Model-free simultaneous design of multiloop PID controllers for TITO interactive processes with time delays

Abstract

This paper presents a model-free simultaneous design method of multiloop PID controllers for two-input-two-output (TITO) interactive processes with time delays. The controller design directly exploits experimental process data without identifying process models. By employing the virtual reference approach, structure of the reference model matrix achievable by the multiloop control scheme is derived and the decentralized multiloop controllers that exactly solve a model-reference control problem are synthesized accordingly. Then, each controller is approximated to PID structure through a frequency-domain approach. The PID controllers design depends on the reference models that are optimally specified by minimizing a model-reference control criterion. Because the controller design is applicable to closed-loop data, it is preferable in industrial applications and the method can be used to improve existing underperforming controllers. Simulation studies show the effectiveness of the proposed design method.