# Conceptual Design and Preliminary Verification of Distributed Wireless System of Weigh-in-Motion
###### Abstract  
In this paper, the concept of a distributed wireless system of weigh-in-motion is proposed. A wireless sensor for weigh-in-motion (WIM) based on piezoelectric materials is designed. The corresponding prototype for indoor testing is made according to the design. It aims to realize the main functions of dynamic pressure sensing, charge signal amplification and conversion, wireless signal transmission and reception, etc. The material properties of the mechanical properties and the piezoelectric properties in the analyses are provided in detail. Through the indoor test platform, the feasibility of the wireless sensor for WIM designed in this paper is preliminarily verified, which provides a basic tool for the realization of the distributed self-powered wireless system of WIM in the next step. weigh-in-motion; conceptual design; distributed system; wireless transmission +
Footnote †: journal: Applied sciences  
such sensors need to be supplemented to reduce measurement errors. [PERSON] et al. [11] estimated the performance, especially the durability, of the piezoelectric WIM sensors using quartz. [PERSON] and [PERSON] [12] studied the analytical model and actual performance of the railway track WIM system based on piezoelectric sensors. [PERSON] et al. [13] analyzed the effect of temperature on the error of piezoelectric sensors through indoor and field tests. [PERSON] et al. [14; 15] analyzed the performance of WIM sensors using three piezoelectric materials, quartz, piezoceramic, and PVDF, through field measurement and discussed the influence of air temperature and vehicle speed on these three piezoelectric sensors. [PERSON] et al. [16] developed sensors for the WIM system based on the advantages of low-temperature sensitivity, high reliability, and simple structure of piezoceramic. [PERSON] et al. [17] established the theoretical model of the strip piezoelectric WIM sensors considering the effect of pavement deformation and emphasized the importance of considering the viscoelastic characteristics of structural layers of asphalt pavements by comparing them with measured structures. [PERSON] and [PERSON] [18] performed field observations of flexible asphalt pavements and discussed the impact on weighing results under vehicle speed and temperature variation. They explained that the distribution differences between vertical and horizontal stresses in the pavement structure primarily cause measurement errors. Currently, these WIM sensors embedded in the road actually measure the wheel load which is directly applied on the sensors. However, in the motion state of actual vehicles, the vehicle vibration is caused by the defects of pavement deformation, smoothness, or pits; thus, the pressure that the wheels applied to the pavement measured by sensors is not static, but dynamic and affected by various factors. Therefore, the existing WIM system needs to be adjusted according to the parameters on site through actual vehicles [7; 19]. [PERSON] et al. [20] and [PERSON] and [PERSON] [21] also present a detailed discussion about the requirement of WIM for pavement smoothness. These works are to calibrate the parameters of the WIM system through on-site or indoor tests. In fact, the whole WIM system is actually regarded as a black box. Without establishing a real theoretical model of the WIM system, empirical calibration parameters have difficulties in promotion and application; hence, calibration parameters are specifically set for each WIM station. [PERSON] et al. [22] carried out a series of MTS tests to verify the theoretical model of the multi-layer structure of PZT sensors. The experiment results indicated that the loading frequency plays a prominent role in identifying the load magnitude. Moreover, the model of PZT sensors neglects the dynamic effects from the load which neglects the differences under the same application at different frequencies.