Multi-parameter optimization of HMCVT fuel economy using parameter cyclic algorithm

Fuel economy has been the basic requirement of tractor operation in recent years. This study aims to improve the fuel economy of small and medium-sized tractors with hydro-mechanical continuously variable transmission (HMCVT) in modern agriculture. The continuous variable planetary ratio of a single planetary row was also combined to run at the working point with the best economy of the whole machine under any load conditions. The parameter of continuous variable planetary ratio was then considered to further improve the control strategy of HMCVT fuel economy. Firstly, the optimal fuel economy index of the tractor was analyzed during this time. The ratio of engine fuel consumption rate ge to HMCVT efficiency of transmission ηb was proposed as the economic objective function of the tractor. The effective fuel consumption rate of the BM58G diesel engine was combined to explore the influencing factors of transmission efficiency of planetary ratio continuously variable HMCVT. In addition to the three basic parameters of engine speed, torque and displacement ratio of the variable pump, the planetary ratio of the planetary row also showed a certain influence on the economy of the tractor. Then, the evaluation index of the tractor economy was determined to combine with the operation characteristics of small and medium-sized tractors. A multi-parameter stepless speed control was formulated with the engine speed, torque, displacement ratio of the variable pump of the HMCVT variable speed transmission system and the planetary ratio of traction planetary row as the control parameters. The control flow was then elaborated on in detail. At the same time, the small and medium-sized HMCVT tractor with the continuously variable planetary ratio was taken as the research object. The control parameters were calculated in the multi-parameter adjustment using Matlab software and the parameter cycle algorithm. The optimal combination was obtained, including the optimal engine speed, torque, and HMCVT variable pump displacement ratio and the planetary ratio of the traction planetary row under any load and target speed of the tractor. Consequently, the optimal control strategy was easy to control the multi-parameter economy of the tractor. The optimal value of any control parameter was obtained under different working conditions after one optimization. After comparison, the addition of the traction planetary row planetary ratio was reduced by 29.86% fuel consumption rate of the tractor, compared with the national standard. Then, the suitable operating speed was determined under different operating items of the tractor. A systematic analysis was also made on the influence of the planetary ratio of the traction planetary row on the economy of the tractor under the three operating speeds of low, medium, and high levels. The planetary ratio and the displacement ratio were then selected under the three operating speeds of low, medium, and high in the transmission system. Once the vehicle was required the lower fuel consumption, the planetary ratio should be taken as large as possible within a certain range. In addition to the pure mechanical condition with a displacement ratio of 0, there was no outstanding optimal value of the remaining displacement ratio for the fuel consumption under the corresponding operating speed. Finally, the control effect of multi-parameter adjustment was verified from two aspects of transmission efficiency and speed ratio of HMCVT. Therefore, the larger displacement ratio and planetary ratio within a certain range can be expected to ensure that the tractor worked in a wide speed ratio range of 0.07-0.38 and a high-efficiency range of transmission efficiency greater than 0.92. The finding can also provide the theoretical reference to promote the development and application of CVT tractor transmission, as well as the power and fuel economy of tractors.