| Wireless detection system is an important tool for structural health detection.The traditional manual detection method often has large subjective deviation,low detection frequency and high cost.The wireless detection system,which has the characteristics of low cost and convenient installation of wireless sensor networks,has the advantages of covering a wider range of structural facilities to be detected and quickly obtaining structural health data.The core content of wireless detection system is data perception and data transmission.Therefore,taking the wireless bridge collision detection system as an example,this paper studies the sensor correction and ad hoc network protocol of the wireless detection system.Firstly,this paper discusses the research background and significance of wireless detection system,and expounds the research status of wireless detection system at home and abroad.On this basis,the main research contents are as follows:(1)According to the application requirements of bridge collision detection,a set of software and hardware of wireless bridge collision detection system is designed and implemented as an experimental platform for follow-up research.(2)The parameters of the wireless detection system are designed to meet the hardware requirements of high-speed networking.The sensor correction method is studied,and a sensor field correction method is proposed to improve the accuracy of the sensor.This method has the characteristics of on-site correction,fast correction speed and no external equipment.(3)Wireless node transmit power,receive power and other parameters are often used in link quality estimation,node positioning and other low-power wireless network support technologies.The accuracy of these parameters is very important for the operation of the upper layer protocol,and the experimental data show that the measured values of these parameters are different from the nominal values.If the difference between the measured value of transmission power and the nominal value can reach more than 6d B.And the differences between different channels are not the same,while the same channel has approximately the same difference.In addition to the difference in the received power,there are also multiple nonlinear regions,that is,the same measured value corresponds to multiple actual input values.Two receiving power correction models are designed.The maximum error of the look-up table model is 3.6dbm,and the cumulative probability reaches 90%when the error is 2.05dbm;The maximum error of the linear fitting model is 5.5dbm.When reaching the same cumulative probability,the error is 4.29 dbm.Although the linear fitting error is larger,its storage overhead is 47 times lower than that of the lookup table.(4)As an important supporting technology of wireless sensor networks,the importance of wireless link quality assessment does not need to be repeated.In order to improve the working efficiency of ad hoc network protocol,a lightweight link quality estimation method based on simplified model is designed.The model estimates the link quality with parameters such as received power and packet rate.The received power used here is corrected by the above research.Compared with the logistic regression model,the RMSE of this model is reduced by 31.52% when the packet length is 82 bytes.Compared with the polynomial model,the RMSE of this model is smaller,reducing 13.61% ～ 20.39%.(5)Based on the above research,this paper designs an adaptive gateway selection method.The node adaptively selects the communication gateway according to the wireless link quality estimation method to improve the data transmission efficiency. |
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