Application of auto power shift (APS) controller for minimizing fuel consumption and performance evaluation of an agricultural tractor

•Auto power shift (APS) controller applies to minimize fuel consumption.•APS controller ensures a constant tractor forward velocity.•Fuel consumption is highly affected by the engine modes of the tractor.•APS ECO mode ensures the engine’s ability to perform with high load fluctuations.•APS ECO mode was the most economical engine mode for asphalt driving and plowing. Minimizing the fuel consumption of an agricultural tractor is the primary concern of researchers worldwide. Thus, developing a suitable controller that can reduce the fuel consumption of agricultural tractor is necessary. In this study, an automatic power shift (APS) controller that can select different engine modes, such as conventional, APS power, and APS ECO, is introduced. The objectives of this study are to verify the APS controller for asphalt driving, analyze the power delivery and fuel consumption of the tractor using different engine modes, and suggest the most suitable, efficient, and economical engine mode for the plowing operation. During asphalt driving, APS ECO mode has the lowest engine power of approximately 31.79 kW. Its fuel consumption is nearly 6.02 L/h, which is lower than those in the conventional and APS power modes by almost 43.84 and 21.10 % per working hour, respectively. However, the axle powers in all engine modes have no significant differences owing to the same forward speed of the tractor. The results prove the reliability of the APS controller performance. During the plowing operation, the engine power and fuel consumption in the APS ECO mode are approximately 70.29 kW and 18.46 L/h, respectively, which are lower than those in the conventional and APS power modes. However, the power delivery efficiency in the APS ECO mode is lower than that in the conventional mode, and the slip ratio is the highest among all engine modes. In addition, the tractive efficiency in the conventional mode, which is approximately 63.56 %, is the highest among all engine modes. However, the effective field capacity in the APS ECO mode for plowing is approximately 1.52 ha/h, which is the highest among all engine modes. The comparative analysis also shows that the working load in the APS ECO mode is located in the ungoverned region of the engine characteristic map, which can avoid sudden engine turn-off during large fluctuations in the working load. Furthermore, the fuel consumption in the APS ECO mode for plowing is reduced by almost 23.37 and 15.59 % compared with those in the conventio