Automatic gear-shifting strategy for fuel saving by tractors based on real-time identification of draught force characteristics

Abstract

Adopting an automatic gear-shifting strategy for agricultural tractors can be an important factor affecting fuel consumption, and a reasonable gear-shifting strategy can effectively improve fuel economy. However, as an important part of the resistance exerted on the tractor–implement combination during tillage, the draught force of the implement strongly influences the driving state of the tractor. The changing characteristics of draught force with work speed largely determine the optimal timing of gear shifting. To realise automatic gear shifting to ensure fuel economy, it is necessary to obtain the varying characteristics of draught force in real time. However, draught force fluctuates is affected by many on-site factors, such as the physical properties of soil, operating speed and the design of the implements. A method is proposed using a recursive least-squares algorithm for the real-time identification of the changing characteristics of draught force. By analysing the forces exerted on the tractor–implement combination and the characteristics of the tractor powertrain, a mathematical model of the tractor–implement combination during field work was established. On this basis, four-parameter gear-shifting schedules were developed for tractor with different types of agricultural implements. The operating conditions were designed based on tractor operating characteristics. The validity and accuracy of the real-time identification method for the changing characteristic of draught force was verified. The designed gear-shifting schedules were proven to realise the automatic gear-shifting function according to the real-time working conditions on the premise of ensuring fuel economy and power performance.