AAS 95-419

Frequency Response Characteristics of the Alternating Sign Learning Control Law

Y-C. Huang and R. W. Longman, Columbia University, New York, NY

Abstract

The possibility of poor transients in simple learning control methods has been illustrated in several previous works. By viewing the learning process in a modern state space formulation, the source of the poor transients was understood, and from this a novel concept of alternating the sign of the learning control gain was developed. Used alone, one of the signs would be associated with convergent learning and the other with a divergent unstable learning process. Nevertheless, when the sign is alternated it can produce a system converging to zero tracking error. This paper develops various properties of alternating sign learning control and alternating sign repetitive control, making use of two other approaches to viewing the transient behavior: frequency response characteristics and root locus plots.