Industrial exoskeletons seem to be a promising new way to help control ergonomic risk factors and improve productivity. Their use appears poised to grow quickly over the next several years. But reports from some early trials are mixed, indicating there are still concerns to be addressed. What are some of the issues that safety professionals need to consider?
Exoskeletons work by amplifying the forces applied by a worker’s muscles, or by off-loading some of the weight of tools and other objects being handled by the worker. But every action has an equal and opposite reaction – in most cases, this reaction force is transferred to or spread over other parts of the body. Some exos do transfer force to the floor, but this requires a larger, more cumbersome and heavier exo. Studies are ongoing to determine whether the reduced strain on some muscles is worth the increased strain or contact pressure on other parts of the body.
The cumbersome nature of exos can add additional ergonomic and safety hazards. The joints and limbs of an exo are intended to move in tandem with the joints and limbs of the wearer. But if an exo’s joint is not lined up properly with a worker’s joint, the two joints will be pulled together as they are flexed.
The human is the weak link in this system – there is the potential for injury from force against the joint or contact pressure from the exo harness pulling on the limb. The careful fit of the exo ensured in R&D trials may not be achieved in the factory or construction site. Most industrial exoskeletons are currently the passive type, with the assistive force provided by springs and locking joints. As powered exos with more forceful actuators become more common, the chance of these types of injuries increases.
Exoskeleton joints also may not have the range of motion of human joints, restricting the wearer’s movements. The worker may push against the exo in a direction it doesn’t move, adding to their fatigue over time. Even as they learn the “proper”, restricted motions, this may not be ideal ergonomically. As we have learned from office ergonomics, even staying in the “ideal” seated posture for long periods becomes uncomfortable and unhealthy – “The best position is your next position”.
This restricted range of motion, the likely imperfect fit of the exo, and amplified muscle forces can result in safety hazards as well. Climbing stairs, moving out of the way of a falling box, or other actions requiring quick, accurate or reflexive motion may be impaired. Falls and other injuries could occur. Again, as powered exos become more common, the chance of injury increases.
As with any change in the workplace, employee involvement is critical to ensure success. In the case of exoskeletons, employee feedback from published studies has been mixed. Some workers liked the exos and wanted to continue using them, others didn’t like them, and most were neutral. Their responses seemed to be related to how well the exos fit and whether they were appropriate for the tasks being performed.
As exoskeletons enter our workforce, it is important to review them as you would any new tool or machine – consider both the increases in productivity and safety, and where new safety hazards might be introduced.
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