Optimal design of a redundant spherical parallel manipulator

Abstract

A new kinematic design of a parallel spherical wrist with actuator redundancy is presented. A special feature of this parallel manipulator is the arrangement of co-axial actuators which allows unlimited rotation about any axis inside a cone-shaped workspace. A detailed kinematic analysis has shown that actuator redundancy not only removes singularities but also increases workspace while improving dexterity. The structure optimization has been performed with a global dexterity criterion. Using a conditioning measure, a comparison with a non-redundant structure of the same type was performed and shows that a significant improvement in dexterity has been obtained.

Inverse-kinematics-based control of a redundantly actuated platform for rehabilitation

“…Obviously, this affects the dexterity of the mechanism meaning that for certain postures within the workspace, the mechanism is not able to produce forces and torques to complete its task. Actuation redundancy has been presented by several researchers as a way to eliminate mechanism singular postures and improve mechanism dexterity [17][18][19][20][21][22]. A study of different mechanism geometries, in the presence and absence of actuation redundancy, for the parallel mechanism studied in this paper was presented in reference [23], where the concept of over-actuation was applied to completely remove mechanism singularity and improve the dexterity of the parallel mechanism.…”

Optimal kinematic design of a haptic pen

“…This is fine for translations but non-uniform sample spacing [17] and an unsuitable workspace boundary (see Figure 9a) result if Euler angles are used to compute rotations. An axis-angle representation R=(θ 0 ,θ 1 ,θ 2 ) (see Figure 9) leads to a more suitable workspace boundary by bounding θ 0 and θ 1 while leaving θ 2 unconstrained ( ) .…”

“…For the Twin-Pantograph, Q 1 is applied to q 1 and Q 2 is applied to q 7 since the waist (q 1 ), wrist (q 7 ) and shoulder (q 2 , q 3 , q 5 , q 6 ) joints have the most dissimilar torque demands. The resulting joint-space scaling matrices (S J ) are shown in (17) for the Twin-Pantograph and in (18) for the parallel platforms.…”

A Case Study of Planar 3-RPR Parallel Robot Singularity Free Workspace Design

“…In [12], singularity elimination methods including passive joint activation, braking, and bracing are presented. In [10], actuator redundancy is introduced as a design method to eliminate singularities and increase workspace. Li [17] introduces a procedure to determine maximal singularity-free zones of the 3 − RP R parallel mechanisms.…”