knee exoskeleton human safety technology

Researchers Unveil Multifunctional Knee Exoskeletons to Enhance Safety in Lifting Tasks

Introduction

Researchers at the University of Michigan engineered knee exoskeletons using drone motors and commercial knee braces to alleviate fatigue in lifting tasks. The devices improved lifting posture and reduced injury risks, as published in Science Robotics.

Innovative Approach

Departure from Conventional Methods

Robert Gregg, U-M robotics professor and lead study author, stated, "Our method emphasizes leg strengthening to preserve proper lifting posture, rather than relying solely on back support, a departure from conventional industry methods."

Comparison to Existing Solutions

"Back braces are already commonly used by workers in construction and manufacturing, where frequent lifting is required. New back exoskeletons using motorized assistance are emerging, but they often assume improper lifting techniques and are inconvenient for other movements, requiring deactivation," Gregg stated.

Unique Features of the Knee Exoskeletons

Support for Quadriceps

According to the Michigan research group, their knee exoskeletons uniquely support the quadriceps, which are vital for effective squat lifting. This novel solution aims to reduce the risk of back injuries in a less obtrusive manner.

Task Performance Evaluation

Study subjects evaluated the exoskeletons while performing lifting and carrying tasks with a 20-pound kettlebell.

The tasks tested in the study included weight lifting and carrying on flat ground, inclines, and stairs. The results revealed that, after fatigue set in, exoskeleton users were able to maintain better posture and experienced only a 1% reduction in lifting speed, compared to a 44% decrease observed without the exoskeletons.

Participant Feedback and Performance

Challenges During Fatigue

"When workers are fatigued, keeping up with a conveyor belt can be particularly challenging," remarked Nikhil Divekar, postdoctoral research fellow in robotics at U-M and first author of the study. "They tend to maintain the conveyor's speed while adopting poor posture, which often leads to more severe back bending and a higher risk of injury."

Satisfaction and Comfort

Participants generally experienced significant benefits from the exoskeletons, indicating high satisfaction, except for level ground walking, where their contentment was more subdued. This is consistent with the limited support the quadriceps need for the easy task; Gregg described the exoskeleton's assistance as just adequate to counterbalance its own weight.

Technological Aspects

Motor Design and Software Integration

A crucial factor in the exoskeleton's comfort its motor design and gearing, which allow users to move their knees naturally and maintain a fluid gait. Additionally, the software plays a key role by assessing the user's needs for assistance based on knee joint angles, thigh and lower leg orientations, and force data collected from a sensor in the user's shoe.

Adaptive Control System

By analyzing these three measurements from both legs, the system can determine the user's intended motion and the appropriate level of assistance. These measurements, captured 150 times per second, allow the exoskeletons to transition smoothly between different activities.

Comparison with Traditional Controllers

Greater Adaptability

In contrast to many exoskeleton controllers that operate based on fixed task patterns, this approach offers greater adaptability. Gregg explained that traditional controllers can experience difficulties when changing tasks and may take as long as a second to determine the user's intended motion.

"A potential issue arises if the exoskeleton is trying to move upstairs while you're attempting to move downstairs," he explained.

Advanced Control Features

The new controller's use of both a physics model and machine learning helps prevent the exoskeleton from making unanticipated moves if the user's actions deviate from the activity patterns learned during training.

Future Prospects

Cost and Production

Currently, lab prototypes are priced at approximately $4,000 per pair. Gregg estimates that with mass production, the cost could potentially drop to around $2,000 per pair.

Next Steps

Ten participants, five of each gender, completed all tasks on two separate occasions: once when well-rested and once when fatigued. Fatigue was induced by having participants perform kettlebell squat lifts until they could no longer continue without taking extended breaks. All participants were already skilled in proper squat lifting techniques.

The team has pursed patent protection with help from U-M Innovation Partnerships and is currently exploring partnership opportunities to launch the technology commercially.

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