专业外语论文

The design of vehicle detector hardware system based oninductance coilXXXXXXCollege of Optoelectronic Engineering, ChongQing University, Chongqing,400044,ChinaE-mail:XXXXXXX@Abstract---Road traffic management will be dominated by Intelligent Transport Systems in the 21st century and road traffic information detector as the most important part of intelligent transportation system will control and determine the accuracy and timeliness of traffic management [1-2]. Inductor-based road traffic detector can have timely access to road traffic information, and it is currently widely used in the world[3].This paper carried out research on the focus of the inductor coil-based road traffic detector design. Buried coil was used as the inductor and combined with transistors to be a capacitance three-point oscillator circuit, and the inductance is changing with road vehicle, thus the oscillation frequency of the circuit was affected [4-6]. An oscillator circuit oscillation frequency directly reflects the passage of traffic vehicle conditions as follows. The oscillation circuit produces sine wave, and with the amplification shaping circuit the wave become standard square wave, and then acquired by the AT89S51 microcontroller. Then the information will be dealt, and send to the information processor STM32F103ZET6. The final result from STM32F103ZET6 will be sent to the computer control center via an Ethernet interface, thus the computer control center obtains information of the traffic where inductor coils is. Simulation tools as ORCAD and PROTUES were used to make sure that the circuits are right, and also Altium Design software was used to draw the schematic and PCB printed circuit board.Index Terms—Inductance coil, traffic detectors, AT89S51, STM32F103ZETI. I NTRODUCTIONhe inductor coil-based road traffic detector was researched and developed all the time as a common traffic monitoring system and the new kinds of inductor coil-based detector system were invented one by one. In recent years, the widely use of inductor coil-based detector also called out people’s enthusiasm to continuously research it. The inductor coil-based road traffic detector was used for many years before the microcontroller come out and shortages such as low processing rate, low automation, high power consumption, were very obvious and made great difficulties during the process of using. While a solution used to improve old detector system come out owing to the emerging of the microcontroller. There is a big significance to combine inductor coil oscillator circuit with microcontroller, because a new method of road traffic detector system was supported by the combination and the disadvantages of old inductor coil detector system were also overcame successfully. To use microcontroller to control the inductor-based road traffic detector circuit and process the dates and signals is the main purpose of this design. So a new road traffic detect method is developed in this paper, and the new method possesses advantages which the former systems never have.Knowledge of LC Oscillator circuit has a very great importance for the whole circuits design, and it is the basis of inductor coil-based road traffic detector. The study of theory of LC oscillator circuit has become an most important aspect of the early theoretical study. The only factor to influence the frequency of the LC oscillator circuit is L of inductor coil, and once the L increase, the frequency decrease. The question of whether processor can distinguish the car on the road from the changing of L has been thoroughly researched over the last few years. The answer is undoubted.The traditional inductor coil oscillator circuit is still used in this paper, and the microcontroller A T89S51 and STM32 were firstly used in this system. The whole system design were divided into five parts, including theoretical analysis, circuit design,circuit simulation,circuit plate and field test. The Altum Design was used to drawing circuit schematic and PCB. Before this, the key circuits were designed and simulated by circuit simulation tools such as orcad9.1 and protues7.5 to make sure that the key circuits are right. After the circuit was designed, in simulation tools, a small programmer was downloaded into the microcontroller to test if the circuits work well and if the oscillator circuit is right. Collection circuit of frequency data was made up by inductor coil oscillator circuit associated with A T89S51 and the change of frequency will be achieved by this part. Also AT89S51 will control LED lights to show the situation of road traffic and send the data to processer [7]. Because of high speed of processing and great communication performance, the processer is microcontroller STM32 in this paper [7]. The dates of frequency was indicator of the traffic passage, and according to the processing of microcontroller, the information of traffic will be achieved and shown on the computer screen, also the information will be send to computer center by RS232 bus[7]. Double-layer circuit board was produced by a PCB factory in Shenzhen, and it was used to do field test on the road in schoolyard. The test result show that the principle is practicable and the board can do work.In the following pages, we shall talk about the theory of the LC oscillator circuit and circuit design, and the simulate result and the test results.TFig.1. The model of the inductor coil-based road traffic detectorII. T HEORETICAL R ESEARCHAs we know, to the LC parallel resonant circuit the resonant frequency 0fequals to 1/(2 , whilethere will be a little deference in terms of the inductorcoil-based road traffic detector theoretical model. The model of the inductor coil-based road traffic detector can be simplified as Fig1. The vehicle was presented by the short circuit circle constituted by A R and A L , and the resonant circuit was composed by p R , p L and excitation power. Parameter M presents the influence between resonant circuit and short circuit circle. p i and A i werethe loop current [8]. We can get an equation from Fig.1p A p p p m di diR L M E i sinwt dt dt++= (1) 0p pA A A di di L i R M dt dt+-= (2) The equal impedance Z was achieved from (1) and (2)()()()()222222A A A A A A p p wM R wM wL Z R jw L R wL R wL ⎡⎤⎡⎤⎢⎥=++-⎢⎥⎢⎥++⎢⎥⎣⎦⎣⎦ (3) and from (3)we can know the equal inductor L is ()()222A p A A wM L L L R wL =-+ (4) For equation (4), p L is related to magnetic permeability of metallic materials, and ()()222]/[A A A wM L R wL + reflectseddy current effect.When vehicles cross the area of detector, the change ofshock frequency of oscillator circuit happens. The level ofthe change is decided by the material of the vehicle and thedistance from bottom surface to pavement. Among thefactors influencing shock frequency, the distance frombottom surface of vehicle to pavement is consideredprimarily because most vehicles have the same material tomake up their body, so that increase the distance thefrequency will decrease and reduce the distance thefrequency will increase. On the other hand, the distance is amain character of vehicle, for examples, the distance of carsis long, the distance of lorries is longer, the distance oftrucks is longest .Thus type of vehicle can be distinguishedfrom the change of frequency. The speed of vehicle isdifferent, considering the fast response of the circuit, wecan write a program in STM32 and calculate the velocity.When vehicle cross, variation of inductor change is()()21222AA A wM R L L L R wL =-=+ .What ’s more, M is related to properties of inductor coil,such as shape, number of turns of the coil, material and so on. Once installed on the road, properties of inductor coil is certain.Suppose length of inductor coil is 2a, width is also 2a, number of turns of the coil is one, and induced currents is0I I sinwt=, so that electromagnetic induction is B and()23/2220(2/)[/]B u a I a d π=+ , and magnetic flux acrossvehicle is()3/24220(8/)[/]BS u a I a d π∅==+ .Combine B and∅,M will achieved,()3/24220/(8/)/][M I u a a d π=∅=+ . From the equation, we are certain that M and L wasdecided by the distance d.Furthermore, some traffic information parameters will be got. First of all, the measure method of velocity can be obtained by the equation as /i i V l t =. l is the width andi t is the time which is waste by vehicle across the inductorcoils and i t can be achieved according to checkingwaveform of frequency signal by microcontroller. Secondly, number of vehicles per unit time Q can be calculated by /Q N t =.N is the total number of cars during t hour. Finally,traffic density /()/()/N S Q T v T Q v ρ==⋅⋅=, v represent mean velocity of vehicles. It is noteworthy that more traffic information parameters can be obtained from the frequency information with microcontroller. About circuit design, there are several key points to note. First, signal shaping circuit is necessary for the detector system, because signal from short circuit is sine so that it is not fit for the microcontroller [9]. Thus the function of signal shaping circuit is to translate the sine signal to squarewave before sent to the microcontroller. Next, the RS485was used to communication between the two microcontroller, because it has good resistance to interference and fit for short distance communication [10].Finally, the key circuit should be tested and verified andthis will be talked in experiment description.III. E XPERIMENT D ESCRIPTIONSeveral experiments were did in the inductor coil-basedroad traffic detector system design. There are two parts, oneis simulation experiment and the other is field testexperiment. In simulation experiment part, the orcad9.1was used to design and test capacitance three-pointoscillator circuit and signal shaping circuit, the finalexperimental results guarantee that the design is right. Andwe also use the protues7.5 to guarantee correctness ofcircuit of microcontroller. We write a short program anddownload with software protues7.5, and an excellent resultwas achieved. So we design the whole circuit and PCBwith Altium Design, and send PCB document to a factory.After we got circuit board ,we did the experiment to verifymthe feasibility of the system. We put the inductor coil on the road in our schoolyard and connect all circuit and computer, then download a program written by classmate Xiong [11]. Results of operation show the information of velocity, number of vehicles per unit time and traffic density in computer screen. However, the number of vehicles per unit time is not correct sometimes.IV.C ONCLUSIONThe inductor coil-based road traffic detector system was designed, tested and verified by us. We are sure that this system is practical and it can be used in traffic management in future once it is improved. In the system, we design the capacitance three-point oscillator circuit and signal shaping circuit to achieve the sine frequency signal and transformed it into square signal. We also design the microcontroller circuit combining the microcontroller and front-end processing circuit, to process the received square frequency signal. The correctness of key circuit is certain after simulation by software. Then we draw the whole circuit schematic and PCB with Altium Design which is upgrade of DXP2004, and send PCB document to a factory. In the experiment, simulation is successful, but the there is something wrong with system in field test. After a period of reflection,the reason is due to the interference outside and inside the circuit board. We guess that the system was disturbed by electromagnetic interference in schoolyard because there are many instruments in the school yard and Wi-Fi signal exist everywhere, also our wires and circuits have no shielding measures. And there is also another possibility that something wrong is likely in the circuit board design and wiring. It is my first time to draw PCB, so I’m lack of experience and I’m not sure whether there is something wrong in my PCB. While, generally speaking, the system has a huge potential to be explored and it combine old inductor coil detector system and modern microcontroller, so we will continue to research and check the places where may be wrong and make the system perfect in the field test.A CKNOWLEDGMENTThis thesis would not have been possible without inspiration and helps from my teacher professor ZhiminLi and my friend ShengmingXiong. Especially, a lot of advising and suggestions about my thesis and design was given by professor Li. My friend ShengmingXiong also gives me lots of suggestion about the program.In addition my thanks will be given to professor GangChen, he help me learn lots of knowledge about English writing. And my acknowledgements also will be given to my classmates ChaoZhang and YihuangFang who help accomplish the PCB drawing and the field test.R EFERENCE[1] Z.Y.Liu, Intelligent Traffic Control Theory and Application,Beijing:Science Publishing House,2003 [2] D.S.Lv, Detection of the vehicle and its development,Computer andCommunications.1999,17(2):28-40[3] H.M.Feng, B.M. Dan, N.P. Hu, Design and implementation of loopvehicle detector , Journal of Qingdao University, 2005, 26(5):448-451[4] Y.G.Sui, Z.X. Li, X.M. Liu, Y.Z. 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