| The high-speed, and high precision CNC machine tool not only requires high repeatpositioning accuracyandlow-speed smooth movement,but also requires high feed rate,highacceleration and high deceleration.When the feed rate exceeds60m/min,the ball screw isnot suitable for the high-speed feed system of CNC machine tools, which can be replacedby a linear motor feed system. This research employs a self-developed linear motor as thedrive of the machine tool feed system.The feedback component is grating. The torquecontrol modeis adopted in this system. The maximum acceleration of the linear motordirect feed system can achieve5g.Linear motor feed system eliminates the transmissionlinks.However,external interference affects the linear motor directly,which makesthe linearmotor control becomes more difficult.This article employs a Turbo PMAC as the controlcard, which controlling the linear motor together with the driver. The system modelis builton this basis. In order to improve the positioning accuracy of the linear motor feed system,the motion control system is researched. The main contents of this article are as follows:(1)Experimental study on Turbo PMAC of controlling the linear motor speedfeed-forward/acceleration feed-forward PID parameters is conducted. To understand therole of PID parameters in servo control, theTurbo PMAC is employed to control the linearmotor.The PID parameters in various working conditions are adjusted. The motionprecisionsin fixed working conditions are measured. The linear motor positioning accuracyis50nmwith load quality100KG and speed0~260000cts/s.(2)A fuzzy speed feed-forward PID self-tuning control strategyis presented.According to the experiences of the parameters and the motion precision, combining withthe fuzzy control theory, we designed a fuzzy speed feed-forward PID self-tuningcontroller. By adopting the PMAC custom servo arithmetic functions, the fuzzyfeed-forward PID control algorithm and the feed-forward PID control algorithmare arecompared at the speed of170000cts/s.The fuzzy adaptive controller is composed of speedfeed-forward, PID parameters and acceleration feed-forward.The experimental resultsshow that the fuzzy adaptive controller has a smaller step response rise timethan the PIDcontroller while debugging; the following error range of parabolic response curvebecomessmaller as well. (3) In order to overcome the PID parameter adjustment difficulties and external loaddisturbance, the pole placement adaptive controller of linear motor control system isdesigned. Through the system model, the system is configured to the desired closed-looppole based on the parameter adjustmentstated above. In this situation, the overshoot of thesystem is0; the damping ratio is1; and the system bandwidth is92Hz.Meanwhile,theonline identification tool of the system parameters is designed. Through the identificationof the motor load quality and rail damping coefficient, motor PID parameters can bemodified online, and the load quality can be compensated online as well. |
