RTCP test axis motion planning for five-axis machine tool dynamic performance using observability optimization based on modified genetic algorithm
03 Nov 2021-The International Journal of Advanced Manufacturing Technology (Springer London)-pp 1-28
TL;DR: In this paper, a modified genetic algorithm is used to select the sensitive rotary axis position and velocity combos; cubic spline interpolation is then used to plan the axis motions based on the sensitive positions and velocities.
Abstract: In the five-axis CNC machining process, the dynamic tracking error due to servo dynamic performance deficiency is a main cause of processing inaccuracy during precise high-speed machining. The rotation tool center point (RTCP) test is commonly used to measure the dynamic performance of five-axis machine tools. The key to the capability of the RTCP test is axis motion planning in the test process. However, the axis motion plans for RTCP tests are usually based on simple motion instruction or engineering experience; the mechanism of the discrepancy between different axis motion plans is unclear. In this study, the axis motion planning process for RTCP dynamic performance tests is analyzed, and a novel axis motion planning method is proposed. The axis motion planning process is directly connected to the mechanism of dynamic tracking error; error observability is used as the index to guide RTCP axis motion planning. A modified genetic algorithm is used to select the sensitive rotary axis position and velocity combos; cubic spline interpolation is used to plan the axis motions based on the sensitive position and velocity combos.
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01 Jan 2023
TL;DR: In this article , the contour error of the tool center point (TCP) is greatly reduced by the method of dynamic modeling and feedforward, where the servo system of the feed axis is modeled and then the torque feedforward module is designed.
Abstract: The hybrid machine tool based on parallel spindle heads can efficiently process complex parts, but the load of the feed axes of the spindle head has the characteristics of nonlinear and coupling, which brings difficulties to the control. In this paper, the contour error of the tool center point (TCP) is greatly reduced by the method of dynamic modeling and feedforward. Specifically, the kinematic modeling is performed using the vector loop method, the dynamic modeling is performed using the virtual work principle, and the frictional force modeling is performed using the Stribeck model to obtain the dynamic model of the spindle head. The servo system of the feed axis is modeled and then the torque feedforward module is designed. Finally, in MATLAB/Simulink simulation, torque feedforward effectively reduces the contour error of TCP. Based on the analysis of the simulation results, the load torque of the parallel spindle head has the characteristics of nonlinearity and coupling. The evaluation index LCE (load caused error) is proposed, and the load torque mainly causes errors during acceleration, deceleration and commutation.
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