Incorporation of Payload Uncertainties into Robot Trajectory Planning

A number of trajectory planning algorithms are available for determining a time history of the joint torques, positions, and velocities required to move a manipulator along a given geometric path in minimum time. These schemes require knowledge of the robot´s dynamics, which in turn depend upon the characteristics of the payload which the robot is carrying. In practice, the dynamic properties of the payload will not be known exactly, so that the dynamics of the robot, and hence the required joint torques, must be calculated for a nominal set of payload characteristics. But since these trajectory planners generate nominal joint torques which are at the limits of the robot´s capabilities, moving the robot along the desired geometric path at speeds calculated for the nominal payload may require torques which exceed the robot´s capabilities. In this paper, bounds on joint torque uncertainties are derived in terms of payload uncertainties. This allows the trajectory planner to incorporate payload uncertainties into the trajectory planning process.