Researchers at the University of Michigan have developed a groundbreaking set of knee exoskeletons, designed using commercially available knee braces and drone motors, which have shown remarkable effectiveness in reducing fatigue during lifting and carrying tasks. These exoskeletons not only help users maintain proper posture while lifting, even when fatigued, but also play a key role in preventing job-related injuries by promoting better lifting techniques.

Robert Gregg, a professor of robotics at U-M and the lead author of the study published in Science Robotics, explained the innovative approach: “Rather than directly bracing the back and giving up on proper lifting form, we strengthen the legs to maintain it. This differs from what’s more commonly done in industry.”

Addressing a Critical Need in High-Risk Industries

In industries such as construction and manufacturing, where lifting is a regular part of the job, back braces and exoskeletons are often employed to protect workers. However, these traditional devices can be cumbersome, restrict movement, and primarily support the back, which may not be the most effective solution for injury prevention. The team at Michigan, however, took a different approach by designing knee exoskeletons that target the quadriceps muscles, offering a more practical and efficient solution for preventing back injuries while allowing for natural movement.

Impressive Test Results

To test the exoskeletons, participants were asked to perform various lifting and carrying tasks with a 20 lb kettlebell, including walking on inclines and stairs. The results were striking: participants who wore the exoskeletons were able to lift at almost the same speed as when they were fresh, even after experiencing fatigue. Without the exoskeletons, their lifting speed dropped significantly.

“These findings are especially important when a worker has to keep up with a conveyor belt,” noted Nikhil Divekar, a postdoctoral research fellow at U-M and the first author of the study. “When a worker is fatigued, they’ll keep up with the rate but with compromised posture. They’ll bend their back more, and that’s when injuries are most likely.”

Advanced Technology for Seamless Movement

The knee exoskeletons are designed with cutting-edge motors and gearing systems that allow users to move their knees naturally. Feedback from participants was overwhelmingly positive, particularly when walking on flat surfaces, where the exoskeleton provided just the right amount of support to the quadriceps.

The advanced software powering the exoskeletons uses data such as knee joint angles, leg orientations, and force measurements from sensors in the user’s shoes to anticipate the user’s movements. By making adjustments 150 times per second, the exoskeleton seamlessly adapts to various tasks, providing the perfect level of assistance. This is a major improvement over traditional exoskeleton controllers, which often struggle to switch between tasks and may take up to a full second to respond to the user’s intentions.

For example, when a traditional exoskeleton is programmed for climbing stairs, it may struggle to adjust when the user suddenly wants to descend. The new system, however, combines machine learning with physics modeling to avoid these complications and ensure smooth transitions between movements.

Looking Ahead: Making the Technology Accessible

The current lab prototypes of the knee exoskeletons cost around $4,000 per pair, but Gregg anticipates that mass production could reduce the price to approximately $2,000 per pair, making them more accessible to industries in need.

The study involved ten participants (five women and five men), each of whom performed various tasks on two different days: one when they were fresh, and one when they were fatigued. To induce fatigue, participants completed a series of squat lifts with a kettlebell until they required a lengthy break between repetitions. All participants were familiar with proper squat lifting techniques, ensuring accurate results.

With these impressive results, U-M’s knee exoskeletons present a promising solution for industries that rely on manual lifting, offering a safer, more efficient way to prevent injuries while improving worker productivity.

By Impact Lab