Kinematic Analysis and Optimization of a New Three Degree-of-Freedom Spatial Parallel Manipulator

Abstract

A study of the kinematic characteristics of a three degree-of-freedom (dof) parallel mechanism is presented. The architecture of the mechanism is comprised of a mobile platform attached to a base through three identical prismatic-revolute-spherical jointed serial linkages. The prismatic joints are considered to be actuated. These prismatic actuators lie on a common plane and have radial directions of action. The mechanism's inverse displacement solution is obtained. Since the mechanism has only 3 dof, constraint equations describing the inter-relationship between the six motion coordinates are derived. These constraints allow the definition of parasitic motions, i.e., motions in the three unspecified motion coordinates. Architecture optimization of the device is undertaken demonstrating that specific values of design variables allow minimization of parasitic motion.

Controlling the Dynamics and Stabilization of the Altitude and Attitude of An Underactuated Tri-rotor UAV

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Solving the double-banana rigidity problem: a loop-based approach

“…Another term one encounters in this setting is "redundant DOF" (Zhang et al, 2003), which however may lead to confusion as the term redundant DOF is used in robotics for robots featuring a greater number of actuators than necessary for a given task space which allows for special control movements (such as the human arm having seven relative joint motions for six DOFs at the hand). In some cases the term "parasitic DOF" is used for isolated DOFs (Rolland, 1999); however, the term "parasitic motion" (Carretero et al, 2000) or "parasitic DOF" is also (and more frequently) used to describe unwanted dependent motions in some direction such as the vertical axis of a lower mobility platform (Hsu et al, 2004;Isaksson et al, 2015;Merlet, 2005). As a further variant one finds the term parasitic degrees of freedom meaning additional degrees of freedom added to the principal DOFs by compliant joints (Togashi et al, 2014).…”

A Comparison Study on Motion/Force Transmissibility of Two Typical 3-DOF Parallel Manipulators: The Sprint Z3 and A3 Tool Heads

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