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.

Design and Implementation of a Novel Variable Stiffness Actuator With Cam-Based Relocation Mechanism


Variable stiffness actuators (VSAs) are widely explored as they could improve the safe performance for human-robot interaction and make the system torque controllable based on the internal compliance. This article presents a novel VSA based on the cam-based relocation mechanism (CRM-VSA), which is utilized to change the locations of pivot and spring of a lever mechanism simultaneously. Consequently, such structure makes the actuator compacted and the stiffness regulation designable, which could help engineers to pursue different demands of stiffness regulation. The simultaneous relocations of the pivot and spring also permit a wide range of adjustable stiffness. By introducing linear guide pairs, the internal friction of the relocations of pivot and spring could be greatly reduced, thus enhancing the energy efficiency. To evaluate the performance of the proposed CRM-VSA, the point-to-point control strategy is developed, which contributes to a higher tracking accuracy and oscillation attenuation at both the start and end points of the trajectory. In addition, the performance of torque controllability is also verified through experiments. These excellent capabilities enable the proposed CRM-VSA to be qualified for constructing a robotic arm toward service applications.
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