Robust Sliding Mode Control Theory And Its Application In Unmanned Helicopter

The development of unmanned helicopters with special configurations has been the hot research direction all the time.Symmetrical layout of the rotor/ducted fan-type unmanned helicopter has a compact structure,high efficiency,safety and reliability due to the novel structure and aerodynamic layout.However,there are significant differences between the new unmanned helicopter with conventional single-rotor ones due to the special structure,maneuvering and flight characteristics,and the new helicopter has strong coupling,fast time-varying and non-linear characteristics.The flight control system design needs to face many challenges.In this paper,we focus on the design of the rotor/ducted fan-type unmanned helicopter flight control system,and propose a control scheme of auxiliary surface positive invariant set sliding mode,and apply this strategy to the new unmanned helicopter robust flight control.First of all,the structural characteristics and control difficulties of the rotor/ducted fan-type unmanned helicopter are analyzed.Based on the information of the existing common helicopter and the unmanned helicopter’s prototype model,the nonlinear mathematical model of the rotor/ducted fan-type unmanned helicopter is established,and its stability and coupling are analyzed.Secondly,on the basis of the mature sensor technology and flight control and navigation technology,and according to the functional requirements and performance indexes requirements of flight control system,we should develop a set of advanced flight control system,while taking into account the feasibility and the economy of the overall design.After the overall scheme is determined,a detailed design platform including inner loop and outer loop control is built,which provides theoretical basis and practical guidance for the use of advanced control algorithms in the subsequent control law design.Thirdly,this chapter confronts a new control strategy for solving longitudinal and lateral drifting movements of the UH and a new UAS-TSMC method for quick flight trim problem.UAS-TSMC control not only owns the common sliding-mode control method for robust but also increases the convergence speed of the system state.Through numerical and HIL simulation,experimental results show the good take-off performance and landing performance and decoupling performance of the UH system.Finally,on the basis of the general sliding mode,a breakthrough is made to the auxiliary surface positive invariant set sliding mode control theory.The state constraints are introduced into the auxiliary surfaces design process,which can guarantee the state to satisfy the constraint condition in the process of convergence.Aiming at the state limited control problem of an unmanned helicopter under some extreme initial condition,this paper uses the auxiliary surface sliding mode control strategy based on the enlarged positive invariant set for the first time in the flight control system of the rotor / duct fan unmanned helicopter.The control strategy is successfully tested in numerical simulation and simulation with a hardware in the loop platform.The results verify the effectiveness and availability of the proposed control strategy for engineering application.