U-model based LMI robust controller design

In this study, an LMI (Linear Matrix Inequality) based H_∞ robust controller design approach is proposed to improve the performance of the designed U-pole placement control systems. Unlike the classical design procedures, the control-oriented U-model based nonlinear control systems cancel the nonlinearity of the nonlinear models. Therefore, the closed loop transfer function of U-pole placement control system can be regarded as a linear block. The solvability and sub-optimality of discrete-time H_∞ robust control are converted to find feasible solutions for LMIs. Once the internal parameters changed, the LMI based H_∞ controllers have a higher level of robustness compared with U-pole placement controllers. A nonlinear dynamic model is selected to test the performance of the LMI robust controller to demonstrate the proposed approach effective.