, , the mechanism of treatment precision influence that the scholar such as introductive Yu Wenhua passes characteristic to servo trends logarithm to accuse machine tool round contrail undertakes study, think to be below the premise of the geometrical precision that takes no account of machine tool oneself, outline tracking error of the system basically is do not match by the dynamic parameter between the dynamic character of servo and linkage axis and cause. Accordingly, machine precision to raise the outline of the machine tool, domestic and international expert and learned man are common from the following 3 respects begin: The first, compensation of machine tool precision. Be like, represent current world superprecision 3 of top level large exceed accurate machine tool (the DTM of laboratory of American LLNL state, 3 model horizontal is large and optical diamond lathe, LODTM vertical is large and optical the OAGM that development of diamond lathe and British Cranfield company succeeds, 2500 model exceed nicety, compensate in order to realize online precision control; The 2nd, the high accuracy of athletic rod dogs control. Be like, tomizuka put forward a kind of 0 phasic errors to dog control (ZPETC) is algorithmic, this is algorithm of control of the make a present of before a kind of number type that signal changes when be being used at dogging, the tracking error peace that it can receive minimum dogs slipperily speed, but it is compared to building parameter of system of modular sum of errors to change sensitive, be opposite at the same time of interpolation data discontinuous (what main show varies for speed and acceleration is discontinuous the high frequency composition in the signal of the input that cause) more sensitive; The 3rd, the alternate coupling control of linkage axis. Koren put forward outline of alternate the top of a kitchen range to control (Cross, CoupledContourControl) is algorithmic, theoretical analysis makes clear, although be below the circumstance with very small tracking error, outline error of the system is likely still very big, accordingly, he regards control quantity as to undertake closed circuit outline is controlled the outline error between linkage axis directly. But, when undertaking linear interpolation, alternate coupling controller is a many variable system, when undertaking circular arc interpolation, be the system changes when a changeful quantity, systematic analysis and control all special difficulty, on the other hand, controller of outline of alternate the top of a kitchen range chooses to wait for a respect to still be perfected not quite in structural design, parameter, restricted its to apply actually. The error of numerical control interpolation that the article used a kind to be based on time to break up a principle compensates algorithm. This algorithm can come true to replace straight line segment to approach with 2 curves give rough sketch, can compensate the interpolation error that former interpolation algorithm brings already, what also can reduce interpolation data is discontinuous to dogging the influence of precision, the outline that improves a system thereby machines precision. The compensation controller that uses this method does not need to make any changes to original interpolation plant, just control systematic software to be revised slightly to servo. The article analysed this algorithmic academic error, the HCM that developing by institute of Electromechanical of Harbin Institute of Technology, 1 model super- undertook actual outline compensates control experiment on accurate lathe, the outline that experimental result proved to this algorithm can raise a machine tool significantly machines precision. 2, main component is the interpolation algorithm that compensates machine tool of algorithmic numerical control: Sampling data standard and referenced pulse law. Algorithm of two kinds of big interpolation has the specific implementation way that makes a variety of differring each again. The HCM that developing, 1 model the interpolation signal that exceeds accurate lathe to went up to use sampling data standard and band of photograph of referenced pulse law creates a method: Use sampling data standard to undertake counting accusing thick interpolation above all, give the point of an a series of disperse that have identical time-interval by thick interpolation controller, use linear interpolation method to undertake interpolation of essence of life between dot and dot next, generate the referenced pulse that can mirror feed speed and displacement finally. If pursue,1 is shown. In random two speed and displacement can express to be respectively: Medium, At is type interpolation is periodic. If use straight line segment to approach outline curve, put inevitably in outline error on one hand, what can cause interpolation speed and acceleration on the other hand is discontinuous. In the meantime, because straight line segment does not have assemble effect, can cause place to machine optical spare parts spot of the dispersion in using a process is bigger, influence performance characteristics. Nextpage to solve this one problem, used a kind of new outline error to compensate control algorithm now, this kind of algorithmic main characteristic is given to interpolation system the instruction undertook modification, make of the positional servo controller inside aleatoric interpolation cycle giving feed rate is linear change. If pursue,2 are shown. Be in I, I+1 time paragraph inside speed and displacement expression see pattern respectively (3) and (4) . Type (in 4) , the extraction of K is worth the curvature of the slope that mirrorred speed-distance curve and displacement curve, if pursue,3 are shown. On the foundation that assures error compensatory precision, go to the lavatory considering the analysis, k ＝ is taken in the article 2. Such, actually before approached optical curve to become with straight line segment will approach with 2 curves. 3, the academic error that error analysis analyses interpolation of the curved surface that be not a ball to facilitate, we nod the curve is not a circle around to be able to use the intimate circle that has collective curvature radius with its to replace in I suppose, if pursue,4 are shown. The curvature that I nods is: Nextpage 1/C of this radius R ＝ of intimate circle, such we control interpolation of the curve that be not a circle and compensation the analysis that the analytic change of the error became circular arc interpolation and compensation control error, make the problem got thereby very big simplify. Should use inside when receiving bowstring to approach former arc, error of its interpolation principle is: The algorithm of interpolation error compensation of article intermediary carry on is equivalent to be in interpolation of former linear position increased a compensation to control the E that measure △ on algorithmic foundation, by type (9) is knowable, 4 when just reduced step pitch role by 2 of original step pitch character square, be opposite namely same curve, below same interpolation error condition, approach inside the length that receive bowstring can increase 100 times, reduced greatly thereby go up the operation quantity of a machine, make go up the interpolation when a machine reality is actual becomes a possibility. 4, experimental test and verify for test and verify the effectiveness of this plan, the HCM that developing by institute of Electromechanical of Harbin Institute of Technology, 1 model super- undertook actual circular arc outline controls an experiment on accurate machine tool. The principle graph of system of numerical control of this machine tool sees a picture 5, it uses multiprocessing implement distributed control structure, through Chan Pin laser interferometer makes positional closed-loop control, servo cycle is 8ms, interpolation cycle is 40ms. Circular arc radius is 30mm. Feed speed is 5mm/min. Among them, when be approached with straight line segment, the length of straight line segment is taken 0. 05mm. After using this compensation to control a method, the outline control precision of the machine tool can rise 0.
1 μ M. CNC Milling