| With the rapid development of China’s economy,people’s living standards are improving day by day,and the total mileage of highways and car ownership are also increasing year by year.Road roughness is closely related to people’s lives.It is not only the research content of road engineering,but also the research hotspot of vehicle engineering.Therefore,it is very important to accurately describe road roughness.International roughness index(IRI)and power spectral density(PSD)of road roughness are two commonly used indicators to describe road roughness.The former combines vehicle response with road roughness characterization and is mostly used in road engineering,while the latter describes road wavelength distribution in frequency domain and is mostly used in vehicle engineering.Among the models of PSD of road roughness,the PSD power function model of road roughness has become a standard model reflecting the road roughness information.Therefore,it is necessary to introduce the IRI into vehicle engineering,owing to the attribute of vehicle dynamic response,and apply it to road roughness PSD identification.This paper focuses on the identification of PSD power function model of road roughness.Based on the description of time and spacial as well as frequency domains of international road roughness index,combined with vehicle vibration response,a new solution of the identification of PSD function model of road roughness is proposed.The aforementioned solution is validated by experiment.The main contents of this paper are given as follows:(1)Description of IRI in time and spacial domainsThe 1/4 vehicle vibration model is established,the solution process of IRI in time domain is deduced,and then the description of IRI in time domain is given.The transformation of IRI description from the time domain to the spacial domain is realized by using the transformation formula of the variables from the time domain to the spacial domain.Finally,the descriptions of IRI in time and spacial domains are compared.A new solution for IRI calculation based on the precise integration method(PIM)is proposed and then validated and analyzed through the measured pavement data.(2)Description of IRI in frequency domainThe statistical characteristics of road roughness and vibration response of vehicle linear system are expounded.Based on the digital characteristics of a special random variable,the description of IRI in frequency domain is given,including two new concepts of time frequency IRI and spacial frequency IRI.A road classification method based on IRI is proposed.(3)New method for describing PSD power function model of road roughnessThe expanded international roughness index(IRIE)is defined.A new method for describing PSD power function model of road roughness is proposed by using IRIE.Based on the model of road roughness in frequency domain,the model of road roughness in time domain reconstruction and the measured road roughness data,the correctness and validity of the new method for describing PSD power function model of road roughness are analyzed and verified.(4)Research on the relationship between vibration response of a planar car and two IRIEsA planar vibration model of a car with 6 degrees of freedom(DOFs)is established.Twenty vibration responses of the car at the speed of 80 km/h are simulated by using the generalized single-point pseudo excitation method(PEM).Based on the joint simulation of Isight and Matlab,the influences of the operating conditions and structural parameters of the planar car on the relationships between the vibration responses and the IRIE are analyzed.The relationships between the vibration responses and two IRIEs are studied through correlation and regression analysis.(5)Research on the relationship between vibration response of a spacial car and two IRIEsConsidering the roll motion of a car,a spacial vibration model of the car with 11 DOFs is established.Thirty-nine vibration responses of the car at the speed of 80 km/h are simulated by using the multi-point PEM,which is applied to a four-wheel pseudo road excitation construction.The influences of the operating conditions and structural parameters of the spacial car on the relationships between the vibration responses and two IRIEs are analyzed.The relationships between the selected vibration responses and two IRIEs are performed.(6)Identification of power function model of road statistical characteristicsBased on the research of the relationships between the vibration responses of the car and two IRIEs,some car vibration responses available for the identification of PSD power function model of road roughness is selected.Combined with the new method for description of PSD power function model,a new solution for the identification of PSD power function model is proposed.The identification solution is verified to be correct and effective through experiment.The innovations in this paper are described as follows:(1)A new solution for calculating IRI based on PIM is proposed and compared with the CEN standard and the ASTM standard.Based on the measured road data,the new solution proposed in this paper is superior to the ASTM standard and the CEN standard.The new solution for calculating IRI proposed in this paper can fully take into account the calculation accuracy,efficiency and stability of IRI.It lays a theoretical foundation for the revision and unification of the IRI calculation standard,people’s understanding of IRI,and the application of IRI in road engineering and vehicle engineering.(2)Two new concepts of time frequency IRI and spacial frequency IRI are proposed.Based on the stochastic vibration theory and the stochastic mathematics theory,a simple mathematical method is used to establish the description of IRI in frequency domain.Combined with the two descriptions of the road surface roughness PSD,two new concepts of time frequency IRI and spacial frequency IRI are defined,which provides an approach for the measurement and estimation of the IRI in frequency domain.The correctness and validity of the description of the IRI in frequency domain are verified by means of median filtering method and the measured pavement data.The problem of inconsistency between the results of establishing the relationships between the IRI and the road roughness PSD by using theoretical derivation method and regression analysis method is solved.(3)A new method based on IRIE for describing PSD power function model of road roughness is proposed.A new concept named IRIE is defined.Based on this,the process of calculating parameters of PSD power function model of road roughness is derived,and a new method of describing PSD power function model of road roughness is given.In frequency domain,it is proved that the IRIE combination }IRIIRI{xEy E,and the parameters of PSD power function model of road roughness are equivalent.In time and spacial domains,the IRIE combination }IRI,IRI{E40is recommended to describe the PSD power function model of road roughness.(4)A new identification solution for PSD power function model of road roughness is proposed.Based on the analysis of the relationship between vibration response and IRIE,the first regression model and the second regression model based on the RMS values of the vertical acceleration of the unsprung mass center of the front axle and the rear axle and the accumulations of the front and rear suspension stroke divided by the travel distance are established,respectively.The experimental results showed that the scheme was effective.Compared with the previous approaches of the identification of PSD power function model of road roughness,the new solution proposed in this paper can be carried on for the test vehicle with the unknown properties and has the advantages of online identification,small calculation amount,high efficiency,low cost and simple identification system. |
