Abstract:

To solve the trajectory tracking and attitude control problems of quadcopter aircraft during flight, a sliding mode variable structure nonlinear controller is designed based on an improved new reaching law and sliding mode function. According to the underactuation, strong coupling and multi-variable characteristics of quadcopter aircraft, the whole force analysis of its system is carried out, and the system mathematical model is simplified based on Newton's second law and Euler's momentum equation. Based on the traditional exponential reaching law and combined with the double-power term, proportional term and improved variable exponential term, a new reaching law sliding mode controller is designed for the inner and outer loops of the system. The output of the outer loop position controller is taken as the expected input of the inner loop controller to form a closed loop system in which the outer loop controls the inner loop, and the stability of the system is proved by the Lyapunov stability theorem. Simulation results show that the proposed method has shorter response time, better tracking performance, and smaller steady-state error than traditional reaching law sliding mode controllers in fixed-point levitation and complex three-dimensional trajectory tracking experiments.

Key words: quadcopter, location tracking, attitude control, novel reaching law, sliding mode function, nonlinear controller, Lyapunov, simulation