Development of a Hydraulic Front Wheel Drive for a Battery Electric Truck

Sammanfattning: This master thesis work has been executed at Volvo GTT in Gothenburg. Focus has beenlaid on implementing a hydraulic front wheel drive (HFWD) system on a battery electricvehicle (BEV). The earlier concept builds have been performed on internal combustionengine (ICE) driven trucks at Volvo Trucks. The main difference in implementing thesystem on a BEV lies in the change of power take-off (PTO) which on a BEV is totallyindependent of the driving engine and cannot use the idle for rotating the charge pumpduring the inactive mode of the HFWD system. On the other hand, this opens up increasedcontrollability with many possibilities for improving the efficiency of the system.  Using efficiency maps of selected components, simulations have been performed tofind out the final energy consumption. Those are partly for the engaged mode where theHFWD is active and partly for when it is inactive. Different control strategies are comparedfor the active mode, including variating the electric motor, hydraulic pump, or both. Forthe inactive mode, one concept using a separate electric motor for a separate charge pumpand one concept removing the charge pump and running the main pump in cycles arecompared with the reference concept. The work resulted in a component- and CAD specification for a reference concept readyto be built within the near future, together with two concepts that can improve the energyefficiency of the HFWD system when operating in the disengaged mode. Results are alsoachieved for the active mode. Simulations show that controlling the pressure and flowby both the electric motor and the hydraulic pump is theoretically the most efficient, butmight bring difficulties in practice. The simulation analysis of the inactive mode showsthat fitting a separate DC motor for the charge pump will lower the disengaged energyconsumption by around 50%. Simultaneously, investigations show that removing thecharge pump completely might be an interesting way of designing the system, dependingon what temperature conditions the application will be used it may decrease the energyconsumption.  Our recommendation is to first build the reference concept according to the specificationpresented in the report on an actual truck to be able to validate the simulations. Thereafter the practical results can be evaluated and solutions from the alternative concepts beinserted with improved efficiency as a preliminary outcome.