Intelligent Non-singular Fast Terminal Sliding Mode Synchronous Control For Direct-drive H-type Platform

Direct-drive H-type platform consists of three Permanent Magnet Linear Synchronous Motors(PMLSMs).PMLSMs are susceptible to uncertainties such as end effect,external disturbances and nonlinear friction,which causes large position tracking error in each single axis of the direct drive H-type platform,and the mechanical coupling causes the synchronization accuracy of the Y-axis dual-axis servo system to decrease.The research purpose of this study is to reduce the position tracking error of the single-axis of the direct drive H-type platform and improve the synchronization control accuracy between the two-axis linear motors.First of all,the development status,research status,and main control strategies of the direct drive H-type platform are introduced.Based on the basic principles of PMLSM,a mathematical model of a direct-drive H-type platform is established,which includes uncertainties such as thrust ripple,external disturbances and mechanical coupling.Secondly,a non-singular fast terminal sliding mode synchronization control is proposed for the reduction of the tracking errors and synchronization error of the direct-drive H-type platform system that affected by thrust ripple,external disturbances and mechanical coupling.The cross-coupling control is used to combine the single-axis tracking errors and the synchronization error to obtain hybrid error,and hybrid error is used as the control state variable,which weakens the coupling effect between the dual linear motors to improve the accuracy of the two-axis synchronization of the platform.The stability of the designed control system is proved using Lyapunov theorem.Then,an intelligent non-singular fast terminal sliding mode synchronization control method is proposed to further reduce the single-axis position tracking error and dual-axis synchronization error of the direct drive H-type platform,and improve the system’s robustness to uncertainties.The RBF neural network is used to estimate the uncertainties of the servo system online,and it is compensated as a feedforward signal to the dual linear motor servo system.At the same time,design the reaching law with attenuation factor to weaken the chattering of the system.Lyapunov theorem is used to prove that intelligent non-singular fast terminal sliding mode control can make the tracking error and synchronization error of the system converge and ensure the stability of the system.Finanlly,the simulation models of direct-drive H-type platform servo system based on traditional sliding mode control,non-singular fast terminal sliding mode control and intelligent non-singular fast terminal sliding mode control are established,and the simulation comparison analysis was performed.Simulation results show that the control system based on intelligent non-singular fast terminal sliding mode has the advantages of smaller single-axis position tracking error,higher accuracy of two-axis synchronous control,stronger robustness,and smaller chattering compared with the other two control strategies.