JP2002370658A - Steering reaction force control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and faithfully realize a steering reaction characteristic in a steer-by-wire type vehicle when steering a steering wheel at a fast rotating speed in a conventional vehicle having a steering shaft. SOLUTION: A control unit 1 corrects a phase lag on the basis of a steering speed and a vehicle speed V detected by a vehicle speed sensor 2, and calculates a rigidity component Tp of steering reaction by applying proportional gain Kp of the rigidity component Tp determined according to a detecting result of the vehicle speed sensor 2, an acceleration sensor 3, and a yaw rate sensor 4 for reflecting a traveling state of one's own vehicle. The control unit 1 calculates a control desired value T of a steering reaction force control motor 6 by adding a viscosity component Td, a friction component Tf, and the rigidity component Tp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a steering reaction force control device, and more particularly to a steering reaction force control device suitable for use in a steer-by-wire type vehicle.

[0002]

2. Description of the Related Art Conventionally, in the field of automobiles, which are typical vehicles, there is a conventional vehicle having a steering mechanism in which a steering wheel operated by a driver and front wheels (steering wheels) are mechanically connected via a steering shaft. 2. Description of the Related Art Vehicles (hereinafter, referred to as conventional vehicles having a steering shaft) are widely used, and a general driver uses a steering wheel to mainly operate the conventional vehicle of this type mainly by tactile sensation of hands and arms. It is known that a driver who is familiar with the perceived steering sensation (steering reaction force characteristic) and is proficient in driving recognizes the behavior and running state of the vehicle he or she drives based on the steering sensation.

FIG. 8 is a diagram illustrating a steering reaction force characteristic of a conventional vehicle having a steering shaft at a speed of 100 km / h. FIG. 8A shows a steering frequency of 0.25 Hz.
FIG. 8B shows a case where the steering frequency is 0.5 Hz.

In the steering reaction force characteristics shown in FIGS. 8A and 8B, the horizontal axis represents the steering angle of the steering wheel generated by the driver's steering, and the vertical axis represents the steering wheel generated in accordance with the steering. And the steering reaction force characteristic is, for example, rightward (+ direction).
When the driver turns the steering wheel, a steering reaction force is generated that pulls back the steering wheel, but the magnitude of the reaction force is saturated at a certain steering angle.

The steering reaction force received by the driver at the time of steering includes a self-aligning torque corresponding to the turning of the steered wheels, but the steering speed by the driver is high (the steering frequency is high). In the case of, the steering speed is low (the steering frequency is low) as compared with the case of FIG.
Since the rise of the self-aligning torque corresponding to the steering is slow, a phase delay of the steering reaction force with respect to the steering angle occurs near the neutral position of the steering angle (that is, the steering angle θ ≒ ± 10 °), and the driver receives the steering. The feel of the reaction force is no longer certain.

[0006] In recent years, for example,
As disclosed in Japanese Patent Application No. 0-198453, there has been proposed a steer-by-wire type vehicle including a steering mechanism in which a steering wheel operated by a driver and a front wheel are mechanically separated from each other. Therefore, it is necessary to reproduce the steering dynamics of a conventional vehicle having a steering shaft with which the driver is familiar. For this reason, in a steer-by-wire type vehicle, control is performed to apply a steering reaction force to the steering wheel based on a steering reaction force characteristic set according to the vehicle speed of the vehicle and the steering angle of the steering wheel. .

[0007]

FIG. 9 is a diagram illustrating a steering reaction force characteristic of a steer-by-wire type conventional vehicle at a speed of 100 km / h. The steering reaction force of a conventional vehicle having a steering shaft is shown. In order to realize the characteristics,
9 shows characteristics of control for applying a steering reaction force performed in a steer-by-wire type conventional vehicle.

FIG. 9A shows that the steering frequency is 0.2
FIG. 9B shows a case where the steering frequency is 0.5 Hz. FIG. 9B shows a case where the steering frequency is 0.5 Hz. The horizontal axis indicates the steering angle of the steering wheel generated by the driver's steering, and the vertical axis indicates the steering wheel automatically according to the steering. The basic shape of any of the steering reaction force characteristics is the same as that of the conventional vehicle having the steering shaft described with reference to FIG.

[0009] However, in the conventional steer-by-wire type vehicle, the steering speed by the driver is high (the steering frequency is high). In the case of FIG. 9A, the steering speed is low (the steering frequency is low). 9 (b), the vicinity of the neutral position of the steering angle (that is, the steering angle θ ≒ ± 1).
0 °), a phase advance of the steering reaction force with respect to the steering angle occurs. This situation is a completely opposite characteristic to the case of the conventional vehicle having the steering shaft described above. In the case of the conventional vehicle having the steering shaft, the driver cannot feel the steering reaction force received by the driver. In conventional vehicles of the by-wire type,
In such a situation where the steering speed is high, the self-aligning torque quickly rises, and the driver feels the steering reaction force surely.

Accordingly, the present invention provides a steering reaction force that can easily and faithfully realize a steering reaction force characteristic when a steering wheel is steered at a high rotational speed in a conventional vehicle having a steering shaft in a steer-by-wire type vehicle. It is intended to provide a control device.

[0011]

In order to achieve the above object, a steering reaction force control device according to the present invention has the following configuration.

That is, a steering wheel operated by a driver and a front wheel are provided in a steer-by-wire type vehicle having a steering mechanism in which the front wheel is mechanically separated, and the vehicle speed and the steering angle of the steering wheel are determined. A steering reaction force control device including control means for applying a steering reaction force to the steering wheel based on a steering reaction force characteristic set in accordance with the steering reaction force characteristic. A phase characteristic of a rigid component of a steering reaction force generated according to the steering angle among a plurality of types of force components constituting the reaction force is a frequency characteristic that is delayed with respect to the steering angle.

[0013] In a preferred embodiment, the control means sets the ratio of the stiffness component in the steering reaction force characteristic to a value larger than a predetermined value, among the plurality of types of force components constituting the steering reaction force. The maximum value of the viscous component generated according to the steering speed of the steering wheel may be restricted.

Further, for example, the control means determines the magnitude of the stiffness component in the steering reaction force characteristic in accordance with at least one of the longitudinal acceleration of the vehicle, the vehicle speed of the vehicle, and the yaw rate of the vehicle. Correct it.

[0015]

According to the present invention, the steering reaction force characteristic of a conventional vehicle having a steering shaft when the steering wheel is steered at a high rotational speed can be easily and faithfully measured in a steer-by-wire type vehicle. Provision of a steering reaction force control device that is realized is realized.

That is, according to the first aspect of the present invention, in a conventional vehicle having a steering shaft, the same steering reaction force characteristic (for example, self-aligning torque) as when the driver steers the steering wheel at a high rotational speed.
Can be faithfully realized by a simple configuration in a steer-by-wire type vehicle, so that the driver can easily recognize the behavior of the vehicle from the steering wheel.

According to the second aspect of the present invention, in a conventional vehicle having a steering shaft, a steering torque characteristic when a driver steers a steering wheel at a high rotational speed is ensured in a steer-by-wire type vehicle. can do.

According to the third aspect of the present invention, the steer
In the steering reaction force characteristic of a by-wire type vehicle, for example, when the acceleration increases, the rigidity decreases, and when the deceleration increases, the rigidity increases. Changes in steering reaction force characteristics (for example, self-aligning torque) can be easily and faithfully reproduced.

According to the fourth aspect of the present invention, the steer
In the steering reaction force characteristic of a by-wire type vehicle, for example, by increasing the rigidity and increasing the phase delay as the vehicle speed increases, the steering reaction force characteristic according to the traveling speed in a conventional vehicle having a steering shaft (for example, Changes in self-aligning torque)
It can be easily and faithfully reproduced.

According to the fifth aspect of the present invention, the steer
In a steering reaction force characteristic of a by-wire type vehicle, for example, by increasing the rigidity as the yaw rate increases, a change in the steering reaction force characteristic (for example, self-aligning torque) according to the yaw rate in a conventional vehicle having a steering shaft. Can be easily and faithfully reproduced.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a steering reaction force control device according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a steering mechanism of a steer-by-wire type vehicle equipped with a steering reaction force control device according to this embodiment. The steering mechanism shown in FIG. This is a steer-by-wire type mechanism in which a steering wheel 8 to be operated and a front wheel (steering wheel) 10 are mechanically separated.

The control unit 1 steers the front wheels 10 by driving the front wheel steering angle actuator 7 according to the rotation angle (steering angle) θ of the steering wheel 8 detected by the steering angle sensor 5.

When driving the front wheel steering angle actuator 7, the control unit 1 controls the vehicle speed V of the vehicle detected by the vehicle speed sensor 2 and the acceleration (including deceleration) of the vehicle detected by the acceleration sensor 3. On the basis of the turning state (yaw rate) of the host vehicle detected by the yaw rate sensor 4 and the steering angle θ, the steering reaction force characteristic of a conventional vehicle having a steering shaft is reproduced on the rotation center axis of the steering wheel 8. By driving the arranged steering reaction force control motor 6, a steering reaction force is applied to the steering wheel 8.

In the present embodiment, a steer-by-wire type vehicle having such a configuration is employed,
In order to solve the problems in the conventional steer-by-wire type vehicle described above in "Problems to be Solved by the Invention" with reference to FIG. Attention is paid to the rigidity component among the four force components constituting the force.

That is, in a steer-by-wire type vehicle, a steering reaction force to be applied in accordance with steering of a steering wheel by a driver generally includes a “rigid component”,
“Viscous component”, “friction component”, and “inertial component”
It is known that it consists of two force components.-"Rigidity component" represents a force component generated according to the steering angle of the steering wheel.-"Viscous component" is generated according to the steering speed of the steering wheel. The "friction component" represents a force component generated by mechanical friction caused by steering of the steering wheel.The "inertial component" represents a force component corresponding to the steering of the steering wheel. Represents a force component corresponding to the acceleration component to be applied.

Here, the steering reaction force is equal to the steering force input to the steering wheel by the driver when the steering wheel is not rotating.

In this embodiment, in the steering reaction force characteristic of the steering mechanism of the steer-by-wire type vehicle shown in FIG. A frequency characteristic that delays with respect to the steering angle θ detected by the steering angle sensor 5 is realized.

Incidentally, since the configuration itself of each block shown in FIG. 1 is currently common, detailed description in this embodiment is omitted.

FIG. 2 is a block diagram for explaining control processing performed by the steering reaction force control device according to the present embodiment.
FIG. 2 is a diagram schematically illustrating functions realized by a microcomputer (not shown) provided in the control unit 1 executing a control program stored in advance.

In FIG. 1, the control unit 1 includes a steering wheel 8 detected by a steering angle sensor 5.
The steering speed is calculated based on the rotation angle (steering angle) θ, and the proportional gain Kd of the viscosity component Td is added to the calculated steering speed.
And the correction according to the steering speed is performed to calculate the viscosity component Td of the steering reaction force.

The control unit 1 converts the steering speed into a sign and applies a proportional gain K to the friction component Tf so as to apply a steering reaction force in a direction opposite to the steering direction by the driver.
By applying f, the friction component Tf of the steering reaction force is calculated.

Further, the control unit 1 corrects the phase delay based on the steering speed and the vehicle speed V detected by the vehicle speed sensor 2 (details will be described later), and sets the vehicle speed to reflect the traveling state of the host vehicle. Sensor 2, acceleration sensor 3,
Further, a rigidity component Tp of the steering reaction force is calculated by applying a proportional gain Kp of the rigidity component Tp determined according to the detection result of the yaw rate sensor 4.

Then, the control unit 1 obtains a control target value T of the steering reaction force control motor 6 by adding the calculated viscosity component Td, friction component Tf, and rigidity component Tp,
By driving the steering reaction force control motor 6 by feedback control based on the control target value T, a steering reaction force is applied to the steering wheel 8.

Here, the inertia component of the steering reaction force does not affect the phase delay of the steering reaction force with respect to the steering angle θ near the neutral position of the steering angle (that is, the steering angle θ ≒ ± 10 °). This need not be considered in the form.

Incidentally, a general method may be employed for the method of calculating the steering speed and the feedback control of the steering reaction force control motor 6, and therefore a detailed description in this embodiment is omitted.

FIG. 3 is a flowchart of the control process of the control unit 1 in the present embodiment.
3 shows a procedure of processing performed by a CPU (not shown).

In FIG. 5, step S1: the detection value of each sensor described with reference to FIG. 1 is updated.

Step S2: A steering speed θ 'is calculated based on the steering angle θ of the steering wheel 8 detected by the steering angle sensor 5.

Step S3: A table representing the characteristic as shown in FIG. 4 in which the time constant τ is corrected to a large value according to the vehicle speed is stored in the memory in advance, and the vehicle speed sensor 2
By referring to the table according to the vehicle speed V of the host vehicle detected by the control unit 1, the magnitude of the delay of the rigidity component Tp of the steering reaction force T to be realized by the control unit 1 in the current control cycle is determined.

Step S4: The steering angle θ1 of the phase delay with respect to the steering angle θ detected in step S1, and s is the Laplace operator, and θ1 = 1 / (1 + τs) × θ (1) It is calculated by (1).

Step S5: FIGS. 5A to 5C
Are stored in advance in a memory, and the vehicle speed V of the own vehicle detected by the vehicle speed sensor 2, the acceleration α of the own vehicle detected by the acceleration sensor 3, and the yaw rate sensor 4 The magnitude of the proportional gain Kp of the stiffness component Tp of the steering reaction force T is determined by referring to each table according to the determined yaw rate φ of the own vehicle.

Step S6: Stiffness component Tp of steering reaction force T
Is the steering angle θ of the phase delay calculated in step S4.
1. Proportional gain K of the rigidity component calculated in step S5
It is calculated based on p. Specifically, for example, Tp = (sign θ1 × (1−exp (−sign θ1 × θ1 × Kp)) × Kp1... (2).
1 is the maximum value of the proportional gain Kp of the rigidity component Tp.

Step S7: A table representing the characteristics as shown in FIG.
The maximum value of the viscosity component Td of the steering reaction force T is set by referring to the table according to the steering speed θ ′ calculated in Step 2.

Step S8: Viscous component Td of steering reaction force T
Is calculated based on the proportional gain Kd of the viscous component, the steering speed θ ′ calculated in step S2, and the limit of the maximum value set in step S7. Specifically, for example, Td = Kd × θ ′ (3). Here, the proportional gain Kd of the viscous component Td is an arbitrary constant, and may be set according to the steering reaction force characteristic to be realized in the target vehicle.

Step S9: Friction component Tf of steering reaction force T
Is calculated based on the proportional gain Kf of the friction component and the steering speed θ ′ calculated in step S2. Specifically, for example, Tf = sign θ ′ × (1−exp (−sign θ ′ × θ ′ × Kf1)) × Kf (4) Here, the proportional gain Kf of the friction component Tf is an arbitrary constant, and may be set according to the steering reaction force characteristic to be realized in the target vehicle. Kf1 is an arbitrary constant for stabilizing the steering reaction force control. Is a constant.

Step S10: The steering reaction force T to be achieved by the control unit 1 in the current control cycle is calculated by the following equation (5): T = Tp + Td + Tf (5).

Step S11: The steering reaction force control motor 6 is driven based on the steering reaction force T calculated in step S10, and the process returns to step S1.

FIG. 7 shows a control unit 1 according to this embodiment.
10 of steer-by-wire type vehicles equipped with
It is a figure which illustrates the steering reaction force characteristic at the time of 0 km / h running,
2 shows a characteristic of a steering reaction force T realized by the control unit 1.

FIG. 7A shows that the steering frequency is 0.2
7 (b) shows the case where the steering frequency is 0.5 Hz, the horizontal axis represents the steering angle θ of the steering wheel 8 detected by the steering angle sensor 3, and the vertical axis represents the steering reaction force control motor. 6 is a steering reaction force T applied to the steering wheel 8.

In any of the steering reaction force characteristics shown in FIGS. 7 (a) and 7 (b), the control processing by the control unit 1 described above causes the conventional vehicle having the steering shaft described with reference to FIG. The steering reaction force characteristic having substantially the same shape as the steering reaction force characteristic in the case is realized, and FIG.
The phase advance of the steering reaction force with respect to the steering angle, which has occurred in the conventional steer-by-wire type vehicle control described above with reference to (b), is eliminated.

That is, the control unit 1 calculates the frequency characteristic of the phase delay including the time constant τ, which increases as the own vehicle speed increases, as calculated in steps S3 and S4, and calculates the rigidity of the steering reaction force T. By reflecting on the component Tp, in the conventional steer-by-wire type vehicle control, the phase advance of the steering reaction force with respect to the steering angle, which occurs when the steering wheel is steered at a high rotation speed, can be eliminated. it can.

Further, the control unit 1 limits the viscosity component Td of the steering reaction force T by the maximum value calculated in step S7. (Origin) The periphery changes greatly and the linearity of the steering reaction force is greatly lost. However, in a conventional vehicle having a steering shaft, the straight line of the steering reaction force when the driver steers the steering wheel at a high rotation speed. Sex, steer by
It can be secured in a wire type vehicle.

In step S5, the control unit 1 corrects the proportional gain Kp according to the acceleration α of the host vehicle by referring to the table shown in FIG. 5C, thereby increasing the acceleration of the host vehicle. Therefore, the rigidity component Tp can be reduced, and the rigidity component Tp can be increased if the deceleration increases. Therefore, it is possible to reproduce the self-aligning torque that changes according to the ground load on the front and rear wheels of the vehicle during acceleration and deceleration. Thus, it is possible to simply and faithfully reproduce a change in the steering reaction force characteristic that occurs when a conventional vehicle having a steering shaft accelerates or decelerates.

In step S5, the control unit 1 corrects the proportional gain Kp according to the traveling speed V of the host vehicle by referring to the table shown in FIG. The rigidity component Tp can be increased, and the higher the vehicle speed, the greater the steering reaction force can be reproduced. In a conventional vehicle having a steering shaft, a change in the steering reaction force characteristic according to the traveling speed can be easily and faithfully performed. Can be reproduced.

In step S5, the control unit 1 corrects the proportional gain Kp according to the yaw rate φ of the vehicle by referring to the table shown in FIG. 5C. Since Tp can be increased, for example, the operational feeling in a situation where the behavior of the vehicle does not actually change even if the steering wheel is operated while traveling on a road having a small friction coefficient μ between the road surface and the front wheels is reproduced. This makes it possible to simply and faithfully reproduce the change in the steering reaction force characteristic according to the yaw rate in the conventional vehicle having the steering shaft.

As described above, according to the present embodiment, the steering reaction force characteristic when the steering wheel is steered at a high rotational speed in the conventional vehicle having the steering shaft is simple and faithful in the steer-by-wire type vehicle. Can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a steering mechanism of a steer-by-wire type vehicle equipped with a steering reaction force control device according to an embodiment.

FIG. 2 is a block diagram illustrating a control process performed by a steering reaction force control device according to the embodiment.

FIG. 3 is a flowchart of a control process of a control unit 1 in the embodiment.

FIG. 4 is a diagram exemplifying characteristics of a table referred to when correcting a delay time constant of a rigidity component of a steering reaction force T;

FIG. 5 is a diagram illustrating characteristics of a table referred to when correcting a proportional gain Kp of a rigidity component of a steering reaction force T;

FIG. 6 is a diagram illustrating characteristics of a table referred to when setting a maximum value of a viscosity component Td of a steering reaction force T;

FIG. 7 is a diagram exemplifying a steering reaction force characteristic of a steer-by-wire type vehicle equipped with the control unit 1 according to the present embodiment when the vehicle is traveling at 100 km / h.

FIG. 8 shows a conventional vehicle 10 having a steering shaft.
It is a figure which illustrates the steering reaction force characteristic at the time of 0 km / h running.

FIG. 9 shows a conventional steer-by-wire vehicle.
It is a figure which illustrates the steering reaction force characteristic at the time of 0 km / h running.

[Explanation of symbols]

 1: control unit, 2: vehicle speed sensor, 3: acceleration sensor, 4: yaw rate sensor, 5: steering angle sensor, 6: steering reaction force control motor, 7: front wheel steering angle actuator, 8: steering wheel, 10: front wheel ( Steering wheel),

Claims (5)

[Claims] 1. A steer-by-wire type vehicle having a steering mechanism in which a steering wheel operated by a driver and a front wheel are mechanically separated from each other. The steering wheel is controlled by a vehicle speed and a steering angle of the steering wheel. A steering reaction force control device comprising: a control unit that applies a steering reaction force to the steering wheel based on a steering reaction force characteristic set in accordance with the steering reaction force. The phase of a stiffness component of a steering reaction force generated according to the steering angle among a plurality of types of force components constituting the reaction force is a frequency characteristic that is delayed with respect to the steering angle. Power control device. 2. The method according to claim 1, wherein the control unit sets a ratio of the stiffness component in the steering reaction force characteristic to a value greater than a predetermined value.
2. The system according to claim 1, wherein a maximum value of a viscous component generated according to a steering speed of the steering wheel is regulated.
The steering reaction force control device as described in the above. 3. The vehicle according to claim 1, wherein the control unit corrects the magnitude of the stiffness component in the steering reaction force characteristic in accordance with a longitudinal acceleration of the vehicle. Steering reaction force control device. 4. The steering reaction force according to claim 1, wherein the control means corrects the magnitude of the stiffness component in the steering reaction force characteristic according to a vehicle speed of the vehicle. Control device. 5. The steering reaction force according to claim 1, wherein the control means corrects the magnitude of the stiffness component in the steering reaction force characteristic according to a yaw rate of the vehicle. Control device.