Bosch says that adding an electrified axle to a trailer takes the industry one step closer to automated trailer parking. According to the company, adding a powertrain to the axle means that the trailer can be shunted around the parking lot without a tractor. Bosch says that the technology is available for new trailers or as a retrofit solution.
Electrified axles facilitate remote-controlled electric driving on private property such as freight companies’ premises or at ports because the electric motor makes the trailer into an independent vehicle that can travel short distances. With the help of additional sensors attached to the trailer and installed at various points in the depot, it will be possible for goods trailers to park themselves.
The parts needed to electrify an axle include an inverter and the relevant vehicle control unit (VCU) supplied by Bosch. A separate motor generator (SMG) is available for installation as a complete electric motor, or the active components—rotor, stator, and resolver—can be integrated into the axle. A battery system that can store the energy is also required.
As far as electrified axle cost, Bosch’s view is that the system must pay back the original investment after two years’ operation at the latest. In view of the cost savings the axle offers in applications such as refrigerated trailers, Bosch is confident that this goal is realistic. In its estimate of fuel savings in such applications, Bosch first considers that the diesel engine that currently powers the refrigeration unit, and that is now being completely displaced by electricity, consumes between two and three liters of diesel an hour. On this basis, annual consumption is roughly 9,000 liters. In addition, there are potential savings resulting from the electrical assistance provided when starting, accelerating, and on ascents. The extra savings may be as much as 4%.
The use of two electric motors is favored because it can recuperate significantly more energy, and offer a high additional benefit at relatively low extra cost, thus allowing greater savings to be made. In addition, a dual-motor axle is better for automatic maneuvering at a depot: Having an electric motor at each end of the axle significantly reduces the trailer’s turning radius. If the customer wishes to save costs, electrification with just one motor is possible.