Research On Permanent Magent Negative Stiffness Technology For Large Vibration Isolation

In order to reduce the impact of low-frequency micro amplitude vibration in the environment on large ultra precision machining equipment and measuring instruments,low frequency/ultra-low frequency vibration isolators with large bearing capacity and low natural frequency are highly needed.Aiming at the problem that large vibration isolation is usually difficult to take into account the large bearing capacity of the system and the low natural frequency of the system,this paper designs a permanent magnet array negative stiffness structure,which is used in parallel with the positive stiffness structure to reduce the natural frequency of the vibration isolation system and achieve the effect of ultra-low frequency vibration isolation.The theoretical analysis and optimization design of the permanent magnet structure with negative stiffness are carried out,the parallel vibration isolation scheme with positive and negative stiffness is designed,and the experimental device is built to test the performance of the vibration isolator to verify the feasibility of the proposed scheme.The main work of this paper is as follows:Firstly,the principle of parallel vibration isolation with positive and negative stiffness is analyzed.Using the parallel vibration isolation method with positive and negative stiffness can reduce the natural frequency of the system without changing the bearing capacity of the system.Based on the analysis and comparison of various permanent magnet negative stiffness structures,a scheme of permanent magnet negative stiffness structure for largescale vibration isolation is designed.The equivalent current model is used to model the axial magnetic force of the structure.The correctness of the modeling results is verified by the finite element simulation method.The deviation between the theoretical calculation results of axial magnetic force and the simulation results is less than 8.1%.Secondly,the negative stiffness characteristics and nonlinear stiffness characteristics of the structure in the axial direction are analyzed,and the influence law of geometric parameters of the negative stiffness structure on the stiffness characteristics is analyzed by using the control variables.Genetic algorithm was used to optimize structural parameters under constraint conditions.Compared with the traditional double magnetic ring negative stiffness structure,the negative stiffness amplitude of the designed structure can be increased by more than three times,which is more suitable for large-scale vibration isolation.Thirdly,the positive and negative stiffness parallel vibration isolation scheme for large-scale vibration isolation is designed.In theory,the natural frequency of the system can be reduced by 69.3% after the negative stiffness structure is paralleled.Then,the error factors of the structure are analyzed.The eccentricity error and inclination error of the magnetic ring have little influence on the axial stiffness characteristics of the structure,but the structure will produce a certain force in the horizontal direction.The magnet size error and permanent magnet magnetization error will have different degrees of influence on the structural stiffness characteristics.Finally,the hardware in the loop simulation model of the parallel vibration isolation system with positive and negative stiffness is designed to verify the feasibility of the negative stiffness structure of the permanent magnet array.The experimental results show that the natural frequency of the system decreases from 4.75 Hz to 1.25 Hz,and the stiffness of the negative stiffness structure at the static equilibrium point is-11.40N/mm,which is 9.3% different from the theoretical calculation.Compared with the ground vibration amplitude,the vibration velocity amplitude of the platform with parallel negative stiffness structure decrease by 51.9% respectively.