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Robust hopping based on virtual pendulum posture control.

Maziar A Sharbafi1, Christophe Maufroy, Majid Nili Ahmadabadi

  • 1School of ECE, Control and Intelligent Processing Center of Excellence CIPCE, College of Engineering, University of Tehran, Tehran, Iran. sharbafi@ut.ac.ir

Bioinspiration & Biomimetics
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Summary

This study introduces a novel control approach for robust hopping, utilizing the virtual pendulum concept to stabilize the body. Event-based control of the virtual pivot point (VPP) significantly enhances stability and disturbance rejection in hopping robots.

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Area of Science:

  • Robotics
  • Biomechanics
  • Control Systems

Background:

  • Perturbed hopping requires precise vertical body alignment for stability.
  • The virtual pendulum concept, inspired by locomotion, uses ground reaction forces directed to a virtual pivot point (VPP).

Purpose of the Study:

  • To develop a robust hopping controller against perturbations in the sagittal plane.
  • To enhance stability, disturbance rejection, and convergence speed in hopping locomotion.

Main Methods:

  • A unified controller integrating virtual pendulum posture control with leg angle and length adjustment strategies.
  • Application to an extended Spring-Loaded Inverted Pendulum (SLIP) model including trunk, leg mass, and damping.
  • Stability analysis using Poincaré map and event-based control of VPP position with a linear quadratic regulator.

Main Results:

  • Fixed VPP position achieved moderate stability and disturbance rejection but with slow convergence.
  • Event-based VPP control significantly improved stability, convergence speed, and robustness against perturbations and parameter variations.
  • The enhanced SLIP model provided a more realistic simulation environment.

Conclusions:

  • The proposed virtual pendulum-based control approach offers a robust and efficient method for perturbed hopping.
  • Event-based VPP control is crucial for achieving high performance in dynamic locomotion tasks.
  • This controller design advances the development of more agile and resilient robotic locomotion systems.