JPH06307989A - Abnormality detector for vehicle sensor - Google Patents

Abstract

PURPOSE:To detect abnormality in a vehicle sensor (yaw rate sensor) positively. CONSTITUTION:A sub-yaw rate sensor 31b is provided in addition to a main yaw rate sensor 31a and yaw rates gammaa, gammab detected by the sensors 31a, 31b are inputted to a microcomputor 35. The microcomputor 35 calculates the variation rates DELTAgammaa, DELTAgammab of the yaw rates gammaa, gammab and then determines the difference D(=¦DELTAgammaa¦-¦DELTAgammab¦). The microcomputor 35 decides that the main yaw rate sensor 31a is abnormal if the difference D is larger than a predetermined value epsilon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality detecting device for a vehicle sensor which is mounted on a vehicle and detects an abnormality of a vehicle sensor for detecting a motion state of the vehicle.

[0002]

2. Description of the Related Art Conventionally, an apparatus of this type is disclosed in, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Laid-Open No. 135980/1993, it is applied to a yaw rate sensor as a vehicle sensor for detecting a motion state of a vehicle, the change rate of the yaw rate detected by the sensor is calculated, and the change rate is calculated in advance. The abnormality of the yaw rate sensor is judged when it becomes larger than the predetermined value.

[0003]

However, in the above-mentioned conventional apparatus, if the predetermined value is set to a small value, even if the vehicle motion state changes suddenly, the vehicle sensor is normal, but There is a problem that the vehicle sensor is determined to be abnormal. On the contrary, if the predetermined value is set to a large value, there is a problem that even if the vehicle sensor is abnormal, the abnormality of the sensor is not detected. The present invention has been made to solve the above problem, and an object thereof is to provide an abnormality detection device for a vehicle sensor that accurately detects an abnormality of the vehicle sensor.

[0004]

In order to achieve the above object, a structural feature of the present invention is that a sub-sensor for detecting a motion state of a vehicle, which is the same as a vehicle sensor, and a vehicle sensor and a sub-sensor are provided. It is provided with a change rate calculation means for calculating the change rate of each of the detected values and a determination means for determining an abnormality of the vehicle sensor based on the degree of difference between the change rates.

[0005]

According to the present invention constructed as described above, a sub-sensor for detecting the same motion state of the vehicle as the vehicle sensor is provided, and the vehicle is determined depending on the degree of difference in the rate of change of each detected value between the two sensors. The sensor for abnormality is judged. Therefore, when the motion state of the vehicle suddenly changes, the change rates of the respective detection values of the both sensors suddenly change at the same time, and the abnormality of the vehicle sensor can be accurately detected. Moreover, since the change rate of each detected value is not affected by the offset amount of the detected value by the vehicle sensor, an inexpensive sensor with a large offset amount can be used as a sub sensor, and even if a sub sensor is provided, the cost is not so large. Does not bring high.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which a yaw rate sensor is used as a vehicle sensor according to the present invention will be described below with reference to the drawings. FIG. 1 schematically shows the entire four-wheel steering vehicle equipped with the sensor. This four-wheel steering vehicle has front left and right wheels FW1 and FW2.
Front wheel steering mechanism 10 for steering the vehicle and left and right rear wheels RW1, RW
A rear wheel steering mechanism 20 that steers 2 and an electric control device 30 that electrically controls the rear wheel steering mechanism 20 are provided.

The front wheel steering mechanism 10 is provided with a steering handle 11 for steering the left and right front wheels FW1 and FW2 by turning operation.
The handle 11 is fixed to the upper end of the steering shaft 12.
The lower end of the steering shaft 12 meshes with the rack bar 14 in the steering gear box 13. The rack bar 14 is supported in the steering gear box 13 so as to be displaceable in the axial direction, and has tie rods 15a, 1 at both ends.
The left and right front wheels FW1, FW2 are steerably connected via the 5b and the knuckle arms 16a, 16b.

The rear wheel steering mechanism 20 comprises an electric motor 21 as an actuator that is electrically controlled to steer the rear wheels. The rotating shaft of the electric motor 21 is connected to a relay rod 23 which is supported in the steering gear box 22 via a speed reduction mechanism so as to be displaceable in the axial direction. The rod 23 rotates in accordance with the rotation of the motor 21. Displace in the direction. Tie rods 2 are provided on both ends of the relay rod 23.
The left and right rear wheels RW1 and RW2 are connected to each other via the 4a and 24b and the knuckle arms 25a and 25b.
W1 and RW2 are steered according to the axial displacement of the relay rod 23.

The electric control unit 30 includes the main yaw rate sensor 3
1a and an auxiliary yaw rate sensor 31b are provided. Both yaw rate sensors 31a and 31b are incorporated in the same case near the center of gravity of the vehicle, and independently detect the yaw rate of the vehicle and output detection signals representing the yaw rates γa and γb. In this case, the auxiliary yaw rate sensor 31b
Is an inexpensive one with a large offset due to temperature,
The response of the sensor 31b is set slightly higher than that of the main yaw rate sensor 31a. The electric control device 30 also includes a vehicle speed sensor 32 that detects the vehicle speed V, a front wheel steering angle sensor 33 that detects the front wheel steering angle θf, and a rear wheel steering angle θr.
And a rear wheel steering angle sensor 34 for detecting In addition,
These yaw rate γ, front wheel steering angle θf and rear wheel steering angle θr
Indicates that the left rotation direction is positive and the right rotation direction is negative. These sensors 31a to 34 are connected to the microcomputer 35. The microcomputer 35 is a CPU, R
ROM including OM, RAM, I / O, timer, etc.
The main program corresponding to the flowchart of FIG. 2 stored therein is repeatedly executed to control the steering of the left and right rear wheels RW1 and RW2, and the interrupt program corresponding to the flowchart of FIG. The abnormality of the yaw rate sensor 31a is detected. A drive circuit 36 is connected to the microcomputer 35,
The drive circuit 36 is controlled by the computer 35 to control the rotation of the electric motor 21.

Next, the operation of the embodiment configured as described above will be described. When an ignition switch (not shown) is turned on, the microcomputer 35 executes step 1
The program execution is started at 00, the flag F is initialized to "0" at step 102, and then the step 104 is executed.
The process consisting of 114 is repeatedly executed. The flag F indicates an abnormal state of the main yaw rate sensor 31a by "1" and a normal state of the sensor 31a by "0".

At step 104, the flag F is "
It is determined whether or not it is 1 ". If the flag F is still set to" 0 "as described above, it is determined to be" NO "in step 104 and the program is executed in steps 106 to 1
Proceed to 12. In step 106, each sensor 3
1a, 32-34 input yaw rate γa, vehicle speed V, front wheel steering angle θf and rear wheel steering angle θr, respectively. In step 108, the steering angle proportional coefficient K1 that changes according to the vehicle speed V is read from the table provided in the ROM.
(See FIG. 3A) and the yaw rate proportional coefficient K2 (see FIG. 3A).
(See (B)). In step 110, the target rear wheel steering angle θr * is calculated by executing the calculation of the following formula 1.

[0012]

[Formula 1] θr * = K1 · θf + K2 · γ After the calculation of the target rear wheel steering angle θr *, the deviation θ between the target rear wheel steering angle θr * and the input rear wheel steering angle θr is calculated in step 112.
Calculate r * −θr and the calculated deviation θr * −θ
The control signal representing r is output to the drive circuit 36. The drive circuit 36 supplies a drive current corresponding to the control signal to the electric motor 2
1 to control the rotation of the motor 21 to rotate the electric motor 21 by an angle corresponding to the deviation θr * −θr. The rotation of the electric motor 21 is transmitted to the relay rod 23, and the rod 23 is displaced in the axial direction according to the rotation. The axial displacement of the relay rod 23 is transmitted to the left and right rear wheels RW1 and RW2 via the tie rods 24a and 24b and the knuckle arms 25a and 25b, and the rear wheels RW.
1, RW2 are steered to the target rear wheel steering angle θr *.

During execution of the processing consisting of steps 104 to 112, the microcomputer 35 interrupts and executes the interrupt program of FIG. 4 every predetermined time. In this interrupt program, the microcomputer 3
5 starts its execution at step 200, then step 2
At 02, the detection signals representing the yaw rates γa and γb are input from the main and auxiliary yaw rate sensors 31a and 31b, and at step 204, the old yaw rates γa2 and γb2 are changed to the new yaw rates γ.
a1 and γb1 are updated, and new yaw rates γa1 and γb1
To the input yaw rates γa and γb. next,
In steps 206 and 208, the change rates Δγa, γa, of the detected yaw rates γa, γb
Calculate Δγb.

[0014]

[Formula 2] Δγa = γa1−γa2

[0015]

## EQU3 ## Δγb = γb1−γb2 After calculation of these change rates Δγa and Δγb, step 210
By executing the calculation of the following equation 4, both change rates Δγa and Δγb
The difference D between absolute values | Δγa | and | Δγb |

[0016]

## EQU4 ## D = | Δγa | − | Δγb | Next, in step 212, the calculated difference D is compared with a predetermined positive value ε. In this case, if the main and sub yaw rate sensors 31a and 31b are normal, each detected yaw rate γ
The change rates Δγa and Δγb of a and γb are almost equal (see time t1 in FIG. 5). Specifically, the sub yaw rate sensor 31
Since the response of b is set slightly higher than that of the main yaw rate sensor 31a, the absolute value of the change rate Δγa | Δγa
| Is equal to the absolute value | Δγb | of the rate of change Δγb or is slightly smaller than the absolute value | Δγb | of the rate of change Δγb. Therefore, in step 212, it is determined that "NO", that is, the difference D is smaller than the predetermined value ε, and the execution of the interrupt program is ended in step 216. As a result, the flag F
Is maintained at "0", the processes of steps 104 to 112 of the main program are repeatedly executed, and the left and right rear wheels RW1 and RW2 are continuously steered to the target rear wheel steering angle θr *.

On the other hand, when an abnormality occurs in the main yaw rate sensor 31a, the absolute value | Δγa | of the rate of change Δγa of the yaw rate γa detected by the sensor 31a may become larger than the absolute value of the actual rate of change of the yaw rate. . In this case, the difference D from the absolute value | Δγb | of the rate of change Δγb of the yaw rate γb detected by the sub-yaw rate sensor 31b becomes large, and "YES" in the above step 212.
That is, it is determined that the difference D is larger than the predetermined value ε and the program proceeds to step 214. In step 214, the flag F is changed to "1", and then step 216
Ends the execution of the interrupt program. This allows
In step 104 of the main program in FIG. 2, "YE
S ”, the program proceeds to step 114, and the fail process is executed at step 114. In this fail process, a warning lamp is turned on, a warning buzzer is sounded, steering of the left and right rear wheels RW1, RW2 is stopped, and the rear wheels RW1, RW2 are returned to the neutral position. Further, the left and right rear wheels RW1 and RW2 are steering-controlled based on the detected yaw rate of the absolute value | Δγa | You may

As can be understood from the above description of the operation, according to the above embodiment, the main and auxiliary yaw rate sensors 31a, 31a,
Yaw rates γa and γb respectively detected by 31b
Absolute values of change rates Δγa and Δγb of | Δγa | and | Δγb |
Since the abnormality of the main yaw rate sensor 31a is determined based on the difference D between them, the absolute value | Δγa of both the change rates Δγa and Δγb when the motion state of the vehicle suddenly changes.
Also, | and | Δγb | will suddenly change at the same time, and the abnormality of the main yaw rate sensor 31a can be accurately detected. The change rates Δγa and Δγb are the yaw rates γa and
Since it does not depend on the offset amount of γb (see FIG. 5),
An inexpensive sensor having a large offset amount due to temperature characteristics or the like can be used as the sub yaw rate sensor 31b.

In the above embodiment, the rate of change Δγa in the yaw rate γa detected by the main yaw rate sensor 31a.
Is smaller than the absolute value | Δγb | of the rate of change Δγb of the yaw rate γb detected by the sub-yaw rate sensor 31b, the main yaw rate sensor 31a is abnormal because the influence on the vehicle steerability is small. However, even in this case, if the difference between the absolute values | Δγa | and | Δγb | of the two change rates Δγa and Δγb is large, it may be determined that the main yaw rate sensor 31b is abnormal. In order to realize this, in step 212, when the absolute value | D | of the difference D calculated in the processing of step 210 becomes larger than the predetermined value ε, it is determined that the main yaw rate sensor 31a is abnormal. Good.

In the above embodiment, the responsiveness of the auxiliary yaw rate sensor 31b is set slightly higher than that of the main yaw rate sensor 31a.
The responsiveness of 31b may be made equal. In addition,
Also in this case, as described above, the difference D
It is also possible to determine that the main yaw rate sensor 31a is abnormal when the absolute value | D | In addition, the difference between both change rates Δγa and Δγb is Δγa−Δγb
When the absolute value | Δγa−Δγb | of the above becomes larger than the predetermined value ε, the abnormality of the main yaw rate sensor 31a may be determined.

Further, in the above embodiment, the embodiment in which the present invention is applied to the main yaw rate sensor 31a for detecting the yaw rate as the motion state of the vehicle has been described.
The present invention may be applied to a sensor that detects lateral acceleration, longitudinal acceleration, etc. of the vehicle as the same motion state.

[Brief description of drawings]

FIG. 1 is an overall schematic view of a four-wheel steering vehicle to which the present invention has been applied.

FIG. 2 is a flowchart corresponding to a main program executed by the microcomputer of FIG.

FIG. 3A is a change characteristic diagram of a steering angle proportional coefficient with respect to a vehicle speed, and FIG. 3B is a change characteristic diagram of a yaw rate proportional coefficient with respect to a vehicle speed.

4 is a flowchart corresponding to an interrupt program executed by the microcomputer of FIG.

5 is a time chart showing a yaw rate detected by a main yaw rate sensor and a yaw rate detected by a sub yaw rate sensor, a difference between change rates of both yaw rates, and a temporal change of a flag indicating abnormality of the main yaw rate sensor.

[Explanation of symbols]

FW1, FW2 ... front wheels, RW1, RW2 ... rear wheels, 10 ...
Front wheel steering mechanism, 20 ... Rear wheel steering mechanism, 30 ... Electric control device, 31a ... Main yaw rate sensor, 31b ... Sub yaw rate sensor, 32 ... Vehicle speed sensor, 33 ... Front wheel steering angle sensor,
34 ... Rear wheel steering angle sensor, 35 ... Microcomputer.

Claims (1)

[Claims] 1. An abnormality detection device for a vehicle sensor, which is mounted on a vehicle and detects an abnormality of a vehicle sensor for detecting a movement state of the vehicle, wherein the same movement state of the vehicle as the vehicle sensor is detected. And a change rate calculating means for calculating a change rate of each detected value by the vehicle sensor and the sub sensor, and a determining means for determining an abnormality of the vehicle sensor according to a degree of difference between the two change rates. An abnormality detection device for a vehicle sensor, comprising: