System of drive of servo of numerical control machine tool is to point to with component of machine tool shift (wait like workbench, head, this book is with workbench only exemple) the automation system that the position and speed measure as control, say to procrastinate again use a system. On numerical control machine tool, servo drive system receives the feed pulse instruction that comes from interpolation device or interpolation software to generate, through certain signal commutation and voltage, power magnifies, workbench of machine tool of its translate into the photograph motion to cutting cutting tool. Current, this basically is handed in through be opposite, the control that dc servo electric machinery or pace take the feed drive element such as electric machinery will come true. The servo drive system of numerical control machine tool realizes the feed drive of the motion between cutting cutting tool and workpiece and actuator as a kind, it is a of numerical control machine tool main component, it decided the function of numerical control machine tool greatly, the highest and floating rate that is like numerical control machine tool, dog a series of main index such as precision, fixed position precision depend on the actor bad of performance of servo drive system. Accordingly, as the development of numerical control machine tool, consider and develop high-powered servo drive system, it is one of crucial technologies that machine tool of contemporary numerical control researchs all the time. To the main function of system of drive of servo of numerical control machine tool the requirement has a few following: (Limits of 1) feed speed wants big. Want to satisfy the requirement of feed of low speed cutting not only, be like 5mm/min, can satisfy the requirement of high speed feed even, be like 10000mm/min. (2) displacement precision wants tall. The displacement precision of servo is the displacement quantity that points to feed of workbench of machine tool of instruction pulse requirement and this instruction pulse via workbench of servo translate into actual displacement is measured between accord with degree. Both error heals small, the displacement precision of servo heals tall. Current, the precision of displacement of servo of numerical control machine tool of high accuracy can be achieved in the ± inside whole journey limits 5 μ M. Normally, interpolation implement or every give out the interpolation software of the computer instruction of pulse of a feed, servo its a displacement of corresponding machine tool workbench measures translate into, we say this displacement measures the pulse equivalent that is a machine tool. The pulse equivalent of common machine tool is 0.01~0.005mm pulse, its pulse equivalent can amount to the CNC machine tool of high accuracy 0.001mm pulse. Pulse equivalent is smaller, the displacement precision of the machine tool is taller. (3) follows the error wants small. Namely the speed of servo is answered should fast. (4) the working stability of servo is close friends. Want to have stronger interference rejection capacity, make sure feed rate is even, stable, make thereby can machine the part with a small surface roughness.