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.

Energy-Efficient Tristable Soft Gripper Using Shape Memory Alloy Wires for Gripping Convex and Concave Objects


Bistable structures have been widely utilized in soft grippers to reduce the energy required for maintaining grip. Grippers have been investigated in terms of the energy efficiency and accuracy of gripping; however, the limited number of gripping states hinders the holding of objects of various shapes. In this study, an energy-efficient gripper was developed to accommodate both convex and concave shapes using a tristable structure that combines two bistable structures, with shape memory alloy wires used as actuators. Different gripping modes were designed for convex and concave shapes, based on three states of the gripper: gripping, open, and holding. The gripper consisted of a driving part with a leaf spring for a “linear snap action” and a soft finger part with an elastic ring and prestressed fingers. Geometric variables were adjusted to construct a tristable energy curve through experiments and analyses. The fabricated gripper weighed about 140 g and was capable of gripping convex objects of up to 80 g, and concave objects of about 120 g. Only a small amount of energy was consumed in the switching states, and the gripper maintained a stable state while gripping with no energy consumption. It is expected that this research will contribute to lightweight and energy-efficient grippers for application to drones, for example.

Read More

Journal of Mechanisms and Robotics Open Issues