Gm Global Technolgoy Operations, Inc.

Randy Scott Miller

Brian Jerome Magnus

Dennis C Eckhardt

Paul Ashby Murphy

Alan Crary Davis

In a vehicle with a hand wheel, steerable wheels positionally responsive to the hand wheel and a steering position sensor coupled to the handwheel and providing a handwheel angle signal indicative of an angular position of the handwheel, a steering angle determination method comprising the steps of: first filtering the handwheel angle signal to provide a first filter output; defining a comparison window around the first filter output; comparing the handwheel angle signal to the comparison window; when the handwheel angle signal is within the comparison window, second filtering the handwheel angle signal to provide a second filter output; when the handwheel angle signal is not within the comparison window, maintaining the second filter output fixed; and determining a steer angle signal as the difference between the handwheel angle signal and the second filter output, wherein offsets between the handwheel angle signal and steered positions of the steerable wheels are compensated for.

Steering angle determaination method and apparatus

A closed center power steering gear having a spool shaft connected to a steering wheel of the motor vehicle, a pinion head connected to steered wheels of the motor vehicle, and a control valve between a fluid accumulator and a working chamber of a steering assist fluid motor. The control valve includes a poppet on the spool shaft having closed and open positions blocking and permitting, respectively, flow from the accumulator to the fluid motor working chamber, a cam on the pinion head, a cam follower on the spool shaft, and a pressure control spring between the cam follower and the poppet. The cam, the cam follower, and the pressure control spring cooperate during relative rotation between the spool shaft and the pinion head to shift the poppet to its open position. Boost pressure in the fluid motor working chamber increases and reacts against the poppet to compress the pressure control spring and shift the poppet to its closed position. The contour of the cam is calculated to cause steering assist boost pressure in the working chamber to increase at a rate faster than applied torque increases thereby to achieve a nonlinear relationship between boost pressure and applied torque.

Closed center power steering gear

A motor vehicle power steering system including a hydraulic pump, a fluid motor, and an electronic control valve which regulates boost pressure independent of pump discharge flow rate so that the pump does not require a constant flow valve. The flow area of a throttling orifice which determines the magnitude of boost pressure depends on the magnitude of a pilot pressure in a pilot pressure chamber behind a valve spool of the electronic control valve. The pilot pressure is regulated by a solenoid controlled pintle. The duty cycle of the solenoid is controlled in open-loop fashion by an electronic control module of the power steering system in response to signals from a steering wheel torque sensor of the power steering system. Fluctuations in the discharge flow rate of the hydraulic pump attributable to changes in engine speed induce spool movements to increase or decrease the flow area of the throttling orifice to maintain boost pressure consistent with the scheduled pilot pressure. A direction control valve responds to the direction of steering wheel torque to expose either a right turn or left turn working chamber of the fluid motor to boost pressure.

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Frankenmuth, MI, United States of America

Randy Scott Miller