U.S. patent application number 12/715214 was filed with the patent office on 2010-06-17 for fault tolerant wheel alignment head and system.
This patent application is currently assigned to Snap-On Incorporated. Invention is credited to Adam C. Brown, Eric Bryan, Steven W. ROGERS.
Application Number | 20100149526 12/715214 |
Document ID | / |
Family ID | 40295037 |
Filed Date | 2010-06-17 |
United States Patent
Application |
20100149526 |
Kind Code |
A1 |
ROGERS; Steven W. ; et
al. |
June 17, 2010 |
FAULT TOLERANT WHEEL ALIGNMENT HEAD AND SYSTEM
Abstract
A sensing head and system utilizes fault tolerant design and
self-diagnosis. Alternative operation modes are provided when one
or more functional modules or components fail. Unique designs
provide redundant system resources. Self-diagnoses and tests are
provided to isolate and identify sources of malfunctions.
Inventors: |
ROGERS; Steven W.; (Conway,
AR) ; Brown; Adam C.; (Maumelle, AR) ; Bryan;
Eric; (Conway, AR) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, N.W.
WASHINGTON
DC
20005-3096
US
|
Assignee: |
Snap-On Incorporated
Kenosha
WI
|
Family ID: |
40295037 |
Appl. No.: |
12/715214 |
Filed: |
March 1, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11829414 |
Jul 27, 2007 |
7684026 |
|
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12715214 |
|
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Current U.S.
Class: |
356/139.09 ;
33/288 |
Current CPC
Class: |
G01B 11/2755 20130101;
G01B 2210/12 20130101; G01B 2210/30 20130101; G01B 2210/14
20130101; G01B 2210/58 20130101; G01B 2210/16 20130101 |
Class at
Publication: |
356/139.09 ;
33/288 |
International
Class: |
G01B 11/26 20060101
G01B011/26 |
Claims
1. A sensing head for use in a wheel alignment system, comprising:
one or more functional modules, each of which is configured to
perform a function usable in obtaining measurements for calculating
wheel alignment parameters of a vehicle, wherein the functional
modules include at least one of: a wireless communication interface
module configured to communicate in a wireless manner with a
computer system or a companion sensing head attached to the
vehicle; a spatial relationship sensing module configured to
measure a spatial relationship between the sensing head and the
companion sensing head; an image sensing module configured to
producing image data representing an image taken of a target
associated with a vehicle wheel; and an illumination module
configured to illuminate the target; a data processor configured to
calculate the measurements based on data received from the one or
more functional modules; wherein the one or more functional modules
provide operation redundancy by utilizing at least one of:
providing multiple sets of illumination devices in the illumination
module, wherein at least one set is independent from another set
and is configured to illuminate the target independently; providing
multiple paths for communication with the computer system using the
wireless communication module, wherein at least one of the paths is
different from another path; providing multiple sets of
illumination devices to the spatial relationship sensing module,
wherein at least one set is independent from another set and is
configured to independently generate a signal to the companion
sensing head; and providing multiple processing units for
implementing the data processor, wherein each processing unit is
configured to independently perform the functions of the data
processor.
2-29. (canceled)
Description
TECHNICAL FIELD
[0001] The present subject matter relates to techniques and
equipment for high reliability wheel alignment that are tolerant to
faults, resistant to harsh operation environment, and capable of
providing effective self-diagnosis.
BACKGROUND
[0002] Wheel alignment systems operate in a harsh environment that
challenges the reliability and operability of the systems.
Significant variations in temperature and humidity, and electrical
noise common in automotive service facilities can disrupt the
operation of the alignment systems and, in the case of cordless
wheel alignment systems, the reliability and availability of
wireless communications between alignment heads and console
computer system. The equipment occasionally is dropped or collides
with vehicles or other equipment. Additionally, many alignment
systems are susceptible to single point failures that can render
the entire system unusable even though only one minor component or
device fails.
[0003] Furthermore, operators of wheel alignment systems often have
limited skills or training in using the equipment. When an
alignment system is not performing as expected, the operator has no
way to know whether it is caused by improper operations,
environment interferences, or actually by system malfunctions. In
these cases, the operator may unnecessarily request the alignment
system be serviced even though it is actually in perfect working
condition. The unnecessary services and unavailability of alignment
systems significantly reduce productivity and increase service and
operation costs. Although some alignment systems provide crude
self-diagnostic information, the information generally relates to a
functional capability but does not identify a specific
component.
[0004] Accordingly, wheel alignment systems that are highly
reliable, tolerant to faults, resistant to harsh operation
environment, and capable of providing effective self-diagnosis are
highly desirable.
SUMMARY
[0005] This disclosure describes embodiments of fault-tolerant,
highly reliable alignment heads and systems that provide
alternative operation mode, such as using redundant system
resources, and avoiding single point failures. Techniques and
designs of effective self-diagnosis and communications with users
related to system faults also are provided. An exemplary sensing
head provides redundant system resources. The sensing head includes
one or more functional modules, each of which is configured to
perform a function usable in obtaining measurements for calculating
wheel alignment parameters of a vehicle. The functional modules
include at least one of a wireless communication interface module
configured to communicate in a wireless manner with a computer
system or a companion sensing head attached to the vehicle, a
spatial relationship sensing module configured to measure a spatial
relationship between the sensing head and the companion sensing
head, an image sensing module configured to producing image data
representing an image taken of a target associated with a vehicle
wheel; and an illumination module configured to illuminate the
target. A data processor is provided to calculate the measurements
based on data received from the one or more functional modules. The
functional modules provide operation redundancy by utilizing at
least one of providing multiple sets of illumination devices in the
illumination module, wherein at least one set is independent from
another set and is configured to illuminate the target
independently; providing multiple paths for communication with the
computer system using the wireless communication module, wherein at
least one of the paths is different from another path; providing
multiple sets of illumination devices to the spatial relationship
sensing module, wherein at least one set is independent from
another set and is configured to independently generate a signal to
the companion sensing head; and providing multiple processing units
for implementing the data processor, wherein each processing unit
is configured to independently perform the functions of the data
processor.
[0006] According to another aspect of this disclosure, an exemplary
sensing head is capable of providing self diagnostic information.
The exemplary sensing head includes one or more functional modules,
each of which is configured to perform a function usable in
obtaining measurements for calculating wheel alignment parameters
of a vehicle, and a data processor, coupled to the one or more
functional modules, configured to process data. At least one of the
functional modules is configured to perform a self test of a
respective functional module. The data processor determines an
operation condition of the respective functional module based on
data related to the self test performed with respect to the
respective functional module. If the data processor determines that
the functional modules are working properly, a user interface
conveys information indicating that the sensing head is in a normal
operation condition.
[0007] According to another aspect of this disclosure, an exemplary
sensing head utilizes a unique communication arrangement to achieve
resource redundancy. The exemplary sensing head is for use in a
wheel alignment system for producing data usable in calculating
alignment parameters. The sensing head includes a housing for
mounting on a wheel of a vehicle to be measured by operation of the
wheel alignment system; and a wireless communication module
configured to selectively establishing a first wireless
communication path and a second wireless communication path between
the sensing head and a remote computer system. A failure in one of
the first wireless communication path and the second wireless
communication path does not affect the operation the other
communication path. The data generated by the sensing head is
transmitted to the computer system via at least one of the first
wireless communication path and the second wireless communication
path.
[0008] According to still another aspect, an exemplary sensing head
includes a unique multi-drop bus system that selectively couples
only one of the one or more functional modules to a data processor
via the bus system and isolates all other functional modules from
the bus system.
[0009] Another aspect of this disclosure allows a sensing head to
detect and provide information related to a drop event. An
exemplary sensing head includes a housing for mounting on a wheel
of a vehicle to be measured by operation of the wheel alignment
system, a drop sensor configured to acquire data related to a drop
of the sensing head, and a data storage device, coupled to the drop
sensor, configured to store the data acquired by the drop sensor. A
data processor may be provided to determine an occurrence of the
drop based on the data acquired by the drop sensor.
[0010] Additional advantages and novel features will be set forth
in part in the description which follows, and in part will become
apparent to those skilled in the art upon examination of the
following and the accompanying drawings or may be learned by
production or operation of the examples. The advantages of the
present teachings may be realized and attained by practice or use
of the methodologies, instrumentalities and combinations
particularly pointed out in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The drawing figures depict one or more implementations in
accord with the present teachings, by way of example only, not by
way of limitation. In the figures, like reference numerals refer to
the same or similar elements.
[0012] FIG. 1 diagrammatically illustrates a first arrangement of
targets and active sensing heads in relation to vehicle wheels.
[0013] FIGS. 1A and 1B illustrate different types of targets that
may be used on passive heads.
[0014] FIG. 2 is a functional block diagram of an exemplary wheel
alignment system, with elements thereof mounted to wheels of a
subject vehicle (although other elements of the vehicle are omitted
for convenience).
[0015] FIG. 3 is a side view of some of the wheel mounted
components of the system, with one of the active sensing heads
shown in a partial cross-sectional detail view.
[0016] FIG. 4 is a side view of one of the active sensing heads
useful in explaining the relationship of the camera axis to the
pitch plane of the measured gravity vector.
[0017] FIG. 5 is a rear view of one of the active sensing heads
useful in explaining the relationship of the camera to the camber
plane of the measured gravity vector.
[0018] FIG. 6 is a functional block diagram of the components of
one of the exemplary active sensing heads.
[0019] FIG. 7 diagrammatically illustrates another arrangement of
targets and active sensing heads in relation to vehicle wheels, in
this case using additional targets and image sensing for
measurement of the spatial relationship between the active
heads.
[0020] FIG. 8 is a side view of some of the wheel mounted
components of the system of FIG. 7, with one of the active sensing
heads shown in a partial cross-sectional detail view, generally
like that of FIG. 3; but wherein the spatial relationship sensor
utilizes another camera.
[0021] FIG. 9 is a functional block diagram of the components of an
exemplary active sensing heads shown in the detail view in FIG.
7.
[0022] FIGS. 10 to 18 diagrammatically illustrate a series of
alternative arrangements, having various heads/targets associated
with different combinations of the vehicle wheels and using various
different configurations or equipment for spatial relationship
sensing.
[0023] FIG. 19 shows a detailed functional block diagram of an
exemplary sensing head.
[0024] FIG. 20 is a simplified block diagram of an exemplary
illumination module.
[0025] FIG. 21 shows the front and side views of an exemplary
spatial relationship sensing module.
[0026] FIG. 22 illustrates transmission of data copies using two
wireless communication paths.
[0027] FIG. 23 is an exemplary circuit diagram of an exemplary SPI
multiplexer.
DETAILED DESCRIPTION
[0028] In the following detailed description, numerous specific
details are set forth by way of examples in order to provide a
thorough understanding of the relevant teachings. However, it
should be apparent to those skilled in the art that the present
teachings may be practiced without such details. In other
instances, well known methods, procedures, components, and
circuitry have been described at a relatively high-level, without
detail, in order to avoid unnecessarily obscuring aspects of the
present teachings.
[0029] Reference now is made in detail to the examples illustrated
in the accompanying drawings and discussed below.
[0030] System Architecture
[0031] FIG. 1 depicts an exemplary alignment system embodying the
teachings and techniques of this disclosure. Except for the wheels,
elements of the vehicle are omitted for ease of illustration.
[0032] The wheel alignment system includes a pair of passive heads
21 and 23 mounted on respective wheels 22 and 24 of the vehicle,
which are front steering wheels in this first example. The active
sensing heads 25 and 27 are adapted for mounting in association
with other respective wheels 26 and 28 of the vehicle, in this case
the rear wheels. Each active sensing head includes an image sensor
29 or 31 for producing image data, which is expected to include an
image of a passive target when the various heads are mounted to the
respective wheels of the vehicle 20. In this first example, the
image sensors 29 and 31 in the active sensing heads 25 and 27 are
two dimensional (2D) imaging devices, e.g. cameras.
[0033] The heads 21 and 23 are passive in that they include targets
but do not include any sensing elements. Each of the passive heads
21 and 23 includes a target of a type that may be observed by one
of the image sensors 29 or 31 in the active heads 25 and 27. A
target on a passive head 21 or 23, for image sensing by a sensor on
another head, may be active or passive. An active target, such as a
light emitting diode (LED), is a source driven by power to emit
energy (e.g. IR or visible light) that may be detected by a sensor.
A passive target is an element that is not driven by power and does
not emit energy for detection by a sensor. Assuming an image sensor
in head 25 or 27, a passive target would be an object that reflects
(or does not reflect) light or other energy in a manner detectable
by the respective image sensor. In the example, although the
targets could comprise one or more light emitting elements, the
targets comprise light and dark regions that can be detected when
illuminated by other sources and imaged by cameras or the like in
the active sensing heads 25 and 27.
[0034] A first example of a target that can be used on either of
the passive wheel heads 21 is illustrated in FIG. 1A. In this first
example, the target is rectangular. A second example of a target
that can be used on either of the passive wheel heads 21 is
illustrated in FIG. 1B. In this second example, the target is
circular. In each case, the target consists of a flat plate with a
pattern of differently sized circles marked on or mounted on the
surface of the plate in a pre-determined format and patter.
Although specific patterns are shown FIGS. 1A and 1B, it will be
evident that a large number of different patterns can be used on
each target. For example, a larger or smaller number of dots may be
included and other sizes and shapes can be used for the dots. As
another example, multifaceted plates or objects can also be used
for the targets. Many examples utilize a number of retro-reflective
elements arranged to form each target. For further information,
attention is directed to U.S. Pat. No. 5,724,743 to Jackson, the
entire disclosure of which is incorporated herein by reference.
[0035] The system also includes a spatial relationship sensor
associated with at least one of the active sensing heads 25 or 27.
The spatial relationship sensor enables measurement of the spatial
relationship between the active sensing heads 25 and 27 when the
active sensing heads are mounted on wheels of the vehicle. In
general, spatial relationship sensors may measure relative position
and/or orientation, depending on the type of sensor used. A
positional measurement refers to the relative position of the
measured item from the perspective or in the coordinate system of
the measuring device. Measurement of position generally uses a
standard coordinate system such as Cartesian coordinates or polar
coordinates. Orientation may be derived from a three-dimensional
position measurement, or orientation may be measured independently
of position. Orientation relates to the rotational position of the
measured device with respect to the measuring device expressed in a
standard coordinate system. Orientation is generally expressed in
rotational angles in three orthogonal reference planes.
[0036] It will be readily apparent to someone skilled in the art
that the wheel alignment systems discussed herein may be
implemented with various different types of spatial relationship
sensors. In this first example, the system uses two conventional
(1D) angle sensors 33 and 35 to measure the relative angles of the
active sensing heads 25 and 27, in the toe plane.
[0037] The active heads 25 and 27 also contain gravity sensors or
the like to measure tilt, typically camber and pitch, of the head.
In this first example, the head 25 includes one or more tilt
sensors 37; and the head 27 includes one or more tilt sensors
39.
[0038] As shown in a more detailed example later (regarding FIG.
2), the system also includes a computer. The computer processes
image data relating to observation of the targets and tilt data,
from the active sensing heads. The computer also processes spatial
relationship data from the at least one spatial relationship
sensor. The data processing enables computation of at least one
measurement of the vehicle.
[0039] Measurement using image processing techniques is
fundamentally different than using conventional angle measurement
technology in a wheel alignment system. Although basic image
processing techniques are known to those skilled in the art, a
brief description is presented for clarity. The image of a body
varies according to the perspective from which such body is viewed
and the variation in the image is directly related to and
determinable from the perspective angle of the view path along
which the body is viewed. Furthermore, it is known that it is
possible to determine the perspective angles at which an object is
viewed merely by relating the perspective image of that object with
a true non-perspective image thereof. Conversely put, it is
possible to determine the angles at which an object is orientated
to a view path (or a plane perpendicular thereto) by comparing a
perspective image of an object with a non-perspective image
thereof.
[0040] In practice, a mathematical representation, or data
corresponding to a true image (i.e. an image taken by viewing the
target perpendicularly to its primary plane) and the dimensions of
the target are preprogrammed into the memory of the computer so
that, during the alignment process, the computer has a reference
image to which the viewed perspective images of the targets can be
compared.
[0041] The way that the computer calculates the orientation of the
target is to identify certain geometric characteristics on the
target, take perspective measurements of these and compare these
measurements with the true image previously preprogrammed into the
memory of the computer.
[0042] Furthermore, as the true dimensions of the target are
preprogrammed into the memory of the computer, the method and
apparatus of this invention can be used to determine the exact
position of the wheels in three-dimensional space. This can be done
by firstly determining the perspective image of certain of the
elements of the pattern on the target (for example, the distances
between circles) and comparing the dimensions of this image to the
true dimensions of those elements. This will yield the distance
that the element and, accordingly, the target is from the image
sensor.
[0043] For the wheel alignment system discussed herein, the image
sensor in the active head views a target attached to a wheel and
produces image data which describes a perspective image of the
target. The computer correlates the perspective image data for the
targets with the true shape of the target. In so doing, the
computer relates the dimensions of certain known geometric elements
of the target with the dimensions of corresponding elements in the
perspective image and by performing certain trigonometric
calculations (or by any other suitable mathematical or numerical
methods), calculates the alignment of the wheel of the vehicle. The
computer can also calculate the three-dimensional position and
orientation of the axis of rotation of the wheel (wheel axis)
associated with the passive target.
[0044] For additional information regarding measurement based on
processing of images of targets, attention again is directed to
U.S. Pat. No. 5,724,743 to Jackson, the entire disclosure of which
is incorporated herein by reference.
[0045] FIG. 2 depicts a more comprehensive example of an exemplary
wheel alignment system 50 as well as four wheels 41, 43, 45 and 47
of a vehicle (otherwise not shown, for simplicity). The system 50
includes four heads 51, 53, 55 and 57 for mounting on or otherwise
in association with the wheels 41, 43, 45 and 47 as shown
stylistically in the drawing. A variety of different types of
mounting devices may be used. In this example, the passive heads 51
and 53 are mounted on the front wheels 41 and 43, and the front
heads 51 and 53 use retro-reflective targets. When mounted on the
wheels as shown, the retro-reflective targets face rearward, so as
to be observable by the image sensors in the respective active
sensing heads. The retro-reflective targets may be similar to those
used in three-dimensional (3D) machine vision alignment systems.
The heads 55 and 57 mounted on the rear wheels 45 and 47 are active
sensing heads, in that they include image sensing elements. In this
example, the heads 55 and 57 further include tilt and spatial
relationship sensing elements, as discussed below, for obtaining
information for processing by a host computer system 100 of the
wheel alignment system 50. The host computer system 100 may be
implemented as part of one of the heads, or implemented with a
computer system, such as a stationary computer or a portable
computer, remote to the heads. According one embodiment of this
disclosure, data obtained by the heads 55 and 57 is transmitted to
the host computer system 100 in a wireless manner using WIFI,
Bluetooth, UWB (Ultra-Wideband), Zigbee, or any other suitable
wireless technology.
[0046] An imaging sensor, such as an alignment camera, is
positioned in each of rear heads. The optical axis of each such
camera faces forward along the track of the vehicle, in order to
measure the position and orientation of the targets attached to the
front wheels. The cameras need not be directly on the track of the
vehicle wheels, that is to say on the roll line of the wheels. The
cameras need only to face alongside the wheel track sufficiently to
view and capture images of the targets on the passive heads 51, 53
associated with the front wheels. In the example, the active
sensing head 55 includes an image sensing module or the like
containing an image sensor in the form of a camera 61 facing
forward along the track of the left wheels. When so mounted, the
field of view of the camera 61 includes the target portion of the
passive head 51 mounted on the left front wheel 41. Similarly, the
active sensing head 57 includes an image sensing module or the like
containing an image sensor in the form of a camera 63 facing
forward along the track of the right wheels. When so mounted, the
field of view of the camera 63 includes the target portion of the
passive head 53 mounted on the right front wheel 43.
[0047] One or more sensors are attached to the rear heads 55, 57
and positioned to measure a spatial relationship between the two
active sensing heads. A variety of available sensing technologies
may be used, and two examples are discussed, later. In the example
illustrated in FIG. 2, the active sensing head 55 includes a sensor
65; and the active sensing head 57 includes a sensor 67. The
sensors 65 and 67 in this application are used for sensing the
relative angular relationship between the active sensing heads 55
and 57, whereas the image signals from the cameras 61 and 64 are
processed to compute regular front wheel alignment parameters, such
as camber and toe.
[0048] Each rear head 55 or 57 also incorporates one or more
inclinometers, which are used as tilt sensors to measure the
relative camber and pitch angles of each rear head to gravity.
These inclinometers, for example, may comprise MEMS type devices
designed to be integral to the track camera printed circuit
board.
[0049] FIG. 3 is a side view of some of the wheel mounted
components of the system. This left side view shows the left front
head 51, with its passive target, attached to the left front wheel
41. The side view also shows the left rear active sensing head 55,
attached to the left rear wheel 45. FIG. 3 also provides an
enlarged detail view, partially in cross section, of elements of
the active sensing head 55.
[0050] As shown, the head 55 comprises a housing 71. Hardware for
mounting the housing to the wheel is omitted for clarity. The
housing 71 contains the forward facing track camera 61. In this
example, the spatial relationship sensor 65 uses a beam angle
detection technology, discussed later with regard to FIG. 6,
although other types of sensors may be used. The housing also
contains a user interface 74 for communicating with the user and a
printed circuit board 75 containing the data processing electronics
for processing the data from the camera(s) and other sensors and
communications with the host computer. For purpose of forming the
sensing head of an exemplary system, the board 75 also supports a
pitch tilt sensor 77 and a camber tilt sensor 79. Although shown
separately, the two tilt sensors 77, 79 may be elements of a single
inclinometer module. The sensors 77, 79 communicate inclination
readings to a processor on the board 75, for transmission with the
camera data to the host computer system 100.
[0051] FIGS. 4 and 5 are somewhat stylized illustrations of the
active sensing head 55, in side and rear views, which illustrate
the relationship of the axes measured by the tilt sensors to the
other elements. It is assumed for discussion here that the tilt
sensors 77-79 are elements of a single MEMS inclinometer. The
inclinometer determines the gravity vector with respect to the
pitch plane (FIG. 4) and the gravity vector with respect to the
camber plane (FIG. 5). Similar measurements, of course, are taken
for the other active sensing head 57 (FIG. 2). In this way, each
head's orientation to gravity can be processed to relate each track
facing camera's optical axis to gravity (FIGS. 4 and 5). In this
way, the relationship of each front target to gravity can also be
measured by processing of the image data and the gravity vector
data.
[0052] FIG. 6 is a functional block diagram of the elements of one
of the active sensing heads, in this case the head 55, although the
elements of the head 57 will be generally similar in this first
example.
[0053] As discussed above, the active sensing head 55 includes an
image sensing module 81 or the like containing an image sensor in
the form of the track camera 61 which in use will face forward
along the track of the left wheels to allow that camera to obtain
images containing the target of the passive head 51 (see also FIG.
2). The track facing image sensor module 81, illustrated in FIG. 6,
includes an LED array 83, serving as an illuminator, to emit light
for desired illumination of the target on the head 51 mounted to
the vehicle wheel 41 on the same side of the vehicle. The camera 61
is a digital camera that senses the image for the wheel alignment
application. In operation, the camera 61 generates a value of each
image pixel based on analog intensity of the sensed light at the
point in the image corresponding to the pixel. The value is
digitized and read out to circuitry on the main printed circuit
board 75. The value may be digitized either on or off of the camera
sensor chip.
[0054] In this implementation, the spatial relationship sensor
module 65 comprises an aperture 86 and a linear image sensor 87
such as a charge-coupled device (CCD) or CMOS unit. An IR LED is
provided to project a beam of light toward a similar toe sensor
module in the opposite head 57. In a similar manner, the opposite
head 57 includes an IR LED that projects a beam of light toward
head 55.
[0055] The IR light/radiation from the IR LED of the opposing head
57 is sensed by the linear image sensor 87, via the aperture 86.
The precise point on the sensor 87 at which the IR light from the
other head is detected indicates the relative angle of incidence of
the light from the opposite head at the sensor 87 in the head 55.
In a similar fashion, the IR light/radiation from the IR LED of the
head 55 is sensed by the linear image sensor, via the aperture in
the opposite head 57; the precise point on the opposite linear
image sensor at which the IR light from the LED is detected
indicates the relative angle of incidence of the light from the
head 55 at the linear sensor in head 57. Processing of the angle
detection data from the two linear sensors enables determination of
the angular relationship between the optical camera axes of the
cameras 61 and 63 in the two active sensing heads.
[0056] The circuit board 75 includes a data processor 89 and an
associated data/program memory 91. The data processor 89 may be
implemented as a single chip or a set of individually packaged
chips. In operation, each camera 61, 63 supplies digital image data
to the data processor 89. As shown, the active sensing head 55 also
includes the camber tilt sensor 79 and the pitch tilt sensor 77.
These inclinometer elements supply the gravity angle measurements
(see discussion of FIGS. 4 and 5) to the processor 89. The
processor 89 performs one or more operations on the data and
supplies the data for transmission to the host computer system
100.
[0057] The image processing operations of the data processor 89 may
involve formatting various data for communication. Alternatively,
the processor 89 may implement some degree of pre-processing before
transmission to the host computer system 100. With regard to the
image data, image pre-processing may include gradient computation,
background subtraction and/or run-length encoding or other data
compression (see e.g. U.S. Pat. No. 6,871,409 by Robb et al.). The
processor 89 may also process the image data to some degree in
response to the tilt data from the tilt sensors 77, 79 and/or the
spatial relationship measurement data. Alternatively, the tilt and
cross position data may simply be forwarded to the host computer
for use in further processing of the image data.
[0058] The processor 89 in one of the active heads may be
configured to receive data from the other head and perform wheel
alignment parameter computations, internally, and then send only
the vehicle measurement results to the host computer system 100.
Moreover, processor 89 in one of the active heads may be configured
to calculate all alignment values and also generate the user
interface. In this case, the active head may act as a web server to
serve web pages that implement the user interface for the wheel
alignment system, and the host computer may consist of any general
purpose computer with a web browser and no wheel alignment specific
software.
[0059] The processor 89 or another controller (not separately
shown) on the board 75 also provides control over operations of the
active sensing head 55. For example, the control element (processor
89 or other controller) will control the timing and intensity of
emissions by the LED array 83 and the IR LED as well as the timing
and possibly other operational parameters of the camera 81 and the
linear image sensor 87. The control element may perform power
management to selectively shut down or reduce power supplies to
different elements or modules of the sensing head, in response to
occurrence of prescribed events or inactivity of sensing heads, to
reduce power consumption and to extend operation time. Details of
the power management of sensing heads will be described shortly.
The active sensing head 55 also includes a user interface 74 for
communicating with a user, and the processor 89 or other controller
will sense and respond to inputs via the user interface 74.
[0060] Two-way data communications are provided between the
components of the active sensing head 55 and the host computer 100
(FIG. 2) and in some configurations between the active heads,
conforming to one or more appropriate data protocol standards, to
enable data communication to and from the host computer 100 at
desired speeds and in a wireless manner. Those skilled in the art
will recognize that other data communications interfaces may be
used in wheel alignment systems, such as WIFI or wireless Ethernet,
Zigbee, Bluetooth, UWB (Ultra-Wideband), IrDA, or any other
suitable narrowband or broadband data communication technology.
[0061] Electronic circuits on board 75 as well as elements of image
sensing module 81 and spatial relationship sensor module 65 receive
power from a supply 94. If heads 55 and 57 are wireless, the power
supply may utilize power storage media, such as rechargeable or
disposable batteries, or super-capacitors. If needed, the system 50
may use cables, to supply power and transmit signals to and from
the heads 55 and 57, in case the wireless transmission is not
working properly or power storage midis run out of power. The wired
supply may run from a conventional AC power grid or receive power
over USB or Ethernet cabling.
[0062] Returning to FIG. 2, host computer system 100 processes data
from the active sensing heads 55, 57 and provides the user
interface for the system 50. In the example, the system 100 may be
implemented by a desktop type personal computer (PC) or other
computer device such as a notebook computer, UMPC (ultra mobile
PC), or similar device. A client server arrangement also could be
used, in which case the server would perform the host processing
and one of the active heads or another user device would act as a
client to provide the user interface. Although those skilled in
advanced wheel alignment technologies will be familiar with the
components, programming and operation of various suitable computer
systems, it may help to provide a brief example.
[0063] Computer system 100 includes a central processing unit (CPU)
101 and associated elements for providing a user interface. The CPU
section 101 includes a bus 102 or other communication mechanism for
communicating information, and a processor 104 coupled with the bus
102 for processing information. Computer system 100 also includes a
main memory 106, such as a random access memory (RAM) or other
dynamic storage device, coupled to bus 102 for storing information
and instructions to be executed by processor 104. Main memory 106
also may be used for storing temporary variables or other
intermediate information during execution of instructions by
processor 104. Computer system 100 further includes a read only
memory (ROM) 108 or other static storage device coupled to bus 102
for storing static information and instructions for processor 104.
A storage device 110, such as a magnetic disk or optical disk, is
provided and coupled to bus 102 for storing information and
instructions. Although only one is shown, many computer systems
include two or more storage devices 110.
[0064] The illustrated embodiment of the computer system 100 also
provides a local user interface, for example, so that the system
appears as a personal computer or workstation as might be used in a
wheel alignment bay or an auto service shop. The computer system
100 may be coupled via bus 102 to a display 112, such as a cathode
ray tube (CRT) or flat panel display, for displaying information to
a computer user. An input device 114, including alphanumeric and
other keys, is coupled to bus 102 for communicating information and
command selections to processor 104. Another type of user input
device is cursor control 116, such as a mouse, a trackball, or
cursor direction keys for communicating direction information and
command selections to processor 104, which the CPU 101 in turn uses
for controlling cursor movement on display 112. The cursor input
device 116 typically has two degrees of freedom in two axes, a
first axis (e.g., x) and a second axis (e.g., y), that allows the
device to specify positions in a plane. The couplings between the
user interface elements 112-116 and the CPU 101 may be wired or may
use optical or radio frequency wireless communication
technologies.
[0065] The CPU 101 also includes one or more input/output
interfaces for communications, shown by way of example as an
interface 118 for two-way data communications with the active
sensing heads 55 and 57. For purpose of the wheel alignment
application, the interface 118 enables the CPU to receive image
data, spatial relationship measurement data and tilt data from the
active sensing heads 55 and 57. Typically, the interface 118 also
allows the host computer system 100 to send operational commands
and possibly software downloads to the active sensing heads 55 and
57.
[0066] Although not shown another communication interface may
provide communication via a network, if desired. Such an additional
interface may be a modem, an Ethernet card or any other appropriate
data communications device. The physical links to and from the
additional communication interface(s) may be optical, wired, or
wireless.
[0067] Although the computer 100 may serve other purposes in the
shop, the alignment system 50 uses the computer system 100 for
processing data from the heads 55, 57 to derive desired alignment
measurements from the data provided by the heads, and to provide
the user interface for the system 50. The computer system 100
typically runs a variety of applications programs and stores data,
enabling one or more interactions via the user interface, provided
through elements such as 112-116 to implement the desired
processing. For wheel alignment applications, the programming will
include appropriate code to process the data received from the
particular implementation of the heads 55, 57, including
computations to derive desired vehicle wheel alignment measurement
parameters from the various data from the heads 55 and 57. The host
computer 100 will typically run a general purpose operating system
and an application or shell specifically adapted to perform the
alignment related data processing and provide the user interface
for input and output of desired information for alignment
measurements and related services. Since it is a general purpose
system, the system 100 may run any one or more of a wide range of
other desirable application programs.
[0068] The components contained in the computer system 100 are
those typically found in general purpose computer systems used as
servers, workstations, personal computers, network terminals, and
the like. In fact, these components are intended to represent a
broad category of such computer components that are well known in
the art.
[0069] At various times, the relevant programming for the wheel
alignment application may reside on one or more of several
different media. For example, some or all of the programming may be
stored on a hard disk or other type of storage device 110 and
loaded into the Main Memory 106 in the CPU 101 for execution by the
processor 104. The programming also may reside on or be transported
by other media for uploading into the system 100, to essentially
install and/or upgrade the programming thereof. Hence, at different
times all or portions of the executable code or data for any or all
of the software elements may reside in physical media or be carried
by electromagnetic media or be transported via a variety of
different media to program the particular system and/or the
electronics of the active sensing heads 55, 57. As used herein,
terms such as computer or machine "readable medium" therefore refer
to any medium that participates in providing instructions to a
processor for execution. Such a medium may take many forms,
including but not limited to, non-volatile media, volatile media,
and transmission media (e.g. wires, fibers or the like) as well as
signals of various types that may carry data or instructions
between systems or between system components.
[0070] Runout compensation for the heads could be performed as with
traditional conventional alignment heads by elevating the rear
wheels and using the camber sensors to measure the runout vector
then elevating the front wheels and using cameras to image the
targets as they rotate about the front wheel's axis. An alternate
method would be to avoid elevating the wheels by rolling the
vehicle along the lift and performing the runout measurements on
the heads with the inclinometers as the track cameras image the
front targets as well as fixed targets on the lift, vehicle or
other stationary object in order to establish the fixed coordinate
system.
[0071] As noted, the rear heads 55, 57 incorporate inclinometer
type tilt sensors to measure the relative camber and pitch angles
of each rear head to gravity. Once runout is taken and the
inclinometer angle values are measured, each head's orientation to
gravity could be processed to relate each track facing camera's
optical axis to gravity. Using the relationship of the track facing
camera to gravity and the measured relationship of the front target
to the track facing camera, the relationship of the front target to
gravity can be calculated. A spatial relationship is measured by
the sensors 65 and 67, to determine the spatial relationship
between the track cameras 61 and 63.
[0072] Front toe, caster, and SAI would be measured using
techniques similar to those embodied in an imaging aligner, such as
the Visualiner 3D or "V3D" aligner, available from John Bean
Company, Conway, Ark., a division of Snap-on Incorporated. The rear
thrust angle, each rear individual toe, and the horizontal angular
relationship of the track cameras to each other, would be derived
from the measurements obtained by the rear spatial relationship
sensors. The inclinometers would relate each track camera to each
other through the common gravity vector references. With the track
cameras effectively related to each other along the axis of the
rear thrust line, each front target's location and orientation can
be determined in a coordinate system that is directly related to
the thrust angle and to gravity.
[0073] Calibration may be performed by mounting each rear head on a
straight calibration bar in much the same way that the current
conventional heads are calibrated. The bar is first rotated to
compensate for runout. The zero offset of the rear spatial
relationship sensors can then be set and by leveling the
calibration bar, each camber sensor zero offset can be set. The
pitch zero offset is set by leveling the head with a precision
level bubble and recording the pitch inclinometer value. Enhanced
camera calibration may be achieved by adding another calibration
bar adapted to mount the front targets in view of the track cameras
(see e.g. U.S. Patent Application Publication No. 2004/0244463 by
James Dale, Jr.). After the initial calibration above is performed,
the track cameras measure the orientation of the front targets as
the targets and bar are rotated about the axis of the front
calibration bar. The relationship of one camera to the other may be
calculated and thus the relationship of each camera to the rear
spatial relationship checked or calibrated. By leveling the front
target calibration bar, the fixed relationship of each track camera
to the local inclinometers may also be checked. This redundant
check could possibly constitute an ISO check for customers that
require measurement accuracy traceability.
[0074] In addition, small targets may be affixed to each front
turntable allowing for an additional measurement or cross check of
turn angle.
[0075] It will be readily apparent to someone skilled in the art
that the wheel alignment systems discussed herein may be
implemented with various different types of spatial relationship
sensors. An image sensor is one type of spatial relationship
sensor. An image sensor may consist of a camera with a two
dimensional array of sensing elements that produces data
representative of an image expected to contain a target within the
field of view of the sensor. The data from the image sensor can be
processed to determine position and orientation information related
to the viewed target and thus the head, wheel or other object with
which the target is associated. An example of a prior art image
sensor is the camera used in the Visualiner 3D commercially
available from John Bean Company, Conway, Ark., a division of
Snap-on Incorporated. An angle sensor is another type of applicable
spatial relationship sensor. An angle sensor produces data
representing the angle from the sensor relative to a point. Various
types of angle sensors are generally known. One example of an angle
sensor is the linear CCD sensor as used in the Visualiner available
from John Bean Company.
[0076] Hence, it may be helpful now to consider an example in which
the aperture and linear image sensor style spatial relationship
sensing arrangement described above relative to FIGS. 3 and 6 is
replaced by an imaging type camera similar to the track camera.
FIGS. 7 to 9 are views/diagrams similar to those of FIGS. 1, 3 and
6, except that the illustrations of this second implementation show
such an alternate technology using a target and image sensor for
the spatial relationship sensing function. Wheels and elements
similar to those of the implementation of FIGS. 1, 3 and 6 are
similarly numbered and are constructed and operate in essentially
the same fashion as discussed above. This example uses passive
two-dimensional targets 51 and 53 on the front wheels 41 and 43;
and it uses active heads 55' and 57' on the rear wheels for the
measurements alongside the vehicle tracks, much as in the example
of FIG. 1. The rear active sensing heads use cameras 61, 63 or
similar 2D image sensors to obtain images of the targets on the
front heads 51, 53 and determine the relative positions and
orientations of the targets with respect to the active heads, as
discussed in detail above relative to FIG. 2. However, the spatial
relationship of the two active heads 55', 57' is determined by at
least one 2D image sensor 97, which obtains images of a 2D target
67' mounted on the opposite active head. In this example, the
active head 57' has an associated target 67' similar to one of the
targets on head 51 and 53, but the head 57' does not include a
sensor for the spatial relationship measurement function. The
active sensing head 55' uses an image processing type approach to
the spatial relationship measurement across the rear of the vehicle
based on imaging the target 67'. The image sensor 97 typically
would be similar to the cameras or the like used as 2D image
sensors in the example of FIG. 2.
[0077] As shown in more detail in FIGS. 8 and 9, the spatial
relationship sensor 95 uses an image sensing module similar to the
track facing image sensor module 81. The spatial relationship image
sensing module 95 includes a digital camera 97 and an LED array 99.
The LED array 99 serves as an illuminator. For the spatial
relationship sensing application, the LED array 99 produces
infrared (IR) illumination. The other rear head 57' includes an IR
sensitive retro-reflective target 67' (FIG. 7) to be illuminated by
the LED array 99, which in turn is sensed by the camera 97.
[0078] The spatial relationship camera 97 images the target 67'
positioned on the companion head (across the rear of the vehicle)
in place of the other spatial relationship sensor. Both cameras 61
and 97 could share a common processing board in the one head while
the other head may simply use a single camera (for track) and a
target (for cross). Processing of the target image obtained by
camera 97 can compute the angular spatial relationship between the
rear heads, in much the same way as the images from the active head
cameras were processed to determine relative angle and/or position
of the wheel mounted targets in the examples of FIGS. 1 and 2.
Rather than measuring a spatial relationship angle as in the
previous example, the image sensing module and associated image
processing measures the 3D spatial relationship of the target on
the opposite active head. For additional information regarding
measurement based on processing of images of targets, attention
again is directed to U.S. Pat. No. 5,724,743 to Jackson.
[0079] In the system of FIGS. 7 to 9, at least one active head
contains gravity sensors to measure camber and pitch of the head.
Since the imaging of the target mounted on the opposite active head
allows the system to obtain a three-dimensional (3D) spatial
relationship measurement between the two active heads, only one
active head is required to have gravity sensors. Otherwise, the
structure, operation and computations are generally similar to
those of the earlier examples.
[0080] In the examples discussed above, the active heads have been
associated with the rear wheels, and the targets have been
associated with the front wheels of the vehicle. However, those
skilled in the art will understand that there are many variations
of the basic configurations discussed above. Also, there are a
variety of different combinations of imaging sensors with other
sensors for determining the spatial relationship that may be used.
Several are described and shown below.
[0081] FIG. 10, for example, shows an arrangement similar to that
of FIG. 1 in which the active heads and the target heads are
reversed. The wheel alignment system of FIG. 10 includes a pair of
passive heads 221 and 223 mounted on respective wheels 222 and 224
of the vehicle 220, which are rear wheels in this example. The
active sensing heads 225 and 227 are adapted for mounting in
association with the respective front wheels 226 and 228 of the
vehicle 220. Again, each active sensing head includes an image
sensor 229 or 231 for producing image data, which is expected to
include an image of a passive target when the various heads are
mounted to the respective wheels of the vehicle. In this example,
the image sensors 229 and 231 in the active sensing heads 225 and
227 are two dimensional (2D) imaging devices, e.g. cameras similar
to the track cameras in the earlier examples.
[0082] The heads 221 and 223 are passive in that they include
targets of a type that may be observed by one of the image sensors
in the active heads 225 and 227, but they do not include any
sensing elements. Typically, the targets comprise light and dark
regions that can be detected when illuminated by other sources and
imaged by cameras or the like in the active sensing heads 225 and
227.
[0083] As in the earlier examples, the system also includes a
spatial relationship sensor associated with at least one of the
active sensing heads 225 or 227. The spatial relationship sensor
enables measurement of the spatial relationship between the active
sensing heads 225 and 227 when the active sensing heads are mounted
on wheels of the vehicle. In this example, the system uses two
conventional (1D) angle sensors 333 and 335 to measure the relative
angles of the active sensing heads 225 and 227, in the toe plane.
The active heads 225 and 227 also contain gravity sensors or the
like to measure tilt, typically camber and pitch, of the head.
Hence, the head 225 includes one or more tilt sensors 337; and the
head 227 includes one or more tilt sensor 339.
[0084] As shown in the earlier examples (e.g. FIG. 2), the system
also includes a computer. The computer processes image data
relating to observation of the targets and tilt data, from the
active sensing heads. The computer also processes spatial
relationship data from the at least one spatial relationship
sensor. The data processing enables computation of at least one
measurement of the vehicle.
[0085] As noted, this example is essentially a front-to-rear
reversal of the target/active sensing head positions from that of
the example of FIG. 1. Although not all variants are shown, those
skilled in the art will understand that similar types of
front-to-rear variants and/or left-to-right variants can also be
implemented for every other alternative arrangement discussed
herein.
[0086] FIG. 11 illustrates another alternative arrangement. In this
example, two active sensing heads are mounted on one side of the
vehicle, and two passive sensors are mounted on the opposite side
of the vehicle. As shown, the mounting of the targets on the
passive heads provides an extension out away from the wheels,
somewhat, so as to allow the image sensors in the active heads to
see and image the targets. Each active head contains an image
sensor that obtains images of a target attached to the
corresponding wheel on the opposite side of the vehicle. As in the
earlier examples, each active head contains gravity sensors to
measure camber and pitch of the head. Here, the spatial
relationships of the two active heads are determined by two
conventional angle sensors measuring the toe plane angles between
the two heads. Since the structure, operation and computations are
generally similar to those of the earlier examples, those skilled
in the art should understand the example of FIG. 11 without a more
detailed discussion here.
[0087] FIG. 12 illustrates another alternative arrangement. In this
example, two active sensors are mounted on one side of the vehicle,
and two passive sensors are mounted on the other side of the
vehicle. Each active head contains image sensors that obtain images
of targets attached to the corresponding wheel on the opposite side
of the vehicle. Here, the spatial relationships of the two active
heads are determined by one or more image sensors that obtain
images of a target mounted on the opposite active head. In the
example, the front active head includes a target, and the rear
active head includes a 2D imaging sensor for obtaining images of
that target, in a manner analogous to the 3D spatial relationship
measurement in the example of FIGS. 7 to 9. At least one active
head contains gravity sensors to measure camber and pitch of the
head. Since this system obtains a 3D position and orientation
measurement between the two active heads, only one active heads is
required to have gravity sensors. Again, since the structure,
operation and computations are generally similar to those of
earlier examples, those skilled in the art should understand the
example of FIG. 12 without a more detailed discussion here.
[0088] FIG. 13 is yet another alternative arrangement. This example
uses a first active sensing head containing a single 2D image
sensor for obtaining images of a passive target on a first passive
head mounted on the other wheel on the same side of the vehicle.
The first passive head is mounted to a wheel on the same side of
the vehicle as the first active head. In the specific example shown
in the drawing, the first active head is mounted on the left rear
wheel, and the first passive head is mounted on the left front
wheel. One target on the first passive head is available for
imaging by the 2D image sensor associated with the left rear wheel,
that is to say, along the vehicle track on that side of the
vehicle.
[0089] However, the first passive head also contains a second
passive target in a known relative position with respect to its
first passive target. The second passive target is extended in
front of the wheel so that it can be viewed by a corresponding 2D
image sensor on the opposite side of the vehicle, for imaging in a
spatial relationship measurement. Hence, the second active head is
mounted across from the first passive head, that is to say on the
right front wheel in the illustrated arrangement. The second active
head contains two 2D image sensors. One of these sensors obtains
images of the target mounted on the first passive head, attached to
the opposite (left front) wheel for the spatial relationship
measurement. The other 2D image sensor in the second active head
obtains images of the target mounted on a second passive head,
which is mounted on the same side of the vehicle, that is to say,
on the right rear wheel in this example. The second passive head
contains a single target, and that head is mounted across from the
first active head.
[0090] In the arrangement of FIG. 13, at least one of the active
heads contains gravity sensors to measure camber and pitch of the
head. Since the system obtains a 3D position and orientation
measurement between the two active heads, only one active heads is
required to have gravity sensors. In general, the details of
implementation and operation of the system of FIG. 13 should be
apparent from this summary discussion and the earlier detailed
disclosure of the examples of FIGS. 1-9.
[0091] The example illustrated in FIG. 14 is generally, similar to
the example of FIG. 13, except that in the system of FIG. 14, the
first active head also contains a second image sensor. The second
image sensor in that head obtains an image of a second target
attached to the second passive head. This configuration has an
advantage over the arrangement of FIG. 13 in that it only requires
two unique head hardware configurations rather that four. Both
active heads are the same, and both passive heads are the same.
Each of the active heads would be similar to the head 55' shown in
FIGS. 8 and 9. One active head should be identified as a front head
and the other as a rear head. This can generally be done with
firmware in the embedded processors.
[0092] A second advantage of this configuration (FIG. 14) is that
the second spatial relationship measurement is redundant
information that is not required to calculate wheel alignment. This
redundant information can be used as a calibration check on the
system. If both active heads contains gravity sensors, both camber
and toe can be validated. If only one active head contains gravity
sensors, only the toe calibration can be validated.
[0093] In the example shown in FIG. 15, the system uses passive
heads with targets that are mounted on each of the front wheels,
essentially as in the examples of FIGS. 1-9. Active heads, shown on
the rear wheels, contain 2D image sensors. A reference bar with a
target on each end is placed such that each active head can view
one of the targets on the reference bar as well as the target on
the front wheel of the same side of the vehicle. The relative
positions and orientations of the two targets on the reference bar
are known. The system can find the spatial relationship of the two
active heads from the measured 3D positions and orientations of the
two reference targets by the active heads and the known
relationship of the two reference targets. This provides the
spatial relationship information obtained by the spatial
relationship sensor--target of the example of FIGS. 7 to 9. Since
the reference targets are fixed in position they can also be used
as a reference for measurements during rolling runout. Those
skilled in the art should appreciate the detailed structure and
operations of this example, from the drawing, this description and
the earlier discussion of other similar examples.
[0094] The example illustrated in FIG. 16 generally works just like
the example of FIG. 15, except there is only a single reference
target. The viewing angle of the image sensors in the active heads
must be wide enough to be able to view both the passive head target
on the same side of the vehicle and the single reference
target.
[0095] FIG. 17 illustrates yet another example of an exemplary
wheel alignment system. Here, the system uses passive heads with
attached targets mounted on each front wheel. The active heads are
mounted on the rear wheels, as in several of the earlier examples.
Each active head contains a 2D image sensor to obtain images of the
passive head target on the respective side of the vehicle.
[0096] The image sensors are extended forward from the center of
the rear wheels so that the sensors are located forward of the rear
wheel tires, so as to provide a cross-vehicle line of sight under
the vehicle. One of the image sensors, in the example the sensor on
the active head mounted on the left rear wheel, contains a partial
mirror that passes images from the passive target or reflects
images from a target mounted on the corresponding active head on
the other side of the vehicle. The operations of the mirror are
shown in more detail in FIG. 19.
[0097] Light from the passive target on the passive head mounted on
the same side of the vehicle, that is to say, on the left front
wheel in the illustrated arrangement, passes directly through the
half-silvered mirror to the 2D image sensor on the active sensing
head mounted on the left rear wheel. Light from the passive target
on the opposite active head, that is to say on the active head
mounted on the right rear wheel in the illustrated arrangement,
arrives at an angle to the partially reflective side of the mirror
and is reflected into the 2D image sensor on the active sensing
head mounted on the left rear wheel. The advantage of this system
is that it eliminates one image sensor by allowing one of the
sensors to view two different targets.
[0098] For further details of exemplary arrangements and
combinations of alignment cameras and targets, attention is
directed to a co-pending patent application Ser. No. 11/487,964
(attorney docket No. 66396-275), titled "VEHICLE WHEEL ALIGNMENT
SYSTEM AND METHODOLOGY," commonly assigned to the assignee of this
application, the disclosure of which is incorporated herein by
reference in its entirety.
[0099] FIG. 19 is a detailed functional block diagram showing an
exemplary sensing head implemented with highly reliable, fault
tolerant features. For purpose of explanation, detailed operations
are discussed based on the structure of the sensing head 55 shown
in FIGS. 2 and 6. However, it will be readily apparent to someone
skilled in the art that the power management discussed herein may
be implemented with various different types of sensing heads or
alignment systems including those disclosed herein as well as other
variations, such as image or non-image based wheel alignment
systems using sensors or heads remote or attached to the wheels of
a vehicle to measure various angles of the wheels and
suspension.
[0100] The exemplary sensing head 55 includes a circuit board 75
and a user interface 74 for communicating with a user. The user
interface 74 includes input and/or output devices such as keypad,
control buttons, switches, display, touch screen input, voice
recognition, LEDs, speakers, etc. As previously discussed relative
to FIG. 6, the printed circuit board 75 includes a data processor
89, a memory device 91 and a power supply 94. The circuit board 75
couples to one or more peripheral devices 510, 511. Each peripheral
device includes one or more functional modules for performing
respective designated functions useful in obtaining data usable in
calculations of alignment measurements. The functions may include
wireless communications, detection of spatial relationships
relative to other sensing heads, illuminations, image capturing,
detection of spatial characteristics of wheels or alignment heads,
user interface, self-diagnosis, self testing, power supply, power
management, signal processing, etc.
[0101] For instance, the peripheral device 510 includes a camera
module 61 implemented with image sensors, such as a charge-coupled
device (CCD) or CMOS unit; an LED array module 83, serving as an
illuminator, to emit light for desired illumination of the target
mounted to the vehicle wheel on the same side of the vehicle; and a
wireless communication module 552 comport to Bluetooth standard to
perform wireless communications with host computer system 100. The
peripheral device 511 includes a spatial relationship sensor module
65 using a beam angle detection technology, discussed previously
with regard to FIG. 6, to detect relative spatial relationships
between the active sensing heads 55 and 57; a tilt sensor module
579 implemented with a MEMS type inclinometer for measuring camber
and sensing device pitch; a potentiometer module 577 implemented
with a rotary potentiometer to encode the angle of the shaft of the
sensing device 55 relative to the wheel/wheel clamp assembly; and
an IR transceiver module 554 for forming a communication path for
sending and receiving measurements data to sensing head 57, as
discussed with regard to FIG. 2.
[0102] While the functional modules illustrated in FIG. 19 are
described based on the sensing head shown in FIGS. 2 and 6, it is
known to people skilled in the art that the selection and
combination of functional modules and peripheral devices are not
limited to those shown in FIGS. 9 and 19. Rather, various types or
different combinations of peripheral devices and/or functional
modules may be used to implement different types of sensing heads
with different functions.
[0103] In one embodiment, one or more functional modules or
components of the sensing head or alignment system implement
self-testing and/or self-diagnosis functions. Operation status and
health condition of each of the functional modules or components
are determined and communicated to the data processor 89 for
determining an overall health of the sensing head or the alignment
system. Generally, any detected problems will be reported the host
computer system 100 and communicated to the user on a display of
the system host and/or the user interface 74 on the sensing head
55, such as via a simple LED indicators or a small graphics or
alphanumeric display panel. The communication using the user
interface 74 on the sensing head 55 is useful in the event that all
communications between the sensing head 55 and the host computer
system 100 fail.
[0104] According to another embodiment, an individual failed module
or component can be switched off if a fault in the module or
component is detected. This prevents a failed device or module from
negatively affecting the performance of other modules or
components. Features associated with the failed module or component
may not be available, but the remainder of the sensing head or
system will continue to operate with its capability reduced by only
the features of the failed component or module. In another
embodiment, an exemplary sensing head and/or alignment system is
implemented with redundant system resources and/or alternative
operation modes such that the alignment or system is capable of
continued operation despite an occurrence of a single point
failure. For instance, multiple sets of a selected device, such as
illumination LEDs, may be provided. Each set of LEDs can work
independently for illumination of targets even if another set or
sets of illumination LEDs are not operating, existent, or
performing properly. Details of designs, techniques, control and
operations related to testing, self diagnosis, redundant resources
will be described shortly.
[0105] (1) The Data Processor
[0106] The data processor 89 includes a supervisor processor 560
and a DSP controller 561. The supervisor processor 560 handles
system management tasks, such as power management, fault
determination, data communications, system integrity and user
interface, and coordinates operations of the functional modules and
various components of the sensing head 55. The supervisor processor
560 utilizes Host Port Interface (HPI) to communicate with the DSP
controller 561. Each module couples to the supervisor processor 560
using a Serial Peripheral Interface (SPI), via a SPI multiplexer.
The SPI multiplexer is a programmable logic device (CPLD) designed
to ensure the isolation of each SPI interface from other SPI
interfaces and the supervisor processor 560. In this way, no one
faulty module can cause signal contention and failure of the shared
SPI interface to the supervisor processor 560. The supervisor
processor 560 may be implemented using an ARM 9 microcontroller,
available from Atmel Corporation of San Jose, Calif.
[0107] The DSP controller 561 executes firmware independent of the
supervisor processor 560, and is in charge of processing image data
received from the camera module 61 and deriving the target plane
orientation. In one embodiment, the DSP controller 561 also
determines image integrity when the self-test feature is invoked to
have the image sensor generate a test image (details related to
test images will be described below relative to the camera module
61). The DSP controller 561 may be implemented using a
video/imaging processor TMS320DM642 from Texas Instruments
Incorporated.
[0108] In another embodiment, the DSP controller 561 is configured
to work as a backup master processor which takes over many tasks
performed by the supervisor data processor 560 should the
supervisor data processor 560 fail. The tasks may include wireless
communications, interactions with the user interface 74, etc. For
instance, the DSP controller 561 can take control of the sensing
head 55 and send all failure data to the user by communications
with the host computer system 100, the companion sensing head 57
and/or the user interface 46.
[0109] The DSP controller 561 learns an operation condition of the
supervisor data processor 560 via one or more signal lines. For
instance, the supervisor data processor 560 may send a heartbeat
signal to the DSP controller 561 when the supervisor data processor
560 is working properly. If the supervisor data processor 560
fails, the heartbeat signal is gone and based on the absence of an
effective heartbeat signal from the supervisor data processor 560,
the DSP controller 561 determines that the supervisor data
processor 560 has failed, and predetermined steps for taking over
part or all of the tasks that previously performed by the
supervisor data processor 560 are performed by the DSP controller
561. In another embodiment, the supervisor data processor 560
constantly drives a specific signal line to a specific state, such
as pull high, when the supervisor data processor 560 is working
properly. If the state of the specific signal line is not pulled
high, the DSP controller 561 determines that the supervisor data
processor 560 is not working properly and will take over the tasks
previously performed by the supervisor data processor 560.
[0110] (2) The Camera Module
[0111] The camera module 61 may be implemented with an Omnivision
OV9121 image sensor with 1280.times.1024 pixel image resolution,
available from Omnivision of Sunnyvale, Calif. The image sensor
setup, exposure time, gain settings and image acquisition is
controlled by an image controller (not shown), such as a Freescale
MC9S08 microcontroller available from Freescale Semiconductor, Inc.
of Austin, Tex. The image controller communicates with the
supervisor processor 560 via the SPI communications bus. The
supervisor processor 560 may command the camera module to take both
a background frame (no illumination) followed immediately by an
illuminated frame or simply one or the other types of frames. The
image data obtained by the image sensor are coupled to a video port
of the DSP controller 561, where images are acquired at
predetermined rates, such as 24 or 48 MegaPixels/sec.
[0112] In one embodiment, the image controller also monitors
various functions of the image sensor, temperature, image frame
pixel count and power supply voltages to ensure proper operation of
the camera module 61. Any failures or variances from nominal will
be reported by the image controller to the supervisor processor 560
via the SPI interface. In another embodiment, the image sensor can
be commanded by the image controller to generate an overlay test
pattern.
[0113] The image controller may command the image sensor to
generate an overlay test pattern, such as a color bar test pattern,
associated with one or more captured images. The DSP controller 561
evaluates the functional integrity of image sensors in the camera
module 61 based on image data including the test pattern. If an
analysis of image data received from the image sensor reveals a
normal test pattern and no defective target images (such as a dark
image), the DSP controller 561 determines that the image sensor is
working properly because the test pattern is generated and sensed
as intended. In this case, the sensing head 55 has sufficient
confidence and certainty that the dark image is caused by reasons
other than malfunctions of the image sensor of the camera module.
The actual cause may be insufficient light, non-existence or
misplacement of alignment target, etc. On the other hand, if both
the test pattern and an effective target image are unavailable, the
DSP controller 561 determines that the image sensor in the camera
module 61 failed. An appropriate error signal identifying the
faulty image sensor may be generated and sent to the supervisor
processor 561 and/or the user interface 74 for communicating to the
user.
[0114] (3) The LED Array Module
[0115] The LED array module 83 performs image illumination
(strobe). FIG. 20 shows an exemplary circuit diagram of the LED
array module 83. The LED array module 83 is controlled by an
illumination controller 831, which may be implemented with a
Freescale MC9S08 microcontroller, available also from Freescale
Semiconductor, Inc. The illumination controller 831 communicates
with the supervisor processor 560 via the SPI bus to setup and
control image illumination. A strobe signal from the camera module
61 is utilized by the LED array module 83 to synchronize image
illumination with the image sensor exposure duration.
[0116] The LED array module 83 includes two sets of high
efficiency, high output infrared LEDs: LED bank A and LED bank B.
Each set of the LEDs is driven by a separate current source. It is
understood that more sets and/or visible types of LEDs may be used
depending on design preference.
[0117] In normal operation, only one set of LEDs is required to
properly illuminate targets and allow the camera module 61 to
obtain target images. Each set of LEDs can be used alternately
thereby increasing the lifetime of each set of LEDs. Failure of an
LED, a set of LEDs, or a power supply will only affect one of the
sets. The other set of LEDs will continue to operate. The failure
will not render the LED array module 83 entirely unusable.
[0118] In one embodiment, the illumination controller 831 monitors
various parameters and operations of the illumination module 83,
such as temperature, power supply voltages and LED current to
ensure proper operation. The voltages (V1, V2 and V3) across the
LED banks are constantly monitored by the illumination controller
831 for determining currents flowing through the LED sets. The
values of currents indicate whether the LED sets are working
properly, whether one or more LED's are shorted, or whether there
is an open circuit in of the LED banks. Any malfunction or
deviation from a preset range or level is reported to the
supervisor processor 560 by the illumination controller 831 via the
SPI bus.
[0119] (4) The Wireless Communication Module
[0120] The wireless communication module 552 comports to one or
more wireless communication standards, such as the Bluetooth
standard, and performs wireless communication with the host
computer system 100. An antenna, such as a Centurion D-Puck high
gain antenna, is provided to transmit and receive wireless signals.
A communication controller (not shown), such as a MC9208
microcontroller from Freescale, bridges the standard Bluetooth HCI
UART interface of the communication module 552 with the SPI bus. In
one embodiment, the communication module 552 is programmed to enter
the Bluetooth defined Hold, Sniff or Park modes to conserve power
during times of low usage. In another embodiment, the communication
controller monitors various functions and/or parameters of the
communication module 552, such as radio interface communications
and power supply voltages to ensure proper operation. Any
malfunctions and/or failures or variances from nominal are reported
to the supervisor processor 560.
[0121] (5) The Spatial Relationship Sensor Module
[0122] As discussed earlier relative to FIGS. 2, 6 and 18, the
spatial relationship sensor module 65 accurately measures the
horizontal angular relationship (cross toe) between sensing devices
55, 57. An image sensor, such as a linear CCD sensor with a 3648
pixel linear CCD, is disposed behind a slit or mask. A sensor
controller (not shown), which may be implemented with a low power
ARM 7 microcontroller, available from Atmel Corporation, is
provided to perform complex CCD timing and data acquisition. In one
embodiment, in response to any activities of the spatial
relationship sensor module 65 during a sleep mode, the sensor
controller may send out an interrupt signal to interrupt and wake
the supervisor processor 560, while the SPI interface is not
active, by toggling the SPI bus slave out data line (MISO).
[0123] The sensor controller performs self tests and monitors
various functions such as LED current and power supply voltages to
ensure proper operation of the spatial relationship sensor module
65. In one embodiment, a unique test illumination device is
provided for performing a self test of the spatial relationship
sensor module 65. As described earlier related to FIGS. 6 and 19,
the sensor module 65 includes the linear image sensor 87, which may
be implemented using a 3648 pixel linear CCD, and an aperture 86 on
a mask, for detecting a beam of light projected by a similar sensor
module in the opposite head 57. An IR light from the opposing head
57 is sensed by the linear image sensor 87, via the aperture 86.
The precise point on the sensor 87 at which the IR light from the
other head is detected indicates the relative angle of incidence of
the light from the opposite head at the sensor 87 in the head
55.
[0124] FIG. 21 illustrate front and side views of an exemplary
spatial relationship sensing module 65 implemented with a test
illumination device. As shown in the front view in FIG. 21, the
spatial relationship sensing module 65 includes CCD 87, LED1 and
LED 3, and a test LED 2. LED 1 and LED 3 are disposed outside a
mask 651 for projecting IR lights to a companion sensing head. In
normal operation, only one of the two LED light sources is needed.
Each is optimized to operation on a particular side of the vehicle.
In the event that one of LED 1 and LED 3 fails, the other LED can
use used in it place.
[0125] Test LED 2 and CCD 87 are disposed within the mask 651. The
test LED 2 is designed to illuminate the entire CCD 87 on the same
sensing head. The sensor controller of the spatial relationship
sensor module may issue a command to control illumination of the
test LED 2, for the purpose of performing a self test to determine
whether the CCD 87 is in normal working condition. For instance, in
the event that the spatial relationship sensing module 65 cannot
obtain proper signals from the companion sensing head 57, the
sensor controller may command the test LED 2 to illuminate the CCD
87. If image signals are properly generated by the CCD 87 in
response to the illumination of the test LED 2, the sensor
controller may determine that the CCD 87 is working properly. The
lack of proper signals may be caused by a problem on the companion
sensing head 57, an incorrect installation of the sensing heads,
etc., but not from the CCD sensor 87. Furthermore, in response to
the illumination of the test LED 2, pixels that deviate
significantly from nominal or predetermined ranges or levels are
flagged as weak or ineffective pixels. Data obtained from the
flagged pixels are compensated for or thrown out during angle
calculations. Factory and field calibration factors may be stored
in the sensor controller internal flash memory and include
checksums for data integrity. Any failures or variances from
nominal will be reported by the sensor controller to the supervisor
processor 560 via the SPI interface.
[0126] (7) The IR Transceiver Module
[0127] The IR transceiver module 554 is configured to establish a
wireless communications link with the IR transceiver module of the
other sensing head 57. The wireless communications link is based on
the standard RS-232 protocol with each bit encoded into IR light
burst modulated on a 500 KHz carrier frequency. The IR
communications link can autonomously receive and transmit data even
while the sensing head is in a sleep mode. It is understood that
other types of wireless communications technology may be utilized
to implement the wireless communications link between two sensing
heads. The sensing head 55 utilizes the IR communications link to
synchronize the sensor controller real time clock of the spatial
relationship modules in the sensing heads 55, 57. In this way, the
sensing head can perform alignment data acquisition cycles in a
known relationship to the companion sensing head. In another
embodiment, a sensing head may send a command via the IR
communications link requesting the spatial relationship sensor on
the companion sensing head begin a toe sensor data acquisition
cycle based on a specific time or immediately upon an external
trigger.
[0128] In still another embodiment, the wireless communication link
between the companion sensing heads provides an alternative data
transmission path to the host computer system 100, in addition to
the wireless communication module 552.
[0129] As shown in FIG. 22, two communication paths between the
sensing head 55 and the host computer system 100 are provided: a
first communication path between the sensing head 55 to the host
computer system 100 via the sensing head's wireless communication
module, and a second communication path from the IR transceiver
module 554 to the companion head 57 and then to the host computer
system 100. The sensing head 55 sends the companion sensing head
57, via the IR transceiver module 554, a duplicate copy (copy 2) of
data that the sensing head 55 generates and sends to the host
computer system 100 via the companion sensing head's wireless
communication module (copy 1). At the companion sensing head 57,
the duplicate copy of data (copy 2) is relayed to the host computer
system 100. Alternatively, the duplicate copy of data (copy 2) is
combined with data sensed and generated by the companion sensing
head 57, and the combined data is sent to the host computer system
100 via the wireless communication module of the companion sensing
head 57. Similarly, the companion head 57 may transmit data to the
sensing head 55 for being relayed to the host computer system 100.
In a similar fashion, the host computer system sends commands
and/or information to each sensing head via two communication
paths: a first path via the wireless communication module of a
sensing head, and a second path via the wireless communication
module of a companion sensing head, for being relayed to the
sensing head. In this way, two copies of data obtained by each
sensing head and commands sent by the host computer system 100 are
transmitted via different communication paths. This architecture
improves communication reliability should any wireless
communication modules of the companion sensing heads become
intermittent or fail. In one embodiment, both transmission paths
are used to transmit data from sensing heads 55, 57 to the host
computer system 100 and commands from the host computer to the
sensing heads 55, 57. In another embodiment, the transmission path
alternative to using the wireless communication module 552 is a
backup to the wireless communication module 552, and is utilized
only when the wireless communication module 552 fails.
[0130] (8) The Tilt Sensor Module
[0131] The tilt sensor module 579 may be implemented using a
two-plane, MEMS type inclinometer, capable of measuring both camber
and sensing head pitch. Tilt controllers (not shown), such as a set
of two Texas Instruments MPS430 ultra low power microcontrollers,
each with an integrated temperature sensor and integrated SPI bus
interface, are provided to process and communicate the angle data
from the inclinometer to the supervisor processor 560 via the SPI
interface.
[0132] The MEMS inclinometer is configured to perform a self test
which deflects the internal micro-machined silicon beam by a
constant amount. Evaluating this deflection by measuring the angle
output change can determine if the inclinometer is defective or out
of calibrations. Any failures or variances from nominal will be
reported to the supervisor processor 560, to indicate an error in
the respective module.
[0133] In one embodiment, an output from the inclinometer detecting
a sensing head pitch is used to awake the sensing head to exit from
the sleep mode and enter into a normal operation mode. The
inclinometer pitch output is constantly monitored by the
corresponding tilt controller. If a predetermined level of change
occurs, signaling vibrations or activity around the vehicle or the
sending head, the tilt controller toggles the SPI bus slave out
data line (MISO) while the SPI interface is not active to interrupt
and wake the supervisor processor 560 from the sleep mode.
[0134] According to another embodiment, during low or no activity
(angle changes), the supervisor processor 560 successively reduces
the frequency of data acquisition cycles that are used to retrieve
data from the tilt sensor module and/or other functional modules.
Between cycles, the supervisor processor 560 and other functional
modules may enter into a sleep mode with most of the power supplies
shut down for long periods of time. The inclinometer can detect
very slight movements of the sensing head 55 indicating potential
activity around the vehicle. Upon detecting this movement, the tilt
controller signals the supervisor processor 560 to resume data
acquisition cycles.
[0135] (9) The Potentiometer Module
[0136] A rotary potentiometer 577 encodes the angle of the shaft of
sensing head 55 relative to the wheel/wheel clamp assembly. A
potentiometer controller (not shown), which may be implemented
using a Texas Instruments MPS430 microcontroller, converts the
position detected by the potentiometer into shaft angle and
communicates the angle data to the supervisor processor 560 via the
SPI bus.
[0137] In one embodiment, factory and field calibration factors are
calculated and stored in the tilt controllers and the potentiometer
controller. Each controller monitors various functions and/or
parameters including temperature and power supply voltages.
[0138] (10) The Bus and Interface System
[0139] As illustrated in FIG. 19, an exemplary sensing head of this
disclosure utilizes a bus system complying with the SPI (Serial
Peripheral Interface) standard, for performing communications
between functional modules and the processor 89. A unique SPI
multiplexer, which may be implemented using a programmable logic
device, such as a CPLD (Complex Programmable Logic Device) or FPGA
(Field Programmable Gate Array), is provided for coupling to the
functional modules via slave SPI bus and to the processor 89 via a
master SPI bus.
[0140] FIG. 23 shows a block diagram of an exemplary SPI
multiplexer. The SPI multiplexer provides seven slave ports (Port 0
through Port 7) for coupling to functional modules, and two master
ports (primary master port and secondary master port), for
optionally support multiple master controllers, such as the
supervisor processor 560 and the DSP controller 561. A set of port
select signals are used to select one and only one module slave SPI
bus to be connected to the master SPI bus. These port select
signals are driven by the master controller prior to initiating a
standard SPI data transfer so as to connect the specific module
intended for data communications.
[0141] The SPI multiplexer may also be programmed to support more
than one master controller. For instance, a signal Master1/Master 2
selects one of the supervisor processor 560 and the DSP controller
561 as the SPI master controller. In this way, a secondary
controller, such as the DSP controller 561, can assume control of
the sensing head 55 in the event that the supervisor processor 560
fails. Each master port has a system clock line (M1_SCK, M2_SCK), a
data transmission indication line (M1_MOSI (master out slave in)
and M2_MOSI) indicating that data is transmitting from a master
port to a selected slave port, a data receiving indication line
(M1_MISO (master in slave out) and M2_MISO) indicating data is
transmitting from a slave port to a master port, and a set of
address lines (M1_PSO-M1_PS3 and M2_PSO-M2PS3) selecting one of the
functional modules coupled to the slave ports. Each slave port has
a system clock line (S1_SCK-S7_SCK), a data receiving indication
line (S1_MOSI-S7_MOSI) indicating that data is transmitting from a
master port to a selected slave port, a data transmission
indication line (S1_MISO_S7_MISO) indicating data is transmitting
from a slave port to a master port, and a slave selection line
(S1_SS-S7_SS), a state of which indicates whether a specific slave
port is selected and active for data communications.
[0142] As described earlier, power supplied to the functional
modules may be partially or completely shut down when not in use or
during a sleep mode, based on a control signal issued by the
supervisor processor 560. In a conventional design where multiple
modules are directly connected to the SPI bus without the SPI
multiplexer, any un-powered module may load the bus, which possibly
results in higher current requirements to drive the bus signals,
loss of bus signal integrity, or even total bus failure. In
addition, in a conventional multi-drop configuration, the identity
of a faulty module can be ambiguous to the processor 89. In the
architecture shown in FIG. 23, the functional modules are isolated
from each other and the bus system by the SPI multiplexer, and the
modules may be shut-down as required without affecting the loading
or integrity of the SPI bus. In addition, the master controller may
sequentially address each module during power on self test to
ensure that each module is functioning properly. If a module
failure is discovered, the master controller can identify the
failed module such as based on an address associated with the
failed module.
[0143] Furthermore, as described earlier, the SPI bus system and
the SPI multiplexer are also programmed to allow an unselected
functional module to request connection to the master SPI bus by
driving a specific signal line, such as the MISO signal. By
altering the state of the MISO signal while a functional module is
not selected, the functional module causes the SPI multiplexer to
provide an interrupt request signal to the master controller. The
master controller may service this interrupt request by querying
the SPI multiplexer for the specific module address requesting
connection, and then select that module for connections and data
communications. While slave ports in the example shown in FIG. 23
utilize MISO signal lines to indicate a service request, it is
understood that a separate, dedicated signal line may be used to
signal the service request.
[0144] While the above discussions utilize SPI standard as an
example to explain operations of the unique combination of a bus
system and multiplexer, it is understood that other types of
multi-drop bus standards, such as Access Bus, EIA-422, EIA-485,
I.sup.2C, IE Bus, LIN Bus, MI Bus, Microwire Bus, MOST, MPI Bus,
SMbus, can also be used without deviating from the teachings of
this disclosure. By implementing isolated selectable ports for each
module versus direct connection, the overall system wide
communication reliability is substantially improved.
[0145] (10) The Power Supply and Charge Subsystem
[0146] As illustrated in FIG. 19, sensing head 55 includes a power
supply and charge subsystem that provides power to the sensing head
55. The power supply and charge subsystem includes the power supply
94, a charger 515, a charging connector 516, a gas gauge 514 and a
battery 517.
[0147] The battery 517 includes one or more power storage units,
such as rechargeable batteries, disposable batteries, chemical
batteries, fuel cells, capacitive power storage devices such as
super capacitors, etc., or any combinations thereof. In one
embodiment, the battery 517 includes one or more Lithium-Ion or
Li-Pol battery packs.
[0148] If rechargeable batteries are provided, the batteries can be
charged by connecting the charging connector 516 to an external
power source such as an AC or DC source. The charger 515 controls
and regulates the charging current and voltage suitable for
charging the battery 517. The power supply 94 is provided to
convert the power supplied by the battery 517 and/or an external
power source to a level suitable for the sensing head 55.
[0149] The gas gauge 514 monitors, measures and calculates multiple
battery parameters and operation status, and provides various types
of information related to the battery and/or charging condition,
including current, available capacity, time-to-empty, time-to-full,
state-of-charge, cell temperature, voltage, charging status,
discharge and charge currents, low voltage thresholds, etc., and
compensates for self-discharge, aging, temperature, and discharge
rate. The gas gauge 514 may track the number of battery
charge/discharge full cycles for predicting the remaining life of
the battery 517. The information related to the battery 514 and
charging conditions may be communicated to the user via the user
interface 74. The gas gauge may be implemented with a bqJUNIOR
series chips available from Texas Instruments, Inc.
[0150] In one embodiment, in addition to using an external power
source, such as the shop AC power, to charge the battery 517, the
charger 515 includes a backup power source for charging the battery
517 when the external power source is unavailable to the sensing
head caused by power failure or disconnection of power line. The
backup power source may be any types of power storage devices, such
as rechargeable batteries, disposable batteries, chemical
batteries, fuel cells, capacitive power storage devices like super
capacitors or boost capacitors, etc., or any combinations thereof.
The backup power storage device has a capacity sufficient to fully
recharge a completely depleted battery 517.
[0151] When the shop AC power is available, the battery 517 may be
recharged by the shop AC power or by the backup power storage
device. When shop AC power is not connected or not available, the
battery 517 is recharged by the backup power storage device only.
This design enables the battery 517 to be recharged even when the
shop AC power is completely turned off. The backup power storage
device may be recharged during a regular recharge process when the
shop AC power connects to the charging connector 516.
Alternatively, the backup power storage device may be recharged
separately, such as by adding fuel to fuel cells, or be replaced by
another fully charged power storage device.
[0152] In another embodiment, an alignment system includes a
docking device for detachably receiving the sensing heads and
recharging the received sensing heads. When the sensing head is
docked in the docking device, the battery 517 is recharged by an AC
or DC power source connected to the docking device, and/or by a
backup power storage device disposed in the docking device. This
design does not require the backup power storage device to be part
of the sensing heads, thereby reduces the overall weight of the
sensing heads.
[0153] In another embodiment, the sensing head 55 includes an
optional shock detection circuit utilizing a digital smart MEMs
device that detects a free fall. A shock controller, which may be
implemented by a Texas Instruments MPS430 microcontroller, acquires
acceleration data from the smart MEMS device and records the time
duration of the drop, to determine if a drop actually occurs and
obtain and record information related to the drop, such as the time
of fall and/or peak acceleration from the impact, for evaluation of
damages and troubleshooting.
[0154] In addition to the exemplary self tests described earlier,
each functional module monitors various functions and/or parameters
including temperature, currents, and power supply voltages, etc.
Factory and field calibration factors may be stored in the modules.
A controller in each module determines an operation status of the
module based on the data and the stored calibration factors. If it
is determined that the functional module is not performing
normally, an indication signal is sent to the supervisor processor
560 to indicate the fault.
[0155] As each functional module has the capability of performing
self tests and diagnoses to isolate and identify a fault or an
error, an exemplary alignment system implemented using the
teachings of this disclosure provides highly useable information
for diagnosis when the system does not operate as intended. In one
embodiment, an audio and/or visual indicator, such as a single LED
or LCD screen, disposed on the sensing head 55 is activated when
the self diagnoses performed by the alignment system indicates that
one or more functional modules or components are not working
properly. In this case, the operator, based on the notification,
knows for sure that the malfunction is not caused by inappropriate
use or operation procedures, but from one or faulty components or
modules of the alignment system, and a service request may be
initiated. On the other hand, if the self tests and diagnoses
performed by the functional modules reveal that the functional
modules are working properly, a user interface, such as a visual or
audio indicator or a signal port, provides output information
indicating that the alignment head is in a normal working
condition. With this information, if the operator encounters
problems during an alignment process, the operator will have
sufficient confidence that the problem is not caused by a
malfunction of the alignment head, but may come from an improper
operation or installation.
[0156] The self-diagnostic information may be stored in a
non-volatile memory of the alignment system, for assisting repair
and diagnosis of the system. In one embodiment, the self-diagnostic
information is transmitted to a remote service center via a data
transmission network coupled to the host computer 100, along with
information of the specific alignment system, such as model number,
serial number, etc., such that replacement parts and components may
be ordered in advance, even before the faulty alignment system
arrives to the service center. Remote diagnosis, repair and
software update may be performed with remote access to the
self-diagnostic information.
[0157] While the foregoing has described what are considered to be
the best mode and/or other examples, it is understood that various
modifications may be made therein and that the subject matter
disclosed herein may be implemented in various forms and examples,
and that the teachings may be applied in numerous applications,
only some of which have been described herein. It is intended by
the following claims to claim any and all applications,
modifications and variations that fall within the true scope of the
present teachings.
* * * * *