ELECTRIC POWER ASSISTED STEERING SYSTEM WITH FRICTION COMPENSATION AND METHOD FOR CONTROLLING THE SYSTEM

摘要

A steering gear (12) has a rack bar (36) and a housing (22). The rack bar (36) is movable linearly relative to the housing (22) for turning steerable wheels (68) of the vehicle. Movement of the rack bar (36) relative to the housing (22) is resisted by friction. An electric motor (14) is connected with the rack bar (36) and causes linear movement of the rack bar (36) relative to the housing (22). A controller (16), in response to a vehicle speed signal and a torsion signal, generates a motor control signal for controlling the electric motor (14). The controller (16) stores data indicative of the friction resisting movement of the rack bar (36) relative to the housing (22) of the steering gear (12). The controller (16) modifies the motor control signal to compensate for the friction.