JPH058745A - Steering reaction force control device of vehicle - Google Patents

Abstract

(57) [Abstract] [Purpose] Improve vehicle stability by accurately detecting the state of the road surface with a simple structure and controlling the steering reaction force in accordance with the detection result. .. A microcomputer 34 estimates a yaw rate of a vehicle based on wheel speeds of non-driving wheels RW1 and RW2 detected by wheel speed sensors 31 and 32, and
The road surface state is detected according to the deviation between the estimated yaw rate and the yaw rate detected by the yaw rate sensor 33. The microcomputer 34 controls the energization amount of the electromagnetic solenoid 17a according to the detected road surface state, and when the vehicle is running on a rough road surface such as a bumpy road, a puddle road, or a snowdrift road, a reaction force mechanism is provided. The reaction force by the control valve 17 is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering reaction force control device for a vehicle, which controls a reaction force to a steering wheel operation according to a road surface condition.

[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. 3-306970, the state of a traveling road surface is detected based on a steering angle detected by a steering angle sensor, a steering torque detected by a steering torque sensor, and a vehicle speed detected by a vehicle speed sensor. In addition, by controlling the steering reaction force (steering assist force) according to the detection result, it is possible for the driver to be appropriate even while driving on rough roads such as bumpy roads, puddle roads, and snowdrift roads. The steering feel is given to improve the maneuverability of the vehicle.

[0003]

However, in the above-mentioned conventional device, since the steering angle sensor and the steering torque sensor are attached to the steering shaft, the steering mechanism including the steering shaft becomes complicated. Further, the steering torque sensor normally detects the amount of strain generated on the steering shaft, and since the amount of strain is small, it is difficult to detect the steering torque with high accuracy and the steering reaction force with high accuracy. There was a problem of being out of control. The present invention has been made to address the above problems, and an object thereof is to detect a state of a traveling road surface with a simple configuration and with high accuracy, and to control a steering reaction force according to the detection result. Accordingly, it is an object of the present invention to provide a steering reaction force control device for a vehicle, which provides the driver with an appropriate steering feeling to improve the maneuverability of the vehicle.

[0004]

In order to achieve the above object, a structural feature of the present invention is to provide a steering reaction force control device for a vehicle which controls a steering device capable of changing a reaction force with respect to a steering wheel operation. A pair of wheel speed sensors for detecting the respective rotation speeds of the pair of wheels, a yaw rate sensor for detecting the yaw rate of the vehicle, and a difference between the two rotation speeds based on the respective rotation speeds detected by the pair of wheel speed sensors. A yaw rate estimating means for calculating an estimated yaw rate proportional to, an integrating means for integrating a deviation between the detected yaw rate detected by the yaw rate detecting means and the estimated yaw rate calculated by the yaw rate estimating means over a predetermined time, And a reaction force control means for controlling the steering device according to the integrated value integrated by the integration means.

[0005]

In general, if the vehicle is traveling on a good road and the ground contact state of the wheels is good, the left and right wheels have a rotational speed difference that is substantially proportional to the yaw rate of the vehicle. In addition, when the vehicle is traveling on rough roads such as bumpy roads, puddle roads, snowy roads, etc., the ground contact state of the wheels will not be good, and the left and right wheels will have a rotational speed difference that is not proportional to the yaw rate of the vehicle. Occurs. In the present invention configured as described above, since the wheel speed sensor detects each rotation speed of the pair of left and right wheels, the yaw rate estimation is performed if the vehicle is traveling on a good road and the ground contact state of the wheels is good. The estimated yaw rate calculated by the means and the detected yaw rate detected by the yaw rate sensor are substantially equal to each other, and the deviation between the two yaw rates is zero or a small value, so that the integrated value by the integrating means is also small. On the other hand, if the vehicle is traveling on a road surface having a lot of unevenness, a snowdrift road, a puddle road, and the ground contact state of the wheels is not good, there is a difference between the calculated estimated yaw rate and the detected detected yaw rate. Since the deviation is large, the integrated value of the integrating means is also large. As a result, this integrated value indicates that the condition of the road surface on which the vehicle is running is worse as the value increases. Then, the reaction force control means controls the reaction force by the steering device according to the integrated value.

[0006]

As can be understood from the above description of the operation,
According to the present invention, unlike the conventional device described above, the state of the traveling road surface is estimated using the wheel speed sensor and the yaw rate sensor without using the steering angle sensor, the steering torque sensor, and the vehicle speed sensor. The steering reaction force can be controlled with a simple configuration without complicating the steering mechanism and the state of the traveling road surface can be accurately detected. Then, the steering reaction force is appropriately controlled according to the detected state of the traveling road surface, so that the steering stability of the vehicle is always kept good.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows an entire front wheel drive vehicle to which the present invention is applied.

This front-wheel drive vehicle has a steering wheel 11. The steering handle 11 is fixed to the upper end of the steering shaft 12, and the lower end of the coaxial shaft 12 meshes with the rack bar 14 inside the housing 13. The rack bar 14 is the housing 1
3 is supported so as to be displaceable in the axial direction, and left and right front wheels FW1 and FW2, which are drive wheels, are steerably connected at both ends via tie rods 15a and 15b. Inside the housing 13, a power cylinder 16 and a control valve 17 with a reaction force mechanism are provided. Power cylinder 16
Assists the steering of the left and right front wheels FW1 and FW2 according to the rotation of the steering handle 11 in accordance with the supply and discharge of hydraulic oil.

The control valve with reaction mechanism 17 is connected to the hydraulic pump 21 and the reservoir 22, and is a rotary valve for controlling the supply and discharge of hydraulic oil to and from the power cylinder 16 in accordance with the steering torque acting on the steering shaft 12. It is a known device that includes a hydraulic reaction chamber that applies a reaction force proportional to the supplied hydraulic pressure to the operation of the steering wheel 11, and a pressure control valve that controls the hydraulic pressure supplied to the hydraulic reaction chamber. Also,
The control valve 17 with the reaction force mechanism is provided with an electromagnetic solenoid 17a for controlling the pressure control valve, and by decreasing the hydraulic pressure supplied to the hydraulic reaction force chamber as the energization amount to the solenoid 17a increases. , The reaction force to the operation of the steering wheel 11 is reduced (the steering assist force is increased).

The energization amount of the electromagnetic solenoid 17a of the control valve 17 with a reaction force mechanism is controlled by an electric control unit 30 including wheel speed sensors 31, 32, a yaw rate sensor 33 and a microcomputer 34. The wheel speed sensors 31 and 32 output detection signals representing the wheel speeds V _RL and V _RR by measuring the rotational speeds of the left and right rear wheels RW1 and RW2 that are driven wheels, respectively. The yaw rate sensor 33 outputs a detection signal representing the yaw rate γ by measuring the rotational angular velocity (yaw rate) about the vertical axis of the center of gravity of the vehicle body. The yaw rate γ represents a left rotation direction by a positive value and a right rotation direction by a negative value.

The microcomputer 34 is a CPU, RO
It is composed of M, RAM, I / O, etc., and stores a program corresponding to the flowchart of FIG. 2 and also stores current values I ₀ , ΔI in the form of a table. Current value I ₀ , Δ
As shown in FIGS. 3 and 4, I is a function determined according to the vehicle speed V and the road surface state evaluation value D.

Next, the operation of the embodiment configured as described above will be described with reference to the flow chart. When the ignition switch is turned on, the microcomputer 34 starts the execution of the program in step 40 of FIG. 2 and repeatedly executes the circulation process including steps 41 to 48,
The energization of the electromagnetic solenoid 17a of the control valve 17 with the reaction mechanism is controlled.

In this circulation processing, in step 41, the detection signals representing the wheel speeds V _RL and V _RR and the yaw rate γ from the wheel speed sensors 31 and 32 and the yaw rate sensor 33 are input, respectively, and in step 42. The wheel speed V
_The vehicle speed V is calculated by executing the following mathematical _expression 1 using _RL and V _RR .

[Formula 1] V = (V _RL + V _RR ) / 2 In this case, the left and right rear wheels RW
Since 1 and RW2 are the driven wheels and hardly slip, the accurate vehicle speed V is calculated by the calculation of the above-mentioned equation 1.

Next, in step 43, the estimated yaw rate γ * is calculated by executing the calculation of the following equation 2 using the input wheel rotation speeds V _RL and V _RR .

## EQU2 ## γ * = (V _RR -V _RL ) / τ In the equation 2, the value τ represents the tread of the vehicle. If a little explanation is added to the equation 2, the rotation speed of the turning outer wheel is high and the rotation speed of the turning inner wheel is low while the vehicle is turning. In this case, the turning center of the vehicle is located a considerable distance to the side of the vehicle (especially, a large distance when the contact state of the wheels is a problem), and the road surface is good and the wheels contact the ground. If the condition is good, the rotational angular velocity around the vertical axis at the center of gravity of the vehicle body, that is, the yaw rate is small, and is substantially equal to the rotational angular velocity around the vertical axis of the vehicle body at the center positions of the left and right rear wheels RW1, RW2.
Therefore, the rotational angular velocity of the vehicle body about the vertical axis at the center position calculated by the above equation 2, that is, the estimated yaw rate γ *, is better than the yaw rate of the vehicle under the condition that the left and right rear wheels RW1 and RW2 are in a good ground contact state. It is a good approximation.

After calculating this estimated yaw rate, step 4
In step 4, the calculation of the following equation 3 is performed using the calculated estimated yaw rate γ * and the input detected yaw rate γ, whereby a predetermined time T () of the deviation (γ * −γ) between the two yaw rates γ * and γ is obtained. The root-mean-square value over T time ago to the present) is calculated, and the calculated value is set as the road surface state evaluation value D.

[Equation 3] In this case, the vehicle is traveling on a good road and the left and right rear wheels RW1,
If the ground contact state of RW2 is good, the estimated yaw rate γ * is substantially equal to the yaw rate actually occurring in the vehicle, and this actual yaw rate is the detected yaw rate γ detected by the yaw rate sensor 33, as described above. So
The road surface condition evaluation value D becomes a small value. On the other hand, if the vehicle is traveling on a rough road such as a rough road, a snowdrift road, or a puddle road and the ground contact state of the left and right rear wheels RW1 and RW2 is not good, there is a difference between the two yaw rates γ * and γ. Then, the road surface condition evaluation value D becomes a large value.

Next, in step 45, the current value I ₀ is read from the table based on the calculated vehicle speed V (see FIG. 3), and in step 46, the current value ΔI is calculated based on the road surface condition evaluation value D. (See FIG. 4), the energization current value I is calculated by executing the calculation of the following equation 4 using both current values I ₀ and ΔI in step 47.

## EQU4 ## I = I ₀ + ΔI

Then, in step 48, a control signal representing the energizing current value I is output to the electromagnetic solenoid 17a of the control valve 17 with a reaction force mechanism, and a current having a magnitude proportional to the current value I is supplied to the solenoid 17a. Shed. As a result, a steering reaction force inversely proportional to the energizing current value I is generated in the control valve 17 with the reaction force mechanism.

When the driver turns the steering wheel 11 while the control valve 17 with the reaction force mechanism is controlled by the microcomputer 34, the front wheels FW1 and FW2 act on the power cylinder 16 and the control valve 17 with the reaction force mechanism. The steering wheel 11 is steered in response to the rotation of the handle 11 while being assisted by.

At this time, if the vehicle speed V is low, the current value I
_{Since 0} is set to a large value and the energization current value I of the electromagnetic solenoid 17a increases (see FIG. 3), the reaction force to the operation of the steering wheel 11 decreases (the steering assist torque increases), and the steering wheel is operated smoothly. Therefore, the maneuverability of the vehicle in a small turn at low speed is improved.
Conversely, if the vehicle speed V is high, the current value I ₀ is set to a small value and the energization current value I of the electromagnetic solenoid 17a becomes small (see FIG. 3), so the reaction force to the operation of the steering wheel 11 becomes large ( Since the steering assist torque becomes small) and the steering wheel operation becomes heavy, the running stability of the vehicle at high speed running becomes good.

If the condition of the traveling road surface is good and the road surface condition evaluation value D is small, the current value ΔI is set to zero or a negative absolute value (see FIG. 4), and the electromagnetic solenoid 17a is set. The energizing current value I is not changed or is not so small. Further, as the condition of the traveling road surface is not good and the road surface condition evaluation value D increases, the current value ΔI is set to a negative value with a large absolute value (see FIG. 4), and the energization current value of the electromagnetic solenoid 17a is set. Reduce I. As a result, the reaction force applied to the steering wheel 11 by the control valve 17 with the reaction force mechanism increases as the condition of the traveling road surface deteriorates. Therefore, even if the condition of the traveling road surface deteriorates and the steering reaction force from the road surface decreases, the decrease in the steering reaction force is compensated by the control valve 17 with the reaction force mechanism, so that the driver receives it from the steering wheel 11. The steering reaction force is kept substantially constant, the steering feeling is improved, and the steering stability of the vehicle is also improved.

In the above embodiment, an example in which the present invention is applied to a front wheel drive vehicle has been described, but the present invention can also be applied to a rear wheel drive vehicle. In this case, the left and right front wheels FW
1, FW2 are non-driving wheels, so the left and right rear wheels RW1, R
Instead of W2, the wheel speeds of the left and right front wheels FW1 and FW2 may be detected by the wheel speed sensors 31 and 32, and the detected wheel speeds may be used for controlling the steering reaction force.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of a front-wheel drive vehicle according to an embodiment of the present invention.

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

3 is a characteristic graph of a current value I ₀ stored in the microcomputer of FIG. 1 and used for calculation.

4 is a characteristic graph of a current value ΔI stored in the microcomputer of FIG. 1 and used for calculation.

[Explanation of symbols]

FW1, FW2 ... front wheels, RW1, RW2 ... rear wheels, 11 ...
Steering wheel, 16 ... Power cylinder, 17 ... Control valve with reaction force mechanism, 17a ... Electromagnetic solenoid, 31, 32
... wheel speed sensor, 33 ... yaw rate sensor, 34 ... microcomputer.

Claims (1)

Claim: What is claimed is: 1. A steering reaction force control device for a vehicle, which controls a steering device capable of changing a reaction force to a steering wheel operation, comprising:
A pair of wheel speed sensors for detecting the respective rotation speeds of the pair of left and right wheels, a yaw rate sensor for detecting the yaw rate of the vehicle, and a pair of wheel speed sensors based on the respective rotation speeds detected by the pair of wheel speed sensors. A yaw rate estimating means for calculating an estimated yaw rate proportional to the difference; an integrating means for integrating a deviation between the detected yaw rate detected by the yaw rate detecting means and the estimated yaw rate calculated by the yaw rate estimating means over a predetermined time period;
A steering reaction force control device for a vehicle, comprising: a reaction force control device that controls the steering device according to an integrated value integrated by the integration device.