I-PD controller as an structural alternative to servo/regulation tradeoff tuning

Abstract

One of the recurrent topics in the PI/PID literature of recent years is the incorporation of the tradeoff between the two possible modes of closed-loop operation: servo and regulation. Tuning rules are usually provided as for servo or regulation. Operator should choose which one to apply depending on the most usual loop operation. As an alternative, the so called tradeoff tunings provide a controller tuning that is not optimal in either of the operation modes but aims to provide a reasonable (in fact, the best) tradeoff among both in such a way that the loss of performance is minimised with respect to the corresponding optimal tunings. In this paper the use of the I-PD controller structure is proposed as an structural solution to the tradeoff tuning. The proposal states that a direct, simple and efficient solution is found if the controller tuning is addressed for the servo mode but using the I-PD controller structure. This is the feedback error just drives the integral mode or, if preferred, a two degrees of freedom controller with the set-point weight to zero.