Robust Multiloop PID Controller Design:  A Successive Semidefinite Programming Approach

The problem of robust multiloop proportional-integral-derivative (PID) controller tuning for multivariable processes is addressed in this paper. The problem is formulated in the ℋ∞ control framework, and the controller parameters are determined based on both user-specified performance and robust stability. The PID settings are computed by solving a nonlinear optimization problem with matrix inequality constraints, using a successive semidefinite programming approach. The proposed method is illustrated by a simple case study that investigates robust PID control of a distillation column.