Force-based power steering system
View Patent ↗A power steering system includes a power cylinder, an accumulator, a reservoir, a pair of valves, and a pair of pressure transducers. The system selectively fluidly couples the accumulator and/or reservoir to the double-acting power cylinder and thereby causes the power steering system to function in the manner of a force-based power steering system.
1. An accumulator enabled power steering system comprising:
an accumulator;
a reservoir;
a power cylinder having a first port; and
a pressure transducer operable to measure a pressure at said first port;
a first valve having an input groove fluidly connected to the accumulator and a return groove fluidly connected to the reservoir, the first valve further including a first valve spool having an output groove fluidly connected to said first port;
a controller operable to provide a power control signal to the first valve based upon an error signal, wherein the error signal is based upon a difference between a control function signal and the pressure at the first port, and wherein the control function signal is determined by a control algorithm in response to an applied torque signal;
a second valve having an input groove fluidly connected to the accumulator and a return groove fluidly connected to the reservoir, the second valve further including a second valve spool having an output groove fluidly connected to a second port of the power cylinder, wherein said controller is operable to provide a power control signal to one of the first valve and the second valve based upon a polarity of the applied torque signal;
a steering wheel torque sensor operable to provide the applied torque signal;
a steering wheel coupled to the steering wheel torque sensor;
a steering shaft coupled to the steering wheel and the steering wheel torque sensor; and
a steering wheel motion direction sensor comprising:
a shaft angle encoder disc coupled to the steering shaft; and
a plurality of sensors, wherein one of the plurality of sensors is operable to count a passage of space while another of the plurality of sensors is operable to determine a desired direction of the space.