| Cable hoist system of sluice is extensively applied in water conservancy project, and has wide market prospect. But generally there are not protection measures for motor or system, or only some simple protection of hardware for motor, in the existing traditional cable hoist systems of sluice. So when they were used there often happen some events that motors burn down and wire rope snapped or winded, or production stopped because of the protective device mistake action leading to motor tripping, and that can't guarantee normal production and safety in production. In addition, in the traditional cable hoist systems of sluice, one instrument for gate opening and one rotary coder were used for gathering information of gate opening, and then sent the control signal to the PLC, and big errors might occur, more signal wire were required. So the system is very complicated, poor reliability might occur, and it is bad for the construction, commissioning, production and maintenance, and should consume massive manpower, physical resource, and financial resource.This paper is to focus on reforming traditional cable hoist control system of sluice, resolving existing industry production problems, and constructing one cable hoist intelligent integrated control system of sluice, which can achieve accurate measurement, protection and operation for the lifting equipment. The system is formed by PLC, electric power monitoring instrument, rotary encoder, pressure transducer, HMI, contactor, auxiliary relay, current transformer, motor, reducer, brake, buttons, switches and indicator lights, etc. The PLC is applied to the cable hoist system of sluice as the intelligent control core, from the software programming real-time monitoring system is achieved by detection gate opening and the speed through the encoder, and protections for motor and system are achieved by optimizing the PLC program using three-phase current, voltage and active power from electric power monitoring instrument. So the problem about safety in production should be resolved, and real-time accurate monitoring and protection for system are also achieved.The Modbus protocol is an international industrial standard protocols, provides users with an open, flexible and standard communication technology. Through the protocol, controllers and controllers, or controllers and other devices through the network can be communication. The Modbus industrial control network protocol was studied in this paper, a communication and control model of gate hoist based on Modbus was presented. By the model in each intelligent control system of gate hoist, many detecting and display equipments including electric power monitoring instrument, rotary encoder and HMI, which is compatible with Modbus, can be connected to the PLC by Modbus network, and the system hardware complexity should be reduced; and many intelligent control systems of gate hoist can also be connected to PC by Modbus network, So integrated control and monitoring should be achieved. The experiment indicates that all the detecting and control equipments can be effectively connected to the system by the communication and control method based on Modbus, which reduces cost of hardware, and it is possible to use the same hardware system controlling different gates hoist, and also reduces development and maintenance cost, and has a high practicability and economic value.In addition, PC with the software Kingview and Modbus communication protocol can monitor several PLC at the same time. It shouldn't need the serial board, and the system was simplified. So it is easier to operate and maintain the system, and realize future function development and integrated automation.The control system based on Modbus in this paper is not only applied in the intelligent control system of gate hoist, but can also be extensively applied in various industrial control systems. |
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