Research On The Data Acquisition System Of Articulated Coordinate Measure Machine Based On CAN

Articulated coordinate measuring machine(ACMM) is applied more and more widely in the industry field of the reverse and detect, because of its several advantages ,such as compact structure, portability to be carried,flexibility to be used. Nowadays, the overseas technology of the ACMM has been mature, but its price always very high. Therefore, it is very urgent and significant to develop a homemade ACMM. In this dissertation, a series of research about data capture has been carried out based on the previous research in this field.At first, the work principle of the ACCM is analyzed. The ACCM achieved the aim of measurement based on the several nodes cooperate with each other. The entire data to be acquired is bulkiness, and the nodes must be able to respond sensitively, furthermore, work synchronously is also demanded for every node .Additionally, restricted by the machine structure, the circuitry used to communications between nodes must be as less as possible. Based on the above characteristics, the model of distributed control net based on CAN is presented, because CAN supports lots of advantages, such as excellent real-time, multimaster, high speed communications, low cost but excellent performance and so on. In this dissertation, the circuit of each node is designed based on the core of P87C591 microcontroller, which is integrated with the chip of SJA1000.Because only the protocol of date-linked layer and physic layer have been defined in the specification of the CAN2.0, and the application protocol must been defined by user themselves. In this dissertation, because of the special characteristics of the ACCM, the application protocol has been defined carefulness based on the designed hardware. Actually, the quality of communications and the complication of the software can be influenced directly by the application protocol. In this dissertation, the advantage of multimaster and data frames identified in CAN is full used, so that the real-time and reliability is insured in this system.In the end, the software in all the nodes is carried out, because the function in each node is different, and the emergency of each task for each node is also different. Therefore, the software of each node must be designed respectively. Because the measurement precision of ACCM is mostly decided by the real-time and synchronization if considered within software. Therefore, the spirit of real-time and synchronization is throughout the software of all the nodes. In order to make the ACCM be able to adapt different application, the interface to configure the work parameter is supported by the software. Furthermore, In order to enhance robust, the quality of the communications is monitored incessantly, and the system also has some ability to compare themselves when the communications quality deteriorated.