Research On Normal Vibration Of Electromechanical-Coupling Permanent Magnet Linear Feed System In High-Precision Cnc Machine Tool

The accuracy of high-precision CNC machine tools has been developed to the stage of nanometer, and the permanent magnet linear feed system is one of the core components of the direct driven high-precision and high-speed CNC machine tools. The vibration of feed system cannot be ignored and avoided. To comprehensively improve the performance of linear feed system, kinematics, dynamics, mechanics, electric and other aspects must be integratedly designed in permanent magnet linear feed system. In this dissertation, normal vibration of permanent magnet linear feed system due to the normal force acting on the motors was studied. Thereinto, the electromagnetic vibration source, system dynamics and damping optimization design were focused on.The root cause of vibration of permanent magnet linear servo motor is the normal magnetic forces ripples. The space-time distribution of normal force in PMLSM with different poles/slots number has been calculated with analytical method as well as finite element method (FEM), and the influence regularity of the normal-force distribution on the mover vibration was further analyzed. The results indicate that when the poles and slots have a common divisor equal to one or two, the resonance is liable to produce.For analyzing the vibration characteristics of linear feed system, the mathematical model for magnetic-structure coupling system was established. Through the indirect coupling calculation on the equation for magnetic-structure coupling field, the coupling-dynamics differential equation for the electromechanical system can be solved. The dynamic characters of worktable system were analyzed supposing the mover of the linear motor and worktable be an integral structure. Under the action of the normal force, the integral structure of worktable system has larger deformation and lower natural frequency than one single motor mover. The modal analysis of linear feed system showed that the workbench is the weak component of the system. Considering the fact that the vibration characteristics of high-precision CNC machine tools is susceptible to the mechanical components of elastic deformation, linear feed table was taken as equivalence to multi-degree-of-freedom spring-damper system based on global coupling view of the electromechanical system. Then the table was flexible by FEM firstly, and dynamics differential equation for the electromechanical coupling system was further deduced and estabished with the Lagrangian-Maxwell equation. Combined with FEM software of ANSYS and dynamic simulation software of ADAMS, the simulation model for the linear feed system was established. The comparative analysis indicates that the flexibility of structure, electrical control parameters and disturbance frequency all have obvious influence on the vibrations of coupling system. The acceleration from the experimental measurements agrees well with the simulation results.To improve the stiffness of linear feed system, the structure were designed and reconstructed by magnetic-structure coupling topology optimization method, and the adjoint method was used to calculate the sensitivity of structure response. Aiming to minimize flexibility and maximize the natural frequency, the structural topology optimization on mover, worktable and bed were conducted. Compared with the original structure, the optimized results showed that the static and dynamic stiffness of system were effectively improved under the premise of not influence the magnetic field distribution. Magnetic-structure coupling topology optimization provides an effective method for innovative design of coupled system.The normal force and the vibration for the prototype of permanent magnet linear servo motor have been tested. And the normal force of the prototype between two polars was measured through designing special testing apparatus. The accelerations of the worktable in the linear feed system with different speeds, loads, and profiles were measured, and then the modal frequencies were analyzed. The experiment results have proved that the coupling model is reasonable and correct.