The combination of hydrostatics and mechanical gearboxes cannot only improve system efficiency but also the usability of mobile machines. A possible solution could be a synchronized gearbox with two gears. Compared to the pure hydrostatic drivetrain, mobile machines with such a combination can have a larger drive torque with the first gear and higher efficiency at high speed. However, the calibration effort of this traditional drivetrain system is enormous; moreover, with a flow-based control, the degrees of freedom to achieve optimum shift performance in all conditions are limited. By adopting the primary torque control concept, we propose a novel hydrostatic-mechanical drivetrain control algorithm so that the holistic shift performance is better whilst the calibration effort is dramatically reduced by systematically adjusting only one hyper-parameter. Experienced engineers and machine operators validated the advantages mentioned here by a series of field experiments. Besides synchronized gearboxes, the controller proposed in this paper is also generalized to other kinds of mechanical transmissions.

This article describes the Dana intelligent Twin Steering System designed for mobile vehicles with two steering axles (i.e. with four steering wheels). Current vehicles with four-wheel steering function are typically equipped with a hydraulic configuration where the two steering cylinders are connected in series. This type of connection highlights some limitations on available power, steering comfort and enabling advanced working functions. Dana evolved this type of hydraulic configuration introducing the possibility to disconnect the rear axle from the front one. In this way the rear axle, through the electronic control of its valve block, allows to improve the steering system performance and introduces advanced steering functions compared to the conventional steering systems.