Design And Implementation Of Attitude Control Systems For A Small-scale Unmanned Helicopter Based On Sliding Mode

Small-scale unmanned helicopters, having advantages of low cost, small size, high maneuverability and so on, have received widespread attention in the world scope, and obtained extensive researches and applications in the fields of both military and civilian.If a small-scale unmanned helicopter is to complete all kinds of tasks without human intervention, it must first have a flight control system with high performances. Attitude control systems are the foundations and critical sections of the automatic flight control systems of a small-scale unmanned helicopter, and the purpose of this paper is to establish a robust attitude controller for a small-scale unmanned helicopter, on the basis of a nonlinear dynamic model, using the method of sliding mode control and adaptive sliding mode control. The main research contents of this paper are listed as follows:1) First,the unmanned helicopter hardware system structure is introduced based on a Raptor 90 3D helicopter. Second,the nonlinear dynamic model of the small-scale unmanned helicopter is established for the study of the roll and pitch attitude control,which mainly includes the rigid body dynamics and kinematics model and main rotor dynamics model, and lays the foundation for the design of the attitude control system.2) We firstly analyze the dynamic model of the small-scale unmanned helicopter, and then design a double loop integral sliding mode attitude controller for the Raptor 90 3D helicopter on the basis of the nonlinear dynamic model, based on the assumption that the dynamic response of the attitude angle rate is faster than the response of the attitude angle.We also design an extended state observer to estimate the system uncertainty and external disturbance. Double loop sliding mode controller has a simple structure and is easy for project implementation, but when the small-scale unmanned helicopter makes some high maneuverings, its control performances may decline, thus we further design a monocyclic integral sliding mode attitude controller to improve the control precision. Several simulations are carried out to evaluate the effectiveness of the proposed controllers and physical experiments are carried out on a test platform for the same purpose. Simulation and physical experiment results are given to illustrate the effectiveness of the two kinds of sliding mode controllers.3) Because the sliding model controllers designed before need the upper bound of the uncertainty, an adaptive sliding mode controller based on the extended state observer is designed. It combines an adaptive sliding mode control law based on a real sliding mode surface with the extended state observer designed before, by which we can obtain the online estimation of the sliding mode gain and thus the upper bound of the uncertainty is not needed. Adaptive sliding mode controllers with double loop and single loop structure are designed respectively, and the simulation and experimental results show the effectiveness and robust of the designed controllers.