Study On The Motion Control System Of Coordinate Measuring Machines

With the rapid development of modern manufacturing engineering, coordinate measuring machines (CMM) are becoming the major inspection equipments in quality control system of manufacturing industry especially automatic production. However, it is very difficult for CMMs to measure some parts of complex geometric forms.The rapid development of digital signal processor (DSP) has advanced the motion controllers with the DSP core widely applied in the areas of modern cutting and measuring processes. Programmable motion controllers make the CMMs to achieve complicated curve motion. This makes it possible to measure some parts of complex geometric forms. On the other hand, it improves the flexibility of design.In particular, with the increasing accuracy of the CNC turntable, CMMs equipped with precise CNC turntable can measure the revolving parts more quickly and accurately. Besides, this promotes the further development of reverse engineering.In this thesis, the mechanical structure of the multi-axis CMM made by Yantai Zhonghuan Electro-mechanical Technology Development Co. Ltd is analyzed systematically. A proper motion control method for this CMM is proposed. To improve the speed and position tracking accuracy, the stiffness coefficients of the servo system and PID parameters of the motion control system, as well as the acceleration feedforward gain and velocity feedforward gain are optimized and adjusted. At the same time, the integrator windup phenomenon which appeared during the PID parameter adjusting process is analyzed, and an effective solution for it is proposed. Some key technologies of the motion control system, such as S–Curve profiling acceleration and deceleration motion, motion with complex curved trajectory, design of manual control system and multi-axis synchronization technology, are studied. The application of these key technologies makes the motion of complicated curve possible, which shows enormous potential especially in the reverse engineering. At last some system experiments were done and the positioning accuracy of the control system reached±1μm.