Power transmission

Abstract

A system and method for pulse-width modulation of multiple solenoid-operated valves in an electrohydraulic servo system employing a microprocessor-based digital controller. Solenoid-energization pulse widths are identified by comparison of operator command input signals to feedback signals responsive to actual motion at the actuators and loads. During each modulation period, all solenoids are initially selectively simultaneously energized as a function of binary information stored in an energization control register, and the shortest energization pulse duration is identified. After a delay corresponding to such shortest duration, during which the microprocessor may perform other control functions, the solenoids associated with such shortest duration are selectively de-energized as a function of binary information stored in a de-energization control register. The next-shortest duration is then identified, and the process again delays for a time equal to the difference between such next-shortest duration and the previous duration. The process of identifying pulse durations of increasing length and correspondingly deenergizing the solenoids continues until all pulse durations have been accommodated or until the modulation period terminates, at which point the entire control process rebegins.