Trajectory Control Strategy Of 3-PUU Parallel Mechanism Coordinate Measuring Machine

In recent decades,the application of coordinate measuring machines has become increasingly mature and extensive.The trajectory planning is an important topic in its motion control.This subject aims to design a suitable trajectory control solution for the 3-PUU parallel coordinate measuring machine.The measuring machine can comply three-dimensional coordinate measurement coordinates only with a pair of precision guide rails and a set of long grating displacement sensors.The x-axis direction can be properly extended according to the size of the measured object.Compared with the existing parallel measuring machine,3-PUU has the advantages of large working space and simple structure,and important theoretical and practical significance.This subject studies its trajectory planning scheme and achieves its complex trajectory movement with the control algorithm to improve its movement accuracy.This paper has established the forward and inverse kinematics solution model of the parallel mechanism by analyzing the working principle of the 3-PUU parallel measuring machine.I has solved its workspace with Python,obtained the singular configuration of the three-coordinate parallel measuring machine through Jacobian matrix,and completed the singularity analysis.The simulation software ADAMS is used to construct the kinematics model.And the inverse solution model is used for kinematics simulation to plan 3-PUU’s movement trajectory.Taking the kinematic theory and hardware condition of prototype control system as the basis,the ADAMS model is used to realize the complex motion of the parallel mechanism in the working space through the multi-axis interpolation method.During the movement,the pulses value corresponding to the displacement of the driving sliders which are collected in real time by the grating reading head,will be collected by the data acquisition card and fed back to the host computer for real-time display.And during this process,the displacement information of the sliders can be recorded manually.At the same time,two PID control strategies based on neural network are proposed in this paper to deal with the correction of the motion error of the drive sliders’ segment displacement which are beneficial to improve the motion accuracy of the parallel mechanism.