Design and Validation of a Modular, Backdrivable Ankle Exoskeleton

Area of Science:

• Robotics
• Biomechanics
• Human-Robot Interaction

Background:

• Partial-assist ankle exoskeletons face challenges balancing torque, control, compliance, and mass.
• Quasi-direct drive actuators offer a solution with inherent back-drivability and precise control.
• The M-BLUE system previously integrated these actuators for hip and knee assistance.

Purpose of the Study:

• To design and validate a back-drivable ankle exoskeleton module.
• To extend the modular M-BLUE system with ankle assistance capabilities.
• To enable bidirectional torque for studying control methods and gait in various users.

Main Methods:

• Developed a novel back-drivable ankle exoskeleton module.
• Utilized quasi-direct drive actuators for plantarflexion and dorsiflexion assistance.
• Benchtop testing of actuator performance and control bandwidth.
• Implemented an optimal task-agnostic energy shaping controller.
• Validated the system with a single human subject across activities of daily living.

Main Results:

• The ankle exoskeleton module demonstrates bi-directional torque capabilities.
• Benchtop tests confirmed actuator performance across position, voltage, and current control modes.
• The controller successfully provided biomimetic torque assistance during human subject experiments.
• The system is suitable for assisting ankle joints during various activities of daily living.

Conclusions:

• The new back-drivable ankle exoskeleton module effectively extends the M-BLUE system.
• The design allows for natural user interaction and precise torque assistance.
• This technology has potential for rehabilitation and augmenting human locomotion.