| With the rapid development of China's national economy and the heavy investment and construction, overloading of vehicles becomes a more and more common phenomenon in highway. Overload transportation in highway causes great damages to social and human property, thus overload governance has become urgent. Dynamic Vehicle Weighbridge is in need to install on the highway to get the message of the weight of vehicles and investigate illegal vehicle, which can effectively control the phenomenon of overloading.In the current dynamic truck scale detection system,vehicles go through truck scale at a certain speed, so weighing process is dynamic. In the process of truck moving, many external factors effect on weighing,in which the impact of speed is very large. Therefore, it is necessary to compensate the weight of vehicles according to the speed. With pulse-type infrared launch tube sensor, this device measures and calculates speed and acceleration of vehicles which go through the scale platform. The data of velocity and acceleration are information to build the mathematical model of relationship between speed and weight. Through the mathematical model we can compensate the weight of vehicle. The device can send speed and acceleration data to the host computer and local meter by the dual serial interfaces, which provide data for graphics, analysis, and weighing compensation, and show the result of weighing on local meter.This thesis focuses on describing the theoretical methods to measure time when the vehicles pass through the 79 different sections of the weighing platform, and putting the theory into practice, which means to collect and process the time signal by microchip and to calculate the on-line speeds at multiple points and the accelerations at multiple sections, in order to collect the data. In the meantime, the measured data would be transmitted by the high-level language Visual Basic programming into the upper monitor to analyze, draft and store.The article, which starts from requirement of the project, is finally determined to measure speed and acceleration by carrier-based infrared speed sensor by several common measurement methods of contrast and analysis. The article in turn tells the method to achieve and its optimum design of the structure, and then mainly analyzes the ability to resist light interference, which can make sure the device can be used in harsh environments in the field. The infrared sensors of receiver and transmitter can be separated, the distance of separation is five meters. The device gets signal with analog switches to select, which reduces the use of MCU port and improves the utilization of MCU.Secondly, the article describes the process of the microcontroller to the pulse-type signal. It is can not judged whether there is a vehicle passes through the scale platform according to the change of the signal. It must be judged in accordance with the characteristics of the pulse signal by delay algorithm, and distinguishes the signals between the one generated by vehicles'passing and normal pulse signal. 485-bus structure is adopted in the communication, so the staff can observe the running condition of the movement from the vehicle in the operating room. The function of self testing and encryption of the device can also make it work stable and reliable and keep the data safe.At the last part, the thesis recommends the method and the standard to test the device, and suggests the problems that need attention at different parts during the process of assembling and testing, and introduces in detail the method to test and measure the assembled system as well as matters to be attended to when the object taking place for the vehicle tire is moving. The device, connected to the upper monitor through the serial interface, is designed by the upper monitor software to reproduces the motion trails of objects passing through the weighing platform. Afterwards, the motion trails in the upper monitor would be observed to determine the accuracy of the device. |
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