Displacement control optimization of hydro-static transmission system containing variable displacement pump and hydro-motor of a front-end loader

Abstract

The article focuses on optimizing the Front-End-Loader (FEL) machine’s hydro-static transmission (HST) system, which comprises a variable displacement hydraulic pump and hydro-motor. These components enable 2-DOF controlled operation, adjusting both pump and hydro-motor displacements simultaneously. In off-road applications, fluctuating load and speed disrupt the FEL’s efficiency. To address this, the article introduces a novel Look-up table-based MIMO controller. This controller algorithm dynamically adjusts displacement of pump $D_{p}$ and displacement of hydro-motor $D_{m}$ based on speed or load demands, aiming for maximum overall efficiency. Integrated into the control hardware, the system optimizes performance within specific speed and torque ranges. Additionally, a sensitivity analysis highlighted the pump and hydro-motor’s higher responsiveness to displacement and operating pressure, emphasizing their crucial role in efficiency optimization. This approach ensures the FEL operates within its efficiency zone, particularly beneficial for off-road applications. Also, the solution may be directly implemented as a software update solution on the transmissions with an electronically controlled variable displacement pump and motor to operate it at high efficiency.

Keywords

2-DOF optimized control closed-circuit closed-loop HST system load cycle of front end loader Look-up table based MIMO controller

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