Optimizing the mode switching quality of hybrid tractors equipped with mechanical-hydraulic compound transmission devices

Abstract During the mode switching process of a hybrid tractor equipped with a mechanical-hydraulic compound transmission (HMCVT) device, the separation and combination of the clutch will cause transient shocks, affecting the smoothness and driving comfort of the entire vehicle. This article establishes a system dynamics model in SimulationX simulation software and builds a hardware-in-the-loop (HIL) test platform for testing to study the simulation and testing when switching from pure electric drive mode to hybrid speed coupling mode. In order to solve the problem of slow dynamic response of the engine, this study proposes a control strategy of "clutch oil pressure fuzzy control + motor torque compensation” and uses the orthogonal test range analysis method and variance analysis method to optimize the vehicle mode switching quality. Taking the switching timing of the six clutches C0, C2, C3, C4, C6 and C7 involved in this article as the factors A, B, C, D, E and F of the orthogonal test range analysis, the clutch switches 0.5s ahead of time. On-time switching and delayed switching of 0.5s are used as three levels. L27(36) orthogonal table is selected for simulation test. Range method analysis shows that scheme A3B1C3D3E1F2 is the optimal switching scheme, that is, clutches C2 and C6 switch 0.5s in advance, and clutch C7 is on time. Switching, clutches C0, C3 and C4 are switched with a delay of 0.5s, the output shaft speed drop is reduced from 21.875% to 1.63%, the dynamic load coefficient is reduced from 8.473 to 2.72, and the impact degree is reduced from 26.181m/s3 to 7.08m/ s3, the switching time is reduced from 1.345s to 0.35s. A hardware-in-the-loop test platform was built for testing. The hardware-in-the-loop (HIL) test results were consistent with the overall trend of the simulation results, verifying the effectiveness of the proposed control strategy and method.