Design, Analysis, and Verification of an Electro- Hydrostatic Actuator for Distributed Actuation System

In order to provide a simplified and low-cost solution of the terminal for a distributed actuation system, this paper proposes an electro-hydrostatic actuator (EHA) based on the linear drive principle. The proposed actuator is directly driven by a linear pump with a collaborative rectification mechanism, whose performance relies on the collaboration of the internal two units. A pair of linear oscillating motors are employed to drive the two pump units respectively. The control of the actuator is based on the modulation of the oscillating amplitude, frequency, and phase difference of the two motors. The advantage of this actuator is that no more valve control is needed to rectify the linear pump besides the high efficiency of the direct pump drive. In this paper, both schematic and detailed structure of the actuator is presented. The kinematic and dynamic characteristics are analyzed and modeled, based on which the control method is proposed. The experiments verify the validity of the actuator structure and control.

A Case of Monochorionic-Triamniotic Triplet Pregnancy with TRAP Sequence Successfully Treated with Radiofrequency Ablation with a Parallel Circuit Consisting of Anastomosed Blood Vessels between the Direct Pump Fetus and the Indirect Pump Fetus

Monochorionic-triamniotic triplet pregnancy with twin reversed arterial perfusion (TRAP) sequence is one of the rare complications of multiple pregnancy and has been reported by only a few. Here, we report a case of monochorionic-triamniotic triplet pregnancy with TRAP sequence successfully treated with radiofrequency ablation, which did not develop polyhydramnios and heart failure although the estimated weight of the acardiac fetus increased twice as much as that of the direct pump fetus. Interestingly, the anastomosed blood vessels between the direct and indirect pump fetuses comprised a parallel circuit, which provided blood flow to the acardiac fetus. We hypothesized that the burden on the pump fetus in monochorionic pregnancy with TRAP sequence would be different between triplet and twin pregnancies.

High Precision Energy Saving Motion Control of Hydraulic Cylinder Based on Integration of Valves and Pump

The independent metering approach makes the two chamber pressure states of the hydraulic actuator completely controllable, which offers the opportunity for energy conservation by reducing the working pressure. However, there still remains a great deal of throttling losses since the entire flow rate is throttling controlled with the valves. In order to avoid throttling losses, the direct pump controlled system might be an option, but the relatively slow dynamic response restricts its application in occasions with response and precision demands. To realize further energy conservation and simultaneous high precision tracking performance, this paper proposes a brand new hardware configuration which integrates the direct pump control, independent metering, and energy reuse methods and takes advantages of their respective strengths. The adaptive robust control approach is applied to deal with the nonlinear control problems. Comparative simulations are done with the focuses on energy consumption and tracking performance.

Effect of Zonal Hydraulics on Energy Consumption and Boom Structure of a Micro-Excavator

This paper investigates the effect of extra weight caused by the Direct Driven Hydraulics (DDH) in a micro-excavator. These projects are investigating the implementation of zonal or decentralized hydraulics for non-road mobile machinery (NRMM) and stationary industrial applications. The benefit of DDH is the combination of electric and hydraulic technologies in a compact package compared to conventional hydraulics, which enables a reduction of potential leakage points, flexible tubing, and boosting of the system efficiency due to switching to direct pump control instead of a loss-generating conventional valve-based control. In order to demonstrate these benefits for the excavator case, this paper proposes a system model approach to assess and predict energy consumption of the zonal hydraulics approach implemented with DDH in various working cycles, complemented by a structural analysis. The finite element analysis utilized for this demonstrated that the extra weight and selected location of DDH units do not negatively affect the structure of the excavator. Simulation results demonstrated that the energy consumption is approximately 15% higher with extra weight added by the three DDH units. Although approximately 20% more regeneration energy is produced, taking into account the regeneration energy, the increases in energy consumption are about 12%.

Twin-Reversed Arterial Perfusion Sequence in a Triple Monochorionic Pregnancy with Two Direct Pump Fetuses Results in Significant Cyclic Doppler Waveform

We report a case of a twin-reversed arterial perfusion (TRAP) sequence complication in monochorionic triplets, in which both normal fetuses were directly connected to the umbilical cord of the acardiac fetus, thus both acting as a pump twin. Doppler ultrasound showed a significant waveform pattern with two superposed systolic waveforms in the same vessel. After birth, placental findings confirmed the existence of two direct pump twins. The Doppler pattern described here may be of help to distinguish the existence of two pump twins in a triplet monochorionic pregnancy with TRAP.