Abstract:The working environment of the laser transmission channel is complicated.In order to meet the requirements of system sealing,this paper designs a magnetic fluid dynamic sealing structure.It is mainly composed of magnetic fluid,pole shoe,permanent magnet,inner tube,outer tube and cover plate.The magnetic field simulation model was established,and the size and distribution of the magnetic field in different sealing gaps are calculated.The theoretical pressure resistance capacity under the gap of 0.1~0.4mm was analyzed,and the sealing gap of 0.2mm was selected according to engineering requirements.The theoretical calculation showed that the withstand pressure can reach 0.26 MPa.The Block Lanczos method was applied to the modal analysis of the inner cylinder.The first order natural frequency is 690.94 Hz,which is much higher than the natural frequency of the theodolite and meets the dynamics requirements.Finally,experiments were carried out and the influence of centrifugal force on the seal is analyzed.The results show that all the indicators of the sealing structure meet the requirements.