Self-oscillating adaptive systems (SOAS) without limit-cycles

The SOAS is a model-following relay feedback system which automatically adjusts itself to give a reasonable gain margin and thus a good performance. The applicability of the SOAS has been limited since it generates limit cycles which are acceptable only in particular applications. By relating the original SOAS version with a recent output-feedback sliding adaptive control system, a modification is proposed which allows the elimination of the limit cycle. A further important property is that the modified SOAS, named Smooth Sliding Controller (SSC), can be made globally stable. Simulations and experimental results with a DC motor control are discussed.