| To reduce the impact of vehicle vibration on the equipment in the movement and ensure the accuracy of the transported equipment,a multi-dimensional vibration isolation platform for the transported equipment is proposed and designed in this paper.Firstly,based on the characteristics of parallel mechanism with strong bearing capacity and multiple DOF(degree of freedom),a design scheme of multi-dimensional vibration isolation platform is proposed.According to the analysis of vehicle vibration directions,the vibration isolation dimensions of multi-dimensional vibration isolation platform are determined.The DOF of parallel mechanism is set as the same as the vibration isolation directions of the platform.According to screw theory,the branches satisfying the DOF of parallel mechanism are synthesized.The different kinds of branches are selected to meet the design requirements of isolation platform.The main structure of the vibration isolation platform is determined as cubic configuration of 6-SPS parallel mechanism.The dimension synthesis of parallel mechanism is completed.Secondly,based on the branch constraint method,the motion equations between the moving platform and branches of 6-SPS parallel mechanism are established.Based on the vibration space of multi-dimensional vibration isolation platform,the working performance of parallel mechanism is verified.The energy model of the 6-SPS parallel mechanism is established by the velocity and acceleration of each component which is calculated by direct differentiation of motion equations.According to Lagrange method,the dynamic equations of 6-SPS parallel mechanism are established.Thirdly,the P-joints and S-joints of the parallel mechanism are replaced by linear spring units and torsion spring units respectively to design the corresponding multidimensional vibration isolation platforms.According to the analysis of the bearing capacity,the stiffness ranges of the two kinds of spring units are calculated.Based on the principle of virtual work,the vibration response equations of the systems are established.To simplify the vibration response equations,the equations are decoupled by the vibration modal analysis method.Additionally,the influence curves between the stiffness and damping of spring units and the decoupled stiffness and damping of multi-dimensional vibration isolation platforms are analyzed.As a result,the optimal stiffness and damping are determined.Through the analysis of the road excitation,the vibrations of the platform suffered are determined.The vibration responses of the two kinds of isolation platforms in each vibration direction are calculated and compared.According to the results,when the S-joints of the 6-SPS parallel mechanism are replaced by torsion spring units in optimal stiffness and damping,the isolation platform has better performance.Fourthly,the torsion spring units of multi-dimensional vibration isolation platform are designed based on flexure hinge.Through the analysis of the flexure hinge deformation range,it is determined that the flexure hinge deformation is in the linear stiffness range.As a result,the torsion stiffness models of flexure hinges with different notches are established and analyzed based on mechanics of materials.In addition,the vibration modals of flexure hinges with different notches are analyzed by finite element method to confirm the equivalence of flexure hinge to S-joint spring damping.By analyzing the overall stress of flexure hinges with different notches,the stress concentration of different flexure hinges is studied.For the elliptical notch flexure hinge has the best stress performance,it is determined as the final form of torsion spring units.By comparing the stiffness of flexure hinges with different materials and shapes with the optimal stiffness of S-joint spring damping,the material and dimensional parameters of elliptical notch flexure hinge are determined.Finally,the structure of the multi-dimensional vibration isolation platform is designed and the bearing capacity of the multi-dimensional vibration isolation platform is simulated and checked according to the finite element analysis.The vibration response model of the vibration isolation platform is carried out by Adams and the physical model is built in the experiment.By analyzing and comparing the experimental results with the calculation results and simulation results,the vibration isolation effect of the multidimensional vibration isolation platform is confirmed and the correctness of the simulation model and numerical calculation results is verified. |
