Research On The Rule Of Springback And Intelligent Control Technologies For Multangular-Shape Single Bending

Sheet metal bending is widely used in the industry field of automobile, agriculture machine, aviation, instrument and so on. The most prominent problem in bending process of sheet metal is that it is difficult to control bending springback accurately, especially complex shape bending workpiece. There are many factors that effect the springback of bending, even if is the same trademark,batch plate, because the material performance and the craft condition undulation also can cause the springback comparatively big change. The current manufacturing industry market trend of development is to the high accuracy, the multi-varieties, the small batch bending workpiece demand increases day by day, but the difference between raw material cost and the final product price reduces gradually, and the competition in market change intensely day by day, so seeks a more effective method is needed to reduce the production cost and to enhance the productivity. Uses the intellectualization to realize the springback accurately controlled, is one effective way to solve above question.The intellectualization of sheet metal bending regards each blank as individual with different performance, identifies in real-time the performance parameter of each individual, consequently confirms the optimal craft parameter, and accomplishes the process of bending forming and unloading with the optimization craft parameter, accordingly achieves the high precision.Based on the research achievements of intelligent control of deep drawing and v bending, the key technologies of intelligent bending are analyzed, and the relevant issues to the theoretic analysis, the identification of parameters, the prediction 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 optical technological parameter is dependent upon the level of understanding the forming law for bending. Based on sheet metal plastic forming theory, according to the bending characteristic, has completed the thorough fundamental research to the U bending forming and the mechanism of springback, has established the U free bending model and cap-bending model which can describe precisely the forming of U bending, has obtained the influence rule of the geometry parameter and mechanics parameter to the bending springback, has provided the basic theory for the real-time identification and real-time prediction of bending intellectualized control.The dominant factors influenced on U bending forming and springback after unloading has been analyzed by using theoretic analysis,finite element method simulation and experiments, 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 feed forward network, and Matlab language has been used to compile the neural network arithmetic program. The network has been trained using the date sample obtained by experiments and numerical simulation. Convergence precision of the identification network reaches 1‰, and generalization precision of identification is high. Furthermore, the influence of sample date and hidden nodes on network convergence efficiency, precision as well as generalization has been studied.A portable DAQ system is established by applying virtual instrument control software LabVIEW,6062E card and other modules. Based on portable DAQ system, the signal acquisition and sensor calibration are developed, and get the satisfied speed and precision to monitoring and control of signals. Interface programs between DAQ and the model of identification and prediction have been developed, accordingly has realized the real-time identification and the optimal craft parameter real-time predication and control. The intellectualization control system of cap bending is established, the bending springback is controlled precisely through control pressure accordingly the intelligent control of sheet metal bending forming is realized. The results of four kind of plate in intelligent bending experiment indicated that the system is successful.