Christopher L. Lewis's MSEE Thesis Abstract

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.