Study On Motion Control System For Gear Hobbing Based On IPC And FPGA

Gear is an important component in mechanical transmission, Specially the noncircular gear, can realize the function that ordinary gear can not replace. however, there exist the problems of processing difficulties-low precision and efficiency for the traditional non-circular gear hobbing machine. In addition, currently the gear machining CNC system is mostly based on the matching CNC system of machine tool to achieve the second development, but the independent research and development of control algorithm can not be embedded. Thus the control precision of the system is limited. To solve these problems, now motion control system is researched and designed for CNC Hobbing of non-circular gears based on IPC, using PCIE bus to connect the upper and lower machine, FPGA as the main control unit. And motion control card is an important part,which is connected with the upper computer and the servo mechanism, and plays a key role. The main contents are as follows:Firstly, this paper analyzes the hobbing machine motion relationship, and establishes the hobbing need mathematical model. According to the mathematical model,the motion characteristics of noncircular gear in hobbing machining is studied, which provides reference for selection of order number and eccentricity for non-circular gear in the design phase. Besides, the method of hobbing movement is analyzed, and the scheme of constant angular velocity of the hob and the change of the angular velocity of the workpiece is determined.Secondly, the electronic gear box function is realized by the FPGA motion control card. In the design process of electronic gear box, master-slave control structure is used. In order to improve the accuracy of the gear box, the PLL and pulse frequency technology are adopted. In order to realize the speed and position control, the feed forward and PID control is applied. In addition, in order to alleviate the pressure of the FPGA motion control card, to achieve high speed and high precision motion control, the application in the IPC is designed to achieved velocity, displacement and other real-time data preprocessing(coarse interpolation).Finally, according to the functional objectives, the overall scheme of motion control card is planned. The FPGA development board model is selected,and timing simulations of module of electronic gear box are given. The PCIE is used as the communication interface bus to insert the IPC card slot. In order to improve the hardware integration and reliability of the control card, FPGA external interface function is achieved,for example, encoder interface, D/A interface and so on, and the circuit diagram and timing simulation are realized.