Drivaxeltrycksreglering hos tunga fordon : För en ökad framkomlighet vid vinterförhållanden

Sammanfattning: Heavy duty vehicles often have problems with traction during the winter periods. For vehicles that can lift tag axles it is possible to increase the normal force on the driven axle by lifting one or more tag axles, this will then increase the propulsive force of friction. This however increases wear on both road and vehicle. A possibility to reduce the wear while achieving nearly equivalent traction compared to lifted tag axles is to allow the vehicle to regulate the normal force by lowering the pressure in the air suspension associated with the tag axles or by the lifting of these axles. The vehicle would then by itself be able to set just the right amount of normal force on the drive wheels to avoid unnecessarily high normal forces while maintaining sufficient traction. The purpose of the report is to find out which parameters affect heavy duty vehicles when driving on slippery slopes and how traction can be improved. To shed some light on this, thorough information searches have been carried out, dynamic models and relations for heavy vehicles have been developed and a program for the simulation of heavy duty vehicles programmed in MATLAB. The results from the simulations show that there is a potential in automatic control of pressure on driven axles. To give good performance such a system would work well in combination with GPS and topographical data. In that way the vehicle can in advance regulate the pressure on driven axles to a level fitting the current incline. This system would also be a lot gentler on the road than if the driver lifts the tag axles. This is because the need for high axle pressure is most of the time at a low level.