Rotary Error Compensation And The Control Method Research Of CNC Lathe Aerostatic Bearings Spindle

With the rapid development of science and technology, people need more precision on the CNC lathe axis system. So, in order to meet growing high precision demand, that must be find a economic and reasonable, and feasible technology solutions. Aiming at the problem of rotary precision of the CNC Lathes spindle, this paper proposed a kind of bearing system which unified the gas bearing and the active magnetic bearing, in this system, gas bearings take the main load bearing part, the active magnetic bearings achievement assisted the part to revise the error of main bearing. It has the good advantages of high rotation precision, big carrying capacity and rigidity, and good controllability, etc.In this paper, the spindle system of CNC lathe includes two hydrostatic gas bearings and two active magnetic bearings, a thrust bearing. First, the structural parameters of gas bearings and magnetic bearings are designed; through research and analysis of precision grinder gas-magnetic bearings spindle system, single DOF and 5-DOF dynamics model are derived. Then, on the spindle error to harmonic separation, the accurate roundness error and rotary error are obtained. Finally, the control system is designed:the system is a closed system with feedback; three eddy current displacement sensors are respectively arranged on the front end and the back end of the spindle; the data collected as the input of the system, this value after the A/D transformation, transforms the digital signal to hardware CPU, that is a digital signal processor (DSP) center, finally obtained the magnetic bearings control law, input the signal after the D/A transformation to the magnetic bearings, to fix the spindle rotation error.The paper uses the Fuzzy self-tuning PID control method, according to the requirements of the control system to build the system simulation platform, through the simulation under the effect of fuzzy adaptive PID control of spindle rotation accuracy can be greatly improved or not. This verifes the feasibility and practicality of the control system, and achieves the purpose to improve the spindle’s gyration accuracy. Based on the TMS320LF2407A DSP, the control system of the CNC lathe of aerostatic bearing shaft system is designed, and the hardware and software part of the system also are designed.