Positioning apparatus and method utilizing PWM control of a double-acting hydraulic cylinder

摘要

A double-acting hydraulic cylinder is controlled by a pair of three-way solenoid valves respectively fluid connected to the two ends of the cylinder and energized in parallel with a continuous stream of pulse width modulated (PWM) pulses to create a mean effective fluid pressure balance at the cylinder ends that hold a desired position of a connected load and mean effective fluid pressure imbalances in the cylinder ends that produce variable rate load movement in either of two directions to a desired new position, all determined by the pulse duty cycle.