JP3717352B2 - Vehicle steering system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle steering apparatus capable of controlling the attitude of a vehicle by driving a steering mechanism.
[0002]
[Prior art]
The mechanical connection between the steering wheel and the steering mechanism for steering the steering wheel is eliminated, and the steering wheel operation direction and operation amount are detected. Based on the detection result, the steering mechanism includes an actuator such as an electric motor. There has been proposed a vehicle steering device that applies a driving force from the vehicle (see, for example, Japanese Patent Laid-Open No. 9-142330).
[0003]
By adopting such a configuration, it is not necessary to mechanically connect the steering mechanism and the steering wheel, so that the steering wheel can be prevented from being pushed up at the time of collision, and the configuration of the steering mechanism is simplified and reduced in weight. be able to. In addition, the degree of freedom of the position where the steering wheel is disposed is increased, and further, it is possible to employ other operating means such as a lever or a pedal other than the steering wheel.
[0004]
In the vehicle steering apparatus configured as described above, the relationship between the operation of the steering wheel and the operation of the steering mechanism can be freely changed by electrical control, so that the driving performance of the vehicle can be dramatically improved. It is expected.
For example, the attitude of the vehicle can be controlled by obtaining the target yaw rate or the target lateral acceleration corresponding to the operation torque or the operation angle of the steering wheel, and controlling the operation of the steering mechanism based on the target yaw rate or the target lateral acceleration. The motion characteristics can be optimized.
[0005]
As another means for controlling the attitude of the vehicle, there is a method of individually controlling the braking pressures of the four wheels. That is, the yaw rate or the lateral acceleration of the vehicle can be controlled by the individual control of the braking pressures of the four wheels, thereby preventing the vehicle behavior from becoming unstable. In particular, on a low-friction road surface such as ice, posture control (brake posture control) based on braking pressure control is more effective than posture control (steering posture control) using a steering mechanism.
[0006]
[Problems to be solved by the invention]
By connecting an ECU (Electronic Control Unit) for controlling the steering mechanism and an ECU for controlling the braking pressure to exchange data, for example, the target yaw rate is shared by both ECUs, and the steering posture Control and brake attitude control may be used together.
In this case, while driving on a low-friction road surface, the brake attitude control works effectively, but even if the tire direction is changed, the vehicle yaw angle hardly changes, so the steering attitude control is substantially meaningless. . Therefore, the calculation of the steering posture control is performed wastefully while traveling on the low friction road surface.
[0007]
Moreover, when steering posture control is performed on a low friction road surface, the steering wheel may be directed in a direction completely different from the operation angle of the steering wheel. For this reason, there is no guarantee that the steering wheel is directed in the direction intended by the driver when the vehicle returns from a slipping state, such as by moving from a low friction road surface to a high friction road surface. There is .
[0008]
Accordingly, an object of the present invention is to provide a vehicle steering apparatus that can solve the above-described technical problems and can appropriately control a steering mechanism.
[0009]
Concrete object of the invention is to provide a vehicle steering apparatus capable of performing attitude control while well adapted to a low friction road surface.
[0010]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, the invention according to claim 1 provides a vehicle steering mechanism (2, 3) based on an output signal of an angle sensor (11) for detecting an operation angle (δh) of the operation means (1 ). A vehicle steering apparatus for driving the vehicle, wherein the steering mechanism is controlled based on a detected value of a behavior variable (Gy, γ) representing the behavior of the vehicle, thereby controlling the attitude of the vehicle (20, S3, S13) and steering effectiveness determination means for determining whether or not there is a significant influence on the vehicle behavior due to the driving of the steering mechanism based on whether or not a certain yaw angle change after driving the steering mechanism has occurred. (S1, S11) and an attitude for stopping the attitude control of the vehicle by the attitude control means when it is determined by the steering effectiveness determination means that there is no significant influence on the vehicle behavior by driving the steering mechanism Look including a control stop means (S2, S12), the steering angle when the posture control of the vehicle is stopped by the attitude control means by said attitude control cancel means, corresponding to the operation angle detected by the angle sensor A steering apparatus for a vehicle , wherein the steering mechanism is controlled so that (δ) is achieved .
[0011]
In addition, the alphanumeric characters in parentheses represent corresponding components in the embodiments described later. The same applies hereinafter.
In this case, it is preferable that there is no mechanical coupling between the steering mechanism and the operation means for steering, and the steering mechanism is electrically controlled in accordance with the operation of the operation means. .
According to the present invention, when the vehicle posture cannot be significantly changed by the steering by the steering mechanism, the vehicle posture control by the control of the steering mechanism is stopped. That is, in situations where the steering is not effective, such as a low-friction road surface, the posture control by the control of the steering mechanism is not performed, so there is no waste of control.
[0012]
Also, after stopping the attitude control, since so as to control the steering mechanism so as to achieve a steering angle corresponding to the operation of the operating means, for example, when leaving the high friction road surface from a low friction road surface Thus, when the vehicle returns from the slipping state, the vehicle can travel in the direction intended by the driver, and the vehicle posture can be prevented from being disturbed.
[0015]
Incidentally, the posture control hand stage by using an output of the behavior variable detection means for detecting a behavior variable representing the actual behavior of the vehicle (15, 16), it is preferable that controls the steering mechanism.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram for explaining a basic configuration of a vehicle steering apparatus according to an embodiment of the present invention. In this vehicle steering apparatus, the operation of the steering actuator 2 driven in accordance with the rotation operation of the steering wheel (operation means) 1 is converted into the steering motion of the front left and right wheels 4F (steering wheels) by the steering gear 3. Thus, steering is achieved without mechanically connecting the steering wheel 1 and the steering gear 3. In this case, a steering mechanism is constituted by the steering actuator 2, the steering gear 3, and the like.
[0017]
The steering actuator 2 can be constituted by an electric motor such as a known brushless motor. The steering gear 3 has a motion conversion mechanism (such as a ball screw mechanism) that converts the rotational motion of the output shaft of the steering actuator 2 into a linear motion in the axial direction (vehicle width direction) of the steering rod 7. The movement of the steering rod 7 is transmitted to the knuckle arm 9 via the tie rod 8 and causes the knuckle arm 9 to rotate. Thereby, steering of the wheel 4F supported by the knuckle arm 9 is achieved.
[0018]
The steering wheel 1 is connected to a rotary shaft 10 that is rotatably supported with respect to the vehicle body. The rotary shaft 10 is provided with a reaction force actuator 19 for applying a steering reaction force to the steering wheel 1. Specifically, the reaction force actuator 19 can be configured by an electric motor such as a brushless motor having an output shaft integrated with the rotary shaft 10.
An elastic member 30 made of a spiral spring or the like is coupled to the end of the rotating shaft 10 on the opposite side of the steering wheel 1 from the vehicle body. The elastic member 30 returns the steering wheel 1 to the straight steering position by the elastic force when the reaction force actuator 19 is not applying torque to the steering wheel 1.
[0019]
In order to detect an operation input value of the steering wheel 1, an angle sensor 11 for detecting an operation angle δh corresponding to the rotation angle of the rotary shaft 10 is provided. Further, the rotary shaft 10 is provided with a torque sensor 12 for detecting an operation torque T applied to the steering wheel 1.
On the other hand, as an output value sensor for detecting the output value of the steering actuator 2, a turning angle sensor 13 for detecting the turning angle δ of the wheel 4F is provided. The steered angle sensor 13 can be configured by a potentiometer or the like that detects the operation amount of the steering rod 7 by the steering actuator 2.
[0020]
The angle sensor 11, the torque sensor 12, and the turning angle sensor 13 are connected to a steering system control device 20 (posture control means, steering control means) including a computer (ECU: electronic control unit).
The control device 20 controls the steering actuator 2 and the reaction force actuator 19 via the drive circuits 22 and 23.
On the other hand, the steering system control device 20 communicates with the traveling system control device 60 for controlling braking of the vehicle via the line 50 to exchange data.
[0021]
The braking pressure corresponding to the depressing force of the brake pedal 51 is generated by the master cylinder 52. This braking pressure is amplified by the braking pressure control unit 53 and distributed to the brake devices 54 of the front wheel 4F and the rear wheel 4R. Thus, each brake device 54 applies a braking force to each wheel 4F, 4R. The braking pressure control unit 53 is controlled by a traveling system control device 60 constituted by a computer (ECU), whereby the braking pressures of the wheels 4F and 4R are individually controlled.
[0022]
In the traveling system control device 60, in addition to the steering system control device 20, a braking force sensor 61 that individually detects the braking force of each wheel 4F, 4R, and each rotational speed of each wheel 4F, 4R is detected individually. A wheel speed sensor 62 is connected. The traveling system control device 60 is further connected with a lateral acceleration sensor 15 for detecting the lateral acceleration Gy of the vehicle, a yaw rate sensor 16 for detecting the yaw rate γ of the vehicle, and a speed sensor 14 for detecting the vehicle speed V. ing. The detected data indicating the lateral acceleration Gy, the yaw rate γ, and the vehicle speed V is used in the traveling system control device 60 and also transmitted to the steering system control device 20 through the line 50. Yes.
[0023]
The traveling system control device 60 can amplify and distribute the braking pressure according to the rotational speed of each wheel 4F, 4R detected by the wheel speed sensor 62 and the feedback value from the braking force detection sensor 61. The brake pressure control unit 53 is controlled. As a result, the braking force of each wheel 4F, 4R can be individually controlled. Note that the braking pressure control unit 53 is configured to be able to generate a braking pressure by a built-in pump even when the brake pedal 51 is not operated.
[0024]
FIG. 2 is a block diagram for further explaining the configuration related to the attitude control of the vehicle. The steering system control device 20 gives data representing the detected values of the operation angle δh, the torque T, and the turning angle δ to the traveling system control device 60 via the line 50. In addition, the traveling system control device 60 gives data representing the detected values of the lateral acceleration Gy, the yaw rate γ, and the vehicle speed V to the steering system control device 20 via the line 50. Further, traveling controller 60 calculates the target yaw rate gamma ^* internally, providing data representing the target yaw rate gamma ^* the steering controller 20.
[0025]
The traveling system control device 60 determines a target yaw rate γ ^* based on each input data, individually controls the braking pressure of each wheel 4F, 4R via the braking pressure control unit 53, and thereby detects the detected yaw rate γ. Vehicle posture control (brake posture control) is performed so as to approach the target yaw rate γ ^* .
On the other hand, the steering system control device 20 obtains the target lateral acceleration Gy ^* based on the operation angle δh, takes in the target yaw rate γ ^* from the traveling system control device 60, and calculates the target turning angle δ ^* based on these. To do. Then, by controlling the steering actuator 2 so that the turning angle δ detected by the turning angle sensor 13 approaches the target turning angle δ ^* , vehicle attitude control (steering attitude control) is performed.
[0026]
That is, in this embodiment, the brake posture control and the steering posture control are used together for the vehicle posture control.
However, while traveling on a low-friction road such as on ice, the rudder cannot be operated, and even if the attitude control of the vehicle is controlled by the control of the steering actuator 2, there is almost no meaning. Only the posture control (brake posture control) by the braking control of the traveling system control device 60 is effective. In such a case, the posture control (steering posture control) by the steering system control device 20 is not only useless, but the traveling road surface is changed from a low friction road surface to a high friction road surface, and the vehicle is moved from a slipping state. When returning, it cannot be guaranteed that the steering wheel 4F is oriented in the direction intended by the driver. Therefore, there is a possibility that the posture of the vehicle is disturbed.
[0027]
Therefore, in this embodiment, an operation as shown in FIG. 3 is performed. That is, the steering system control device 20 determines whether or not a yaw angle change of a certain level or more has occurred after driving the steering actuator 2 (step S1). If there is no significant yaw angle change (NO in step S1), the steering posture control is stopped (step S2). If a significant yaw angle change is recognized (YES in step S1), the steering posture control is continued. (Step S3).
[0028]
The determination as to whether or not a certain yaw angle change has occurred can be substituted by, for example, determining whether or not the tire skid angle β is greater than a certain value.
When the brake posture control is performed only when slipping occurs, the same purpose can be achieved by the operation shown as a reference example in FIG. That is, instead of examining whether there is a significant yaw angle change, it is determined whether or not the brake attitude control is being performed (step S11). If the brake attitude control is being performed, the steering attitude control is stopped ( If the brake attitude control is not performed, the steering attitude control is performed (step S13).
[0029]
When the steering posture control is stopped (steps S2 and S12), the steering system control device 20 controls the steering actuator 2 so that the turning angle δ corresponding to the operation angle δh detected by the angle sensor 11 is achieved. To control. Therefore, when the vehicle moves from the low friction road surface to the high friction road surface and the vehicle returns from the slipping state, the vehicle advances in the direction intended by the driver. Therefore, the vehicle posture is not disturbed due to the steering posture control.
[0030]
Next, other features of this embodiment will be described with reference to FIGS.
The steering system control device 20 and the traveling system control device 60 exchange data via a communication line represented by a line 50. In order to synchronize the steering posture control with the brake posture control, the steering system control device 20 generates a reception interrupt when the data from the traveling system control device 60 is received via the line 50, and performs posture control calculation. Do.
[0031]
However, if an abnormality occurs in any of the components related to the abnormality of the line 50 or the brake posture control (the traveling system control device 60, the sensors 14 to 16, etc.), the data sent from the traveling system control device 60 Based attitude control is meaningless.
Therefore, in this embodiment, when an abnormality occurs in the data from the traveling system control device 60, the steering system control device 20 shifts to the internal synchronization method that defines the control cycle by the internal timer 70 (internal synchronization means). And switching.
[0032]
More specifically, as shown in FIG. 5, when data is received, it is determined whether or not the data is abnormal (step S21). Whether or not there is an abnormality in the data is detected, for example, by examining the coincidence / non-coincidence between the sum total of all data received during one control period and the sum value data sent from the traveling system control device 60 can do.
If there is no abnormality in the data (NO in step S21), a reception interrupt is generated and attitude control calculation is performed in the control cycle (step S22). On the other hand, if there is an abnormality in the received data (YES in step S21), the reception interrupt is not performed, and the drive control of the steering actuator 2 is performed by an internal synchronization method in which a control cycle is determined by the internal timer 70 (step S23). In this case, since the detection data of the sensors 14 to 16 are not input, the attitude control is not performed, and the steering actuator 2 is normally controlled so that the turning angle δ corresponding to the operation angle δh of the steering wheel 1 is achieved. The steering control is performed.
[0033]
Thus, according to this embodiment, when any abnormality occurs on the traveling system control device 60 side, the steering system control device 20 detects such an abnormality based on the received data, and receives a reception interrupt. Inhibit and switch to the internal synchronization method to perform independent control calculations. In this way, it is possible to provide a system with countermeasures against abnormality.
Although one embodiment of the present invention has been described above, the present invention can be implemented in other forms. For example, in the above-described embodiment, the detection signals of the speed sensor 14, the lateral acceleration sensor 15, and the yaw rate sensor 16 are input to the traveling system control device 60, and data representing the detected values is transmitted from the traveling system control device 60 to the steering system. Although it is configured to be input to the control device 20, as indicated by a two-dot chain line in FIG. 2, the output signals of the sensors 14, 15 and 16 are output from the traveling system control device 60 and the steering system control device 20. It may be input to both. In this case, since the steering system control device 20 can obtain information necessary for posture control without depending on the travel system control device 60, an abnormality is recognized in the data received from the travel system control device 60. After this, the steering posture control can be continued. When the data from the traveling system control device 60 is normal, it is necessary to share at least the target yaw rate γ ^* between the traveling system control device 60 and the steering system control device 20. Data communication is required.
[0034]
In the above-described embodiment, the case where two wheels of a four-wheel vehicle can be steered as a steering wheel has been described. However, the present invention is applied to a four-wheel steering system in which all four wheels are steered. Also good.
In the above-described embodiment, the example in which the steering wheel 1 is used as the operation unit has been described. However, other operation units such as a lever and a pedal may be used.
[0035]
In addition to these, various design changes can be made within the scope of the matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram for explaining a basic configuration of a vehicle steering apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram for explaining a configuration for posture control.
FIG. 3 is a flowchart for explaining a process for invalidating steering posture control;
FIG. 4 is a flowchart for explaining another process for invalidating steering attitude control.
FIG. 5 is a flowchart for explaining switching of the synchronization method of the steering system control device;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering actuator 11 Angle sensor 12 Torque sensor 13 Steering angle sensor 14 Speed sensor 15 Lateral acceleration sensor 16 Yaw rate sensor 20 Steering system control apparatus 50 Line (communication line)
60 Traveling system controller 70 Internal timer

Claims (1)

A vehicle steering device that drives a steering mechanism of a vehicle based on an output signal of an angle sensor that detects an operation angle of an operation means ,
Attitude control means for controlling the attitude of the vehicle by controlling the steering mechanism based on a detected value of a behavior variable representing the behavior of the vehicle;
Steering effectiveness determination means for determining the presence or absence of a significant influence on vehicle behavior due to driving of the steering mechanism, based on whether or not a certain yaw angle change has occurred after driving the steering mechanism;
This steering validity determination unit, when it is determined that there is no significant influence on the vehicle behavior due to the driving of the steering mechanism, see containing a posture control stop means to stop the posture control of the vehicle by the attitude control means ,
Controlling the steering mechanism so that a turning angle corresponding to an operation angle detected by the angle sensor is achieved when the posture control of the vehicle by the posture control unit is stopped by the posture control stopping unit; A vehicle steering apparatus characterized by the above.

Images