JP3147635B2 - Steering reaction force control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving simulator for simulating the running condition of an automobile in a laboratory, and to a steering system in which a driver does not directly connect a steering wheel to a steering wheel when the driver operates the steering wheel. The present invention relates to a control device for a device for applying a reaction force.

[0002]

2. Description of the Related Art In a driving simulator, a device for applying a steering reaction force received when a driver steers a steering wheel is disclosed in Japanese Patent Application No. Hei 4-8269.
There is No. 8. This prior art calculates a steering reaction force given to a driver based on a steering angle, a vehicle speed, and a slip angle to improve a steering feeling. There is a case where the steering reaction force at the time of starting cannot be simulated.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a device for applying a steering reaction force which a driver receives when steering a steering wheel. It is to simulate the steering reaction force at a low speed as described above.

[0004]

A steering reaction force control device according to the present invention comprises: a steering angle detecting means for detecting a steering angle of a steering wheel; a vehicle speed detecting / calculating means for detecting or calculating a vehicle speed of a vehicle; Determining means for determining whether or not the vehicle is stopped, a slip angle calculating means for calculating a slip angle of a steered wheel based on the vehicle speed and the steering angle, the steering angle, the vehicle speed and the slip angle. And a steering reaction torque calculating means for calculating the steering reaction torque on the basis of the above, and increasing the steering reaction torque as the vehicle speed increases in a low vehicle speed state; and a friction force for decreasing the friction force as the vehicle speed increases. A steering reaction torque correction means for weighting the steering reaction torque based on the slip angle to calculate a corrected steering reaction torque; When the vehicle is in a stopped state, a steering reaction force applied to a steering wheel is controlled based on the frictional force. When the vehicle is in a running state, steering is controlled based on the corrected steering reaction force torque and the frictional force. A steering reaction force control device for controlling a steering reaction force applied to a wheel.

[0005]

The present invention has the following functions.
In the present invention, first, it is determined whether or not the vehicle has stopped based on the vehicle speed of the vehicle. When the vehicle is stopped (during stationary operation), a substantially constant steering reaction force is applied to the steering wheel by the frictional force applying means regardless of the steering angle and the steering angular velocity. Hereinafter, the validity of applying such a steering reaction force will be described. When the vehicle is stationary, the frictional force acting on the contact surface between the tire and the road surface is large.Therefore, in vehicles equipped with power steering, the auxiliary force of the steering force should be maximized to reduce the steering force when the vehicle is stopped. I do. Therefore, the hydraulic oil is pressurized by the power steering pump to a state close to the maximum set pressure. Further, the frictional force is substantially constant regardless of the steering angle.

Therefore, in a state close to such a maximum set pressure, the torsion angle of the torsion bar connected to the steering wheel of the vehicle changes in a narrow region near the maximum value regardless of the steering angle. This means that the steering reaction force at the time of stationary steering is substantially constant.

Further, when the steering wheel is turned and the steering wheel is released and the hand is released, the steering reaction force disappears accordingly, and the steering wheel stops at the released steering angle. Further, it is preferable that the steering reaction force in this case is set to be larger than when the speed is high.

When the vehicle is not stopped, that is, when the vehicle is running, first, the slip angle of the steered wheels is calculated based on the steering angle of the steering wheel and the vehicle speed. Next, a steering reaction force is calculated based on the steering angle, the vehicle speed, and the slip angle. Further, the steering reaction force is weighted based on the slip angle to calculate a corrected steering reaction force.

In this case, the characteristic feature is that, in a low speed state such as when starting from a stopped state of the vehicle, the steering reaction torque increases as the vehicle speed increases, and the frictional force decreases as the vehicle speed increases. It is. This increases the self-aligning torque from the state in which the braking torque generated by the frictional force applying means is larger than the driving torque of the steering reaction force applying means in the vehicle stopped state, and increases the steering reaction force torque by increasing the vehicle speed. The steering reaction force is continuously connected to a state in which is larger than the brake torque.

[0010]

As described above, during stationary operation,
By applying a substantially constant steering reaction force to the steering wheel irrespective of the steering angle and the steering angular velocity by the frictional force applying means, it is possible to simulate the steering reaction force of the actual vehicle. Also, in a low-speed state such as when starting from a vehicle stop state, the steering reaction torque is increased as the vehicle speed increases, and the frictional force is decreased as the vehicle speed increases, so that steering in the vehicle stop state is performed. A state in which the braking torque generated by the frictional force applying means is larger than the driving torque of the reaction force torque applying means, and a state in which the steering reaction force torque is larger than the brake torque due to an increase in the self-aligning torque due to an increase in vehicle speed. The steering reaction force is continuously connected to. Therefore, the present invention can satisfactorily simulate the steering reaction force when the vehicle is stopped and the steering reaction force at a low speed such as when starting from a stopped state.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a driving simulator will be described below. FIG. 1 shows the configuration of this embodiment.

The driving simulator of this embodiment is
When the driver operates the steering wheel 1, the accelerator 6, and the brake 7, the motion of the vehicle is calculated in the personal computer 11 based on the operation amounts of these. In this embodiment, a steering reaction force due to a self-aligning torque and a caster effect for the front wheels is obtained, and the steering reaction force is weighted by a function of a front wheel slip angle βf, and a simulated steering reaction force equipped with a power steering mechanism of a real vehicle is obtained. Is given to the driver. Actuator 2 for giving this steering reaction force
Is an electric motor, and the torque of this motor is controlled by a motor drive circuit 8 in response to a reaction force command from a personal computer.

On the other hand, a flat belt wheel 3 provided between the steering wheel 1 and the actuator 2, and a powder brake 4 connected to the flat belt wheel 3 by the flat belt 5.
Constitutes a friction imparting mechanism of the steering reaction force simulator. The braking force of the powder brake 4 includes vehicle speed, steering angle,
A current controlled by the brake drive circuit 9 is calculated by the personal computer 11 according to the steering speed, and the calculated value is applied to the powder brake 4.

The rotation angle of the steering wheel 1, that is, the steering angle, is detected by a pulse generator 10 provided in the electric motor 2. This steering angle is converted into a digital value by an I / O interface attached to the personal computer 11.

The accelerator opening is determined by the accelerator pedal 6
Is detected in an analog manner by a potentiometer, and this signal is converted into a digital value by an analog / digital converter attached to the personal computer 11.

The brake signal is obtained by detecting the stroke of the brake pedal 7 in an analog manner using a potentiometer, as in the case of the accelerator opening, and converting the signal into a digital value by an analog / digital converter of the personal computer 11.

Next, the arithmetic processing performed in the personal computer 11 will be described with reference to FIG. First,
In step 30, a vehicle model for calculating the driving state of the vehicle from the digitized signals of the driving operation of the driver, that is, accelerator, brake, and steering will be briefly described. The longitudinal acceleration u 'of the vehicle is approximately determined by the following equation: u' = A * VA-B * VB-C * u2-D * u (1) Here, VA: accelerator opening,
VB: Brake stroke, A, B, C, D are appropriately set constants.

First, the steering reaction force when u = 0, that is, when the vehicle is stopped (during stationary operation), will be described. When the vehicle is stopped (when the vehicle is stationary), the powder brake 4 applies a substantially constant steering reaction force to the steering wheel regardless of the steering angle and the steering angular velocity. The validity of applying a substantially constant steering reaction force will be described below. When the vehicle is stationary, the frictional force acting on the contact surface between the tire and the road surface is large.Therefore, in vehicles equipped with power steering, the auxiliary force of the steering force should be maximized to reduce the steering force when the vehicle is stopped. I do. Therefore, the hydraulic oil is pressurized by the power steering pump to a state close to the maximum set pressure. Further, the frictional force is substantially constant regardless of the steering angle.

Therefore, in a state close to the maximum set pressure, as shown in FIG. 10, the torsion angle of the torsion bar connected to the steering wheel of the vehicle changes in a narrow region near the maximum value regardless of the steering angle. Will do. This means that the steering reaction force at the time of stationary steering is substantially constant. Further, if the steering of the steering wheel is stopped and the hand is released at the time of stationary steering, the steering reaction force disappears accordingly, and the steering wheel stops at the steering angle at which the hand is released. As described above, at the time of stationary steering, by applying a substantially constant steering reaction force to the steering wheel irrespective of the steering angle and the steering angular velocity by the powder brake 4, the steering reaction force of the actual vehicle can be simulated. Further, it is preferable that the steering reaction force in this case is set to be larger than when the speed is high.

Next, the case where u> 0, that is, the vehicle is in a running state will be described.

If the vehicle is running, step 3
In step (1), the lateral and yaw movements of the vehicle are determined by the following equations based on the vehicle speed and the steering angle determined by equation (1).

[0022]

(Equation 1)

Here, m: weight of the vehicle β: slip angle of the vehicle r: yaw rate of the vehicle kf: cornering power of the front wheel kr: cornering power of the rear wheel if: distance from the front wheel to the center of gravity of the vehicle lr: vehicle from the rear wheel Distance to center of gravity θh: Steering angle G: Steering system gear ratio (steering wheel angle / front wheel actual steering angle) I: Yaw moment of inertia of vehicle

Further, in step 32, (1),
The slip angle βf of the front wheels is obtained from the following equation from the vehicle slip angle β, the yaw rate r, and the detected steering angle θh, which are obtained by solving the simultaneous differential equations (2) and (3). βf = β + (lf / u) r-θh / G (4)

In step 33, the self-aligning torque M of the front wheels can be approximated by the following equation in a range where the front wheelslip angle is small. M = {kf βf (5) where ξ is a pneumatic trail.

Accordingly, the running condition of the vehicle is obtained from the signals of the accelerator, the brake and the steering by the equations (1) to (3), and the self-aligning torque for the front wheels is then calculated by the equations (4) and (5). Desired.

In steps 35, 36 and 37, the torque MC associated with the running resistance due to the caster effect is θ
When h is | θh | ≦ GC * G (6), MC = kC (θh / G) (7), and when | θh |> GC * G (8), MC = GC * kC (9) Desired. FIG. 2 shows the expressions (6) to (9) collectively.

Finally, in step 39, the self-aligning torque M obtained by the equation (5) and the torque MC by the caster effect obtained by the equation (7) or (9) are added. This added torque is the steering reaction force of a manually-steered vehicle without a power steering mechanism.

By the way, as described above, in the power steering system, the assisting force acts according to the steering torque of the driver, that is, the steering reaction force which is in the relation of the action and the reaction, and the sum of the steering force of the driver and the assist force is calculated. , And the force of the front wheels to return to the straight running state. Therefore, the sum of the self-aligning torque determined by the equation (5) and the torque due to the caster effect determined by the equation (7) or (9), that is, a part of the combined torque is given to the driver as a steering reaction force in the driving simulator. This makes it possible to simulate a power steering mechanism.

This combined torque is calculated as a function f of the front wheel slip angle.
By weighting with (βf), the power steering mechanism can be effectively simulated. This function f (βf)
Is, for example, as shown in FIG. That is, in the range where the front wheel slip angle βf is small, f (βf) is almost 1
And f (βf) is a function that decreases as βf increases. The steering reaction force command obtained in this way is as follows. Th * = f (βf) * (M + MC) (10)

When simulating the steering reaction force of the vehicle speed-sensitive power steering, the steering reaction force command Th * expressed by the equation (10) should be weighted using the vehicle speed function g (u). I understand. This function g (u) is as shown in FIG.

In this case, the characteristic feature is that the function g is obtained in a low speed state such as when starting from a vehicle stopped state.
By increasing the value of (u) as the vehicle speed increases, and decreasing the braking force command TBU, which will be described later, as the vehicle speed increases, the value of the powder brake 4 compared to the drive torque of the electric motor 2 in the vehicle stopped state. The steering reaction force is continuously connected from a state where the generated brake torque is large to a state where the steering reaction torque becomes larger than the brake torque due to an increase in the self-aligning torque due to an increase in the vehicle speed.

The reaction force command Th given to the motor drive circuit 8 for driving the electric motor 2 which is an actuator for applying a steering reaction force in FIG. Th = g (u) * f (βf) (M + MC) (11)

The steering reaction force Th obtained by the equation (11) is
The value is the same when the driver cuts the steering wheel and when the driver returns. However, in the case of an actual vehicle, turning the steering wheel is heavier than returning the steering wheel. That is, the relationship between the steering angle and the steering reaction force has a hysteresis as shown in FIG.

The hysteresis characteristic as shown in FIG. 6 can be produced by a friction mechanism provided between the actuator 2 and the steering wheel 1, that is, the powder brake 4, as shown in FIG. If this powder braking force is always constant, the width B of the hysteresis shown in FIG.
Becomes constant regardless of the steering angle. However, in an actual vehicle, the width of the hysteresis varies depending on the vehicle speed, the steering angle, and the steering angular speed.

FIG. 7 shows a braking force command TBU depending on the vehicle speed. In this case, what is characteristic is that the brake force command TBU is made smaller as the vehicle speed increases in a low-speed state such as when starting from a vehicle stop state. By increasing the braking force command TBU relatively to the value of the function g (u), the brake torque generated by the powder brake 4 is larger than the drive torque of the electric motor 2 when the vehicle is stopped. Due to the increase of the self-aligning torque due to the increase of the vehicle speed, the steering reaction force is continuously connected to a state where the steering reaction torque becomes larger than the brake torque.

For example, when the vehicle is started from a state in which the steering wheel is fully turned in a stationary state, the brake torque generated by the powder brake 4 is smaller than the drive torque of the electric motor 2 until the vehicle speed becomes several km / h. Therefore, the steering wheel maintains the same steering angle even when the driver releases the steering wheel. Further, when the vehicle speed is higher than several km / h, the driving torque of the electric motor 2 becomes larger than the braking torque generated by the powder brake 4, so that when the driver holds the steering wheel, the steering wheel is in the neutral position. You will feel the reaction to return to. As described above, by increasing the value of the function g (u) as the vehicle speed increases, and decreasing the brake force command TBU as the vehicle speed increases, a low speed state such as when starting from a vehicle stop state is obtained. Can appropriately simulate the steering reaction force.

FIG. 8 shows a braking force command TBa based on the steering angle. FIG. 9 shows a braking force command TBV based on the steering angular velocity.

The steering reaction force command Th to the motor drive circuit 8 and the command (TBU + TBa + TBV) to the brake drive circuit 9 described above are calculated by the personal computer 11 shown in FIG. It is converted to an analog value by an analog converter. The torque of the electric motor 2 and the braking force of the powder brake 4 are controlled based on the analog signal.

As described above, in this embodiment, the self-aligning torque for the front wheels and the steering reaction force due to the caster effect are obtained, and the steering reaction force is weighted by the function of the slip angle βf of the front wheels to obtain the power steering mechanism of the actual vehicle. Can produce a simulated steering reaction force.

Further, in this embodiment, the vehicle speed-sensitive power steering is mounted by increasing the steering reaction torque as the vehicle speed increases and decreasing the frictional force as the vehicle speed increases in a low vehicle speed state. In the vehicle, the steering reaction force when the vehicle is stopped and the steering reaction force at low speed such as when starting from a stopped state can be simulated well. Further, in this embodiment, the powder braking force is determined in consideration of the vehicle speed, the steering angle, and the steering angular speed, and the hysteresis characteristic of the steering reaction force can be simulated well.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a relationship between a torque Mc associated with running resistance due to a caster effect and a steering angle θh according to the embodiment of the present invention.

FIG. 3 shows a self-aligning torque M according to the embodiment of the present invention.
For calculating the torque Mc associated with the running resistance due to the caster effect

FIG. 4 is a diagram illustrating a function for weighting by a steered wheel slip angle according to the embodiment of the present invention;

FIG. 5 is a diagram showing a function for performing weighting based on a vehicle speed when calculating a steering reaction force of a speed-sensitive power steering in the embodiment of the present invention.

FIG. 6 is a diagram showing a hysteresis of a steering reaction force according to the embodiment of the present invention.

FIG. 7 shows a braking force command T based on vehicle speed according to the embodiment of the present invention.
Diagram representing bu

FIG. 8 is a diagram showing a braking force command Tba depending on a steering angle according to the embodiment of the present invention.

FIG. 9 is a diagram showing a braking force command Tbv based on a steering angular velocity according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 steering wheel 2 electric motor 3 flat belt car 4 powder brake 5 flat belt 6 accelerator 7 brake 8 motor drive circuit 9 brake drive circuit 10 pulse generator 11 personal computer

Claims (1)

(57) [Claims] 1. A steering angle detecting means for detecting a steering angle of a steering wheel; a vehicle speed detecting and calculating means for detecting or calculating a vehicle speed of a vehicle; and a determining means for determining whether or not the vehicle is stopped based on the vehicle speed. A slip angle calculating means for calculating a slip angle of a steered wheel based on the vehicle speed and the steering angle; calculating a steering reaction torque based on the steering angle, the vehicle speed and the slip angle; In the low state,
Steering reaction torque calculation means for increasing the steering reaction torque as the vehicle speed increases, friction force calculation means for decreasing the friction force as the vehicle speed increases, weighting the steering reaction torque based on the slip angle A steering reaction torque correction means for calculating a corrected steering reaction torque by performing a steering reaction force applied to a steering wheel based on the frictional force when the vehicle is in a stopped state. A steering reaction force control device that controls a steering reaction force applied to a steering wheel based on the corrected steering reaction torque and the frictional force when the vehicle is in a state.