## 1 Introduction  
In recent years, the number of tractors of different forms has greatly increased, as they are the main type of agricultural power machinery. The inefficiency and high fuel consumption of traditional tractors lead to energy waste and environmental pollution [1]. A tractor uses 345,000 kL of oil, accounting for 48.5% of the total oil consumption of agricultural machines. Thus, developing an efficient tractor is necessary [2]. Battery-powered electric vehicles have been proven to be one of the most effective ways to reduce emissions and energy consumption. With the rapid development of battery technology and motor technology, there is growing interest in the electrification of agricultural tractors [3]. Pure electric tractors (PETs) seem to be a promising solution in the context of more sustainable farming as they can use a wide range of power sources which can be obtained from a variety of renewable or clean energy sources [4]. However, at the current technical level, the biggest bottleneck in the development of PET is their limited operation time. Optimizing transmission efficiency is a practical method to increase operation time before the energy density of the battery displays evident improvement. The improvement of transmission efficiency depends on the development of an efficient powertrain and effective control strategies. At present, the powertrains of PETs on the market are mostly driven by a single motor, whereby the diesel engine is replaced by batteries and a motor and the original multi-gear transmission is retained [5; 6; 7]. Considering the different power requirements of tractors under various working conditions, the motor often works in a low-efficiency region under low-load conditions. Moreover, research shows that the tractors' multi-speed mechanical gearboxes will bring more energy losses [8]. It has been found that in the powertrain configuration of \"single motor + multi-speed transmission\", it is difficult to change the current situation of tractors, whereby they present low efficiency and high power consumption. Therefore, it is necessary to find other powertrain structures that can improve tractor efficiency. Many studies have shown that dual-input coupling powertrain systems (DICPSs) have been widely used in electric vehicles to reduce energy consumption and improve efficiency [9; 10; 11; 12]. By using two smaller motors instead of a single high-power source, the torque capacity of a single motor can be reduced, which is beneficial to the development of high-speed motors, thereby increasing the power density of the driving system. Moreover, the operating points of the two motors can be adjusted to optimize the efficiency of the drive system. Most studies on DICPS in the agricultural tractor field have focused on hybrid tractors, while the PET concept is applied less frequently. [PERSON] et al. designed a powertrain simulation model and proved the fuel consumption reduction of the parallel hybrid tractor through the power distribution ratio strategy. The results showed that the fuel efficiency of the hybrid tractor was 11.78% higher than the conventional tractor [13]. [PERSON] et al. developed a parallel hybrid tractor, which had three control modes: idle, power assist, and battery charge. The results showed that the performance of the hybrid tractor was better than the conventional tractor at the higher load condition, and the fuel efficiency was 74% lower than that of the conventional tractor [2]. [PERSON] et al. designed a parallel hybrid tractor transmission system with a planetary gear set as the power coupling device, and a design theory and calculation method for the transmission system were proposed. The simulation results showed that the hybrid tractor could save energy by up to 24% under plowing operations compared to the equivalent power fuel tractor [14]. The literature studies described above show that hybrid tractors with a dual-input powertrain can effectively improve fuel efficiency.