An Optimal Braking Force Distribution in the Rigid Drawbar Trailers with Tandem Suspension

Rigid drawbar agricultural trailers with laden weight of up to 13 tonnes have a single axle, up to 19 tonnes tandem axles. Carried out analysis of a tractor semi-mounted trailer combination showed that under ideal braking, the adhesion utilised by all axles and a coupling device are equal. By adopting the concept of treating the coupling device as a conventional front axle, the requirements of EU Directive 2015/68 for multi-axle trailers have been used to develop a new method for selecting the brake force distribution of semi-trailers with different suspensions. First, the forces acting on a single and tandem semi-trailer were analysed during braking. An algorithm based on the quasi-Monte Carlo method was then proposed to solve the constrained optimisation of the linear brake force distribution of semi-trailers equipped with ALB or MLB regulators. Finally, examples of MATLAB calculations were given for a 5 tonne single axle trailer and a 16-tonne trailer with 5 different tandem suspensions: bogie, two leaf spring, two leaf spring and rods, two leaf spring with dynamic equalisation and air spring. The results of the work are expected to provide a reference for the design and evaluation of the braking system of agricultural semi-trailers, especially with different types of tandem axles, to improve braking performance and reduce coupling forces.