Controlling apparatus of steering angle of rear wheels of four-wheel steering vehicle

• US 5,502,639 A
• Filed: 02/22/1995
• Issued: 03/26/1996
• Est. Priority Date: 08/10/1990
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Fukunaga, Takashi, Segawa, Akiyoshi
• Primary Examiner(s): Chin, Gary
• Application Number:
  US08/392,626
• Time in Patent Office: 398 Days
• Field of Search: 364/424.05, 280/91, 180/65.1, 180/65.3, 180/79.1, 180/140-143
• US Class Current: 701/41
• CPC Class Codes: B62D 7/159 characterised by computing methods or stabilisation processes or systems, e.g. responding to yaw rate, lateral wind, load, road condition

Abstract

A steering angle of rear wheels of a four-wheel steering vehicle is controlled so that a quick response of an electric motor mounted in the rear wheels is achieved only when it is necessary, thereby avoiding wasteful consumption of power. In addition, a yaw rate feedback system is kept stable. When unstable vibration of the electric motor is detected, a gain to the yaw rate is adjusted.

Claims

1. A controlling apparatus for controlling a steering angle of rear wheels of a four-wheel steering vehicle and comprising a sensor for detecting and outputting a sensor signal indicative of at least one of a current steering wheel angle, a current speed and a current yaw rate of the vehicle, wherein the steering angle of the rear wheels is established according to an operating position of an electric motor which drives the rear wheels via a reduction gear, said controlling apparatus further comprising:

a position detector for detecting and outputting a detection signal indicative of a current operating position of the electric motor;

an operating unit for (a) receiving the sensor signal from said sensor and the detection signal from said position detector, (b) calculating a desired operating position of the electric motor from the at least one of the current steering wheel angle, the current speed and the current yaw rate of the vehicle indicated by the sensor signal, (c) calculating a current command value indicative of a difference between the desired operating position of the electric motor and the current operating position of the electric motor indicated by the detection signal, and (d) outputting the current command value to a motor driver of the electric motor;

wherein said operating unit includes means for judging that the electric motor is vibrating when the difference between the desired operating position and the current operating position of the electric motor repeatedly fluctuates between positive and negative values at least a predetermined number of times within a preset time interval and an absolute peak value of the difference is at least a preset value during the preset time interval.

2. A controlling apparatus as claimed in claim 1, wherein said operating unit includes means for outputting a zero command value as the current command value to the motor driver of the electric motor when the electric motor is judged to be vibrating, wherein the driver of the electric motor is responsive to the zero command value to maintain the current operating position of the electric motor.

3. A controlling apparatus for controlling a steering angle of rear wheels of a four-wheel steering vehicle, and comprising a steering wheel angle sensor for detecting and outputting a steering wheel angle signal indicative of a current steering wheel angle of the vehicle, a speed sensor for detecting and outputting a speed signal indicative of a current speed of the vehicle, and a yaw rate sensor for detecting and outputting a signal indicative of a current yaw rate of the vehicle, wherein the steering angle of the rear wheels is established according to an operating position of an electric motor which drives the rear wheels via a reduction gear, said controlling apparatus further comprising:

a position detector for detecting and outputting a detection signal indicative of a current steering angle of the rear wheels;

an operating unit for (a) receiving the steering wheel angle signal from the steering wheel angle sensor, the speed signal from the speed sensor, the yaw rate signal from the yaw rate sensor and the detection signal from the position detector, (b) applying a predetermined gain to the yaw rate signal to obtain an adjusted yaw rate signal indicative of an adjusted current yaw rate, (c) calculating a desired steering angle of the rear wheels from the current steering wheel angle indicated by the steering wheel angle signal, the current speed indicated by the speed signal, and the adjusted current yaw rate indicated by the adjusted yaw rate signal, (d) calculating a steering angle command signal indicative of a difference between the desired steering angle of the rear wheels and the current steering angle of the rear wheels indicated by the detection signal, and (e) outputting the steering angle command value to a motor driver of the electric motor;

wherein said operating unit includes means for judging that the rear wheels are vibrating when the difference between the desired steering angle of the rear wheels and the current steering angle of the rear wheels repeatedly fluctuates between positive and negative values at least a predetermined number of times within a preset time interval and an absolute peak value of the difference is at least a preset value during the preset time interval, and wherein said operating unit further includes means for reducing a value of the gain applied to the yaw rate signal when said operating unit judges that the rear wheels are vibrating, the gain being reduced to an extent that the absolute peak value of the difference becomes less than the preset value.