JPH0459481A - Failure detecting device for vehicle steering angle control device - Google Patents

Abstract

PURPOSE:To perform the correct failure judgment of a steering angle control system by avoiding the failure judgment in the high-frequency area where the steering angle control system is liable to generate control errors, and performing the failure judgment in the low-frequency operating area where the control error surely should be near zero. CONSTITUTION:A steering angle detecting means detecting the actual steering angle, a deviation calculating means calculating the deviation between the actual steering angle of the steering angle detecting means and the steering angle target value of a steering control system, a correcting means correcting the deviation of the deviation calculating means based on the transfer characteristic having the low-pass characteristic, and a failure judging means judging the failure of the steering angle control system based on the correction value of the correcting means are provided. The deviation between the target steering angle and the actual steering angle is corrected by the correcting means based on the transfer characteristic having the low-pass characteristic in the failure detecting device of a vehicle steering angle control device, the failure judgment in the high-frequency area where control errors are easily generated is avoided, failure judgment is performed only in the low-frequency area, and correct failure judgment can be performed.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a failure detection device for a vehicle steering angle control system having a steering angle control system that controls the steering angle of either a front wheel or a rear wheel of a vehicle. In particular, it is possible to accurately detect failures in the steering angle control system without erroneously detecting them.

[Conventional technology]

As a failure detection device for this type of vehicle steering angle control device,
For example, there is one described in Japanese Utility Model Application Publication No. 1168366, which was previously proposed by the present applicant.

In this conventional example, the deviation θ6 is the absolute value of the difference between the actual rear wheel steering angle θ detected by the rear wheel steering angle sensor and the target steering angle θ8 calculated based on the steering angle detected by the steering angle sensor. This deviation Δθ is compared with a preset failure determination threshold α, and when the state of Δθ>α continues for a predetermined period of time, it is determined that there is an abnormality in the rear wheel steering angle control system.

[Problem to be solved by the invention]

However, in the conventional failure detection device for the vehicle steering angle control device, a failure occurs when the deviation between the target steering angle and the actual rear wheel steering angle, that is, the absolute value of the control error exceeds a certain predetermined value. Generally, even in normal conditions, the steering angle control system is more likely to produce control errors as the frequency components of the target steering angle and disturbances become higher, and when the target steering angle and disturbances are in the low frequency range. If the fault judgment value is set to a small value based on the characteristics, there is a risk that the steering angle control system may be mistakenly judged to be faulty even though it is normal in the high frequency operating range, and vice versa. There is an unresolved problem that increasing the fault detection value reduces the sensitivity of fault detection.

Therefore, the present invention has been made by focusing on the unresolved problems of the conventional example described above, and aims to avoid failure determination in the high frequency range where the steering angle control system is likely to cause control errors, and to ensure that the control errors are zero. The purpose of the present invention is to provide a failure detection device for a steering angle control system for a vehicle that can accurately determine failures in a steering angle control system by determining failures in a low frequency operating range that should be close to . There is.

[Means to solve the problem]

In order to achieve the above object, a failure detection device for a steering angle control device for a vehicle according to claim (1) is provided, as shown in the basic configuration diagram of FIG. In a vehicle steering angle control device having a steering angle control system for controlling a steering angle, a steering angle detecting means for detecting an actual steering angle, and an actual steering angle of the steering angle detecting means and a steering angle target of the steering angle control system are provided. a deviation calculation means for calculating a deviation from the value; and a correction means for correcting the deviation of the deviation calculation means based on a transfer characteristic having a low-pass characteristic.
The present invention is characterized by comprising a failure determination means for determining a failure of the steering angle control system based on the correction value of the correction means.

Further, in the failure detection device for a vehicle steering angle control system according to claim (2), the correcting means has a low-pass characteristic that corresponds to a normal steering angle target value of the steering angle control system to be detected as a failure. It is characterized in that it is set according to the transmission characteristics of the actual steering angle.

[Operation] In the failure detection device for a vehicle steering angle control device according to claim (1), the deviation between the target steering angle and the actual steering angle is corrected by the correcting means,
Since the correction is based on the transfer characteristic that has a low-pass characteristic, it is possible to avoid fault judgment in the high frequency range where control errors are likely to occur, and to make fault judgment only in the low frequency range. Failure can be determined.

Further, in the failure detection device for a steering angle control device for a vehicle according to claim (2), the low-pass characteristic of the correction means is the actual steering angle relative to the normal steering angle target value of the steering angle control system to be detected as the failure. Because it is set according to the angle transfer characteristics, the low-pass output is approximately zero when the steering angle control system is normal, and when the steering angle control system is abnormal and a steady deviation occurs. Therefore, an output corresponding to the deviation can be obtained, and the failure judgment means can more accurately judge the failure.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a schematic configuration diagram showing a first embodiment in which the present invention is applied to a rear wheel steering angle control system of a four-wheel steering vehicle.

In the figure, 1 is a rear wheel steering angle control system, and this rear wheel steering angle control system 1 includes a variable steering angle mechanism 3 that mechanically steers left and right rear wheels 2L and 2R, and a variable steering angle mechanism 3 that mechanically steers left and right rear wheels 2L and 2R. A control device 4 that drives and controls the mechanism 3 is provided.

The variable steering angle mechanism 3 has king pin shafts 6L and 6R between knuckle arms 5L and 5H attached to the left and right rear wheels 2L and 2H.
and tie rod 8 via ball joints 7L and 7R.
are connected to each other, and a sliding screw 9 formed on this tie rod 8 is connected to a nut 1o having external teeth formed on the outer peripheral surface.
is screwed together, and the step motor 1 is attached to the external teeth of this nut lO.
The gears 12 attached to the rotating shaft 1 are meshed with each other, and by rotationally driving the step motor 11,
The tie rod 8 moves in the left and right direction, and the rear wheels 2L and 2R are steered.

As shown in FIG. 3, the control device 4 includes a front wheel steering angle sensor 15 configured with a potentiometer connected to a front wheel tie rod, for example, that detects the steering angle δ of the front wheels, and a vehicle speed sensor 16 that detects the vehicle speed. , a rotary encoder 17 that outputs two types of pulses PA and P having a phase difference of 90 degrees depending on the rotation direction as a steering angle detection means for detecting the rotation angle of the drive motor 11, and this rotary encoder 1.
Pulses PA and PR outputted from 7 are input, and based on these two pulses, the rotation direction is discriminated to form an addition pulse and a subtraction pulse, and these are added and subtracted by an up/down counter to obtain the current motor rotation angle θ as a digital value. The current rotation angle measurement circuit 18 outputs the front wheel steering angle detection value δ1 output from the front wheel steering angle sensor 15, the vehicle speed detection value ■ output from the vehicle speed sensor 16, and the current rotation angle measurement circuit 18.
A microcomputer 20 receives the current motor rotation angle θ output from the microcomputer 20, and a rotation drive signal SI and a rotation direction signal S output from the microcomputer 20.
, , S3 and a motor drive circuit 21 to which the failure signal S4 is directly supplied.

Here, the microcomputer 20 has at least A/
Input interface circuit 20a, D having a D conversion function
/A conversion function output interface circuit 20b,
It is equipped with an arithmetic processing device 20c and a storage device 20d,
In the arithmetic processing unit 20c, the input/output interface circuit 20
Front wheel steering angle detection value δ1 of the front wheel steering angle sensor 15 via a.
Reads the vehicle speed detection value ■ of the vehicle speed sensor 16 and the current motor rotation angle θ of the current rotation angle measurement circuit 18, calculates the rear wheel steering angle target value δ7 based on the front wheel steering angle detection value δ1 and the vehicle speed detection value ■, This is converted into a target motor rotation angle σ, and PID control is performed based on the deviation ε between this target motor rotation angle and the current motor rotation angle θ to form a target drive current value, and this target drive current T is rotated. The rotation direction signal S is used as the drive signal S.
2. Along with S3, it is output from the output interface circuit 20b to the motor drive circuit 21, and a control error e, which is the deviation between the target motor rotation angle j and the current motor rotation angle θ, is calculated, and this control error e is subjected to low-pass filter processing. The absolute value of the filter output is compared with a preset failure determination threshold value f0 to determine a failure, and when a failure is determined, a failure signal S4 with a logic value of "1", for example, is sent to the motor drive circuit 21. output to the output and cut off its power supply.

Here, the rear wheel steering angle control system that drives the drive motor 11 to control the variable steering angle mechanism 3 is generally as shown in FIG.
Motor target rotation angle〃 and current rotation angle θ of the drive motor 11,
is supplied to the comparator 31, and the deviation ε calculated by the comparator 31 is supplied to the PID controller 32 and converted into a target current value, and this target current value is used as the drive current I in the motor drive circuit 21. This can be represented by a block diagram in which the steering angle δ of the rear wheels 2L and 2R is controlled by the variable steering angle mechanism 3 by the rotation of the drive motor 11.

The equation of motion of this rear wheel steering angle control system can be expressed by the following equation (1).

T-d=1.・S2θ ・・・・・・・・・
(1) Here, T is the drive torque of the drive motor 11, d is the cornering force, disturbance torque caused by road surface irregularities, etc., 11 is the drive motor rotor, and the variable steering angle mechanism 3.
The moment of inertia of a tire or the like around the motor axis, S is a differential operator, and θ is the current motor rotation angle.

Since the operation of the current control system by the motor drive circuit 21 is significantly faster than the operation of the drive motor 11, the PA
Since the target current ■ outputted from the D control section 32 and the drive current I outputted from the motor drive circuit 21 substantially match, the transfer characteristic between the target steering angle i and the actual steering angle i is as shown in (2) below.
It can be expressed by the formula.

In this equation (2), if the differential operator S is set to zero, the current motor rotation angle θ and the target motor rotation angle i will match. That is, the motor rotation angle θ is not affected by steady disturbances.

Also, the current motor rotation angle θ with respect to the target motor rotation angle
As shown in FIG. 5, the transmission characteristic has a low-pass characteristic, and from this FIG. 5, the frequency range of the target motor rotation angle θ is the cutoff frequency ω. When it is sufficiently lower than θ, the gain of the transfer characteristic is “1” and the phase delay is 0°, so θ
ζi, and the control error is very small, but the cutoff frequency ω.

In a higher frequency range, the gain decreases and the phase delay increases, so the control error e (-θ-i) of the current motor rotation angle θ with respect to the target motor rotation angle J increases. The power spectrum of this control error e is shown in FIG.

Therefore, as shown in FIG. 7, the control deviation e has a cutoff frequency of ω. By filtering with a low-pass filter, the filter output becomes a value that does not include the frequency range where the control error e becomes large, and becomes approximately zero when the rear wheel steering angle control system is normal, and the rear wheel steering angle control When an abnormality occurs in the system, a steady deviation will occur in the control error e, and the filter output will be set at a preset failure judgment threshold f0.
By comparing the results with the above, accurate failure judgment can be made.

Furthermore, the storage device 20d of the microcomputer 20 stores programs necessary for the arithmetic processing of the arithmetic processing unit 20c, and also stores a preset failure judgment threshold e.
0 is stored.

As shown in FIG. 8, the motor drive circuit 21 has a power input terminal 21a connected to a normally closed contact tA of a polarity switching relay 21c and a normally open contact 1B of a polarity switching relay 21d via a power supply relay 21b. The step motor 11 is connected between the movable contacts tc of the switching relays 21c and 21d, and the normally open contact tw of the polarity switching relay 21c and the normally closed contact tA of the polarity switching relay 21d are grounded via a power transistor 21e. has. here,
The power relay 21b is that relay coil! One end of b is grounded to the power supply terminal 21a, and the other end is grounded via a power transistor 21f, and a failure signal S4 output from the microcomputer 20 is supplied to the base of the power transistor 21f. Also, the relay coils of polarity switching relays 21c and 21d! , and ld are grounded at one end, and a rotation direction signal S2 output from the microcomputer 20 at the other end.
and S are supplied. Furthermore, power transistor 2
A pulse width modulation circuit 21g is connected to the base of 1e, and a microcomputer 20 is connected to this pulse width modulation circuit 21g.
The drive control signal S1 output from the drive control signal S1 is supplied, and
Current sensor 2 that detects the drive current of the step motor 11
The current detection value from 1h is supplied, and the pulse width modulation circuit 21g compares the current detection value of the current sensor 21h with the drive control signal SI, controls the duty ratio so that the two match, and forms a pulse signal. and supplies this to the power transistor 21e. Note that 21i is a flywheel diode that absorbs reverse polarity voltage.

Next, the operation of the above embodiment will be explained with reference to FIGS. 9 and 10 showing the processing procedure of the microcomputer 20.

FIG. 9 shows the steering angle control process for controlling the drive motor 11. First, in step (2), the front wheel steering angle detection value δ of the front wheel steering angle sensor 15 and the vehicle speed detection value V of the vehicle speed sensor 16 are read.

Next, proceeding to step (2), a target steering angle δ of the rear wheels is calculated based on the front wheel steering angle δ1 and the vehicle speed ■ read in step (2), and this is updated and stored in a predetermined storage area of the storage device 20d. do. The target steering angle δ of the rear wheels is determined by calculating the following equation (3) based on the vehicle speed ■, and calculating the rear wheel steering angle δ8 with respect to the front wheel steering angle δ so that the steady tank slip angle is zero.
The steering angle ratio K can be calculated by multiplying the steering angle ratio K by the front wheel steering angle δ.

Here, a is the distance between the front wheels and the center of gravity, b is the distance between the rear wheels and the center of gravity, l is the wheel base, CF and C11 are the front and rear wheel cornering powers, and M is the vehicle mass.

Therefore, as is clear from equation (3) above, the target rear wheel steering angle δ8 is such that the steering direction of the rear wheels is opposite to that of the front wheels so that the turning performance of the vehicle is improved when the vehicle speed is lower than the predetermined vehicle speed. direction and the vehicle speed exceeds the specified vehicle speed,
In order to improve the running stability of the vehicle, the steering direction of the rear wheels is set to be the same as that of the front wheels.

Next, the process moves to step (2), and a target motor rotation angle i of the drive motor 11 is calculated based on the target rear wheel steering angle δ8 calculated in the above step (2), and this is stored in a predetermined storage area of the storage device 20d for the past three times. Updates and stores the previous values while sequentially shifting them.

Next, the process moves to step ■, where the current rotation angle measurement circuit 1 is
The current motor rotation angle θ of the drive motor 11 stored in step 8 is read, and then the process moves to step 2, where the current motor rotation angle θ is subtracted from the target motor rotation angle l calculated in step 2, and the deviation ε between the two is calculated. After calculating , proceed to step ■.

In this step ■, in order to perform PID control, the deviation ε
Based on the following equation (4), a target current value (■) is calculated, and this is updated and stored in a predetermined storage area of the storage device 20d.

Here, K is a proportional gain, K2 is an integral gain, K3 is a differential gain, and S is a Laplace operator.

Next, the process moves to step (2), and it is determined whether or not the cut is to the left. This determination is based on the previous target motor rotation angle θf1
! -11 and the current target motor rotation angle 13 Both are set to the logical value "0", and then the step [phase] is started, and fl (Kl ≦ (9 (
When it is K-11, it is judged as a right cut and step ■
, and both the steering direction signals S2 and S3 are set to logical values '“.
1′” and then moves to step [phase].

In step [phase], the target current value T calculated in step (2) above is output to the motor drive circuit 21 as the drive control signal S1, and the steering direction signals S2 and S3 are output to the motor drive circuit 21, and then the step Return to ■.

In this way, the motor drive circuit 21 receives the drive control signal S1 and the steering direction signal S2. When S3 is input, when the steering direction signals SZ and S3 have a logical value of "0" (or a logical value of "1"), the polarity switching relays 21C and 21d cause their relay coils 2c and ! Since it is in the energized state (or energized state), the movable contact tc is switched to the normally closed contact tA (or normally open contact t8) side, and the drive motor 1
1 is in a state where a direct current of positive polarity (or reverse polarity) is input. In this state, a pulse signal with a duty ratio corresponding to the current value of the drive control signal S1 is supplied from the pulse width modulation circuit 21g to the base of the power transistor 21e, so that a pulse current corresponding to this pulse signal is applied to the drive motor 11. The drive motor 11 is driven to rotate forward (or reverse), the tie rod 8 moves to the right (or moves to the left), and the rear wheels 2L and 2R are steered to the left (or to the right). At this time, since the steering angle δ8 of the rear wheels 2L and 2R is proportional to the rotation angle θ of the drive motor 11, the steering angle δ3 is δ,=.

θ (K, is a constant determined by the gear ratio of the nut lO and the gear 12, the lead length of the slide screw 9, the lever ratio of the knuckle arms 5L, 5R, etc.).

Further, the arithmetic processing unit 20c performs a predetermined period of time, for example, 2Q@s
The failure determination process shown in FIG. 8 is executed by the timer interrupt process for each ec.

In this failure determination process, first, in step (2), the target motor rotation angle θ, which was stored in the step (2), is determined. The current motor rotation angle θ, which is stored in the current rotation angle measurement circuit 18, is read out and then the process moves to step @. is read and then moves to step 0.

In this step @, step Φ is calculated according to equation (5) below.
Current motor rotation angle θ, read in. Control the value obtained by subtracting the predicted target motor rotation angle value θfK) read in step ■ from ? 1111 error e (Kl) is updated and stored in the current control error storage area of the storage device 20d, and the previous control error e (K-11 is shifted to the previous control error storage area.

e(ni)-θfK)-θ(Kl...
・・・・・・・・・(5) Next, proceed to step @, and calculate the control error e (cutoff frequency ω of the rear wheel steering angle control system shown in FIG. 7 with respect to Kl. The following cantoff frequency is calculated. Perform first-order low-pass filter processing with the following (7)
The filter output F tx+ shown in the formula is calculated and updated and stored in the current filter output storage area of the storage device 20d, and the previous filter output F is calculated. -1, is shifted to the previous filter output storage area.

That is, the filter output F fKl can be expressed as (6)2.

Here, a is a constant, Z-1 is a delay operator, (1+a
r ) Z-'/(1+a r Z-1) is the transfer characteristic of a digital filter having a cutoff frequency less than or equal to the cutoff frequency ω0.

Therefore, from equation (6) above, the filter output F (K)
is F(Kl = at F(K-11+ (1+
ar) etx-n・・・・・・・・・・・・(
7) It can be calculated by performing the following calculation.

This filter output F (K) is F, when the rear wheel steering angle control system is normal. ζ. Then, F(.≠0) only when the rear wheel steering angle control system becomes abnormal and a steady deviation occurs in the control error e (K).

Next, the process moves to step [phase], and the absolute value IF() of the filter output F (K) calculated in the above step [phase].

The failure judgment threshold value f is set in advance. It is determined whether or not the value is greater than or equal to the value. This determination determines whether the rear wheel steering angle control system is in an abnormal state or in a normal state.
When l<f, it is determined that the rear wheel steering angle control system is in a normal state, and the process moves to step @, where a failure signal S4 with a logical value of "1" is sent to the motor drive circuit 21, and then the timer assignment is performed. IF,. When 1≧f0,
It is determined that the rear wheel steering angle control system is in an abnormal state where a failure has occurred, and the process moves to step @, where a failure signal S4 with a logical value of "O" is sent to the motor drive circuit 21, and then the timer interrupt processing is performed. end.

In this way, in the failure determination process, when the rear wheel steering angle control system is determined to be in a normal state, the failure signal S4 takes the logical value "1", and this is supplied to the motor drive circuit 21, so that the motor drive port 821 When the relay coil ! of the power supply relay 21b becomes energized and its normally open contact closes, a drive current is supplied to the drive motor 11.
Conversely, when the rear wheel steering angle control system is determined to be in a failure state,
As the failure signal S4 becomes the logic value Pa0'', '!!
Relay coil of relay 21b! , becomes de-energized and the normally open contacts open, thereby cutting off the supply of drive current to the drive motor 11 and stopping the drive of the drive motor.

Therefore, in the above failure determination process, the control error e between the target motor rotation angle i and the current motor rotation angle θ. The filter output F, which is processed by low-pass filtering. Since the failure of the rear wheel steering angle control system is determined by comparing ω with the failure determination threshold f0, the cutoff frequency ω of the rear wheel steering angle control system increases the control error. Control error e in the frequency range above
By attenuating TKI, the control error e (K
), failures are determined only in frequency ranges with few
Moreover, in this frequency range, when the rear wheel steering angle control system is in a normal state, the filter output F, ゎ becomes almost zero, and F,...
, <fo, and when the rear wheel steering angle control system is in an abnormal state, a steady deviation occurs in the control error e at that time, so that the filter output F. .

becomes a large value, F (K) ≧f0, and a failure in the rear wheel steering angle control system can be reliably detected.

In the above embodiment, a case has been described in which the failure judgment of the rear wheel steering angle control system is performed using the microcomputer 20. It can also be configured by combining circuits.

Further, in each of the above embodiments, a case has been described in which a failure determination is made in the rear wheel steering angle control system, but the present invention is not limited to this, and failure determination may be made in the front wheel steering angle control system. . In this case, the target motor rotation angle is determined by detecting the rotation angle of the steering wheel or the steering torque, and calculating the target motor rotation angle based on this.

Furthermore, in each of the above embodiments, as the steering angle detection means,
Row reencoder 17. Although the case where the motor rotation angle measuring circuit 18 is applied has been described, the movement amount of the tie rod 8 on the rear wheel side may be directly detected by a movement amount sensor such as a potentiometer.

[Effects of the Invention] As explained above, according to the failure detection device for a vehicle steering angle control device according to claim (1), the deviation between the target steering angle and the actual steering angle is calculated by the deviation calculation means, The calculation result is low-pass filtered by the correction means, and the filter output is compared with the fault judgment value to determine the failure of the rear wheel steering angle control system. Control errors are attenuated, and failures are determined only in the frequency range with few control errors, making it possible to determine failures in the steering angle control system with high sensitivity without causing erroneous judgments, regardless of the characteristics of the steering angle control system. You can get the effect you want.

Further, according to the failure detection device for a steering angle control device for a vehicle according to claim (2), the low-pass characteristic of the correction means is determined based on the actual steering angle target value in the normal state of the steering angle control system that is the object of failure detection. Since the setting is made according to the transmission characteristics of the steering angle, it is possible to reliably attenuate the frequency range above the cutoff frequency of the steering angle control system, which is likely to cause control errors, and to make more accurate failure judgments. I can do it.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram showing a schematic configuration of the present invention, Fig. 2 is a schematic configuration diagram showing an embodiment of the invention, Fig. 3 is a block diagram showing an example of a control device, and Fig. 4 is a rear wheel A block diagram of the steering angle control system. Figure 5 is a characteristic diagram showing the relationship between frequency and gain and phase in transfer characteristics. Figure 6 is a characteristic diagram showing the power spectrum of control error. Figure 7 is a characteristic diagram showing the relationship between frequency and gain and phase in transfer characteristics. A characteristic diagram showing the relationship between the frequency and gain of the band pass filter, Fig. 8 is a block diagram showing the motor drive circuit, Fig. 9 is a flowchart showing an example of steering angle control processing, and Fig. 10 is a flowchart showing an example of the steering angle control processing. It is a flowchart which shows an example. In the figure, 1 is a rear wheel steering angle control system, 2L and 2R are rear wheels, 3 is a variable steering angle mechanism, 4 is a control device, 8 is a tie rod, 11 is a drive motor, 15 is a front wheel steering angle sensor, and 16 is a vehicle speed sensor,
17 is a rotary encoder, 18 is a current rotation angle measuring circuit, 20 is a microcomputer, and 21 is a motor drive circuit. Figure 2 3! e-Kamitsu 1-Tsuru Figure 8 Figure 9

Claims (2)

[Claims] (1) In a vehicle steering angle control device having a steering angle control system that controls the steering angle of either a front wheel or a rear wheel of a vehicle, a steering angle detecting means for detecting an actual steering angle, and the steering angle detecting means a deviation calculation means for calculating the deviation between the actual steering angle of the steering angle and a steering angle target value of the steering angle control system; and a correction means for correcting the deviation of the deviation calculation means based on a transmission characteristic having a low-pass characteristic. A failure detection device for a steering angle control device for a vehicle, comprising failure determination means for determining failure of the steering angle control system based on a correction value of the correction means. (2) Claim (1), wherein the correction means has a low-pass characteristic set in accordance with a transfer characteristic of the actual steering angle with respect to a steering angle target value in a normal state of the steering angle control system that is subject to failure detection. A failure detection device for the vehicle steering angle control device described above.