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Observer-based controller for nonaffine time-delayed systems subject to input nonlinearities, state constraints, and unknown control direction

Mohit, M ; Sharif University of Technology | 2022

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  1. Type of Document: Article
  2. DOI: 10.1002/acs.3450
  3. Publisher: John Wiley and Sons Ltd , 2022
  4. Abstract:
  5. In this work, an adaptive observer-based control scheme has been designed for uncertain nonaffine nonstrict feedback systems subject to state time delay, various types of input nonlinearities, time-varying asymmetric state constraints, and unknown control direction. Compared to the existing controllers for systems with state constraints, the designed control scheme in this work can be applied to state-constrained systems with nonaffine structure subject to state delays, unknown control direction, and different types of input nonlinearities, while full-states measurement is not required. Moreover, by introducing a novel saturated Nussbaum function in the present work, not only has the problem of unknown control direction been handled, but also the probability of a control shock due to applying the conventional Nussbaum functions has been eliminated. The system unknown dynamics has been approximated by using neural networks (NNs), and by updating the maximum norm of NNs weight vectors, only one adaptive law is required for the controller implementation. By employing appropriate Lyapunov functions, it has been shown that all signals in the closed-loop system are bounded, state constraints are satisfied, and the output tracking error can be made small by selecting appropriate design parameters. The effectiveness of the designed control scheme has been shown through two simulation studies. Moreover, the superiority of the proposed saturated Nussbaum function in comparison with conventional Nussbaum functions has been shown via simulation. © 2022 John Wiley & Sons Ltd
  6. Keywords:
  7. Input nonlinearity ; Nonstrict feedback systems ; Adaptive control systems ; Control nonlinearities ; Controllers ; Delay control systems ; Feedback control ; Lyapunov functions ; Time delay ; Approximators ; Control schemes ; Feedback systems ; Input nonlinearities ; Intelligent approximator ; Non-strict-feedback ; Nonstrict feedback system ; Nussbaum functions ; State constraints ; Unknown control direction ; Closed loop systems
  8. Source: International Journal of Adaptive Control and Signal Processing ; Volume 36, Issue 8 , 2022 , Pages 2122-2149 ; 08906327 (ISSN)
  9. URL: https://onlinelibrary.wiley.com/doi/abs/10.1002/acs.3450