JP3539085B2 - Vehicle steering control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering controller of a vehicle, by which straight traveling performance of the vehicle and return of a steering wheel are improved by controlling the wheel speeds of right and left wheels according to the steering state. SOLUTION: A vehicle provided with a wheel speed control means capable of controlling the wheel speeds of right and left wheels is constituted of a judging means for judging the neutral state and the returning state of steering on the basis of a detected signal of a steering detecting means and a steering angle detecting means, and a controller 10 for controlling a wheel speed control means so that the wheel speeds of the right and left wheels may be maintained to be the constant speed in the neutral state and so that the wheel speeds of the right and left wheels may be approached to the constant speed in the returning state according to the steering state judged by the judging means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering control device which can improve the straightness of a vehicle or return of a steering wheel by controlling the wheel speed of left and right wheels according to a steering state.

[0002]

2. Description of the Related Art Generally, in power steering,
Although assisting manual torque based on steering, it does not have any active effect on maintaining steering neutrality, and the straightness of the vehicle is maintained by restoring caused by suspension geometry settings such as camber and toe-in At present it depends on power.

[0003] For this reason, in a vehicle equipped with a power steering, there have been complaints that the steering wheel is not smooth and the steering wheel return is poor, and that the steering wheel returns poorly.

[0004]

As an improvement to respond to the above-mentioned points and dissatisfactions, a suspension in which the friction of each part of the steering wheel is reduced so that the restoring force acts more effectively or the restoring force is generated more greatly. There are methods such as setting the geometry.However, in both cases, the robustness against disturbance input generated between the tire and the road surface is reduced, and kickback disturbance is likely to be transmitted as steering wheel vibration. Excitation vibration tends to lead to deterioration of steering characteristics such as easy occurrence of steering wheel vibration.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a steering control apparatus for a vehicle which can improve the straightness of the vehicle and the return of the steering wheel by controlling the wheel speed of the left and right wheels according to the steering state. .

[0006]

According to a first aspect of the present invention, there is provided a vehicle provided with wheel speed control means capable of controlling wheel speeds of left and right wheels, a wheel speed detection means for detecting the wheel speeds of the left and right wheels, respectively. A steering gear for steering the front wheels based on the steering operation; a steering detection means for detecting the steering operation; a steering angle detection means for detecting the steering angle of the front wheels; and a detection signal of the steering detection means and the steering angle detection means. A control unit that controls the wheel speed control unit to maintain the wheel speeds of the left and right wheels at a constant speed if the determination unit determines a neutral state based on the steering condition; It is constituted by.

According to a second aspect of the present invention, there is provided a vehicle provided with a wheel speed control means capable of controlling the wheel speeds of the left and right wheels, a wheel speed detection means for detecting the wheel speeds of the left and right wheels, respectively, and a front wheel based on a steering operation. A steering gear for steering the steering wheel, a steering detecting means for detecting the steering operation, a steering angle detecting means for detecting a steering angle of the front wheels, and a steering return state based on detection signals of the steering detecting means and the steering angle detecting means. And a control device that controls the wheel speed control means so as to reduce the wheel speed difference between the left and right wheels when the return state is determined by the determination means.

According to a third aspect of the present invention, there is provided a vehicle having a wheel speed control means capable of controlling the wheel speeds of the left and right wheels, a wheel speed detection means for detecting the wheel speeds of the left and right wheels, respectively, and a front wheel based on a steering operation. A steering gear for steering the steering wheel, a steering detecting means for detecting the steering operation, a steering angle detecting means for detecting a steering angle of the front wheel, and a neutral state of steering based on detection signals of the steering detecting means and the steering angle detecting means. Discriminating means for discriminating between the wheel speeds of the left and right wheels in a neutral state according to the steering state discriminated by the discriminating means. And a control device for controlling the wheel speed control means so as to reduce the vehicle speed.

According to a fourth aspect of the present invention, there is provided a vehicle provided with a wheel speed control means capable of controlling the wheel speeds of the left and right wheels, a wheel speed detection means for respectively detecting the wheel speeds of the left and right wheels, and a front wheel based on a steering operation. A steering gear for steering the steering wheel, a steering detecting means for detecting the steering operation, a steering angle detecting means for detecting a steering angle of the front wheels, and a neutral state of steering based on detection signals of the steering detecting means and the steering angle detecting means. Discriminating means for discriminating a turning state and a returning state; and maintaining the wheel speeds of the right and left wheels at a constant speed in a neutral state according to the steering state discriminated by the discriminating means; A control device for giving a difference to the wheel speeds and controlling the wheel speed control means so as to reduce the wheel speed difference between the left and right wheels in the return state. Those constituted by the.

The invention according to claims 5 and 6 is characterized in that the wheel speed control means comprises an anti-lock brake system capable of independently controlling the braking force of the left and right wheels, or a differential of the driving force distributed to the left and right wheels. In the differential limiting device that limits

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 10 denotes a wheel speed control unit capable of independently controlling the wheel speeds of all four wheels. The control unit 10 detects the wheel speeds of the left and right front wheels 11FL and 11FR and the left and right rear wheels 11RL and 11RR. Wheel speed sensors 12A, 12B, 12C, 12D and front wheels 11F
A torque sensor 14 for detecting a steering torque applied to a steering wheel 13 for steering the L and 11FR, and a steering angle sensor 1 for detecting a steering angle of the front wheels 11FL and 11FR.
5 are respectively connected.

The torque sensor 14 outputs a signal corresponding to the steering torque applied to the steering wheel 13, and this signal has positive and negative values depending on the steering direction. Further, the steering angle sensor 15 outputs a signal corresponding to the turning angle of the front wheels 11FL and 11FR, and this signal becomes positive and negative values by turning right and left. The steering wheel 13
Are the left and right front wheels 11FL, 1 via the steering gear 17.
1FR, the left and right front wheels 11FL and 11FR can be steered by operating the steering wheel 13. Here, the steering gear 17 is formed of a manual steering device having no power assist function, and the steering assist action is performed by the front wheels 11FL, 11
This is achieved by FR wheel speed difference control.

As shown in FIG. 2, the control unit 10 includes an input interface 21, a central processing unit (hereinafter referred to as CPU) 22, a read-only memory (hereinafter referred to as ROM) 23, and a random access memory (hereinafter referred to as RAM). ) 24 and an output interface 25. Various signals are input from the input interface 21, the processing is executed by the CPU 22, and a control signal is output from the output interface 25.

In the ROM 23, as shown in FIG.
A cutting control map A in which the relationship between the steering torque Tm and the differential ratio Δnf representing the ratio of the wheel speed of the left and right front wheels 11FL and 11FR is programmed in advance, and a wheel speed correction coefficient C for the steering angle θ as shown in FIG. Is stored in advance in the return control map B. From the incision control map A, a differential ratio Δnf with respect to the steering torque Tm detected by the torque sensor 14 is read, and one of the wheels of one of the front wheels to be turned inside wheels based on the differential ratio Δnf as described later. The target speed N1 is calculated by the following equation (1). Here, n2 indicates the current wheel speed of the other front wheel serving as the turning outer wheel.

N1 = (1−Δnf) · n2 (1) A correction coefficient C for the steering angle θ is read from the return control map B, and one of the turning outer wheels is determined based on the correction coefficient C as described later. Is calculated from the following equation (2). Here, n1 indicates the current wheel speed of the other front wheel on the turning inner wheel side.

N2 = n1 · C (2) Next, wheel speed control for controlling the wheel speeds of all four wheels at a constant speed, or controlling the wheel speeds of the inner or outer turning wheels to target values N1 and N2. Will be described. Here, the wheel speed control can be performed by an antilock brake system (hereinafter referred to as ABS) that can independently control the braking force of the four wheels, or a differential limiting device that limits the differential between the left and right front wheels or the left and right rear wheels. In the following description, an example in which the wheel speed is controlled using the ABS will be described.

FIG. 5 shows a braking pressure control device 3 using ABS.
0 is schematically shown taking the left front wheel 11FL as an example. The braking pressure control device 30 controls each wheel 11FL, 11FR,
Normal braking control for controlling the vehicle by independently controlling the braking forces of 11RL and 11RR, and steering control for controlling the steering of the vehicle by actively controlling the wheel speeds of the left and right wheels according to the steering state. It has two functions.

Here, the normal braking control is a known one and is not a feature of the present invention. Therefore, the following description will focus on steering control by wheel speed control. In FIG. 5, reference numeral 33 denotes a master cylinder operated in response to the operation of the brake pedal 31. One output port of the master cylinder 33 and the wheel cylinder 3
4, a normally open and normally closed solenoid valve 35,
36 and a pump 38 driven by an electric motor 37
Is interposed. The discharge side of the normally closed solenoid valve 36 is connected to a reservoir 39.

The solenoid valves 35 and 36 are two-port two-position solenoid switching valves, and when the solenoid is not excited, the wheel cylinder 34 is connected to the master cylinder 33 and the pump 3.
The wheel cylinder 34 is connected to the reservoir 39 when the solenoid is excited. By controlling the energization of the solenoids of the solenoid valves 35 and 36, the braking pressure in the wheel cylinder 34 can be increased, reduced or maintained. That is, the solenoid valve 3
When the solenoids 5 and 36 are not excited, the brake fluid pressure is supplied to the wheel cylinder 34 from the master cylinder 33 and the pump 38 to increase the pressure. When the solenoids of the solenoid valves 35 and 36 are excited, the wheel cylinder 34
9 and the pressure is reduced. Also, if the solenoid of the solenoid valve 35 is excited and the solenoid of the solenoid valve 36 is de-energized, the braking pressure in the wheel cylinder 34 can be maintained.

The solenoids of the solenoid valves 35 and 36 are connected to the control unit 10 via a solenoid drive circuit 41.
Similarly, the above-described electric motor 37 is connected to the output interface 25 via a motor drive circuit 42. Next, control unit 1
A control procedure for controlling the steering of the vehicle using 0 will be described based on the flowchart of FIG.

All four wheels 11FL, 11F changing every moment
The wheel speeds n1 to n4 of R, 11RL, and 11RR, the steering torque Tm applied to the steering wheel 13, and the steering angles θ of the left and right front wheels 11FL and 11FR are determined by wheel speed sensors 12A to 12D, a torque sensor 14, and a steering angle sensor 15. Respectively, and these wheel speed signals n1
To n4, the steering torque signal Tm, and the steering angle signal θ are input from the input interface 21 of the control unit 10 and stored in a predetermined storage area of the RAM 24.

On the other hand, the CPU 22 executes the processing operation shown in FIG. 6 when an interrupt signal is input at regular intervals. First, in step 100 of the figure, the wheel speed signals n1 to n4, the steering torque signal Tm, and the steering angle signal θ stored in a predetermined storage area of the RAM 24 are read. In step 102, the differential ratio Δnf corresponding to the absolute value | Tm | of the steering torque signal Tm and the correction coefficient C corresponding to the absolute value | θ | of the steering angle signal θ are respectively stored in the ROM 23. It is read from the control map A (FIG. 3) and the return control map B (FIG. 4).

Next, at step 104, it is determined whether the absolute value | Tm | of the steering torque signal Tm is larger or smaller than a predetermined value Tm0. If it is larger than the predetermined value Tm0, it is determined that the steering wheel 13 is in the steering state (cutting state), and the routine proceeds to step 106. In this step 106, the target wheel speed N1 of the turning inner wheel is calculated by substituting the differential ratio Δnf into the equation [N1 = (1−Δnf) · n2].
Move to 8.

In step 108, it is determined whether or not the current wheel speed n1 of the turning inner wheel has become equal to the target wheel speed N1, and if so, the program is returned. Step 1
At 10, the braking force of the turning inner wheel is controlled in a direction in which the wheel speed of the turning inner wheel matches the target value N1. In this way, the cutting control process for assisting the steering torque by giving the wheel speed difference to the left and right front wheels 11FL and 11FR is executed.

On the other hand, if it is determined in step 104 that the absolute value | Tm | of the steering torque signal Tm is smaller than the predetermined value Tm0, then in step 112, the absolute value | θ | It is determined whether the value is larger or smaller than the predetermined value θ0. If it is smaller than the predetermined value θ0, it is determined that the front wheels 11FL and 11FR are near neutral, and the process proceeds to step 114. In this step 114, all four wheels 11FL, 11FR, 11
It is determined whether or not the current wheel speeds n1 to n4 of the RL and 11RR are equal, and if they are equal, the program is returned, but if they are not equal, at step 116, all four wheels 11FL, 11FR, 11RL, 11RR A neutral control process is performed to make the wheel speeds of the wheels equal.

On the other hand, if it is determined in step 112 that the absolute value | Tm | of the steering torque signal Tm is larger than the predetermined value θ0, it is determined that the steering wheel 13 is in the returning state, and the process proceeds to step 118. Transition. Then, in step 118, the correction coefficient C is substituted into the equation [N2 = n1 · C] to calculate the target wheel speed N2 of the turning outer wheel, and the routine proceeds to step 120.

In step 120, it is determined whether or not the current wheel speed n2 of the turning outer wheel has become equal to the target wheel speed N2, and if so, the program is returned. Step 1
At 22, the braking force of the turning outer wheel is controlled in a direction in which the wheel speed of the turning outer wheel matches the target value N2. In this way, a return control process for reducing the difference in wheel speed between the left and right front wheels 11FL and 11FR and improving the return of the steering wheel is executed.

Although detailed description is omitted, in actual cut control processing or return control processing,
The turning direction or returning direction of the steering wheel 13 is determined from the sign of the steering torque signal Tm and the sign of the steering angle signal θ, and one of the left and right front wheels 11FL and 11FR is controlled to the target wheel speeds N1 and N2 based on the cutting direction. The turning inner wheel or the turning outer wheel to be selected.

The above-described neutral control processing, cutting control processing and return control processing are performed by energizing the solenoid valves 35 and 36 of the braking pressure control device 30 for controlling the braking pressure of the left and right front wheels 11FL and 11FR and the left and right rear wheels 11RL and 11RR. And the drive control of the electric motor 37, the left and right front wheels 11FL, 1FL,
This is achieved by increasing or decreasing the braking pressure of 1FR and the left and right rear wheels 11RL, 11RR.

That is, all four wheels 11FL, 11FR, 1
In the case of the 1RL and 11RR wheel speed constant speed control, the braking force of the other wheels is controlled to match the wheel speed based on the lowest wheel speed among the wheel speeds n1 to n4 of all four wheels. , The wheel speeds n1 to n4 of all four wheels are made equal. By such constant velocity control of all four wheels, the neutral holding of the steering is actively controlled, and the neutral straightness can be significantly improved.

When the vehicle is in the notched state, the wheel speed n1 of the left (right) front wheel 11FL (11FR), which is to be the turning inner wheel, matches the target wheel speed N1, that is, the right (left) wheel, which is the turning outer wheel. ) The left (right) front wheel 11F is set to a value lower than the wheel speed n2 of the front wheel 11FR (11FL).
The braking force of L (11FR) is controlled. For example, when the current wheel speed n1 is higher than the target wheel speed N1, the braking force of the turning inner wheel is increased. Conversely, when the current wheel speed n1 is lower than the target wheel speed N1, turning is performed. Decrease inner wheel braking force.

As described above, the left and right front wheels 11FL, 11FR
7 by actively giving the wheel speed difference to
As shown in FIG. 5, a yaw moment M is generated around the center of gravity of the vehicle due to the tire reaction force with the road surface, and assist power is generated to compensate for the deflection force of the left and right front wheels 11FL and 11FR due to the manual torque applied to the steering wheel 13. Will be.

Further, in the return state, the wheel speed n2 of the left (right) front wheel 11FL (11FR) of the turning outer wheel matches the target wheel speed N2, that is, the right (left) front wheel serving as the turning inner wheel. The left (right) front wheel 11FL (11F) is set to a value lower than the wheel speed n1 of 11FR (11FL).
R) The braking force is controlled. For example, when the current wheel speed n2 is higher than the target wheel speed N2, the braking force of the left (right) front wheel 11FL (11FR) is increased, and conversely, the current wheel speed n2 is higher than the target wheel speed N2. If smaller, the braking force of the left (right) front wheel 11FL (11FR) is reduced.

By the control in such a direction as to reduce the difference in wheel speed between the left and right front wheels 11FL and 11FR, a restoring force is exerted on the left and right front wheels 11FL and 11FR returning to the neutral position to more positively return to neutral. The so-called steering wheel return can be improved. The returnability of the steering wheel in this case is determined by how the correction coefficient C is determined for the steering angle θ, and the characteristics can be arbitrarily set from a sharp steering wheel return to a gentle steering wheel return.

In the above-described wheel speed control, the wheel speed to be controlled is not controlled so as to completely match the target value.
The braking force is controlled so as to be within this width, and the control is stabilized. FIG. 8 shows another embodiment of the present invention. In the vicinity of neutral steering, that is, when the steering torque is equal to or less than Tm0, all four wheels 11FL, 11F are provided.
R, 11RL, and 11RR are not simply controlled at a constant speed, but can be controlled with a certain width based on a neutral coefficient K shown in FIG.

That is, in a region where the steering torque signal Tm of the torque sensor 14 is smaller than the predetermined value Tm0, a neutral control map C defining a neutral coefficient K for the steering torque signal Tm is stored in the ROM 23, When the steering torque signal Tm is smaller than the predetermined value Tm0, a neutral coefficient K corresponding to the steering torque signal Tm is read from the neutral control map C, and all four wheels 11FL, 11FR, 11RL, 11RR are determined according to the neutral coefficient K. Is controlled at substantially constant speed to increase the neutral straightness by constant speed control in a true neutral state, and to provide a certain width in the vicinity of the steering speed signal Tm in accordance with the steering torque signal Tm, thereby providing a clear sense of neutrality. , But is controlled to follow the steering torque Tm applied to the steering wheel 13.

In the above embodiment, the left and right front wheels 11FL, 11FRB and the left and right rear wheels 11RL, 11R
The example in which ABS is used as a means for controlling the wheel speed of R has been described. However, the wheel speed control means is not limited to ABS. For example, other means such as using a differential limiting function of a differential mechanism may be used. The wheel speed control means having the above configuration can be used.

In the above-described embodiment, an example has been described in which the neutral control is performed by controlling the wheel speeds of all four wheels. However, the neutral control may be performed by controlling the wheel speeds of the front two wheels. The control and the return control can also be performed by controlling the wheel speeds of all four wheels. Further, in the above-described embodiment, an example in which the operation of the steering wheel 13 is detected based on the signal of the torque sensor 14 has been described. However, other steering detecting means capable of detecting the steering direction and the magnitude thereof may be used. Good.

In the above-described embodiment, a characteristic map in which the relationship between the steering torque Tm and the front wheel differential ratio Δnf representing the ratio of the differential between the wheel speeds of the left and right front wheels 11FL and 11FR is stored in advance. Although the target wheel speed of the front inner wheel is calculated based on the differential ratio read from the characteristic map, the target wheel speed of the front inner wheel is determined by calculating the steering torque Tm and the current wheel speed of the front wheel. It can also be obtained directly from the calculation formula as a variable.

[0040]

As described above, according to the present invention, the neutral state and / or the return state of the steering is determined, and the wheel speeds of the left and right wheels are made uniform at the neutral state according to the determined steering state. In the return state, the left and right wheels are controlled so that the wheel speeds approach the constant speed, so that the neutral straightness can be improved and the steering wheel return can be improved.

According to the present invention, the steering assist is provided by providing a wheel speed difference between the left and right wheels in addition to the above-described improvement of the neutral straightness and the return of the steering wheel, and a power source is provided on the steering gear side. It is possible to achieve a large energy saving with an extremely simple configuration.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a wheel speed control unit.

FIG. 3 is a diagram showing a control map showing a relationship between a steering wheel torque and a front wheel differential ratio.

FIG. 4 is a diagram showing a control map representing a correction coefficient for a steering angle.

FIG. 5 is a diagram showing a configuration of a braking force control device.

FIG. 6 is a flowchart showing a braking force control process.

FIG. 7 is a diagram for explaining a turning motion of the vehicle.

FIG. 8 is a diagram showing a control map representing a neutral coefficient with respect to a steering torque.

[Explanation of symbols]

10 Wheel speed control unit 11FL, 11FR front wheel 11RL, 11RR Rear wheel 12A ~ 12D Wheel speed sensor 13 Steering wheel 14 Torque sensor 15 Steering angle sensor 17 Steering gear 30 Braking pressure control device 31 Brake pedal 33 Master cylinder 34 wheel cylinder

Claims (6)

(57) [Claims] 1. A vehicle provided with wheel speed control means capable of controlling wheel speeds of left and right wheels, a wheel speed detection means for detecting wheel speeds of the left and right wheels, respectively, and a steering gear for steering front wheels based on a steering operation. Steering detecting means for detecting the steering operation, steering angle detecting means for detecting a steering angle of the front wheels, and determining means for determining a neutral state of steering based on detection signals of the steering detecting means and the steering angle detecting means. And a control device for controlling the wheel speed control means so as to maintain the wheel speeds of the left and right wheels at a constant speed when the neutral state is determined by the determination means. Control device. 2. A vehicle provided with wheel speed control means capable of controlling wheel speeds of left and right wheels, a wheel speed detection means for detecting wheel speeds of the left and right wheels, respectively, and a steering gear for steering front wheels based on a steering operation. Steering detecting means for detecting the steering operation, steering angle detecting means for detecting the steering angle of the front wheels, and determining means for determining a return state of the steering based on detection signals of the steering detecting means and the steering angle detecting means. And a control device for controlling the wheel speed control means so as to reduce the wheel speed difference between the left and right wheels when the return state is determined by the determination means. . 3. A vehicle provided with wheel speed control means capable of controlling the wheel speeds of left and right wheels, a wheel speed detection means for detecting the wheel speeds of the left and right wheels, respectively, and a steering gear for steering a front wheel based on a steering operation. A steering detecting means for detecting the steering operation, a steering angle detecting means for detecting a steering angle of the front wheels, and a neutral state and a returning state of steering based on detection signals of the steering detecting means and the steering angle detecting means. Determining means for maintaining the wheel speeds of the left and right wheels at a constant speed in a neutral state and reducing the wheel speed difference between the left and right wheels in a return state according to the steering state determined by the determining means. A vehicle steering control device comprising: a control device that controls the wheel speed control means. 4. A vehicle provided with wheel speed control means capable of controlling wheel speeds of left and right wheels, a wheel speed detection means for detecting wheel speeds of the left and right wheels, respectively, and a steering gear for steering front wheels based on a steering operation. A steering detecting means for detecting the steering operation, a steering angle detecting means for detecting a steering angle of the front wheels, a neutral steering state, a turning state and a return state based on the detection signals of the steering detecting means and the steering angle detecting means. Determining means for determining the state; and maintaining the wheel speeds of the left and right wheels at a constant speed in the neutral state according to the steering state determined by the determining means, and determining a difference between the wheel speeds of the left and right wheels in the notch state. And a control device that controls the wheel speed control means so as to reduce the wheel speed difference between the left and right wheels in the return state. A steering control device for a vehicle. 5. The vehicle steering control device according to claim 1, wherein said wheel speed control means comprises an anti-lock brake system capable of independently controlling braking forces of left and right wheels. 6. The vehicle steering control device according to claim 1, wherein the wheel speed control means comprises a differential limiting device that limits a differential of a driving force distributed to left and right wheels.