Quantifying naturalistic occupant postures in belt-positioning booster seats through pressure mapping.
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Date
2024-03
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Abstract
Background and Objective: Previous studies have shown that belt-positioning booster (BPB) characteristics influence occupant posture as they contribute to the occupant’s comfort during use. Slouching is a common out of position (OOP) posture associated with comfort that is assumed by BPB occupants to accommodate for long seat lengths. This posture is particularly concerning because of its association with injuries in the event of a crash. Previous work that has investigated BPB occupant postures has been limited in the ability to fully quantify slouched postures due to limitations in data collection techniques that occluded the pelvis. Further, these works were primarily focused on ideal, instantaneous occupant postures. It is pivotal to understand naturalistic (time-dependent, non-ideal) postures so future testing of crash surrogates can more accurately represent pediatric occupants. This will improve BPB design and injury mitigation strategies. Therefore, the objective of this study was to collect quantitative data to describe naturalistic postures of BPB occupants over extended periods of time using novel applications of pressure mapping.
Methods: Thirty booster-age children (5 to 12 years old) were recruited. Five seating configurations were used to manipulate booster profile (high, low, or no BPB) and the presence of armrests (armrests present or none), using two low back BPB models and captains’ chairs from a current model minivan. Two captain’s chairs were arranged within the laboratory to mimic the front and rear rows of a vehicle interior. Volunteers were randomly assigned to two of the five seating configurations, which were implemented in the rear row captain’s chair. TekScan 5250 pressure mats were arranged to cover the BPB seating surface. Cameras were positioned to record the occupant’s behaviors over time. Each trial lasted thirty minutes during which center of force (COF) position from pressure maps was continuously collected, along with video and posture data from XSENS inertial measurement units. Every ten minutes the volunteers were provided a two-question survey to evaluate their comfort.
Results: Children assumed a variety of postures over the thirty minutes from remaining stationary to frequent changes. There were no significant differences in COF average fore-aft position, or maximum relative translation based on BPB seating configuration. Assessing translation of COF over time showed significant differences between BPB profiles and with respect to time, with an average forward translation of 2.47 cm from ideal reference positions over the 30-minute period (p=0.0028), the greatest translation occurring in low-profile and baseline configurations.
Discussion and Conclusions: This is the first study to report pressure mapping metrics for BPB occupants over time. On average, volunteers trended towards slouched postures, evidenced by a forward translation of their COF within seating configurations over the 30-minute period. These data can be applied in future surrogate models to accurately assess the implications of naturalistic BPB occupant postures. Future work should continue to investigate these postures in more realistic, on-road environments and explore the influence of additional BPB features in promoting prolonged ideal positions throughout the entirety of motor vehicle travel.
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Engineering: 1st Place (The Ohio State University Edward F. Hayes Advanced Research
Forum)
Keywords
Belt-positioning booster seats, Pressure mapping, Pediatric occupant biomechanics, Volunteer study, Injury prevention