Design Of Multi-objective Ultrasonic Positioning System At The Scene Of The Substation Operation Maintenance

Ultrasonic positioning technology is one of the critical technology on the indoor complexity environment, which is mainly used for small-scale target-location and tracking. This technology is suitable for vehicle parking management, intelligent care in nursing homes, materials management in the warehouse, operation and maintenance of substation and so on. With the limit of positioning accuracy, positioning range and variety of obstacles, mature applications in these areas above are rare.This thesis is based on ultrasonic technology, which in accordance with TDOA(Time Difference of Arrival) indoor positioning theory, using advantages of ultrasonic transmission detection to solve the critical problem that measurement accuracy is not high. Meanwhile, using the technology of pseudo- random noise code to achieve multi-target identification and precise positioning, and develop target location system in substation, to solve the problem of personnel location management.In this thesis, which firstly summarize the principle and basic theory of ultrasonic positioning, then selected TDOA location method as the design principles of indoor positioning system. For the problem of multi-objective distinction, this thesis introduced the pseudo-random coding techniques in detail. Through the use of pseudo-random code’s good autocorrelation and cross correlation, adopt the method of direct sequence spread spectrum, it can not only solve the problem of multi-objective distinction, but also alleviate the impact of multipath interference.The design of Multi-objective Ultrasonic Positioning System, include three parts as follow: Mobile node, Positioning node and Wireless base station. The base station is responsible for the control commands issued and time synchronization signal. Positioning terminal preprocess the ultrasonic signal and transmit it to the air. Then acoustic positioning sensor node receive the ultrasonic signal, and transmit the data of ultrasonic signal arrival time to backend server, backend server calculated the three-dimensional coordinates by using of TDOA theory.Each parts hardware circuit is based on STM32 processor. Some related components as follows: ultrasonic transmitter sub-modules, wireless sub-module, power management module, temperature and humidity measurement sub-module, Ethernet communication and POE module. Sub-module is used to wireless data transmission; POE module power for equipment; temperature and humidity sub-module collect environment’s temperature and humidity data, for the purpose that correcting the speed of sound.For the problem of electromagnetic interference, signal fading and multipath interference and other issues in ultrasonic positioning system, this thesis made a detailed analysis and designed the anti- noise power supply circuits.The main achievement of this thesis are as follows:1.Using software radio technology roadmap to deal with the sending and receiving of ultrasonic waves, then put forward a practical ultrasonic positioning transmission technology.2.Using the technology of pseudo- random noise code to achieve multi-target identification and precise positioning, and develop target location system in substation. It can provide technical reference for other systems with multi- objective distinction needs.3.Using a high-precision synchronization technology to build a master-slave clock synchronization network, which can effectively control the clock error of various subsystems within 10 microseconds.