JP2004224159A - Steering control device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering control device for a vehicle that can prevent vibration of a steering operation means near a limit on the range of movement of a steering wheel and that allows the driver to recognize that the steering angle has reached the limit of the range of the movement easily. <P>SOLUTION: In this steering control device for a vehicle including a steering mechanism that does not join a steering control system to a wheel steering system mechanically, steering angle control means, and steering reactive force control means, there is provided an angle sensor 2 for detecting a steering angle, and the steering reactive force control means includes a controlling component for steering control reactive force, which increases the steering reactive force in accordance with an increase in the steering angle with the slope of a line or a curve until immediately before the steering angel reaches the limit angle from a predetermined steering angle and then increases the steering reactive force to the limit reactive force rapidly when the steering angle reaches the limit angle. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the technical field of steering reaction force control of a vehicle steering control device using a steer-by-wire system that does not mechanically connect a steering system and a wheel turning system.
[0002]
[Prior art]
In a steer-by-wire system in which the steering system and the wheel steering system are not mechanically connected, the steering wheel can be steered beyond the movable range of the steered wheels unless mechanical restrictions are provided.
[0003]
On the other hand, as a method of limiting the steering wheel so as not to be steered beyond the movable range of the steered wheels without increasing the number of parts, that is, without adding a mechanical limitation, a conventional vehicle steering control device includes: When the deviation between the target turning angle and the actual turning angle obtained by steering the steering wheel is equal to or larger than a predetermined value (for example, when the steering wheel is steered beyond the movable range of the steered wheel), the steering reaction force actuator is used. , A predetermined operation inhibition reaction force is generated (for example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-2002-87308 (page 1, FIG. 2).
[0005]
[Problems to be solved by the invention]
However, in the conventional vehicle steering control device, a large steering reaction force is generated at a stretch when the steering wheel is steered beyond a certain steering angle near the limit of the movable range of the steered wheels. Since the steering reaction force was generated at the time of control, when the driver applied steering torque in the increasing direction to the steering wheel, a certain steering angle near the movable range limit of the steered wheels was applied to the steering wheel. As a boundary, a torque is applied in a turning back direction by a steering reaction force at an angle larger than the angle, and in a turning direction more at an angle smaller than the angle. Therefore, there is a problem that the steering wheel generates vibration in which the direction of the torque alternates near the limit of the movable range of the steered wheels.
[0006]
The present invention has been made in view of the above problem, and it is possible to suppress the vibration of the steering operation means near the limit of the movable range of the steered wheels and to make it easy for the driver to determine that the steering angle is at the limit of the movable range. It is an object of the present invention to provide a vehicle steering control device that can be recognized by a vehicle.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, in the present invention,
A steering mechanism that does not mechanically connect the steering system and the wheel steering system;
Turning angle control means for controlling the turning angle of the wheels according to the steering angle,
Steering reaction force control means for controlling a steering reaction force acting in a direction opposite to the steering direction;
In a vehicle steering control device provided with
Providing a steering angle detection means for detecting a steering angle,
The steering reaction force control means, according to an increase in the steering angle, until the steering angle reaches a limit angle that is a limit steering angle corresponding to a limit angle of the turning angle of the wheel from a predetermined steering angle. Includes a steering limit reaction force control unit that increases the steering reaction force with a straight or curved slope and, when the steering angle reaches the limit angle, sharply increases the steering reaction force to the limit reaction force that is the limit of the steering reaction force. It is characterized by the following.
[0008]
【The invention's effect】
Therefore, in the vehicle steering control device of the present invention, in the steering restriction reaction force control unit of the steering reaction force control means, until the steering angle reaches the limit angle from the predetermined steering angle until the steering angle reaches the limit angle. The steering reaction force is increased linearly or curvedly according to the increase, and when the steering angle reaches the limit angle, the steering reaction force is sharply increased to the limit reaction force. Thus, the vibration of the steering operation means can be suppressed, and the driver can easily recognize that the steering angle is at the limit of the movable range.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment for realizing a vehicle steering control device of the present invention will be described based on an example illustrated in the drawings.
[0010]
(First embodiment)
First, the configuration will be described.
FIG. 1 is an overall system diagram showing a vehicle steering control device according to a first embodiment. In FIG. 1, 1 is a steering wheel, 2 is a steering angle sensor (steering steering angle detecting means) for detecting a steering angle, 3 is a reaction force actuator for generating a steering reaction force on the steering wheel 1, and 4 is a reaction force actuator 3. The drive motor 5 is a drive circuit for driving the drive motor 4 of the reaction force actuator 3, and these components constitute a steering system operated by the driver.
[0011]
In FIG. 1, reference numeral 6 denotes a drive circuit for driving a drive motor 7 of a steering actuator 8 that steers the steered wheels 11, 7 denotes a drive motor of the steering actuator 8 that steers the steered wheels 11, and 8 denotes a steered wheel 11. The turning actuator 9 for turning is an angle sensor for detecting the turning angle of the turning actuator 8, and a wheel turning system for turning the steered wheels 11 by the turning actuator 8 is configured by these components.
[0012]
That is, the steering system and the wheel steering system employ a steering mechanism that is not mechanically connected.
[0013]
In FIG. 1, reference numeral 10 denotes a steering control device that calculates a torque of a steering reaction force generated in the steering wheel 1 and calculates an angle of a steering actuator 8 that steers the steered wheels 11.
[0014]
The steering control device 10 detects a steering amount of the driver with respect to the steering wheel 1 by a steering angle sensor 2 and turns the steering wheel 11 so that the turning angle of the steered wheels 11 becomes a target turning angle corresponding to the detected steering angle. The control amount calculation of the rudder actuator 8 is performed. The control amount calculation result is output to the drive circuit 6 as a voltage value according to the motor drive torque, for example, and the drive circuit 6 drives the drive motor 7 according to the input voltage value. Further, when the drive motor 7 is driven, the steering actuator 8 steers the steered wheels 11, and the steered angle is detected by the angle sensor 9 and input to the steering control device 10. The steering control device 10 drives the drive motor 7 by feedback control such that the deviation between the target steering angle calculated previously and the actual steering angle detected by the angle sensor 9 is eliminated (steering angle control means).
[0015]
On the other hand, a steering reaction force to be applied to the steering wheel 1 is calculated by the steering control device 10 in accordance with the operation state of the steering actuator 8, or the steering angle of the steering wheel 1, the speed of the vehicle, etc. 5 is output as a voltage value corresponding to the motor torque, for example. The drive circuit 5 drives the drive motor 4 according to the input voltage value, and generates a steering reaction force on the steering wheel 1 via the reaction force actuator 3 (steering reaction force control means).
[0016]
Next, the operation will be described.
[0017]
[Steering reaction force control processing]
FIG. 2 is a flowchart showing the flow of the steering reaction force control process executed by the steering control device 10, and each step will be described below.
[0018]
In step S1, it is determined whether or not the steering angle detected by the steering angle sensor 2 exceeds the limited reaction force start angle. If Yes, the process proceeds to step S2, and if No, the process proceeds to step S7.
Here, "restricted reaction force" refers to the steering reaction force immediately before reaching the limit angle lower than the limit reaction force, and when the value of the limited reaction force is determined in advance, the slope of a straight line from the normal reaction force to the limited reaction force. The "restricted reaction force start angle" is determined by the steering reaction force increasing characteristic that increases with the above.
[0019]
In step S2, it is determined whether or not the steering angle detected by the steering angle sensor 2 is equal to or larger than the limit angle. If Yes, the process proceeds to step S6, and if No, the process proceeds to step S3.
Here, the "limit angle" refers to the limit steering angle corresponding to the limit angle of the turning angle of the wheel, and the "limit reaction force" refers to the limit of the steering reaction force at the limit angle.
[0020]
In step S3, it is determined whether or not the rotation of the steering wheel 1 is in the direction of turning back from the limit angle. If Yes, the process proceeds to step S5, and if No, the process proceeds to step S4.
[0021]
In step S4, if it is determined in step S3 that the steering operation is in the turning-up direction, the output reaction force based on the following equation (1), that is,
Output reaction force = normal reaction force + {(steering angle−restriction reaction force start angle) / (limit angle−restriction reaction force start angle)} × (restriction reaction force−normal reaction force). . . ▲ 1 ▼
Is output to the drive circuit 5.
[0022]
In step S5, when it is determined in step S3 that the steering operation is in the direction of returning from the limit angle, the output reaction force based on the following equation (2), that is,
Output reaction force = Normal reaction force + {(steering angle-Limit reaction start angle) / (Limit angle-Limit reaction start angle)} × (Limit reaction-Normal reaction force). . . ▲ 2 ▼
Is output to the drive circuit 5.
[0023]
In step S6, when it is determined in step S2 that the steering angle is equal to or larger than the limit angle, a command for obtaining a limit reaction force is output to the drive circuit 5.
[0024]
In step S7, if it is determined in step S1 that the steering angle is equal to or smaller than the limited reaction force start angle, a command to obtain the steering reaction force in the normal control is output to the drive circuit 5.
[0025]
[Steering reaction force control action]
When the steering angle is equal to or smaller than the limited reaction force start angle, the flow proceeds from step S1 to step S7 in the flowchart of FIG. 2, and in step S7, a command for obtaining the steering reaction force in the normal control is output to the drive circuit 5. You.
[0026]
If the steering angle exceeds the limited reaction force start angle due to the turning operation to the steering wheel 1, the flow proceeds to step S1 → step S2 → step S3 → step S4 in the flowchart of FIG. A command to obtain an output reaction force based on the equation (1) is output to the drive circuit 5.
[0027]
Further, when the steering angle reaches the limit angle by performing an additional turning operation on the steering wheel 1, the flow proceeds to step S1 → step S2 → step S6 in the flowchart of FIG. A command to obtain a force is output to the drive circuit 5.
[0028]
Thereafter, when the rotation of the steering wheel 1 is turned back from the limit angle, the flow proceeds to step S1 → step S2 → step S3 → step S5 in the flowchart of FIG. 2, and in step S5, the above equation (2) is obtained. A command for obtaining an output reaction force based on the above is output to the drive circuit 5.
[0029]
When the steering angle becomes equal to or less than the limited reaction force start angle due to the turning back of the steering wheel 1, the flow proceeds from step S1 to step S7 in the flowchart of FIG. 2, and in step S7, the steering reaction force in the normal control is reduced. The command to be obtained is output to the drive circuit 5.
[0030]
[Steering limit reaction force control action]
The conventional vehicle steering control device generates a large steering reaction force at a stroke when the steering wheel is steered beyond the limit angle as shown in FIG. 3 near the limit of the movable range of the steered wheels. Because it was configured to generate a steering reaction force during normal control, although it was only necessary to stop the steering wheel from rotating further at the limit angle of the movable range of the steered wheels, suddenly at the limit angle or more The steering wheel is returned in the turning direction because a large reaction force is generated. When the driver is applying a steering torque in the turning direction to the steering wheel, the steering wheel is steered at a steering angle above a certain steering angle near the limit of the movable range of the steered wheels as shown in FIG. Due to the reaction force, torques in opposite directions are applied alternately in the direction of turning back and, if the angle is smaller than the angle, in the direction of increasing turning. Therefore, the steering wheel generates vibration near the limit of the movable range of the steered wheels.
[0031]
On the other hand, in the vehicle steering control device of the first embodiment, if it is determined in step S3 that the steering wheel 1 is being steered from the neutral point in the turning direction, the process proceeds to step S4, and as shown in FIG. Then, a steering reaction force obtained from the inclination connecting the reaction force and the limited reaction force during normal control and the steering angle at that time is output (the above formula (1)). Therefore, when the steering wheel 1 is turned further, the reaction torque gradually increases from the limited reaction force start angle in accordance with the inclination, and the rotational speed of the steering wheel 1 being steered is suppressed. As a result, the rotational speed of the steering wheel 1 being steered is not suppressed until the limit angle is reached, and when the limit angle is reached, the maximum reaction force is applied at once, and a large torque is generated in the return direction generated by the reaction force actuator. Vibration of the steering wheel 1 can be suppressed.
[0032]
When the steering wheel 1 is turned further and the steering angle of the steering wheel 1 becomes equal to or larger than the limit angle, the process proceeds from step S2 to step S6, and a limit reaction force is generated as shown in FIG. Therefore, the driver can feel the rising change of the steering reaction force from the limited reaction force to the limit reaction force at the time of further turning operation via the steering wheel 1, and as a result, the steering angle is at the movable range limit. Can be easily recognized.
[0033]
Next, when the steering wheel 1 is rotated in the return direction this time by the maximum reaction force, if the steering angle is smaller than the limit opening and larger than the limit reaction force start angle, the process proceeds from step S3 to step S5. As shown in FIG. 5, a steering reaction force obtained from the inclination connecting the limit reaction force and the reaction force in the normal control and the steering angle at that time is output (the above equation (2)).
[0034]
For example, as shown in FIG. 4, when the same steering reaction force characteristic is given at the time of further turning and at the time of turning back, when the steering wheel is slightly turned back from the limit angle, the steering reaction force decreases from the limit reaction force to the limit reaction force. As a result, the steering reaction force greatly changes, and the vibration of the steering wheel 1 cannot be reliably suppressed.
[0035]
On the other hand, as shown in FIG. 5, by providing a hysteresis between the steering reaction force at the time of turning further toward the limit angle and the steering reaction force at the time of turning back from the limit angle, even when the vehicle is turned back from the limit angle. The change in the steering reaction force is small, and the vibration of the steering wheel 1 can be eliminated.
[0036]
Further, by gradually increasing the steering reaction force at the time of further turning, the rotation speed of the steering wheel 1 is suppressed, and the return amount of the steering wheel 1 due to the maximum reaction force can be reduced, so that the hysteresis width can be reduced. If the hysteresis width is large, the driver strongly recognizes that the hysteresis exists near the limit angle, giving a sense of incompatibility with the conventional mechanically connected steering system. Is good.
[0037]
Next, effects will be described.
In the vehicle steering control device according to the first embodiment, the following effects can be obtained.
[0038]
(1) A steering mechanism that does not mechanically connect a steering system and a wheel steering system, a steering angle control unit that controls a steering angle of a wheel according to a steering angle, a steering direction, A steering reaction force control means for controlling a steering reaction force acting in the opposite direction, a steering reaction control apparatus for a vehicle, comprising: an angle sensor 2 for detecting a steering steering angle; Until the steering angle reaches the limit angle from the predetermined steering angle, the steering reaction force is increased in a straight line or a curve in accordance with the increase in the steering angle, and when the steering angle reaches the limit angle, the steering reaction force is increased. The steering wheel 1 near the limit of the movable range of the steered wheels 11 due to the provision of a steering limit reaction force control unit that rapidly increases the steering wheel 1 to the limit reaction force. And the driver can easily recognize that the steering angle is at the limit of the movable range.
[0039]
(2) The steering limiting reaction force control unit includes a hysteresis for a steering reaction force increasing characteristic when the steering angle increases to the limit angle and a steering reaction force decreasing characteristic when the steering angle decreases from the limit angle. Therefore, even when the steering wheel 1 is returned from the limit angle, the change in the steering reaction force is suppressed to a small value, and the vibration of the steering wheel 1 can be eliminated.
[0040]
(3) The steering limiting reaction force control unit includes: a steering reaction force increasing characteristic in which the steering reaction angle increases from a normal reaction force to a limited reaction force with a linear inclination with respect to an increase in a steering angle from the limited reaction force start angle to the limit angle; The steering limit reaction force is controlled by a steering reaction force reduction characteristic that decreases with a straight line slope from the limit reaction force to the normal reaction force when the steering angle decreases from the limit angle to the limit reaction force start angle. In addition, the hysteresis width in the limit range of the movable range can be reduced, and as a result, the driver's uncomfortable feeling with respect to the steering system having the conventional mechanical connection configuration can be reduced.
[0041]
As described above, the vehicle steering control device according to the present invention has been described based on the first embodiment. However, the specific configuration is not limited to the first embodiment, but is described in each of the claims. Changes and additions to the design are permitted without departing from the spirit of the invention.
[0042]
For example, in the first embodiment, the steering restriction reaction force control unit uses the steering reaction force increasing characteristic that increases with the inclination of the straight line and the steering reaction force decreasing characteristic that decreases with the inclination of the straight line. A steering reaction force increasing characteristic that increases with the inclination and a steering reaction force decreasing characteristic that decreases with the inclination of the curve may be used.
[Brief description of the drawings]
FIG. 1 is an overall system diagram showing a vehicle steering control device according to a first embodiment.
FIG. 2 is a flowchart illustrating a flow of a steering reaction force control process executed by a steering control device in the first embodiment.
FIG. 3 is a diagram showing a reaction torque characteristic in a conventional vehicle steering control device.
FIG. 4 is a diagram showing a reaction torque characteristic in a vehicle steering control device of a comparative example in which hysteresis is not provided at the time of further turning and turning back.
FIG. 5 is a diagram showing a reaction torque characteristic in the vehicle steering control device of the first embodiment.
FIG. 6 is an explanatory diagram of vibration of a steering wheel in a conventional vehicle steering control device.
[Explanation of symbols]
1 steering wheel 2 steering angle sensor (steering steering angle detecting means)
3 Reaction Force Actuator 4 Drive Motor 5 Drive Circuit 6 Drive Circuit 7 Drive Motor 8 Steering Actuator 9 Angle Sensor 10 Steering Controller 11 Steered Wheel

Claims (3)

A steering mechanism that does not mechanically connect the steering system and the wheel steering system;
Turning angle control means for controlling the turning angle of the wheels according to the steering angle,
Steering reaction force control means for controlling a steering reaction force acting in a direction opposite to the steering direction;
In a vehicle steering control device provided with
Providing a steering angle detection means for detecting a steering angle,
The steering reaction force control means, according to an increase in the steering angle, until the steering angle reaches a limit angle that is a limit steering angle corresponding to a limit angle of the turning angle of the wheel from a predetermined steering angle. Includes a steering limit reaction force control unit that increases the steering reaction force with a straight or curved slope and, when the steering angle reaches the limit angle, sharply increases the steering reaction force to the limit reaction force that is the limit of the steering reaction force. A vehicle steering control device characterized by the above-mentioned. The vehicle steering control device according to claim 1,
The steering restriction reaction force control unit has hysteresis in a steering reaction force increasing characteristic when the steering angle increases to the limit angle and a steering reaction force decreasing characteristic when the steering angle decreases from the limit angle. A steering control device for a vehicle. In the vehicle steering control device according to claim 1 or 2,
The steering limiting reaction force control unit, when the steering reaction force that is lower than the limit reaction force and immediately before reaching the limit angle is referred to as a limiting reaction force, when the steering reaction angle increases from the limiting reaction force start angle to the limit angle, the normal reaction force From the limit reaction force to the normal reaction force in response to a decrease in the steering angle from the limit angle to the limit reaction force start angle. A steering control device for a vehicle, wherein a steering restriction reaction force is controlled by a steering reaction force reduction characteristic.

Images