Universal CNC Control Technology For Industrial Computed Tomography

Industrial Computed Tomography (CT) is one of the universally acknowledged optimum detecting methods. Its domestic application becomes more and more widely, which makes it plays a more and more important role in the new technology fields recently. The development of CT and the extensive application call for higher requirements of Industrial CT, including the CT imaging precision, rapid response ability, multitasking and expandability. As a key technology of Industrial CT, the control system determines whether the above requirements can be realized. Currently, the control system is difficult to meet the high accuracy and rapid response demands when multi-axis motion integrated, meanwhile, it needs a long time to develop and is hard to build flexiblely. In order to solve these problems, the research concerning on the control technology of Industrial CT is carried out in this paper.Firstly, the performance and functional requirements of control system in Industrial CT were analyzed in this paper, then the comparisons of merits and demerits were made among various main control technology types in Industrial CT. Based on the above analysis, a control technology for Industrial CT using universal Computerized Numerical Control (CNC) system known as SIEMENS SINUMERIK 840D was presented, and its feasibility was discussed, then the modular system structure centering on 840D was designed, at last the control platform was established.Aiming to the second and third generation scanning mode, which are commonly used in Industrial CT, each control mode was analyzed. Then the motion control method based on the CNC platform was researched, and the synchronous control method adopting synchronized action and NCK I/O was determined. According to the communication requirement between the control system and the principal computer, the basic underlying control function, the calling method and the access to acquiring the data in 840D were studied. By adopting SIEMENS OEM development software and DDE technology, the scanning parameters of Industrial CT realized the offline loading by the Ethernet. Based on the software structure of Industrial CT control systerm, the NC and PLC program were designed.Finally, through researching on the closed-loop control unit of SIMODRIVE 611D, particularly the speed loop and position loop, the mathematical model of entire closed loop position control was established. By analyzing the parameters in the time and frequency domain, the parameters optimization was completed, which made the system control performance improved.The tests of the second and the third generation of CT scanning motion process on the control platform show that the Industrial CT control technology based on the universal CNC system can meet the requirements of the multi-axis motion integration and the synchronous requirements for data acquisition. It has advantages in the control precision and the performance. Meanwhile, the system not only has high reliability, but also is easy to expand and can be flexible constructed for different requirements in various Industrial CT fields.