Optimisation of the power-cycle hydro-mechanical parameters in a continuously variable transmission designed for agricultural tractors

Power transmission is a critical component of agricultural tractor designs and more demanding requirements have been placed on transmissions due to the complexities of their operational environments. However, economic performance is usually sacrificed in favour of using high-powered engines to satisfy the dynamic performance requirements related to power. In this study, a new power-cycle hydro-mechanical continuously variable transmission (PCHMCVT) device is proposed for use in agricultural tractors. The effects of various structural parameters on the system performance is analysed, and an evaluation index for the performance of the PCHMCVT performance is proposed. A comprehensive examination of speed regulation performance, economic performance, and dynamic performance are performed. A multi-objective optimisation design numerical model is established, which utilises the NSGA-II multi-objective genetic algorithm to optimise the transmission. Finally, the feasibility of the optimisation results is verified by comparing and analysing the speed ratios, torque ratios and efficiency characteristics of the trans- mission before and after optimisation. This study provides an optimised design method for the selection of the structural parameters of the PCHMCVT to ensure competent overall performance. (C) 2019 IAgrE. Published by Elsevier Ltd. All rights reserved.