Simulation Of AC Servo Feed System Based On Fuzzy-PI Control

In usual, there are definite parameters in design and analysis of the feed servo systemin CNC so as to choose mostly reasonable control parameters in PID. However, in theactual industrial production, some parameters may change and then its PID controlparameters may be unreasonable, and seriously even break the stability of the system. Sowe must adjust some original parameters. Taking advantages of combination of fuzzycontrol and PID control, the paper designed a self-tuning fuzzy-PI controller. Applied tothe feed servo system and simulated, its result showed that the system could overcomeadverse effect such as parameter variations, strong coupling and time-varying factors andimprove its dynamic quality.Firstly, the article made some analysis of the feed servo system and mathematicalmodels of a PMSM and a mechanical drive system were respectively established.Followed by a control system was established based on id0including tricyclicstructure (position loop, velocity loop, current loop).Then a simulation model of feedservo system was established in Modelica, including PMSM, mechanical feed drivesystem, inverter, SVPWM, etc. The result of simulation showed that an appropriateinherent frequencywm and damping ratio were of great significance for rapid andstability of the system. At the same time, the simulation model could quantitatively studysuch as a screw and equivalent stiffness impacted on its output, and it provided a basis foranalysis and design of the system.In order to deal with some objects which have nonlinear, time-varying and strongcoupling as much better, the paper designed a fuzzy-PI controller taking the idea of fuzzycontrol account into PI control systems in the feed servo system. The fuzzy-PI controllercould adjust two control parameters online according to the motor speed deviation and itsrate of change through fuzzy control rules and fuzzy algorithm.Finally, with the advantages of simple structure and strong robustness, the simulationresults showed that the method could improve rapid response and control accuracy andhad much potential in engineering.The study in the paper has some meanings to design and analysis of feed servosystem. Similarly, the idea of fuzzy-PI is applied to the spindle servo system. And itprovides a new idea to research on improving the intelligence, high precision, and practicein CNC.