Performance of an electronic control system for hydraulically driven forestry tandem trailers

• Evaluation of an electronic control system for hydraulic transmission on a trailer.
• System was tested on the forestry tandem trailers using test routes.
• System had good performance going up and downhill.
• System improved the versatility of the forestry tandem trailers.
• Control system could increase the general safety level of forestry trailers.

Timber transportation can be a complex operation because variations in timber types and soil characteristics can require changes to the vehicles and techniques used. Furthermore, this operation can be dangerous in unfavourable soil conditions (e.g. frozen and muddy ground). A solution to the problem is the use of mechanically or hydraulically driven trailers. The object of this study was to determine whether an innovative electronic control system for trailers equipped with motor axles, could be adapted to the hydraulic transmissions usually mounted on the forestry tandem trailers. The control system consisted of software that is able to modulate the forward speed of the trailer to that of the tractor as a function of the force presented on the hooked components. The control system mounted on forestry tandem trailers was found to have good performance and the versatility of the forestry tandem trailer was improved. Trailers equipped with hydraulic drive and the control system performed similarly to trailers fitted with mechanical drives normally used in forestry. However, unlike the latter, they had a higher ground clearance and were lighter because the absence of motor axle. It was considered that the control system increased safety levels because the tractor was protected from potentially dangerous oscillations generated by the trailer whilst driving on poor roads.