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Christopher L. Lewis's MSEE Thesis Abstract

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On-Line Trajectory Generation for Robots Cooperating to Perform an Assembly Task

M.S.E.E., Purdue University, August 1990

Major Professor: Anthony A. Maciejewski

The poor dexterity of commercial robots is due in part to their single
arm structure. The development of multiple robotic systems will
overcome this limitation. The kinematic control of single arm robots
is well developed, but motion control of multiple robots is still in
its infancy. This thesis formulates an algorithm for on-line
trajectory generation for two robots cooperating to perform a task.
The two robots are treated as a single redundant system. A Jacobian
is formulated that relates the joint rates of the entire system to the
relative motion of one of the hands with respect to the other.
Solving for the minimum norm solution to this relative Jacobian
equation at each iteration provides a set of joint rates which
performs the cooperative tasks. In addition to the cooperative task,
secondary goals are satisfied using velocities in the null space of
the relative Jacobian. For this purpose and for operating the robots
independently, a second, composite, Jacobian is formulated. A
weighted solution of the composite Jacobian equation constrained to be
in the null-space of the relative Jacobian provides for collision and
joint limit avoidance, and absolute orientation constraints. The
weighting provides a means for specifying the relative importance of
the secondary criteria. An unconstrained solution of the composite
Jacobian equation provides the necessary motion for operating the
robots independently. Collision avoidance during independent mode is
made possible by using a weighted minimum norm solution of the
composite Jacobian equation.