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, Dynamic Analysis, and Experimental Evaluation of a Hybrid Parallel–Serial Polishing Machine With Decoupled Motions


In this paper, a novel six degrees-of-freedom (DOF) hybrid kinematic machine (HKM) is designed, analyzed, and evaluated for precision polishing. The design adopts a 3-DOF tripod-based parallel mechanism (PM) to locate the workpiece, a 2-DOF serial mechanism (SM) to orient the polishing tool, and a functional extension limb to provide a redundant DOF when polishing the workpieces with axially symmetrical shapes. Compared with the existing HKMs, the most distinctive feature is that the position and orientation adjustments of the tool with respect to the workpiece are decoupled during the synchronous machining, thus allowing the rotational tool center point (RTCP) function to be conveniently realized. For the developed HKM, the kinematics are studied systematically, including position, velocity, acceleration, and workspace. The dynamic model of the PM is derived by employing the principle of virtual work. For a pre-defined trajectory, the required driving forces are obtained through dynamic simulation. Based on these analyses, a laboratory prototype of the HKM is designed and developed. A preliminary accuracy assessment of the HKM is implemented with a double ball-bar, and a series of polishing experiments are conducted to show the capacity and feasibility of the developed HKM.
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