Design and tuning of valve position controllers with industrial applications

Mid-ranging refers to control problems where there are two manipulated inputs and only one output to control. Most mid-ranging controllers in industrial use today are based on the valve position control concept. Presently, design and tuning of valve position control schemes is largely done ad hoc. As a result, much time is spent devising control strategies that may work well in one application, but not nearly so well in another. To address this problem, we set out to devise a systematic approach to the design and tuning of valve position controllers. The new method was tested in simulation, and pilot plant and paper mill examples were used to demonstrate the performance of the method in several real-life applications.. Overall, the proposed design was able to reject disturbances quicker and mid-range faster, and with less oscillation than conventional schemes. This approach may be applied to virtually any mid-ranging control application and is easily implemented on any distributed control system.