Research On Robust Multiple-model Control And Application Of 3-DOF Helicopter

The 3-DOF helicopter system is a typical multiple-input multiple-output system with the features of higher non-linearity,uncertainties due to external disturbances,so it is very difficult to design an accurate and effective controller for the system.In order to simplify controller's design,under certain conditions,the nonlinear model of 3-DOF helicopter is approximate to linear model.In addition,based on the design principle of linear quadratic optimal regulator?LQR?,an LQR controller for the helicopter is designed.LQR control method can realize the optimal control for linear system,but it is difficult to control the 3-DOF helicopter system using LQR control method only due to the uncertainties that the system has.Thus,based on the LQR control theory,a mixed H₂/H_? robust controller for 3-DOF helicopter is designed by using H_? robust theory.Because the robust H_? theory can effectively handle the system's uncertainties problem,and make the system have robust stability.Therefore,the H₂/H_? control method can not only make the helicopter system get good system performance,but also make the system maintain certain robust stability.When the 3-DOF helicopter model is in different flight states,the system need different system performance and robust stability.For example,when the helicopter model is in rising state,we require the system quickly track the given signal,and has a smaller overshoot.But when the helicopter model is in a steady stable state,it needs a good robust stability.Therefore,based on the mixed H₂/H_? robust control method,model set is built according to different elevation angel.Then,according to the different flight state of the helicopter,different H_? performance indexes are chosen to design sub controller and weighted approach is adopted to make the sub controllers form global controller.In this way,the multiple-model weighted controller for 3-DOF helicopter is designed.The effectiveness of this method is proved by MATLAB simulation and semi physical simulation experiment.It is difficult to analyze multiple-model weighted control on theory,so we propose a robust guaranteed control method based on multiple-model switching based on H_? robust controller,H₂ robust controller and switching system relative theory.The biggest difficulty of multiple-model switching control is to restrain the jitter on the switching point and to ensure the smoothness of the switching process.The robust guaranteed switching controller proposed in this paper,which applies the H_? robust control theory on every sub model and switching process between sub models,not only makes the system more robust,but also effectively solves the problem of smooth switching among models.The H₂ control theory is also applied to the helicopter switching system,which makes the helicopter system have a better system performance.Finally,the simulation results of MATLAB show that the proposed method achieves the expected goal in theory.