Fundamentals of Automation

What Is Proportional Control?

Proportional control means that the output of a system is directly related to the input. System inputs include both a target value, which is the desired result such as a specific position, pressure, or force level, and the real-time measurement of actual progress toward that goal. With proportional control, the output of a system can be any interim value within a fixed range. For example, an air cylinder can be positioned anywhere between fully retracted and fully extended. In another example, a tank’s pressure can be maintained anywhere between vacuum and full line pressure. Proportional control is a cost effective way to create systems with high flexibility and dynamic control.

Closed Loop vs. Open Loop

If you want to control it you must measure it. Closed loop systems are actively managed using feedback from sensors that monitor actual performance. This feedback is continuously compared to the desired value and corrective action is taken until the goal is achieved. While open loop systems are simpler, actual performance is left to chance. Closed loop systems are needed when precision is required, when the system may be subjected to external disturbances, or when the desired value might change during a process.

Technology Overview

Linear Force Motor Vs. Solenoid

Although solenoids have been the workhorse of pneumatic valves, they are slow, non-linear, and hard to control. And, you need two of them for directional control. In its patented design, Enfield Technologies uses a specialized directly coupled linear force motor.

This motor uses a voice-coil type winding and an intensified rare earth magnetic field. With low inertia and bi-directional control, a single valve operates in true linear fashion four to seven times faster than a double solenoid valve, allowing more cycles in the same amount of time with fewer components.

Development Kits

Development kits are available for position, pressure or flow control applications in a variety of component configurations. Custom kits can be provided for special applications. Contact Enfield Technologies for configuration and pricing.