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Switching Assistance for Exoskeletons During Cyclic Motions
Nevio Luigi Tagliamonte1, Simona Valentini1, Angelo Sudano1
1Biomedical Robotics and Biomicrosystems Research Unit, Department of Engineering, Università Campus Bio-Medico di Roma, Rome, Italy.
Frontiers in Neurorobotics
|July 6, 2019
Summary
This study introduces a new control algorithm for exoskeletons that reduces muscular effort during cyclic movements by injecting energy optimally. The novel controller decreased knee extensor muscle activity by 10-20% in most trials without affecting movement speed.
Area of Science:
- Robotics
- Biomechanics
- Control Systems
Background:
- Cyclic movements, such as walking, require significant muscular effort, particularly during energetically demanding phases.
- Existing exoskeleton control strategies may introduce perturbations or fail to optimize energy transfer.
- Reducing user muscular effort is crucial for enhancing the effectiveness and user acceptance of assistive robotic devices.
Purpose of the Study:
- To propose and evaluate a novel control algorithm for torque-controlled exoskeletons designed to assist cyclic movements.
- To minimize user muscular effort by optimizing the timing of energy injection into the human-robot system.
- To assess the impact of the control algorithm on muscular activity and spatio-temporal characteristics of cyclic movements.
Main Methods:
- Development of a novel control algorithm based on injecting energy parcels at moments of maximum angular momentum.
- Implementation of the algorithm in a torque-controlled exoskeleton system for assisting cyclic knee movements.
- Measurement of electromyographic (EMG) activity of knee flexor-extensor muscles to quantify muscular effort.
- Analysis of spatio-temporal parameters, including swinging speed, to assess movement perturbations.
Main Results:
- The proposed controller significantly reduced muscular activity in knee extensor muscles by 10-20% in 83% of trials.
- No significant effect on swinging speed was observed, with variations below 10% in 92% of trials.
- In cases where muscular activity increased, the increment was less than 10% and statistically significant.
Conclusions:
- The novel control algorithm effectively reduces muscular effort during the extension phase of cyclic movements, particularly against gravity.
- The algorithm minimizes perturbations to the natural spatio-temporal characteristics of the movement.
- This approach is highly suitable for applications requiring exoskeleton-assisted cyclic motions, improving user comfort and reducing fatigue.
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