Development Of3D Elliptical Vibration Assisted Cutting Appratus And Its Control

Three-dimensional elliptical vibration assisted cutting (EVAC) is a very potentialprocessing methods, not only be verified to improving material machinability,but alsocan formed into a surface by micromachining movement,and then,3D EVAC gets highconcerned by academic and engineering all of the world.The ability to obtain the bestperformance of3D EVAC in actual processing based on the develop of3D EVACappratus and its control.State-of-the-art,there are still some issues of the previous studiesin3D EVAC appratus and its control to be resolved by studies,such as the controllabilityof three-dimensional elliptical trajectory,the nonlinear motion of three-dimensionalelliptical trajectory,and so on.This dissertation will focus on the problem of these twoaspects in-depth study.This dissertation detailed reviews the research status of three-dimensional EVACappratus and its control method. On this basis, the design of three-dimensional EVACappratus,the identification method of three-dimensional EVAC system and the controlmethod for three-dimensional EVAC appratus was studied,and the theories were verifiedthrough offline experimental testing,cutting experiments,theoretical analysis andsimulation.This dissertation contains the following five parts.(1) Designed a three-dimensional EVAC appratus based on parallel driver the parallelflexible hingeAimed to solve the current problems existing in3D EVAC appratus,developed athree-dimensional EVAC appratus to meet the requirements.The developedthree-dimensional EVAC appratus uses four piezoelectric actuators place parallelly andsymmetrically.The knife block in the appratus and the flexible hinges integratedprocessing to reduce the errors caused assembly,the appratus has a wedge-block designto fine-tune the height of the diamond tool.According to the movement of thepiezoelectric actuators configuration,the appratus can achieve cutting experiment bycommon turning, two-dimensional and three-dimensional elliptical vibration assisted turning. This dissertation calculate the stiffness of the flexible hinge portion in thedeveloped appratus and the finite element analysis of key components.Modeling theknife sites trajectory by simplify the designed appratus and simulation analysis theaffecting of the trajectory parameters on the trajectory shape, and generate athree-dimensional elliptical trajectory by adjusting the parameters of the trajectoryparameters to meet the processing requirements.(2) Carried ou the performance test of the developed3D EVAC apparatusThis dissertation carried out the performance test of the developed3D EVACapparatus to enable it to meet requirements of the precision ultra-precision machining.The test content includes the static stiffness test, the test of natural frequency,the testingof step response and sinusoidal response, the test of resolution testing and maximumstroke and the test of crosstalk.The test results of the Static stiffness is close to the designvalue and the simulation results,the test Results of natural frequency is not very differentfrom the simulated values,basically meet the requirements of this experiment. The stepresponse and sinusoidal response testing of the developed appratus can be seen that thedriving motion error of the piezoelectric stack satisfies the design requirements.Theresults of the resolution test can be seen that the resolution of the developed appratus is100nm or less.The maximum stroke test reaults of the developed appratus can be seenthat the maximum stroke can be achieved as13.97μm, the crosstalk test between thepiezoelectric stacks was carried out finally.The overall performance of the designedthree-dimensional EVAC appratus have a comprehensive grasp by the performancetest,can be targeted the subsequent control process.(3) Proposed a system identification method for three-dimensional EVAC appratus basedon nonlinear Wiener system.This dissertation described the developed three-dimensional EVAC appratus systemusing a nonlinear Wiener system due to the nonlinear hysteresis characteristics of thepiezoelectric actuators, and proposed a targeted identification strategy,researchidentification of the system, improved the memetic algorithm.This paper improvedmemetic algorithm framework global search strategy chosen is genetic particle swarm optimization algorithm,the local refinement strategy uses a only perception mode ofparticle swarm algorithm.So that not only the local convergence problems ofconventional algorithms can be solved,but also improve the chances of search efficiencyand success.The improved algorithm was tested through two commonly used algorithmstest functions,the test results were compared with GA, CMA and PSO,verified thesuperiority of the improved algorithm. This dissertation proposed a system identifierbased on the improved memetic algorithm and carried ou the system identification of thedeveloped three-dimensional EVAC appratus.The data for identification was collectedby experimental,the signals for identification selected as sinusoidal signal and the squarewave signal.The fit of the system identification result can be up to97.55%.(4) Proposed a adaptive fuzzy sliding control method for three-dimensional EVACappratusA fuzzy adaptive sliding mode controller was proposed to control the developedthree-dimensional EVAC appratus according to the nonlinear characteristics of theEVAC system. The control law of sliding mode was designed through the results ofsystem identification,and system stability was proved by Lyapunov law,finally thesimulation of fuzzy adaptive sliding mode controller was carried out.The simulationresults shows that the fuzzy adaptive sliding mode controller can effectively suppresschattering problem, which has strong robustness.(5) Carried out the processing experiments by the developed three-dimensional EVACappratusThis dissertation carried out the processing experiments by the developedthree-dimensional EVAC appratus.Firstly, introduced the experimental conditions of thecutting experiment.Synthesis three-dimensional elliptic trajectory through the parametersetting of three-dimensional elliptical trajectory,also to verify the theoretical ofmodeling knife sites modeling in the chapter2.The cutting experiments results of by thedeveloped three-dimensional EVAC appratus were comparison with the conventionalcutting and two-dimensional EVAC of YOZ plane.The photo of machined parts weregiven firstly,then described the advantages of three-dimensional EVAC by cut traces,surface roughness and tool wear,also authentication the theoretical research in thefront.