1.2.2 Data Acquisition of Road Unevenness
For the determination of the spectral power density of road unevenness, the longitudinal section of the road is taken into consideration. For the measurement of road unevenness different measuring procedures were developed, which are partially adapted to both road construction as well as for automotive applications. About 70 different unevenness measuring procedures are available.
An accurate measurement of the road surface is possible only with subgrade level and levelling instrument. Since the measurement of long distances is time intensive and disturbs the free flow of traffic etc. these approaches are not widely used in technical application. The so-called geometrical unevenness measuring instruments were developed mainly for application in road construction.
The measuring procedures used in automotive technology, function according to the principle of the dynamic unevenness measurement. During these measuring procedures the reference level is not fixed, but derived continuously from an average value of the road unevenness, formed over a sufficiently long period of time. The figure shows a test vehicle equipped with devices for the measurement of road unevenness. The measuring task is divided into two sub-tasks:
Measurement of the change in distance Δz between road surface and reference point on the vehicle body.
Measurement of the vertical body movement zA at the points of reference.