Patent ID: 6069460
Filing Date: 2000-05-30
Classification: B62D

Abstract:
A method of controlling an electro-hydraulic power assist steering system including a variable-speed electric motor for pumping hydraulic fluid in the system, the method comprising:monitoring vehicle speed;monitoring vehicle steering wheel angle;monitoring vehicle steering wheel turning rate;determining a mode of operation of the vehicle based on the monitored vehicle speed such that below a predetermined level of speed the vehicle is determined to be in a park mode and at or above this level the vehicle is determined to be in a drive mode;controlling the speed of the variable speed electric motor to vary hydraulic fluid flow in the power assist steering system based upon said monitored vehicle steering wheel turning rate if said parking mode is determined; andcontrolling the speed of the variable speed electric motor to vary hydraulic fluid flow in the power assist steering system based upon said monitored vehicle speed, vehicle steering wheel angle and vehicle steering wheel turning rate if said driving mode is determined.