JPH0774001B2 - Detection front wheel steering angle correction device - Google Patents

Description

The present invention relates to a detected front wheel steering angle correction for correcting a detected front wheel steering angle detected by a front wheel steering angle sensor incorporated in a front wheel steering system such as a steering shaft. Regarding the device.

[Prior art]

Conventionally, using the detected front wheel steering angle detected by the front wheel steering angle sensor assembled to the front wheel steering system such as the steering shaft,
A device for controlling various states of a vehicle is well known, and for example, in Japanese Patent Laid-Open No. 57-44568, a device is mounted on a steering shaft to detect a front-wheel steering angle, and in response to a signal from a front-wheel steering angle sensor. A device for controlling the steering state of the rear wheels is shown.

[Problems to be solved by the invention]

However, in any of the above conventional devices,
Detection by the front wheel steering angle sensor Since the front wheel steering angle is used as it is to control various states of the vehicle, there are errors in mounting the front wheel steering angle sensor on the front wheel steering system, wheel alignment adjustment errors, tire changes over time, and steering wheel changes. The sensor connected to the tire changes over time, the vehicle body and chassis are deformed by impact, the temperature around the front wheel steering angle sensor changes, the voltage supplied to the sensor changes, and the sensor itself changes over time. If the zero point of is shifted, the accuracy of the detected front wheel steering angle becomes poor and the control of the various states described above cannot be performed well.

The present invention was devised to address the above problems,
The purpose is to correct the detected front wheel steering angle detected by the front wheel steering angle sensor on the basis of the learning correction value learned from the above-mentioned zero deviation state, and thereby the front wheel steering used for the control of the above various states. An object of the present invention is to provide a detection front wheel steering angle correction device that maintains good corner accuracy.

[Means for solving problems]

In order to solve such a problem and achieve the above object, the structural feature of the present invention is, as shown in FIG. 1, a detection front wheel steering for correcting the detected front wheel steering angle detected by the front wheel steering angle sensor 1. An angle correction device, a sampling means 2 for sequentially sampling the detected front wheel steering angle detected by the front wheel steering angle sensor 1, and a reference value storage means 3 for storing a reference value corresponding to a zero point of the detected front wheel steering angle. The vehicle speed detection means 4a for detecting the vehicle speed, the yaw rate detection means 4b for detecting the yaw rate of the vehicle, and the vehicle in a straight traveling state on condition that the detected vehicle speed is higher than a predetermined value and the detected yaw rate is substantially zero. Judgment means 4c for judging that there is
And an accumulating means for accumulating a value corresponding to a deviation amount of the sampled detected front wheel steering angle with respect to the reference value when the straight traveling state of the vehicle is judged by the judging means 4c for each predetermined sampling time. 5, reference value updating means 6 for updating the reference value by adding the accumulated result to the reference value, and correction front wheel for detecting the front wheel steering angle by adding the updated reference value to the detected front wheel. And the correction calculation means 7 for correcting the steering angle.

[Operation of the invention]

In the present invention configured as described above, the sampling means 2 samples the detected front wheel steering angle detected by the front wheel steering angle sensor 1, and the vehicle speed detected by the vehicle speed detecting means 4a is greater than a predetermined value and the yaw rate detecting means. 4b
When the judging means 4c judges that the vehicle is in a straight traveling state on the condition that the yaw rate detected by the above is approximately zero, the accumulating means 5 stores the sampled front wheel steering angle and the reference value storing means 3 The stored deviation amount from the reference value corresponding to the zero point of the detected front wheel steering angle is accumulated for a predetermined time at each sampling timing. In this case, if the vehicle is in a straight traveling state, the front wheel steering angle of the vehicle is essentially zero, and the deviation from the reference value corresponding to the zero point of the detected front wheel steering angle causes a detection error regarding the zero point of the front wheel steering angle. Therefore, the accumulated result indicates the zero point correction value of the detected front wheel steering angle obtained by learning the occurrence state of the detection error regarding the zero point of the front wheel steering angle sensor 1 within the predetermined time.

Then, the reference value updating means 6 updates the reference value by adding the accumulated result indicating the zero point correction value to the reference value corresponding to the zero point stored in the reference value storage means 3, The reference value is corrected every predetermined time and indicates the zero point correction value of the detected front wheel steering angle, which is obtained by learning the occurrence state of the detection error regarding the zero point of the front wheel steering angle sensor 1 for a long time. The reference value indicating such a zero-point correction value is used by the correction calculation of the correction calculation means 7, and the correction calculation means 7 calculates the corrected detected front wheel steering angle by correcting the detected front wheel steering angle based on the reference value.

〔The invention's effect〕

As can be understood from the above description of the operation, according to the present invention,
Even if the zero point of the front wheel steering angle detected by the front wheel steering angle sensor 1 deviates due to the reasons listed in the section [Problems to be Solved by the Invention], the occurrence state of this zero point deviation is learned and the learning result is obtained. Since the detected front wheel steering angle is corrected on the basis of the above, the accuracy of the corrected detected front wheel steering angle is always kept good. Then, by utilizing the corrected detected front wheel steering angle for controlling various states of the vehicle, the control can be performed well.

Further, according to the present invention, expensive tires, linkages, and parts of the front wheel steering angle sensor 1 itself, which do not change with time and do not require high-precision mounting and high-precision wheel alignment adjustment of the front-wheel steering angle sensor 1, themselves. Since the deviation of the detected front wheel steering angle from the zero point is corrected by an electronic circuit such as a micro computer without adopting an expensive circuit that prevents or compensates for temperature changes and voltage fluctuations, etc. The precision of the front-wheel steering angle used for the control of is realized by an inexpensive device. As a result, the vehicle manufacturing cost is reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 schematically shows a front and rear wheel steering vehicle to which a detected yaw rate correction device according to the present invention is applied. This front and rear wheel steering vehicle includes a front wheel steering device 20 for steering the left and right front wheels 10a, 10b,
A rear wheel steering device 30 that steers the left and right rear wheels 11a and 11b, and an electric control device 40 that controls the rear wheel steering device 30 are provided.

The front wheel steering device 20 includes a steering shaft 22 connected to a steering wheel 21.
22a fixed to the lower end of the pinion and this pinion 22a
A relay rod 23 having a rack tooth 23a that meshes with the relay rod 23 is provided, and the relay rod 23 is displaced in the axial direction according to the rotation of the steering handle 21. The displacement of the relay rod 23 is transmitted to the left and right tie rods 24a and 24b connected to both ends of the rod 23, and the left and right knuckle arms 25a and 25b are oscillated by the swing of the left and right tie rods 24a and 24b based on the displacement.
Is rotated so that the left and right front wheels 10a, 10b are steered. Further, a power steering switching valve 26 is attached to an intermediate portion of the steering shaft 22, and the switching valve 26 receives high pressure oil from a hydraulic pump 27b driven by an electric motor 27a according to the rotation of the steering shaft 22. Is supplied to one oil chamber of the power cylinder 28 accommodating the piston 28a fixed to the relay rod 23, and the oil return from the other oil chamber of the cylinder 28 to the reservoir 27c is allowed. The power cylinder 28 supplies the high pressure oil to the piston 28a and the relay rod 23.
Is displaced in the axial direction of the rod 23 to assist steering of the left and right front wheels 10a, 10b according to the rotation of the steering handle 21.

The rear wheel steering device 30 meshes with an electric motor 31 whose rotation is controlled by an electric control device 40, a pinion 32a fixed to the rear end of a rear wheel steering shaft 32 which is rotationally driven by the motor 31, and this pinion 32a. Relay rod with rack teeth 33a
33 has a relay rod 33 according to the rotation of the electric motor 31.
Is displaced in the axial direction. The displacement of the relay rod 33 is transmitted to the left and right tie rods 34a and 34b connected to both ends of the relay rod 33, and the left and right knuckle arms 35 are oscillated by the swing of the left and right tie rods 34a and 34b based on the displacement.
The a and 35b are rotated so that the left and right rear wheels 11a and 11b are steered. In addition, the rear wheel steering system 30 includes a power steering switching valve 36 installed in the middle portion of the rear wheel steering shaft 32.
And a power cylinder 37 accommodating a piston 37a fixed to the relay rod 33, and by the same switching valve 36 and the same cylinder 37, as in the case of the front wheel steering device 20, left and right rear by rotation of the electric motor 31. The steering of the wheels 11a and 11b is assisted. The switching valve 36 is connected to a hydraulic pump 38b that is driven by an electric motor 38a and supplies high-pressure oil to the switching valve 36, and a reservoir 38c that stores oil from the switching valve 36.

The electric control device 40 includes a front wheel steering angle sensor 41, a vehicle speed sensor 42, a yaw rate sensor 43, a rear wheel steering angle sensor 44, and a microcomputer 45. The front wheel steering angle sensor 41 is an angle sensor that is attached to the steering shaft 22 and detects a rotation angle of the coaxial shaft 22 from a reference position. The front wheel steering angle sensor 41 outputs a front wheel steering angle signal indicating a front wheel steering angle A corresponding to the detected rotation angle. Supply to the computer 45. In this case, the front wheel steering angle A is expressed as zero when the left and right front wheels 10a, 10b are in a straight traveling state, and the front wheel steering angle A is negative (or right) when the left and right front wheels 10a, 10b are steered leftward (or rightward). Positive) value. The vehicle speed sensor 42 is composed of a rotation sensor that detects the rotation of the output shaft of the transmission, and supplies a vehicle speed signal having a frequency proportional to the vehicle speed V to the microcomputer 45. The yaw rate sensor 43 is an angular velocity sensor that is mounted on the vehicle body and detects a yawing angular velocity of the vehicle, and supplies a yaw rate signal representing a yaw rate Y corresponding to the detected angular velocity to the microcomputer 45. Rear wheel steering angle sensor
Reference numeral 44 denotes an angle sensor that is mounted on the rear wheel steering shaft 32 and detects a rotation angle of the coaxial shaft 32 from a reference position, and outputs a rear wheel steering angle signal indicating a rear wheel steering angle θr corresponding to the detected rotation angle to a micro signal. Supply to the computer 45. Also in this case, like the front wheel steering angle A, the rear wheel steering angle θr is expressed as zero when the left and right rear wheels 11a, 11b are in a straight traveling state, and the left and right rear wheels 11a, 11b are represented.
When b is steered to the left (or to the right), the rear wheel steering angle θr is expressed as a negative (or positive) value. In the present embodiment, the front wheel steering angle sensor 41
And the rear-wheel steering angle sensor 44 to the steering shaft 22 and the rear-wheel steering shaft, respectively.
Although the sensors 41 and 44 are provided in the middle portion of 32, the tip end portions of the respective steering shafts 22 and 32 are extended (broken line portions 41a and 41a in FIG. 2).
It may be provided in the. In addition, each of these sensors 4
Each of the relay rods 1 and 44 is composed of position sensors 41b and 44b (broken lines in FIG. 2) that detect a linear displacement amount.
The front wheel steering angle A and the rear wheel steering angle θr may be detected by detecting the axial displacement amounts of 3, 33.

The microcomputer 45 includes a program memory 45a, a central processing unit (hereinafter referred to as CPU) 45b, a working memory 45c, a first timer circuit 45d, a second timer circuit 45e, and a steering angle ratio table 45.
f and an input / output interface (hereinafter referred to as I / O) 45g, and these respective circuits 45a to 45g are commonly connected to a bus 45h. The program memory 45a is composed of a read-only memory (ROM), and has an "initial setting" program corresponding to the flowcharts of FIGS.
A “zero point correction value calculation” program and a “rear wheel steering control” program are stored. The CPU 45b executes the "initial setting" program when the ignition switch (not shown) is closed, and at each arrival of each first and second interrupt signal from the first and second timer circuits 45d and 45e described later. The "zero point correction value calculation" program and the "rear wheel steering control" program are executed. The working memory 45c is composed of a writable memory (RAM), and temporarily stores data representing variables and flags necessary for executing the programs. The main ones of these variables and flags are listed below.

Detected vehicle speed V ... Represents the traveling speed of the vehicle detected by the vehicle speed sensor 42.

Detected yaw rate Y ... Indicates the yaw rate of the vehicle detected by the yaw rate sensor 43.

Yaw rate zero point correction value Yo ... Represents a correction value for correcting the deviation of the zero point of the detected yaw rate Y.

Corrected detection yaw rate Y * ... Represents a value obtained by correcting the detected yaw rate Y with a yaw rate zero point correction value Yo.

Detected yaw rate zero point error ΔYo ... In order to calculate the yaw rate zero point correction value Yo, it represents the accumulated value of the deviation of the detected yaw rate Y from the zero point when the detected yaw rate Y should originally be zero.

Yaw rate zero point correction sample value Ny: To calculate the yaw rate zero point correction value Yo, the detected yaw rate zero point error Δ
It represents the number of samples of the detected yaw rate Y accumulated as Yo.

Yaw rate zero point correction timer value Ty ・ ・ ・ Detected yaw rate zero point error ΔYo to calculate yaw rate zero point correction value Yo
Represents the elapsed time from the start of accumulation.

Flag for detecting yaw rate sensor failure WFy: To detect a failure of the yaw rate sensor 43, "1" represents a state in which the detected yaw rate Y shows an abnormal value, and "0" represents the detected yaw rate Y is normal. Represents a state that indicates a value.

Count value Wty for detecting yaw rate sensor failure ... Indicates the elapsed time from when the detected yaw rate Y begins to show an abnormal value in order to detect the failure of the yaw rate sensor 43.

Detected front wheel steering angle A: Indicates the steering angle of the left and right front wheels 10a, 10b detected by the front wheel steering angle sensor 41.

Front wheel steering angle zero correction value Ao ... Represents a correction value for correcting the deviation of the zero point of the detected front wheel steering angle A.

Corrected detected front wheel steering angle A * ... Indicates a value obtained by correcting the detected front wheel steering angle A with a front wheel steering angle zero correction value Ao.

Detected front wheel steering angle zero point error ΔAo: To calculate the front wheel steering angle zero correction value Ao, the accumulated value of the deviation of the detected front wheel steering angle A from the zero point should be calculated when the detected front wheel steering angle A should be zero. Represent

Front wheel steering angle zero point correction sample value Na ・ ・ ・ Detected front wheel steering angle zero point error Δ to calculate front wheel steering angle zero point correction value Ao
The number of samples of the detected front wheel steering angle A accumulated as Ao is shown.

Front wheel steering angle zero correction timer value Ta ... To calculate the front wheel steering angle zero correction value Ao, the detected front wheel steering angle zero error ΔAo
Represents the elapsed time from the start of accumulation.

Front wheel steering angle sensor failure detection flag WFa ... In order to detect a failure of the front wheel steering angle sensor 41, "1" represents a state where the detected front wheel steering angle A shows an abnormal value, and "0" The detected front wheel steering angle A indicates a normal value.

Front wheel steering angle sensor failure detection count value WTa ... Indicates the elapsed time from when the detected front wheel steering angle A starts to show an abnormal value in order to detect the failure of the front wheel steering angle sensor 41.

Detected rear wheel steering angle θr: represents the steering angle of the left and right rear wheels 11a and 11b detected by the rear wheel steering angle sensor 44.

Target rear wheel steering angle θr * represents the steering angle at which the left and right rear wheels 11a, 11b should be steered.

Failure flag OUTFLG ... "1" indicates a failure state of the front wheel steering angle sensor 41 or yaw rate sensor 43, and "0" indicates a normal state of each of the sensors 41, 43.

The first and second timer circuits 45d and 45e are respectively initialized by the processing of the "initialization" program, and thereafter, the first timer circuit 45d causes the first interrupt signal at every first predetermined time (for example, about 10 milliseconds). Is output to the CPU 45b. The second timer circuit 45e outputs a second interrupt signal to the CPU 45b every second predetermined time (for example, several tens of milliseconds to several hundreds of milliseconds). The steering angle ratio table 45f is composed of a read-only memory (ROM),
The vehicle speed-corresponding steering angle ratio K1 (V), which has a characteristic that gradually changes from negative to positive in response to an increase in vehicle speed V as shown in FIG. 6, is stored in the form of a map with respect to the vehicle speed V. Note that when the steering angle ratio K1 (V) corresponding to the vehicle speed is negative, the left and right rear wheels 11a, 11b are the left and right front wheels 10a, 10b.
Is meant that the steering control is performed in the opposite phase, and that the vehicle speed corresponding steering angle ratio K1 (V) is positive that the left and right rear wheels 11a, 11b are steered in phase with the left and right front wheels 10a, 10b. Means I
/ O45g is connected to each sensor 41-44.
Each detection signal supplied from ~ 44 is converted into a digital format signal suitable for program processing by CPU45b, and
5b or working memory 45c is supplied via bus 45h. Further, the I / O 45g has a built-in digital-analog converter (D / A converter), and is a digital signal representing the steering amount of the left and right rear wheels 11a, 11b determined by the program processing of the CPU 45b, that is, the rotation amount of the electric motor 31. The data is converted into an analog signal and supplied to the power amplifier 46. Power Amplifier
46 drives and controls the electric motor 31 based on the analog signal. Further, a warning lamp 47 provided near the driver's seat is connected to the I / O 45g.

The operation of the above embodiment will be described below with reference to the flow charts of FIGS. 3 to 5. Before describing the program processing operations corresponding to these floatates in detail, the program processing operations will be outlined. To explain.

When the ignition switch (not shown) is closed, the CPU 45b executes the "initial setting" program (FIG. 3) including steps 100 to 103. The "initial setting" program is executed only once immediately after the ignition switch is closed, and is not executed unless the ignition switch is closed again after the engine is stopped.
By executing this "initial setting" program, the first timer circuits 45d and 45e are initialized, and thereafter the first and second timer circuits 45d and 45e are set to the first and second predetermined time intervals.
Start outputting interrupt signals to the CPU 45b. Due to the arrival of the first and second interrupt signals, the CPU 45b causes the "zero point correction value calculation" program (FIG. 4) consisting of steps numbered 200 to 200 and the "rear wheel steering control" program consisting of steps 300 to 306. (Fig. 5) is executed respectively. In this case, since the first interrupt signal is generated every first predetermined time (about 10 milliseconds), the "zero point correction value calculation" program is repeatedly executed every first predetermined time. Since the second interrupt signal is generated every second predetermined time (several tens of milliseconds to several hundreds of millimeters), the "rear wheel steering control" program is repeatedly executed every second predetermined time.

The "zero point correction value calculation" program is a "yaw rate zero point correction value calculation" routine, a "yaw rate sensor failure detection" routine, a "fault detection processing" routine, a "front wheel steering angle zero point correction value calculation" routine, and a "front wheel steering angle sensor failure detection". It consists of a routine. As shown in FIG. 4, the "yaw rate zero point correction value calculation" routine is composed of steps 210 to 217. The CPU 45b calculates the yaw rate zero point correction value Yo by repeating the routine every first predetermined time. The value Yo is stored in the working memory 45c. The “Yaw rate sensor failure detection” routine consists of steps 220 to 223, and the CPU4
5b detects a failure of the yaw rate sensor 43 by repeating the same routine every first predetermined time. The "fault detection process" routine is composed of steps 230 to 232, and the CPU 45b performs the process associated with the fault detection of the "yaw rate sensor fault detection" routine and the fault detection of the "front wheel steering angle sensor fault detection" routine described later in the same routine. Perform the accompanying processing. The "front wheel steering angle zero point correction value calculation" routine is a step
The CPU 45b is composed of 240 to 248 and calculates the front wheel steering angle zero correction value Ao by repeating the same routine every first predetermined time and stores the value Ao in the working memory 45c. The "front wheel steering angle sensor failure detection" routine is steps 250 to 253.
The CPU 45b detects a failure of the front wheel steering angle sensor 41 by repeating the same routine every first predetermined time.

Further, in the "rear wheel steering control" program (FIG. 5) which is repeatedly executed every second predetermined time, the CPU 45b sets the detected yaw rate Y and the detected front wheel steering angle A to the both zero correction values Yo and Ao, respectively. Based on the corrected detected yaw rate Y * and the corrected detected front wheel steering angle A * and the vehicle speed corresponding steering angle ratio K1 (V) stored in the steering angle ratio table 45f, the target rear wheel steering angle θr * is corrected. After the calculation, the left and right rear wheels 11a and 11b are controlled to the same steering angle θr *.

Next, the processing of each program and each routine described above will be described in detail.

(1) Regarding the "initial setting" program When the ignition switch is closed as described above, the CPU 45b starts executing this program from step 100 and clears the working memory 45c at step 101 to clear all variables. And set flags to initial values. After the processing of step 101, the CPU 45b sets the first and second timer circuits 45d and 45e to the operable state in step 102 and, at the same time, sets the first timer circuit 45d to the first predetermined time (Equation 1).
The second timer circuit 45e is set to generate the first interrupt signal every 0 milliseconds) and the second timer circuit 45e generates the second interrupt signal every second predetermined time (several tens of milliseconds to several hundreds of milliseconds). Is set and the execution of this program ends in step 103. By the setting process in step 102, the first and second timer circuits 45d and 45e thereafter output the first and second interrupt signals to the CPU 45b at the first and second predetermined times, respectively.

(2) Regarding "Yaw rate zero point correction value calculation" routine This routine calculates the deviation of the detected yaw rate Y from the zero point based on the fact that the yaw rate of the vehicle is essentially zero when the vehicle is in a stopped state or a substantially stopped state. The yaw rate zero point correction value Yo is calculated by accumulating, and every time the first timer circuit 45d generates the first interrupt signal to the CPU 45b, the CPU 45b causes the vehicle to be in a stopped state or a substantially stopped state. Under this condition, the processing of this routine is repeatedly executed to calculate the yaw rate zero point correction value Yo.

That is, upon arrival of the first interrupt signal, the CPU 45b starts executing the "zero-point correction value calculation" program from step 200 of FIG. 4, and from the vehicle speed sensor 42 to I / O at step 210.
The vehicle speed V is calculated based on the vehicle speed signal input via 45g, and the absolute value | V | of the calculated detected vehicle speed V is compared with the first predetermined vehicle speed α. The first predetermined vehicle speed α is set to about 3 kilometers / hour in order to detect the stopped state or the substantially stopped state of the vehicle. If the vehicle is in the stopped state or the substantially stopped state, the CPU 45b at the same step 210 YES ", that is, the absolute value | V | is determined to be less than the first predetermined vehicle speed α,
Program proceeds to step 211. The CPU 45b uses the detected front wheel steering angle zero point error ΔAo and the front wheel steering angle zero point correction sample that are used to calculate the front wheel steering angle zero point correction value Ao in the processing of the “front wheel steering angle zero point correction value calculation” routine in step 211. Value Na and timer value for front wheel steering angle zero correction
Set Ta to “0” and set yaw rate sensor 4 in step 212.
The absolute value | Y−Yo | of the difference between the detected yaw rate Y represented by the yaw rate signal input from 3 through the I / O 45g and the yaw rate zero correction value Yo is compared with the predetermined yaw rate γ. This predetermined yaw rate γ is set to a small value of about 1 degree / second, and if the yaw rate sensor 43 is operating normally, the detected yaw rate Y includes a slight error (detected yaw rate zero point error ΔYo), but the yaw rate zero point. Correction value Yo
Therefore, the CPU 45b determines “YES” in step 212, that is, the absolute value | Y−Yo | is the predetermined yaw rate γ.
If so, the program proceeds to step 213. If the absolute value | Y−Yo | is greater than or equal to the predetermined yaw rate γ, the CPU 45b determines “NO” in step 212, that is, the detected yaw rate Y indicates an abnormal value, and executes the program in step 220. And proceeds to the execution of the "yaw rate sensor failure detection" routine processing.

After determining "YES" in step 212, the CPU 45b determines in step 213 that the yaw rate sensor failure detection flag WFy and the yaw rate sensor are used for the failure detection process of the yaw rate sensor 43 in the "yaw rate sensor failure detection" routine. The failure detection count value WTy is "0".
Set to. Next, the CPU 45b detects the detected yaw rate for each of the detected yaw rate zero point error ΔYo, the yaw rate zero point correction sample value Ny, and the yaw rate zero point correction timer value Ty which have been set to “0” as initial values in step 214. By adding the difference Y−Yo between Y and the yaw rate zero correction value Yo, the value “1”, and the predetermined time value Δt of about 10 milliseconds, which is equal to the generation interval of the first interrupt signal, each value ΔY
Update o, Ny, and Ty respectively. By this update, each value ΔY
o, Ny and Ty are respectively set to the difference Y-Yo, "1" and Δt. After the processing of step 214, the CPU 45b causes the step 215
At, the yaw rate zero point correction timer value Ty is compared with a predetermined time value Tyo preset for about 5 seconds. In this comparison, the set timer value Ty is the predetermined time value Ty.
Since it is not greater than or equal to o, the CPU 45b determines “NO”, and ends the execution of this “zero point correction value calculation” program in step 201.

After this end, when the first predetermined time (about 10 milliseconds) has elapsed, the first timer circuit 45d again sends the first interrupt signal to the CPU 45b.
Then, the CPU 45b starts execution of the "zero-point correction value calculation" program from step 200 as in the above case. Then, as in the case described above, if the vehicle is in a stopped state or a substantially stopped state and the detected yaw rate Y is close to the yaw rate zero correction value Yo, the CPU 45b determines “YES” in steps 210 and 212, respectively. In step 214, the zero-point error ΔYo is updated by adding the difference Y−Yo between the new detected yaw rate Y and the yaw rate zero-point correction value Yo to the detected yaw rate zero-point error ΔYo, and the yaw rate zero-point correction sample value Ny and By adding the value “1” and the predetermined time value Δt to the yaw rate zero correction timer value Ty,
Update Ny and Ty to “2”, 2 · Δt, respectively. After this update, C
The PU 45b sends Ty (= 2) in step 215 as in the above case.
Based on the relationship of Δt) <Tyo, “NO” is determined and the execution of the “zero point correction value calculation” program is ended in step 201.

Then, when the first predetermined time (about 10 milliseconds) has elapsed again, the CPU 45b restarts the execution of the "zero-point correction value calculation" program from step 200, and the vehicle and the detected yaw rate Y
Unless the above state changes, the processing of steps 210 to 215 is performed, and the execution of the program is ended in step 201. In this way, as a result of the process of step 214 being repeatedly executed at every first predetermined time, the detected yaw rate zero point error ΔYo becomes a value obtained by accumulating the error of the detected yaw rate Y from the yaw rate zero point correction value Yo, while the yaw rate Zero-correction sample value Ny and yaw rate zero-correction timer value Ty
Increases every first predetermined time. And the repetition is
At about 500 times, the timer value Ty becomes equal to or greater than the predetermined time value Tyo (about 5 seconds). At this time, the CPU 45b determines “YES” in the comparison in step 215, and adds the value ΔYo / Ny obtained by dividing the same zero point error ΔYo by the same sample value Ny to the yaw rate zero correction value Yo in step 216. Correction value Yo
To update. In this case, the same sample value Ny is the same zero point error Δ
Since it is equal to the cumulative number of times Yo, the value ΔYo / Ny is the average value obtained by sampling the deviation of the detected yaw rate Y from the yaw rate zero point correction value Yo over about 5 seconds, and the zero point correction value Yo is corrected by this average value. Will be. After the processing of step 216, the CPU 45b at step 217 prepares the detected yaw rate zero point error ΔYo, the yaw rate zero point correction sample value Ny, and the yaw rate zero point correction timer value Ty in preparation for the next update of the yaw rate zero point correction value Yo. Each is initially set to "0", and the execution of this "zero point correction value calculation" program is ended in step 201. Further, if the vehicle continues to be in a stopped state or a substantially stopped state and the detected yaw rate Y is close to the yaw rate zero point correction value Yo, the CPU 45b performs the "yaw rate zero point correction value calculation" including the above steps 210 to 217. The routine is repeatedly executed, and the yaw rate zero point correction value Yo is updated about every 5 seconds.

As can be understood from the above description, the deviation of the detected yaw rate Y sampled about every 10 milliseconds from the yaw rate zero correction value Yo is accumulated as the detected yaw rate zero point error ΔYo over about 5 seconds. Since the error ΔYo is averaged with the sampling ring value Ny equal to the cumulative number, the value ΔYo / Ny is less affected by the sampling error per one time. This value ΔYo / Ny is added to the yaw rate zero point correction value Yo about every 5 seconds to obtain the zero point correction value Yo.
Is corrected, the same zero point correction value Yo becomes a learned value of the deviation of the yaw rate Y detected by the yaw rate sensor 43 from the zero point for a long time, and the accuracy of the same zero point correction value Yo is improved.

In the "yaw rate zero point correction value calculation" routine, the yaw rate zero point correction timer value Ty and the predetermined time Ty
By comparing o with step 215, detection is performed for a predetermined time (about 5 seconds).
Since it is executed every 10 milliseconds, by comparing in step 215 whether or not the sample value Ny for yaw rate zero point correction is about 500 or more, it is possible to detect for a predetermined time (about 5 seconds). Good.

(3) Regarding "Yaw rate sensor failure detection" routine This routine is based on the fact that the yaw rate of the vehicle is essentially zero when the vehicle is in a stopped state or a substantially stopped state. And to detect a failure of the yaw rate sensor 43 by detecting a large deviation from the zero point,
The CPU 45b repeatedly executes the processing of this routine to detect the failure of the yaw rate sensor 43 on condition that the vehicle is in the stopped state or the substantially stopped state and the detected yaw rate Y is largely deviated from the zero point.

That is, upon arrival of the first interrupt signal, the CPU 45b starts the execution of the zero point correction value calculation program from step 200, and after the processing of steps 210 and 211 similar to the case of the above (2), from the yaw rate sensor 43 in step 212. Absolute value of difference between detected yaw rate Y represented by yaw rate signal input via I / O 45g and yaw rate zero correction value Yo | Y−
Yo | is compared with a predetermined yaw rate γ. In this case, the detected yaw rate Y is largely deviated from the yaw rate zero point correction value Yo, so in the comparison of step 212, the CPU 45b
Is “NO”, that is, the absolute value | Y−Yo | is not less than the predetermined yaw rate γ (about 1 degree / second), and the program proceeds to step 220. In step 220, first, the yaw rate sensor failure detection flag WFy is set to "0" by the processing of step 101 (FIG. 3) of the "initial setting" program or step 213 of the "yaw rate zero point correction value calculation" routine. Therefore, the CPU 45b determines “NO”, that is, the flag WFy is not “1”. After this determination, the CPU 45b sets the flag WFy to "1" in step 221 and sets the yaw rate sensor failure detection count value.
WTy is set to "1", and in step 223, the set same count value WTy is compared with the predetermined value P. In this case, since the predetermined value P is preset to "50", the CPU 45b determines "NO" in the same step 223, that is, the same count value WTy is not greater than or equal to the predetermined value P, and in step 217 the above ( The same processing as in the case of 2) is performed, and the execution of this “zero point correction value calculation” program is ended in step 201.

After this end, when the first predetermined time (about 10 milliseconds) elapses, the first timer circuit 45d outputs the first interrupt signal to the CPU 45b again as in the case of (2) above, and the CPU 45b outputs the same signal as in the above case. Similarly, the execution of the “zero point correction value calculation” program is started from step 200. Then, as in the above case, if the vehicle is still in the stopped state or the substantially stopped state and the detected yaw rate Y is largely deviated from the yaw rate zero point correction value Yo, the CPU 45b determines "YE
If it is determined to be “S” or “NO”, the program proceeds to step 220. In this case, the yaw rate sensor failure detection flag WF
Since y is set to "1" by the processing of the above step 221, the CPU 45b determines "YES" in the same step 220, and is set to "1" by the processing of the above step 221 in step 222. Count value WT for yaw rate sensor failure detection
The count value WTy is set to "2" by adding "1" to y. After the processing of step 222, CPU45b
Determines in step 223 to be “NO” based on the relationship of WTy (= 2) <P (= 50), and through the process of step 217,
In step 201, the execution of this "zero point correction value calculation" program is terminated.

Then, when the first predetermined time (about 10 milliseconds) elapses again, the CPU 45b starts executing the "zero-point correction value calculation" program from step 200, and unless the above-described states of the vehicle and the detected yaw rate Y change, step 210 ~ 212,220,222,2
After the processing of 23,217, the execution of the same program is ended in step 201. In this way, the process of step 222 is repeatedly executed every first predetermined time, and the yaw rate sensor failure detection count value WTy sequentially increases by "1". When the count value WTy reaches “50” due to this increase, the CPU 45b determines “YES” in step 223, that is, the count value WTy is equal to or larger than the predetermined value P (= 50) and the yaw rate sensor 43 is out of order. If so, the program proceeds to the "fault detection process" routine consisting of steps 230-232.

When the vehicle is in a stopped state or a substantially stopped state and the yaw rate Y detected by the yaw rate sensor 43, which should be zero, continues to show an abnormal value for about 0.5 seconds (10 milliseconds × 50) like an abnormality, The CPU 45b executes the processing of steps 210 and 212 and the processing of the "yaw rate sensor failure detection" routine consisting of steps 220 to 223 to execute the processing of the yaw rate sensor 43.
Detect the failure of. Accordingly, when the detected yaw rate Y shows an abnormal value for a moment due to the temporary vibration of the sensor 43 due to the vibration of the vehicle body, the sensor 43 is not determined to be in failure, and the failure detection of the sensor 43 is detected. Will be done accurately.

(4) “Fault detection processing routine” This routine is for performing processing associated with failure detection of the yaw rate sensor 43 or the front wheel steering angle sensor 41.
The U 45b executes the processing of this routine on condition that the determination is "YES" in step 223 of the "yaw rate sensor failure detection" routine or step 253 of the "front wheel steering angle sensor failure detection" routine described later.

In other words, after the above determination, the CPU 45b sends the I / O 45 at step 230.
A lighting control signal is output to the warning lamp 47 via g. As a result, the lamp 47 continues to be lit, and the driver can visually recognize the failure of the yaw rate sensor 43 or the front wheel steering angle sensor 41. After the processing of step 230, the CPU 45b sets the failure flag OUTFLG to "1" in step 231, controls the first timer circuit 45d to be inactive in step 232, and controls to set the zero correction value in step 201. The calculation program ends. As a result, the first timer circuit 45d
Will no longer generate the first interrupt signal, and this "zero point correction value calculation" program will no longer be executed. This is because if the yaw rate sensor 43 or the front wheel steering angle sensor 41 fails, it is meaningless to calculate the zero-point correction values of the sensors 43, 41. The failure flag OUTFLG continues to be set to "1".

(5) Routine for calculating front wheel steering angle zero correction value routine This routine is for calculating the front wheel steering angle of the vehicle when the vehicle speed V is high to some extent and the yaw rate Y is substantially zero, that is, when the vehicle is traveling straight ahead. It is for calculating the front wheel steering angle zero point correction value Ao by calculating the deviation of the detected front wheel steering angle A from the zero point based on the fact that it is originally zero. If this condition is satisfied, the processing of this routine is repeatedly executed to calculate the front wheel steering angle zero correction value Ao.

That is, at the arrival of the first interrupt signal, the CPU 45b starts the execution of the “zero-point correction value calculation program” from step 200, and at step 210, the absolute value | V | In this case, since the vehicle is in a straight traveling state, the CPU 45b determines “NO” in the same step 210, that is, the absolute value | V | of the detected vehicle speed V is It is determined that the vehicle speed is not less than the predetermined vehicle speed α, and in step 240, the yaw rate zero point correction value Yo used in the process of the "yaw rate zero point correction value calculation" routine is calculated, and the yaw rate zero point correction sample value Ny is used. Also, the yaw rate zero point correction timer value Ty is set to "0". Next, the CPU 45b calculates the vehicle speed V based on the vehicle speed signal input from the vehicle speed sensor 42 via the I / O 45g in step 241, and calculates the absolute value | V | of the calculated detected vehicle speed V and the second predetermined vehicle speed β. To compare. The second predetermined vehicle speed β is preset in order to detect the running state of the vehicle at about 20 km / hour, and if the vehicle is in the normal running state, the CPU 45b determines “YES” in the same step 241, that is, the detected vehicle speed V. It is determined that the absolute value | V | of is greater than the second predetermined vehicle speed β, and the program proceeds to step 242. If the detected vehicle speed V is greater than or equal to the first predetermined vehicle speed α and less than or equal to the second predetermined vehicle speed β and the vehicle is running at an extremely low speed, the CPU 45b determines “NO” in step 241. ,
In step 248, the front wheel steering angle zero point error ΔAo used to calculate the front wheel steering angle zero point correction value Ao, the front wheel steering angle zero point correction sample value Na, and the front wheel steering angle zero point correction count value Ta are each “0”. , And the execution of the “zero-point correction value calculation” program is ended in step 201.

After determining "YES" in step 241, the CPU 45b
Is the absolute value of the difference between the detected yaw rate Y represented by the yaw rate signal input from the yaw rate sensor 43 through the I / O 45g in step 242 and the yaw rate zero correction value Yo | Y−
Yo | is compared with a predetermined yaw rate γ (about 1 degree / second).
In this case, since the detected yaw rate Y is substantially equal to the yaw rate zero point correction value Yo when the vehicle is in a straight traveling state, the CPU 45b
Is YES in step 242, that is, the absolute value | Y−Yo
| Is determined to be smaller than the predetermined yaw rate γ, and the program proceeds to step 243. When the vehicle is in a turning state and the detected yaw rate is not close to the yaw rate zero correction value Yo, the CPU 45b in step 242 returns “NO”, that is, the absolute value | Y−Yo | is smaller than the predetermined yaw rate γ. When it is determined that there is no such error, the execution of the “zero point correction value calculation” program is ended in step 201 after the above-described processing of step 248.

After determining "YES" in step 242, the CPU 42b determines in step 243 the detected front wheel steering angle A and the front wheel steering angle A represented by the front wheel steering angle signal input from the front wheel steering angle sensor 41 through the I / O 45g. Absolute value of difference from zero correction value Ao | A−Ao
| Is compared with a predetermined steering angle δ. The predetermined steering angle δ is set to a small value corresponding to a rotation angle of the steering wheel 21 of about 2 to 5 degrees, and if the front wheel steering angle sensor 41 is operating normally, the detected front wheel in the straight traveling state. Although the steering angle A includes a slight error (detected front wheel steering angle error ΔAo), it becomes a value approximate to the front wheel steering angle zero correction value Ao.
Is YES in step 243, that is, the absolute value | A−Ao
Is determined to be less than the predetermined steering angle δ, and the program proceeds to step 244. If the absolute value | A−Ao | is greater than or equal to the predetermined steering angle δ, the CPU 45b determines in step 243 that “NO”, that is, the detected front wheel steering angle A indicates an abnormal value, and the program step The process proceeds to 250, and the process of the "front wheel steering angle sensor failure detection" routine is executed.

After the determination of "YES" in step 243, the CPU 45b, in step 244, detects the failure of the front wheel steering angle sensor used for the failure detection process of the front wheel steering angle sensor 41 in the "front wheel steering angle sensor failure detection" routine. Flag WFA and the front wheel steering angle sensor failure detection count value WTa are each "0".
Set to. Next, the CPU 45b sets the detected front wheel steering angle zero point error ΔAo, the front wheel steering angle zero point correction sample value Na, and the front wheel steering angle zero point correction timer value Ta which have been set to “0” as initial values in step 245, respectively. On the other hand, by adding the difference A-Ao between the sword-out front wheel steering angle A and the front wheel steering angle zero correction value Ao, the value "1", and the predetermined time value Δt (about 10 milliseconds), each value ΔAo, Update Na and Ta respectively. By this update, each value ΔAo, Na, Ta is the difference A-Ao,
After the processing of step 245, which is set to "1" and Δt, respectively, the CPU 45b determines in step 246 the front wheel steering angle zero point correction timer value Ta and the preset time value of about 5 seconds.
Compare with Tao. In this comparison, the set timer value Ta is not greater than or equal to the predetermined time value Tao, so the CPU 45b
Is determined to be “NO”, and the execution of this “zero-point correction value calculation” program is ended in step 201.

After this end, when the first predetermined time (about 10 milliseconds) has elapsed, the first timer circuit 45d again sends the first interrupt signal to the CPU 45b.
Then, the CPU 45b starts execution of the "zero-point correction value calculation" program from step 200 as in the above case. Then, as in the case described above, the vehicle is in a normal straight traveling state, and the detected front wheel steering angle A is the front wheel steering angle zero correction value Ao.
If it is close to the CPU 45b, the CPU 45b executes steps 210, 241, 242, 243.
Are sequentially determined as “NO”, “YES”, “YES”, “YES”, and at step 245, the detected front wheel steering angle zero point error ΔAo.
The zero point error ΔAo is updated by adding a new difference A-Ao between the detected front wheel steering angle A and the front wheel steering angle zero correction value Ao, and the steering angle zero correction sample value Na and the front steering angle zero point are updated. By adding the value “1” and the predetermined time value Δt to the correction timer value Ta, the values Na and Ta are updated to “2” and 2 · Δt, respectively. After this update, the CPU 45b performs Ta (= 2 · Δt) <T in step 246, as in the above case.
It is determined to be "NO" based on the relationship of ao, and the execution of the "zero point correction value calculation" program is ended in step 201.

Then, when the first predetermined time (about 10 milliseconds) has passed again, the CPU 45b starts executing the "zero-point correction value calculation" program from step 200, and unless the above-described state of the vehicle and the detected front wheel steering angle A changes, After the processing of steps 210 and 240 to 246, the execution of the program ends in step 201. In this way, as a result of the processing of step 245 being repeatedly executed every first predetermined time, the detected front wheel steering angle zero point error ΔAo is a value obtained by accumulating the error of the detected front wheel steering angle A from the front wheel steering angle zero correction value Ao. On the other hand, the front wheel steering angle zero point correction sample value Na and the front wheel steering angle zero point correction timer value Ta increase every first predetermined time. And the repetition is 500
When the number of times is about the same, the timer value Ta is set to the predetermined time value Tao (about 5
Seconds) or more. At this time, the CPU 45b determines “YES” in the comparison in step 246, and adds the value ΔAo / Na obtained by dividing the zero-point error ΔAo by the same sample value Na to the front-wheel steering angle zero-point correction value Ao in step 247. Due to the same zero correction value Ao
To update. In this case, the same sample value Na is the same zero point error ΔAo
The value ΔAo / Na is the average value of the deviation of the detected front wheel steering angle A from the front wheel steering angle zero correction value Ao over a period of about 5 seconds, and the zero correction value Ao is the average value. Will be corrected by. This step 247
After that, the CPU 45b, in step 248, detects the front wheel steering angle zero point error ΔAo, the front wheel steering angle zero point correction sample value Na, and the front wheel steering angle zero point correction in preparation for the next update of the front wheel steering angle zero point correction value Ao. The timer values Ta for each are initially set to "0", and the execution of this "zero point correction value calculation" program is ended in step 201. Further, if the vehicle continues to be in a normal straight traveling state and the detected front wheel steering angle A is close to the front wheel steering angle zero correction value Ao, the CPU 45b executes the "front wheel steering angle zero point" including steps 240 to 248 as described above. The "correction value calculation" routine is repeatedly executed to update the front wheel steering angle zero correction value Ao about every 5 seconds.

As can be understood from the above description, as in the case of the detected yaw rate, the deviation of the detected front wheel steering angle A sampled about every 10 milliseconds from the front wheel steering angle zero correction value Ao is about 5 Front wheel steering angle zero point error Δ detected over seconds
The error ΔAo is accumulated as Ao, and the error ΔAo is averaged by the sampling value Na equal to the number of times of accumulation, so that the influence of the sampling error per value ΔAo / Na once becomes small. And
This value ΔAo / Na is added to the front wheel steering angle zero point correction value Ao about every 5 seconds to correct the same zero point correction value Ao. Therefore, the same zero point correction value Ao is measured by the front wheel steering angle sensor 41 for a long time. Since the deviation of the zero point of the detected front wheel steering angle A is learned, the accuracy of the zero point correction value Ao is improved.

In the "front wheel steering angle zero correction value calculation" routine, the front wheel steering angle zero correction timer value Ta and the predetermined time value
Although the predetermined time (about 5 seconds) is detected by comparing Tao with step 246, this routine is executed about every 10 milliseconds, so the front wheel steering angle zero point correction sample value Na Is about 500 or more Step 2
By comparing at 46, detection may be performed for a predetermined time (about 5 seconds).

(6) "Front wheel steering angle sensor failure detection" routine This routine is based on the fact that the front wheel steering angle of the vehicle is originally zero when the vehicle is in a normal straight traveling state, and therefore the detected front wheel should be zero. The CPU 45b is for detecting a failure of the front wheel steering angle sensor 41 by detecting that the steering angle A is largely deviated from the zero point continuously for a certain period of time. On condition that the angle is largely deviated from the zero point, the processing of this routine is repeatedly executed to detect the failure of the front wheel steering angle sensor 41.

That is, upon arrival of the first interrupt signal, the CPU 45b starts execution of the "zero-point correction value calculation" program from step 200, and steps 210, 240 to 242 similar to the case of (5) above.
After the above processing, in step 243 the front wheel steering angle sensor 41 receives I / O.
The absolute value | A−Ao | of the difference between the detected front wheel steering angle A represented by the front wheel steering angle signal input via 45g and the front wheel steering angle zero correction value Ao is compared with the predetermined steering angle δ. in this case,
Since the detected front wheel steering angle A is largely deviated from the front wheel steering angle zero correction value Ao, in the comparison of step 243, C
The PU 45b determines that “NO”, that is, | A−Ao | is not less than the predetermined steering angle δ (about 2 to 5 degrees in terms of the rotation angle of the steering wheel 21) and proceeds to the program step 250. Step 250
At first, the front wheel steering angle sensor failure detection flag
WFa is step 101 (3rd
(Fig.) Or the "front wheel steering angle zero correction value calculation" routine is set to "0" by the processing of step 244, so C
The PU 45b determines “NO”, that is, the flag WFA is not “1”. After this determination, the CPU 45b sends the flag W in step 251.
Fa is set to "1", the front wheel steering angle sensor failure detection count value WTa is set to "1", and the set same count value WTa is compared with a predetermined value q in step 253. In this case, since the predetermined value q is preset to "50", the CPU 45b determines "NO" in the same step 253, that is, the same count value WTa is not equal to or larger than the predetermined value q, and in step 248 the above ( The same processing as in the case of 5) is performed, and the execution of the "zero point correction value calculation" program is ended in step 201.

After this end, when the first predetermined time (about 10 milliseconds) has elapsed, the first timer circuit 45d outputs the first interrupt signal to the CPU 45b again as in the case of (5) above, and the CPU 45b outputs the same signal as in the above case. Similarly, the execution of the “zero point correction value calculation” program is started from step 200. Then, as in the above case, if the vehicle is still in the normal straight traveling state and the detected front wheel steering angle A is largely deviated from the front wheel steering angle zero correction value Ao, the CPU 45b sequentially performs steps 210, 241, 242, 243. The program proceeds to step 250 by judging "NO", "YES", "YES", and "NO". In this case, since the front wheel steering angle sensor failure detection flag WFa has been set to "1" by the processing of the above step 251, the CPU 45b causes the same step 250
It is determined to be "YES" in step 25, and the above step 25 is performed in step 252.
The count value WTa is set to "2" by adding "1" to the front wheel steering angle sensor failure detection count value WTa set to "1" by the processing of 1. After the processing of step 252, the CPU 45b proceeds to step 253, where WTa (=
2) Based on the relationship of <q (= 50), it is determined to be "NO", and after the processing of step 248, the execution of this "zero point correction value calculation" program is ended in step 201.

Then, when the first predetermined time (about 10 milliseconds) has passed again, the CPU 45b starts executing the "zero-point correction value calculation" program from step 200, and unless the above-described state of the vehicle and the detected front wheel steering angle A changes, Step 210,240〜243,250,2
After the processing of 52, 253 and 248, the execution of the program is ended in step 201. In this way, the process of step 252 is repeatedly executed every first predetermined time, and the front wheel steering angle sensor failure detection count value WTa sequentially increases by "1". When the count value WTa reaches “50” due to this increase, the CPU 45b determines “YES” in step 253, that is, the count value WTa is equal to or greater than the predetermined value q (= 50) and the front wheel steering angle sensor 41 fails. If so, the program proceeds to the "fault detection processing" routine consisting of steps 230-232.

As described above, when the vehicle is in a normal straight traveling state, the front wheel steering angle A detected by the front wheel steering angle sensor 41, which should have been zero, continues to show an abnormal value for about 0.5 seconds (10 milliseconds × 50). As shown, the CPU 45b performs "front wheel steering angle sensor failure detection" including steps 210, 241-243 and steps 250-253.
By executing the routine processing, the failure of the front wheel steering angle sensor 41 is detected. As a result, the sensor 41 associated with vehicle body vibration
When the detected front wheel steering angle A shows an abnormal value for a moment due to the temporary vibration of the sensor 41, the sensor 41 is not determined to be in failure, and the failure of the sensor 41 is accurately detected. .

(7) "Rear wheel steering control" program This program is for steering the left and right rear wheels 11a, 11b, and the CPU 45b executes a second interrupt signal every time the second timer circuit 45e issues a second interrupt signal to the CPU 45b. By repeatedly executing this program to control the rotation of the electric motor 31, the steering of the left and right rear wheels 11a and 11b is controlled. That is, upon arrival of the second interrupt signal, the CPU 45b starts execution of this "rear wheel steering control" program from step 300 in FIG. 5, and in step 301 it is determined whether the failure flag OUTFLG is "1" or not. judge.

First, a case where the front wheel steering angle sensor 41 and the yaw rate sensor 43 have not failed will be described. In this case, the failure flag OUTFLG is set in step 101 of the “Initialize” program.
It remains set to "0" by the process of (Fig. 3),
The CPU 45b determines “NO” in step 301, and proceeds to step 302
From the yaw rate sensor 43 and the front wheel steering angle sensor 41
A yaw rate signal and a front wheel steering angle signal are respectively input via 045g, and a detected yaw rate Y and a detected front wheel steering angle A are represented by a "yaw rate zero point correction value calculation" routine and a "front wheel steering angle zero point". The correction detection yaw rate Y * = Y + Yo and the correction detection front wheel steering angle A * = in which both the detection values Y and A are zero-corrected by adding the respective zero-point correction values Yo and Ao calculated in the “correction value calculation” routine. A
+ Ao is calculated and stored in the working memory 45c.

After the processing of step 302, in step 303, the CPU 45b first calculates the vehicle speed V based on the vehicle speed signal input from the vehicle speed sensor 42 via the I / O 45g, and based on the calculated detected vehicle speed V, calculates the steering angle ratio table 45f. The steering angle ratio K1 (V) corresponding to the vehicle speed is derived by referring to it. Next, the CPU 45b executes the same step 30.
At 3, the target is obtained by executing the arithmetic processing represented by the following (formula) based on the vehicle speed corresponding steering angle ratio K1 (V), the stored correction detection yaw rate Y * and the correction detection front wheel steering angle A *. The rear wheel steering angle θr * is calculated.

θr * = K1 (V) · A * + K2 · Y * (Equation) In the above (Equation), K2 is a constant, so that the target rear wheel steering angle θr * is as shown in FIG. The steering angle ratio characteristic corresponding to the vehicle speed and the yaw rate of the vehicle are determined.

After the processing of step 303, the CPU 45b inputs the rear wheel steering angle signal from the rear wheel steering angle sensor 44 through the I / O 45g in step 304, and calculates the calculated target rear wheel steering angle θr * and the rear wheel steering angle. Difference θ from the detected rear wheel steering angle θr represented by the angle signal
Output digital data corresponding to r * -θr to I / O 45g. The I / O 45g converts the digital data into an analog signal and supplies the analog signal to the power amplifier 46, and the power amplifier 46 rotationally drives the electric motor 31 based on the analog signal. By driving this electric motor 31, the rear wheel steering shaft 32 is rotated, and the coaxial 32 is assisted by the power cylinder 37 so that the left and right rear wheels 11a,
Steer 11b to the target rear wheel steering angle θr *. Step 3 above
After the processing of 04, the CPU 45b ends the execution of this "rear wheel steering control" program in step 305. After the end of this program, the second predetermined time (several tens of milliseconds to several hundreds of milliseconds) elapses, and the second timer circuit 45e outputs the second interrupt signal C again.
When output to PU45b, CPU45b does the same as above for step 300.
The processing of steps 305 to 305 is performed to steer the left and right rear wheels 11a and 11b. In this case, the second predetermined time is determined in consideration of the responsiveness of the rear wheel steering device 30, and the left and right rear wheels 11a, 11a, 11 are processed by repeating the "rear wheel steering control" program every second predetermined time.
b is steered to the target rear wheel steering angle θr * without delay.

Thus, in the "rear wheel steering control" program,
The detected yaw rate Y and the detected front wheel steering angle A are corrected by the yaw rate zero-point correction value Yo and the front wheel steering angle zero-point correction value Ao, and the left and right rear wheels 11a, 11b are corrected by the corrected detected yaw rate Y * and the corrected detected front wheel steering angle A *. Since the steering angle is controlled, even if the zero point of the yaw rate sensor 43 or the front wheel steering angle sensor 41 is deviated, the steering control of the left and right rear wheels 11a, 11b is accurately performed, and the running stability of the vehicle is improved.

Next, a case will be described in which the yaw rate sensor 43 or the front wheel steering angle sensor 41 has failed and the failure flag OUTFLG is set to "1" by the processing of step 231 (FIG. 4) of the "failure detection processing" routine. . In this case, the failure flag OU
Since TFLG is set to "1", the second interrupt signal is CP
Each time this "rear wheel steering control" program is input to the U45b and executed as described above, the CPU 45b determines "YES" in step 301, executes the failure process in step 306, and then executes in step 305. The execution of the program ends. In the failure processing of step 306, the CPU 45b determines that the left and right rear wheels 1
Incorrect steering control of the left and right rear wheels 11a, 11b due to a failure of the yaw rate sensor 43 or the front wheel steering angle sensor 41, such as returning 1a, 11b to the neutral position or fixing the steering angle of the rear wheels 11a, 11b. Take preventive action. However, this failure processing is not directly related to the present invention, so a detailed description thereof will be omitted.

It should be noted that, in the above-described embodiment, the comparison judgment in step 210 (FIG. 4) is made under the condition that the absolute value | V | of the detected vehicle speed V is less than the first predetermined vehicle speed α when the vehicle is stopped or substantially stopped. However, other means may be used as long as the state of the vehicle can be detected. For example, in an automatic transmission vehicle, it is also possible to detect a stopped state or a substantially stopped state of the vehicle on condition that the shift position of the transmission is at the parking position.

In this case, a switch for detecting that the shift lever is in the parking range is provided, and instead of the determination based on the vehicle speed V, it is preferable to determine the on / off state of the switch in step 210. Further, in a manual transmission vehicle, it is also possible to detect a stopped state or a substantially stopped state of the vehicle on the condition that the shift position of the transmission is in the neutral position and the parking brake is operated. In this case, a first switch that detects that the shift lever is in the neutral position and a second switch that detects that the parking brake lever is pulled are provided, and instead of the determination based on the vehicle speed V in step 210, First, it is preferable to determine the on / off state of the first and second switches.

In the above embodiment, the sampled yaw rate Y and the detected front wheel steering angle A are used as they are, and steps 214 and 216 (FIG. 4) and steps 245 and 247 (FIG. 4) are used.
By executing each of the processing, the average error ΔYo / Ny of the detected yaw rate zero point error ΔYo and the average error ΔAo / Na of the detected front wheel steering angle zero point error ΔAo were calculated respectively. ΔYo / Ny and ΔAo / Na may be obtained. That is, by sequentially interpolating the detected yaw rate Y and the detected front wheel steering angle A with a straight line or by interpolating with a curve such as quadratic, cubic ... Represented by a time function that fluctuates with respect to the correction value Yo and the front wheel steering angle zero correction value Ao, these functions are integrated over time and the integrated value is divided by the integration time, and each average error ΔYo / Ny,
ΔAo / Na may be calculated. Since this improves the accuracy of error detection, the time required to detect the average errors ΔYo / Ny and ΔAo / Na can be shortened.

Further, in the above embodiment, once the failure of the yaw rate sensor 43 and the front wheel steering angle sensor 41 is detected by the processing of steps 223 and 253, the "zero point correction value calculation" program (Fig. 4) is prevented from being executed again. Although the steering control of the left and right rear wheels 11a, 11b by the respective sensors 43, 41 is not performed, a program for detecting recovery of the failure of the respective sensors 43, 41 is further provided, and when the failure is detected. When the recovery of the failure of each of the sensors 43, 41 is detected by executing this program, the "zero point correction value calculation" program (Fig. 4) is executed again. Further, the left and right rear wheels 11a, 11b may be controlled by the yaw rate Y detected by the sensors 43, 41 and the front wheel steering angle A detected.

In the above embodiment, the "initial setting" program (Fig. 3) is executed every time the ignition switch is closed, and all variables are initialized by the processing of step 101. Regarding the zero point correction value Yo and the front wheel steering angle zero point correction value Ao, this initial setting may not be executed, and the same values Yo, Ao may be stored regardless of whether the ignition switch is opened or closed. In this case, a part of the working memory 45c is configured by a non-volatile memory (non-volatile RAM), and both zero point correction values Yo,
Ao may be stored in this non-volatile memory. As a result, the detected yaw rate Y and the detected front wheel steering angle A are corrected by the both zero point correction values Yo and Ao which have learned the deviation of the zero points of the detected yaw rate Y and the detected front wheel steering angle A for a very long time. The accuracy of the correction is further improved.

Furthermore, in the above embodiment, the present invention is applied to the left and right rear wheels 11a,
Although the example applied to the steering control of 11b has been described, the present invention is also applied to the case where the yaw rate sensor 43 or the front wheel steering angle sensor 41 is used for other electronic control such as a suspension device and an anti-skid device.

[Brief description of drawings]

1 is a diagram corresponding to the configuration of the present invention described in the claims, FIG. 2 is an overall schematic diagram of a front and rear wheel steering vehicle to which the present invention is applied, and FIGS. 3 to 5 are FIG. FIG. 6 is a flowchart of a program executed by the microcomputer of FIG. 6 and FIG. 6 is a diagram showing the characteristics of the steering angle ratio corresponding to the vehicle speed. Explanation of symbols 10a, 10b …… front wheels, 11a, 11b …… rear wheels, 20 …… front wheel steering device, 30 …… rear wheel steering device, 40 …… electric control device, 41 ……
Front wheel steering angle sensor, 42 …… vehicle speed sensor, 43 …… yaw rate sensor, 45 …… microcomputer.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B62D 137: 00

Claims (1)

[Claims] 1. A detection front wheel steering angle correction device for correcting a detection front wheel steering angle detected by a front wheel steering angle sensor, comprising: sampling means for sequentially sampling the detection front wheel steering angle detected by the front wheel steering angle sensor. A reference value storage means for storing a reference value corresponding to a zero point of the detected front wheel steering angle, a vehicle speed detection means for detecting a vehicle speed, a yaw rate detection means for detecting a yaw rate of the vehicle, and the detected vehicle speed is larger than a predetermined value. Determination means for determining that the vehicle is in a straight traveling state on the condition that the detected yaw rate is substantially zero; and the sampled front wheel steering angle of the detected front wheel steering angle when the determination means determines the straight traveling state of the vehicle. Accumulating means for accumulating a value corresponding to the deviation from the reference value for a predetermined time at each sampling timing; Reference value updating means for updating the reference value by adding the accumulated result, and correction calculation means for correcting the detected front wheel steering angle by performing a correction calculation for adding the updated reference value to the detected front wheel steering angle. A detection front-wheel steering angle correction device comprising: