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Walking position commanded NAO robot using nonlinear disturbance observer-based fixed-time terminal sliding mode.

Mahmoud Farhat1, Yassine Kali2, Maarouf Saad1

  • 1École de Technologie Supérieure, Montreal, H4R 0G3, QC, Canada.

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|December 27, 2023
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Summary

This study enhances humanoid robot walking stability using a Nonlinear Disturbance Observer (NDO) and Fixed-time Terminal Sliding Mode (FTSM) control. The NDO-NDO-based FTSM controller improves tracking performance and robustness against disturbances.

Keywords:
ChatteringFixed-time convergenceHumanoid robotsLyapunov functionSliding modeUncertain disturbanceWalking control

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Area of Science:

  • Robotics
  • Control Systems Engineering
  • Artificial Intelligence

Background:

  • Humanoid robot walking stability is challenged by complex nonlinear dynamics and external disturbances.
  • Existing control strategies often struggle with uncertainties and chattering phenomena.
  • The NAO robot serves as a platform to address these fundamental walking stability issues.

Purpose of the Study:

  • To introduce a novel control strategy for enhanced walking stability in humanoid robots.
  • To address the impact of uncertain external disturbances on robot locomotion.
  • To achieve robust and precise performance tracking for the NAO robot.

Main Methods:

  • Implementation of a Nonlinear Disturbance Observer (NDO) to estimate uncertainties and external disturbances.
  • Design of a novel Fixed-time Terminal Sliding Mode (FTSM) surface for rapid error convergence.
  • Application of Lyapunov stability theory to guarantee fixed-time stability of the system.
  • Real-time experimental validation on a humanoid NAO robot.

Main Results:

  • The NDO-based FTSM control law demonstrated robustness against uncertain perturbations.
  • The proposed controller significantly improved tracking performance during walking.
  • Reduced chattering phenomenon was observed compared to other control methods.
  • Effective validation on both flat and inclined surfaces.

Conclusions:

  • The developed NDO-based FTSM control strategy effectively enhances humanoid robot walking stability.
  • The controller provides robust performance and improved tracking accuracy under external disturbances.
  • This approach offers a promising solution for reliable humanoid robot locomotion.