Research On Thrust Ripple Characteristics Of Ironless Tubular Permanent Magnet Synchronous Linear Motor

Due to the linear motor can directly output rectilinear motion,so it has excellent positioning performance,but the thrust ripple can cause undesirable vibration and noise.The ironless tubular permanent magnet synchronous linear motor(ITPMSLM)has no positioning force due to its structural characteristics,but thrust ripple and external friction will also affect the thrust ripple.In order to achieve the purpose of reducing thrust ripple,this thesis puts forward a new structure of Halbach magnetized ITPMSLM,launched a series of studies on it.Based on the comparison of different magnetizing methods of permanent magnets,the magnetic field solving model of Halbach magnetized ITPMSLM based on equivalent magnetization intensity method is established,and the analytical expression of excitation field is deduced.The effects of different parameters of permanent magnets on the air gap magnetic field are studied,the results show that the ratio of axial length of axially magnetized permanent magnet to axial length of radially magnetized permanent magnet has the biggest influence,the influence of permanent magnet thickness is the least,and the influence of air gap length is in the middle,and the size parameters of the permanent magnet are determined.A single layer non-stack winding is used as the winding structure of Halbach magnetized ITPMSLM,according to Faraday’s law of electromagnetic induction and ampere’s law is deduced respectively the analytical expression of the electric back emf and electric motor thrust.The influence of different parameters of the winding on the back emf and thrust is studied,the consequence indicate that the thickness of the winding has little influence,and the axial width of the winding has a great influence,and the size parameters of the motor winding are determined.It is revealed that the internal factor of thrust ripple of Halbach magnetized ITPMSLM is ripple thrust caused by air gap magnetic field waveform aberration,and the external factor is friction resistance caused by the friction between the motor and the guide rail when the motor is moving.The method of changing the structure shape of the permanent magnet and using the motion scheme of the air floating guide rail to suppress the thrust ripple is proposed.According to the thrust ripple led to internal cause,this thesis proposes a chamfered permanent magnet structure.Ansys Maxwell simulation software was used to optimize the size of the chamfered permanent magnet,so that its air gap magnetic field waveform reached the best sinusoidal.The magnetic field,back emf and thrust of the chamfered permanent magnet and the rectangular permanent magnet Halbach magnetized ITPMSLM are compared and analyzed.The consequence indicate that the character of the chamfered permanent magnet is better than that of the rectangular permanent magnet.According to the external cause of thrust ripple caused by frictional resistance,a motion scheme of air floating guide is proposed,and its structure is designed to eliminate the friction effect in the process of motor mo vement.The basic structure and size parameters of Halbach magnetized ITPMSLM prototype are determined,and the stator was machined and assembled and the actuator is wound and sealed.The air floating guide rail assembly is processed and manufactured,the air floating table is built and debugged to check the strength of relevant key components,and the overall motor system is run and debugged,and the development of Halbach magnetized ITPMSLM prototype is completed.The principle and scheme of Halbach magnetized ITPMSLM back emf repeated positioning accuracy and thrust fluctuation experimental test are designed.The corresponding experimental test results show that the error between the measured back emf constant and the simulation value is very small,which indicates that the distribution of air gap magnetic field waveform has good sinusoidal properties.The experiment measured that the repeated positioning accuracy of the motor under different motion stroke is in the sub-micron scale,which indicates that the positioning performance of the motor is excellent.The thrust volatility measured by the experiment is in good agreement with that of the simulation analysis,which indicates that the Halbach magnetized ITPMSLM can suppress the thrust ripple of the motor.To sum up,this thesis focuses on reducing the thrust ripple of Halbach magnetized ITPMSLM,analyzes the magnetic field,back emf and thrust of the motor,and gets the optimal size range of the motor.The internal and external factors affecting the thrust ripple are analyzed,and a prototype is developed for experimental research.The rationality of Halbach magnetized ITPMSLM structure is verified,which can effectively suppress the influence of thrust ripple,improve the positioning performance of precision machining equipment,and provide a new guidance for the design of motor.