Research On Intelligent Control Technologies For V Shaped Free Bending Of Sheet Metal

As a branch of plastic working field, sheet metal forming possesses an important place in the industry field of automobile, aviation, instrument and so on. Its state of the art reflects industrial modernization level of a country or region in some degree. Due to lack of the skill in real-time monitoring, identifying and predicting, the automation of sheet metal forming can only finish forming process in the light of pre-established work program and process parameters. When material quality and operating condition of manufactured object change or fluctuate, process parameters can't be automatically regulated. The intellectualization of sheet metal forming, which includes 4 basic elements, real-time monitoring, identification, prediction and control, is the crossing subject of control-science and sheet metal forming theory. According to the characteristics of the initial piece, utilizing physical quantities easy to be measured, material properties and friction coefficient can be determined in real-time, and then the forming process can be completed automatically with the optimal processing parameters. As a result, the intellectualization of sheet metal forming process is the higher level of new technologies such as press forming automation and flexible process system, by which not only can the feature of manufacturing technique be changed, but also the transformation of press equipment can be forwarded. It brings about the progress of sheet metal forming theory and improvement of analysis precision at the same time. it has the important significance for degrading sheet metal level, eliminating technology difficulty between die and equipment adjustment, shortening die setting time, improving productivity and the rate of finished products, and so on. Bending forming is very widely applied in engineering practice, so it has much academic value and significance to study intelligent control technology of bending forming of sheet metal. Based on the research achievements of intelligent control of deep drawing, the key technologies of intelligent bending are analyzed, and the relevant issues to the theoretic analysis, the identification of parameters, the predication of optimal technological parameter and the establish of control system is studied in this paper. Among the four basic elements required by intelligent bending of sheet metal, the establishment of the identification model of parameters and the prediction model of optimal technological parameter is dependent upon the level of understanding the forming law for bending. Based on sheet metal plastic forming theory, the stress/strain distribution law is studied and elastic deformation of sheet metal is taken into account according to bending forming characteristics. The calculating formula of springback angle is deduced based on springback theory, which provides a fundamental theoretic basis for real-time identifying and predicting material parameters in the process of bending intelligent control. Moreover, the control strategies of spring-back and thickness reduction are discussed, as well as, the slip-line field method solving stress/strain of the forming area is presented. The dominant factors influenced on V bending forming have been analyzed by using theoretic analysis and finite element method (FEM) simulation, and then the identification model of parameters and the prediction model of optimal technological parameter are determined. The Levenberg-Marquarat is chosen as optimal algorithm of neural network whose topology structure is feedforward network, and Matlab language is to program. For the problem of sample data acquisition, the feasibility has been studied that FEM replaces some experiments to get sample data, by which the sum-squared error is stepped downward to 1‰. Furthermore, the influence of sample data and hidden nodes on network convergence efficiency, precision as well as generalization has been studied, by which the sum-squared error is stepped downward to 1‰. A portable DAQ system is established by applying virtual instrument control software...