Design, control and validation of the variable stiffness exoskeleton FLExo.

Area of Science:

• Robotics
• Biomechanics
• Assistive Technology

Background:

• Upper limb assistive devices often lack natural control and force feedback.
• Existing exoskeletons may not effectively replicate human muscle dynamics.
• Controlling assistive devices based on biological muscle parameters remains a challenge.

Purpose of the Study:

• To design and validate a one-degree-of-freedom assistive platform for upper limb strength augmentation.
• To develop a novel control strategy that maps muscle activation directly to exoskeleton behavior.
• To investigate the efficacy of a variable stiffness actuator that mimics antagonistic muscle function.

Main Methods:

• Development of a variable stiffness actuator replicating antagonistic muscle pairs.
• Implementation of a control system mapping estimated muscle activations (via ElectroMyoGraphic (EMG) sensors) to the exoskeleton.
• Tuning of mechanical parameters to achieve analogy with human muscle system threshold lengths.
• Experimental validation of the platform and control strategy.

Main Results:

• The assistive platform successfully augmented upper limb strength.
• The novel control strategy effectively exploited the muscle-like dynamics of the actuator.
• Experimental results demonstrated a substantial reduction in subject muscle effort.
• The exoskeleton joint stiffness was inherently controlled through the mapping strategy.

Conclusions:

• The developed assistive platform and its muscle-analogue control strategy are effective.
• This approach offers a promising method for enhancing human-machine interaction in assistive robotics.
• The findings suggest potential for more intuitive and effective upper limb exoskeletons.