Analysis and control of high efficient electro-hydraulic solutions for the actuation systems of off-road vehicles

The transition to cleaner technologies, such as electrified systems in off-road vehicles, is crucial for reducing greenhouse gas emissions and promoting sustainable practices. This shift toward electrification is driving advancements in dedicated electrified hydraulic actuation systems. Traditional centralized fluid power architectures remain popular for their cost-effectiveness, power density, and reliability. However, the increasing demand for lower emissions is raising interest in electro-hydraulic actuators. By adopting individualization strategies, the overall efficiency of hydraulic systems, generally under 30%, can be increased through reduced throttling losses and the ability to recover energy during assistive loads. This capability not only improves transmission efficiency but also leads to lower fuel consumption, making EHAs an appealing alternative for meeting stringent emission regulations. This study explores two types of EHA architectures: an open-circuit design that connects directly to the tank, and a closed-circuit design where the differential volume of the linear actuator is stored and supplied by an accumulator. The sizing procedure for the electro-hydraulic system is discussed in detail, aiming to maintain the functionality of the baseline hydraulic system while optimizing costs. Both EHA configurations utilize a commercial electro-hydraulic unit that combines a variable-speed electric motor with a fixed-displacement hydraulic pump. A complete speed range across all four quadrants is achieved without requiring the hydraulic pump to operate at low rotational speeds, ensuring high efficiency throughout the unit's operation. This setup not only provides a cost-effective solution but also operates quietly, making it an attractive option for modern applications. In developing an effective EHA, careful attention must be paid to the components that ensure optimal performance and efficiency. A systematic approach to sizing various system elements, including the electric motor and hydraulic unit, is essential. The selection of these components follows an established sizing methodology, with particular emphasis on valve and filter selection influenced by the accumulator sizing. Additionally, the design of a manifold to house the cartridge valves and filter is addressed, underscoring its significance within the overall system architecture. To validate the EHA design, it is critical to predict the system's behavior before engaging in costly experiments and demonstrations. An integrated simulation model is developed using the lumped parameter approach within the Simcenter Amesim environment. This model incorporates the electric system, hydraulic system, and the intended mechanism, facilitating a thorough efficiency analysis. In the final phase, the closed-circuit EHA system is integrated into a reference vehicle, specifically a Case New Holland TV380 skid steer loader. Implementing the new electro-hydraulic system requires minor modifications to the baseline hydraulic circuit, along with instrumentation of the power electronics to operate the EHU. The conducted experiments focus on the energy-saving potential of the EHA, which shows efficiency up to 70% supporting the potential for commercializing these hydraulic systems in mobile applications.