JP2003127886A - Vehicle steering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle steering apparatus forgiving a stable steering behavior as a skilled person does to a vehicle while compensating for the insufficiency of the derivative action of a person. SOLUTION: In the vehicle steering apparatus which has a target steering angle ratio or a target wheel turning angle set by steering a steering wheel toward a position where a vehicle arrives after a preset time so that the vehicle arrives at the position independently of a vehicle speed and which is feedback controlled so that an actual steering angle ratio or an actual wheel turning angle becomes the target steering angle ratio or the target wheel turning angle, the target steering angle ratio or the wheel turning angle is added and corrected depending on the steering angle speed of the steering wheel. Thus, the steering angle of steered wheel is automatically corrected corresponding to the steering angle speed given to the steering wheel by a driver, providing good maneuverability as a skilled person does without giving a great burden to the driver.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering system. 2. Description of the Related Art When driving a car, a driver draws information on a forward fixation point, that is, a travel path angle determined from a position of the vehicle to be located after a certain time as a target path angle in the mind. A steering angle for generating a yaw rate required to reach the target position after a time is input to the steering wheel. At this time, the steering angle given to the steering wheel is determined based on the yaw rate gain that the driver himself has gained. By the way, the applicant of the present invention has obtained an analysis result that a driver generally looks at about 1.2 seconds ahead when entering a curved road, and that the preview time does not depend on the vehicle speed. ing. That is, if the driver can reach the target point after 1.2 seconds by inputting the steering angle according to the target route recognized by the driver regardless of the vehicle speed, it is necessary to correct the yaw rate gain according to the vehicle speed, the lateral acceleration, and the like. It can be said that there is no longer. [0004] Based on such knowledge, by changing the interlocking state (steering angle ratio) between the input shaft and the output shaft according to the vehicle speed and the steering angle, the change of the yaw rate gain with respect to the actual steering angle is obtained. A vehicle steering system designed to reduce the size and thereby reduce the burden on the driver has already been proposed (see Japanese Patent Application Laid-Open No. 5-105106). [0005] However, in a machine such as an automobile in which the motion is directly controlled by a person, not only the responsiveness of the machine itself but also the machine itself,
In some aspects, motility is determined by human responsiveness. When the human control operation is regarded as a linear and continuous feedback control as shown in FIG. 5, the deviation ε from a target course ahead by a distance L in FIG. It is known that the human transfer function H (s) in this case can be expressed by, for example, the following equation when the proportional constant is h, the differential time is τD, and the dead time is τL. I have. H (s) = h (1 + τD · s) e− ^{τL · s} Among the human actions represented by the above equation, the proportional action is an action of outputting an output signal proportional to the magnitude of the input signal. In the differential operation, an output signal is output in proportion to the rate of change of the input signal per unit time. In the case of a human, the adaptation to the proportional operation is relatively easy (h is changed according to the vehicle behavior; for example, h is reduced at high speed so that the behavior is not unstable), but the differential operation is performed. In other words, there is a limit in adapting to the predicted control operation (changing τD), and it is possible to appropriately cope with the case where the forward gaze distance (L) can be appropriately set. Is known to be unable to provide a stable response. Further, it is well known that this differentiation operation includes many empirical factors, and that there is a large gap in the appropriateness of control between a beginner and an expert. In view of the above findings, a main object of the present invention is to provide a vehicle steering apparatus configured to reduce a change in yaw rate gain with respect to an actual steering angle in the same manner as in a skilled person. Is to be improved to obtain In order to achieve the above object, according to the present invention, the steering wheel is steered toward a position where the vehicle arrives after a predetermined time, thereby irrespective of the vehicle speed. A vehicle in which a target steering angle ratio or a target wheel turning angle is set such that the vehicle reaches the position, and feedback control is performed so that the actual steering angle ratio or the wheel turning angle becomes the target steering angle ratio or the target wheel turning angle. The steering device is characterized in that the target steering angle ratio or the target wheel turning angle is added and corrected based on the steering angular velocity of the steering wheel. [0011] According to this, the steering angle of the steered wheels is automatically corrected in accordance with the steering angular velocity given to the steering wheel by the driver, so that the steering operation can be performed without imposing a great burden on the driver. Stability can be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. In FIG. 1, when the vehicle is running on a certain target course while gazing forward by a distance L, the front wheel steering angle δ is given to the deviation ε from the target course at the front gazing point. Then, [0014] to organize δ / ε = h (1 + τD · s) e -τL · s e -τL · s = (1-τL · s) and considered by, δ / ε = h [1- (τL- τD) · s] When the above equation is modified with the differential value of the shift amount ε as ε ^* ( ^* is a differential value), δ = h · ε−h (τL−τD) ε ^* is obtained. . Here, since ε = y + Lθ−y _0L , δ = h · ε−h (τL−τD) · [Lθ ^* − (y ^* _0L)
−y ^* )]. Changing the proportional gain h is equivalent to changing the ratio between the steering angle of the steering wheel and the turning angle of the steered wheels. Therefore, by changing the steering angle ratio according to the vehicle speed and the steering angle, When the driver inputs the steering angle according to the target route that is recognized to be able to reach after 1.2 seconds, the steering angle of the steered wheels is automatically corrected, and regardless of the vehicle speed, the input steering wheel is input. Can be matched to the shift amount ε. In this case, the steering angular velocity of the steering wheel causes an excess or deficiency of the yaw rate. Therefore, in the present invention, the following equation is applied, and the deviation ε which is a differential operation with respect to the front wheel steering angle δ output by the driver is applied. Differential value of ε
^* A, by adding multiplied by some appropriate correction coefficient for correcting the derivative time τD human correction steering angle Keideruta ^*, is aimed to further stabilize the vehicle behavior to compensate for the response delay of the person. Δ = h · ε−h (τL−τD) · ε ^* + kδ ^* Next, a steer-by-wire steering apparatus to which the present invention is applied is a conceptual configuration diagram of FIG. 2 and FIG. This will be described with reference to the block diagram of FIG. This steer-by-wire steering system 1
Are steering wheel 2 steered by a driver, a steering angle sensor 3, a steering reaction force adding motor 4, and a steering torque sensor 5 attached to the steering wheel 2, a knuckle arm 7 and a tie rod A steering rod 9 connected via the steering rod 8, a steering motor 10 for giving a steering angle to the steered wheels 6 for driving the steering rod 9 in the axial direction, a vehicle speed sensor 11 for outputting the vehicle speed, The steering angle sensor 12 outputs the steering angle of the steering wheel 6 from the axial position, and the control device 13 controls the steering reaction force applying motor 4 and the steering motor 10. The steering wheel 2 is constantly urged toward the neutral position by an appropriate spring mechanism or the like (not shown). The control device 13 controls the steering reaction force adding motor 4 based on signals from the steering torque sensor 5 and the vehicle speed sensor 11.
And a turning control unit 15 that controls the steering motor 10 based on signals from the steering angle sensor 3, the vehicle speed sensor 11, and the turning angle sensor 12, and controls the steering reaction force. The additional motor 4 and the steering motor 10 can be controlled individually. The steering reaction force control unit 14 sets a target steering reaction force based on a vehicle speed signal from the vehicle speed sensor 11 and a steering angle command signal from the turning control unit 15.
6 and a steering reaction force for calculating a drive current of the steering reaction force motor 4 for matching the output value (actual steering torque) of the steering torque sensor 5 with the target steering reaction force set by the target steering reaction force setting unit 16. It comprises a motor control signal output section 17 and a steering reaction force motor drive circuit 18 for controlling electric power actually supplied to the steering reaction force motor 4 according to the current command value. With the above configuration, a force (reaction force) in a direction opposite to the operation direction of the driver is applied to the steering wheel 2. This steering reaction force is detected, for example, by the vehicle speed sensor 11.
Is determined in accordance with the vehicle speed input from the vehicle and the turning angle of the steered wheels 6. That is, the operating force of the steering reaction force motor 4 is set so that the operating force of the steering wheel 2 increases as the steering angle of the steered wheels 6 increases, and is relatively large at high speeds and relatively small at low speeds. Is continuously variably controlled by feedback control. Thus, the steering wheel 2
A steering feeling as if the steering wheel 6 and the steering wheel 6 are directly connected to each other is obtained. On the other hand, the turning control unit 15 is provided with the steering angle sensor 3.
A target turning angle setting unit 19 that sets a target turning angle based on an operation angle signal including the operation direction of the steering wheel 2 from the vehicle and a vehicle speed signal from the vehicle speed sensor 11 and a signal from the steering angle sensor 3 are differentiated. Target steering angle setting unit 20 for setting a target correction steering angle based on the steering angular velocity signal obtained by
And a steering motor control signal output unit 21 for calculating a drive current of the steering motor 10 for making the output value of the steering angle sensor 12 (the actual steering angle of the steered wheels 6) coincide with the target value obtained by adding these. A steering motor drive circuit 22 controls the power actually supplied to the steering motor 10 according to the current command value. With the above configuration, the optimum turning angle of the steered wheels 6 is determined in consideration of the vehicle speed at that time with respect to the steering angle given to the steering wheel 2 by the driver. In this case, the basic target turning angle value is determined so as to match the target route that the driver has recognized that the driver can reach the vehicle after 1.2 seconds regardless of the vehicle speed. Then, a steering angle obtained by adding a target correction steering angle value based on the steering angular velocity as a differential element to the target steering angle value is given to the steered wheels 6.
The feedback control of the steering motor 10 is performed. In this manner, for example, when the vehicle is running at low speed, the steered wheels 6 are relatively steered relative to the amount of operation of the steering wheel 2, and the trouble of garage entry and steering operation on a curved road is eliminated. At high speed, the steered wheels 6 are steered relatively small with respect to the operation amount of the steering wheel 2. At the same time, the steering angle ratio continuously changes so that the yaw rate gain with respect to the operation amount of the steering wheel 2 becomes substantially constant regardless of the vehicle speed.
Driving stability is enhanced. In addition, when quick steering is performed, for example, during emergency avoidance, the turning angle of the steered wheels 6 is automatically corrected in accordance with the temporal change of the yaw rate to be generated to reach the target point. As a result, the steering stability and responsiveness are realized at a higher level. The present invention is also applicable to a steering device 25 in which the steering wheel 2 and the steered wheels 6 are mechanically connected as shown in FIG. In this case, the relationship between the rotation angle of the steering wheel 2 and the turning angle of the steered wheel 6 is continuously changed between the steering wheel 2 and the steering gear box 26 that provides the steered angle to the steered wheels 6. A variable steering angle ratio mechanism 27 (see Japanese Patent Application Laid-Open No. 5-105106) is provided. Also in this case, the signals from the steering angle sensor 3 and the vehicle speed sensor 11 are input to the control device 29 and the feedback control of the variable steering angle ratio motor 28 is performed, so that the turning angle of the steering wheel 2 and the turning angle of the steered wheels 6 are reduced. Can be controlled in the same manner as in the steer-by-wire steering device 1, and a similar operation can be obtained. In setting the target correction steering angle, not only the above-mentioned steering angular velocity but also a yaw rate, a lateral acceleration or the like may be used. If a sensor having a proportional relationship between the rotation angle and the torque is used, the steering angle, the steering angular velocity, and the steering torque can be obtained from one sensor. As described above in detail, according to the present invention, at a high speed, the differentiation operation of a person is reduced despite the weight of the differentiation operation being increased, and the burden on the driver is reduced. A great effect can be achieved in realizing stable running equivalent to that of a skilled person by reducing the amount.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the movement of a vehicle along a course. FIG. 2 is a schematic configuration diagram of a steer-by-wire steering device to which the present invention is applied. FIG. FIG. 4 is a schematic block diagram of a variable steering angle ratio steering device to which the present invention is applied. FIG. 5 is a schematic block diagram of a human control operation. FIG. 6 is a schematic diagram showing the movement of a vehicle along a course. [Description of References] 1 Steer-by-wire steering device 2 Steering wheel 3 Steering angle sensor 4 Steering reaction force adding motor 6 Steering wheel 10 Steering motor 13 Control device 15 Steering control unit 19 Target turning angle setting unit 20 Target correction steering angle setting unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B62D 119: 00 B62D 119: 00 F-term (Reference) 3D032 CC03 DA02 DA03 DA15 DA23 DC03 DD17 EB12 EC22 3D033 CA02 CA03 CA13 CA16 CA17 CA21

Claims (1)

Claims 1. A target steering angle ratio or a target wheel such that a vehicle reaches a position where a vehicle reaches a position irrespective of a vehicle speed by steering a steering wheel toward a position where the vehicle arrives after a predetermined time. A vehicle steering system that sets a steering angle and feedback-controls an actual steering angle ratio or a wheel steering angle to be the target steering angle ratio or a target wheel steering angle, wherein the target is determined by a steering angular velocity of the steering wheel. A vehicle steering system for adding and correcting a steering angle ratio or a target wheel turning angle.