A modified model reference adaptive control approach for systems with noise or unmodelled dynamics

Select a Journal Proc IMechE, Part F: Journal of Rail and Rapid Transit more options Search Query Builder Close | Clear Title (ti) Abstract (ab) Author (au) ISSN (issn) DOI (doi) And Or Not ( ) * (wildcard) Within all content Within this journal Within this issue Export this article Export this article as RIS | Text PDF (265.9 KB) Authors S A Neild1, L Yang1, D J Wagg1 1 Department of Mechanical Engineering, University of Bristol, Bristol, UK Abstract In this paper, a modified model reference adaptive control (MRAC) strategy is developed for use on plants with noise or unmodelled high-frequency dynamics. MRAC consists of two parts, an adaptive control part and a fixed gain control part. The adaptive algorithm uses a combination of low- and high-pass filters such that the frequency range for the adaptive part of the strategy is limited. The mechanism for noise-induced gain wind-up is demonstrated analytically, and it is shown how MRAC can be modified to eliminate this wind-up. Further to this, an additional filter is proposed to improve MRAC robustness to high-frequency unmodelled dynamics. Two test plants, one with added noise and the other with unmodelled high-frequency dynamics, are considered. Both plants exhibit unstable behaviour when controlled using standard MRAC, but, with the modified strategy, robustness is significantly improved.