JPH0481364A - Controller for front/rear wheel-steering vehicle - Google Patents

Abstract

PURPOSE:To obtain superior maneuvering stability independently of the imbalance of load by calculating the output value to a rear wheel steering angle applying means on the basis of the difference between the aimed rear wheel steering angle and actual steering angle and the integration calculation value which is obtained by integration-calculating the difference. CONSTITUTION:A front wheel steering angle detecting means C, car speed detecting means D and a rear wheel steering angle detecting means E are installed, and the aimed rear wheel steering angle is calculated by a means F according to the detected steering angle quantity and the car speed. The difference between the calculated aimed rear wheel steering angle and the actual rear wheel steering angle is obtained by a difference calculating means G, and after the difference is integration-calculated by a difference integration calculating means H, the load neutral point is calculated by a load neutral point calculating means J, and the output value to the rear wheel steering angle applying means A is calculated by an output value calculating means K on the basis of the difference and the load neutral point.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a control device for a front and rear wheel steered vehicle that controls the steering of the rear wheels according to the steering state of the front wheels.

[Prior Art 1] Conventionally, as a control device for such a vehicle with front and rear wheel steering, the one described in Japanese Patent Application Laid-open No. 141877/1987 is known.

This system uses sensors to detect the steering status and vehicle speed of the front wheels, determines the rear wheel target steering angle corresponding to the detected results, and then detects the rear wheel steering angle using the sensor. By comparing the actual steering angle and the target steering angle, the rear wheels are steered by a motor via a worm reducer with a reversal efficiency of O or less so that the error becomes zero.

[Problem to be solved by the invention] However, in such a conventional example, the reversal efficiency of the rear wheel steering actuator is 0, that is, even if there is an input from the rear wheel side, the motor shaft side is not affected. Therefore, if there are variations in parts when assembling the rear wheel suspension or steering system to the vehicle, or if there is an imbalance in the vehicle weight due to the occupants, the actual rear wheel suspension in the neutral position The magnitude of the load on the left and right sides is different,
There is a problem in that the so-called steering angle neutral and load neutral do not match, and as a result, the steering stability of the vehicle is adversely affected.

In other words, since the rear wheel steering control is performed based on the neutral position of the rear wheels, the steering response differs when steering to the right and when steering to the left during a turn, which adversely affects steering performance. There was also the problem that it gave the driver a sense of discomfort.

It is an object of the present invention to solve such conventional problems and to provide a front and rear wheel steering vehicle that does not give the driver a sense of discomfort even when there is load imbalance due to variations in parts, etc., and has excellent steering stability. The purpose of this invention is to provide a control device.

[Means for Solving the Problems 1] In order to achieve the above object, the present invention provides a rear wheel steering angle applying means for applying a predetermined steering angle to the rear wheels, and a front wheel steering angle detection device for detecting the steering angle of the front wheels. means, vehicle speed detection means for detecting the vehicle speed of the vehicle, and rear wheel steering angle detection means for detecting the steering angle of the rear wheels;
Rear wheel steering angle target value calculation means for calculating a target steering angle of the rear wheels according to the steering angle amount determined by the front wheel steering angle detection means and the vehicle speed determined by the vehicle speed detection means; and the rear wheel steering angle target value calculation means. error calculation means for calculating the error between the rear wheel target steering angle calculated by the rear wheel steering angle and the rear wheel actual steering angle determined by the rear wheel steering angle detection means; and an error integration unit for integrating the error calculated by the error calculation means. means, load neutral point calculating means for calculating a load neutral point of the vehicle based on the integral value by the error integrating means, and an output for calculating an output value to the rear wheel steering angle applying means based on the error and the load neutral point. The present invention is characterized by comprising a value calculation means.

[Operation 1] According to the present invention, the error between the target steering angle and the actual steering angle of the rear wheels is calculated, and this error is further integrated by the integrating means. Furthermore, the load neutral point is determined by the load neutral point calculating means based on this integral value.

Then, based on this load neutral point and the above-mentioned error, an output value to the rear wheel steering angle applying means is calculated.

Therefore, it is possible to perform rear wheel steering control using an output value that takes this load neutral point into consideration, so even if there is an imbalance between the left and right loads, the actual load will be adjusted every time the vehicle is used. The vehicle will be controlled by taking the neutral point into consideration, and you will be able to drive in a way that feels strange.

[Embodiment 1] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block configuration diagram showing one embodiment of the present invention, in which A is a rear wheel steering angle applying means that applies a predetermined steering angle to the rear wheel B, and C is a front wheel steering device that detects the steering angle of the front wheels. Angle detection means, D is a vehicle speed detection means for detecting the vehicle speed, and E is a rear wheel B.
This is rear wheel steering angle detection means for detecting the steering angle of the rear wheel. F is a rear wheel steering angle target value calculation means that calculates a target steering angle of the rear wheel B according to the steering angle amount determined by the front wheel steering angle detection means C and the vehicle speed determined by the vehicle speed detection means, and G is a rear wheel steering angle target. Error calculation means for calculating the error between the rear wheel target steering angle calculated by the value calculation means F and the rear wheel actual steering angle determined by the rear wheel steering angle detection means E; H is the error calculated by the error calculation means G; K is an output value calculating means that calculates an output value to the rear wheel steering angle applying means A based on the error and the load neutral point.

Next, FIG. 2 is a system configuration diagram showing an embodiment of the present invention. In the diagram, l is an on-vehicle battery, 2 is an ignition switch, 3 is a steering angle sensor, and a steering wheel (not shown) is connected to the steering wheel. Generates a signal proportional to the steering angle and a neutral position signal. 4 is a vehicle speed sensor that detects the vehicle speed; 5 is a brake switch that is turned on in response to depression of the brake pedal; 6 is a stop lamp that lights up when the brake switch 5 is turned on; and 7 is when a clutch is connected or disconnected from the drive system. A clutch switch is turned on, and 8 is a warning lamp.

Next, reference numeral 9 indicates a rear wheel steering actuator, and in this embodiment, a steering motor 9A for imparting a predetermined amount of steering angle to the rear wheels (not shown) and a steering motor 9A are used. A limiting motor 9 for driving a mechanism that reduces the applied steering amount by a predetermined ratio and limits the maximum steering angle of the rear wheels.
It is equipped with B. Note that this restriction mechanism will be explained in detail later.

A sensor 9C serves as rear wheel steering angle detection means and detects displacement of an operating rod, which will be described later, corresponding to the amount of rotation of the motor 9A.
1, and a sensor 9D is provided as a ratio detection means for detecting a relative angle of a cam groove, which will be described later, corresponding to the amount of rotation of the motor 9B.

10 is a control unit that sends drive signals for the steering motor 9A and the limiting motor 9B based on the input signals of the various sensors described above;
A micro combinator IOA equipped with M10A and RAM10A, a power supply circuit 10B for the microcomputer 10A, and a power supply circuit 10B for the microcomputer 10A, which sends signals from the steering angle sensor 3, vehicle speed sensor 4, brake switch 5, and clutch switch 7 to the microcomputer 10A. An input I/F circuit 10G that converts into an input signal, an output I/F circuit 100 to the warning lamp 8, a motor drive circuit 10E that drives both motors 9A and 9B, and detection sensors 9C and 9D.
power supply circuit 10F and detection sensors 9C and 9D for
Analog human input I/F circuit 1 into which the analog signal of
0G, and an A/D conversion circuit 10H that converts the signal of the analog input I/F circuit 10G into digital.

Next, the aforementioned limiting mechanism will be explained with reference to FIG.

In the figure, reference numeral 20 denotes an actuating rod that is supported via a bearing in a housing (not shown) attached to the vehicle body so as to be movable along its axis. Both ends of the operating rod 20 are connected to knuckle arms (not shown) via ball joints and tie rods 21 to steer the rear wheels.

Reference numeral 30 denotes a cylindrical member that is rotatably supported by a housing (not shown) with a bearing around a rotation axis L2 perpendicular to the axis L1. 31 is press-fitted and fixed. A worm wheel 31 is meshed with a worm pinion 32 driven by the above-mentioned limiting motor 9B fixed to the housing.

Reference numeral 40 designates an eccentric cam member which is rotatably supported by the housing with a bearing around the rotational axis L2, and a worm wheel 41 is press-fitted and fixed to the outer periphery of the eccentric cam member. An eccentric cam 42 is protruded from the lower end surface of the eccentric cam member 40 at a position offset by a predetermined distance from the rotation axis L2. A worm wheel 41 is meshed with a worm pinion 43 driven by the aforementioned steering motor 9A fixed to the housing.

Reference numeral 50 denotes a slider member that is slidably supported by guide rods 33 and 33 installed along the diameter of the cylindrical member 30. A cam groove 50A is provided on the upper side of the slider member 50 in a direction perpendicular to the guide rods 33, 33, and the aforementioned eccentric cam 42 is engaged with the groove 50A via a needle bearing 44.

Furthermore, a driving protrusion 51 is provided protruding from the lower surface of the slider member 50.

Furthermore, 22 is a fixed block member fixed to the operating rod 20 with bolts, and the upper side thereof has a cam groove 22A extending in a direction orthogonal to the axis L1 of the operating rod 20.
is provided. The drive protrusion 51 of the slider member 50 described above is engaged with this cam groove 22A via a needle bearing 52.

In this embodiment having the above configuration, the rotation angle of the cylindrical member 3Q and, by extension, the slider member 50, that is, the cam groove 22A of the fixed block member 22 fixed to the actuating rod 20
The relative angle between the cam groove 50A of the slider member 50 and the cam groove 50A of the slider member 50 can be changed by driving the limiting motor 9B. When the relative angle between the cam groove 50A and the cam groove 22A is 90°, the amount of steering angle due to the rotation of the steering motor 9A is
0 is not transmitted. That is, the circular movement of the eccentric cam 42 of the eccentric cam member 40 about the rotation axis L2 via the worm binion 43 and the worm wheel 41 shown in FIG. is converted into a movement in the direction of the guide rod 33.3
Since the axial direction of No. 3 coincides with the direction of the cam groove 22A, the drive protrusion 51 only moves within the cam groove 22A, and the fixed block member 22 and, by extension, the actuating rod 20 do not move.

Conversely, the relative angle between the cam groove 50A and the cam groove 22A is O.
At the time of o, the amount of steering angle due to the rotation of the steering motor 9A is all transmitted as a movement of the actuating rod 20 in the direction along the axis L1.

Next, an example of the control procedure of this embodiment will be explained with reference to the flowchart of FIG. 4.

First, when the control starts, the steering angle θ1 of the front wheels by the steering angle sensor 3 is read in step S1, and the vehicle speed ■ by the vehicle speed sensor 4 is read in step S2.

Then, in step S3, the steering angle θ is determined.

A target value θ of the rear wheel steering angle is calculated from the vehicle speed and the vehicle speed. Next, in step S4, the actual steering angle θ8 of the rear wheels detected by the rear wheel steering angle detection sensor 9C is read, and the target steering angle θ is determined.
, and the error θ between the actual steering angle θ8.

but, θ,=θ,-07 is calculated in step S5.

Furthermore, in step S6, the error θ. integral value SU
M is SUN = SUM 10.

It is calculated as

Next, in step S7, the steering angle Fc at the neutral point of the load is calculated using the following formula. That is, Fc=*SUN where n is a constant determined depending on the suspension type, vehicle weight, etc.

Then, in step S8, the load neutral point steering angle Fc
The difference e between the actual steering angle θ8 of the rear wheels and the rear wheel actual steering angle θ8 is obtained as e=Fc-08.

In step S9, it is determined whether this difference e is positive or negative. If the difference e is positive or O, step S10
Proceed to. If the difference e is negative, the process advances to step Sll.

Now, to explain the above-mentioned positive/negative relationship using Fig. 5, when looking at the vehicle from above, if the rear wheels are steered to the right, it is positive, and if the rear wheels are steered to the left, it is negative. shall be.

FIG. 5 is a characteristic diagram showing the relationship between the shaft torque of the steering motor 9A required to steer the rear wheels and the rear wheel steering angle, (A)
(B) is the case where the load center and the steering angle center (steering angle = 0) match, and (B) is the case where they deviate.

Here, when the rear wheel steering angle is returned to the neutral position, the shaft torque of the motor is small due to the relationship with the road reaction force.
When steering in the opposite direction, it is necessary to

Therefore, in step S9 described above, the fact that the difference e is positive means that the rear wheel actual steering angle θ8 exists to the left of the load center steering angle Fc in FIG. 5(B). . Furthermore, the error θ in step SIO is 0
The above means that the actual steering angle θ3 is still insufficient with respect to the target steering angle θ1, and in this case, the shaft torque shown by the straight line XL is required.

Therefore, in this case, the process proceeds to step S12, and the larger gain difference is selected from Table 1 shown in FIG.

Furthermore, if the error θ is negative in step SIO,
This means that the rear wheels are being returned to the neutral position, and the shaft torque indicated by the straight line YL is sufficient. Therefore, in this case, the process proceeds to step S13, and the small gain G3 is selected.

By the way, as is clear from Figures 5 (A) and (B), if we assume that the rear wheels are steered to the left from their neutral position, the load center and the steering angle center will coincide. If so, it is sufficient to start steering with the shaft torque of a. However, if the load center and the steering angle center are misaligned, it is effective to change the gain as described above, since a larger shaft torque b than a is required.

Note that in step Sll, the same judgment as described for step SIO is made, and X, l,
A gain suitable for the shaft torque indicated by Y is selected.

(In step S14, the control output value to be supplied to the rudder motor 9A is calculated using the error θ and the gain GL or G selected in step S12 or S13. Then, in step S15, the control output value is calculated. The motor is driven.

In addition, in the embodiment described above, the rear wheel steering angle detection sensor 9
Although an example of a sensor that detects the displacement of the actuating rod 20 has been described as C, this may also be a sensor that detects the amount of rotation of the steering motor 9A.

[Effect 1 of the invention As is clear from the above explanation, according to the present invention, the error between the target steering angle and the actual steering angle is integrated, the load neutral point of the vehicle is determined based on this value, and the error, load neutral Since the output value to the rear wheel steering angle applying means is calculated based on the point, it is possible to calculate the output value to the rear wheel steering angle applying means even if there is an unbalanced load that occurs during vehicle assembly or if the weight of the vehicle is uneven. , it is possible to automatically correct the difference in responsiveness between the left and right sides with respect to the steering center, and it is possible to significantly improve steering stability without giving the driver a sense of discomfort.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram showing an embodiment of the present invention, FIG. 2 is a system configuration diagram showing an embodiment of the present invention, and FIG. Figure 4 is a flowchart showing an example of a control procedure according to an embodiment of the present invention, Figure 5 is a characteristic diagram showing the relationship between motor shaft torque and rear wheel steering angle, and Figure 6 is an explanation of a gain selection table. It is a diagram. 3... Steering angle sensor, 4... Vehicle speed sensor, 9A... Steering motor, 9B... Limiting motor, 9C... Rear wheel steering angle detection sensor, 9D... Cam groove relative Angle detection sensor, lO... Control unit, 20... Operating rod, 22... Fixed block member, 22A... Cam groove, 30... Cylindrical member, 33... Guide rod, 40... - Eccentric cam member, 42... Eccentric cam, 50... Slider member, 50A... Cam groove.

Claims (1)

[Scope of Claims] 1) Rear wheel steering angle applying means for applying a predetermined steering angle to the rear wheels, front wheel steering angle detecting means for detecting the steering angle of the front wheels, and vehicle speed detecting means for detecting the vehicle speed of the vehicle. , a rear wheel steering angle detection means for detecting a steering angle of the rear wheels; and a rear wheel for calculating a target steering angle of the rear wheels according to the amount of steering angle determined by the front wheel steering angle detection means and the vehicle speed determined by the vehicle speed detection means. a steering angle target value calculation means; and an error calculation for calculating the error between the rear wheel target steering angle calculated by the rear wheel steering angle target value calculation means and the rear wheel actual steering angle determined by the rear wheel steering angle detection means. means, error integrating means for integrating the error calculated by the error calculating means, load neutral point calculating means for determining the load neutral point of the vehicle based on the integral value by the error integrating means; A control device for a front and rear wheel steered vehicle, comprising: an output value calculating means for calculating an output value to the rear wheel steering angle applying means based on the above.