The Optimal Design And Kinematic Control Of Parallel Machine Tool For Bending Metal Tools Based On Stewart Platform

In practice, metal pipes with diverse radius of curvature are commonly used, and how to bend a pipe rapidly and easily by an intelligent machine tool has drawn attention of many researchers in machinery manufacturing. The Stewart Platform has much good performance, such as multiple degrees of freedom, hard structural stiffness, high carrying capacity, good kinematic precision, simple inverse position, easy force feedback control and so on. It is novel to use the Stewart Platform as the manipulator of the parallel machine tool for bending metal pipes. In this thesis, the conceptual design, optimal design for the structural parameters and track following control of the parallel machine tool for bending metal pipes based on Stewart Platform have been investigated as follows:Firstly, the conceptual design of the machine tool is accomplished, according to the requirements for bending metal pipes. A 6-SPS parallel Stewart platform made up of a fixed platform, a moving platform, and six legs driven by servo hydraulic cylinders is chosen as the manipulator of the parallel machine tool for bending metal pipes. And the pipe is designed to be clamped horizontally to augment the workspace of the machine tool.Secondly, a multi-object optimal design method based on Genetic algorithm is presented to determine the structural parameters of the machine tool to meet the needs of workspace and precision. The kinematic and dynamic simulation results of the machine tool with optimal structural parameters show that its performance is improved. Thirdly, a track following control method based on united feedback linearization and Nerve Network is proposed to control the leg's velocity output. It is indicated from the leg's velocity control simulation when the paths of the manufacturing point on the moving platform are circle and screw respectively that, by the proposed control method, the path error is decreased observably to ensure machining precision.The kinematic and dynamic modeling, optimization, control and simulation in this thesis are conducted utilizing MATLAB software.