  We investigate energy-optimal control of robots with ultracapacitor based
regenerative drive systems. Based on a previously introduced framework, a
fairly generic model is considered for the robot and the drive system. An
optimal control problem is formulated to find point-to point trajectories
maximizing the amount of energy regenerated and stored in the capacitor. The
optimization problem, its numerical solution and an experimental evaluation are
demonstrated using a PUMA 560 manipulator. A comprehensive experimental setup
was prepared to evaluate power flows and energy regeneration. Tracking of
optimal trajectories was enforced on the robot using a standard robust
passivity based control approach. Experimental results show that when following
optimal trajectories, a reduction of about 13\% in energy consumption can be
achieved for the conditions of the study.
