Design of a multivariable self-tuning PID controller with an internal model structure

PID control schemes have been widely used for various process control systems for a long time. However, since such processes have relatively large time-delays and uncertainties caused by modeling errors and system fluctuation, it is non-trivial to choose suitable PID parameters. In the paper, a design scheme of a multivariable self-tuning PID controllers is proposed for unknown processes with time-delays. A parallel internal model is firstly designed in order to compensate the time-delays. The PID control system is then constructed for the augmented system. The PID control parameters are tuned adaptively based on online process identification and the relationship between the PID control and the minimum variance control laws