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