Design And Analysis Of A Double-sided Moving-magnet Multi-air-gap Permanent Magnet Linear Synchronous Motor For Electromagnetic Launching

With the improvement of the national defense level and the development of military science and technology in various countries,the requirements for the take-off performance of modern military aircraft are constantly increasing,which has a higher requirement for the take-off devices on the aircraft carrier.Nowadays the electromagnetic launching(EML)is the most effective take-off auxiliary device,its main body is the combination of many large-power linear motors.However,the disadvantages of the linear motors are lower thrust density,higher quality of mover,greater normal force,poorer safety and higher cost,that constrain the efficiency of the EML and greatly promote the technological revolution and development of the linear motors.Based on the performance requirements of the EML for high electromagnetic thrust,low thrust ripple,low normal force and high operating speed,a double-sided moving-magnet multi-air-gap permanent magnet linear synchronous motor(DSMMMA-PMLSM)is designed.The motor combines the advantages of the permanent magnet linear synchronous motor(PMLSM)and the double-sided moving-magnet mover structure.It is very suitable for the EML for its high thrust density,high power factor,light mover quality,sturdy structure and favorable for subsection power supply and control.After combining the design method and experience of the permanent magnet synchronous rotary motor and the linear induction motor,the electromagnetic design scheme of the DSMMMA-PMLSM was programmed.Firstly,according to the rated parameters requirements of the EML,the main dimensions and the electromagnetic load of the motor were determined and the main structural parameters including the slot dimensions,winding distribution and connection mode of the stator and the permanent magnet dimensions of the mover were selected.Then the magnetic circuit calculation,the parameter calculations and the operation characteristic calculations were carried out,and the electromagnetic design scheme of the motor which met the requirements of the EML was obtained.The electromagnetic design scheme has improved and perfected the design method of PMLSM and has certain guiding significance in engineering.The thrust characteristic is an important index to measure the performance of PMLSM.Considering the special end effect of the linear motor and the influence of the magnetic field harmonics on the armature flux,the mathematical model of the asymmetric d-q coordinate system under vector control was set up,and the electromagnetic thrust of DSMMMA-PMLSM was derived.On this basis,the mechanism of the electromagnetic thrust ripple was analyzed,the main reasons of the thrust ripple were pointed out,and the effective measures to weaken the harmonic component in the linear motor and to improve and restrain the thrust ripple of the linear motor were put forward.In order to verify the accuracy of the mathematical model,a two-dimensional analytical model of a linear motor with multi-layer air-gap was established by using the analytic hierarchy process of magnetic field,and the distribution of magnetic field and the characteristics of the electromagnetic thrust were obtained.The two methods have their own advantages and disadvantages.Different methods can be adopted in different analysis strategies to meet different analysis needs and computing environments.During the operation of PMLSM,the normal force perpendicular to the electromagnetic thrust direction is very high,which will reduce the efficiency and reliability of the motor.After the detailed description of the mechanism of the normal force and its ripple,the whole motor model was divided into two air-gap magnetic field models of the stator and the auxiliary stator according to the special structure of DSMMMA-PMLSM.The normal force between the stator and the mover,the mover and the auxiliary stator were analyzed,and the normal force value of one single side of the motor was calculated by superposition method.Then the relationship between the structural parameters of DSMMMA-PMLSM and the normal force was summarized,and the difference of the influence degree of each parameter on the normal force was further obtained.The finite element method was used to simulate the PMLSM with different mover structures,compared with the simulation results under normal steady-state operation and eccentric operation of the mover,the DSMMMA-PMLSM had obvious advantages.The operating characteristics of the motor in the entire starting process was obtained by the transient simulation of the DSMMMA-PMLSM,and the strength of the mover in the extreme environment was analyzed and checked.Combined with the structural parameters obtained by electromagnetic design,a prototype was designed and manufactured,an experimental platform for the motor system was set up,and a relevant electromagnetic thrust test was performed to verify the rationality of the DSMMMA-PMLSM and the accuracy of the calculation of the various analytical methods.