Alison Godwin

Accuracy of Inertial Motion Sensors in Static, Quasistatic, and Complex Dynamic Motion

Inertial motion sensors (IMSs) combine three sensors to produce a reportedly stable and accurate orientation estimate in three dimensions. Although accuracy has been reported within the range of 2 deg of error by manufacturers, the sensors are rarely tested in the challenging motion present in human motion. Their accuracy was tested in static, quasistatic, and dynamic situations against gold-standard Vicon camera data. It was found that static and quasistatic rms error was even less than manufacturers technical specifications. Quasistatic rms error was minimal at 0.3 deg (+/-0.15 deg SD) on the roll axis, 0.29 deg (+/-0.20 deg SD) on the pitch axis, and 0.73 deg (+/-0.81 deg SD) on the yaw axis. The dynamic rms error was between 1.9 deg and 3.5 deg on the main axes of motion but it increased considerably on off-axis during planar pendulum motion. Complex arm motion in the forward reaching plane proved to be a greater challenge for the sensors to track but results are arguably better than previously reported studies considering the large range of motion used.

Functional data analysis as a means of evaluating kinematic and kinetic waveforms

Researchers use peak and mean characteristics to quantify changes in kinematics and kinetic loading patterns. The variability of human motion warrants a more complex method of analysis. This paper will demonstrate that functional data analysis (FDA) can quantify differences throughout a lifting waveform that would not be evident when applying standard statistical methods to discrete variables. A functional ANOVA was used to identify variation in kinematic and kinetic waveforms resulting from fatigue experienced over a 45-min lifting task. Only trunk angular motion and hip angular velocity were significantly different across the work task using discrete peak values. FDA was able to demonstrate that additional areas outside of the peaks were significantly different in the late phase for several waveforms. FDA was able to demonstrate significant variation across the work period for kinetic and kinematic variables when statistics performed on discrete variables reported no variation. More robust methods for follow-up procedures were recommended.

Evaluating the reliability of assessing home-packed food items using digital photographs and dietary log sheets.

OBJECTIVEnTo assess the reliability of manual data entry for home-packed food items by using digital photographs and dietary log sheets.nnnMETHODSnData from 60 lunches were entered by researcher A and B independently. Researcher B re-entered researcher As items within 1 week. Researcher B then re-entered her items 4 weeks from the initial entry point.nnnRESULTSnThe inter-rater reliability intraclass correlation coefficient (ICC) was 0.83 for total kilocalories and ranged from 0.75-0.87 for macronutrients. The intra-rater reliability ICC was 0.92 for total kcal and ranged from 0.90-0.92 for macronutrients. The inter-rater ICCs for the 5 selected micronutrients ranged from 0.33-0.83, whereas the intra-rater ICCs for these micronutrients ranged from 0.65-0.98.nnnCONCLUSIONS AND IMPLICATIONSnThis method of data entry is feasible and its reliability is promising forxa0macronutrient investigations. Continued assessment of this method for investigations related to micronutrient content is recommended.

Examination of vibration characteristics, and reported musculoskeletal discomfort for workers exposed to vibration via the feet

The frequency and amplitude characteristics of vibration experienced at the feet under typical mining equipment operation were documented in this study. Foot-transmitted vibration (FTV) was measured using a tri-axial accelerometer mounted at the location where the worker stood. A musculoskeletal disorder questionnaire, work history and demographic information were also collected. Vibration from locomotives (primary source exposure) had a dominant frequency below 6.3 Hz; whereas, drilling and raise platforms (secondary source exposures) were predominantly in the 31.5 to 40 Hz range. All workers reported lower limb discomfort and two had been diagnosed with vibration induced white feet. All raise platforms exposed the workers to vibration levels that placed them above the ISO 2631–1 health guidance caution zone for an 8-hour exposure. Further investigation using both ISO 2631–1 and ISO 5341–1 standards is needed to determine long-term health effects to the whole-body and feet of workers exposed to FTV.

Classic JACK modelling of driver posture and line-of-sight for operators of lift-trucks

Several reports indicate that lift-truck (LT) drivers may be at higher risk for developing musculoskeletal injuries due to postures that must be adopted in order to manoeuvre the LT in industrial workplaces. This research uses a human simulation program to quantify changes to line-of-sight (LOS) using driving simulations acquired from actual drivers in a closed arena setting. Video files acquired during the mock-up were decimated to 3 Hz and the resulting video files were coded in 3D Match. The resulting posture file was used to drive the animation tool in Classic JACK v4.1 human simulation software while quantifying LOS with additional virtual tools. On average, the drivers adopted awkward postures with increased levels of compression in order to have less overall LOS on both LT models. The method introduced was deemed a success at simulating human motion in a virtual environment from a simple, video record of the original motion.

Ergonomic and usability ratings of helmets and head-mounted personal protective equipment in industry

BACKGROUNDnAnecdotal evidence from industry suggests that those working as arborists prefer to use minimal brim style, climbing helmets rather than traditional forestry helmets. In the mining industry, workers prefer wireless, LED cap lamps. Workers cite better comfort, better ability to see their work and better ventilation as reasons to use those helmets and cap lamps. Safety personnel in the industry would like to base future helmet decisions and requirements on a complete understanding of the ergonomic and safety issues of all available head-borne equipment.nnnOBJECTIVEnPrevious research has found that helmet design, head load and head/neck posture can influence the amount of neck discomfort experienced by users. Specific features of helmets and head-mounted personal protective equipment (PPE) in various industries have been changing to reflect ergonomic design principles. A series of three studies were conducted to evaluate usability and preference of new style cap lamps and helmet brims.nnnPARTICIPANTSnPARTICIPANTS (n=10-16) were recruited primarily from undergraduate students, and each study represents a different group of novice participants.nnnMETHODSnTwo different courses that included a tunnel were used in the first two studies to evaluate cap lamp styles and wireless cap lamps, while a simulated arborist task was used in the final study to evaluate helmet brim. Measures of ergonomic and discomfort questionnaires were analysed for this paper.nnnRESULTSnThe first cap lamp study was able to conclude that LED lamps are preferred over incandescent lamps, while the second study demonstrated that users prefer a multi-directional beam, and adjustability features of the cap lamp. In the final study, participants who must perform extreme overhead tasks prefer a helmet with a minimal brim.nnnCONCLUSIONSnAdditional research is warranted to determine whether actual, industry workers demonstrate the same preferences for these PPE items.