JP4144467B2 - Vehicle steering system - Google Patents

Description

  The present invention belongs to the technical field of vehicle steering devices in steer-by-wire systems.

This type of prior art includes a steering control unit 33 that controls the steering actuator 2 based on the target steering angle δ ^*, and the control gain of the steering control unit 33 is changed by a gain setting unit 35. Steering devices are known.

The gain setting unit 35 sets a large control gain when the turning steering detection unit 362 detects the turning steering. Further, when the return steering detection unit 363 detects the return steering, the control gain is set small. Thereby, it is possible to achieve both good responsiveness at the time of turning steering and smoothness at the time of return steering (for example, see Patent Document 1).
JP 2002-46639 A (FIG. 2)

  However, in the above prior art, for example, when the driver intentionally steers the steering continuously from side to side, such as slalom running, the control gain is frequently changed, so that it is difficult to steer the vehicle. was there.

  The present invention has been made paying attention to the above-mentioned problem, and an object of the present invention is a vehicle capable of achieving both a smooth return to the neutral position of the steering means during non-steering and ensuring the stability of vehicle steering. An object of the present invention is to provide a steering apparatus.

In order to achieve the above object, according to the present invention, the steering control means includes a driver steering determination unit that determines whether or not the driver is steering the steering means, and a steering angular velocity of the steering reaction force when the driver is steering. And a steering reaction force characteristic controller that changes the damping coefficient when the driver is not steering.

Therefore, in the present invention, when the driver is not steering, the damping coefficient with respect to the steering angular velocity of the steering reaction force is changed, so that the steering means can be returned to the neutral position at an appropriate speed. On the other hand, when the driver returns the steering means to the neutral position by his / her steering, the damping coefficient is kept constant, so that the driver can easily predict the vehicle behavior with respect to his / her steering input. That is, it is possible to achieve both a smooth return to the neutral position of the steering means during non-steering and ensuring the stability of vehicle steering.

  The best mode for carrying out the vehicle steering system of the present invention will be described below based on the first and second embodiments.

First, the configuration will be described.
FIG. 1 is a configuration diagram of a vehicle steering apparatus according to a first embodiment.
The vehicle steering apparatus according to the first embodiment includes a steering wheel 1, a steering reaction force actuator 2, a steering torque sensor (steering torque detection means) 3, a steering angle sensor (steering angle detection means) 4, and steered wheels 5. The transmission unit 6, the steering gear 7, the turning actuator 8, the turning angle sensor 9, a steering control device (steering control means) 10, and a vehicle speed sensor 11 are provided.

  The steering torque sensor 3 detects a steering torque generated between the steering wheel 1 and the steering reaction force actuator 2. The steering angle sensor 4 detects the steering angle of the steering wheel 1. The steered angle sensor 9 detects the steered angle of the steered wheels 5. The vehicle speed sensor 11 detects the speed of the vehicle. The outputs of these sensors are input to the steering control device 10.

  The steering control device 10 calculates the steering reaction force generated by the steering reaction force actuator 2 based on the output of each sensor, and calculates the control amount of the turning actuator 8 that drives the steering gear 7. The force in the vehicle lateral direction output from the steering gear 7 is transmitted to the steered wheels 5 via the transmission unit 6, and the steered angle of the steered wheels 5 is changed according to the drive amount of the steering gear 7.

  With the above configuration, the vehicle steering apparatus according to the first embodiment realizes a so-called steer-by-wire function that can arbitrarily change the characteristic of the turning angle with respect to the driver's steering input.

Next, the configuration of the steering control device 10 is shown in FIG.
In FIG. 2, outputs from the steering angle sensor 4 and the steering torque sensor 3 are input to a driver steering determination unit 10 a set in the steering control device 10, and outputs from the steering torque sensor 3, the steering angle sensor 4, and the vehicle speed sensor 11. Is input to the steering reaction force calculation unit (steering reaction force characteristic control unit) 10b and the turning angle calculation unit 10c set in the steering control device 10.

  In the driver steering determination unit 10 a, whether the driver is steering the steering wheel 1 by applying a steering force based on the outputs of the steering torque sensor 3 and the steering angle sensor 4, or neutralized by the steering reaction force actuator 2. It is determined whether the steering wheel 1 is steered by using the force to return to the position.

  The steering reaction force calculation unit 10b calculates a target steering reaction force based on the outputs of the steering torque sensor 3, the steering angle sensor 4 and the vehicle speed sensor 11 and the determination result of the driver steering determination unit 10a. A command value to the steering reaction force actuator 2 for generating a force is calculated.

  The target steering reaction force is set based on a steering torque coefficient set according to the steering angle and a damping coefficient set according to the steering angular velocity. At this time, the larger the steering torque coefficient and the smaller the damping coefficient, the larger the target steering reaction force. On the other hand, the smaller the steering torque coefficient and the larger the damping coefficient, the smaller the target steering reaction force.

  The turning angle calculation unit 10c calculates a target turning angle based on the outputs of the steering torque sensor 3, the steering angle sensor 4, and the vehicle speed sensor 11, and turns the turning wheel 5 so as to have the target turning angle. A command value to the actuator 8 is calculated.

[Damping coefficient setting control processing]
FIG. 3 is a flowchart showing the flow of the damping coefficient setting control process performed by the driver steering determination unit 10a and the steering reaction force calculation unit 10b of the steering control device 10, and each step will be described below.

  In step S300, the system is activated with the ignition key switch turned on as a trigger, and the process proceeds to step S301.

In step S301, an initial value η ₁ of a damping coefficient for the steering angular velocity of the steering reaction force is set, and the process proceeds to step S302.
This is a means for notifying the driver that the turning angle has suddenly increased when the steering gear ratio (steering angle / steering angle) is set to be smaller than usual, such as during low-speed driving. Also used as

  In step S302, signals from the steering torque sensor 3 and the steering angle sensor 4 are input, and the process proceeds to step S303.

  In step S303, the direction in which torque is generated and the steering angular velocity are calculated from the output results of the steering torque sensor 3 and the steering angle sensor 4 obtained in step S302, and the process proceeds to step S304.

  In step S304, it is determined whether or not the driver is steering in the neutral direction. If YES, the process moves to step S306, and if NO, the process moves to step S305.

  In step S305, it is determined whether or not the steering gear ratio is larger than a predetermined value set in advance. If YES, the process proceeds to step S308. If NO, the process proceeds to step S307.

In step S306, the damping coefficient is held at the initial value η ₁ and this control is terminated.

In step S307, the damping coefficient of the steering reaction force is set to a value η ₂ that is larger than the initial value η ₁ , and this control ends.

In step S308, the damping coefficient of the steering reaction force is set to a value η ₃ that is smaller than the initial value η ₁ , and this control ends.

[Damping coefficient setting control action]
When the driver is steering back to the neutral position, in the flowchart of FIG. 3, the process proceeds from step S301 to step S302, step S303, step S304, and step S306. In step S306, the damping coefficient is the initial value η ₁ is kept. That is, since the steering reaction force characteristic of the steering reaction force actuator 2 is constant, it is easy for the driver to predict the vehicle behavior with respect to his / her steering input, and the stability of vehicle steering is ensured.

When the driver is not returning to the neutral position and the steering gear ratio is equal to or less than the predetermined value, in the flowchart of FIG. 3, from step S301 → step S302 → step S303 → step S304 → step S305 → step S307 It will be the flow to go. That is, in step S307, the damping coefficient is set to η ₂ that is larger than the initial value η _1, and a steering reaction force that is smaller than that during return steering is set.

If the driver is not returning to the neutral position and the steering gear ratio is larger than the predetermined value, in the flowchart of FIG. 3, the process proceeds from step S301 to step S302 to step S303 to step S304 to step S305 to step S308. It will be the flow to go. That is, in step S308, the damping coefficient is set to η ₃ which is smaller than the initial value η _1, and a larger steering reaction force is set than when returning steering is performed.

[Return steering judgment logic]
Here, in order to facilitate the following description, the direction in which the torque is generated is positive when the steering wheel 1 side is generated in the clockwise direction with respect to the motor side of the steering reaction force actuator 2. . Similarly, the direction in which the steering angle changes is defined as positive when the steering wheel 1 is clockwise when viewed from the driver.

  The steering reaction force applied by the steering reaction force actuator 2 is added so as to return in the direction in which the vehicle goes straight. Therefore, when the driver weakens the steering force after steering the steering wheel 1 clockwise, the steering wheel 1 starts to return to the neutral position by the torque of the steering reaction force actuator 2. At this time, as shown in FIG. 4A, the steering angular velocity rotates in the negative direction (left rotation), and the torque is output in the positive direction.

  Here, if the driver tries to turn the steered wheels 5 in the reverse direction quickly, the driver tries to return faster than the return by the steering reaction force actuator 2, so that the steering angular velocity is negative as shown in FIG. It rotates in the direction (left rotation), and torque is also output in the negative direction.

  Similarly, if the steering force is weakened after the driver steers the steering wheel 1 counterclockwise, the steering angular velocity rotates in the positive direction (right rotation) and the torque is negative as shown in FIG. Is output in the direction of.

  On the other hand, when the driver tries to turn the steered wheels 5 in the reverse direction quickly, as shown in FIG. 4D, the steering angular velocity rotates in the positive direction (right rotation), and the torque is also output in the positive direction. The

  From the above, when the steering wheel 1 returns to the neutral position, it can be distinguished from the steering torque and the steering angular velocity whether the driver is performing return steering or whether the driver is returning to the neutral position by the torque of the steering reaction force actuator 2. .

Next, the effect will be described.
In the vehicle steering apparatus according to the first embodiment, the following effects can be obtained.

(1) Since the steering control device 10 keeps the damping coefficient at the initial value η ₁ when the driver is performing the return steering, it is easy to predict the vehicle behavior with respect to the driver's steering input at the time of the return steering. Can be ensured.

(2) When the driver is not performing return steering and the steering gear ratio is small, the steering control device 10 changes the damping coefficient to η ₂ that is larger than the initial value η _1. It is possible to prevent the return to the neutral position from deviating from the driver's steering feeling during traveling.

For example, during low-speed running of the garage or the like, in order to steer offload driver, if is set to be smaller than the normal steering gear ratio, the damping coefficient remains at the initial value eta _1, the neutral position The speed to return to is too fast, causing a deviation from the driver's steering feeling. Therefore, in this case, the return suitable for the steering feeling can be realized by increasing the damping coefficient.

(3) The steering control device 10 changes the damping coefficient to η ₃ smaller than the initial value η ₁ when the steering gear ratio is large when the driver is not performing return steering. It is possible to prevent the return to the neutral position from deviating from the driver's steering feeling.

For example, if the steering gear ratio is set larger than usual to improve straight-line stability during high-speed driving, if the damping coefficient remains at the initial value η ₁ , the speed to return to the neutral position is too slow As a result, a deviation from the steering feeling of the driver occurs. Therefore, in this case, by making the damping coefficient small, it is possible to realize a return that matches the driver's steering feeling.

  (4) Since the driver steering determination unit 10a determines that the driver is steering when the steering angular velocity and the steering torque are acting in the same direction, the driver steering determination unit 10a can reliably determine the presence or absence of return steering of the driver.

Next, Example 2 will be described.
Since the configuration of the second embodiment is the same as that of the first embodiment, the description thereof is omitted.

Next, the operation will be described.
[Steering torque coefficient setting control process]
FIG. 5 is a flowchart showing the flow of the steering torque coefficient setting control process performed by the driver steering determination unit and the steering reaction force calculation unit of the steering control device.

  In step S500, the system is activated with the ignition key switch turned on as a trigger, and the process proceeds to step S501.

In step S501, an initial value T ₁ (θ) of the steering torque coefficient with respect to the steering angle of the steering reaction force is set, and the process proceeds to step S502.

  In step S502, signals from the steering torque sensor 3 and the steering angle sensor 4 are input, and the process proceeds to step S503.

  In step S503, the direction in which torque is generated and the steering angular velocity are calculated from the output results of the steering torque sensor 3 and the steering angle sensor 4 obtained in step S502, and the process proceeds to step S504.

  In step S504, it is determined whether or not the driver is steering in the neutral direction. If YES, the process moves to step S506, and if NO, the process moves to step S505.

  In step S505, it is determined whether or not the steering gear ratio is larger than a predetermined value set in advance. If YES, the process moves to step S508, and if NO, the process moves to step S507.

In step S506, the steering torque coefficient is maintained at the initial value T ₁ (θ), and this control is terminated.

In step S507, the steering torque coefficient is set to a value T ₂ (θ) smaller than the initial value T ₁ (θ), and this control is terminated.

In step S508, the steering torque coefficient is set to a value T ₃ (θ) larger than the initial value T ₁ (θ), and this control is terminated.

[Steering torque coefficient setting control action]
When the driver is steering back to the neutral position, the flow proceeds from step S501 to step S502, step S503, step S504, and step S506 in the flowchart of FIG. 5. In step S506, the steering torque coefficient is an initial value. T ₁ (θ) is maintained. That is, since the steering reaction force characteristic of the steering reaction force actuator 2 is kept constant, it is easy for the driver to predict the vehicle behavior with respect to his / her steering input, and the stability of vehicle steering is ensured.

When the driver is not returning to the neutral position and the steering gear ratio is equal to or less than the predetermined value, in the flowchart of FIG. 5, from step S501 → step S502 → step S503 → step S504 → step S505 → step S507. It will be the flow to go. That is, in step S507, the steering torque coefficient is small T ₂ than the initial value _{T 1 (θ) (θ)} , small steering reaction force is set than when you return steering.

When the driver is not returning to the neutral position and the steering gear ratio is larger than the predetermined value, in the flowchart of FIG. 5, from step S501 → step S502 → step S503 → step S504 → step S505 → step S508. It will be the flow to go. That is, in step S508, the steering torque coefficient is set to T ₃ (θ) that is larger than the initial value T ₁ (θ), and a steering reaction force that is larger than that during reverse steering is set.

Next, the effect will be described.
In the vehicle steering apparatus according to the second embodiment, the following effects can be obtained.

(5) Since the steering control device 10 keeps the steering torque coefficient at the initial value T ₁ (θ) when the driver is performing the return steering, it is easy to predict the vehicle behavior with respect to the steering input of the driver during the return steering. Thus, the stability of vehicle operation can be secured.

(6) The steering control device 10 changes the steering torque coefficient to T ₂ (θ) smaller than the initial value T ₁ (θ) when the driver is not performing return steering and the steering gear ratio is small. Therefore, when the vehicle is traveling at a low speed such as in a garage, it is possible to prevent the return to the neutral position from being too fast and deviating from the driver's steering feeling.

(7) The steering control device 10 changes the steering torque coefficient to T ₃ (θ) larger than the initial value T ₁ (θ) when the driver is not performing return steering and the steering gear ratio is large. Therefore, it is possible to prevent the return to the neutral position from being too slow during driving at high speed and deviating from the driver's steering feeling.

(Other examples)
The best mode for carrying out the present invention has been described based on the first and second embodiments. However, the specific configuration of the present invention is not limited to the first and second embodiments, and departs from the gist of the invention. Even if there is a design change or the like within a range not to be included, it is included in the present invention.

  For example, as a specific means for changing the steering reaction force characteristic, the damping coefficient is changed in the first embodiment and the steering torque coefficient is changed in the second embodiment. However, both the damping coefficient and the steering torque coefficient are changed. A configuration may be adopted.

1 is a configuration diagram of a vehicle steering device (first embodiment). FIG. 1 is a configuration diagram of a steering control device 10. FIG. 7 is a flowchart illustrating a flow of a damping coefficient setting control process performed in the steering control device (first embodiment). It is explanatory drawing which shows the return steering determination logic of a driver. 10 is a flowchart showing a flow of steering torque coefficient setting control processing executed in the steering control device (Example 2).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering reaction force actuator 3 Steering torque sensor 4 Steering angle sensor 5 Steering wheel 6 Transmission part 7 Steering gear 8 Steering actuator 9 Steering angle sensor 10 Steering control apparatus 10a Driver steering determination part 10b Steering reaction force calculation part 10c Steering angle calculation unit 11 Vehicle speed sensor

Claims (4)

Steering means that is not mechanically connected to a steering actuator that steers the steered wheels;
A steering reaction force actuator that applies a steering reaction force to the steering means;
Steering angle detection means for detecting a steering angle of the steering means;
Steering torque detection means for detecting input torque to the steering means;
Steering control means for variably controlling the output torque of the steering reaction force actuator and the driving amount of the turning actuator according to the detected steering angle and steering torque,
In a vehicle steering apparatus comprising:
In the steering control means,
A driver steering determination unit that determines whether the driver is steering the steering means;
A steering reaction force characteristic control unit that maintains a constant damping coefficient with respect to the steering angular velocity of the steering reaction force when the driver is steering, and changes the damping coefficient when the driver is not steering;
Vehicle steering apparatus, wherein a is provided. Steering means that is not mechanically connected to a steering actuator that steers the steered wheels;
A steering reaction force actuator that applies a steering reaction force to the steering means;
Steering angle detection means for detecting a steering angle of the steering means;
Steering torque detection means for detecting input torque to the steering means;
Steering control means for variably controlling the output torque of the steering reaction force actuator and the drive amount of the steering actuator according to the detected steering angle and steering torque,
In a vehicle steering apparatus comprising:
In the steering control means,
A driver steering determination unit that determines whether the driver is steering the steering means;
A steering reaction force characteristic control unit that maintains a constant steering torque coefficient with respect to the steering angle of the steering reaction force when the driver is steering, and changes the steering torque coefficient when the driver is not steering;
Vehicle steering apparatus, wherein a is provided. The vehicle steering apparatus according to claim 1 or 2,
The steering reaction force characteristic control unit sets the magnitude of the steering reaction force characteristic to be changed according to the magnitude of the steering gear ratio, which is the ratio of the steering angle of the steering means to the turning angle of the steered wheels. A vehicle steering system. The vehicle steering apparatus according to any one of claims 1 to 3,
The driver steering determination unit determines that the driver is steering when the steering angular velocity and the steering torque are acting in the same direction .

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