Experimentell utvärdering av väggreppsmätaren RT3 Curve

Abstract

This thesis presents an experimental evaluation of the road grip estimator RT3 Curve manufactured by Halliday Technologies Inc. RT3 Curve can be pictured as a small trailer that is coupled behind a car. It measures the friction between two surfaces by two measuring wheels mounted with fixed slip angles. The vehicle dynamic term slip angle is the angle between a rolling wheel's actual direction of travel and the direction at which it is pointing. The slip angle causes side forces when the trailer is pulled behind the car. Mounted in the wheel center axis is a load cell mounted that measures the changes in the side forces that arise due to friction between the tire and the road surface. RT3 Curve is among other things intended to be used for measurement of winter maintenance processes. RT3 Curve is capable of measuring road grip at all kinds of road conditions as well as on straight, curved or cambered roads. It has, however, a limitation when it comes to curves where the minimum radius as specified by the manufacturer is 50 m.In this experimental study the relationship between road grip and curve radius has been investigated. The main question was how the road grip changes when turning compared with driving on a straight road. It has been found that the road grip differs from the reference value at a radius of about 20 m. The reference value is determined from runs on a straight section adjacent to the curve/roundabout where the measurement was made. An empirical function is formulated from the experimental data. This relationship allows us to compensate for the deviations in road grip that occurs when cornering. The model is validated only for surfaces with high friction such as asphalt. Road grip is very difficult to measure and it depends on both the tire and the road characteristics. The resulting model has to be developed and more extensive measurements has to be carried out on different surfaces such as dry asphalt, wet asphalt, snow, ice, etc.Validerat; 20150609 (global_studentproject_submitter