U.S. patent application number 11/711744 was filed with the patent office on 2007-08-30 for acceleration sensor status detecting apparatus.
This patent application is currently assigned to Aisin Seiki Kabushiki Kaisha. Invention is credited to Kentaro Hirose, Hiroyuki Ichikawa, Kenichi Sato.
Application Number | 20070199373 11/711744 |
Document ID | / |
Family ID | 38442762 |
Filed Date | 2007-08-30 |
United States Patent
Application |
20070199373 |
Kind Code |
A1 |
Sato; Kenichi ; et
al. |
August 30, 2007 |
Acceleration sensor status detecting apparatus
Abstract
An acceleration sensor state detecting apparatus for detecting a
state of an acceleration sensor provided at a vibrating body
includes a calculating method for calculating a difference between
measured results of the acceleration sensor obtained per first
predetermined time that is shorter than a vibration period of the
vibrating body, and a determining method for determining that the
acceleration sensor is in an error state in a case that a state in
which the difference calculated falls into a range between a
predetermined upper limit value and a predetermined lower limit
value continues for a second predetermined time or more.
Inventors: |
Sato; Kenichi; (Nagoya-shi,
JP) ; Hirose; Kentaro; (Yokkaichi-shi, JP) ;
Ichikawa; Hiroyuki; (Kani-shi, JP) |
Correspondence
Address: |
REED SMITH LLP
Suite 1400, 3110 Fairview Park Drive
Falls Church
VA
22042
US
|
Assignee: |
Aisin Seiki Kabushiki
Kaisha
TOKAI Rubber Industries, Ltd.
|
Family ID: |
38442762 |
Appl. No.: |
11/711744 |
Filed: |
February 28, 2007 |
Current U.S.
Class: |
73/114.07 ;
702/41 |
Current CPC
Class: |
G01P 21/00 20130101 |
Class at
Publication: |
73/118.1 ;
702/41 |
International
Class: |
G01M 19/00 20060101
G01M019/00; G01L 3/00 20060101 G01L003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2006 |
JP |
2006-052238 |
Claims
1. An acceleration sensor state detecting apparatus for detecting a
state of an acceleration sensor provided at a vibrating body,
comprising: a calculating means for calculating a difference
between measured results of the acceleration sensor obtained per
first predetermined time that is shorter than a vibration period of
the vibrating body; and a determining means for determining that
the acceleration sensor is in an error state in a case that a state
in which the difference calculated falls into a range between a
predetermined upper limit value and a predetermined lower limit
value continues for a second predetermined time or more.
2. An acceleration sensor state detecting apparatus according to
claim 1, wherein the first predetermined time is equal to or
smaller than a third of a half period of the vibration period.
3. An acceleration sensor state detecting apparatus according to
claim 1, further comprising a frequency detecting means for
measuring a vibration frequency of the vibrating body, wherein at
least one of the first predetermined time and the second
predetermined time is determined on the basis of a measured result
of the frequency detecting means.
4. An acceleration sensor state detecting apparatus according to
claim 2, further comprising a frequency detecting means for
measuring a vibration frequency of the vibrating body, wherein at
least one of the first predetermined time and the second
predetermined time is determined on the basis of a measured result
of the frequency detecting means.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and claims priority under 35
U.S.C. .sctn. 119 to Japanese Patent Application No. 2006-052238,
filed on Feb. 28, 2006, the entire content of which is incorporated
herein by reference.
FIELD OF THE INVENTION
[0002] This invention generally relates to an acceleration sensor
state detecting apparatus. More particularly, this invention
pertains to an acceleration sensor state detecting apparatus that
detects a state of an acceleration sensor provided at a vibrating
body.
BACKGROUND
[0003] In the case of eliminating or preventing vibration of a
vibrating body such as an engine by using a vibration isolator, for
example, an acceleration sensor is provided at an engine mount so
as to control the vibration isolator based on a measured result of
the acceleration sensor. In this case, if the acceleration sensor
does not operate normally and properly, the vibration isolator
cannot be controlled correctly and thus an effective elimination of
vibration cannot be achieved. In order to avoid such issue, various
acceleration sensor state detecting apparatuses have been
considered for detecting whether the acceleration sensor operates
properly.
[0004] JP07-174787A and JP11-190741A each disclose an acceleration
sensor state detecting apparatus. According to the acceleration
sensor state detecting apparatus disclosed in JP07-174787A, an
upper limit value and a lower limit value are defined relative to a
measured result of an acceleration sensor on the basis of a
measured object thereof. When a state in which the measured result
is above the upper limit value or below the lower limit value
continues for a predetermined time or more, an error in the
acceleration sensor is determined. In addition, according to the
acceleration sensor state detecting apparatus disclosed in
JP11-190741A, a rotation sensor for detecting a rotation speed of
wheels is provided so as to detect a state of an acceleration
sensor that measures an acceleration of a vehicle in motion. Then,
an acceleration acquired on the basis of a measured result of the
rotation sensor, and a measured result of the acceleration sensor
are compared so as to detect an error in the acceleration
sensor.
[0005] According to the acceleration sensor state detecting
apparatus disclosed in JP07-174787A, the error in the acceleration
sensor can be detected if the measured value thereof is retained
over the upper limit value or below the lower limit value. However,
an error that may possibly occur in the acceleration sensor when
the measured value is specified between the upper limit value and
the lower limit value cannot be detected. Further, according to the
acceleration sensor state detecting apparatus disclosed in
JP11-190741A, an error in the acceleration sensor occurring when
the measured value thereof is retained between the upper limit
value and the lower limit value can be detected. However, since the
measured values by the other sensor and the acceleration sensor are
compared for the detection of the error in the acceleration sensor,
an error that might occur, in fact, in the other sensor may be
mistakenly determined as the error in the acceleration sensor.
[0006] Thus, a need exists for an acceleration sensor state
detecting apparatus that can accurately detect a state of an
acceleration sensor.
SUMMARY OF THE INVENTION
[0007] According to an aspect of the present invention, an
acceleration sensor state detecting apparatus for detecting a state
of an acceleration sensor provided at a vibrating body includes a
calculating method for calculating a difference between measured
results of the acceleration sensor obtained per first predetermined
time that is shorter than a vibration period of the vibrating body,
and a determining method for determining that the acceleration
sensor is in an error state in a case that a state in which the
difference calculated falls into a range between a predetermined
upper limit value and a predetermined lower limit value continues
for a second predetermined time or more.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The foregoing and additional features and characteristics of
the present invention will become more apparent from the following
detailed description considered with reference to the accompanying
drawings, wherein:
[0009] FIG. 1 is a block diagram illustrating a structure of an
acceleration sensor state detecting apparatus;
[0010] FIG. 2 is a block diagram illustrating a vibration isolator
of an automobile engine;
[0011] FIGS. 3A and 3B are views illustrating an example condition
for determining a state of the acceleration sensor; and
[0012] FIG. 4 is a flowchart for detecting a state of the
acceleration sensor.
DETAILED DESCRIPTION
[0013] An embodiment of the present invention will be explained
with reference to the attached drawings.
[0014] FIG. 1 is a block diagram illustrating a structure of an
acceleration sensor state detecting apparatus 10. The state
detecting apparatus 10 according to the present embodiment detects
a state of an acceleration sensor 7 based on an output signal g
that is a measured result of the acceleration sensor 7. The state
detecting apparatus 10 includes a calculating means 11 and a
determining means 12. The calculating means 11 calculates a
difference between measured results of the acceleration sensor 7
that are obtained per first predetermined time dt. The determining
means 12 determines whether the acceleration sensor 7 operates
normally and properly on the basis of the calculated difference of
the measured results, and, for example, predetermined upper limit
and lower limit values that have been specified according to a
vibrating state of a vibrating body. Precisely, the determining
means 12 determines that an error occurs in the acceleration sensor
7 when a state, in which the calculated difference of the measured
results falls into a range between the upper limit value and the
lower limit value, continues for a second predetermined time or
longer.
[0015] According to the present embodiment, the output signal from
the acceleration sensor 7 is amplified by an input interface
circuit 5d for signal amplification, for example, and is then input
as an amplified signal G to the calculating means 11. The
calculating means 11 calculates a difference .DELTA.G in the
amplified signal G that is obtained per first predetermined time
dt. The determining means 12 determines whether the acceleration
sensor 7 operates normally on the basis of the calculated
difference .DELTA.G.
[0016] The state detecting apparatus 10 also includes a frequency
detecting means 41 for detecting a vibration frequency of the
vibrating body. A detection result of the frequency detecting means
41 is transmitted via an input interface circuit 5a to the
calculating means 11. The calculating means 11 determines the first
predetermined time dt based on the detection result of the
frequency detecting means 41.
[0017] A case in which the state detecting apparatus 10 is employed
in a vibration isolator 100 of an engine 13 of a vehicle will be
explained with reference to FIG. 2. The vibration isolator 100 of
the engine 13 (vibrating body) generates vibration in an opposite
phase to that of the engine 13. Precisely, the anti-phase vibration
is generated by a solenoid 2 arranged at an engine mount 9
(vibrating body) so as to prevent the vibration of the engine 13
from being transmitted to a vehicle body.
[0018] As illustrated in FIG. 2, the vibration isolator, precisely,
a vibration control ECU (Electronic Control Unit) 100 includes a
microcomputer 1, a solenoid drive circuit 3, a power supply circuit
8, interface circuits 5a to 5d that perform electrical matching
with various peripheral devices, and the like. In this case, the
various peripheral devices include an engine control unit 4, an
in-vehicle communication bus 6 connected to other control units,
and the like.
[0019] The microcomputer 1, which forms the core of the vibration
control ECU 100, functions as the state detecting apparatus 10
according to the present embodiment. The microcomputer 1 receives
an engine rotational signal (hereinafter referred to as "TACH
signal") via the input interface circuit 5a from the engine control
unit 4. Afterwards, the microcomputer 1 generates a control signal
such as a control pulse signal for driving the solenoid 2, which is
then output to the solenoid drive circuit 3. Precisely, the
microcomputer 1 outputs the control signal for switching a
direction of power supply of the solenoid 2, a pulse width
modulation signal Po, and the like.
[0020] As mentioned above, the solenoid 2 is controlled by the
microcomputer 1 so that the solenoid 2 generates the vibration in
an opposite phase to that of the engine 13. In order to monitor the
vibrating state of the engine 13, the acceleration sensor 7 is
provided at the engine mount 9. The acceleration sensor 7 inputs an
acceleration signal obtained by the vibration of the engine 13 via
an input interface circuit 5c to the microcomputer 1. The
microcomputer 1 controls the solenoid 2 based on the acceleration
signal from the acceleration sensor 7. At this time, the vibration
of the engine 13 may be influenced by temperature, and the like.
Accordingly, in order to improve accuracy of vibration control,
information such as outside air temperature is input from the other
control unit that includes a temperature sensor and the like to the
microcomputer 1 via the communication bus 6 and a communication
interface 5b.
[0021] The microcomputer 1 includes a ROM that stores a program, a
RAM serving as a backup memory during execution of a program, a
timer that calculates a rotational number of the engine 13 based on
the TACH signal, an A/D (analog-digital) converter that digitalizes
an input voltage from the acceleration sensor 7, and the like.
Further, since a power supply voltage of the microcomputer 1 is
low, i.e. 5V, 3.3V or the like in general, a voltage provided to
the microcomputer 1 from a battery (not shown), i.e. 12V, 24V or
the like, is converted by the power supply circuit 8.
[0022] Meanwhile, a relatively high voltage such as 12V or 24V is
provided via the battery or the power supply circuit 8 to the
solenoid 2 and the solenoid drive circuit 3 since the solenoid 2
and the solenoid drive circuit 3 are power circuits. The solenoid
drive circuit 3 includes a bridge circuit for driving the solenoid
2 and a driver circuit for pressurizing a low voltage control
signal input from the microcomputer 1 and connecting that
pressurized control signal to the bridge circuit. The bridge
circuit includes a power transistor, a power MOSFET (metal oxide
semiconductor field effect transistor), and the like. The
microcomputer 1 performs PWM control on the solenoid 2 by means of
the solenoid drive circuit 3.
[0023] The acceleration signal from the acceleration sensor 7 as
mentioned above is also input to the microcomputer 1 via the input
interface circuit 5d for signal amplification. The microcomputer 1,
which serves as the state detecting apparatus 10 according to the
present embodiment, determines whether the acceleration sensor 7
operates normally and appropriately on the basis of the amplified
acceleration signal. Further, the microcomputer 1 determines a
first predetermined time, a second predetermined time, and upper
and lower limit values used for error detection based on the TACH
signal input through the input interface circuit 5a from the engine
control unit 4. At this time, the first predetermined time may be
equal to or smaller than a third of a half vibration period of the
engine 13.
[0024] Next, the detection of an error in the acceleration sensor 7
conducted by the state detecting apparatus 10 will be explained
with reference to FIGS. 3A and 3B. FIGS. 3A and 3B are views
illustrating an example condition used for determining whether the
acceleration sensor 7 is in an error state or not. Precisely, FIG.
3A illustrates g (t) that is a change with time in output signal g
from the acceleration sensor 7. FIG. 3B illustrates g (t)/dt that
is a variation in g (t) per first predetermined time. T1, T2 and T3
in FIGS. 3A and 3B each illustrate one vibration period of the
engine 13. Tth in FIG. 3B is a determination time for determining
that the acceleration sensor 7 is in the error state and
corresponds to the second predetermined time according to the
present embodiment. As illustrated in FIGS. 3A and 3B, the
acceleration sensor 7 operates normally and appropriately in the
period of T1 and T2. On the other hand, during and after the period
of T3, the acceleration sensor 7 is in the error state in which,
for example, the change with time in output signal g (t) is
retained at a substantially constant value. The acceleration sensor
7 is in the error state when a wiring for output the acceleration
signal is shorted with the other wiring, the acceleration cannot be
detected because of the failure of the acceleration sensor 7
itself, and the like.
[0025] Even during the operation of the vibration isolator 100, the
vibration of the engine 13 is not completely eliminated.
Accordingly, when the acceleration sensor 7 is in the normal
operating state, the acceleration sensor 7 detects the vibration
and then the change with time in output signal g (t) represents a
vibration waveform as in the period of T1 and T2 in FIG. 3A. On the
other hand, when the acceleration sensor 7 is in the error state,
the change with time in output signal g (t) represents, for
example, a substantially constant value as in the period of T3 in
FIG. 3A instead of the vibration waveform.
[0026] As illustrated in FIG. 3B, in the cases where the
acceleration sensor 7 is in the normal operating state, the
variation in g (t) per first predetermined time dg (t)/dt
represents the vibration waveform. Thus, dg (t)/dt exceeds an error
detection upper limit value gth and falls below an error detection
lower limit value -gth one time each during one vibration period of
the engine 13. On the other hand, in the cases where the
acceleration sensor 7 is in the error state, dg (t)/dt is retained
at a substantially constant value. Thus, dg (t)/dt is defined to be
within a range between the error detection upper limit value gth
and the error detection lower limit value -gth. Accordingly, by
monitoring whether a state, in which calculated dg (t)/dt is not
above the upper limit value and not below the lower limit value,
continues for the determination time Tth (which corresponds to the
second predetermined time according to the present embodiment), the
error in the acceleration sensor 7 can be determined. The
determination time Tth is defined on the basis of frequency of the
engine 13 and is equal to or greater than a half period, more
precisely, one period, of the vibration of the engine 13, for
example.
[0027] For the purpose of simple explanation, an example of
detecting the error in the acceleration sensor 7 by monitoring the
variation in g (t) per first predetermined time dg (t)/dt is
illustrated in FIGS. 3A and 3B. In this case, in fact, since dt is
an extremely short period, the variation in g (t) per first
predetermined time dg (t)/dt is extremely small. Accordingly, the
amplified signal G obtained by amplifying the output signal g from
the acceleration sensor 7 may be used. Then, the difference
.DELTA.G in the amplified signal G is used for detecting the state
of the acceleration sensor 7. Further, a signal such as a high
frequency noise other than the measured result of the acceleration
sensor 7 may be mixed with the output signal of the acceleration
sensor 7. Thus, a noise may be appropriately eliminated by means of
a low-pass filter. According to the present embodiment, a phrase of
"on the basis of the measured result of the acceleration sensor 7"
includes not only a case in which the output signal g of the
acceleration sensor 7 is used as it is but also a case in which the
output signal g that has been appropriately processed, i.e.
amplified or filtered, is used.
[0028] An example of procedures for detecting the error in the
acceleration sensor 7 by the state detecting apparatus 10 will be
explained with reference to a flowchart illustrated in FIG. 4.
According to the present embodiment, the state of the acceleration
sensor 7 is detected by using the amplified signal G that is
obtained by amplifying the output signal g from the acceleration
sensor 7. In Step 1 (Step will hereinafter be referred to as "S"),
the calculating means 11 obtains an amplified signal Gn. Then, in
S2, the calculating means 11 calculates .DELTA.Gn, which is a
difference between the amplified signal Gn currently obtained and
an amplified signal Gn-1 obtained immediately before the amplified
signal Gn.
[0029] The determining means 12 receives the difference .DELTA.Gn
calculated by the calculating means 11 and determines whether or
not the difference .DELTA.Gn is above a predetermined upper limit
value Gth and below a predetermined lower limit value -Gth in S3.
When it is determined that the difference .DELTA.Gn is neither
above the upper limit value Gth nor below the lower limit value
-Gth, i.e. the difference .DELTA.Gn falls into a range between the
upper limit value Gth and the lower limit value -Gth, an error time
counter CT is incremented by one in S5. Meanwhile, when it is
determined that the difference .DELTA.Gn is above the upper limit
value Gth or below the lower limit value -Gth in S3, the error time
counter CT is reset to zero in S4. Afterwards, the error time
counter CT and an error time upper limit value CTMAX (which
corresponds to the second predetermined time according to the
present embodiment) are compared in S6. When it is determined that
the error time counter CT exceeds the error time upper limit value
CTMAX, the acceleration sensor 7 is determined as in the error
state in S7. At this time, an occupant of the vehicle may be warned
of the error in the acceleration sensor 7 by a warning light turned
on, for example. In addition, the controlling method of the
vibration isolator 100 may be switched to a method not relating to
the measured result of the acceleration sensor 7. On the other
hand, when it is determined that the error time counter CT is equal
to or smaller than the error time upper limit value CTMAX in S6,
the acceleration sensor 7 is not determined as in the error state.
The processes from S1 to S6 are repeated so as to keep detecting
the state of the acceleration sensor 7.
[0030] According to the aforementioned embodiment, the difference
.DELTA.G is obtained by subtracting the amplified signal Gn-1
acquired immediately before the currently obtained amplified signal
Gn therefrom. However, the difference .DELTA.G may be obtained by
subtracting an amplified signal Gn-2 from the currently acquired
amplified signal Gn, or the like. Further, according to the
aforementioned embodiment, absolute values of the upper limit value
and the lower limit value are identical with each other. However,
the absolute values can be different from each other.
[0031] According to the aforementioned embodiment, in order to
detect the state of the acceleration sensor 7 provided at the
engine mount 9, the acceleration sensor 7 is determined as in the
error state when a sate, in which the difference between the
measured results of the acceleration sensor 7 obtained per first
predetermined time through calculation by the calculating means 11
is neither above the predetermined upper limit value Gth nor below
the predetermined lower limit value -Gth, continues for the second
predetermined time or longer. That is, the state of the
acceleration sensor 7 is detected on the basis of the measured
result of the acceleration sensor 7, i.e. on the basis of whether
the measured result fluctuates. Accordingly, even when the measured
result of the acceleration sensor 7 is fixed at an intermediate
value between the upper limit value and the lower limit value, the
error in the acceleration sensor 7 can be detected. Further, the
state of the acceleration sensor 7 is detected on the basis of the
measured result of the acceleration sensor 7 itself instead of a
comparison between a measured result of the other sensor and a
measured result of the acceleration sensor 7 as in the conventional
manner. Thus, the error in the acceleration sensor 7 can be
prevented from being wrongly detected at the time the acceleration
sensor 7 is actually in the normal operating state. The
acceleration sensor state detecting apparatus with high reliability
can be obtained accordingly. As a result, the state of the
acceleration sensor 7 can be appropriately detected.
[0032] Further, according to the aforementioned embodiment, at
least three measured results used for acquiring the difference
therebetween can be obtained within a half vibration period of the
engine 13. That is, the difference is not obtained from identical
measured values. As a result, the error in the acceleration sensor
7 can be prevented from being wrongly detected at the time the
acceleration sensor 7 is actually in the normal operating
state.
[0033] Furthermore, according to the aforementioned embodiment, the
first predetermined time and the second predetermined time can be
defined, on the basis of the measured result of a frequency
detecting means, to an appropriate value in response to the number
of vibrations of the vibrating body. As a result, the state of the
acceleration sensor can be more precisely detected.
[0034] The principles, preferred embodiment and mode of operation
of the present invention have been described in the foregoing
specification. However, the invention which is intended to be
protected is not to be construed as limited to the particular
embodiments disclosed. Further, the embodiments described herein
are to be regarded as illustrative rather than restrictive.
Variations and changes may be made by others, and equivalents
employed, without departing from the spirit of the present
invention. Accordingly, it is expressly intended that all such
variations, changes and equivalents which fall within the spirit
and scope of the present invention as defined in the claims, be
embraced thereby.
* * * * *