Decoupling Control Design Based On Internal Model Control For Multivariable System With Time Delays

Present industry processes are basically of multivariable system, espe-cially in the petroleum refining and chemical industrial. Due to the parti-cularity of such complex process control requirements, such as the over-shoot amount limit, adjusting time and control precision demand, time delays must be taken into considered as an important factor. Therefore, the research of multivariable system control plays an important role in-creasingly in the present process control.During the study in the control design of multivariable system with time delays, centralized controller can decouple the multivariable system effectively. The centralized controller can be divided into static decoupl-ing controller and dynamic decoupling controller, and two kinds of me-thod have their own advantages according different meeting of process control.The parameters of controller are tuned via IMC (Internal Model Con-trol) criteria. To achieve the desired system output, appreciate filter para-meters must be adjusted when time delays are considered. The adjusting parameters can guarantee the system robust stability and nominal perfor-mance when the model can’t match the system perfectly. The robust sta- bility and nominal performance of internal model control are analyzed.Since traditional decentralized control can’t obtain the non-interfering control, reflexive decoupling control based on SVD (singular value de-composition) is proposed in this paper. Smith compensator is applied, in which parameters of PI controller are tuned via IMC. PI controllers are disposed with two unitary matrices to achieve decoupling controllers. Noteworthy improvement of the proposed method is that it can be applied to both square and non-square system. Also, the error is eliminated via this design, which is caused by model reduction and system parameter perturbation. The design is simple and easy to be implemented.Moreover, complete Smith composition is designed based on inverted decoupling to solve the problem caused by incomplete time composition. Necessary conditions are proposed to guarantee the implement of the de-coupler, including both time delays and the static gain. Two illustrative examples are provided to demonstrate the effectiveness of the proposed method, resistance to system disturbance.