Research On Variable Time-domain Discrete Interpolation Control Method In Flexible Roll Forming

Flexible roll forming is a new plastic processing technique for the production of sheet metal, which defines the variable cross-section sheet metal that can be formed gradually into desired geometry as it travels the forming stations assembled with definite shape of rollers. Comparing to uniform cross-section roll forming products, flexible roll forming products can increase the bearing capacity of sheet metal, reduce the structural weight of products and lower the cost of production more efficient.The motion control is extremely complicated in flexible roll forming as to the process is kinds of coupling in shape such as horizontal bending, longitudinal tension, longitudinal bending and horizontal shearing. Therefore, it is required for real-time accuracy and dependable control to assure the sheet metal to be formed into desired products during the forming. By controlling the servo motors to drive the rollers of forming stations in longitudinal movement direction to form the sheet metal in horizontal movement direction, then the specified variable cross-section molding products can be completely rolled out when the movement distance perfectly matches with the sheet metal contour curve in time and space between each forming station.Applying the configuration programming is a common approach to achieve roll motion, but will not be able or difficult to realize by the configuration programming for complex contour without the rules such as hyperbolic, or the molding product in asymmetric cross-section shape. However, there are two other approaches such as simplifying the curves and using similar shapes to fit the process. And this will inevitably decrease the forming precision of products at a certain degree.According to the process characteristic of flexible roll forming, and its rollers motion control technology, this thesis propounds the variable time-domain discrete interpolation control method for achieving the process forming for variable cross-section sheet metal without rules. Based on the systematic research on the variable time-domain discrete interpolation control method, and according to its principle, this thesis develops the control system for flexible roll forming eventually by adopting the servo position control mode, and by making full use of the multi-axis control and the fast real-time communication capability of PMAC, the rich software resources and the efficient data processing capability of IPC.Abundant experiments indicate this system can achieve high precision and high good stability forming for variable cross-section sheet metal without rules, and the variable time- domain discrete interpolation control method provides a good control method for forming the variable cross-section sheet metal without rules in flexible roll forming.