An electric power assisted steering system

Abstract

The invention discloses an electric power assisted steering system. According to the invention, a combined angular position and torque sensor assembly for use in an electric power assisted steering system comprises an input part for connection to an upper column shaft, an output part for connection to a lower column shaft, a torsion bar that interconnects the input shaft and the output shaft, a first and second upper column angular position sensing means that each produce at least one output signal that is dependent on the angular position of the upper column shaft; and a processing means which produces a first torque signal indicative of the torque carried by the torsion bar. The processing means further includes means for producing a first absolute angular position signal by processing the output signals of the first and secondary sensors in a first way and a second absolute angular positon signal processing the output of the same two sensors in a different way, and further comprises a cross checker that performs a cross check between the two absolute position signals.

Description

technical field [0001] The invention relates to the improvement of the electric power steering system. Background technique [0002] In a typical electric power steering system, an electric motor, such as a three-phase DC motor, is connected to part of the steering mechanism, specifically to a steering shaft that connects the vehicle's steering wheel to the wheels. A sensor, such as a torque sensor, generates a signal indicative of the torque applied by the driver to the steering wheel, and this signal is fed into the microprocessor. The microprocessor uses this signal to generate control signals for the motor, which indicate the torque or current required by the motor. These control signals are converted in the microprocessor into voltage waveforms for each phase of the motor, which in turn are transmitted from the microprocessor to the motor side bridge driver. [0003] The motor-side bridge driver converts the control signal, which is typically a low-level voltage wavef...

AI Technical Summary

Problems solved by technology

[0006] Although the dual channel torque sensor affords an increased degree of safety, in the event of a failure of one channel, it may not be possible to continue to safely apply the assist torque even if the other channel is not, partly because it may not be possible Distinguish which channel is faulty and which channel is reliable, and also because there is no way to provide protection so that the channel that is still good does not fail later

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