PROPORTIONAL-INTEGRAL-PLUS (PIP) CONTROL OF TIME-DELAY SYSTEMS

The paper shows that the digital proportional-integral-plus (PIP) cont roller formulated within the context of non-minimum state space (NMSS) control system design methodology is directly equivalent, under certa in non-restrictive pole assignment conditions, to the equivalent digit al Smith predictor (SP) control system for time delay systems. This al lows SP controllers to be considered within the context of NMSS state variable feedback control, so that optimal design methods can be explo ited to enhance the performance of the SP controller. Alternatively, s ince the PIP design strategy provides a more flexible approach, which subsumes the SP controller as one option, it provides a superior basis for general control system design. The paper also discusses the robus tness and disturbance response characteristics of the two PIP control structures that emerge from the analysis and demonstrates the efficacy of the design methods through simulation examples and the design of a climate control system for a large horticultural glasshouse system.