With the recent electrification trend in the fluid power area, more research has been incentivized to propose cost-effective and energy-efficient solutions for hydraulic systems. Hence, electro-hydraulic actuator (EHA) architectures receive increasing attention. The paper proposes a novel open-circuit EHA architecture, with the goal to obtain a cost-effective solution for mobile applications while maximizing the overall system efficiency. The proposed EHA is capable of meeting or exceeding traditional off-road machine performance, therefore enabling further electrification of off-road machines. Four-quadrant functionality, covering the full speed range, is achieved by a combination of a variable electro-hydraulic drive and valves with different functions. Focusing on the steady-state performance, the functionality is validated by numerical as well as experimental methods. A simulation model based on the Amesim environment and a dedicated test setup was developed to verify the performance. The good match between simulation and experimental results confirms the potential of the formulation approach of the proposed EHA for applications with different duty cycles and power levels.

This paper proposes an electro-hydraulic actuator (EHA) system, and a novel-designed electro-hydraulic unit (EHU) consisting of a fixed-displacement hydraulic gear machine and a variable-speed electric machine. The novel EHU design integrates an electric machine and a hydraulic machine in a single housing, targeting optimal compactness, power density, and component reduction. The EHA system features an open circuit design, where hydraulic hoses connect the EHU with a tank, a valve manifold, and the hydraulic cylinder. In this way, the proposed EHA technology can be used to implement distributed hydraulic actuation in a vehicle without requiring changes to the hydraulic actuators or at the overall layout of the hydraulic components with respect to the original vehicle design. A dedicated test rig is developed to verify the performance of the proposed EHA system. The efficiency of the EHA is measured in a steady state and under a realistic duty cycle of a commercial compact loader. The efficiency of the EHA system based on the measurements on the test rig can reach 54% with up to 20 kN load and 6 kW power level. Furthermore, the EHU is implemented on the reference machine to drive the boom function. Preliminary results on the performance of the EHU show an efficiency of up to 68% under different loading conditions.

This study introduces an innovative design for the hydraulic implement system in electrified compact loader applications. The presented architecture is based on the pre-compensated load sensing system, incorporating electronified components with energy regeneration capabilities. The system employs an electronified open-center pump (eOC-P) and a load sensing pre-compensated valve sourced from Rexroth. The compensator for the boom function is redesigned to remain static, allowing a bidirectional path for regeneration during the boom lowering phase. The eOC-P offers pressure control, flow control, displacement control, and torque control modes, achieved by replacing the traditional mechanical load sensing feedback with sensor signals. Enhanced by a dedicated control strategy, the redesigned system adapts its operational modes to suit both single and multiple user conditions, aiming to achieve optimal energy performance. This system is designed to seamlessly integrate into the electric drive, reducing components and conserving space in the compact machine, also improving the energy performance. According to the simulation with baseline measurements on a 68kW rated power 5-ton compact loader, the proposed system can save up to 30% energy during a single boom cycle. Moreover, approximately 20% of the input energy can be recovered and stored in the battery, effectively extending the operating hours of the machine.

This study introduces an innovative design for the hydraulic implement system in electrified compact track loader applications. The presented architecture is based on a pre-compensated load sensing system, incorporating electronified components and removing one compensator for the boom function. The system employs an electronified open-center pump (eOC-P) and a load sensing pre-compensated valve sourced from Rexroth. The compensator for the boom function is re-designed to remain static, allowing a bidirectional path for regeneration during the boom lowering phase. The eOC-P offers pressure control, flow control, displacement control, and torque control modes, achieved by replacing the traditional mechanical load sensing feedback with sensor signals. A dedicated control strategy is proposed and verified for the compensator-less design to adapt its operational modes to suit both single and multiple user conditions. According to the simulation, the proposed system can achieve the same controllability compared to conventional LS system with energy regeneration capability. From the tests on the proving ground, the novel system performs the same functionality and reduces the power consumption of 37% compared to the baseline open-center system on a 68kW rated power 5-ton compact loader.