Tuning Guide for Basic Control Loops, 1997 Process Control, Electrical & Info. Conference Proceedings

The overwhelming majority of controllers used in the pulp and paper industry are simple PID controllers. For most control applications, a well designed and properly tuned PID control loop is all that is needed to achieve the control objectives. The majority of the PID control loops are tuned by a “trial and error” procedure. Some people actually develop a “knack” for tuning using this procedure. Unfortunately, most people do not. Until recently, if they used a tuning procedure at all, it was likely to be a quarter-amplitude-damping method such as the Ziegler-Nichols Method [1]. However, many technicians and engineers refrain from using this method because of the oscillations (cycling) that occur and the poor stability margin.

This paper discusses a more applicable tuning method called “Lambda Tuning” which has been gaining in popularity in recent years. Lambda tuning has been adopted as the preferred controller tuning method in the pulp and paper industry [2]. It is based on simple process models that can be obtained by a sequence of simple “bump” tests while the loops are in manual mode.

The step by step tuning procedures covered in this paper were developed by the author as part of committee assignment for the System Design Subcommittee of the Process Control Committee. The tuning procedures are also being converted into a TAPPI Technical Information Sheet (TIS).