Research On Internal Model Control Algorithm For Multivariable System With Time Delay

The time delay exists generally in industrial field. Due to the information feedback, it limits the control performance. There are many integrating processes with time delay in industrial field, for example boiler drum water level, which is difficult to control for load disturbance response because of the integrating term. For multivariable control systems, the coupling relationship among the control loops is the most important problem to deal.In order to solve the aforementioned control problems, in this paper, the internal model principle and development are discussed in detail and a series control strategies are designed for the conventional stable systems and unstable systems. Also, the paper gives the analytic relationship between the system response performance index(IAE)?the system robustness index(Ms) and the tuning parameter, which provides theoretical foundation for parameter setting. The internal model control can not be applied to the unstable system control directly. This paper proposes a novel TDF control strategy based on the internal model control structure to decouple the relationship between the set-point tracking and the load disturbance rejection. The controllers are designed based on the internal principle and proposes a modified filter, and improves the system performance a lot for a series of integrating processes with time delays. In the end, the paper discusses the stable range for tuning parameter and how the parameter effects the system performance and system robustness.For the multivariable system with time delays, the paper emphatically analyzes common decoupling methods and focuses on the inverted decoupling method. All multivariable systems with time delays can not be decoupled by the inverted decoupling method. Therefore, the paper provides the restricted condition and solution. For a kind of multivariable systems which does not satisfy the restricted condition, the compensation term is adopted to get generalized plant, and then the internal model controller can be designed based on the generalized plant. TDF PI controllers are introduced into the multivariable system with time delays to separate the design of the set-point tracking and the load disturbance rejection. A clear tuning method of parameters in controller is given by Ms, and the paper discusses how the set-point weight affects system response. This new control scheme gets better system response performance.