USING CONTROL ELEMENT CHARACTERISTICS TO COMPENSATE FOR PROCESS NONLINEARITIES

It is shown how the nonlinearities associated with loop components such as sensors, valves, and controllers may often be used to compensate for process characteristics. The inherent nonlinear responses of various control components are well known, and fortunately can be applied to balance the varying input-output characteristics of broad classes of common processes. As a result it is often possible to design loops which are effectively linear over wide operating ranges, using only standard commercially-available hardware and without resorting to complex mathematical analyses. Pertinent guidelines are suggested.