Design And Application Of Position Encoding Sensor Based On Electromagnetic Induction

In a transportation system, a magnetic stripe is paved along the orientation of the tunnel, whose shape like a tree, the tow car can move along the stripe. In order to find the right way to the goal station, the tow car must know where it is and where the goal station is. Then can go along the way automatically. Combined with common positioning methods and the actual work environment of the tow car, this paper designed a novel contactless position sensor, and successfully applied it to identify some special points in the channel.Electromagnetic Induction Position Encoding Sensor(EIPES) applies Magnetic Induction Communication(MIC). MIC has a short effective range, so it can be used for positioning. EIPES has two parts, the transmit one and the receive one. In the transmit part, high frequency oscillation signal is modulated by a special coded signal and then carries the position number out. In the receive part, the signal coming from the transmit part is demodulated by circuit, and then be decoded.A novel encoded mode is proposed in this thesis, which uses the different interval of two pulses. Specifically the pulse duration is 1T; 1T interval indicates that the bit is ‘0’ and 2T interval is ‘1’. In addition, a start bit and a stop bit are set in serial communication, which are indicated by 3T and 4T.The transmit part is composed of six circuit modules: dial module, encoding module, driving signal generation module, driving signal isolation and synchronization module, power amplification module and signal transmission module. The first two modules constitute a modulation circuit, and the last four modules constitute an oscillating circuit. The encoding module uses its high and low levels to control the enable port of the driving signal generation module, thus realizes the modulation. LC resonance circuit is driven by a rectangular pulse signal, which can be replaced by Fourier series. The amplitude-frequency response of the LC resonance circuit is analyzed, and it indicates that the signal of L can be regard as the response of the fundamental component.The receive part is composed of seven circuit modules: inductive module, amplification module, full-wave rectification module, detection module, wave shaping module, decoding module and communication module. The first five modules constitute a demodulation circuit, who converts the signal coming from the transmit part to square wave signal. The position number can be obtained after a MUC’s decode. The receive part supplies a communication port by applying a RS-485 BUS, and a software interface by applying a communication protocol of MODBUS, so it is standardized.EIPES is used to indicate the branch of the tree shape path. The car reads the potion number by the SYSBUS directly, and uses mapping tables to query the work station’s number and the path style, which simplify the logic of the control system. At last, a real-time location method using the car’s velocity and the operating system time is researched in the thesis.