Direct synthesis approach of PID controller for second-order delayed unstable processes

In general, PID control is used to control stable processes. For second-order delayed unstable processes, a new PID controller tuning method based on direct synthesis approach is proposed in this paper. The proposed method obtains explicit expression of PID tuning parameters using specification of the desired closed-loop transfer function for disturbance responses. Performance and robustness metrics are used as evaluation criteria to assess the controller performance. Simulation and computation results demonstrate that the design method for the PID controller provides good control performance in terms of disturbance rejection, set-point tracking, and strong robustness.