Coupled exoskeleton assistance simplifies control and maintains metabolic benefits: A simulation study

Area of Science:

• Biomechanics
• Robotics
• Human-Computer Interaction

Background:

• Assistive exoskeletons reduce walking's metabolic cost, with advances yielding significant savings.
• Current devices primarily assist single joints (ankle or hip).
• Multi-joint assistance promises greater savings but faces design complexity.

Purpose of the Study:

• Evaluate metabolic savings from multi-joint exoskeleton assistance using simulation.
• Identify promising joint combinations for assistive devices.
• Investigate coupled assistance strategies to simplify control.

Main Methods:

• Developed 2D muscle-driven simulations of walking.
• Optimized control strategies for simulated lower-limb exoskeleton devices to minimize metabolic cost.
• Compared single-joint, multi-joint independent, and multi-joint coupled assistance.

Main Results:

• Multi-joint devices (independent or coupled) provided 50% greater metabolic savings than single-joint devices.
• Coupled multi-joint assistance achieved most of the savings of independently controlled multi-joint devices.
• Simulations identified optimal torque profiles and metabolic power changes.

Conclusions:

• Multi-joint exoskeleton assistance significantly reduces metabolic cost.
• Coupled assistance strategies can simplify control design without sacrificing major metabolic benefits.
• Findings suggest reduced torque control parameters for efficient multi-joint exoskeleton design.