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.

Stiffness Compensation Through Matching Buckling Loads in a Compliant Four-Bar Mechanism

Abstract

In this paper, a novel alternative method of stiffness compensation in buckled mechanisms is investigated. This method involves the use of critical load matching, i.e., matching the first two buckling loads of a mechanism. An analytical simply supported five-bar linkage model consisting of three rigid links, a prismatic slider joint, and four torsion springs in the revolute joints is proposed for the analysis of this method. It is found that the first two buckling loads are exactly equal when the two grounded springs are three times stiffer than the two ungrounded springs. The force–deflection characteristic of this linkage architecture showed statically balanced behavior in both symmetric and asymmetric actuation. Using modal analysis, it was shown that the sum of the decomposed strain energy per buckling mode is constant throughout the motion range for this architecture. An equivalent lumped-compliant mechanism is designed; finite element and experimental analysis showed near-zero actuation forces, verifying that critical load matching may be used to achieve significant stiffness compensation in buckled mechanisms.

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