| Large Belt Conveyor requires speed control during the start process. Controlled start transmission which is researched in this paper is based on internal friction in Newton's Theorem, using viscous shear forces to deliver power. High transfer efficiency, easy control, overload protection and other functions are the characteristics. But now in our country, the technology only widely used in the water pump and fan industry, for the research on belt still in backward stage relatively.Taking the CST system which is the products of Dodge Company as the research object, analysis the theory of machinery, pressure control circuit and control method, as while as combining with the simulation through computer and experiments. Corresponding with domestic product in order to increase the control precision and response speed of the system, the paper puts some measures to improve, which making the system well satisfied the control requirements such as the controlled start, adjusting speed control and so on.The whole belt conveyor network is based on Profibus-DP network configuration mode, using PLC to control every analogue and digital quantity, meanwhile monitoring the startup mode of the conveyor belt, alarming when the system is overload, overheat or tape skid alarms. Pressure control system is applied electro-hydraulic proportional control system. High control accuracy stability and not high demand to the environment make the electro-hydraulic proportional valve more suitable for the actual engineering than servo valve. The electrical control part mainly adopts closed loop PID control (including of pressure, velocity, acceleration and power PID control), of which the main control parameters are belt speed and motor power to ensure that the system of the ideal start with power balance of each motor output.This paper analyzes the control method of the system in small flow. At present, most agencies use proportional relief valve to control pressure which can not meet the requirements well. According to the situation above, the paper proposes using as the improvements. First models the 3/2 electro-hydraulic proportional reduce valve in SimulationX, then puts forward that using PID closed-loop control optimizing valve pressure control performance. On the basic discussed above, the paper puts forward a scheme to design experiment to control the valve, simulat the start process of conveyor with the pressure PID control. The results verified the theory and simulation analysis.The belt conveyor with controlled start transmission system designed in the paper sets machinery, electricity and liquid at an organic whole and the control effect is far much better, easily bringing about extending the service life of the conveyor belt, improving the safety coefficient and production efficiency of the equipments.
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