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.

Kinematic Analysis and Optimal Design of a Novel Schönflies-Motion Parallel Manipulator With Rotational Pitch Motion for Assembly Operations

Abstract

This paper presents a novel Schönflies-motion Parallel Manipulator with RotationalPitch motion (SPM-RP) based on a single-platform fully parallel mechanism. An analysis of the position, workspace, velocity, and singularity of the SPM-RP is carried out in detail, and a dimensionless Jacobian is proposed to evaluate the manipulability of the SPM-RP. The analysis shows that the SPM-RP is with position-decoupled kinematics, a large singularity-free workspace, and excellent manipulability. The SPM-RP is actuated by four parallel prismatic actuators, enabling the manipulator to provide the identical kinematic performance at all generic cross sections perpendicular to the prismatic joint axes within its workspace. This paper thus proposes a reduced design optimization formulation, where the traditional optimization over the entire workspace is reduced to the optimization on a representative workspace cross section of the SPM-RP. According to this approach, the design optimization of the SPM-RP is carried out by maximizing its manipulability over the total orientation workspace, which is crucial for precision assembly. Based on the achieved optimal design, an SPM-RP prototype is developed. The mobility, orientation capability, total orientation workspace, and repeatability of the optimal design are tested and verified by the developed SPM-RP prototype. Experiments show that the SPM-RP can achieve a large total orientation workspace with excellent precision performance.
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