粘弾性測定方法とその加振機構に関する研究

学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 樋口 俊郎, 東京大学教授 佐々木 健, 東京工業大学教授 鈴森 康一, 東京大学准教授 山本 晃生, 東京大学准教授 森田 剛University of Tokyo(東京大学

Ergonomic dual four-bar linkage knee exoskeleton for stair ascent assistance

Introduction: Robotic exoskeletons are emerging technologies that have demonstrated their effectiveness in assisting with Activities of Daily Living. However, kinematic disparities between human and robotic joints can result in misalignment between humans and exoskeletons, leading to discomfort and potential user injuries.Methods: In this paper, we present an ergonomic knee exoskeleton based on a dual four-bar linkage mechanism powered by hydraulic artificial muscles for stair ascent assistance. The device comprises two asymmetric four-bar linkage mechanisms on the medial and lateral sides to accommodate the internal rotation of the knee and address the kinematic discrepancies between these sides. A genetic algorithm was employed to optimize the parameters of the four-bar linkage mechanism to minimize misalignment between human and exoskeleton knee joints. The proposed device was evaluated through two experiments. The first experiment measured the reduction in undesired load due to misalignment, while the second experiment evaluated the device’s effectiveness in assisting stair ascent in a healthy subject.Results: The experimental results indicate that the proposed device has a significantly reduced undesired load compared to the traditional revolute joint, decreasing from 14.15 N and 18.32 N to 1.88 N and 1.07 N on the medial and lateral sides, respectively. Moreover, a substantial reduction in muscle activities during stair ascent was observed, with a 55.94% reduction in surface electromyography signal.Discussion: The reduced undesired load of the proposed dual four-bar linkage mechanism highlights the importance of the adopted asymmetrical design for reduced misalignment and increased comfort. Moreover, the proposed device was effective at reducing the effort required during stair ascent

Mechanical Characterisation of Woven Pneumatic Active Textile

Active textiles have shown promising applications in soft robotics owing to their tunable stiffness and design flexibility. Given the breadth of the design space for planar and spatial arrangements of these woven structures, a rigorous and generalizable characterisation of these systems is not yet available. In order to characterize the response of a stereotypical woven pattern to actuation, we undertake a parametric study of plain weave active fabrics and characterise their mechanical properties in accordance with the relevant ISO standards for varying muscle densities and both monotonically increasing/decreasing pressures. Tensile and flexural tests were undertaken on five plain weave samples made of a nylon 6 (polyamide) warp and EM20 McKibben S-muscle weft, for input pressures ranging from 0.00 MPa to 0.60 MPa, at three muscle densities, namely 100 m−1 , 74.26 m−1 and 47.62 m−1 . Contrary to intuition, we find that a lower muscle density has a more prominent impact on the thickness, but a significantly lesser one on length, highlighting a critical dependency on the relative orientation among the loading, the passive textile and the muscle filaments. Hysteretic behaviour as large as 10% of the longitudinal contraction is observed on individual filaments and woven textiles, and its onset is identified in the shear between the rubber tube and the outer sleeve of the artificial muscle. Hysteresis is shown to be muscle density-dependent and responsible for a strongly asymmetrical response upon different pressure inputs. These findings provide new insights into the mechanical properties of active textiles with tunable stiffness, and may contribute to future developments in wearable technologies and biomedical devices

Video1_Self-excited valve using a flat ring tube: Application to robotics.MP4

Complex and bulky driving systems are among the main issues for soft robots driven by pneumatic actuators. Self-excited oscillation is a promising approach for dealing with this problem: oscillatory actuation is generated from non-oscillatory input. However, small varieties of self-excited pneumatic actuators currently limit their applications. We present a simple, self-excited pneumatic valve that uses a flat ring tube (FRT), a device originally developed as a self-excited pneumatic actuator. First, we explore the driving principle of the self-excited valve and investigate the effect of the flow rate and FRT length on its driving frequency. Then, a locomotive robot containing the valve is demonstrated. The prototype succeeded in walking at 5.2 mm/s when the oscillation frequency of the valve was 1.5 Hz, showing the applicability of the proposed valve to soft robotics.</p