Patent ID: 9669867
Date: 2017-06-06
CPC Classifications: B62D

Claim:
1. A method for characterizing a stiction condition using a rotary actuator in an electrically-assisted steering system, wherein the steering system includes a rack, a pinion gear disposed on an end of a steering shaft in meshed engagement with the rack, a steering assist motor, and a drive mechanism driven via the steering assist motor to electrically assist a steering maneuver, the method comprising: transmitting a first steering control signal from a controller to the rotary actuator for a calibrated duration, wherein the first steering control signal is a periodic steering conditioning signal having a calibrated steering frequency and a calibrated peak steering angle; receiving, via the steering assist motor, a second steering control signal from the controller during and after transmission of the first steering control signal to thereby cause the steering assist motor to electrically assist in the steering maneuver via the drive mechanism; transmitting a third steering control signal from the controller to the rotary actuator after the calibrated duration and while still transmitting the second steering control signal, wherein the third steering control signal is a commanded steering angle that causes alternate rotation of the steering shaft, with a constant acceleration and deceleration, respectively to and from a target steering angle rate; measuring a steering torque output from the rotary actuator while alternately rotating the steering shaft; and executing a control action with respect to the steering system, via the controller, when a difference in a local maximum and minimum peak amplitude of the measured steering torque output exceeds a calibrated threshold difference indicative of the stiction condition.