Robust two-degree of freedom H ∞ control design for a twin rotor multi-input multi-output system with external disturbances and model uncertainties

Abstract

The control of twin rotor multi-input multi-output system is difficult as it is subjected to model uncertainties and external disturbances. Furthermore, there also exists a coupling between pitch and yaw positions, which makes the system more difficult to control them separately. Considering the above difficulties in twin rotor multi-input multi-output system control, $H_{\infty }\mathrm{-}\mathrm{based}$ robust controller is designed to handle the model uncertainties and external disturbances with two-degree-of-freedom. A mixed sensitivity approach is employed to represent the uncertainties and external disturbances arise in the twin rotor multi-input multi-output system. For performance analysis, first the proposed two-degree-of-freedom $H_{\infty }$ controller is compared with the ‘Linear Quadratic Regulator-Linear Matrix Inequality’–based robust proportional–integral–derivative controller and Internal Model Control–based proportional–integral–derivative controller in MATLAB/Simulation and then in experimentation. From the obtained results, it is confirmed that the proposed controller exhibits enhanced robustness, faster tracking performance and accurate disturbance attenuation, when compared with Linear Quadratic Regulator-Linear Matrix Inequality–based robust proportional–integral–derivative controller and Internal Model Control–based proportional–integral–derivative controller in face of external disturbances and uncertainties.