Study On The Motion Control Card For CNC Gear Hobbing

Motion control card was the bridge between CNC system and the servo system, Which play an important role in the CNC machine. With the rapid development of the open CNC system based on IPC (Industry Personal Computer) architecture combine the motion control card providing a rapid and efficient way to develop a high performance CNC machine.Gears serve as the important fundamental parts in machines transmission, but high precision gear were manufactured difficult and inefficient because of the gear’s complicated parameters. To solve this problem it is an efficient way to design a motion control card for gear hobbing in which the indispensable inner-linked transmission chain relation were replaced by EGB (electronic gear box). Thus, The EGB is the key technology in motion control card for gear hobbing.Firstly, the motion principles of hobbing machine were analyzed and the mathematic formulas were deduced including non-circular gear. According to the hobbing machine’s feature to improve the transmission accuracy EGB was employed to replace the mechanical gear transmission chain. Since there is no EGB available in china. In this paper the EGB was implemented by a FPGA(Field Programmable Gate Array), After the EGB type analyzed the B-axis signal tracing type was taken, meanwhile the PLL (Phase lock loop) concept was also taken into EGB, Second the timing sequence of EGB were simulated based on Quartus II software. Since no-circular gears are used widely in industry, Thus the EBG for non-circular gear hobbing was also discussed. The embedded system was design in charge of the transmission ratio refreshment to meet the requirement of non-circular gear hobbing caused by the polar axis length change.At last the blue print of motion control card was designed based on PCI-bus and DSP+FPGA mode was adopted. This approach has been proved of good adaptability and easiness of software update. The discrete PID method incorporate with feedforward control model were taken and implemented by FPGA.To improve speed detect precision the feedback signal come from encoder were quadrupled in motion control card.