Simulation research on energy management strategy of six-row hybrid cotton picker

Cotton is an important economic crop and strategic resource. The 14th Five-Year Plan emphasizes the need to vigorously promote agricultural mechanization and intelligentization. As a key agricultural equipment for achieving whole process mechanization of cotton harvesting, cotton pickers have attracted increasing attention. In China, the traditional walking transmission system of cotton pickers usually adopts the form of hydraulic infinite variable speed combined with mechanical stepped transmission. However, during operation, these pickers face significant variations in working conditions and fluctuating external loads, resulting in an overall high load. The hydraulic walking transmission system finds it struggles to continuously adjust speed and torque to match the constantly changing actual load, which leads to frequent fluctuations in the engine operating points, mismatch of torque in transmission components, and low efficiency of the transmission system. At the same time, due to the large overall load during the operation of the cotton picker, the engine runs for a long time in the high-speed and high-load area, and it is unable to maintain the high-efficiency area, resulting in the problem of high fuel consumption. To address the high fuel consumption associated with traditional cotton picker engines operating in inefficient areas, as well as the low efficiency of the hydraulic drive transmission system, replacing the original 410 kW engine with a 560KW engine allows it to operate in the high-efficiency area. Simultaneously, employing hybrid technology to replace hydraulic transmission with electric drive can significantly improve the performance and efficiency of the cotton picker, yielding better operational outcomes and economic benefits. In order to solve the problems of low system efficiency and high energy consumption caused by the hydraulic transmission of the main working subsystem of the traditional diesel engine power six-row cotton picker, a series hybrid power system configuration is proposed for the first time. Based on this, a hybrid power system configuration for a six-row cotton picker is proposed for the first time. To accommodate the actual working conditions of cotton pickers, a two-speed gearbox is implemented, which includes a working gear and a transporting gear. The front and rear axles are driven by front and rear drive motors through gearboxes and front and rear axle reducers. This configuration allows for efficient operation and transmission of power, enhancing the overall performance of the cotton picker. A vehicle simulation model for a six-row series hybrid cotton picker has been developed using MATLAB/Simulink, and the effects of three strategies on the performance of the cotton picker are studied: power following strategy, equivalent consumption minimization strategy (ECMS), and torque distribution combined with equivalent consumption minimization strategy (TD-ECMS). Simulation results show that under a combined road transportation and field operation condition, the total simulation duration is 1,319 seconds, with 0 to 688 seconds allocated for road transportation and 689 to 1,319 seconds for field operation. The ECMS strategy significantly minimizes fluctuations in the engine's speed point. In comparison to the power-following strategy, which allows the engine to operate in a stable state only 34.34% of the time, the ECMS strategy enhances stability, increasing the stable operating time to 75.28%. This results engine speed stabilization time increased by 40.94 %. The TD-ECMS strategy achieves optimal control of the comprehensive efficiency of the dual motors, maintaining consistency with power-sharing control when the required power is high, and when the required power is low, the torque is completed by the front drive motor alone, the reduction of working points in the low-efficiency area of the rear-mounted motor leads to a decrease in the overall proportion of operation within the low-efficiency area. The comprehensive efficiency of the dual motors under the TD-ECMS strategy increased from 93.92% to 94.83% compared to power-sharing control. Compared to the power-following strategy, the ECMS strategy has reduced fuel consumption by 4.87%, and the TD-ECMS has reduced fuel consumption by 5.62%, resulting in a significant decrease and an improvement in overall economic performance. This paper presents an efficient energy management strategy for a six-row series hybrid cotton picker, laying the foundation for engineering practice.