High resolution pulse width modulation

An electrohydraulic system comprising

• means responsive to an electrical control signal for variably controlling flow of hydraulic fluid, and
• microprocessor-based control means including means for receiving an input command, means for generating a flow command as a function of said input command, means for sampling said input command and updating said flow command at predetermined fixed sampling intervals, and means for directing a pulse width modulated control signal to said flow-controlling means as a function of said flow command,
• said pulse width modulated control signal consisting of a continuous series of alternating on and off half-cycles at a fixed period less than said sampling interval, all on half-cycles having an identical base time duration and all off half-cycles having an identical base time duration, said base time durations being updated at each said sampling interval and remaining constant during each sampling interval,
• said control means further including means for selectively increasing or decreasing time durations of said on and off half-cycles from said base time durations within each said sampling interval while maintaining constant said fixed period of said pulse width modulated control signal.