JPH02231273A - Rear wheel steering controller for front/rear wheel steered vehicle - Google Patents

Abstract

PURPOSE:To always carry out the proper rear wheel steering control and facilitate steering by detecting the anomaly of a car speed detecting means and selecting two kinds of aimed rear wheel steering angle having different characteristic according to the case when anomaly is detected or not and controlling the steering for rear wheels. CONSTITUTION:The car speed and front wheel steering angle are detect by sensors 1 and 2, and the anomaly of the means 1 is detected by a means 3. In this case, if the anomaly of the means 1 is not detected, the reverse phase steering for front wheels in a low car speed region and the equal phase steering for front wheels in a high car speed region are represented, and the first aimed rear wheel steering angle which increases with the increase of the front wheel steering angle is determined by a means 4. When the anomaly of the means 1 is detected, the second aimed rear wheel steering angle in which the equal phase steering for front wheel in a small steering angle region of the front wheel and the reverse phase steering in a large steering angle region are represented is determined by a means 5. Rear wheels RW are steering-controlled by a means 6 according to each determined aimed rear wheel steering angle.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention steers the rear wheels in proportion to the steering of the front wheels, and also adjusts the steering direction of the rear wheels in accordance with the vehicle speed (in a direction opposite to the # wheel). This invention relates to a rear wheel steering control device for a front and rear wheel steered vehicle that changes and controls the front and rear wheels (in-phase direction). (Prior art) Conventionally, this type of device has been disclosed, for example, in Japanese Patent Application Laid-Open No. 60-78870.
As shown in the publication, based on the vehicle speed detected by the vehicle speed detecting means and the front wheel steering angle detected by the front wheel steering angle detecting means, it indicates reverse phase steering for the front wheels in a low vehicle speed region, and indicates reverse phase steering for the front wheels in a high vehicle speed region. By determining a target rear wheel steering angle that represents in-phase steering and increasing as the front wheel steering angle increases, and controlling the rear wheels to the determined target rear wheel steering angle, the vehicle's tight turning performance at low speeds and high speeds can be improved. In addition to improving the running stability of the vehicle during running, an abnormality detection means for detecting an abnormality in the vehicle speed detection means is provided, and when an abnormality in the vehicle speed detection means is detected by the abnormality detection means, the rear wheel Steering control is stopped to maintain the rear wheel steering angle at zero. (Problem to be Solved by the Invention 1) However, in the above-mentioned conventional device, the influence of the rear wheel steering control on the steering stability of the vehicle is too large depending on whether the vehicle speed detection means is normal or abnormal. Unfavorable.For example, when changing lanes while driving at high speed, if the vehicle speed detection means is normal, the yaw rate acting on the vehicle body will be suppressed by in-phase steering of the rear wheels, but if an abnormality occurs in the vehicle speed detection means, the yaw rate of the rear wheels will be suppressed. Since the steering angle is kept at zero, the yaw rate is not suppressed, making it difficult for drivers who are accustomed to vehicles where the yaw rate is suppressed to control the vehicle.Also, it is difficult to maneuver the vehicle while driving at low speed. If the vehicle speed detection means is normal, the turning radius of the vehicle will be reduced by reverse phase steering of the rear wheels, but if an abnormality occurs in the vehicle speed detection means, the steering angle of the rear wheels will be kept at zero. As a result, the turning radius of the vehicle increases, making it difficult for drivers who are accustomed to vehicles with a small turning radius to maneuver the vehicle. The M
It is an object of the present invention to provide a rear wheel steering III# device for a front and rear wheel steered vehicle, which controls the steering of the rear wheels so that the vehicle can be easily maneuvered. (Means for Solving Problem 1) In order to achieve the above object, the structural features of the present invention are as follows.
As shown in the ffil diagram, vehicle speed detection means 1 detects the vehicle speed, and front wheel steering angle detection means 2 detects the front wheel steering angle.
and an abnormality detection means 3 for detecting an abnormality in the vehicle speed detection hand Pi1.
When an abnormality in the vehicle speed detection means 1 is not detected by the abnormality detection means 3, it represents anti-phase steering for the front wheels FW in a low vehicle speed region, represents in-phase steering for the front wheels FW in a high vehicle speed region, and as the front wheel steering angle increases. An abnormality in the vehicle speed detecting means 1 is detected by the target rear wheel steering angle determining means 4 and the abnormality detecting means 3, which determines the target rear wheel steering angle to be increased based on the pre-detection steering angle and the detected vehicle speed. When a small steering angle region of the front wheels FW represents in-phase steering with respect to the front wheels FWI; and a large steering angle region of the front wheels FW represents inverse phase steering with respect to the front wheels FW. the second target rear wheel steering angle determining means 5, and the first target rear wheel steering angle determining means 4 or the second target rear wheel steering angle determining means 4, or the second target rear wheel steering angle determining means 4 or the second target rear wheel steering angle determining means 4; A steering control means 6 is provided to control the steering of the rear wheels RW to the target rear wheel steering angle determined by the S rear wheel steering angle determination means 5. Effects of the Invention In the present invention configured as described above, when the abnormality detection means 3 does not detect an abnormality in the vehicle speed detection means 1, the first target rear wheel steering angle determination means 4
and the front wheel steering angle detecting means 2, it represents anti-phase steering for the front wheels FW in a low vehicle speed region, represents in-phase steering for the front wheels FW in a high vehicle speed region, and also represents a target steering angle that increases as the front wheel steering angle increases. After determining the wheel steering angle, the steering control means 6 controls the rear wheels RW to the target rear wheel steering angle, so that when changing lanes at high speed, the rear wheels RW are in the same phase as the front wheels FW. When the rear wheels RW are steered in the opposite direction and the vehicle is to make a small turn while traveling at low speed, the rear wheels RW are steered in the opposite phase. On the other hand, in a state in which an abnormality in the vehicle speed detection means 1 is detected by the abnormality detection means 3, the second target rear wheel steering angle determination means 5 determines the small steering angle of the front wheels FW by 14@ with the front wheel steering angle detection means 2. Determine a target rear wheel steering angle that represents in-phase steering for the front wheels FW in the area and represents anti-phase steering for the front wheels FW in the large steering angle area of the front wheels FW, and steer! The control means 6 controls the steering of the rear wheels RW to the target rear wheel steering angle, but when changing lanes while driving at high speed, the steering angle of the front wheels FW is usually small, so the rear wheels RW are steered in the same phase. Being stabbed. Also, when the vehicle is making a small turn while driving at low speed, the steering angle of the front wheels FW is usually large, so the steering angle of the rear wheels RWD is usually large.
is steered out of phase. [Effects of the Invention] As can be understood from the above description of the operation, according to the present invention, the steering characteristics of the rear wheels RW are not very large in the normal running state of the vehicle, regardless of whether the vehicle speed detection means 1 is normal or abnormal. Since it does not change, it becomes easier for the driver to control the vehicle. [Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. Second
The figure schematically shows the entire front and rear wheel steering vehicle according to the present invention. B, and an electric control device C that electrically controls the rear wheel steering device B. The front wheel steering device A is displaced in the axial direction to control the left and right front wheels FWl, F.
It has a rack par 11 for steering W2. The rack par 11 is connected to the lower end of a steering shaft 14 which has a steering handle 13 connected to its upper end in the gear box 12, and has left and right tie rods 15a,
The left and right front wheels FWI and FW2 are steerably connected via the left and right knuckle arms 16a and 16b. The rear wheel steering device B has a relay rod 22 that is driven in the axial direction by a power cylinder 21 to steer the left and right rear wheels RWI, RW2, and the relay rod 22 has left and right tie rods 23a, 23b and The left and right rear wheels RWI, RW2 are steerably connected via left and right knuckle arms 24a, 24+. The power cylinder 21 has left and right oil chambers 2lb, 21c separated by a piston 21a fixed to a relay rod 22, and a servo valve 25 is connected to each oil chamber 2lb, 21c. This servo valve 25 is controlled by an electric control device C to supply hydraulic oil from a hydraulic pump 26 to one oil chamber, and discharge hydraulic oil in the other oil chamber to a reservoir 27. The electric control device C has a front wheel steering angle sensor 31, a rear wheel steering angle sensor 32, and a vehicle speed sensor 33. The front wheel steering angle sensor 31 outputs a front wheel steering angle signal representing the steering angle δf of the left and right front wheels FWI, FW2 by detecting the rotation angle of the steering shaft 14 or the amount of axial displacement of the rack par 11. The rear wheel steering angle sensor 32 detects the displacement amount of the relay rod 22 in the axial direction, thereby adjusting the left and right rear wheels RWI,
Outputs a rear wheel steering angle signal representing the steering angle δr of RW2.
Note that both the front wheel steering angle δf and the rear wheel steering angle δr are positive, indicating steering to the right, and negative, indicating steering to the left. Vehicle speed sensor 33 outputs a vehicle speed signal representing vehicle speed V by detecting the rotational speed of an output shaft of a transmission (not shown). The outputs of the front wheel steering angle sensor 31 and the vehicle speed sensor 33 are connected to a microcomputer 34, and the computer 34 has a ROM 34b connected to a bus 34a.
．． It consists of a CPU 34c, a RAM 34d, and an input/output interface (hereinafter simply referred to as I/O) 34e. ROM
34b stores a program corresponding to the flowchart in FIG. 3, and also stores a vehicle speed corresponding steering angle ratio Kυ representing the ratio of the steering angles of the left and right rear wheels RWI, RW2 and the left and right front wheels FWI, FW2, and the steering angle ratio of the left and right rear wheels RWI, RW2. The rear wheel steering angle δrt corresponding to the steering angle, which represents the steering angle, is stored in the form of a table. As shown in the graph in Figure 4, the vehicle speed corresponding steering angle ratio Ku continuously changes from a negative value (corresponding to out-of-phase steering) to a positive value (corresponding to in-phase steering) as the vehicle speed increases. It is.
As shown in FIG. 5, the rear wheel steering angle δr' corresponding to the steering angle changes sinusoidally as the amount of left and right front wheels FWI, FW2 is steered in the left-right direction, that is, the absolute value of the front wheel steering angle δf increases. When the absolute value of the front wheel steering angle δf is small, the left and right rear wheels R in the same phase direction with respect to the left and right front wheels FWI, FW2.
It represents the steering angle of the left and right rear wheels RWI, RW2, and when the absolute value is large, it represents the steering angle of the left and right rear wheels RWI, RW2 in the opposite phase direction with respect to the left and right front wheels FWI, FW2. The CPU 34c executes the program. R
AM34d temporarily stores variable data necessary for executing the program. I/034e is composed of an A/D converter, a D/A converter, a memory circuit, etc., and receives detection signals from the front wheel steering angle sensor 31 and vehicle speed sensor 33, and also outputs the left and right rear wheel RWI, R
A control signal for controlling the steering of W2 is output to the non-inverting input (+) of the differential amplifier 35. A rear wheel steering angle sensor 32 is connected to the inverting input (1) of the differential amplifier 35, and the amplifier 35 controls the servo valve 25 in feedback. Next, the operation of the embodiment configured as described above will be explained. When the vehicle is running and the steering handle 13 is rotated, the rotation is transmitted to the rack bar 11 via the steering shaft 14 and the gear box 12, and the bar 11 is rotated in response to the rotation of the steering handle 13. displacement in the axial direction. This displacement of the rack par 11 is transmitted to the left and right front wheels FWI, FW2 via the left and right tie rods 15a, 15b and the left and right knuckle arms 16a, 18b.
is steered in the left and right directions according to the rotation of the steering handle 13. On the other hand, in such a state, when the ignition switch (not shown) is opened, the CPU 34c
Execution of the program is started at step 40 in the figure, and after initial setting of various data at step 41, a circular process consisting of steps 42 to 48 is repeatedly executed. In this w-ring process, the new vehicle speed data vN is updated by setting the new vehicle speed data vN as the old vehicle speed data Vo in step 42, and the vehicle speed signal from the vehicle speed sensor 33 is updated via ■/034e in step 43. At the same time, the front wheel steering angle signal from the front wheel steering angle sensor 31 is taken in and stored as new vehicle speed data ■9.
0 3 4 e and is revised and stored as front wheel steering angle data δf. In addition, new vehicle speed data vI
1 represents the current vehicle speed V, and the old military speed data Vo represents the vehicle speed ■ before one cycle of the circulation process consisting of steps 42-48. Next, in step 44, an abnormality detection process is performed to determine whether the vehicle speed sensor 33 is operating normally or not, based on, for example, the following conditions. ■Based on the new vehicle speed data VN and the old vehicle speed data Vo, both data Vs. If the difference in V o shows a value so large that it is impossible for the vehicle to run, it is determined that the vehicle speed sensor 33 is abnormal, and if not, it is determined that the sensor 33 is normal. ■If the new vehicle speed data VN shows a value that is impossible for the vehicle to run, it is determined that the vehicle speed sensor 33 is abnormal, and if not, it is determined that the sensor 33 is normal. If it is determined in the determination process in step 44 that no abnormality has occurred in rNOJ, that is, in the vehicle speed sensor 33, the table in the ROM 34b is referred to in step 45, and the steering angle ratio corresponding to vehicle speed KLI is determined based on the new vehicle speed data vN. (4th
In step 46, a target rear wheel steering angle δr is determined by multiplying the derived vehicle speed corresponding steering angle ratio Ku by the single wheel steering angle data δf, and in step 47, a target rear wheel steering angle δr is determined. The steering signal representing the steering angle δr vehicle is I/03
4 via e. difference. Non-inverting input (+) of dynamic amplifier 35
is supplied to The differential amplifier 35 feedback-controls the servo valve 25 in response to a detection signal representing the rear wheel steering angle δr from the rear wheel steering angle sensor 32. As a result, the servo valve 25 operates on the power cylinder 2 in response to the control signal from the differential amplifier 35.
The power cylinder 21 controls the supply and discharge of hydraulic oil to the left and right oil chambers 21b and 21c of the left and right oil chambers 21b and 21c.
Since the relay rond 21 is controlled so that the steering angle δr of the rear wheels becomes the target rear wheel steering angle δr, the rear wheels RWI, RW
2, the left and right tie rods 23a, 23b are connected by the same rod 21.
The rear wheels are then steered to the target rear wheel steering angle δr via the left and right knuckle arms 24a and 24b. In such a case, the steering angle ratio Ku corresponding to the vehicle speed is set to change from negative to positive as the vehicle speed ■ increases, and the target rear wheel steering angle δr* is set to change from the left and right front wheels FWI, FW2 in the low vehicle speed region.
Represents reverse phase steering, and at high vehicle speed
Since this represents in-phase steering for FWI and FW2, the left and right rear wheels RWI and RW2 represent the left and right front wheels FWI at low vehicle speeds.
, FW2 are steered in the opposite phase, and at high vehicle speeds, the same front wheels FW1 and FW2 are steered in the same phase. This improves the turning performance of the vehicle when making small turns at low speeds, and at the same time improves the running stability of the vehicle when changing lanes at high speeds. In addition, if the determination process in step 44 is "rYES", that is, it is determined that an abnormality has occurred in the vehicle speed sensor 33, the table in the ROM 34b is referred to in step 48, and the steering angle is determined based on the front wheel steering angle data δf. A corresponding rear wheel steering angle δr+ (see FIG. 5) is derived and the steering angle δr+
is determined as the target rear wheel steering angle δr*. After determining the target rear wheel steering angles δr, the same process as in the above case is executed in step 47, and the left and right rear wheels RWI, RW2 are controlled by the rear wheel steering angle sensor 32, the M dynamic amplification n35. Based on the same stabilization as described above by the servo valve 25 and the power cylinder 21, the vehicle is steered to the target rear wheel steering angle δr*, that is, the rear wheel steering angle δr+ corresponding to the steering angle. In such a case, the rear wheel steering angle corresponding to the steering angle δr+ is set to a value that steers the left and right rear wheels RW1, RW2 in the same phase with the left and right front wheels FWI, FW2 in a region where the absolute value of the curved wheel steering angle δf is small. In areas with large absolute values, the same rear wheel RWI and RW2 are the same front wheel FWI.
．． Since the value is set to steer in the opposite phase to FW2, when the left and right front wheels FWI, FW2 are steered by a large steering angle at low speed to turn the vehicle in a small direction, the left and right rear wheels RWI. RW2 is steered in the opposite phase to the front wheels FWI, FW2, and when the left and right front wheels FW1, FW2 are steered by a small steering angle at high speed to cause the vehicle to change lanes, the left and right rear wheels RWI, RW are steered in the opposite phase.
2 will be steered in the same phase with the same front wheels FWI and FW2. As a result, the steering of the left and right rear wheels RWI, RW2 is the same as when no abnormality occurs in the vehicle speed sensor 33, and the driver can drive the vehicle with almost the same feeling whether the vehicle speed sensor 33 is normal or abnormal. It becomes like this.

[Brief explanation of the drawing]

11 is a claim correspondence diagram corresponding to the structure of the present invention described in the above claims, FIG. 2 is an overall schematic diagram of a front and rear wheel steered vehicle showing an embodiment of the present invention, and FIG. 3 is a diagram corresponding to FIG. FIG. 4 is a graph showing the characteristics of the steering angle ratio corresponding to the vehicle speed, and FIG. 5 is a graph showing the characteristics of the rear wheel steering angle corresponding to the steering angle. Code A...front wheel steering device, C...electric stabbing device, wheel. RWI, RW2・Steering angle sensor, 32・3...Vehicle speed sensor, user. Description B... Rear wheel steering device, FWI, FW2... Front... Rear wheel, 31... Front wheel... u&fI1 steering angle sensor, 3 34... Micro combination Figure 1

Claims (1)

[Scope of Claims] Vehicle speed detection means for detecting vehicle speed; front wheel steering angle detection means for detecting a front wheel steering angle; abnormality detection means for detecting an abnormality in the vehicle speed detection means; and detecting the vehicle speed by the abnormality detection means. When an abnormality in the means is not detected, the detected front wheel steering angle represents anti-phase steering for the front wheels in a low vehicle speed region, represents in-phase steering for the front wheels in a high vehicle speed region, and sets a target rear wheel steering angle that increases as the front wheel steering angle increases. a first target rear wheel steering angle determination unit that determines the target rear wheel steering angle based on the angle and the detected vehicle speed; and when the abnormality detection unit detects an abnormality in the vehicle speed detection unit, performs in-phase steering for the front wheels in a small steering angle region of the front wheels. a second target rear wheel steering angle determining means for determining a target rear wheel steering angle representing reverse phase steering for the front wheels in a large front wheel steering angle region based on the detected front wheel steering angle; and a steering control means for controlling the steering of the rear wheels to the target rear wheel steering angle determined by the steering angle determining means or the second target rear wheel steering angle determining means. Wheel steering control device.