# The copy of machine tool of fictitious axis numerical control 3 axle control

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- source:PHAUP CNC Machining

F; Farther, undertake Fnew and Fold of uptodate feed speed comparative, and the Fk(mm/min) of adds computation of decelerate character curve to give current sampling cycle instantaneous feed speed according to the machine tool. Speed and the geometry that because interpolation is calculated,the error is controlled is not a kind of static state are calculated, it must make the distance between current interpolation dot and dot of before one interpolation satisfies feed speed to reach impose the requirement such as decelerate, make sure the interpolation between this 2 o'clock is straight even at the same time line segment and be in by the error between interpolation curve given inside allow poor limits. For this, need to be control target with instantaneous feed speed, in order to allow an error to restrain a condition linear to interpolation end length spends Dtk to undertake controlling. Its method is as follows: Above all, press the Fk of instantaneous feed speed that adds decelerate computation to give out, with computation leaving type current sampling cycle hopes mediumly chord (without the interpolation when the tie linear end length spends) : (The Dt1 in 3) type -- hope chord, mm T -- sampling is periodic, ms next, according to the error of sampling interpolation relation computation restrains chord: (The E in 4) type -- the permission between interpolation contrail and hope contrail error R -- the curvature radius of contrail of hope of interpolation point point is final, decide according to the opposite size of Dt1, Dt2 the extraction of Dtk is worth. Namely, if hope chord Dt1 is less than tie chord Dt2, make current interpolation straight Dt1 of ＝ of Dtk of line segment length, take Dtk=Dt2 otherwise. Task of calculative of contrail of interpolation of interpolation contrail computation is: In each sampling cycle, according to the interpolation that above gets linear end length spends Dtk, the coordinate that before interpolation contrail is duped, real time computation nods is worth. Its computation process is as follows: Above all, beg the Du that gives current interpolation cycle according to joining following concerns between variable increment Du and Dt: (The Du/ds in 5) type -- because interpolation frequency is taller,ginseng variable is led to the change of curvilinear arc length, the arc length in cycle of a sampling and chord are very adjacent, when be being calculated actually so, can make Du/ds ≈ Du/Dt. Take U one increment Du so, beg the Dt that gives correspondence, can get needs Du/ds. Although this expresses to be able to have little effect to feed speed approximately, but won't produce any effects to interpolation contrail precision. In sampling interpolation, orbit precision is main contradiction, the coordinate computation that interpolation nods must be aimed absolutely truly, and the accuracy of speed of motion of contrail of interpolation drop edge is in minor position, can be patient of is tiny error. The result that such getting assured orbit precision already, raised computational rate again. Next, calculate what current sampling cycle joins variable to take a cost: Uk=uk-1+Du (6) is final, uk era enters type (1) , the coordinate that before computation gives interpolation contrail to be duped, can nod is worth Xk, yk, zk. Till arrive at interpolation terminus,repeat above process ceaselessly, the interpolation contrail that can get whole disperse is changed. How does computation of map of 5 false or true move according to the three-dimensional cutting tool in empty axis space statement cost is right the length of lever of the 6 drive in solid axle space undertakes be controllinged accurately, it is to realize copy of fictitious axis machine tool the another crucial question of 3 axle control. To solve this problem, the empty axis motion that must produce interpolation dictates changeover is instruction of real axle control, its beg solution process to be as follows: Above all, according to copy 3 axes treatment needs to make axes of machine tool main shaft and workbench plane normal ask parallelly, affirmatory main shaft is initiative attitude At ＝ 0, bt ＝ 0. What decide platform Ct coordinate according to spare parts appearance and treatment requirement is optimal beforehand set buy Ct0. Next, before treatment begins in returning reference point to operate, will move platform to move At=0, bt ＝ 0, ct=Ct0 condition, make cutting tool axes and working mesa perpendicular, at=0 of cutting tool attitude, bt=0. Right now, the structure according to using platform is attainable on its 6 strong point (of 6 drive lever move end points) the initiative position Pxi in department of cutting tool coordinate, Pyi, Pzi(i=1, 2, ... , 6) . Be like K hour, the cutting tool contrail that computation of 3 axes interpolation produces dictates the value is Xk, Yk, Zk, it is make sure cutting tool attitude is constant, should make the 6 coordinate costs in moving end points to be fastened in cutting tool coordinate fixed, the in moving end points to fasten in machine tool coordinate coordinate that can get 6 drive lever from this is worth: Xdi=Xk+PxiYdi=Yk+Pyi (I=1, 2, ... , 6)Zdi=Zk+Pzi (of the 6 drive lever that gets above 7) basis move the Jing Duan with end points coordinate and machine tool foregone structure to nod coordinate, press type can get K hour the hope value of length of each drive lever, namely with Xk, yk, the solid axle coordinate of Zk correspondence is worth: (The Xji in 8) type, Yji, Zji -- static end points of 6 drive lever fastens medium coordinate to be worth space of 6 solid axles in machine tool coordinate 6 axes linkage controls contrail of cutting tool of empty axis space to generate is a kind of thick interpolation, when feed when rate is higher, thick interpolation straight line segment will be longer. Accordingly, to assure the smooth stability of linkage of 6 drive lever, interpolation of following essence of life can undertake in solid axle space. Above all, through false or true space of axis of map general empty (three dimensional space) interpolation is linear paragraph commutation is solid axle space (6 dimension space) straight line segment, its length is: (The Li0 in type of 9) -- thick interpolation is periodic in the begining solid axle coordinate is worth next, the shift of contrail of solid axle space in begging a cycle of each essence interpolation is apart from: The T1 in Dl=L/(T1/T2) (10) type, T2 -- the sampling of interpolation of thick, essence is periodic, ms then, begin N from this straight line segment the mobile quantity of each drive lever is periodic end of interpolation of essence of life: × of DLin=n × Dl (Li-Li0)/L (I=1, 2, ... , 6)(11) is farther, can get N hour to take a cost actually each drive staff is longly by next type, namely solid axle motion dictates the value is: Lin=Li0+DLin (I=1, 2, ... , 6)(12) is final, adopt system of the follow-up control that solve Ou [3] the actual length that assures drive staff and hope length are consistent, the solid axle linkage that can achieve contrail of contented cutting tool to ask is controlled. 7 systems implementation developed copy of fictitious axis machine tool according to the means that offers system of 3 axle control, if the graph is shown 3 times,its are comprised basically. This system is a foundation with system of Pentium Ⅱ personal computer, in its the interface that development of outfit proper motion adds on patulous bus line gets stuck, in order to realize the information exchange between control system and drive system. Software of numerical control system by C language + mixture process designing of 32 assembly language comes true. Graph 3 control system comprises block diagram when this system works, operation personnel can pass the I/O equipment such as floppy disk driver to input treatment place to want information, can pass the senior editor function that the system provides, undertake modification to the information that already inputted. Of the machine tool move to operate face plate to undertake controlling through computer clavier and numerical control by operation personnel, the concerned message that the system runs is shown through form of form of chromatic CRT to in an attempt to and data come. The L6 of ～ of solid axle L1 to the machine tool uses this system servo of communication of type of high accuracy number undertakes drive is controlled, each axis all uses closed-loop control means. Detect device uses high accuracy grating, in order to assure the displacement precision of solid axle. The logistic order that the switch in the system measures control to be used at controlling a machine tool partly moves, if control cutting tool changes, tray exchange, main shaft is opened stop, cooling system, journey protects those who wait for link to move. Switch quantity controls partial general and servo control to close suitably, finish the control of process of machine tool job jointly. Fictitious axis machine tool has 8 verdict rigid structure simple, stiffness tall, benefit is machined at realizing high speed wait for an advantage, but also exist rotate coordinate is effective the work area when small, much coordinate machines corner is narrow wait for defect. Accordingly, answer to produce its advantage in the high speed of groovy spare parts, efficient treatment. Pass copy 3 axle control, decreased effectively to control systematic complexity, reduced the totle drilling cost of the machine tool significantly thereby, be helpful for fictitious axis machine tool popularizing application inside bigger range. CNC Milling CNC Machining