機(jī)械外文翻譯--對(duì)1ps+4tps型混合工作機(jī)床在插補(bǔ)原理和方法的研究-其他專(zhuān)業(yè)-全文預(yù)覽
【正文】 ith control vertex , and are normal B spline base for parameter u and v respectively. also have If row cutting method is adapted for surface machining, parallel planes can be used for incising surface of machining part, desired cutting path can be obtained. Curve equation located in the kth plane can be expressed as Normal vector N of cutting point of machining part surface can be calculated using following equation . Above equation can be rewriten as Furthermore, unit normal of N, namely, Ne can be obtained Where Supposing that the axis of cutter keeps consistent with orientation of surface normal of machining parts (Showen as ), so, according to geometry relationship, we have where is position vector of cutter reference point P, is pensationvector of cutting remains , is pensation vector of cutter radius, r is cutter radius. control of cutting velocity Feeding velocity V(u) along curve direction can be defined as Where So In sampling time t=kT, using Talor series and processing two order expandedness, we obtain Above equation is asymmetry iterative equation for parameter u. Feeding velocity along curve direction during machining process can be controlled by adjusting increment of parameter u, and feeding velocity along curve direction can be made to keep constant. So, smooth cutting characteristic can be achieved. . Fine interpolation algorithm PVT fine interpolation mode of pmac motion card is also called position, velocity, time motion mode. Under such PVT mode, interpolation period is set to be a constant, and acceleration is a linear function of time. Based on constrain condition of position and velocity of start point and end point, a smooth continuous spline curve can be obtained using Hermite interposition. So, acceleration velocity position of joint space under atain time can be expressed as Where . cutter path interval calculation fig .6a shows the situation, in which machined surface is a plane. Suppose radius of cutter is R, cutter path interval is L, remains height is h, based on geometry relationship in , we have In order to make the remains height less than the allowed height H0, following condition must be met Fig 6b shows the situation ,in which machined surface is a protruding surface . Suppose curvature radius of surface is ρ , based on geometry relationship in , we have Expand above equation using taylor series,the simplified equation can be expressed as In order to make the remains height less than the allowed height H0, following condition must be met Fig 6c shows the situation which machined surface is a concave surface. Based on geometry relationship in , we have Expand above equation using taylor series ,the simplified equation can be expressed as In order to make the remains height less than the allowed height H0, following condition must be met 6 ERROR ANALYSIS AND SIMULATION CALCULATION Based on derivation of above interpolation algorithm ,it ca be seen that interpolation point always located on section curve of machining surface, there is not direction keeps constant. Interpolation error mainly es forth from radial error of chord and curve, shown as Fig. 7. Suppose length of chord is L, curvature radius is ρ , error is δ , based on error relationship between chord and arc, we have feed speed of HMT is 10m/min, interpolation period of CNC system is 2ms, based on Eq.(36), it can be calculated that the interpolation error is m. So, it can be concluded that even the machining speed is very high, above interpolation algorithm can also implement high precise machining with machining error less than 1μ algorithm, we proceeded a calculation simulation. In order to simulate machining process, cutter motion is displayed dynamicly on puter screen, simulation program is designed using Delphi puter language. Fig. 8 shows simulation results of cutter motion path and cutter motion orientation (represented using cutter axis line), in order to display simulation results clearly, cutter motion path and cutter motion orientation are displayed after an interval of row, in Fig. 8, cutter axis line keeps perpendicular to maching plane. Graph display result and data sampling analysis result show that interpolation algorithm proposed in this paper is correct and feasible. 7. CONCLUSIONS AND DISCUSSION Closed from inverse displacement analysis model and inverse kinematic model for main feed mechanism of 1PS+4TPS type HMTs are established. Focusing on characte
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