Study On Sliding Mode Control Of 6-DOF Wire-driving Parallel Robot

Wire-driven parallel robot is a new type of wind tunnel test supporting system.This system has drawn much attention because it has the following advantages:large working space,small interference to the flow field of the aircraft model,and strong model stiffness.In this paper,based on the application of wire-driven parallel mechanism in wind tunnel,kinematics and dynamics analysis is studied deeply.Considering the influence of different factors on the control accuracy,the control scheme is designed separately.Stability analysis and simulation verification are performed.The main contributions are described as below:Firstly,the kinematics and dynamics analysis of wire-driven parallel robot is carried out.The relationship between the wire length and the attitude of the aircraft model is obtained by the inverse kinematics analysis.The dynamic model of the whole system is obtained based on the dynamic model of the driving system and the dynamic model of the aircraft.Based on the kinematics model,the visual servoing method is applied to wire-driven parallel robot.The posture of the model is measured by a vision system,and a new control law is designed to perform an exponential decay of the tracking error.The method is simulated and verified by experiments.Secondly,a sliding mode controller is designed for wire-driven parallel robot,and a SIMULINK simulation block diagram of the system is set up.For comparison analysis,the feasibility of the non-singular terminal sliding mode control and the continuous non-singular terminal sliding mode control in wire-driven parallel robot are studied respectively.A continuous non-singular terminal sliding mode controller,based on torque control,is selected.The different motion cases are taken as examples,the motion control simulation analysis is performed.In addition,the influence of sliding mode controller parameters on the dynamic performance of the system is analyzed.Thirdly,considering the effect of aerodynamics and elastic elements,the external disturbances and uncertainties in the low-speed wind tunnel test of wire-driven parallel robot are studied.In the control law,the aerodynamic force is compensated adaptively.An adaptive terminal sliding mode controller is designed.The pitch motion is taken as an example for simulation.Considering the effect of wire elastic elements on the control of aircraft model,based on the singular perturbation theory,the system dynamics model is reconstructed.A controller for compensating the elastic elements of the wire is designed and the motion control simulation is performed.Finally,in order to achieve the hybrid pose-force control of the wire-driven parallel robot,the penalty function method is chosen to calculate the optimal distribution of the wire tension.Using the pitching motion as an example,three optimization target methods are analyzed,and the method of optimizing the tension variance is finally selected.Based on the sliding mode control and the optimal distribution method of the wire tension,the force control scheme of wire-driven parallel robot is designed.The pitch motion is used as an example to carry out the control simulation,and the curves of torque and tension are obtained.The research in this paper realizes the kinematics,dynamics and hybrid force-position control simulation analysis of wire-driven parallel robot,which lays a solid foundation for the further development and application of the wire-driven parallel robot.