Rotary Direct-Drive Valve (RDDV) servovalves use a limited angle, rotary torque motor to produce linear spool motion and modulate fluid flow through the valve’s control ports. They have no orifice assemblies, nozzles, jets or filters to become clogged and can be applied to hydraulic or pneumatic operations, providing flows of 0.18 to 60 gpm for hydraulics and 0.45 to 136 scfm for pneumatics. The stainless-steel devices are rated at vibrations of 40 G and shock at 60 G. Internal leakage is low for the RDDV servovalves, which accommodate maximum steady-state pressures to 5,000 psi. An integrated electronic controller maintains a user-specified spool position by comparing the command signal to the actual position and adjusting the spool position by the measured error. A general-purpose PID control card, model EC250GP, offers adjustability and options for position control-loop functions for servovalves with the electronic feedback controller. It also provides a second feedback loop for acceleration, force, velocity, and pressure.
Woodward Inc., (800) 659-4229