IEEE Transactions on Robotics and Automation 4:6 (December 1988)

THE MOTION OF A PUSHED, SLIDING WORKPIECE

M. A. Peshkin
A. C. Sanderson

Robotics Institute, Carnegie-Mellon University

ABSTRACT

It occurs frequently in robotic applications that a robot 
manipulates a workpiece which is free to slide on a work surface. 
Because the pressure distribution supporting the workpiece on 
the work surface cannot in general be known, the motion of the 
workpiece cannot be calculated uniquely.  Yet despite this 
indeterminacy, several researchers have shown that sliding 
motions can be employed to accurately align workpieces without 
visual or other feedback. 

Here we find the locus of centers of rotation of a workpiece for 
*all* possible pressure distributions.  The results allow a 
quantitative understanding of open-loop robot motions which 
guarantee the alignment of a workpiece. Several sample problems 
are solved using the results, including the distance that a flat 
"fence" or robot finger must push a polygonal workpiece to 
assure that a facet of the workpiece comes into alignment with the 
fence.  

KEYWORDS

Center of rotation, sliding, slipping, pushing, 
grasping, manipulation, friction. 

ACKNOWLEDGEMENTS

This work was  supported by a grant from Xerox Corporation
and by the Robotics Institute, Carnegie Mellon University.