# Conceptual Design and Preliminary Verification of Distributed Wireless System of Weigh-in-Motion
## 5 Conclusions  
In this paper, the conceptual design of distributed self-powered wireless system of WIM is proposed. A new wireless sensor for the WIM of road vehicles based on piezoelectric ceramics is designed and fabricated to measure the dynamic load of vehicles under normal driving conditions on the road. The collected signal is transmitted to the weighing station through a wireless transmission module. The main research work and results of this paper are as follows:  
1. PZT piezoelectric ceramics were selected as the sensing material. The pressure sensing element was designed and fabricated in parallel to improve the piezoelectric output. The mechanical structure of the vehicle WIM sensor was also designed according to the requirements of the weighing sensor equipment on the road;
2. The circuitry required for the WIM sensor was designed and the prototype was built. It mainly consists of the charge conversion amplifier with a filtering function, the power supply circuit, and the A/D conversion function programmed using the STM32f103 rct6 microcontroller. Meanwhile, the STM32f103 rct6 microcontroller was combined with the wireless RF module NRF24L01 to realize the wireless transmission and reception of pressure signal data;
3. The signal response of the wireless WIM sensor under cyclic loads peaking at 20 kN, 50 kN, and 80 kN was verified by a high-performance universal testing machine. Preliminary results show that the mechanical and circuit design of the whole structure is reasonable and effective. It means the collected signals work well;
4. The piezoelectric sensing unit (Figure 3) can provide self-power (under the 5 Hz load of 20 KN, 50 KN, and 80 KN, respectively, the obtained peak voltages are 320 mV, 713 mV, and 1178 mV, respectively), but the electricity provided is very limited, which cannot provide the power of wireless transmission module (Figure 9). It means that the'self-powered' module is conceptual at this stage and has not been totally realized yet.  
The next step will be to implement the self-powered module with the road test. A new distributed self-powered wireless system of WIM would be optimized by adjusting the number and the arrangement of sensors. Machine learning would also be applied in the inverse analysis of vehicle travel speed and axle weight.  
Y.W.: Conceptualization, Methodology, Software, Validation, Investigation, Formal analysis, Visualization, Writing--original draft; L.G.: Conceptualization, Writing--Review & Editing, Funding Acquisition. B.B.: Conceptualization, Writing--Review & Editing, Funding Acquisition. J.P.: Conceptualization, Writing--Review & Editing. Q.F.: Conceptualization, Writing--Review & Editing. R.X.: Conceptualization, Methodology, Formal analysis, Writing--Review & Editing. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the \"Pioneer\" and \"Leading Goose\" R&D Program of Zhejiang (No. 2022C01143) and the National Natural and Science Foundation of China (Nos. 12072097, 12272335). This work was also supported by the ZJU-ZCCC Institute of Collaborative Innovation (No. ZD)G2022002).  
The authors declare no conflict of interest.