*4.4. Full Electric Mode*

The proposed HeCVT architecture allows for operating in full electric mode. This mode is available through the disengagement of the clutch between thermal unit and the drive shaft to which the generator is coupled. Full electric mode can be used in light work situation, since at high loads, the instantaneous discharging current of the battery pack would exceed the safety limit of 5C or endurance may be too low. To explore full electric capabilities, some of the work scenarios shown in previous sections were considered. Table 9 shows the powertrain performance in full electric mode, while Table 10 reports the endurance at different vehicle speed levels. Endurance means the time to discharge the battery SOC from 100% to 20%. Figure 11 shows the results of the 0–40 km/h acceleration in full electric mode with no trailer. When the vehicle reached speed of 15 and 40 km/h, the two electric machines had approximately the same rotational speed corresponding to

their base speed. In addition, the power coming from the battery pack did not exceed either instantaneous or continuative previously imposed safety limits.

**Table 9.** HeCVT performance in full electric mode.


**Table 10.** HeCVT endurance in full electric mode: constant speed 40 km/h with different trailer payloads.


**Figure 11.** HeCVT 0–40 km/h acceleration test without trailer and 0% of slope in full electric mode.

#### **5. Conclusions**

In this work, a HeCVT tractor architecture was studied to investigate its performance in terms of peak power capabilities in field-derived work tasks and fuel saving in daily work cycles against a traditional orchard tractor taken as the case study. The HeCVT was equipped with a downsized diesel engine of 56 kW and two electric motors of 30 kW, whose capabilities were mechanically combined with a two-stage planetary gear. This layout allowed for both for ICE operating point optimization and to use the BP power reservoir as a booster thanks to the proper control of the two electric machines. The proposed HeCVT architecture showed promising results in almost all the test cases, achieving the best improvements in trailer handling where the conventional architecture is obliged to continuously change the engine rotational speed to follow the desired travel speed of the driver. Performance tests with several combinations of slopes and trailer payload were considered to see how the HeCVT powertrain was able transfer power to the wheels in different combinations of travel speed and resistive load. Results showed that the HeCVT was able to perform in the acceleration and overcoming of slopes as much as the conventional powertrain in almost all the performed tests. Therefore, the proposed hybrid architecture is a valid alternative to the traditional one since it achieved at least the same performance in terms of peak power capabilities, but is also able to accomplish typical daily work activities with a significant reduction in fuel consumption. Moreover, the compact longitudinal design of the transmission and the size of the proposed battery pack are suitable for the required compactness in orchard tractors. Future works will explore further optimization techniques for ICE operating points and in-depth design optimization of powertrain elements without compromising the good results achieved with this preliminary solution.

**Author Contributions:** Conceptualization, F.M. and V.M.; methodology, F.M. and V.M.; software, F.M. and V.M.; validation, F.M. and V.M.; formal analysis, F.M. and V.M.; investigation, F.M. and V.M.; resources, F.M.; data curation, F.M. and V.M.; writing—original draft preparation, F.M. and V.M.; writing—review and editing, F.M. and V.M.; visualization, F.M. and V.M.; supervision, F.M.; project administration, F.M.; funding acquisition, F.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported in part by the Italian MISE project Brevetti+—Ecothea (C65F20000290008).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The authors would like to thank Ecothea Srl for the possibility to explore the full capabilities of the patented eCVT architecture thanks to funds from Italian MISE project Brevetti+.

**Conflicts of Interest:** The authors declare no conflict of interest.

## **References**

