Research On Internal Model Control For Processes With Time Delays

Owing to the time delays that commonly exists in industrial processes, the traditional PID control cannot satisfy the rising control performance. Due to the advantages of less adjusTable parameters and clear relationship between parameters and performance, Internal model control method is widely accepted. However, the RHP poles and internal coupling relationships between multi-loop restricted the application of the IMC(internal model cotnrol) in time-delay systems. This paper focuses on the research of the IMC (internal model control method) application problems in the unsTable process and multivariable systems with time delays. In this work the conventional IMC controllers are firstly analyzed to clarify some drawbacks. Then we proposed an IMC-based co-balance design objective in terms of servo/regulator and performance/robustness. Finally, the co-balance controller design is realized on the basis of proposed objective.This paper proposes a modified IMC control method to solve the problem that the internal model control structure can not directly control the unsTable processes. The setpoint tracking controller and the controlled object are regarded as a generalized object. Then the error between the generalized controlled object and the predicted value is taken as a disturbance signal to reject. Without feedback loop, this method reduces the complexity of the control system design. The method is applied to a wide range of unsTable processes.Two degrees of freedom structure for unsTable processes could effectively balance the set point tracking and load disturbance rejection performance. However many studies lack detailed analysis of robustness and performance. In order to solve the above problems, this paper proposes a novel controller design method to obtain optimal robustness. On the basis of two degree of freedom control structure, we use an improved filter structure and analyze relationship of the controller parameters and the performance, robustness. The paper gives the scope of Ms to trade off the robustness and performance. Based on this, this paper presents an optimal internal model controller design rules under the condition of the maximum sensitivity function.Conventional inverse decoupling method can’t deal with systems containing RHP zeroes can time delay. Motivated by this drawback, this paper proposed a novel multivariable IMC-PID controller based on inverse decoupling by analyzing the characteristics of a system and illustrating realizability conditions of inverse decoupling. In case one system doesn’t meet the realizability conditions, a compensation term is introduced to obtain a decoupled plant. Then the design method of decoupler is modified specific to the decoupled plant mentioned above. The design scheme proposed by this article can realize perfect dynamic decoupling control and obtain well robustness.