Abstract:
The transmission efficiency of hydraulic-mechanical continuously variable transmission varies significantly with changes in input and output conditions, which is a crucial factor impacting the operational economy of HMT tractors. Based on HMT efficiency, this study explores the influence of the formulation of objective function on tractor economy, this paper considers the efficiency of HMT and explore the influence of the influence of setting objective function on tractor economy.The integral efficiency optimal control strategy with the highest engine efficiency as the objective function and the integral efficiency optimal control strategy with the highest overall efficiency of engine and HMT as the objective function are proposed. The engine efficiency model and HMT efficiency model are established, The improved fish swarm algorithm is used to search and solve the control parameters, and the optimal control parameters under the two control strategies are obtained (engine speed and HMT speed ratio); The HMT tractor simulation model is established, according to the road/operation test data of real vehicles, the data fragments of common road/operation conditions were extracted, and the cycle conditions with speed and operation resistance as parameters were constructed, and the two control strategies were compared and simulated. The simulation results show that the fuel consumption of IOCS is 1.356L and that of EOCS is 1.381L in one simulation cycle, and the fuel consumption of IOCS is 1.81% lower than that of EOCS. Comparative analysis of simulation results shows that IOCS can effectively improve the overall efficiency of engine and HMT, and the economy is better than EOCS. However, in the face of load change, the engine and HMT operating point change more violently than EOCS, and the acceleration performance is worse than IOCS. In the face of load changes, the EOCS engine operating point changes more smoothly than IOCS, and the "reserve torque" is larger than EOCS. However, the instantaneous fuel consumption rate of HMT tractor of EOCS is slightly higher than that of IOCS, and the economy is slightly worse than that of IOCS. The research results can lay a research foundation for HMT tractors to formulate control strategies that meet the requirements of engineering applications.