Multi-centralized control system design based on equivalent transfer functions using gain and phase-margin specifications for unstable TITO process

In this paper, a new multi centralized control system method proposed for unstable systems using gain and phase-margin specifications. Effective relative gain array based loop interactions are considered to design of off-diagonal controllers. Unstable first order plus time delay models are changed to second order plus time delay model without losing model identity to design a two degree of freedom PID diagonal controllers. Equivalent transfer function method Xiong et al. (J Process Control 17(8):665–673, 2007) is extended to unstable system. Simulation results show that; designed robust control system gives good response and control action. Performance evaluation is done by integral absolute error criteria.