Simultaneous Energy Management and Speed Control in a Hybrid Tractor With Experimental Validation

In recent years, the hybridization process is an emerging trend in heavy-duty vehicles and agricultural machinery. In this work, a parallel hybrid tractor is studied, aiming at developing an energy management strategy (EMS) able to deal with the built-in speed tracking requirements. Indeed, a speed controller is originally present in the tractor, so that the driver directly sends a speed command through the pedal. We propose an EMS based on the equivalent consumption minimization strategy (ECMS), which is properly modified to explicitly include the speed tracking objective. Then, the stability of the closed-loop system needs to be proven and discussed. Finally, the designed EMS is implemented on the tractor control unit and validated through a large experimental campaign on a small track. First, the benefits induced by the explicit consideration of the speed tracking are highlighted, and then the fuel-saving performance is assessed in different conditions, experiencing 14% of fuel saved on average, consistent with the simulation results.