Dynamic Performance of a SCARA Robot Manipulator With ...

IEEE TRANSACTIONS ON ROBOTICS, VOL. 25, NO. 1, FEBRUARY 2009 209
Fig. 2.
Simulation results for all four joints of a SCARA robot with variation in the first two link masses and the payload.
TABLE III
MAXIMUM ABSOLUTE DIFFERENCE BETWEEN PCT
AND MC FOR SCARA ROBOT
6) PCT has no problem with both underdamped and overdamped
type responses.
Additionally, this example also corroborates several of the known
advantages regarding the use of PCT. Specifically, PCT is more efficient
from a simulation time standpoint, allows dynamic changing of
parameters during the simulation, and yields a richer result that can be
utilized in other applications like controller design.
also opens the door for easy optimization of the controller gains for
the small amount of variation. Sensitivity studies can quickly and
effectively be performed for different controller gains.
V. CONCLUSION
This paper has shown in detail how to use PCT to analyze the
dynamic response of an open-loop mechanism by applying it to a
SCARA robot manipulator. Through this particular example, several
items were found.
1) PCT on the SCARA robot is feasible as long as the number of
unknowns are small. Automating the process further aiding in
speeding up the process. However, this even has its limits as
even the automated process is still cumbersome.
2) Using PCT on robotic applications requires a judicious choice of
states and formulation of the problem to make sure that nonlinearities
are not introduced into the equations.
3) PCT on a SCARA robot gives consistent results to a large MC
for a simple one-term expansion. This was true even using a
standard approximation of the trigonometric identities.
4) PCT exhibits “antinodes” (positions in the output where the
variation decreases significantly), even in this robotics example.
However, this was not noted on all joints.
5) PCT can be utilized with feedback control. However, integral
and nonlinear control poses some interesting problems that have
yet to be solved.
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