Robust multiloop PID controller design: A successive semidefinite programming approach

The problem of robust multiloop proportional-integral-derivative (PID) cont roller tuning for multivariable processes is addressed in this paper. The p roblem is formulated in the H-infinity control framework, and the controlle r parameters are determined based on both user-specified performance and ro bust stability. The PID settings are computed by solving a nonlinear optimi zation problem with matrix inequality constraints, using a successive semid efinite programming approach. The proposed method is illustrated by a simpl e case study that investigates robust PID control of a distillation column.