A novel relay auto-tuning technique for processes with integration

Abstract

In this paper a novel idea of inserting a differentiator in front of the relay is presented. This technique is applicable to a process with integration. The advantage is that the time taken for the relay experiment can be shortened by as much as 100%. A special case of an asymmetrical relay - relay with DC bias - is also analysed. This paper shows that a common process model used in the industry - the first-order plus dead-time process model - can be obtained from the oscillation produced by the relay with DC bias. Once a process model is obtained, many controller design techniques are available. The techniques described in this paper were successfully implemented in a laboratory experiment on a tank level system.