FEATURE


surveillance. In most cases this health surveillance is performed by recording the time that a worker uses a device and calculating the exposure using the vibration information for the equipment used (often taken from the manufacturer). HTV measurements use an international standard (ISO 5349-1:2001) covering a frequency range between 6.3 Hz – 1250 Hz.


To best protect workers an online HTV vibration monitoring system is favourable. In this way the exposure to vibration can be correctly recorded and analysed. There are many factors that can contribute to injury; these principally being the magnitude, frequency, and duration of the vibrations, and all would need to be measured for a correct assessment of risk to the worker.


In order to provide representative data it is best to monitor vibration at the point of entry into the hand. For most hand tools this would be through the palm. This measurement is difficult using many existing methodologies as the placement of a vibration monitoring device (such as an accelerometer) on the palm would interfere with the tools use and reduce the comfort of the end user. Comfort is critical as workers in many professions will operate power tools for the majority of the working day.


The Advanced Textiles Research Group at Nottingham Trent University is exploiting its patented yarn encapsulation technology to integrate very small-scale vibration sensors into yarns. Yarns are the building block of textiles and garments and this technology can be used to create vibration sensing work gloves.


The yarn encapsulation technology sees the small-scale vibration sensor chip soldered onto fine copper wire interconnects. The chip, a carrier yarn to increase tensile strength, and the solder-joints are then encased in a small resin micro-pod. This protects the sensitive electronics from the mechanical and chemical stresses that will be encountered during garment fabrication as well as day-to-day wear of the final apparel. The entire ensemble is then


8


“IN 2015 HAVS AND CTS RESULTED IN 635


AND 260 NEW CLAIMS TO THE INDUSTRIAL


INJURIES DISABLEMENT BENEFIT SCHEME.”


surrounded with fibres and covered with a knitted fibre sheath to create a final yarn that is soft, comfortable to the end user, and where the embedded chip is undetectable.


An alternating current is measured from the embedded sensor. This signal is then Fast-Fourier Transformed (FFT) which allows for the frequency and magnitude of the vibrations to be measured. Measurements are taken over discrete time intervals, and therefore duration of exposure can be determined.


Currently research is focusing on optimising the design rules for the vibration sensing yarns as the presence of the resin micro pod and surrounding fibres will influence how vibrations travel to the embedded sensor and ultimately its response. So far results are very promising and the sensors investigated still function correctly after the encapsulation process.


To further test this concept a vibration sensing yarn was embedded within a commercially-available protective work glove. Preliminary tests have shown that the glove can provide data, while worn, for a variety of hand-held oscillatory power tools.


The final device will take the form of a knitted vibration sensing glove that can be worn inside of any style of protective work glove. Sensors can be placed anywhere on the glove’s surface allowing for the vibration sensing gloves to be tailored for use with certain power-tool types, or many sensors can be integrated to create a multipurpose glove that is suitable for use with many types of tool. Further research will investigate the best placement for sensors.


It should be highlighted that a sensor anywhere on the glove will still give useful readings, but a greater accuracy will be achieved if the sensor is at the point of contact between the tool and hand.


Beyond providing a useful health monitoring aid this type of glove offers exciting opportunities for the academic community. The ability to create a glove, that does not interfere with the user, which can measure vibration at multiple points on the hand will provide a powerful tool for HTV research.


www.ntu.ac.uk TOMORROW’S HEALTH & SAFETY YEARBOOK 2017/18


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