This paper demonstrates a number of PI controller tuning methods being used to tune a temperature controller for a real air heater. Indices expressing setpoint tracking and disturbance compensation and stability margin (robustness) are calculated. From these indices and a personal impression about how quick a method is to deliver the tuning result and how simple it is to use, a winning method is identified.

ABSTRACT--True membranes are no-compression structures which exhibit the unique response of wrinkling. Prediction of the associated wrinkle parameters is of practical importance. Accurate measurement of membrane wrinkling has heretofore not been presented in the literature; among other requirements, noncontact methods must be used. First, some background information on membrane wrinkling prediction and measurement is given. Then, an experimental apparatus is discussed within which a membrane was subject to planar loading. The measurement system consisted of a capacitance-based noncontact displacement sensor mounted in an XYZ frame. A computer controlled the forces applied to the membrane, as well as the motion of the XYZ frame during data acquisition. Results are presented and conclusions are drawn regarding the wrinkle parameters.

A novel experimental method -here denoted the Good Gain method -for tuning PI controllers is proposed. The method can be regarded as an alternative to the famous Ziegler-Nichols' Ultimate Gain method. The approach taken resembles the Ziegler-Nichols' method as it is based on experiments with the closed loop system with proportional control. However, the method does not require severe process upset during the tuning like sustained oscillations. Only well-damped responses are assumed. Furthermore, in the present study it is demonstrated that the approach typically gives better stability robustness comparing with the Ziegler-Nichols' method. The method is relatively simple to use which is beneficial for the user. A theoretical rationale based on second order dynamics is given.

A modification of the PI setting of the Ziegler-Nichols closed loop tuning method is proposed. The modification is based on a combination of the Skogestad SIMC tuning formulas for "integrator plus time-delay" processes with the Ziegler-Nichols tuning formulas assuming that the process is modeled as an "integrator plus time-delay" process. The resulting PI settings provide improved stability margins compared with those obtained with the original Ziegler-Nichols PI settings. Compared with the well-known TyreusLuyben PI settings, the proposed PI settings give improved disturbance compensation. For processes with zero or a negligible time-delay, but with some lags in the form of time-constants, tuning based on ultimate gain and ultimate period may give poor results. Successful PI settings for such processes are proposed.

No abstract