Although more efficient than e.g., constant flow systems, hydraulic load sensing (LS) systems still have various losses, e.g., system inherent pressure losses (SIPL) due to throttling at pressure compensators. SIPL always occur whenever two or more actuators are in operation simultaneously at different pressure levels. This paper introduces a novel hydraulic LS system architecture with reduced SIPL. In the new circuit, each actuator section is automatically connected either to the tank or to a hydraulic accumulator in dependence of its individual and the systems load situation via an additional valve. When connected to the accumulator, the additional pressure potential in the return line increases the load on the actuator and thus reduces the pressure difference to be throttled at the pressure compensator. The new circuit was developed and analyzed in simulation. For this, the hydraulic simulation model of a hydraulic excavator was used. To validate the sub-models of both machine and new circuit, two separate test rigs were developed and used. Both valid sub-models then were combined to the model of the optimized system. The final simulation results showed, that under the applied conditions, the novel hydraulic circuit was able to decrease SIPL of the examined system by approximately 44% and thus increasing the machines’ total energy efficiency. With the successful completion of the project, the gathered knowledge will be used to further develop the proposed circuit and its components.

Independent metering systems (IMSs) have been applied and researched in mobile machinery due to their advantages of reduced throttling energy losses and remarkable advances under negative load through decoupling actuator throttling control. Although IMSs have the control flexibility to deal with negative workloads, the control performance of the IMSs is challenged by uncertain loads in mobile operations, limiting the control accuracy. In addition, if the motion reference is improperly specified and exceeds the constraints, the pressure of the actuator may oscillate significantly and potentially result in control instability. In this study, a constrained adaptive robust control strategy is proposed for an IMS. An adaptive robust control strategy is designed for the meter-in and meter-out throttling to achieve precision motion control despite the nonlinearities and uncertainties of the electro-hydraulic IMS. The value of the uncertain workload is estimated in real-time and utilized in the model-based controller to improve control accuracy. In addition, a constrained trajectory planning approach is presented to handle out-of-constraint references and ensure motion tracking performance. This effectively prevents pressure fluctuations caused by the inappropriate reference.