Adaptive Fractional Sliding Mode Synchronous Control Of Direct Drive H-type Platform

The direct drive H-type motion platform is composed of a permanent magnet linear synchronous motor(PMLSM)in the X axis direction and two permanent magnet linear synchronous motors parallel to the Y axis,and the X axis and Y axis belong to Rigid connection.Because PMLSM is more sensitive to some uncertain factors,the single-axis PMLSM of the direct-drive H-type platform will produce tracking errors.In addition,the parallel axis is susceptible to mechanical coupling,parameter dynamic mismatch and other factors,which will cause the synchronization accuracy of the parallel axis to decrease.The research purpose of this paper: to solve the problem of non-synchronization of the servo system of the direct-drive H-type motion platform,and to ensure the single-axis accuracy and reduce the synchronization error of the parallel axis by designing an effective control strategy.Firstly,The basic structure and working principle of PMLSM are introduced in detail,and the mathematical model of PMLSM is established by coordinate transformation.According to the basic principle of PMLSM,a mathematical model of the direct drive H-type platform including parameter uncertainty,load disturbance and torsion force uncertainty is established.Secondly,a synchronization control strategy based on the combination of adaptive fast non-singular terminal sliding mode(AFNTSM)controllers is designed for the direct drive Htype motion platform servo system that is susceptible to parameter perturbation,load disturbance and mechanical coupling.Use cross-coupling structure design to correct the error between parallel shafts,and use the designed correction error as the single-axis control input.The single axis adopts FNTSMC to suppress the influence of uncertain factors,fast convergence while avoiding nonlinear sliding mode singularity problems,and speeds up the convergence rate when away from the equilibrium point.In order to eliminate the influence of external interference on the direct drive system,an adaptive control strategy is adopted to estimate the uncertain parameters and the limits of external interference in real time,which improves the synchronization accuracy and single-axis tracking accuracy of the direct drive H-shaped motion platform.Then,in order to further improve the dynamic quality of the direct drive servo system,obtain high-quality synchronization performance.A synchronization control strategy based on adaptive fractional order fast non-singular terminal sliding mode(FO-AFNTSM)is designed.Introducing the fractional order theory into sliding mode control,using the properties of the fractional saturation function of "large deviation and large gain,small deviation and small gain",it accelerates the approach speed and at the same time weakens the sliding mode chattering phenomenon,improves the system performance The dynamic quality reduces the synchronization error between parallel axes and the tracking error of a single axis.And use the Lyapunov stability proof to verify the progressive stability of the system.Finally,a direct-drive H-type synchronization controller based on fast non-singular terminal sliding mode synchronization controller,adaptive fast non-singular terminal sliding mode synchronization controller and different order adaptive fractional-order fast nonsingular terminal sliding mode synchronization controller are established respectively.Simulation model of the platform servo system and comparative analysis.The simulation results verify that the fractional-order control system based on the adaptive fractional-order fast non-singular terminal sliding mode is compared with the other two integer-order control systems.It reduces the single-axis position tracking error while improving the synchronization accuracy between parallel axes,and enhances system robustness.