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.

Design and Experimental Verification of a Parallel Hip Exoskeleton System for Full-Gait-Cycle Rehabilitation


Rehabilitation with exoskeletons after hip joint replacement is a tendency to achieve efficient recovery of people to rebuild their human motor functions. However, the kinematic mismatch between the kinematic and biological hip is a problem in most existing exoskeletons that can cause additional stress in the hip. To avoid secondary damage, the misalignment between the mechanical and biological hip joint of an exoskeleton must be compensated. This paper introduces a novel hip exoskeleton system based on parallel structure. The exoskeleton can inherently address the kinematic mismatch by introducing additional kinematic redundancy, while requiring no additional kinematic components and volumes. To achieve bidirectional full-gait-cycle walking assistance, a remote actuation system is designed for power delivery, and a control scheme is proposed to reject disturbances caused by gait dynamics during walking exercises. Human testing was carried out to evaluate the performance of the system. The results show that the exoskeleton has good human–machine kinematic compatibility and can achieve promising force tracking in the presence of gait dynamics.

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