Study On Method Of Measuring And Evaluating Pavement Roughness By Smartphone

Pavement roughness is an important index in pavement performance.An excellent road surface not only guarantees the riding quality of the driver and the passengers,but also reduces the damage to vehicle and pavement due to tire dynamic load.The measurement methods of pavement roughness usually include the cross-section,response-type and subjective evaluation method.The cross-section method is usually accurate,but its convenience is poor,and it is time-consuming and labor-consuming.On the contrary,the response-type method is convenient,but its index doesn't build a relationship with the profile elevation data of pavement,and it also requires specialized equipment.The subjective evaluation method requires enough manpower,and it is easily influenced by subjective factors.Therefore,an inexpensive and convenient measurement method or device is needed.And its measurement result should be associated with the profile elevation data and a general roughness index(International Roughness Index).For this purpose,a new method was applied to measure and evaluate pavement roughness by the smartphone.Firstly,a client application which can be installed on a smartphone was developed based on Android Studio 2.0.When it was developed,the main programming language was Java 8.The developing process included writing source code and the construction of application installation package.And the construction of application installation package included the compilation of source code,conversion,packaging,signature,and optimization.Secondly,a preprocessing method of the acceleration data was proposed.The process was divided into two steps.Firstly,the data trend was eliminated by least squares,and then the data were denoised by discrete wavelet transform method.The results showed that the preprocessed acceleration data coincided with the baseline of time axis.And the noises in the original signal were effectively eliminated,meanwhile,the useful information was preserved.The process has a good denoise effect.Next,a method of identifying the physical parameters of the 1/4 actual vehicle model was proposed.The theoretical relationships between the physical parameters and the modal parameters in the vibration equations were obtained based on the complex modal theory.The drop experiment of the vehicle front wheels was carried out.With the least squares frequency domain method,the modal parameters in the frequency response function were obtained.According to the theoretical relationships and the modal parameters obtained,five physical parameters in the vibration equations of the 1/4 actual vehicle model were obtained by genetic algorithm.Afterwards,the relationships between the acceleration data and International Roughness Index(IRI)were obtained by the theoretical method.Firstly,the dynamic equations about the forced vibration response of the 1/4 actual vehicle model were established.According to the transfer matrix method and the physical parameters obtained,the variable transfer matrix and coefficient matrix of the vehicle model could be calculated.And the theoretical relationships between the state variables and the profile elevation data at the adjacent moments were established.Therefore,the profile elevation data could be obtained based on the vertical acceleration data collected by the smartphone.Meanwhile,according to the specified standard vehicle parameters,the variable transfer matrix and coefficient matrix corresponding to the 1/4 standard vehicle model can be obtained.As a result,IRI could be obtained on the basis of the profile elevation data.Finally,the verification tests of acceleration data acquisition were carried out on the area around the Qujiang River,and the verification tests of theoretical calculation method of IRI were carried out on the Xitong Expressway and Xiyu Expressway.In the verification tests of acceleration data acquisition,the smart phone and three unidirectional accelerometers were used simultaneously to collect the three-directional acceleration data of vehicle vibration.Based on the caculated total weighted root-mean-square accelerations,the accuracy of the data collected by the smartphone client application were verified.In the verification tests of theoretical calculation method of IRI,the test results of IRI carried out by smartphone were compared with the results tested by Shaanxi Highway Construction Group co.LTD,and the validity and accuracy of the IRI calculation method based on the vertical acceleration data of the smartphone were verified.According to the total weighted RMSA obtained,the riding comfort of pavement could be evaluated.According to the IRI obtained,the riding quality of pavement could also be evaluated.In this way,pavement roughness could be evaluated.