Li Qingpin

Bio: Li Qingpin is an academic researcher. The author has contributed to research in topics: Isolator & Stewart platform. The author has an hindex of 3, co-authored 3 publications receiving 70 citations.

Quasi-zero stiffness vibration isolator with annular permanent magnets used for generating negative stiffness

Abstract: A quasi-zero stiffness vibration isolator with annular permanent magnets used for generating negative stiffness comprises a base and an outer cylinder connected with the base, the outer permanent magnet is arranged in a top notch of the outer cylinder, an upper cover is connected with the outer cylinder, a sliding bearing is combined with a central hole of the upper cover in a sleeved mode, and a central shaft is sleeved with the sliding bearing and is in clearance fit with the sliding bearing. A sleeve and an adjusting sleeve are sequentially connected to the position, located on the lower portion of the sliding bearing, of the central shaft, and the inner permanent magnet is installed in the sleeve. A spring is arranged at the bottom of the central shaft in a sleeving mode, the bottom end of the spring is fixed to the base, and the top end of the spring is fixed to the adjusting sleeve. A mark line on the central shaft is used for representing the position of the inner permanent magnet relative to the outer permanent magnet. When the mark line coincides with the upper end face of the sliding bearing, the inner permanent magnet exactly faces the outer permanent magnet, and the isolator is in a normal working state. The quasi-zero stiffness vibration isolator has the advantages of being high in static stiffness and low in dynamic stiffness, basic stimulation with large amplitude can be isolated, and the mass of a vibration-isolated objected can be adjusted.

Six-degree-of-freedom quasi-zero-rigidity vibration isolation system based on Stewart platform

Abstract: The invention provides a six-degree-of-freedom quasi-zero-rigidity vibration isolation system based on a Stewart platform. The system comprises an upper platform, a lower platform and six same landing legs fixed between the upper platform and the lower platform through hinge blocks. The three hinge blocks are distributed in an equilateral triangle mode, two corresponding landing legs are fixed to each hinge block, the adjacent landing legs are perpendicular, and the upper platform has six degrees of freedom relative to the lower platform. The six landing legs have the quasi-zero-rigidity characteristic, so that the vibration isolation system has the quasi-zero-rigidity characteristic on the six degrees of freedom, the all-order resonant frequency of the vibration isolation system is small, and the wide vibration isolation frequency range is achieved. The system has the advantages of being high in bearing capacity and low in resonant frequency, has the good restraint effect on low-frequency vibration, and is suitable for vibration isolation of flywheel systems and optical cameras in the spaceflight field and vibration isolation of equipment such as precision machine tools and precision measuring systems in the civil field.

Nonlinear vibration of a slightly curved beam with quasi-zero-stiffness isolators

Abstract: Bending vibration of isolated structures has always been neglected when the vibration isolation was studied. Isolated structures have usually been treated as discrete systems. In this study, dynamics of a slightly curved beam supported by quasi-zero-stiffness systems are firstly presented. In order to achieve quasi-zero-stiffness, a nonlinear isolation system is implemented via three linear springs. A nonlinear dynamic model of the slightly curved beam with nonlinear isolations is established. It includes square nonlinearity, cubic nonlinearity, and nonlinear boundaries. Then, the mode functions and the frequencies of the curved beam with elastic boundaries are derived. The schemes of the finite difference method (FDM) and the Galerkin truncation method (GTM) are, respectively, proposed to obtain nonlinear responses of the curved beam with nonlinear boundaries. Numerical results demonstrate that both the GTM and the FDM yield accurate solutions for the nonlinear dynamics of curved structures with nonsimple boundaries. The multi-mode resonance characteristics of the curved beam affect the vibration isolation efficiency. The quasi-zero-stiffness isolators reduce the transmissibility of modal resonances and provide a promising future for isolating the bending vibration of the flexible structure. However, the initial curvature significantly increases the resonant frequency of the flexible structure, and thus the frequency range of the effective vibration isolation is narrower. Furthermore, the quadratic nonlinear terms in the curved beam make the dynamic phenomenon more complicated. Therefore, it is more challenging and necessary to investigate the isolation of the bending vibration of the initial curved structure.