Mix to character of high speed, high spirit, fast face as acting machine tool the way of tall stability develops, the application of direct drive technology increasingly enlarge is added. The advantage of direct drive system, in control only system, electric machinery is mixed measure the system is coordinated each other and cooperate under ability is able to develop adequately, survey a system performance of system of direct to reflecting drive crucial. The linear grating feet that is based on technology of scanning of photoelectricity type only field / angle coder has the advantage with high accuracy, high resolution and fractionize small error, suit direct drive application very much. From control academic side looks, the heat of the main transfer machinery when reciprocate of the transmission error that because machine tool of half dead loop controls a system to cannot overcome machine tool main transfer machinery,arises, high speed is out of shape sum of errors wears away, completely dead loop controls theory to apply increasingly already in control of contemporary machine tool as what can eliminate transmission error. Drive technology respect, because of direct drive and conventional drive photograph comparing has high accuracy, tall dynamic character, low attrition, safeguard mix simply efficient wait for a characteristic, wide application is won in machine tool industry. Measure technical respect, code as a result of very form and technology of scanning of only field of type of interfacial technology, photoelectricity the application that wait, the precision that measures feedback component, resolution and security had very big rise. The efficiency of numerical control machine tool raises hang on to control system, electric machinery, machine component and coordinate what measure a system to wait each other with cooperate. Right choice surveys a system, the function to the machine tool especially direct drive system has main effect. The expression of efficiency of direct drive system depends on greatly the choice that the position measures package, have extremely high demand to measuring package: The measurement with tall ① precision; The fractionize error with small ② ; The resolution with high ③ ; ④ is jam-free. The largest dominant position of direct drive depends on direct drive technology its drive component (linear electric machinery or pitching moment electric machinery) and by drive component (workbench or revolving stage) between without other drive disk assembly, join tigidity is tall, because this is direct,the gain of operating ring system of drive system can be more than conventional drive system far. Tall gain has its advantage, but the requirement that also raised to output signal character to measuring package at the same time, at linear grating feet is linear electric machinery, at angle coder is pitching moment electric machinery. Graph system of 1 direct drive dies to dominate a picture circularly completely 2 linear electric machinery and sketch map of pitching moment electric machinery pursue the impact of 3 fractionize error to exterior character is immediate drive system is done not have special at speed operating ring rotate coder, its position operating ring and speed measure annulus to share same measure package (1) seeing a picture. Speed operating ring needs to have very small signal cycle, from this, the resolution need that measures package is enough tall, assure when to machine tool low speed moves, also can undertake exact rate is controlled thereby. Direct drive uses linear grating rule / the grating reticle of linear grating feet or angle coder collects angle coder to be engraved with photoetching craft make go up in glass or metal strip matrix, bar of this kind of reticle is apart from minimum and edge clarity, even. Field scanning technology and high grade signal handle the photoelectricity type sheet that cooperates to be not a contact circuit, linear grating feet and angle coder can provide the high quality signal of high accuracy, high resolution and small fractionize error for direct drive system, opposite to pollution not sensitive (in the graph that control a problem, gules area is contaminative) , the position that assures drive system finally measures stability of precision, rate and relatively constant temperature, ensure of the system move smoothly. Fractionize error is measured to the influence of direct drive package is using increment formula or measurement technique wins very form after two phasic difference are the positional signal of 90 ° , need to undertake farther fractionize will achieve place to require resolution. Because signal of actual output position scans the reason such as means, pollution and follow-up electron processing, meeting and ideal sine signal have deviation. When undertaking fractionize, this kind of deviation can be inside cycle of a signal the high frequency error with periodic generation, namely the error inside single signal cycle or fractionize error. Fractionize error depends on character of the signal cycle that measures package, reticle and scanning character. The position that uses scanning of photoelectricity type only field at present measures package to be able to restrict fractionize error in signal cycle 1% the left and right sides, for example the linear grating feet that signal cycle is 20µm, its fractionize error is 0. 2µm. Fractionize error not only the fixed position precision that affects direct drive system, can affect the stability of speed operating ring more. The speed operating ring that controls a system is opposite according to the fixed position error of feed system the working electric current of drive system has consideration, control linear electric machinery or fact of pitching moment electric machinery to bring to bear on then decelerate. When speed of feed of numerical control machine tool is inferior, feed system follows fractionize error. Direct drive system controls bandwidth from this as a result of tall gain big, fractionize error gets inside a bigger speed limits the impact is bigger. When milling workpiece, as a result of the influence of fractionize error, workpiece surface can have moire shape to machine a trace, affect the exterior quality of workpiece badly, if pursue,3 are shown. Say commonly, the wavelengh of moire record mark and amplitude and fractionize error become direct ratio. As a result of the existence of fractionize error, the electric machinery interior of direct drive can produce additional electricity, produce extra quantity of heat and noise thereby. Rate of feed of electric machinery of fractionize sum of errors is older, quantity of heat of electric machinery hair and noise are bigger. In addition, control a system from measuring package to get the position to be worth, if the position believes date resolution and fractionize error to be close to relatively, fractionize error can be differentiated to be the athletic error of system of machine tool feed, control system is met random sex ground sends compensation signal to feed system. This meeting brings about control system concussion, the component of machine tool motion such as the slideway of linear electric machinery is long high frequency reciprocate, wear away quickly thereby, lower service life. The system of dynamic and characteristic direct drive of direct drive system has good dynamic character, often have campaign of feed of high speed, tall acceleration, this requirement measures a system to have good signal quality, expensive electric campaign speed and fight exceedingly goodly brace up, anti-impact properties. Scanning of photoelectricity type only field is linear the signal quality of grating feet and angle coder is high, measure between grating reticle and reading head without the contact make its are not had wear away, and fight brace up, anti-impact properties is good, electric motion speed can amount to 180 M/min. The place on put together is narrated, be aimed at the applied characteristic of direct drive system, scanning of photoelectricity type only field is linear grating feet and angle coder are his the high quality signal that positional operating ring and speed operating ring provided error of high accuracy, high resolution, small fractionize, those who assured drive system is efficient, smooth move, can realize the treatment of character of high speed, high spirit, fast face and tall stability finally. CNC Milling