Vehicle steering control apparatus and method

Abstract

A vehicle steering control apparatus has a steering wheel, a steering mechanism mechanically separate from the steering wheel for steering the left and right front wheels and a reaction force motor for imparting an operation reaction force against the steering wheel. A steering motor is provided to impart a turning force to the steering mechanism, while a clutch is provided to mechanically connect and disconnect the steering wheel to and from the steering mechanism. A drive torque detector is provided to detect a drive torque imparted to the steering reaction force actuator. A torque sensor is provided to detect an operating torque imparted to the steering wheel. A clutch connection determiner determines that the clutch is in a connected state when a drive torque direction detected by the drive torque detector and an operating torque direction detected by the operating torque detector are different.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the attached drawings which form a part of this original disclosure:

FIG. 1 is schematic view of a steer-by-wire system exemplifying a vehicle steering control apparatus in accordance with a first embodiment of the present invention;

FIG. 2 is a gear ratio versus vehicle speed characteristic diagram illustrating an example of the variable gear ratio control executed by the steer-by-wire control in the first embodiment of the present invention;

FIG. 3 is control block diagram illustrating a robust model matching method that can be used as the steering control portion of the steer-by-wire control of the first embodiment of the present invention;

FIG. 4 is a flowchart of clutch connection determination processing executed by the operation reaction force controller and the steering controller of the first embodiment of the present invention;

FIG. 5 is a characteristic plot illustrating an example of the relationships among the steering wheel operating angle, the actual (detected) steering angle, and the command steering angle when the clutch is connected;

FIG. 6 is a characteristic plot of the reaction force motor drive torque and the torque sensor value and a schematic view illustrating how the torques and rotational directions change after the clutch is connected in a situation in which the clutch is connected while the steering wheel is being operated in one direction;

FIG. 7 provides a characteristic plot of the reaction force motor drive torque and the torque sensor value and a schematic view illustrating how the torques and rotational directions change after the clutch is connected in a situation in which the clutch is connected while the direction in which the steering wheel is operated is being reversed;

FIG. 8 is a characteristic plot of the reaction force motor drive torque and the torque sensor value and a schematic view illustrating how the torques and rotational directions change after the clutch is connected in a situation in which the clutch is connected while the steering wheel is being operated in one direction and, afterwards, the steering wheel is released by the driver;

FIG. 9 is a flowchart of the clutch connection release processing executed by the operation reaction force controller and the steering controller of a first variation of the first embodiment of the present invention;

FIG. 10 is a flowchart of the clutch connection release processing executed by the operation reaction force controller and the steering controller of the second variation of first embodiment of the present invention;

FIG. 11 is a cross sectional view of the clutch in a vehicle steering control apparatus in accordance with a second embodiment of the present invention;

FIG. 12 is the mechanical clutch section of the clutch in a vehicle steering control apparatus in accordance with a second embodiment;

FIG. 13 illustrates how the clutch can become connected when it is supposed to be in a released state;

FIG. 14 is a flowchart of clutch connection determination processing executed by the operation reaction force controller and the steering controller of a first variation of the second embodiment of the present invention;

FIG. 15 is a flowchart of clutch connection determination processing executed by the operation reaction force controller and the steering controller of a second variation of the second embodiment of the present invention; and

FIG. 16 is a flowchart of clutch connection determination processing executed by the operation reaction force controller and the steering controller of a third variation of the second embodiment of the present invention.

Claims

1. A vehicle steering control apparatus comprising: a driver operating unit configured to be operated by a driver;a steering unit arranged to be mechanically separated from the driver operating unit and configured to turn at least one steered wheel;a steering reaction force actuator operable to apply an operating reaction force to the driver operating unit;a steering actuator configured to apply a turning force to the steering unit;a clutch operable to mechanically connect and disconnect the driver operating unit and the steering unit to and from each other;a drive torque detector operable to detect a drive torque imparted to the steering reaction force actuator;an operating torque detector operable to detect an operating torque applied to the driver operating unit; anda clutch connection determiner configured to determine that the clutch is in a connected state when a drive torque direction indicated by a drive torque detection value detected by the drive torque detector and an operating torque direction indicated by an operating torque detection value detected by the operating torque detector are different.

2. The vehicle steering control apparatus as recited in claim 1, further comprising a difference calculator configured to calculate a difference between the drive torque imparted to the steering reaction force actuator and the operating torque detection value detected by the operating torque detector; andthe clutch connection determiner being further configured to determine that the clutch is in a connected state when an absolute value of the difference calculated by the difference calculator is equal to or larger than a threshold value.

3. The vehicle steering control apparatus as recited in claim 2, wherein the clutch connection determiner is further configured to set a first threshold value as the threshold value when the driver operating unit is operated in a direction so as to turn wider or to return toward a non-turning position, and a second threshold value as the threshold value when the driver operating unit is operated such that the operating torque direction is changed, with the second threshold value being larger than the first threshold value.

4. The vehicle steering control apparatus as recited in claim 2 or 3, wherein the clutch connection determiner is further configured to raise a clutch connection diagnostic flag and set a command steering angle to a detected steering angle upon determining that the clutch is in the connected state.

5. The vehicle steering control apparatus as recited in claim 4, wherein the clutch connection determiner is further configured to determine that the clutch is in the connected state and raise a clutch connection confirmation flag when the clutch connection diagnostic flag has been in a raised state continuously for at least a prescribed amount of time.

6. The vehicle steering control apparatus recited in claim 1, further comprising a connection determination execution condition detector configured to detect a prescribed condition in which the clutch connection determiner determine if the clutch is in the connected state; andthe clutch connection determiner is further configured to execute determination of whether the clutch is the connected state when the prescribed condition has been detected.

7. The vehicle steering control apparatus as recited in claim 6, wherein the connection determination execution condition detector is further configured to detect that the prescribed condition exists when an operating speed of the driver operating unit is equal to or larger than a first rate threshold value.

8. The vehicle steering control apparatus as recited in claim 6, wherein the connection determination execution condition detector is further configured to detect that the prescribed condition exists when a change rate of the drive torque imparted to the steering reaction force actuator is equal to or larger than a second rate threshold value.

9. The vehicle steering control apparatus as recited in claim 6, wherein the connection determination execution condition detector is further configured to detect that the prescribed condition exists when a change rate of the operating torque detection value detected by the operating torque detector is equal to or larger than a third rate threshold value.

10. The vehicle steering control apparatus recited in claim 1, further comprising a clutch connection releasing device configured to exert a torque in an opposite direction of a connection direction of the clutch using the steering actuator or the steering reaction force actuator when the clutch connection determiner detects that the clutch is in the connected state.

11. The vehicle steering control apparatus as recited in claim 10, wherein the clutch connection releasing device is further configured to drive the steering actuator using a detected steering angle existing at a point in time when the clutch connection determiner detected the connected state of the clutch as a command steering angle.

12. The vehicle steering control apparatus as recited in claim 10, wherein the clutch connection releasing device is further configured to exert a torque in an opposite direction of a connection direction of the clutch using the steering reaction force actuator when a variable gear ratio control is being executed such that a gear ratio becomes equal to or smaller than a clutch connection gear ratio at a point in time when the clutch connection determiner detected the connected state of the clutch.

13. The vehicle steering control apparatus recited in claim 10, wherein the clutch connection releasing device is further configured to determine that the clutch has been disconnected when the absolute value of the difference between the drive torque imparted to the steering reaction force actuator and the operating torque detection value detected by the operating torque detector is equal to or below a third threshold value and the direction of the drive torque imparted to the steering reaction force actuator and the operating torque direction of the operating torque detection value detected by the operating torque detector are equal.

14. A vehicle steering control apparatus comprising: steering input means for receiving a steering operation from a driver;turning means for turning at least one steered wheel;steering reaction force means for applying an operating reaction force to the steering input means;torque applying means for applying a wheel turning torque to the turning means in response to an input torque from the steering input means;connection means for mechanically connecting and disconnecting the steering input means to the turning means to and from each other to mechanically transmit an input torque from the steering input means to the turning means when the steering input means and the turning means are mechanically connected by the connection means;drive torque detecting means for detecting a drive torque imparted to the steering reaction force means;operating torque detecting means for detecting an operating torque applied to the steering input means; andconnection determining means for determining that the connection means is in a connection state of when a drive torque direction indicated by a drive torque detection value detected by the drive torque detecting means and an operating torque direction indicated by an operating torque detection value detected by the operating torque detecting means are different.

15. A vehicle steering control method comprising: providing a driver operating unit configured to be operated by a driver to input an operating torque to a steering unit that is configured to turn at least one steered wheel, with a steering actuator configured to apply a turning force to the steering unit based on the operating torque and a clutch selectively operable to mechanically connect and disconnect the driver operating unit and the steering unit to and from each other to selectively transmit the operating torque to the steering unit;providing a steering reaction force actuator operable to apply an operating reaction force to the driver operating unit;detecting a direction of a drive torque imparted to the steering reaction force actuator coupled to a driver operating unit;detecting an operating torque direction of the operating torque applied by the driver to the driver operating unit; anddetermining that the clutch is in a connected state when the direction of the drive torque imparted to the steering reaction force actuator and the operating torque direction of the operating torque are different.