Combined approaches to lightweight arm utilization

Abstract

In order to use lightweight arms the combination of a number of new approaches in arm design and control may be necessary. This paper describes four complimentary research efforts and how their results will work together. The bracing strategy is proposed first as one scenario of arm usage. It braces the arm against a passive structure to increase rigidity during fine motions of the end effector. Large motions of the arm require path and trajectory planning. Research on minimum time motions that avoid unnecessarily exciting vibrations is described next. The damping of those vibrations that are excited can be accomplished through a combination of active modal feedback control and passive damping. The enhancement of the damping characteristics of arm structures is described. This is important for stable feedback control with actuators and controllers with limited bandwidth. Analytical and experimental results for constrained layer damping are described. in the context of the control problem. An active modal control has been implimented on a simple one link beam. As higher bandwidth is sought from this physical system deviations from the predicted results were observed. A refinement of the model to include anti-aliasing filter, sample-data, and amplifier effects explains the behavior as explained.