Design Of Mixed H₂ /H_∞ Robust Model Predictive Controller

Model Predictive Control (MPC) has been developed since 1970s. It has been recognized as an efficient advanced process control strategy that can explicitly deal with various engineering constrains. Among them, Robust MPC (RMPC) has received particular attention when dealing with ubiquitous external disturbances and model uncertainties in practical applications. It is important to design controllers to stabilize the closed-loop system yet to achieve a satisfactory control performance in the MPC synthesis.In RMPC research, the closed-loop stability and control performance of RMPC with H₂ or H∞performance index have been widely investigated. However, the design approach of employing mixed H₂ /H∞performance indices, which can handle closed-loop stability and conrol performance simultaneously, remains a fundamental question on how to design RMPC algorithms for different systems to tradeoff among system performance, robustness, initial feasible regions and online computational butden. This is also the key issue that this dissertation is focusing on. The detailed research topics are listed as follows: To remedy the drawbacks of traditional MPC algorithm, we firstly apply mixed H₂ /H∞design method to ensure the recursive feasibility of RMPC problem. We propose a control design strategy to reduce the conservativeness of the single feedback control law as well as the online computational loads.We study the synthesis methods to design RMPC for the systems with parameter and structural uncertainties. We introduce a multi-step control strategy to reduce the conservativeness and expand the initial feasible region and then analyze the recursive feasibilities. We further design an ellipsoid invariant set offline and later optimize a combination of coefficients online to mitigate the real time computational burden and achieve better performance. Meanwhile, we apply the method of input to state stability(ISS) to analyse the stabibility of closed-loop system with structural uncertainties.We develop an RMPC design method to deal with actuator saturations and also to meet the requirements of multi-objective control. The closed-loop system performance and robustness have been carefully studied.For the system with time delay, a RMPC synthesis method is proposed to use mixed H₂ /H∞design approach. We analyze its feasibility and then apply it to uncertain system.