Spatial Robust Whole-Body Dynamic Trajectory Optimization of a Lower-Limb Exoskeleton.

Area of Science:

• Robotics
• Biomechanics
• Control Systems

Background:

• Lower limb exoskeletons require robust control strategies to manage external perturbations and ensure user safety.
• Current trajectory optimization methods often do not explicitly account for disturbance rejection capabilities.

Purpose of the Study:

• To design spatial (3D) robust reference trajectories for lower limb exoskeletons using trajectory optimization.
• To enhance the exoskeleton's ability to reject perturbations by maximizing a defined robustness metric.

Main Methods:

• Augmented trajectory optimization by incorporating a robustness metric maximization.
• Defined robustness as the minimum force at the Center of Mass that cannot be rejected without violating system constraints.
• Designed dynamic trajectories for level walking, side-stepping, and stair ascent.

Main Results:

• The proposed method significantly increased the robustness metric compared to nominal trajectory optimization.
• Successfully demonstrated increased robustness against external forces.
• Validated the practical feasibility of the optimized trajectories through implementation on a lower limb exoskeleton.

Conclusions:

• Optimized robust trajectories enhance the disturbance rejection capabilities of lower limb exoskeletons.
• The developed method is feasible and effective for real-world exoskeleton applications, including assisting paraplegic users.
• This approach improves the safety and performance of lower limb exoskeleton control systems.