Research On Effects Of Influencing Factors Of Dynamic Accuracy Of Five-Axis Hybrid Machine Tool Based On RTCP

With the continuous development and improvement of the parallel mechanism,the high load capacity,high response and flexible swing characteristics of the parallel mechanism are combined with the large working space and the high-precision motion capability of the series mechanism,and the five-axis based on the series-parallel mechanism is developed.The five-axis hybrid processing equipment is a reliable choice for high-speed machining of aerospace aluminum alloys.In this paper,the PRS-XY fiveaxis hybrid machine tool is taken as the research object,and its dynamic precision is studied.The RTCP function of the traditional five-axis CNC machine is used.By setting the tool point of hybrid machine always be on the programmed track,a RTCP detection trajectory belonging to the hybrid machine tool is described.Based on the built five-axis linkage model,and the effects of dynamic error on the tool point motion error is simulated and analyzed by running RTCP detection trajectories.The specific research contents are as follows:(1)The structural characteristics of the five-axis hybrid machine tool are analyzed,and the mathematical model of the machine's forward and inverse kinematics is constructed.Then the numerical analysis method is used to verify the correctness of the two models.The RTCP working principle of high-grade five-axis CNC machine tools is introduced.Based on the RTCP detection method of traditional CNC machine tools,the RTCP detection trajectory belonging to the five-axis hybrid machine tool is studied.And the described trajectory has the feature that the tool point of the five-axis hybrid machine is always on the programmed trajectory.(2)The composition of the servo control system of the five-axis hybrid machine tool drive shaft is introduced.The control system of the parallel mechanism and the series axis XY table are discussed separately.The mechanical transmission system is build after rationally simplifying the ball screw feed system.By analyzing the traditional PID control,the three-axis control model of the three-loop control of the machine tool servo control system is established.Adding feedforward to optimize servo control system model.Then the relationship between dynamic error and tool center point motion error is established.(3)The linkage system for a five-axis hybrid machine is built in the Simulink environment.To verify its correctness,the physical system of the machine is built in the SimMechanics environment.Then,under the same expected trajectory,the actual output displacements of the sliders are simulated to verify the correctness and effectiveness of the models in the two environments.(4)Based on the established tool point motion error model,the RTCP detection trajectory is run by the five-axis linkage model in the Simulink environment.The action law between the following error of the hybrid machine tool and the position error of the tool tip is simulated and analyzed.A dynamic error transfer index is proposed to characterize the transfer relationship between the machine axes and the tool point motion error.Finally,the multi-dimensional display method is used to obtain the motion error trajectory of the tool point characteristic corresponding to the following error of each drive axis.It helps the traceability of the dynamic error of the hybrid machine tool and provides guiding suggestions for dynamic error compensation,thus achieving the effect of improving the machining accuracy of the machine tool.