Vibration Response Analysis And Fatigue Life Estimation For Drive Components Of 2(3HUS+S) Parallel Hip Joint Simulator

Parallel mechanism has advantages of good dynamic property and high positioning precision compared to the traditional series mechanism.The parallel mechanism is introduced into parallel hip joint simulator thanks to the advantages above.Some vibration will be produced during the operation,which will bring some deviation to the motion trajectory simulated by the experimental device,the deviation will influence the accuracy of the test results.Therefore,the vibration characteristics of parallel mechanism needed to be analyzed.In order to meet the test requirements better,the fatigue life of the device needed to be estimated.The research and analysis about stiffness,vibration model,vibration response and fatigue life of the drive components of a new type 2(3HUS+S)parallel hip joint simulator(referred to parallel hip joint simulator)had carried on.The main research contents could be summarized as follows:1)The study of modeling method for the deformation and stiffness of drive component system: The stiffness of system was decomposed into stiffness of ball screw,stiffness of ball screw pair and stiffness of supporting bearings.Stiffness of each part needed to be calculated respectively,then stiffness of whole system could be gotten.For stiffness of ball screw,the stiffness of ball screw was described by the theory of material theory according to the relationship between stiffness of ball screw and motion position of sliding blocks of ball screw rods.For stiffness of ball screw pair,firstly,the force on a single ball under the action of motor drove moment was obtained,and the deformation of a single ball was obtained based on Hertz contact theory,then the stiffness of ball screw pair could be gotten utilizing MATLAB.For stiffness of supporting bearings,firstly,the stress distribution of support bearings was analyzed,and the deformation of inside circle and outside circle could be gotten by Hertz contact theory,then the stiffness of supporting bearings could be calculated by MATLAB.The total stiffness were calculated according to the stiffness of each part.2)The study for vibration model establishment of drive component system: In this chapter,a hybrid method was utilized to establish the vibration model and simplify drive components.The drive component system was divided into supporting bearings,ball screw pair and ball screw,then the vibration model diagram of drive component system was drawn.The vibration model of drive components was divided into axial vibration model and torsional vibration model respectively.The kinetic energy,potential energy and dissipation energy expressions of axial vibration modeland torsional vibration model were written by Lagrange equation,then,the whole vibration differential equation was written.At last,a suitable hybrid basis function was selected to calculate first six natural frequencies of the axial vibration model and the torsional model.The general law of the result could be obtained.3)The study for analysis method for vibration response of drive component system: Firstly,a suitable dynamic analysis method was selected to analyze,then,Solidworks was used to establish the drive component system model of 2(3HUS+S)parallel hip joint simulator.The model was imported into Adams software,material attributes was defined according to the actual working environment,work constraints and kinematic condition for dynamic simulation were added.After dynamic simulation,the contact force on single ball could be obtained.The models which had maximum axial force were imported into workbench,material properties were added,the appropriate grid division method was selected,the grids in some regions were subdivided,and the main contacts were defined.After the definition,the vibration of drive components could be observed.the integration of ball screw pair was simplified,the contact force on single ball obtained from the dynamic analysis was imported into the model,then the vibration acceleration response from three points of nuts could be gotten.4)The study for fatigue life estimation of drive part system: Experiment system was established to measure the experimental data of moment of drive motors in linear modules,and the experimental data was compared with theoretical data.The random load conditions on equipment were established and the poisson stochastic process model was established based on nonhomogeneous poisson stochastic process theory.The model parameters of nonhomogeneous poisson stochastic process theory were estimated by neural network.The adjoint strength damage theory proposed worked out the problem that the fatigue life estimation was inaccurate due to the interaction between loads,then the rationality of the theory was verified by the eight-stage random loading test.The stress condition of the ball screw pair could be found out by Hertz contact theory,then the stress was deal with through the theory above,finally,the fatigue life of drive component system was estimated.