Approaching Servoclass Tracking Performance by a Proportional Valve-Controlled System

An industry-grade proportional valve is much cheaper and rugged than a servovalve. A feedforward controller for a proportional valved system has been developed here to achieve tracking controls beyond 1 Hz that are usually attained by servovalves. For compensating the higher nonlinearities, feedforward controllers have been designed offline by proposing appropriate static models for friction and valve flow and executing the supporting experiments. These controllers have been implemented with real-time PID feedback of only the piston displacement. Excellent tracking performance has been obtained up to 2 Hz that has deteriorated with an increase in cylinder friction.