Track segment smooth transfer control algorithm The part contour track consists of straight line segments and arc segments. The current segment and straight line segment are transferred as shown. During the interpolation process, the current segment and line segment l are theoretically transferred via the Plstart point. If the current segment is not decelerated to 0, but is transferred at the speed ve, the distance S1 between the current point Pcur and the transfer point Plstart is smaller than the displacement S=veT of the transfer speed ve in an interpolation period T. In the next step of the current segment interpolation, the next interpolation point will exceed the end point Plstart. Therefore, the actual transfer point Pnext needs to be calculated on the line segment l.
Control Algorithm Error Analysis For the cases in Sections 1.1 and 1.2, the error is determined by Pcur, Pnext, and Plstart (PCstart) regardless of the type of patch cord segment. For a unified description, note that Plstart and PCstart are P. Errors as shown. A and 3b respectively indicate that ∠PcurPPnext is an obtuse angle and an acute angle. ∠PcurPPnext is the error analysis of the obtuse angle transfer for the obtuse angle. The transfer error is defined as the distance e from the theoretical transfer point P to the transfer line segment PcurPnext. Therefore, when the ∠PcurPPnext is an obtuse angle, the PcurP distance, Υ and Ve jointly determines the transfer error. If the calculated error is within the allowable range of accuracy, it can be transferred according to the transfer algorithm to avoid repeated start and stop of the motor, thereby improving the processing efficiency and quality, and prolonging the life of the motor. If the transfer error does not meet the accuracy requirements, it can be solved by appropriately reducing the transfer speed.
∠PcurPPnext is the acute angle transfer error analysis for the acute angle transfer of b, the transfer error is defined as the distance between the theoretical transfer point P and the starting point of the transfer line segment Pcur and Pnext e1 and e2, that is, after the transfer, e1 and E2 must meet the processing accuracy requirements. Taking the allowable error as 10Λm as an example, the interpolation period is T=4ms, ∠PcurPPnext=30°, S1=0.5S, then the speed at the time of transit is ve=1.8mms. In the acute angle transfer process, the two axes move in the opposite direction. Therefore, the acceleration caused by the change of the velocity component before and after the transfer of each axis should be less than the maximum acceleration allowed for each axis. Otherwise, the centripetal acceleration at the transition will exceed the servo capacity, resulting in a large trajectory error. In addition, for the acute angle transfer, the transfer line segment makes the transfer angle not sharper than the theoretical transfer angle, so it is not suitable for use when it is necessary to ensure the processing of the sharp corner.
The dynamic response analysis of the transit process speed can avoid the case where the speed is reduced to 0 in each interpolation according to the above algorithm, and the transfer is performed at the speed allowed by the track error; however, since the transfer, from the current segment to the transfer During the segment and from the transition to the next segment, the interpolation direction changes, so although the feed rate is the same before and after the transfer, the speed components of the axes vary. Therefore, it is necessary to analyze the dynamic response of the uniaxial velocity change during the transfer process. The speed of each interpolation axis speed depends on the dynamic response performance of the servo motor. If the dynamic response of the servo motor is better, the speed response is faster, and the contour error is small in one interpolation cycle; otherwise, if the servo motor Slower speed response results in large contour errors in one interpolation cycle.
It is judged whether the next segment to be transferred with the current segment is a straight segment or an arc segment, and thus a different transfer algorithm is used to solve the transfer point. After the transfer point is obtained, the transfer point should be used as the starting point of the segment when interpolating the next segment. According to the algorithm described in Section 1, in the experiment, the actual interpolation trajectory is engraved using a laser. The machine tool acceleration a=100mms2, the interpolation period T=4ms. The actual trajectory laser engraving is as shown. The actual interpolation points output by the GT100 system are compared with the theoretical trajectories as shown.
Conclusion This paper proposes a smooth transfer interpolation process control algorithm for the trajectory segment of numerical control system and analyzes the error. The dynamic characteristics of the speed during the interpolation process are established by establishing the mathematical model of the servo system, and the effectiveness of the algorithm is proved theoretically. In addition, the effectiveness of the algorithm is verified by experiments. At present, the algorithm has been applied in the GT100 type CNC system, which improves the processing efficiency under the premise of ensuring the surface processing quality.
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