Research Of Dynamic Weighing System Based On PVDF Sensors

The overloaded and overmarged vehicles have seriously affected the security andshortened the service life of our roads and bridges. Transport department proposedhigher and higher demands for Dynamic weighing (WIM) in order to strengthen themanagement of overloading. The currently widely used Weight-in-Motion system isweak in high-speed detection, sensitivity and accuracy. Studies have demonstrated thatthe vehicles’ wheelpath lateral distribution on the cross-section of the bridge is animportant parameter for bridge load. And it affects the structural behavior of the bridge.Therefore, it is of great significance to establish a high speed dynamic weighing systemin protecting the safety of important roads and bridges, which can identify thewheelpath lateral distribution and have high sensitivity.The thesis develops a Piezoelectric WIM system which can detect the lateral positionof the vehicle through rational emplacing manners of PVDF sensors with betterdurability and stability. It’s the first time to use three sensors by "N" distribution layoutin the driveway. Based on the Labview program platform, it designs the analysissoftware of the system. The Dynamic weighing system can not only improve thedynamic weighing accuracy, but also can detect the wheelpath lateral distribution.Beyond that it provides a new, simple and practical method to investigate the trafficdata for transport agencies.The thesis proceeds in the following way:Firstly, it elaborates the piezoelectric principles and characteristics of PVDF sensor,and introduces the problems in installation and application to ensure the accuracy of theWIM system. The change of environmental temperature cause the variation of sensorpiezoelectric constant, volume resistance and elastic modulus. Then the weighing resultwill be wrong. For these problems, the thesis recommends a temperature compensationformula.Secondly, considering the additional dynamic load of vehicles, it proposes a areaintegration method which is superior to the peak method in identifying and calculatingthe parameters of vehicles based on the PVDF sensors.Thirdly, it designs the sensors’ laying way in order to develop a dynamic weighingsystem which can detect the wheelpath lateral distribution. It programmes a analysissoftware of the system by Labview, which can analyze the signal to get the traffic data,including gross vehicle weight, axle load, wheel weight, wheelbase and wheelpath lateral distribution, etc.Fourthly, it designs experimental project in the laboratory to verify the system’sfeasibility and the algorithm of the developed dynamic weighing system. With thebackground of Zhanchuan River Bridge in Huangshan, it proceeds field tests to verifythe system and has a detailed discussion of the problems we should pay attention to ininstallation of the PVDF WIM system. In laboratory experiments and field tests thesystem performs in a good stability and reliability, meanwhile the precision meet theengineering requirements.