Method of measuring upper system friction for algorithm use in vehicles equipped with angle based steering control

摘要

Measuring upper system friction in REPS (Rack Electric Power Steering) Systems has not been possible without advanced driver features. By using the advanced features, it is possible to measure the friction of the i-shaft, column and FOD seal with no change to mechanical architecture. Measuring and recording this upper system friction using hysteresis type steering inputs from an angle based steering controller allows for a specific vehicle to adjust steering feel parameters, driver safety features (autonomous takeover, etc.) and predict upper system safety concerns, A pre-determined waveform steering position command of a pre-determined amplitude at a pre-determined time can be used to record torque data for the upper system with respect to pinion position. This allows for a baseline friction function to be established for a particular vehicle, enabling consistent steering wheel torques, robust to vehicle and component variation. In addition, torque data can be measured during any angle-based command to adjust the steering calibrations to maintain performance for the entire vehicle life, over various vehicle conditions. Additionally, this data can be used to detect upper system component failures.