Hydraulic servovalves  |  Pneumatic servovalves | Servo Electronics

Pneumatic R-DDV™ servovalves

The new Model 27N pneumatic R-DDV™ servovalve from HR Textron is designed for use in high precision, closed-loop feedback motion control systems. Industrial applications include control of load position, velocity, acceleration and force. Applications as diverse as automotive vehicle component testing and manufacturing, semiconductor manufacturing, packaging, assembly, automation and robotics, biomedical testing and lumber processing can benefit from the enhanced level of control offered by this cost-effective technology.

The high performing HR Textron pneumatic servovalve offers exceptional, 80 Hz frequency response with 10 flow rates from 0. 018 Cv to 0.9 Cv. Fast response time and a wide flow range permit the motion control system to be optimized for a variety of speeds, loads and accuracies.

Used in conjunction with a low friction cylinder, typical linear load speeds would range 0 to 100 inches per second and load weights 0 to 100 pounds. Depending on controller capability and system parameters, linear position resolution can be as fine as ±0.002 inch.

The HR Textron Model 27N pneumatic R-DDV™ servovalve has also demonstrated high accuracy in pneumatic applications that require precise control of force or pressure, such as fine polishing of painted surfaces or lapping of computer hard discs. The servovalve can attain pneumatic system pressure repeatability of less than 0.01 psi on a 100 psi system.

Low servovalve cost is achieved with HR Textron's patented R-DDV™ servovalve rotary direct-drive design which controls flow through the valve in a single stage that is independent of supply pressure. There are no springs, nozzles, filters or pilot valves to maintain or replace.

How It Works
In simplest terms, a limited angle dc torque motor drives a valve spool directly through an "eccentric" built into the motor shaft. Rotary motion of the motor shaft results in linear motion of the spool, which in turn modulates flow through the valve control ports.

The R-DDV™ servovalve incorporates an integrated electronic controller with a sophisticated algorithm, which is packaged into the motor enclosure. The controller compares the electronically monitored spool position with the input command signal. The resulting error signal is amplified to produce a current, which drives the motor to the commanded position. The signal is electronically enhanced to give optimum valve performance – hysteresis, linearity and internal leakage are minimized while dynamic performance and stability are optimized.

R-DDV™ servovalves are single stage devices. There are no fluid amplifiers or first stage pilot valves. Therefore, R-DDV™ servovalves operate independent of supply pressure -- and there are no orifice assemblies, nozzles, jets or filters that are subject to contamination, wear or maintenance. Robust design features ensure excellent tolerance of pressure spikes as well as mechanical shock and vibration.

Pneumatic Systems

Previously, pneumatic industrial control systems were limited to solenoid valves to drive pneumatic actuators, with loads positioned by mechanical stops or by opening and closing a solenoid valve in response to discrete signals from adjustable limit switches. Solenoid valves cannot automatically compensate for changes in load and air pressure, or vary the position of a load, without resetting and recalibrating sensors or mechanical stops.

Pneumatic R-DDV™ servovalves offer industrial motion engineers the opportunity to create high performance pneumatic servo systems -- incorporating velocity, acceleration, deceleration, force and positioning parameters previously unattainable. All with a reliable and economical valve package priced competitively with existing non-servo products.

Specifications
Review the specification information at this web site, then contact Flow Products, Inc. at 800-631-2029 to review your specific application.