The Research And Implement Of Control System Of Highly Precise Computerized Combination Balance Based On CAN Field Bus

With the main thread of the weightily systematic precision improving, this paper, in mechanics and electronic view, deals with the research and implement of control system of highly precise computerized combination balance based on CAN field bus from the conceive of the system structure, the analysis of measuring precision, the design of the electric and the means of the anti—jamming and so on.With the continuous development of industrial automation, an electronic weighing scale applied widely on the field of circulating commodity and business of packing foodstuff appears—the control system of highly precise computerized combination balance. Especially in the food industry, the weighing scale is utilized extensively, Not only easing the work strength of the enterprise's workers consumedly, and raising production efficiency, but also making the packing product attain to ideal weight. This promises a business enterprise to prohibit indeed and avoids the economic loss because of not measuring accurately, in the meantime also promises the consumer's benefits, so combination balance has been well received by large customers.On the basis of the thinking of various kinds of automatic measuring equipment, according to the development of sensor, microprocessor network, communication technology, the system has adopted CAN field bus method to measure, which is made up of a host industrial controlling computer and many servant microprocessor, the host computer gives control task each servant microprocessor. In other words, every servant microprocessor can be regarded as one independent control unit. It realized that data management be separating from process control, heightening the controlling speed of the weighing system. At the same time, it is scattered that the whole trouble risk of the measuring system, so its dependability more improves. In the thesis, it is expounded the mathematics model of combination weighing, and the analysis of various kinds of factors which influences weighing speed and precision, and then the design of the best combination algorithm and the systemic network structure. The whole combination weighing system is made of one industrial control computer and many weighing units, CAN field bus joins the upper machine to every weighing unit, this constitutes a network system based on CAN field bus. The system uses SJA1000 as a network processor and 82C250 as the driver of receiving and sending. In order to improve weighing speed, every weighing unit uses two microcontrollers, a host MCU is MSC1210 produced by Texas Instruments, a servant MCU is AT89C2051, the host MCU is used as weighing accurately, the servant MUC is used as controlling stepper motors, the system uses also LMD18245,which is a stepping motor driver. The system programs with Keil C51 and VB6.0, including data acquisition and wave-percolation, communication, the switch control, combination calculating and so on. Additionally, some methods of anti-jamming that are adopted in this system are also studied.