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.

Dynamics of a Parallel-Kinematics Machine With Six Pairs of Offset Joints


The authors propose a systematic formulation of the dynamics of the 6-P-RR-R-RR parallel-kinematics machine (PKM) with offset RR -joints. The kinematics of the same system is reported in an accompanying paper. Based on the kinematics model developed in the former, the dynamics model of the limb-chain is derived here using the Newton–Euler equations. Then, the constraint wrenches in the governing equations of the limb-chain are eliminated with the aid of the natural orthogonal complement. This is the twist-shaping matrix, which maps the joint-rate array of the limb-chain into the twist array of the PKM. Furthermore, the dynamics model of the whole PKM with offset joints is formulated. Moreover, the actuator forces are obtained. Finally, upon validation via simulation, the dynamics model is proven to be both precise and effective.

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