Accurate flow measurement is critical for hydraulic systems because it represents a crucial parameter in the control of fluid power systems and enables the calculation of hydraulic power when combined with pressure data, which is valuable for applications such as predictive maintenance. Existing flow sensors in fluid power systems typically operate invasively, disturbing the flow and providing inaccurate results, especially under transient conditions. A conventional method involves calculating the flow rate using the pressure difference along a pipe via the Hagen–Poiseuille law, which is limited to steady, laminar, incompressible flow. This paper presents a novel soft sensor with an analytical model for transient pipe flow based on two pressure signals, thus eliminating the need for an actual volumetric flow sensor. The soft sensor was derived in previous research and validated with a distributed parameter simulation. This work uses a constructed test rig to validate the soft sensor with real-world experiments. The results highlight the potential of the soft sensor to accurately and computationally efficiently measure transient pipe volumetric flow based on two pressure signals.

In recent years, the electrification of mobile machinery has progressed. Due to the change of the primary energy source, the hydraulic system must be more efficient and sustainable. In this context, the use of decentralized electro-hydrostatic actuators (EHA) is highly promising. Still, a widespread use cannot be observed. Reasons for this might be the higher initial component costs, worse dampening, as well as higher expenditure in the implementation of the required controls. This paper presents a simulative evaluation of an electro-hydrostatic actuator with a hydraulic high-speed unit for use in mobile machinery. The circuit layout was selected based on cost considerations and includes load-holding capabilities. Furthermore, the load-holding valves are a key aspect of the control scheme. They are used to introduce a small active throttling at the discharge side of the cylinder in both pumping quadrants, thereby extending their load pressure range and enabling full operational coverage of the four-quadrants. The developed controller is mainly based on two state machines. It aims to synchronize the switching times of the valves with motor speed to enhance system performance and prevent system excitation. The controller is implemented in Matlab Simulink. For the aspired evaluation, it was coupled with a lumped parameter model of the circuit. The simulated cylinder velocities for several different speed and load combinations are evaluated to determine the control performance. Special focus is placed on the quadrant changes.

Accurate flow measurement is critical for hydraulic systems because it represents a crucial parameter in the control of fluid power systems and enables calculating hydraulic power when combined with pressure data, which is valuable for applications such as predictive maintenance. Existing flow sensors in fluid power systems typically operate invasively, disturbing the flow and providing inaccurate results, especially under transient conditions. A conventional method involves calculating the flow rate using the pressure difference along a pipe via the Hagen-Poiseuille law, which is limited to steady, laminar, incompressible flow. This paper presents a novel soft sensor with an analytical model for transient pipe flow based on two pressure signals, thus eliminating the need for an actual volumetric flow sensor. The soft sensor was derived in previous research and validated with a distributed parameter simulation. This work uses a constructed test rig to validate the soft sensor with real-world experiments. The results highlight the potential of the soft sensor to accurately and computationally efficiently measure transient pipe volumetric flow based on two pressure signals.

In recent years, the electrification of mobile machinery has advanced. One crucial issue is that the energy density of the associated storage solutions is lower, requiring more space on the machines or more frequent recharging. To compensate for this the hydraulic system must be more efficient and sustainable. In this context, the use of decentralized electro-hydrostatic actuators (EHA) shows high potential. However, they are not yet widely used. The reasons for this are likely higher initial component costs, worse dampening, and the high cost of implementing necessary control software. This paper presents a simulation-based evaluation of an electro-hydrostatic actuator with a hydraulic high-speed unit intended for use in mobile machinery. The circuit layout was selected based on cost considerations and incorporates load-holding capability. Furthermore, the load-holding valves are a key aspect of the control scheme. They are used to introduce a small amount of active throttling on the outflow side of the cylinder while energy is supplied to it. This extends the load pressure range in which the hydraulic unit is pumping and enables full operational coverage of all working conditions, which would otherwise be impossible. The developed controller synchronizes the valves’ switching times with motor speed to enhance system performance and prevent excitation. The controller is linked with a lumped parameter model of the hydraulic circuit and validated based on test cases that focus specifically on the quadrant switches, as well as on a measured dig and dump cycle. The results qualitatively demonstrate the excellent performance of the EHA, with mostly brief and minor velocity deviations during quadrant switching. The combination of the developed EHA and corresponding controller achieves good position tracking during the load cycle once drift due to inherent control delays is compensated for by a simple P-controller, representing the machine operator adjusting to the system response. This reduces the maximum RMSE of position deviation from 163 mm to 42 mm. In conclusion, the results demonstrate the functionality of the developed EHA and encourage further investigation, particularly experimental validation, to confirm the findings.