By Bob Wojcik
Proportional directional control valves are available that incorporate a variety of accuracy and feedback options. These proportional valves begin with those that simply control the stroke of the directional valve spool with metering notches in order to provide flow control while providing directional control to the actuator.
The next, more accurate variation is a proportional valve with spool position feedback, in additional to the basic flow and position control. By incorporating positional feedback, this more complex version of the proportional valve offers a greater degree of accuracy in controlling the speed, direction, and position of the actuator.
The most accurate proportional valve is one with a much higher frequency response which can, in some cases, nearly parallel the performance obtained with servo valves. These proportional control valves are suitable for use in very accurate, high response, position, velocity, and force control closed-loop systems.
Proportional valves are generally specified in order to gain an overall smoother machine operation as well as improving production rates and quality.
Proportional directional control valves are available with or without on-board electronic feedback and control. This selection depends upon which configuration best suits the application and control system options. Proportional valve systems can also be implemented with the electronic interface for control of the entire machine.
Proportional valves are well suited for both mobile and industrial applications. For mobile applications, Quality Hydraulics & Pneumatics, Inc. offers high-quality brands including HydraForce valves, and Bucher Hydraulics. For industrial applications, Quality Hydraulics provides high-quality brands including Moog, Yuken Hydraulics, and Nachi Hydraulics.
As with all hydraulic systems, proportional valve circuits in particular require a high degree of filtration which will both enhance system performance as well as extending component life for the entire hydraulic system.