Design And Experiment Of Fiber-optic WIM System

in recent years, with the increase of freight car in the highway, almost all freightvehicles are varying degrees of transfinite overloading behavior. In order to roadtraffic and road safety of life, road management requires a high precision and tofacilitate road dynamic measurement of vehicles weighing equipment. Based ontraditional methods of electrical measurement capabilities of anti-electromagneticinterference, low reproducibility, can not provide high enough accuracy. We use anadvanced optical sensor technology, the fiber-optic microbend sensing technologyhave high sensitivity, linearity, and anti-electromagnetic interference, corrosionresistance, low-cost, simple structure, easy to carry, etc., it not only to provideaccurate weighing of the main the weight of information, but also to improve theefficiency of the weight, accord with the national Intelligent Transportation System tothe requirements of the direction of development. Therefore, my thesis focus on thefiber-optic microbend sensing technology principle of dynamic weighing, measuringsystems for detailed design, focuses on the principle of weighing, structural design ofweighing system, and the experiment of weighing signal.1,The fiber optic microbend principle of WIMMicrobend fiber weighing system is used in fiber-optic sensing technologyMicrobend. It is the use of optical fiber to detect the Microbend vehicle wear and tearon the weighing system of the force. Optical fiber in the external force will have acurved, the result that some optical coupling from the core into the cladding, so thatthe ends of fiber-optic core to reach the light intensity decreased, resulting in opticalpower loss, which reflected the size of the disturbance caused by fiber-opticMicrobend physical changes. So by measuring the optical power changes, we candetect the weight of the vehicle value. The fiber optical microbend sensor is usuallycomposed of light, optical fiber, microbend modulators, optical detectors etc. plate, and due to tooth board by the outside world and change the role of parameterspace, the fiber also changes the degree Microbend, theoretical studies andexperiments show that fiber-optic light Microbend generated and external forceschange are linear approximation, Based on the principle ,we can achieve the vehiclesWIM.2,The Design of Weighing SystemBased on the weighing principle of Microbend optical fiber sensing technology,we design the structure of the entire weight system , the overall block diagram isshown in Figure 2, mainly composed of the fiber-optic sensor systems, signalprocessing systems, data acquisition systems, as well as the display systems.In the optical fiber sensing system, included the choice of suitable opticalmatching, LED light source, the corresponding light detectors, with emphasis on thestructure deformation Microbend designed. In this paper, a sawtooth-type device asthe design basis for the deformation, from the practical application of the startingweight of zigzag shape, the materials are deformed re-design. When a pressure sensoron the vehicle, the light detector detects the signal and weighing the correspondingoutput signal, signal processing, we adopted the signal amplification system formeasuring and processing, and then enter the number of systems, including datacollection, data processing , calibration, interface design, etc., using the mathematicalmodel will be converted into voltage signal and displays the weighing signal. In thispaper, a data acquisition interface card and software combination, as a dataacquisition card processing system to VC + +6.0 as development platform, all the wayto the software to achieve its function. In data acquisition and data processing in thedigital filtering of piecewise linear approach, weighing the correct signal values intothe interface will eventually be displayed, storage, and printed.3,experiment test and analysisUsing the device we carry out the experimental testing and analysis. Through thestandard calibration data, we tested the weighing signal and pressure, pressuredeformed position, sampling rate and other factors, and then all the conditions areoptimized ,we test the accuracy analysis.According to Linearization equation , concentration inversion formula can be when the sensor signal falls between 2 and 3, it will ( ) be iincorporated into the inversion of its type in the wheel of the weight of the currentvalue obtained by the display module directly displayed. We re-weight according tothe standard experiment, 10 sets of data obtained and compared with standard data, asshown in table 1. Figure 3 for measuring the weight of the calculated values with thestandard curve comparative data. From the table and figure we can see that the error iscontrolled in the range of 5% ,which achieve the measurement accuracy requirements.5,conclusionIn this thesis, based on the WIM principle of fiber-optic microbend sensingtechnology, we do the detailed design for the measuring system. We mainlyintroduced the principle of weighing, WIM system Microbend fiber design ideas andmethods, data acquisition and interface design etc, then do the experiment test andanalysis of the accuracy, as well as the factors affecting the weighing signal. finallythe error is controlled in the 5% range.