Compact, backdrivable, and efficient design of linear electro-hydrostatic actuator module

An electro-hydrostatic actuator (EHA) has high backdrivability and is suitable for robots that interact with the environment, including human. However, the challenging problem in its mechanical design is that it is difficult to achieve compact size and high power transmission efficiency, compared with standard gear reducers. To tackle this problem, this study presents the design method by macro- and micro-scale designs. A linear-type EHA consists of a cylinder and a hydraulic pump. The former includes cylinder parameters that are dominant in the total size, and the latter includes gap width in the gear pump that is important for reducing power loss. We propose the hierarchical design to determine these parameters. In the macro-scale design, we determine the cylinder radius and differential pressure to maximize the efficiency-to-volume ratio. Based on the result of the macro-scale design, the micro-scale design determines the width of internal gaps to minimize the power loss in the gear pump. We derive mathematical formulations for the designs and develop the EHA by utilizing modular design and 3D printing. Moreover, we evaluate the fundamental properties of the developed EHA module, focusing on its power transmission efficiency and backdrivability.</p

Kaplan-Meier event curves for clinical outcomes in patients with two-vessel or three-vessel disease including proximal LAD.

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List of clinical research coordinators.

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Baseline characteristics, medications, angiographic and procedural characteristics during the index hospitalization in the propensity score-matched cohort.

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Kaplan-Meier event curves for clinical outcomes in patients with two-vessel disease including LAD.

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Fig 2 -

Crude kaplan-meier curves for the cumulative incidence of (A) all-cause death/MI/stroke, (B) all-cause death, (C) any coronary revascularization, and (D) all-cause death/MI/stroke/any coronary revascularization. PCI = percutaneous coronary intervention; CABG = coronary artery bypass grafting; MI = myocardial infarction.</p

Angiographic and procedural characteristics: PCI group versus CABG group.

Angiographic and procedural characteristics: PCI group versus CABG group.</p

Subgroup analyses for the primary outcome measure (death/MI/stroke).

Subgroup analyses for the primary outcome measure (death/MI/stroke).</p

Landmark analysis at 1 year and at 2 years for any coronary revascularization.

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Baseline characteristics and medications during the index hospitalization: PCI group versus CABG group.

Baseline characteristics and medications during the index hospitalization: PCI group versus CABG group.</p