| 摘要 |
A method of operating an electric power steering system, wherein the steering system comprises a steering wheel coupled to a steering column, a pinion engaging a toothed rack to operate steerable wheels of a vehicle, at least one sensor for measuring a torque applied to the steering column or a force applied to the rack, and an servo motor supplying steering assist to support a steering effort of a driver, the torque sensor and the servo motor being connected to a control unit, the method comprising the following steps: a) continuously monitoring the rack load or the pinion torque using the signal from at least one sensor by direct measurement or estimation in a state observer, b) continuously monitoring the motor speed, c) when the motor speed is near zero or equal to zero: deriving the rack load change from the rack load or the pinion torque, d) calculate a reference motor movement which would be expected for the rack load change if no friction were present, e) if the motor movement is smaller than the reference motor movement, then request first additional steering assist torque, and f) proceed to step c).
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