An integration of an electric motor and a drive with wide-bandgap (WBG) devices possesses numerous attractive features for electrified and decentralized actuation systems. The WBG devices can operate at a high-junction temperature (>170°C) with improved efficiency due to fast switching speed and low on-state resistance. It also leads to better performance and higher power density electro-hydrostatic actuators (EHAs) than the traditional solutions, which are being widely adopted in industrial applications such as aerospace, robotics, automobiles, manufacturing, wind turbine, and off-road vehicles. This paper introduces and investigates the benefits of the integrated motor drive with the WBG-based power electronics for the EHA systems.

The energy efficiency of an electro-hydraulic forklift is significantly improved by using a permanent-magnetsynchronous-motor-servo-drive-based direct pump control to control the position of the fork without control valves. This paper provides a short evaluation of the hydraulic system and a more detailed analysis of the losses of the electric machine drive system. A theoretical approach is taken and the results are verified by practical measurements. Finally, possible improvements of the energy efficiency in the suggested system are discussed.

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This paper presents a novel hydraulic setup, direct driven hydraulics (DDH), which consists of two pumps on a common axis driven by a servomotor. These pumps are directly connected to each chamber of a differential hydraulic cylinder. The pumps are dimensioned so that the respective nominal sizes corresponds to the expected flows of each cylinder chamber. However, the dimensioning of the pumps are slightly off, leading to an excess rise of pressure in the B-chamber. This paper investigates if the implementation of a hydraulic accumulator can mitigate this mismatch problem. A Matlab/Simulink model was created and utilized for simulating the optimal accumulator parameters for energy efficiency. The optimal alternative was implemented to the research setup and energy efficiency measurements are performed with various loads and different ambient temperatures. The results shows that this solution was a viable alternative and that the energy efficiency of this setup was improved.

This paper investigates energy efficiency and dynamic behavior through simulation and experiments of a compact electro-hydrostatic actuator system (EHA) consisting of an electric motor, external gear pump/motors, hydraulic accumulator, and differential cylinder. Tests were performed in a stand-alone crane in order to validate the mathematical model. The influence and importance of a good balance between pump/motors displacement and cylinder areas ratios is discussed. The overall efficiency for the performed motion is also compared considering the capability or not of energy recovery. The results obtained demonstrate the significant gain of efficiency when working in the optimal condition and it is compared to the conventional hydraulic system using proportional valves. The proposed system presents the advantages and disadvantages when utilizing components off-the-shelf taking into account the applicability in mobile and industrial stationary machines.