Latest Papers

ASME Journal of Mechanisms and Robotics

  • Mechanical Characterization of Supernumerary Robotic Tails for Human Balance Augmentation
    on August 31, 2023 at 12:00 am

    AbstractHumans are intrinsically unstable in quiet stance from a rigid body system viewpoint; however, they maintain balance, thanks to neuro-muscular sensory control properties. With increasing levels of balance related incidents in industrial and ageing populations globally each year, the development of assistive mechanisms to augment human balance is paramount. This work investigates the mechanical characteristics of kinematically dissimilar one and two degrees-of-freedom (DoF) supernumerary robotic tails for balance augmentation. Through dynamic simulations and manipulability assessments, the importance of variable coupling inertia in creating a sufficient reaction torque is highlighted. It is shown that two-DoF tails with solely revolute joints are best suited to address the balance augmentation issue. Within the two-DoF options, the characteristics of open versus closed loop tails are investigated, with the ultimate design selection requiring trade-offs between environmental workspace, biomechanical factors, and manufacturing ease to be made.

Origami-Inspired Variable Stiffness Actuator for Safe Human–Robot Interaction


In this paper, an origami-inspired variable stiffness actuator (OVSA) is proposed. Innovatively borrowing from the origami principle, OVSA uses torsion springs and hinges to form a transformable hexagonal structure as the special elastic component. While having a light and compact structure, it can also theoretically realize the change of stiffness from zero to infinity. Archimedean Spiral Cam (ASC) is used as a transmission element to connect the motor and elastic components further increasing the compactness of the structure. In addition, the OVSA requires very little torque to maintain stiffness under deflection conditions, which improves energy efficiency. In this paper, the stiffness equation of OVSA is established and verified by experiments. The results show that its stiffness is high when the deflection angle is close to 0 deg and decreases rapidly with the increase of deflection angle, which makes it have sufficient safety.

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