Modal Analysis And Research Of Visual Positioning And Punching Control For Micro Punching System

The forming technique of micro punching has a great application prospect in thefield of micro parts manufacturing, such as electronic manufacturing and bio-medicaltreatment. In order to enhance the competitiveness of products, the manufacturingmethod and technique of the micro parts must be of high efficiency and low cost. It is ofgreat importance to carry out the research aiming at improving the manufacturingaccuracy and production efficiency.Based on the 863 project"Micro Parts Batch Manufacturing System Based OnMicro Plastic Forming", modal tests, researches on the visual positioning and thecontrol of linear motor are conducted in this paper after a development situationintroduction of systems with micro punching technique in and abroad.Firstly, modal tests are carried out HinH HconsiderationH HofH the calculated results ofANSYS. Different exciting and response methods are adopted in the tests usinghammering method according to the signal strength of different modal vibration modes.Actual low order frequencies of the system are attained through the selection of the testsresults with the help of the calculated modal data.Secondly, in order to decrease the positioning error of the HtranslationH directionscaused by feeding stepper motors, a visual positioning system and a positioningmethodology are designed and analyzed. A positioning hold is chosen as the detectingtarget. The complex threshold value determining process using one-dimensional grayhistogram in the image segmentations are avoided through a two-dimensional grayhistogram method. After the thinning process of the detected edges of positioning holesby four different edge detection operators, the best operator and the best threshold valueare determined. A Hough and least-square circle detecting method is proposed, whichhas a better robustness than the traditional Hough method shown in simulations. Theexperiments indicate the maximum error between positioning hole and the datum is nomore than 3.5μm.Finally, in order to improve the control performances of the linear motor with shortstrokes, a sliding mode variable structure control (SMC) method is studied against thedefects of PI control in the speed loop. The SMC controller is designed with statevariables of velocity difference and its derivative. Disturbances are compensated by aRomberg observer. The realizing method of this controller in the SIEMENS system isexplored after the validity is proved by the simulations. The controller is then integratedin the speed loop of the SIEMENS system through the Drive Control Chart (DCC)programming. After adjustments of controller's parameters during the experiments, theSMC controller with the Romberg observer realizes the response of near step velocity signal without overshoot and low steady-state error. The transient time is remarkably short compared with that under PI control.