Latest Papers

ASME Journal of Mechanisms and Robotics

  • Dynamics of Mobile Manipulators Using Dual Quaternion Algebra
    on September 14, 2022 at 12:00 am

    AbstractThis article presents two approaches to obtain the dynamical equations of mobile manipulators using dual quaternion algebra. The first one is based on a general recursive Newton–Euler formulation and uses twists and wrenches, which are propagated through high-level algebraic operations and works for any type of joints and arbitrary parameterizations. The second approach is based on Gauss’s Principle of Least Constraint (GPLC) and includes arbitrary equality constraints. In addition to showing the connections of GPLC with Gibbs–Appell and Kane’s equations, we use it to model a nonholonomic mobile manipulator. Our current formulations are more general than their counterparts in the state of the art, although GPLC is more computationally expensive, and simulation results show that they are as accurate as the classic recursive Newton–Euler algorithm.

A Novel Tunable Stiffness Mechanism Using Filament Jamming


The jamming mechanism is a crucial method to tune the stiffness of soft-bodied machines to adapt to their surroundings. However, it is difficult for the present jamming structures to integrate them into systems with complicated shapes such as twist, cylinder, and spiral. This paper introduces a novel jamming mechanism termed a filament jamming technique, which varies stiffness using jamming of a cluster of tiny and compliant filaments. The jamming structure demonstrated various characteristics such as softness, shape compatibility, lightweight, and high stiffness. These feats can meet a variety of application scenarios that the traditional jamming one cannot afford. The experimental test was used to explore the jamming structure’s stiffness behavior and dynamic performance. The influence of the filament structure dimensions, material properties, and the vacuum pressure on the stiffness was revealed. With the negative pressure increasing, both the natural frequency and damping ratio increase due to the rigidity variation. It indicates that the filament jamming structure has excellent response rapidity and shock resistance. Our work demonstrated some versatile features of the filament jamming technology, like shape adaptation, shape-preserving, stiffness stability, and compliance. To demonstrate the advantage of the jamming technique, we constructed a soft gripper and a torsional actuator to illustrate how the mechanics of filament jamming can enhance real-world robotics systems’ performance. Therefore, the filament jamming mechanism provides various machines and structures with additional properties to increase forces transmitted to the environment and tune response and damping. This study aims to foster a new generation of mechanically versatile machines and structures with softness and stiffness.

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