U.S. patent application number 12/093334 was filed with the patent office on 2009-09-03 for loader.
This patent application is currently assigned to VOLVO CONSTRUCTION EQUIPMENT AB. Invention is credited to Gilles Florean, David Lazzaro.
Application Number | 20090222176 12/093334 |
Document ID | / |
Family ID | 36613400 |
Filed Date | 2009-09-03 |
United States Patent
Application |
20090222176 |
Kind Code |
A1 |
Florean; Gilles ; et
al. |
September 3, 2009 |
LOADER
Abstract
A loader including a vehicle including a structural frame and an
elongate boom arm is provided. The boom arm is pivotally mounted at
its first end to the frame and has at its second end an assembly
for receiving a tool. The loader includes actuators to actuate the
boom arm and its associated assembly. The loader also includes a
control unit provided with user operable controls for controlling
position and orientation of the boom arm and its associated
assembly. The actuators integrally incorporate therein magnetic
sensors operable to sense longitudinal extension of the actuators
and thereby generate actuator feedback signals indicative of the
longitudinal extension. The control unit processes the actuator
feedback signals in a feedback control to render the position and
orientation of the boom arm and its associated assembly adjustable
using the user operable controls. Sensing a rotation rate of
vehicle engine providing power to the actuators is employed to
modify the feedback control to improve operating stability of the
loader.
Inventors: |
Florean; Gilles; (Belley,
FR) ; Lazzaro; David; (Belley, FR) |
Correspondence
Address: |
WRB-IP LLP
1217 KING STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
VOLVO CONSTRUCTION EQUIPMENT
AB
Eskilstuna
SE
|
Family ID: |
36613400 |
Appl. No.: |
12/093334 |
Filed: |
November 10, 2005 |
PCT Filed: |
November 10, 2005 |
PCT NO: |
PCT/EP2005/013381 |
371 Date: |
August 12, 2008 |
Current U.S.
Class: |
701/50 |
Current CPC
Class: |
F15B 2211/7051 20130101;
F15B 15/2861 20130101; F15B 2211/20523 20130101; F15B 2211/633
20130101; E02F 9/24 20130101; F15B 2211/6336 20130101; E02F 3/432
20130101 |
Class at
Publication: |
701/50 |
International
Class: |
E02F 3/43 20060101
E02F003/43 |
Claims
1. A loader comprising a vehicle including a structural frame and
at least one elongate boom arm, the at least one elongate boom arm
being pivotally mounted substantially at its first end to the
structural frame and having at its second end an assembly for
receiving in operation one or more tools, the loader further
including actuators operable to actuate the at least one boom arm
and its associated assembly, and also including a control unit
provided with user operable controls for controlling in operation
position and orientation of the at least one boom arm and its
associated assembly, wherein the actuators integrally incorporate
therein magnetic actuator sensors operable to sense longitudinal
extension of the actuators and thereby generate actuator feedback
signals indicative of the longitudinal extension, wherein the
control unit is operable to process the actuator feedback signals
in a feedback control to render the position and orientation of the
at least one boom arm and its associated assembly adjustable using
the user operable controls.
2. A loader as claimed in claim 1, wherein the magnetic actuator
sensors integrally included within the actuators are each operable
to sense relative positions of a piston and its associated
co-operating cylinder of its corresponding actuator.
3. A loader as claimed in claim 1, wherein the actuators include a
first actuator operable to actuate the at least one boom arm to
vary its pivotal angle relative to the structural frame, and a
second actuator operable to actuate the assembly to vary its
pivotal angle relative to substantially the second end of the at
least one boom arm.
4. A loader as claimed in claim 1, wherein the control unit is
operable to apply a mathematic translation to the actuator feedback
signals to generate translated signals indicative of an inclination
angle of the one or more tools and a height of the one or more
tools, the translated signals being compared in the control unit
with signals from the user operable controls to provide in
operation the feedback control.
5. A loader as claimed in claim 1, wherein the feedback signals are
operable to provide substantially a first order dynamic measure of
angular orientations of the at least one boom arm and its
associated assembly and one or more tools.
6. A loader as claimed in claim 1, wherein the control unit is
operable to enable the user: (a) to record one or more sets of
preferred angular orientations of at least one boom arm and its
associated assembly corresponding to preferred positions and
orientations of the one or more tools, and (b) to invoke the one or
more sets of orientations for operating the one or more tools for
moving them to one or more of the preferred positions.
7. A loader as claimed in claim 1, wherein the vehicle includes an
inertial sensing unit for sensing at least one of inclination,
acceleration, deceleration and vibration of the vehicle and thereby
generating an inertial signal, the sensing unit being in
communication with the control unit for receiving the inertial
signal such that the control unit is operable to modify at least
one of angular orientation and height of the one or more tools in
response to the inertial signal for retaining a load borne in
operation by the one or more tools more securely.
8. A loader as claimed in claim 1, wherein the vehicle comprises an
engine operable to provide actuation power for the actuators, the
engine including an engine rotation rate sensor adapted to generate
a rotation rate signal indicative of a rotation rate of the engine
in operation, wherein the control unit is arranged to receive the
rotation rate signal for adapting the feedback control in response
to the rotation rate signal.
9. A control system including a control unit adapted to control
operation of a loader, the loader comprising a vehicle including a
structural frame and at least one elongate boom arm, the at least
one elongate boom arm being pivotally mounted substantially at its
first end to the structural frame and having at its second end an
assembly for receiving in operation one or more tools, the system
further including actuators operable to actuate the at least one
boom arm and its associated assembly, and also including the
control unit provided with user operable controls for controlling
in operation position and orientation of the at least one boom arm
and its associated assembly, wherein the actuators integrally
incorporate therein magnetic actuator sensors operable to sense
longitudinal extension of the actuators and thereby generate
actuator feedback signals indicative of the longitudinal extension,
wherein the control unit is operable to process the actuator
feedback signals in a feedback control to render the position and
orientation of the at least one boom arm and its associated
assembly adjustable using the user operable controls.
10. A control system as claimed in claim 9, wherein the magnetic
actuator sensors are each operable to sense relative positions of a
piston and its associated co-operating cylinder of its
corresponding actuator.
11. A method of controlling operation of a loader, the loader
comprising a vehicle including a structural frame and at least one
elongate boom arm, the at least one elongate boom arm being
pivotally mounted substantially at its first end to the structural
frame and having at its second end an assembly for receiving in
operation one or more tools, the loader further including actuators
operable to actuate the at least one boom arm and its associated
assembly, and also including the control unit provided with user
operable controls for controlling in operation position and
orientation of the at least one boom arm and its associated
assembly, wherein magnetic actuator sensors operable to sense
longitudinal extension of the actuators are integrally
incorporating in the actuators, the method comprising steps of: (a)
generating actuator feedback signals indicative of the longitudinal
extension; (b) processing the actuator feedback signals in the
control unit to implement a feedback control to render the position
and orientation of the at least one boom arm (40) and its
associated assembly adjustable using the user operable
controls.
12. A method as claimed in claim 11, wherein the magnetic actuator
sensors are each operable to sense relative positions of a piston
and its associated co-operating cylinder of its corresponding
actuator.
13. A method as claimed in claim 11, wherein step (b) further
comprises steps of: (c) applying a mathematical translation to the
actuator feedback signals to generate translated signals indicative
of an inclination angle of the one or more tools and a height of
the one or more tools; and (d) comparing the translated signals in
the control unit with signals from the user operable controls to
provide in operation the feedback control.
14. A method as claimed in claim 11, wherein the feedback signals
are operable to provide substantially a first order dynamic measure
of angular orientations of the at least one boom arm and its
associated assembly and one or more tools.
15. A method as claimed in claim 11, wherein the method includes
further steps of: (e) measuring using a rotation rate sensor a
rotation rate of an engine of the vehicle and generating a
corresponding rotation rate signal; and (f) adapting the feedback
control in response to the rotation rate signal to enhance
stability of the feedback control.
16. Software on a data carrier executable on computing hardware of
a control unit of a loader for implementing the method as claimed
in claim 11.
Description
BACKGROUND AND SUMMARY
[0001] The present invention relates to loaders operable to execute
digging tasks or to transport and handle loads, wherein such
loaders are mobile and each includes a device such as a bucket or
attachment mounted onto a boom arm. Moreover, the present invention
relates to arrangements for controlling such loaders. Furthermore,
the invention also concerns methods of controlling such loaders and
their boom arms. Additionally, the invention relates to software
executable on computing hardware for implementing the methods in
the aforesaid loaders.
[0002] Loaders are known. They are often each implemented as a
four-wheeled vehicle with two substantially parallel boom arms
pivotally mounted at their proximate ends towards a front region of
the vehicle. A counterweight is often included at a rear region of
the vehicle. Each boom arm is coupled at its distal end to a
pivoting arrangement to which a device such as a bucket is coupled.
Optionally, the bucket is demountable and the loader is configured
to be able to accept other types of tools or attachments, in
operation, such a loader is controlled by an operator or driver
seated in a cabin of the vehicle. The operator or driver is
provided in the cabin with controls for raising and lowering the
boom arms as well as adjusting angle of the pivoting arrangement to
which the bucket is coupled. Thereby, the driver is able to, for
example, scoop a load, for example cement or building bricks, into
the bucket and adjust an inclination of the bucket to retain its
load, lift the bucket upwardly, and then drive the vehicle to
another location for delivering the load held in the bucket.
Alternatively, the driver can employ the bucket for digging
operations, for example digging trenches and holes.
[0003] In view of a magnitude of physical forces required for such
loaders to function, it is contemporary practice to employ
hydraulic actuators, for example hydraulic cylinder actuators, for
raising and lowering the boom arms, and also for adjusting an
inclination angle of the pivoting arrangement associated with the
bucket or attachment. Pressurized hydraulic oil for operating the
hydraulic actuators is provided from a hydraulic pump coupled to an
engine of the vehicle. Moreover, flow of pressurized hydraulic oil
to and from the hydraulic actuators is regulated via hydraulic
valves coupled appropriately to the aforesaid controls included in
the cabin. As will be elucidated later, it has become contemporary
practice to include sensors operable to sense orientation of the
boom arms as well as orientation of the pivoting arrangement
coupled to the bucket or attachment; signals provided by such
sensors are coupled to a feedback arrangement employing signals
from the controls in the cabin as reference signals.
[0004] Known loaders of a type described in overview in the
foregoing will now be further elucidated. In a granted U.S. Pat.
No. 4,844,685, there is described a loader including an electronic
bucket positioning and control system. The loader employs a
hydraulically-controlled boom arm assembly and bucket. The boom arm
assembly includes a pair of boom arm lift hydraulic actuators, and
a pair of bucket lift hydraulic actuators. Each hydraulic actuator
includes a cylinder housing together with a piston rod movable in
respect of its cylinder. Moreover, each piston includes therein a
position sensor implemented as a linear potentiometer comprising a
resistance strip for providing an electrical signal indicative in
operation of a degree to which the piston rod is extended or
retracted in respect of its corresponding cylinder.
[0005] In a published U.S. Pat. No. 4,923,362, there is described a
boom arm and bucket system for a loader. The system includes a
bucket leveling valve operable to maintain a desired orientation of
the bucket as the boom arm is raised and lowered. The system
employs first rotary angular sensors mounted at proximate ends of
the boom arms whereat they are pivotally mounted to a vehicle body
of the loader. Moreover, the system further employs second rotary
angular sensors to sense an inclination of the bucket relative to
the boom arm. The rotary angular sensors are conveniently
implemented as potentiometers. Signals from the first and second
angular sensors are coupled to an electronic feedback unit, for
example implemented using computing hardware operable to execute
software instructions, which compares the signals with reference
signals generated from operator controls included within a cabin of
the loader. In the system, the inclination angle of the bucket is
directly and simply derivable from the signals generated from the
first and second rotary angular sensors.
[0006] Of importance with regard to loaders described in the
foregoing is ease of use and reliability. In view of a degree of
power which operators of such loaders are able to control to
execute various digging or lifting operation, it is vitally
important that actuator sensors and their associated control
systems are robust, for example to wear and debris generated in
operation. A failure or inaccuracy in an actuator sensor
implemented as a potentiometer can cause such a loader to function
potentially erratically with a risk of damage to property or
personnel.
[0007] Thus, two problems which are encountered with contemporary
loaders concern robustness in use as well as dynamic handling
characteristics. The first problem concerns robustness of the
rotary angular sensors which can be conventionally addressed by
employing a better quality of sensor. The second problem relates to
reducing a risk of loads being manipulated by loaders
unintentionally falling with associated potential problems of
personal injury as well as damage to property; this second problem
is conventionally addressed, for example as described in a European
patent application EP 0 597 657, by controlling a rate at which
hydraulic oil is applied or extracted from hydraulic actuators
employed to actuate loader boom arms and associated buckets.
[0008] For aforementioned loaders, although loader operating
performance has been enhanced, there is still a need for further
improvements in loader performance, for example operating safety
when manipulating and transporting loads, to satisfy exacting
requirements demanded by contemporary users and operators of such
loaders; such operating performance is a technical problem
pertinent to the present invention which the present invention
seeks to at least partially solve.
[0009] It is desirable to provide a loader with improved operating
performance and operating robustness.
[0010] According to a first aspect of the present invention, there
is provided a loader comprising a vehicle including a structural
frame and at least one elongate boom arm, said at least one
elongate boom arm being pivotally mounted substantially at its
first end to the structural frame and having at its second end an
assembly for receiving in operation one or more tools, said loader
further including actuators operable to actuate said at least one
boom arm and its associated assembly, and also including a control
unit provided with user operable controls for controlling in
operation position and orientation of the at least one boom arm and
its associated assembly, characterized in that said actuators
integrally incorporate therein magnetic actuator sensors operable
to sense longitudinal extension of said actuators and thereby
generate actuator feedback signals indicative of said longitudinal
extension, wherein said control unit is operable to process said
actuator feedback signals in a feedback control to render said
position and orientation of said at least one boom arm and its
associated assembly adjustable using said user operable
controls.
[0011] The invention is of advantage in that the magnetic actuator
sensors integrally incorporated within the actuators are capable of
imparting improved operating performance and safety of operation to
the loader.
[0012] Optionally, in the loader, the magnetic actuator sensors
integrally incorporated within the actuators are each operable to
sense relative positions of a piston and its associated cooperating
cylinder of its corresponding actuator. Such a manner of including
the actuator sensors is susceptible to increasing robustness of the
actuator sensors and improving their sensing accuracy. Moreover,
such magnetic sensors are found in practice to be highly robust and
reliable and provide signals suitable for implementing the
aforementioned feedback.
[0013] Optionally, in the loader, the actuators include a first
actuator operable to actuate said at least one boom arm to vary its
pivotal angle relative to the structural frame, and a second
actuator operable to actuate said assembly to vary its pivotal
angle relative to substantially the second end of said at least one
boom arm. Such allocation of the first and second actuators is
effective at providing a degree of isolation between local feedback
loops controlling the boom arm and the assembly, thereby
simplifying control and improving stability.
[0014] Optionally, the vehicle comprises an engine operable to
provide actuation power for said actuators, said engine including
an engine rotation rate sensor adapted to generate a rotation rate
signal indicative of a rotation rate of said engine in operation,
wherein said control unit is arranged to receive said rotation rate
signal for adapting said feedback control in response to said
rotation rate signal. Inclusion of the rotation rate sensor is
capable of enabling the control unit to provide more stable
feedback control in response to variations in engine rotation rate
and hence available actuation power.
[0015] Optionally, in the loader, the control unit is operable to
apply a mathematic translation to the actuator feedback signals to
generate translated signals indicative of an inclination angle of
the one or more tools and a height of the one or more tools, said
translated signals being compared in the control unit with signals
from the user operable controls to provide in operation said
feedback control. Isolation of the control for inclination of the
one or more tools relative to the control for height of the one or
more tools is susceptible to rendering the loader easier to control
and hence potentially safer in operation.
[0016] Optionally, in the loader, the feedback signals are operable
to provide substantially a first order dynamic measure of angular
orientations of the at least one boom arm and its associated
assembly and one or more tools. Such first order dynamic response
enables potentially more feedback to be applied to the loader and
its assembly, irrespective of changes in their dynamic
characteristics in response to varying loads being applied thereto
in operation.
[0017] Optionally in the loader, the control unit is operable to
enable the user: (a) to record one or more sets of preferred
angular orientations of at least one boom arm and its associated
assembly corresponding to preferred positions and orientations of
the one or more tools, and (b) to invoke the one or more sets of
orientations for operating said one or more tools for moving them
to one or more of the preferred positions. Providing the one or
more sets of preferred angular orientations and preferred position
is susceptible to rendering the loader faster and easier for the
user to operate, thereby potentially increasing efficiency of
operation of the loader, for example when implementing repeated
digging operations.
[0018] Optionally, in the loader, the vehicle includes an inertia!
sensing unit for sensing at least one of inclination, acceleration,
deceleration and vibration of said vehicle and thereby generating
an inertial signal, said sensing unit being in communication with
said control unit for receiving said inertial signal such that said
control unit is operable to modify at least one of angular
orientation and height of said one or more tools in response to
said inertial signal for retaining a load borne in operation by
said one or more tools more securely. Inclusion of the inertial
sensing unit is capable of increasing operating safety of the
loader, thereby more safely retaining and handling loads borne in
operation by the loader, for example over uneven or inclined
terrain.
[0019] According to a second aspect of the present invention, there
is provided a control system including a control unit control unit
adapted to control operation of a loader, said loader comprising a
vehicle including a structural frame and at least one elongate boom
arm, said at least one elongate boom arm being pivotally mounted
substantially at its first end to the structural frame and having
at its second end an assembly for receiving in operation one or
more tools, said system further including actuators operable to
actuate said at least one boom arm and its associated assembly, and
also including the control unit provided with user operable
controls for controlling in operation position and orientation of
the at least one boom arm and its associated assembly,
characterized in that said actuators integrally incorporate therein
magnetic actuator sensors operable to sense longitudinal extension
of said actuators and thereby generate actuator feedback signals
indicative of said longitudinal extension, wherein said control
unit is operable to process said actuator feedback signals in a
feedback control to render said position and orientation of said at
least one boom arm and its associated assembly adjustable using
said user operable controls.
[0020] Optionally, in the control system, the magnetic actuator
sensors are each operable to sense relative positions of a piston
and its associated co-operating cylinder of its corresponding
actuator.
[0021] According to a third aspect of the present invention, there,
is provided a method of controlling operation of a loader, said
loader comprising a vehicle including a structural frame and at
least one elongate boom arm, said at least one elongate boom arm
being pivotally mounted substantially at its first end to the
structural frame and having at its second end an assembly for
receiving in operation one or more tools, said loader further
including actuators operable to actuate said at least one boom arm
and its associated assembly, and also including the control unit
provided with user operable controls for controlling in operation
position and orientation of the at least one boom arm and its
associated assembly, wherein magnetic actuator sensors operable to
sense longitudinal extension of said actuators are integrally
incorporated into said actuators, said method comprising steps
of:
[0022] (a) generating actuator feedback signals indicative of said
longitudinal extension;
[0023] (b) processing said actuator feedback signals in said
control unit to implement a feedback control to render said
position and orientation of said at least one boom arm and its
associated assembly adjustable using said user operable
controls.
[0024] Optionally, when implementing the method, the magnetic
actuator sensors are each operable to sense relative positions of a
piston and its associated co-operating cylinder of its
corresponding actuator.
[0025] Optionally, in the method, step (b) further comprises steps
of:
[0026] (c) applying a mathematical translation to the actuator
feedback signals to generate translated signals indicative of an
inclination angle of the one or more tools and a height of the one
or more tools; and
[0027] (d) comparing said translated signals in the control unit
with signals from the user operable controls to provide in
operation said feedback control.
[0028] Optionally, in the method, said actuator feedback signals
are operable to provide substantially a first order dynamic measure
of angular orientations of the at least one boom arm and its
associated assembly and one or more tools.
[0029] Optionally, the method includes further steps of:
[0030] (e) measuring using a rotation rate sensor a rotation rate
of an engine of said vehicle and generating a corresponding
rotation rate signal; and
[0031] (f) adapting said feedback control in response to said
rotation rate signal to enhance stability of said feedback
control.
[0032] According to a fourth aspect of the invention, there is
provided software on a data carrier executable on computing
hardware of a control unit of a loader for implementing the method
according to the third aspect of the invention.
[0033] It will be appreciated that features of the invention are
susceptible to being combined in any combination without departing
from the scope of the invention as defined herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] By way of example only, embodiments of the present invention
will now be described with reference to the accompanying drawings
wherein:
[0035] FIG. 1 is a schematic illustration of an embodiment of a
loader pursuant to the present invention, the loader including an
actuated boom arm pivotally mounted at its proximate end to a
vehicle body of the loader and pivotally coupled at its distal end
to an assembly dismountably couplable to, for example, a bucket or
other similar type of tool; the schematic illustration further
depicts a feedback control arrangement operable to control the boom
arm and its associated assembly and bucket;
[0036] FIG. 2 is a schematic geometrical representation of the boom
arm and the assembly of the loader illustrated in FIG. 1;
[0037] FIG. 3 is a schematic illustration of the loader depicted in
FIG. 1 in operation when manipulating a load retained within a load
retaining tool of the loader;
[0038] FIG. 4 is a cross-sectional illustration of a hydraulic
actuator employed within the loader depicted in FIGS. 1 and 3 for
actuating the boom arm of the loader or the assembly and its
associated bucket of the loader; and
[0039] FIG. 5 is an optional modification to the loader illustrated
in FIG. 1, wherein an inertial sensor unit, for example a
configuration of accelerometers and inclination sensors, is
included within a vehicle of the loader; dynamic measurement
signals from the inertial sensor unit are beneficially employed to
adapt control of the boom arm and the assembly for the bucket so as
to increase retention of a load within the bucket, for example
under braking situations or when the vehicle is negotiating uneven
or unstable terrain.
DETAILED DESCRIPTION
[0040] Referring to FIG. 1, there is shown an embodiment of the
present invention, namely a loader indicated generally by 10. The
loader 10 includes a vehicle denoted by 20, the vehicle 20 being
provided with four wheels, an engine 25 providing in operation
motive power to one or more of the wheels, a control cabin for
accommodating an operator or driver of the vehicle 20, one or more
hydraulic pumps coupled to the engine 25 and optionally a
counterbalance weight; the vehicle 20 is also illustrated in FIG.
3. Moreover, the loader 10 comprises a boom arm and bucket
arrangement which will be elucidated in further detail with
reference to FIG. 1.
[0041] The boom arm and bucket arrangement is mounted to a robust
mounting member 30 of the loader 10; the mounting member 30 serves
as a support or structural frame for the boom arm and bucket
arrangement. As illustrated in FIG. 3, the mounting member 30 is
substantially located at a forward region of the loader 10
substantially in front of the aforesaid control cabin. Moreover,
the boom arm and bucket arrangement comprises a boom arm 40 having
a proximate end pivotally mounted at a pivot 50 onto the mounting
member 30, and also a distal end pivotally coupled to the aforesaid
bucket as shown. The boom arm 40 is elongate and includes a bend
portion therealong. There is also included a first hydraulic
actuator 60 pivotally mounted at its first end by way of a pivot 70
to the mounting member 30. The pivot 70 of the actuator 60 is
located at a distance below the pivot 50 of the boom arm 40 as
illustrated. The actuator 60 is mounted at its second end to a
pivot 80 included on an interface member 90. The interface member
90 is itself attached to the boom arm 40 at a position
substantially corresponding to the aforesaid bend portion of the
boom arm 40. Towards the distal end of the boom arm 40 is included
a first elongate assembly member 200 pivotally coupled at its first
end via a pivot 210 to the boom arm 40. The first assembly member
200 is further coupled at its second end via a pivot 220 to a
second elongate assembly member 230 and also to a first end of a
second hydraulic actuator indicated by 300. The second assembly
member 230 is coupled at its second end via a pivot 240 to a first
region of a tool interfacing member 250. The tool interfacing
member 250 further includes a pivot 260 disposed in a spaced apart
manner from the pivot 240, the pivot 260 being operable to
pivotally couple the tool interfacing member 250 to the aforesaid
distal end of the boom arm 40. The aforementioned second actuator
300 is pivotally mounted at its second end to a pivot 270 disposed
spatially substantially midway between the pivots 240, 260 as
illustrated.
[0042] The tool interfacing member 250 is adapted to releasably
interchangeably receive a variety of tools and related devices. For
example, the interfacing member 250 is shown in FIG. 1 coupled to
the aforesaid bucket denoted by 310; the bucket 310 includes a base
panel 320 for holding and retaining a load in operation within the
bucket 310.
[0043] The boom arm 40 and its associated components are controlled
in operation from a control assembly denoted by 400. The control
assembly 400 includes an electronic control unit 410; the unit 410
is conveniently implemented using electronic hardware, for example
by way of computing hardware operable to execute software
instructions or dedicated hardware such as one or more application
specific integrated circuits (ASICs). The assembly 400 has
associated therewith an operator control console indicated by 420;
the console 420 is coupled to the electronic control unit 410 as
illustrated and will be elucidated in further detail later. The
electronic control unit 410 is connected to first and second
hydraulic control valves 430, 440 associated with the first and
second hydraulic actuators 60, 300 respectively. The first
hydraulic valve 430 includes hydraulic feed pipes or hoses 500 for
injecting and extracting hydraulic oil from the first actuator 60
for actuating the first actuator 60 in operation. Similarly, the
second hydraulic valve 440 includes hydraulic feed pipes or hoses
510 for injecting and extracting hydraulic fluid from the second
actuator 300 for actuating the second actuator 300 in
operation.
[0044] The vehicle 20 includes a rotation rate sensor 460
rotationally coupled to a rotating engine shaft of the engine 25
which drives the aforementioned one or more hydraulic pumps
operable to provide pressurized hydraulic oil to the valves 430,
440. The rotation rate sensor 460 generates in operation a rotation
rate signal 470 indicative of a rotation rate, namely RPM, of the
engine shaft. The rotation rate signal 470 is coupled to the
control unit 410. In operation, the control unit 410 modifies one
or more of its feedback parameters, for example feedback loop gain,
to improve feedback control stability in response to variations in
available hydraulic power available to drive the actuators 60,
300.
[0045] The first and second actuators 60, 300 include internally
therein position sensors 600, 610 for sensing in operation position
of pistons of the actuators 60, 300 relative to their cylinders,
namely measures of effective length of the actuators 60, 300
between their pivots 70, 80, 220, 270. The position sensors 600,
610 are preferably incorporated into the actuators 60, 300 in a
manner as depicted in FIG. 4 which will be further elucidated
later. On account of the position sensors 600, 610 being mounted
within their respective actuators 60, 300, they are well protected
from potential damage and degradation due to outdoor environmental
conditions. Moreover, mounting the sensors 600, 610 within the
actuators 60, 300 also enables better dynamic operating
characteristics for the loader 10 to be achieved as will be
described in further detail later. Position signals 740, 750
derived from the sensors 600, 610 respectively are conveyed in
operation to the electronic control unit 410.
[0046] The aforementioned console 420 includes first and second
operator-adjustable controls 700, 710; conveniently, the controls
700, 710 are implemented as continuously moveable joy-sticks or
levers although other implementations are possible. In operation,
the first and second controls 700, 710 give rise to first and
second reference signals 720, 730 representative of desired height
and inclination tilt angle of the bucket 310 respectively. These
reference signals 720, 730 are conveyed to the electronic control
unit 410 which is operable to, in a complex manner, compare the
reference signals 720, 730 with the position signals 740, 750 and
thereby generate appropriate output signals 760, 770 to control the
first and second valves 430, 440 respectively.
[0047] In comparison to contemporary known loaders described in the
foregoing, the electronic control unit 410 is operable to perform
more complex signal processing on account of the signals 740, 750
from the position sensors 600, 610 not being directly indicative of
angular orientation of the boom arm 40 and the bucket 310.
[0048] In overview, the loader 10 is operable in dynamic situations
to function in a different manner to known contemporary loaders.
When applying feedback in general to mechanical systems, it is
known that it is more difficult to stabilize such feedback when the
system in an open-loop state is susceptible to exhibiting complex
multiple pole-zeroes in its frequency response. Such feedback
problems are further confounded when the mechanical systems exhibit
back-lash, namely "dead regions" in spatial response. Moreover,
such feedback is even more difficult to optimize when system
characteristics are susceptible to temporally change; for example,
the boom arm 40 has elasticity and is susceptible to elastically
deforming and thereby functioning as a spring denoted by K in FIG.
2. Substantially at the distal end of the boom arm 40 is included
the bucket 310 together with its associated members 200, 230, 250
which collectively form a mass denoted by M in FIG. 2. This mass M
is susceptible to variation depending upon a weight of a load 1200
carried in the bucket 310.
[0049] A pressure of hydraulic oil provided from the one or more
pumps to the valves 430, 440 is also a factor affecting
responsiveness of the actuators 60, 300, namely response time
constants exhibited by the loader 10. In order to improve user
handling performance of the loader 10, the control unit 410 is
operable to vary one or more of its feedback parameters, for
example one or more of its feedback loop gains, or one or more of
its feedback loop time constants, in order to improve handling
responsiveness and stability of the loader 10.
[0050] Conventionally, to address a potentially variable open-loop
system response, two approaches are possible:
[0051] (a) vary the feedback applied in response to changes in
open-loop characteristics of a system to be controlled, namely
characteristics of the boom arm 40 and its associated distal mass
M; or
[0052] (b) apply a form of feedback which can cope with a full
range of open-loop characteristics of the system to be controlled,
namely characteristics of the boom arm 40 and its mass M.
[0053] Whereas the approach (a) represents further complexity in
that dynamic response characteristics of the boom arm 40 and its
mass M need to be periodically evaluated, the approach (b) results
in sluggish performance which is manifest in sluggish and
inaccurate response to adjustments of the first and second controls
700, 710 adversely affecting efficiency of use of the loader 10 and
potentially reducing operating safety.
[0054] The inventors of the present invention have surprisingly
found that the implementation of the loader 10 depicted in FIG. 1
potentially offers considerable advantages in comparison to
contemporary loaders described in the foregoing. By employing the
feedback signals 740, 750 derived directly from the position
sensors 600, 610 in the actuators 60, 300, there is provided a
direct form of feedback which is susceptible to being of a
relatively lower-order system response. Such a low order system
response results in the feedback being more stable and responsive.
Thus, the configuration of the actuators 60, 300 and the control
assembly 400 depicted in FIG. 1 is capable of providing the
operator of the first and second controls 700, 710 with more
accurate and faster feedback control. Moreover, the loader 10 as
depicted in FIG. 1 would be superficially less attractive to employ
in view of the complexity of signal processing required to be
implemented in the control assembly 400.
[0055] Referring to FIG. 2, there is shown a simplified geometrical
representation of the loader 10 illustrated in FIG. 1. A parameter
"a" represents a length of the first actuator 60 between its
associated pivots 70, 80. Moreover, a parameter "b" represents a
spatial distance between the pivots 50, 70. Furthermore, a
parameter "c" represents a distance between the pivots 50, 80.
Thus, the pivots 50, 70, 80 define a triangle which, in operation,
is susceptible to having its parameter "a" varied as the first
hydraulic actuator 60 is actuated. At the pivot 50, there is
subtended an angle .theta. as illustrated. This angle .theta. can
be described using geometry as in Equation 1 (Eq. 1):
.theta. = cos - 1 ( c 2 + b 2 - a 2 2 bc ) Eq . 1 ##EQU00001##
[0056] On account of the bend portion of the boom arm 40, an
orientation .theta.d of the distal end of the boom arm 40 at the
pivot 260 is described by Equation 2 (Eq. 2):
.theta..sub.d=.theta.+.theta..sub.0 Eq. 2
[0057] wherein .theta.0 is a constant angular offset. In a similar
manner, an angle .gamma. associated with the bucket 310 as
illustrated can be determined from geometrical analysis. The
elongate member 200 has a length denoted by a parameter "e" between
its associated pivots 210, 220. Moreover, a distance between the
pivots 210, 260 is denoted by a parameter "d". Furthermore, a
distance between the pivots 220, 240 is denoted by a parameter "f.
Additionally, a distance between the pivots 240, 260 is denoted by
"g". All four parameters "d", "e", "f and "g" are substantially
constant as they are determined by the lengths of their associated
members 200, 230, 250 or portion of the boom arm 40. The second
actuator 300 is operable to substantially modify a spatial distance
denoted by a parameter "h" between the pivots 220, 260 to affect
changes in the angle .gamma.. The angle .gamma. can be
substantially computed from Equation 3 (Eq. 3):
.gamma. = cos - 1 ( d 2 + h 2 - e 2 2 dh ) + cos - 1 ( g 2 + h 2 -
f 2 2 gh ) Eq . 3 ##EQU00002##
[0058] Thus, an inclination angle .alpha. of the bucket 310 can be
computed from Equations 2 and 3 as combined in Equation 4 (Eq.
4):
.alpha. = .theta. 1 + cos - 1 ( c 2 + b 2 - a 2 2 bc ) + cos - 1 (
d 2 + h 2 - e 2 2 dh ) + cos - 1 ( g 2 + h 2 - f 2 2 gh ) Eq . 4
##EQU00003##
wherein .theta..sub.1 is another angular offset constant. The
parameters "a" and "h" are dependent on actuation of the actuators
60, 300 respectively. It is desired that the inclination angle
.alpha. is a direct simple function of position of the control 700
and not substantially influenced by adjustment of the control
710.
[0059] Moreover, from further geometrical analysis, a substantial
height H of the bucket 310 above a ground level, for example as
denoted on an axis 1030 in FIG. 3, can be computed from Equation 5
(Eq. 5):
H = H 0 + L sin ( .theta. - .pi. 2 ) Eq . 5 ##EQU00004##
wherein H.sub.0 is a height offset constant and the angle .theta.
is as defined in Equation 1 such that the angle .theta. is
substantially a function of a length of the first actuator 60, and
L is an effective length of the boom arm 40 from its proximate end
to its distal end.
[0060] Equations 1 to 5 can be summarized by Equations 6 (Eqs.
6):
.alpha.=F.sub.1(S.sub.1,S.sub.2); H=F.sub.2(S.sub.1) Eqs. 6
[0061] wherein S.sub.1, S.sub.2 correspond to the position signals
740, 750 respectively. Measures of the inclination angle .alpha.
and the height H derived from the position signals 740, 750 are
compared with corresponding reference signals 720, 730 in the
electronic control unit 410 and the signals 760, 770 appropriately
adjusted to minimize a difference between the sensed inclination
angle .alpha. and the reference signal 720, and also to minimize a
difference between the measured height H and the reference signal
730. By doing so, the operator adjusting the controls 700, 710 will
find that the control 700 responsively and accurately determines
the inclination angle .alpha. of the bucket 310, and the control
710 responsively and accurately determines the height of the bucket
310.
[0062] It will be appreciated that the electronic control unit 410
can either employ computations to solve Equations 6 in real time,
or otherwise employ pre-calculated look-up tables.
[0063] Operation of the loader 10 will now be further elucidated
with reference to FIG. 3. It is found ergonomically optimal that
tilt and height of the bucket 310 are independently adjustable by
the operator, thereby potentially reducing a risk of accident. It
is highly desirable that the control 710 only adjusts height of the
bucket 310 so that its contents, namely the load 1200, do not fall
out of the bucket 310 when the boom arm 40 is adjusted in position.
As illustrated in FIG. 1, the base panel 320 of the bucket 310 has
a slight front upwardly-curved lip for assisting in retaining the
load 1200 within the bucket 310. In FIG. 3, the aforesaid
counterbalance is denoted by 1000. Dynamic mechanical
characteristics of the loader 10 are not only affected by a weight
of the load 1200 carried within the bucket 310 but also, to a
lesser extent, by a weight of the counterbalance 1000. When the
bucket 310 is provided with an extension 1020 as illustrated in
FIG. 3, it is especially desirable that accurate control of the
inclination angle .alpha. is achieved.
[0064] The loader 10 is susceptible to function in both a
transportation mode as well as a digging mode. In the
transportation mode, the member 250 is beneficially provided with a
fork arrangement as depicted in FIG. 3; this fork arrangement can
either be additional to the bucket 310 or in substitution thereof.
In the transportation mode, the electronic control unit 410 is
configured to be able to maintain a substantially constant
inclination angle .alpha. in response to different heights H
selected by the operator using the control 710; in other words,
parallelism of the work piece is maintained in operation. For
enhancing safety, a table of lifting capacities as a function of
lifting height H can be stored in the electronic control unit 410;
the electronic control unit 410, for purposes of enhancing
operating safety, can intentionally limit the height H demanded by
the operator using the control 710 so that the loader 10 is not
operated beyond its safe range of operation. Optionally, the
electronic control unit 410 is operable to inform the operator when
the unit 410 intentionally limits operation to the limited height
H. As a further refinement, the electronic control unit 410 can be
configured to limit a rate at which the load 1200 is lowered,
namely a rate at which H is reduced, so as to avoid shock damage to
the load 1200.
[0065] Conversely, in the digging mode of operation, limits to a
range of heights H through which the bucket 310 is capable of being
manipulated are stored in memory of the electronic control unit
410, for example a highest position and a lowest position.
Similarly, maximum and minimum inclination angles .alpha.
achievable for the bucket 310 can also be stored in the electronic
control unit 410. These limits can be stored as preset positions
which the operator can invoke by pressing appropriate control
switches or similar. For example, there can be provided a "return
to dig" control to enable the operator to rapidly invoke a stored
and therefore memorized digging position for the bucket 310.
[0066] A further refinement to the loader 10 is illustrated in FIG.
5. The vehicle 20 of the loader 10 is further provided with an
inertial sensor unit 5000. In its simplest implementation, the
sensor unit 5000 is operable to measure inclination of the vehicle
20, for example when operating over uneven or sloping terrain. A
vehicle inclination indicative signal present in an output signal
5010 from the sensor unit 5000 is beneficially, for example in the
aforementioned transportation mode of operation, applied to modify
the reference signal 720 controlling the inclination angle .alpha.
of the bucket 310 so as to generate via a summing function 5020 a
modified reference signal 5030 for use in controlling the first and
second actuators 60, 300. By appropriately modifying the desired
inclination angle .alpha., operating safety of the loader 10 is
potentially improved when operating over inclined or uneven
terrain. As a further modification, the sensor unit 5000 also
includes one or more accelerometers and wheel sensors for measuring
forward or reverse speed of the vehicle 20 and also a rate of
deceleration or acceleration demanded by the aforesaid operator
when operating the loader 10. In response to the acceleration and
deceleration, and also in response to a direction of travel of the
vehicle 20, namely forward or reverse, the desired inclination
angle .alpha. of the bucket 310 can be momentarily modified so as
to retain the load 1200 more safely within the bucket 310. For
example, when the vehicle 20 is traveling in a forward direction
and is subject to deceleration, the inclination angle .alpha. is
beneficial momentarily increased during deceleration so that the
load 1200 is less likely to be ejected from the bucket 310.
Similarly, when the vehicle 20 is traveling in a reverse direction
and is subject to acceleration, the inclination angle .alpha. is
beneficial momentarily increased during acceleration so that the
load 1200 is less likely to be ejected from the bucket 310. Such
compensation of the inclination angle .alpha. in response to
measurement signals provided from the sensor unit 5000 is
optionally selectable by the operator in a situation where the
operator deliberately accelerates the vehicle 20 rapidly backwards
for dislodging and hence depositing the load 1200. Furthermore,
when the sensor unit 500 includes accelerometers, a measurement of
an unevenness of a terrain over which the vehicle 20 is traveling
can be ascertained in order to automatically reduce the height H at
which the load 1200 is carried and/or increase the inclination
angle .alpha. so as to reduce a risk of accident or unintentional
dropping of the load 1200. As elucidated in the foregoing,
inclusion of the rotation rate sensor 460 enables the control unit
410 to modify one or more feedback parameters influencing the
signals 760, 770 and thereby improving stability and hence
operating safety of the loader 10.
[0067] It will be appreciated from the foregoing that the present
invention is not only capable of providing the operator of the
loader 10 with more precise and stable control of the load 1200,
but is also capable of increasing operator safety, both when the
loader 10 is stationary and when transporting the load 1200 between
locations. Such enhancement would not be contemporarily anticipated
in that more comprehensive feedback around configurations of
mechanical components would be perceived to be a logical approach
to improving performance.
[0068] In order that the present invention is comprehensively
described, implementation of the actuators 60, 300 will elucidated
with reference to FIG. 4. In FIG. 4, a cross-sectional view of the
actuators 60, 300 is provided. Each actuator 60, 300 comprises a
first end substantially circular housing eye 2000 comprising a
central mounting hole 2005, and also a second end substantially
circular housing eye 2010 also comprising a central mounting hole
2015. The first end housing eye 2000 is attached to a proximate end
of a piston rod 2020. Substantially at a distal end of the piston
rod 2020 is included a piston 2030 implemented as an annulus
surrounding the piston rod 2020. The piston rod 2020 has formed
therein an elongate central hole as shown, the central hole having
an opening at the distal end of the piston rod 2020. Moreover, the
second housing eye 2010 is attached to a proximate end of a
cylinder 2040, the cylinder 2040 having at its distal end an
integral annular collar providing a hydraulic seal to an outer
surface of the piston rod 2020. An outer annular surface of the
piston 2030 is operable to provide a hydraulic seal to an inner
surface of the cylinder 2040 as illustrated. Thus, in operation,
the first housing eye 2000 together with its piston rod 2020 and
its piston 2030 are capable of sliding relative to the cylinder
2040 and its associated second housing eye 2010. In the cylinder
2040, the piston 2030 is operable to define first and second
chambers 4000, 4010 which are preferentially supplied with
hydraulic oil under pressure in order to actuate the piston 2030
and hence the piston rod 2020 relative to the cylinder 2040.
[0069] The aforesaid sensors 600, 610 are implemented for each
actuator 60, 300 by way of a magnetic transducer 3000 provided with
a robust electrical connection 3010 at a peripheral surface of the
second housing eye 2010. The aforesaid signals 740, 750 are derived
via the electrical connections 3010 of the actuators 60, 300
respectively. The transducer 3000 includes a central shaft 3020
adapted to be accommodated within the aforesaid central hole of the
piston rod 2020. Substantially at the distal end of the piston rod
2020, at an inside surface of the central hole thereof, an annular
magnetic component 3030 is included. In operation, the magnetic
component 3030 slides together with the piston rod 2020 relative to
the central shaft 3020 thereby modifying a magnetic characteristic
of the transducer 3000. Such modification of the magnetic
characteristics of the transducer 3000 provides a measure of
relative position of the piston rod 2020 relative to the central
shaft 3020 and hence an indication of a length of the actuator
between its housing eyes 2000, 2010. Either changes in inductance
or change in magnetic field strength experienced by the transducer
3000 are used to generate the signals 740, 750. Use of magnetic
sensing is found to be especially robust in practice, especially in
view of the cylinder 2040 being operable to provide magnetic
shielding for the transducer 3000, and relatively insignificantly
affected by trace hydraulic oil and other debris arising within the
actuators 60,300 during prolonged periods of use.
[0070] Modifications to embodiments of the invention described in
the foregoing are possible without departing from the scope of the
invention as defined by the accompanying claims.
[0071] Expressions such as "including", "comprising",
"incorporating", "consisting of, "have", "is" used to describe and
claim the present invention are intended to be construed in a
non-exclusive manner, namely allowing for items, components or
elements not explicitly described also to be present. Reference to
the singular is also to be construed to relate to the plural.
[0072] Numerals included within parentheses in the accompanying
claims are intended to assist understanding of the claims and
should not be construed in any way to limit subject matter claimed
by these claims.
* * * * *