Robust nonlinear control of the hydroïd humanoid robotic arm: a comparative study of sliding mode strategies for high-precision trajectory tracking

Youssef Mahmoud, Mohamed Elasswad, Ahmed Abdellatif, Maya Sleiman, Khaled Khalil, Samer Alfayad

Abstract


This paper presents the modelling, control and performance evaluation of a redundant 7-DOF anthropomorphic robotic arm of HYDROÏD humanoid hydraulic robot. A kinematic framework based on the Denavit–Hartenberg (D–H) convention is developed and integrated with a biomimetic design that embeds physiological motion constraints. To bridge theory and implementation, the system is modelled in a CAD-to-Simscape Multibody environment, capturing nonlinear actuator dynamics, torque saturation, and joint coupling. A comparative analysis is conducted between linear and robust nonlinear control strategies, including State Feedback, LQR, SMC, TSMC, and STSMC. The controllers are evaluated through tracking of complex trajectories—rectangle, infinity, and parallelogram—under disturbance and payload variation scenarios. Results show that sliding mode-based controllers significantly outperform linear approaches, reducing RMSE from over 20° (linear controllers) to below 10° (SMC variants). STSMC achieves the highest steady-state accuracy with MAE as low as 0.44°, while TSMC provides superior robustness with maximum deviation limited to approximately 0.83°. These findings confirm the effectiveness of advanced sliding mode strategies for high-DOF humanoid robotic systems operating under realistic conditions.

 

Received: 26 April 2026

Accepted: 13 May 2026

Published: 17 June 2026


Keywords


Humanoid Robotics; Sliding Mode Control; Robust Nonlinear Control; Trajectory Tracking; Disturbance Rejection

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DOI: https://dx.doi.org/10.21622/RIMC.2026.03.1.2013

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Copyright (c) 2026 Youssef Mahmoud, Mohamed El Asswad, Ahmed Abdellatif, Maya Sleiman, Khaled Khalil, Samer Alfayad

Robotics : Integration, Manufacturing and Control

E-ISSN: 3009-7967

P-ISSN: 3009-6987

 

Published by:

Academy Publishing Center (APC)

Arab Academy for Science, Technology and Maritime Transport (AASTMT)

Alexandria, Egypt

rimc@aast.edu