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Open mixing machine is a mechanical equipment, which is widely used in rubber, plastic industries, mainly for its natural rubber refining plastic, rubber mixing .It is made up of body, roller, the transmission system, clearance adjustment, safety brakes, electric motors. Among them, clearance adjustment plays an important role in the automation and control. Aiming at the insufficient of existing clearance adjustment of open mixing machine, a digital control system based on MCU is proposed.By analyzing the practical work process of clearance adjustment system of open mixing machine, the digital control system which is designed in this paper is composed of data acquisition unit and main control unit. Data acquisition unit is designed to accomplish the sensor collections and communications, the main control unit carries through the work of system operation control, running state monitor, parameter set and so on. The whole system is based on the CAN bus architecture to meet a variety of communication requirements.As it is rich in function resources and its anti-interference ability is strong, the 16bit MCU MC9S12 which is the latest product of Motorola company has been adopted as key calculate part of the controller. The measures of separated power, photo isolate for input/output and shielded crust make the system more strong in reliabilities; In the structure of software, the embedded real-time operating system uC/OS-II have been used, which makes the system work as a real time system and can be designed simply. In the control method, the incremental digital PID control method achieved good control. PC program using Visual Basic language, be able to set the parameters for the node, and can draw real-time control of the curve.The debugging and running of the system indicate that it has the characteristics of a whole well-designed, simpler structure, lower cost, easier operation, higher reliability and friendly interface between human and system. It improves the working efficiency and the accuracy, meets the need of production, possesses good value of promotion.
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