Automatic Levelling in Road Construction

Abstract

SUMMARYThe fulfilment of today's demands for particular pavement course thicknesses and a particular evenness in the construction of road surfacings is one of the main tasks set to road building equipment. This aim can be reached through the use of electro-hydraulic control facilities for the working units of the corresponding construction machinery.The subject of this paper is to deal with the automatic control technique used for the levelling systems on bulldozers, graders, milling machines, asphalt pavers and concrete finishers. Starting out from theoretical considerations, the experience gained from practical operation of the levelling systems employed nowadays will be described, as well as the limits set to these systems.

Modelling Asphalt Overlay As-Built Roughness Based on Profile Transformation—Case for Paver Using Automatic Levelling System

“…The asphalt paver working principle can be used to explain the previously described relationship between the wavelength content of the existing profile and the smoothness achieved during construction. When placing the asphalt mix, the levelling response of the paver screed is related to profile defects nature in a such a way that the longer the undulation on the surface being paved, more accurately the screed will replicate these undulations, i.e., the screed decreases its levelling efficiency as the wavelength of the defects causing the irregularity increases [12,13]. For this reason, pavers have incorporated the use of leveling beams (long reference averaging) and automatic control systems to regulate the screed tow-point position during paving and in this way compensate for the lowest leveling efficiency at longer wavelength defects.…”

“…Then, for positive spool displacement (x v > 0), the two flow equations representing flow out of the valve (Q 1 ) and flow back thought the valve (Q 2 ) are given by the well-known orifice equation. As shown in Equation (13) and Equation ( 14) respectively [25].…”