How Auburn Researchers Made Manhole Lifting Safer with Motion Capture

When Auburn University’s Iván Nail-Ulloa set out to measure the strain of lifting 400-pound manhole covers, motion capture data revealed the hidden risks behind the task. His findings led to the development of an assistive device that makes this demanding job safer and more ergonomic.

Challenge

Auburn University’s Biomechanical Engineering (AUBE) Lab postdoctoral fellow, Iván Nail-Ulloa, needed to accurately measure employees’ physical wellbeing. It was important for the motion capture solution to work in any environment, including locations with magnetic interference.

Solution

Ivan used Xsens to identify potential risk areas and develop an assistive machine that automatically lifts manhole covers, with minimal human assistance required.

Key takeaways

• Identifying the problem areas: Ivan and the team analysed lumbar spine loading, one of the most common injury areas during physical work
• High compressive force during manhole cover lifting: Ergonomic analysis revealed that workers’ backs are subjected to potentially harmful/injury-inducing forces with each manhole lifted
• Risk applies to multiple workers: Whether one or two people are lifting a cover, the force applied is still similar 

Ergonomic analysis is increasingly data-driven. Physical wellness at work takes technological evidence and extensive research to quantify. Postdoctoral fellow Iván Nail-Ulloa from Auburn University shares his project on ergonomics, reflects on the product he made to improve employee wellbeing, and shows how inertial motion capture provided the most accurate results.

Preparing for ergonomic analysis 

Funded by EPRI Occupational Safety and Health Program 62, Ivan began his project, “Assessing the accuracy of a wireless sensor system for estimating lumbar moments during manual lifting tasks considering the effects of load weight, asymmetry, and height”. It was designed to assess manual labor employees within their work environment and the adverse effects their tasks could have on their bodies, particularly for the lumbar spine. Lower-back pain is a well-known issue in the ergonomics industry, and Ivan wanted a technological method to study the cumulative exposure to physical risk factors. 

Traditionally, ergonomic solutions were created based on self-reported pain or company injury documents. “Things changed in the ergonomics industry when we could scientifically track data that provided tangible proof to employers of their employees experiencing pain,” explains Iván. “Having this information helps us find the exact issue with their workflow and provide a solution to stop injuries from happening.”

The dissertation project began in 2018 when Iván had to choose which technology was best suited for his research. “We decided to compare optical and inertial motion capture using biomechanical modeling,” he says. “Our study found that inertial motion capture data and optical motion capture data varied by 12-14%, showing that the small difference, coupled with flexibility gains, made the inertial method the ideal choice.”  After making this decision, Iván began to research different systems.

Creating a safe working environment for high-risk jobs 

A particular focus of Iván’s project was to enhance the occupational health and safety of power utility workers in New York. “Employees lift manhole covers that reach 400 pounds,” he mentions. “This is an extremely heavy load, and can be incredibly unsafe for those who have to lift it.” The workers use J-hooks that attach to the manhole covers and then haul them out of the way.

To effectively quantify the pressure experienced on the workers’ bodies, the Xsens system was the perfect solution. “Working on ergonomics in a real-world scenario is very fast-paced, and we had to stop traffic in New York to record the worker’s movements,” explains Iván. “Luckily with the ease of setup, we could quickly get the recordings without holding anyone up for too long.”

Given the particular setting and circumstances of this application, the research team knew they needed inertial motion capture to capture an accurate ergonomic analysis. Before Xsens, Iván found that machinery and nearby electronics would disrupt the technology’s electromagnetic field, so he had to search for a new option. The Awinda motion capture suit used in this study has magnetic immunity, making it the perfect use case in this context.

Measuring the impact of manhole cover lifting

The research found that a significant amount of stress was placed on the workers’ bodies during the initial movement of the manhole cover (peaking at 276-739 lbs of compressive force). This applied whether there were one or two people moving the cover at once. While the compressive forces remain below the recommended compression limit, given the number of times the employees could do this task in a day, the cumulative damage was proven to be a very serious topic to address. This is on top of another point of high force revealed to occur during the initial exertion of the mahnhole cover, resulting in significant torso flexion.

Gaining this valuable ergonomic research led to Iván and his team designing and building a power hook that automatically lifts manhole covers, eliminating the risk of injury. This technology enabled a reduction in peak compression force of 7-15%, and the improvement in the ergonomics was also noted anecdotally by the workers testing the new device, reporting that it “helps to keep a neutral back".

“This solution simply could not be found without objective movement data,” Ivan says. “We needed quantifiable figures to show the contractors that moving these manhole covers posed a significant risk to their workers.” 

Rapid results for occupational health and safety

Creating a safe working environment takes extensive planning and research to effectively quantify the workers’ needs. Ergonomic analysts do just this, but they need to have high-quality, accurate equipment to help them get the required information. 

Iván’s use of Xsens technology helped him make countless workers’ jobs safer through objective movement data. He needed pinpoint accuracy, and found that through biomechanical analysis and a reliable motion capture system, he could achieve just this.

Looking to the future, Iván plans to continue ergonomic research using inertial motion capture. “Xsens is perfectly suited to my needs, and shows just how important accuracy is in ergonomics,” he says. “The next thing we’ll focus on from this project is improving the automatic manhole lifter in terms of speed, which was an idea created as a result of our collected data and workers’ feedback.”

Interested in what Xsens can do for your ergonomic analysis? Take a look at our motion capture products.