Research On Trajectory Tracking Control Of Four-DOF High-speed Parallel Manipulator

At present,with development of the computer,communication and consumer electronic manufacturing,4-DOF parallel manipulator with pick-and-place capability play a vital role in those manufacturing.Not only precision of the core parts lower then foreign,but also tracking performance of the main controller is worse than foreign.So,designing a high-precision controller with simple structure and strong robustness becomes the key way to break foreign monopolies in robotic manufacturing.For this paper,as research object,the 4-DOF parallel manipulator was introduced,then its kinematic and dynamic model are built.Critically,modified bat algorithm based optimal fuzzy super-twisting sliding mode control algorithm was designed according to the dynamic model,and the main processes are as follow:In terms of robot kinematics and dynamics,firstly,the structure of manipulator was introduced.Then,the inverse kinematic model of manipulator was built according to the closed-loop-equation.Before the dynamic analysis,jacobian matrices were derived by Differentiating the closed-loop-equation with respect time.Subsequently,based virtual work principle,the dynamic model of parallel was built.At last,the kinematic and dynamic model were validated by simulation.As a supplement,dynamic parameters of parallel manipulator were identified by recursive least squares method.In the control algorithm design,as a comparison,computed torque controller was designed firstly.And a traditional first order sliding mode algorithm,whose stability was demonstrated by Lyapunov function,was designed as a main controller for parallel manipulator.Then,computed torque controller and first order sliding mode controller were simulated in Matlab/Simulink.In order to fix the issue of chattering of sliding mode controller,super-twisting sliding control algorithm was adopted to improve the continuity of switching function of sliding mode control.Beside,two fuzzy controllers,which can adjusting the gain of switching function and slope of the sliding surface,were designed to improve the robustness under un-modeled uncertainty and external disturbance.Subsequently,the simulation was done,which validate the effectiveness of the fuzzy super-twisting sliding mode controller.Generally,bottom widths of degree of membership function,chosen according to experience of control technician,are not optimal parameters.To fix this issue,Lévy flight based bat algorithm was introduced to optimize those bottom widths.After simulation.Compared with computed torque controller and first order sliding controller,lower tracking error,stronger robustness and less disturbance were obtained by using modified bat algorithm based optimal fuzzy super-twisting sliding controller.