Study On The Key Technology Of Measurement And Control System For Movable Bridge-type Coordinate Measuring Machine

With the rapid development of chinese automobile manufacturing and mould &die industry,the requirements of the performance and quality of the products,such as auto components and complex mold,have raised a lot.There are much technologies would be involved to meet the requirements,but the most important thing is the measurement of the three dimensional data of the products.The coordinate measuring machine(CMM)has been widely used in the field of mechanical manufacture,automobile manufacturing,mould & die industry and aviation because its several advantages such as high precision,good efficiency,high stability and better universality.However,with the rapid development of the advanced manufacturing and reverse engineering,it has put forward more stringent requirements of speed and accuracy on CMM.Taking the movable bridge-type CMM as the studying object,this paper thoroughly studied the three components of measurement and control system and its some key technologies.Finally,some relevant experiments are designed to verify the effectiveness.The main work and contributions are as follows.Firstly,the system structure of measurement and control system of CMM is analyzed,including the machinery,measurement and control parts.This part presents the concrete composition of the measurement and control system of the movable bridge-type CMM,describes the probe and grating measuring system.Secondly,some key technologies of the motion control system,such as S–Curve profiling acceleration and multi-axis synchronization technology,are studied.Moreover,some system experiments were done and it proves the positioning accuracy of the control system can reach(1~2)?m.Thirdly,the structure and working principle of the contact probe of CMM are described.As for the probe system,it mainly studies the probe calibration technology,put forward a new concept of functional diameter of tip,analyzes the impact of the different motion parameters on the functional diameter.In addition,as for the difficulty of the pretravel calibration,a double-trigger control method is proposed and the system structure of the single-direction repeatability and pretravel calibration of the probe are established.At last,the experiment proves the effectiveness of the proposed double-trigger control method.Finally,the key technology of the grating measurement system-the self-focusing control system is studied.The system mainly ensures that the light can focus on thegrid plane of the grating with a faster rate,so as to promise the measurement accuracy of the measuring system.In this system,an optimized particle swarm optimization(MPSO)algorithm is introduced to BP-PID to form a MPSO-BP-PID controller.Furthermore,in this paper,the simulation and analysis are taken for the BP-PID,PSO-BP-PID,and MPSO-BP-PID controller.According to the simulation results,it proves the proposed MPSO-BP-PID controller can significantly improve the accuracy,stability and robustness of the measuring system.