Research On Montion Control Of An Aircraft Skin Inspection Robot Based On Switching Strategy

With the rapid development of Chinese aviation industry,the aircraft has been inseparable with everyone's lives,so the potential safety hazard of the aircraft skin surface damage has attracted greater attention.The manual inspection,which is mainly used in aircraft inspection,has many problems,such as big labor intensity,low inspection efficiency,high rate of missed detection and high cost.In addition,it can not guarantee the safety of aircraft maintenance personnel.In this paper,according to the need of automatic NDT(Non-destructive Testing)for aircraft skins,a kind of aircraft skin inspection robot is studied.Firstly,the mechanical structure of the inspection robot and its movement gaints are introduced.Considering the adsorotion system of the inspection robot,the rigid switching adsorption strategy and the flexible switching adsorption strategy are described.According to the robot's stress distribution on the plane surface,the dynamic model of robot has been established.Then,according to the characteristics of the inspection robot,a switching strategy based on event driven is designed.The adaptive controller based on support vector regression is studied for the nonlinear system of the robot,and the auxiliary variables based on distribution upper bound is designed to estimate the modeling uncertainties and unknown external disturbances.Finally,simulation results illustrate that the adaptive control scheme can guarantee the satisfactory trajectory tracking performance for the inspection robot with the unknown disturbance and the system uncertainty.Thirdly,the switched nonlinear systems are used to describe the inspection robot dynamic model.The trajectory tracking control method of the known switched system is studied by backstepping control method,and the closed-loop stability condition is analyzed by using the common Lyapunov function.The modeling uncertainties and unknown external disturbances in the switched system can be accurately estimated by the Nussbaum disturbance observer.The performances of the nonlinear disturbance observer and the disturbance observer based on Super-twisting algorithm are compared with the Nussbaum disturbance respectively.The stability of the closed-loop system is proved by the average dwell time method.Simulation results illustrate that the proposed control scheme can guarantee the satisfactory tracking performance of the attitude motion for the inspection robot under the external unknown disturbance.Subsequently,a switched motion control scheme is proposed for the inspection robot system with the external disturbance and the input constraints.A hyperbolic tangent function is used to transform the original robot system into an equivalent form in order to solve the problem of input constraints,and a new subsystem is added in the last step of the conventional backstepping control to design an effective control scheme,the external disturbance and the system uncertainty are efficiently tackled using a Nussbaum disturbance observer.Finally,the stability of the closed-loop system is proved by the Lyapunov method,simulation results illustrate that the proposed control scheme can achieve satisfactory tracking performance.Finally,the motion control experiment of the robot has been carried out on the plane and inclined plane,including rigid switch adsorption strategy experiment and flexible switch adsorption strategy experiment,which verifies the reliability and stability of the robot switch system.