The Design Of The Acoustic Signal Based Underground Cables Anti-damage Early Warning System

The underground cable not only carries the power transmission,but also the important electrical signal transmission network such as the network communication.Due to the complex dustribution of the underground cable as well as the lack of the supervision,the underground cables are frequently destroyed caused by the excavation equipment in the process of city construction,which is a difficult problem to be solved in power supervision department.According to the investigation and relevant units of feedback,the main excavation equipment includes the excavator,cutting machine,electric hammer,hydraulic hammer and so on.The protection of underground cable damage can be strengthened by early warning.In this paper,an early warning system based on acoustic signal for underground cable damage protection is proposed.The system employs the AM3354 as the main controller and equips with the Linux system.Moreover,the acoustic signal conditioning,collection,storage,transmission,processing and communication are realized by hardware and software design,which provides a stable operation environment for the embedded algorithm.The main contributions are listed as follows.(1)By analying the characteristics of the excavator equipment,we use the high-sensitivity capacitive microphone to carry out the conversion of sound and electricity then the Howland precision driving constant current source circuit is designed.The acoustic signal conditioning is conducted by the audio signal amplifying circuit,the active Butterworth low-pass filter circuit and the ADC differential signal driving circuit.Finally,the analog signals are converted into digital signals by the ADS1274 sampling circuit.(2)An embedded hardware circuit system with AM3354 as the main controller is designed.The power management chip of the digital circuit system uses TPS65217 C to provide multichannel power supply voltage.The DDR3 memory circuit chip uses the IS43TR16256,which provides 256 MB data cache space.The NAND Flash storage circuit chip uses MT29F8G08 ABABA to provide the storage space of the 1GB program.The EEPROM storage circuit chip uses DS2460 S to provide the system parameter information storage space of the 64 KB.The SD card storage interface circuit is designed to store the sampled sound data.The system designs various external communication modes,including 485 communication,Gigabit Ethernet communication,USB2.0 communication,UART communication and GPRS communication,so as to realize data and early warning information transmission.(3)We empolys the four layer structure design to realize the embedded PCB hardware circuit,and the signal Integrity simulation and analysis of AM3354 and IS43TR16256 high speed interconnect signal channel is accomplished by high speed circuit design method.Then,employing the comparison of the simulation results,the appropriate matching scheme is selected to optimization the PCBrouting,which can improve the stability of communication and reduce the power consumption of the circuit.PDN impedance simulation is carried out on the key power network plane of the embedded circuit PCB to realize the rational distribution of decoupling capacitance and optimize the decoupling design of power supply system.(4)For the softwares,the operating system of the Linux2.6 version is transplanted.An efficient DMA automatic storage program,an IPC driver,and a GPRS communication program are designed to be triggered by hardware.The recognition and location algorithm is transplanted into the system task to identify the equipment and locate the azimuth.(5)For the experiments,we design and optimize the contrast tesst,including the analog power ripple test,audio signal gain setting,transmission line length test and DMA trigger signal test.Through a large number of outdoor experiments,the amplitude and spectrum data of the acoustic signals under the different distances for the four devices are collected,and the results of recognition and location are compared and analyzed.