JP2536204B2 - Abnormality detection device for yaw rate sensor output - Google Patents

Description

The present invention relates to a yaw rate sensor output abnormality detecting device for detecting an abnormal output of a yaw rate sensor used for steering control of a vehicle.

[Prior Art] Conventionally, a yaw rate sensor for detecting a yaw rate acting on a vehicle body is provided, and in order to improve the steering stability of the vehicle, feedback control of steering of front wheels or rear wheels is performed according to the output of the yaw rate sensor. The steering control device for a vehicle described above is well known. (For example, JP-A-60-1612
(See Japanese Patent Publication No. 55) [Problems to be solved by the invention] However, when controlling the behavior of the vehicle by using the yaw rate sensor output as described above, an abnormality in the sensor output can be detected and the abnormality can be dealt with. It is indispensable to do so, and conventionally, it has been desired to develop a device capable of detecting an abnormality in the output of the yaw rate sensor.

The present invention has been made to address the above problems,
An object of the present invention is to provide a yaw rate sensor output abnormality detecting device capable of detecting an abnormality in the yaw rate sensor output with a simple configuration.

[Means for Solving the Problem] In order to achieve the above-mentioned object, a structural feature of the present invention is that front wheel steering speed detecting means (6) for detecting a front wheel steering speed.
1,72,73) and at least the rate of change of the detected yaw rate,
The yaw rate sensor is determined by the determination means (72 to 74, 76) that determines that the yaw rate sensor output is abnormal when the estimated maximum yaw rate change speed that is determined by the detected front wheel steering speed and increases as the front wheel steering speed increases is exceeded. This is because the output abnormality detection device was configured.

[Operation] In the present invention configured as described above, the front wheel steering speed detecting means detects the front wheel steering speed, and the determining means determines that at least the change rate of the detected yaw rate is determined by the detected front wheel steering speed. When the estimated maximum yaw rate change speed, which increases with an increase in, is exceeded, it is determined that the yaw rate sensor output is abnormal. The yaw rate that acts on the vehicle body is a physical quantity that is closely related to the steering of the vehicle.
The rate of change of the yaw rate is large when the steering wheel is suddenly rotated and the vehicle is steered steeply.
According to the above determination, the abnormality in the output of the yaw rate sensor is accurately determined.

[Effects of the Invention] As can be understood from the above description of the operation, according to the present invention, the abnormality of the output of the yaw rate sensor is detected with a simple structure, and the abnormality can be dealt with and the behavior of the vehicle is controlled by the yaw rate sensor. Functions are enhanced. Further, the front wheel steering speed detecting means used in the present invention differentiates the output of the front wheel steering angle sensor normally mounted on the vehicle when controlling the steering of the vehicle such as a front and rear wheel steering vehicle. Since it is configured by means, it is often unnecessary to provide the same sensor for the present invention, and the present invention is economically advantageous.

[Embodiment] An embodiment in which the abnormality detection device for the output of the yaw rate sensor according to the present invention is used for the rear wheel steering control of a front and rear wheel steering vehicle will be described below with reference to the drawings. The whole is shown schematically. This front and rear wheel steering vehicle has a front wheel steering device A for steering the left and right front wheels FW1 and FW2 and a left and right rear wheel R.
Rear wheel steering device B for steering W1, RW2 and left and right rear wheels RW1, RW2
In addition to the mechanical control by the front wheel steering device B, an electric control device C for electrically controlling

The front wheel steering device A is axially displaced and the left and right front wheels FW1, FW2
It has a rack bar 11 for steering. The rack bar 11 is supported in the steering gear box 12 so as to be displaceable in the axial direction and is connected to the lower end of the steering shaft 13 in the box 12, and a steering handle 14 provided at the upper end of the steering shaft 13. The shaft is displaced in the axial direction according to the rotation of the. The left and right front wheels FW1, FW2 are attached to both ends of the rack bar 11 via the left and right tie rods 15a, 15b and the left and right knuckle arms 16a, 16b.
Are steerably connected, and the front wheels FW1 and FW2 are steered in accordance with the axial displacement of the rack bar 11. A control valve (not shown) consisting of a four-way valve is incorporated in the steering gear box 12,
The valve supplies the hydraulic oil from the shunt valve 18 connected to the hydraulic pump 17 to the power cylinder 21 according to the steering torque acting on the steering shaft 13, and discharges the hydraulic oil from the cylinder 21 to the reservoir 22. . The power cylinder 21 drives the rack bar 11 in the axial direction according to the supply and discharge of hydraulic oil to assist the steering of the left and right front wheels FW1 and FW2.

The rear wheel steering device B is axially displaced and the left and right rear wheels RW1, RW2
, The left and right rear wheels RW1, via left and right tie rods 32a, 32b and left and right knuckle arms 33a, 33b, at both ends thereof, as in the case of the front wheel steering device A. RW2 is steerably connected. The relay rod 31 is biased to a neutral position by a spring 34, and is driven in an axial direction by a power cylinder 35.

The power cylinder 35, together with the spool valve 38 and the lever 41, constitutes a hydraulic pressure copying mechanism. The spool valve 38 is a valve sleeve that is axially displaceable with respect to the vehicle body.
38a and a valve spool 38b housed in the sleeve 38a so as to be slidable in the axial direction. The flow dividing valve 18 is provided in accordance with relative displacement between the valve sleeve 38a and the valve spool 38b.
To control the supply of hydraulic oil to one oil chamber of the power cylinder 35 and the discharge of hydraulic oil from the other oil chamber to the reservoir 22. A drive rod 43 biased to a neutral position by a spring 42 is connected to the valve sleeve 38a, and the rod 43 is in contact with a cam plate 44. Cam plate 44
A pair of cables 45, 46 are respectively wound around the outer peripheral side surface of the cable, and the cables 45, 46 are fixed to the cam plate 44 at their rear ends. These cables 45,46
Is to rotate the cam plate 44 in conjunction with the steering of the left and right front wheels FW1 and FW2. The cam plate 44 is extended to the front of the vehicle, and its front ends are fixed to both ends of the rack bar 11 of the front wheel steering device A. ing. Then, when the left and right front wheels FW1, FW2 are steered and the rack bar 11 is displaced left and right, the cables 45, 4
6 rotates the cam plate 44, and this rotation causes the drive rod 43 to be displaced in the axial direction, but when the cam plate 44 is in a small rotation range from the neutral position, the drive rod 43
Is kept in a neutral position. A valve spool 38b of the spool valve 38 is slidably and tiltably engaged with an intermediate portion of a lever 41 via a connecting rod 47.

The lower end of the lever 41 is slidably and tiltably engaged with the relay rod 31. The upper end of the lever 41 is the wheel
It is rotatably connected to the wheel 48 at a position eccentric from the center of rotation on the upper surface of 48. The wheel 48 meshes with the worm 51 on the outer circumference thereof, and rotates around the rotation center according to the rotation of the worm 51. The worm 51 is connected to a rotating shaft of an electric motor 52 composed of a step motor so as to rotate integrally therewith.

The electric control device C includes a front wheel steering angle sensor 61 and a vehicle speed sensor 6
2. A yaw rate sensor 63, a rear wheel steering angle sensor 64 and a microcomputer 65 are provided.

The front wheel steering angle sensor 61 is mounted on the outer periphery of the steering shaft 13 and detects the rotation angle of the coaxial 13 so that the left and right front wheels FW are detected.
A detection signal representing the steering angle δf of 1, FW2 is output. The vehicle speed sensor 62 outputs a detection signal indicating the vehicle speed V by detecting the rotation speed of the output shaft of a transmission (not shown). The yaw rate sensor 63 is fixed to the vehicle body and detects a rotation speed of the vehicle body about a vertical axis of the center of gravity thereof, thereby outputting a detection signal representing a yaw rate γ acting on the vehicle body. As the yaw rate sensor 63, for example, a known angular velocity sensor as disclosed in JP-A-63-252220 can be used. By detecting the rotation angle of the electric motor 52, the rear wheel steering angle sensor 64 outputs a detection signal indicating the steering angle δr of the left and right rear wheels RW1, RW2 steered according to the rotation of the electric motor 52. The front wheel steering angle δf and the rear wheel steering angle δr show positive values when the left and right front wheels FW1 and FW2 and the left and right rear wheels RW1 and RW2 are steered to the right, and when the respective wheels are steered to the left. Indicates a negative value. The yaw rate γ shows a positive value when the vehicle body rotates clockwise and a negative value when the vehicle body rotates counterclockwise.

Each of these sensors 61 to 64 is connected to the interface 65e of the microcomputer 65. The microcomputer 65 includes a ROM 65b and a CPU 65 that are commonly connected to the bus 65a.
c, RAM 65d and interface 65e. The ROM 65b stores a program corresponding to the flowchart of FIG. 2, and the estimated maximum yaw rate γ _EM and the estimated maximum yaw rate change speed _EM are used as the first and second yaw rate tables, and the first and second coefficients K ₁ , K. ₂ for 1st and 2nd
It is stored as a coefficient table. Estimated maximum yaw rate γ _EM and estimated maximum yaw rate change speed _EM are the left and right front wheels
When steering 1 and FW2, the front wheel steering angle δf and the front wheel steering speed f
Represents the maximum possible amount for the front wheel steering angle δf as shown in the graphs of FIGS. 3 and 4.
And the absolute values of the front wheel steering speed f | δf | and | f | increase. The first and second coefficients K ₁ and K ₂ change according to the vehicle speed V, and the first coefficient K ₁ is, as shown in the graph of FIG. Shows a negative value in the area,
Moreover, the second coefficient K ₂ indicates a value that increases as the vehicle speed V increases from a medium range to a large range of the vehicle speed V.

The CPU 65c executes the above program, RAM6
5d temporarily stores variables necessary for executing the program. The interface 65e receives the detection signals from the sensors 61 to 64 and outputs the rotation control signal to the electric motor 52, as described above.

Next, the operation of the embodiment configured as described above will be described.

When the ignition switch (not shown) is closed, the CPU 65c starts executing the program in step 70 of FIG. 2, and initializes the flag data FLG to "0" in step 71. After executing, the circulation process consisting of steps 72 to 81 is repeatedly executed unless an abnormality in the output of the yaw rate sensor 63 described later is detected. The flag data FLG is normally set to "0",
It is set to "1" when the output of the yaw rate sensor 63 is abnormal.

In the execution of the circulation processing, in step 72, the respective detection signals from the front wheel steering angle sensor 61, the vehicle speed sensor 62, the yaw rate sensor 63 and the rear wheel steering angle sensor 64 are respectively taken in, and the front wheel steering angle δf and the vehicle speed V are acquired. , Yaw rate γ and rear wheel steering angle δr are stored in the RAM 65d as data respectively. In such a case, regarding the front wheel steering angle δf and the yaw rate γ, the fetched data is stored in the RAM 65d as new data representing the current front wheel steering angle δf and the yaw rate γ, respectively, and is also stored in the RAM 65d from before. At least one data representing the previous front wheel steering angle δf and yaw rate γ that have been stored is stored and held in the RAM 65d as past data.

After the processing of step 72, the rate of change (differential value) f of the front wheel steering angle δf and the yaw rate γ is calculated in step 73 based on the new data and the past data concerning the front wheel steering angle δf and the yaw rate γ. Stored in the RAM 65d. In order to realize such a differential operation, the time required for the circulation processing from the processing of step 73 to the processing of step 73 again is always constant. Further, even if the time required for this circulation processing is not fixed, the time required for the circulation processing may be counted by a timer or the like and the counted time may be used for the differential operation.

Next, in step 74, the first and second yaw rate tables are referred to, and the RAM 65 is processed by the processing in steps 72 and 73.
The estimated maximum yaw rate γ _EM and the estimated maximum yaw rate change rate _EM corresponding to the absolute values | δf |, | f | of the current front wheel steering angle δf and front wheel steering speed f stored in d are derived. These estimated maximum yaw rate γ _EM and estimated maximum yaw rate change speed _EM are calculated in steps 75 and 76 as follows.
By the processing of steps 72 and 73, the current yaw rate γ and the absolute values of the yaw rate change speed | γ |, || stored in the RAM 65d are compared. In such a case, the output of the yaw rate sensor 63 is normal and the absolute values | γ
If |, || are equal to or less than the estimated maximum yaw rate γ _EM and the estimated maximum yaw rate change speed _EM, respectively, the same step 7
Both 5 and 76 are judged as "YES", and step 7
In step 7, it is determined to be "YES" based on the flag data FLG initially set to "0", and the program proceeds to step 78 and thereafter.

In step 78, the current yaw rate γ is set as the yaw rate γ * for calculation of the target rear wheel steering angle δf *, and in step 79, the first and second coefficient tables are referred to and the first yaw rate corresponding to the detected vehicle speed V is set. The first and second coefficients K ₁ and K ₂ are derived. After the processing in steps 78 and 79, in step 80, by executing the following formula based on the first and second coefficients K ₁ and K ₂ , the front wheel steering angle δf and the calculation yaw rate γ *, The wheel steering angle δr * is calculated.

δr * = K ₁ δfK ₂ + K ₂ γ * In step 81, a difference δr * −δr between the target rear wheel steering angle δr * and the detected rear wheel steering angle δr is calculated and an error is dealt with. A control signal indicating the rotation amount of the electric motor 52 is output to the interface 65e. The interface 65e, based on the control signal, the electric motor 5
2 is rotated by a rotation amount corresponding to the difference δr * −δr, and the steering angles of the left and right rear wheels RW1 and RW2 are changed to the target rear wheel steering angle δ.
Set to r *.

The steering control of the left and right rear wheels RW1, RW2 will be described in detail. The rotation of the electric motor 52 causes the worm 51 to rotate.
The rotating plate 48 rotates via the. In this case, the upper end of the lever 41 is rotatably supported by the rotation plate 48 so that the rotation center of the rotation plate 48 is eccentric.
Since it is attached to 48, its upper end is displaced in the left-right direction in FIG. Due to this displacement, the valve spool 38b assembled in the middle of the lever 41 is also displaced in the same direction,
A relative displacement occurs between the valve sleeve 38a and the valve spool 38b. In such a case, the spool valve 38
The cooperation of the relay rod 31 and the lever 41 controls the supply and discharge of hydraulic oil to and from the power cylinder 35 so that the relative displacement between the valve sleeve 38a and the valve spool 38b is eliminated, and the relay rod 31 is moved to the lever. The left and right rear wheels RW1 and RW2 are steered to the target rear wheel steering angle δr * because the left and right rear wheels are displaced by an amount corresponding to the displacement amount of the upper end portion of 41.

The electric steering control by the various sensors 61 to 64 and the microcomputer 65 has a small front wheel steering angle δf and a small rotation amount even if the cam plate 44 rotates. This is a case where 38a is almost at the reference position and mechanical control via the cables 45 and 46 does not affect the steering control of the left and right rear wheels RW1 and RW2.

In this way, the left and right rear wheels RW1, RW2 are electrically steered and controlled, and as a result, the first coefficient K ₁ shows a negative value in the low vehicle speed and medium vehicle speed regions, and the steering control is performed as described above. Since steering of the vehicle is affected in a region where the front wheel steering angle δf is small, the steering control improves the initial turning of the vehicle when the left and right front wheels FW1 and FW2 are steered during low speed to medium speed running. Further, since the second coefficient K ₂ has a positive value in the medium vehicle speed and high vehicle speed regions, the steering control causes the vehicle body due to steering of the left and right front wheels FW1 and FW2 at the time of traveling from medium speed to high speed and cross wind. The yaw rate that occurs in the vehicle is suppressed, and the traveling stability at the medium speed and the high speed of the vehicle is improved.

On the other hand, the steering wheel 14 is largely turned, and the left and right front wheels FW
When the steering angle δf of 1 and FW2 increases, the rotational angle of the cam plate 44 that is rotationally driven via the cables 45 and 46 increases due to the axial displacement of the rack bar 11, and the drive rod 43
Starts to move in the axial direction. Due to this displacement, the valve sleeve 38a is displaced in the same direction and a relative displacement is caused between the valve sleeve 38a and the valve spool 38b, and the spool valve 38, the power cylinder 35, the relay rod 31
And the hydraulic imitation of lever 41 causes the left and right rear wheels RW1, RW2
Is steering controlled. In this steering control, due to the cam shape of the cam plate 44, the left and right rear wheels RW1, RW2 are
Since it is set to be steered in reverse phase with respect to W1 and FW2, the small-turn performance of the vehicle at low speed traveling is improved by such reverse-phase steering control by the cables 45 and 46, the cam plate 44, and the like. In this case, the electric steering control described above also works, but the control amount thereof is smaller than that of the mechanical steering control. Therefore, in the same case, the mechanical steering control has priority.

Returning to the explanation of the program of FIG. 2 again, during the steering control of the left and right rear wheels RW1 and RW2 by the circulation processing including the steps 72 to 81 as described above, the yaw rate sensor 63 breaks down or the road surface causes the vehicle body to move. When an impact force is applied and the sensor 63 generates an abnormal detection signal, the CPU 66c determines “NO” in step 75 or step 76 and advances the program to step 82. That is, in such a case, the absolute value | γ | of the detection output of the yaw rate sensor 63 shows an abnormally large value, or the absolute value of the change rate of the detection output ||
May show an abnormally large value, so that the above step may be performed based on the judgment condition | γ | ≦ γ _EM or || ≦ _EM.
It is determined to be "NO" in step 75 or step 76. Step 82
, The flag data FLG is set to "1", and the left and right rear wheels RW1 and RW2 are steered to the target rear wheel steering angle δr * by the processing of steps 79 to 81 described above. In this case, since the processing of step 78 is not performed, the yaw rate γ * for calculation of the target rear wheel steering angle δr * is not updated and the previous value (the value before the yaw rate sensor 63 generates an abnormal output) is calculated. ). As a result, the yaw rate sensor 63
Even if a detection signal indicating an abnormal value is output, the target rear wheel steering angle δr * does not suddenly change, and the running stability of the vehicle becomes good. As described above, the yaw rate sensor
As long as 63 outputs an abnormal signal, steps 72 to 7 are performed based on the judgment of "NO" in step 75 or step 76.
The circulation processing of 6,82,79 to 81 continues to be executed.

During this circulation process, when the yaw rate sensor 63 starts to output a normal detection signal, it is determined to be "YES" in steps 75 and 76, and the flag data FLG set to "1" in step 77. Is determined to be "NO", and the program proceeds to step 83. In step 83, the yaw rate γ * for calculating the target rear wheel steering angle δr * is updated by executing the following calculation.

[gamma] * = [gamma] * + ([gamma]-[gamma] *) / N Note that the value N in the above equation is a predetermined large natural number, and by this calculation, the calculation yaw rate [gamma] * is ([gamma]-[gamma] *). ) / N each Current detected yaw rate γ
You can get closer to the value. After the process of step 83, whether the absolute value | γ * −γ | of the difference between the calculated yaw rate γ * and the current detected yaw rate γ value updated in step 84 is less than a predetermined small value Δγ. Is determined. In such a case, the above absolute value | γ * -γ
If | does not fall below the predetermined small value Δγ, based on the determination of “NO” in step 84, steps 72 to 77,8
The cyclic process consisting of 3,84,79 to 81 continues to be executed. In this circulation processing, as described above, the target rear wheel steering angle δ
The yaw rate γ * for calculating r * is the current detected yaw rate γ.
While gradually approaching the value, the calculation yaw rate γ *
The target rear wheel steering angle δr * is determined based on the above, and the left and right rear wheels RW1, RW2 are steered to the determined target rear wheel steering angle δr *. Accordingly, the detection output value γ of the yaw rate sensor 63
Even when the normal rear wheel steering angle returns to the normal value, the yaw rate γ * for calculating the target rear wheel steering angle δr * is gradually changed.
There is no sudden change in r *, and the running stability of the vehicle becomes good.

On the other hand, the absolute value | γ
If * -γ | becomes less than a predetermined small value Δγ,
Based on the determination of “YES” in 84, the yaw rate γ * for calculating the target rear wheel steering angle δr * is set to the current yaw rate γ in step 85, and the flag data FLG is set to “0” in step 86. Is set to ", the steering control by the microcomputer 65 is returned to the initial state, and thereafter, the circulation processing including the above steps 72 to 81 is repeatedly executed.

As can be understood from the above description of the operation, according to the above-described embodiment, the abnormality in the detection output of the yaw rate sensor 63 is detected based on the front wheel steering angle δf, and the steering angle δf is also detected.
Uses the output of the front wheel steering angle sensor 61 used for steering control of the left and right rear wheels RW1 and RW2, so that the abnormality detection can be realized with a simple configuration without complicating the electric control device C. . When this abnormality is detected, step 78
The yaw rate γ * for calculation of the target rear wheel steering angle δr * is not updated due to the non-processing of the above, and is maintained at the value before the abnormality, and when the output of the yaw rate sensor 65 returns to the normal state, the processing of steps 82 to 86 is performed. Since the calculation yaw rate γ * is gradually returned to the current detected yaw rate γ, in both cases, the target rear wheel steering angle δr * does not suddenly change, and the fail safe of the vehicle at the time of the abnormality occurrence. The function is realized, and the maneuverability of the vehicle does not deteriorate.

[Brief description of drawings]

1 is an overall schematic view of a front and rear wheel steering vehicle to which an abnormality detection device for yaw rate sensor output according to the present invention is applied, FIG. 2 is a flow chart of a program executed by the microcomputer of FIG. 1, FIG. FIG. 4 is a graph showing the change characteristics of the estimated maximum yaw rate and the change rate of the yaw rate stored in the ROM of FIG. 1, and FIGS. 5 and 6 are the first stored in the ROM of FIG. 3 is a graph showing change characteristics of the second coefficient. Explanation of symbols A ... front wheel steering device, B ... rear wheel steering device, C ... electric control device, FW1, FW2 ... front wheels, RW1, RW2 ... rear wheels, 61 ...
Front wheel steering angle sensor, 62 …… Vehicle speed sensor, 63 …… Yaw rate sensor, 64 …… Rear wheel steering angle sensor, 65 …… Microcomputer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroaki Tanaka, 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor: Shin Koike, 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. ( 72) Inventor Mizuho Sugiyama 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Kaoru Ohashi, Aichi Prefecture Toyota City, Toyota City, Toyota City, Ltd. (72) Inventor, Hitoshi Iwata, Aichi Prefecture Toyota-cho, Toyota-shi, Toyota Automobile Co., Ltd. (72) Inventor Masa Ishikawa Toyota-cho, Toyota-shi, Aichi Prefecture, Toyota-automobile, Ltd. (56) Reference JP-A-62-163868 (JP, A) Kaihei 1-229764 (JP, A)

Claims (1)

(57) [Claims] 1. A device for detecting an abnormality in an output of a yaw rate sensor mounted on a vehicle for detecting a yaw rate acting on a vehicle body, the front wheel steering speed detecting means for detecting a front wheel steering speed, and at least the detected yaw rate. The rate of change is
The yaw rate sensor output is characterized in that the yaw rate sensor output is determined to be abnormal when the estimated maximum yaw rate change speed, which is determined by the detected front wheel steering speed and increases as the front wheel steering speed increases, is exceeded. Abnormality detection device.