Research On Low-power Consumption Wireless Monitoring System For Dynamic Tensions Of Chains In Scraper Conveyors

The scraper conveyor is an important equipment for fully-mechanized face.The scraper chains are the key component of the scraper conveyor and it is easy to fail.It is important to monitor the state of scraper chains.There often are a large amount of mineral water in working face which can reach the middle plates which brings difficulties to install the monitoring system.Therefore,a modification scheme of scraper conveyor and a set of low-power consumption wireless monitoring system for dynamic tension of chains in scraper conveyors were proposed.The research content of this paper is mainly as follows.Firstly,the necessity of the tension monitoring and the influence of the actual working condition of the scraper conveyor on the monitoring system are analyzed.The difficulties of the installation of the tension monitoring system of the scraper conveyor and the influence of the actual working conditions on the function of the monitoring system are clarified.According to the requirement of function,it is determined that the tension monitoring system transmits the tensions by means of wireless communication.Firstly,the influence on wireless communication of mineral water,electromagnetic interference and installation scheme is explained.According to the electromagnetic wave theory,the quality of wireless communication and communication distance are estimated through specific calculations.The wireless communication scheme is further designed according to the calculation result,including determination of position of the tension acquisition device and the data receiving device,design of the signal path,design of the directional antenna,and so on.Finally,the wireless communication model is established,and the electromagnetic signal quality of the wireless communication is simulated by HFSS to evaluate the feasibility of wireless communication.In order to extend the service time of the monitoring system,after comprehensively consider the workflow and installation scheme of the monitoring system,an energy-saving strategy based on proximity switch and sleep mechanism is designed.According to the actual working conditions,the proximity switch based on the Hall effect is selected.The basic principle of the Hall effect is explained.According to the magnetic circuit principle and the characteristics of the paramagnetic material,a new structure suitable for installing the proximity switch on the scraper conveyor is designed.The structure of proximity switch was imported in Maxwell,an electromagnetic simulation software,which can verify its feasibility by calculation.The proximity switch combined with the sleep program on the software can realize that the tension acquisition device turns on the wireless transmitter when approaching the data receiving device,and then automatically enters the sleep mode in which power consumption is low after the data transmission is done.The tension acquisition circuit is the basic of the tension detection system.After determining the type of sensor,according to the actual demand and working conditions,the measurement circuit that has high sensitivity and temperature compensation is designed.A differential amplifying circuit and a filtering circuit are designed to process the output signal of the measuring circuit.According to the parameters of strain gauge and circuit component,the relationship between the tension of the scraper chains and the output voltage of the tension acquisition circuit is determined.Finally,the correctness of the circuit design is verified by the simulation of Multisim.After the hardware design is completed,the program of the tension monitoring system is designed.The tension acquisition device and the data receiving device of the tension monitoring system perform point-to-point communication through a network protocol named Basic RF.According to the actual needs,the data packets in the network protocol are redefined.The working process of the network protocol is described and the strength of the signal received by the antenna of data receiving device is analyzed.The application layer programs of the tension acquisition device and the data reception device are respectively designed.The application layer program of the tension acquisition device includes data acquisition,digitization,sleep processing,and so on.The application layer program of the data receiving device includes tension data calculation,communication with the host computer,and data visualization program.Finally,the tension monitoring system was fabricated.The basic functions of the tension monitoring system were verified by experiments,and the parameters such as power consumption of the tension monitoring system and data transmission-reception time were measured.A test bench to simulate the real working conditions of the coal mine is set up and the feasibility of the tension monitoring system is verified by experiment.Through the sensor calibration experiment,the measurement error of the tension acquisition device is reduced.Through the temperature stability experiment,it is ensured that the tension monitoring device is sufficient to accommodate the large range of temperature in coal mine.