Loop-shaping design of PID controllers with constant Ti/Td ratio

This paper presents new tuning rules for PIDcontrollers based on loop shaping. Previous research has shownthat maximization of the integral gain subject to constraints on the maximumsensitivity is an efficient design method for PI controllers, but thatadditional constraints are needed for design of PID controllers. Inthis paper, an additional constraint is obtained by restricting theratio between integral time and derivative time. It is shownthat this gives a numerically efficient method that gives good resultsfor a large class of processes.