Ergonomic Certification: How inertial motion capture improves conformity assessment

ErgoCert, otherwise known as the Ergonomics Certifying Institute, is the first certifying institute in Europe which deals specifically with ergonomics in workplaces, workstations and daily-use products. Using Xsens MVN Analyze, ErgoCert works to assess the physical exertions of users as they operate machinery, extracting biomechanical data from a realistic, user-environment that doesn’t fictionalize movements.

Attaining the certification is a must for any company looking to release both commercially available and work-specific products that meet user safety requirements. We sat down with Marco Bordignon, Technical Manager at ErgoCert, to discuss the institute’s certification methodology and how inertial motion capture provides the most accurate data for their assessments.

Oversight

All certifying bodies have inspectors and auditors to ensure consistency and proper application. The team at ErgoCert ensures that methodological rigor and cohesion.

“I’m responsible for all of our technicians and auditors in ergonomics. I’m also hugely involved in direct research and evaluating ergonomic research – I evaluate how the instruments are used and whether they meet compliance.”

Assessing Ergonomics

ErgoCert uses the Xsens system to acquire data from real operational modes performed by the users on machines in workplaces.

“If a company asks us to certify a specific machine or workplace, we request at least four real users—representative of different anthropometric percentiles of the product—to perform their everyday tasks as per usual. However, we ask them to wear Xsens suits whilst doing so. Then, we collect biomechanical data and feed it into our own custom, analysis software which includes acceptability limits deriving from international standards” explained Marco.

By assessing regular users of the machines in typical environments, ErgoCert can obtain realistic data based upon a standardized sequence of tasks, in order to assess possible biomechanical overload for the shoulders, elbows, wrists, back, and neck.

“Since product conformity evaluation on posture and ergonomics is based on international standards, we apply the data from Xsens to objectify the measures.”

“In particular, the standards require data from the shoulder, back, neck, posture and hand position. We don’t apply data related to elbows and wrists in the certification itself because they can be influenced by subjective movements and not necessarily by the machines in question,” said Marco.

Capturing biomechanics

When certifying products within the professional field, biomechanics is the most relevant factor of the assessment. This is because the procedure requires the same task to be repeated multiple times. In the consumer department, such as home appliances, usability is more important. Using Xsens suits, ErgoCert can operate in both fields.

“We certify both professional and consumer products – not all bodies have the skills to manage both. From our experience, Xsens is very easy to set up with a user. It’s easy to calibrate, and it’s not impacting the way the user moves. Before motion capture, all ergonomic evaluations and certifications were completed from observation alone,” explained Marco.

When the suits are combined with other peripheral measuring devices, ErgoCert can produce a more complete picture of the subject being researched – it’s this feature that sets Xsens’ inertial motion capture apart from camera-based systems.

“We sometimes integrate the system with other instruments for applied research, such as testing the instrument with eye-tracking technology and force glove.”

In a recent analysis conducted by ErgoCert, Unity 3D and Oculus Rift VR glasses were used to virtually evaluate new Electrolux Professional barrier washers – the image below depicts an example of back flexion evaluation, measured by Xsens.

Analysis

The team at ErgoCert extrapolate the kinematic data recorded with their own analysis software, designed to produce exact, mathematical results. The goal is to determine the dimensional effects of the machine, focusing on the biomechanics that are directly—and strictly—affected by the machine’s characteristics. This is the postural side of the analysis.

“Another parameter that we analyze is the frequency of complex actions, such as vehicle assembly cycles – it’s a combination of movements. So, we’re developing an algorithm that is analyzing combined movements and producing an analytical picture of the body’s full exertion. We also apply BoB (Biomechanics of Bodies),” exclaimed Marco.

BoB is a biomechanical modeling package that contains a human musculoskeletal model that generates all of the vital anatomical parts of the body. This works perfectly when translating data from the biomechanical model produced with MVN Analyze. ErgoCert utilized Xsens and BoB alongside force measurement systems to assess large-scale ovens, analyzing back compression forces associated with lifting different trays into the oven – the force measured was weight, using 5, 10 and 15kg trays.

“Previously, we did try an optics-based solution for particular tasks, but Xsens is the only inertial system we’ve tried and remains the go-to technology for our workplace evaluation and product certification procedures. We bought the first system 6 years ago, so we’ve got a very established experience with the systems. This year alone, we have recorded and analyzed more than 200 hours using our 3 inertial systems,” said Marco.

With ErgoCert’s certification being so integral to product manufacturers, Marco sees a continued and natural collaboration between Xsens MVN technology and the certification process.