Title: A modified adaptive control scheme in the presence of input saturation

Authors: Natsuki Takagi; Kazuya Sato; Masahiro Oya

Addresses: Department of Mechanical Engineering, Miyakonojo National College of Technology, 473-1 Yoshio-cho, Miyakonojo-shi, Miyazaki, 885-8567, Japan. ' Department of Mechanical Engineering, Faculty of Science and Engineering, Saga University, 1 Honjo-machi, Saga-shi, Saga, 840-8502, Japan. ' Department of Mechanical and Control Engineering, Kyushu Institute of Technology, 1-1 Sensui-cho, Tobata-ku, Kitakyushu-shi, Fukuoka, 804-8550, Japan

Abstract: We have proposed a model reference adaptive control scheme (conventional control scheme) for continuous time single-input single-output linear systems with an input saturation. In the closed-loop system using the conventional control scheme, it has been shown theoretically that the tracking error between the controlled object output and the reference model output can converge to zero. Moreover, it has been also shown theoretically that tracking performance can be improved by setting only one design parameter. However, there is the indispensable condition that initial states in the tracking error system must satisfy. To meet the condition, many design parameters have to be adjusted. In the paper, in order to save the time spent to meet the condition for initial states, the main attention is focused on reduction of the design parameters to be adjusted. To achieve the reduction of the design parameters, we modify the conventional control scheme and propose a new adaptive control scheme. As a result of analysing stability of the closed-loop system using the new control scheme, a new condition for initial states is derived. It should be emphasised that we can apply the new control scheme in a larger region of initial states compared with the conventional control scheme.

Keywords: model reference adaptive control; input saturation; control performance improvement; relaxation of restricted conditions; tracking performance; design parameters.

DOI: 10.1504/IJAMECHS.2011.042613

International Journal of Advanced Mechatronic Systems, 2011 Vol.3 No.3, pp.168 - 180

Published online: 19 Sep 2011 *

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