Duffy [44] developed the theory which is applied to
the analysis of single-loop mechanisms, which are movable
polygons or open chains with one end fixed to the ground,
closed by an imaginary link between ground and a free end
where there is a mechanical hand or gripping device.
Hunt [45] has discussed all possible single- and multi-
degree-of-freedom kinematic pairs and used screw theory,
kinematic geometry and the techniques of linear algebra to
systematize in-parallel-actuated robot-arms. Mohamed and
Duffy [46] also applied screw theory to study the
instantaneous kinematics of the end-effector platform of
fully parallel robot-type device. Sugimoto [47] derived the
kinematic and dynamic model for a parallel manipulator by
using motor algebra and Newton-Euler formulation.
A comparison between the serial and parallel devices
in terms of some necessary and desirable performance and
control characteristics was presented by Cox [48]. There
are eight performance characteristics chosen as follows:
i. Range of motion
ii. Rigidity or stiffness and strength
iii. Complexity of end-effector positioning
formulation (computability)
iv. Complexity of system dynamics (computability)
v. Precision positioning
vi. Load carrying distribution through system
vii. Fabrication (economics)
viii. Compactness