Occupational exposure to whole-body vibration (WBV) is a hazard linked to several adverse health effects. The most widely reported pathogenic effects of WBV exposure include the occurrence of lower back pain [1][2][3][4] although other reported effects include increased prevalence of herniated discs and neck-shoulder disorders 5) . Vibration can also adversely affect comfort and performance 6) . In order to assist in addressing the risks to health posed by occupational exposure to WBV, the European Physical Agents (Vibration) Directive (PA(V)D) 7) specifies limits on daily occupational WBV exposure. The PA(V)D mandates application of ISO 2631-1 8) as the metrological framework for measurements of daily WBV exposure severity and the application of the appropriate frequency weightings 9) .Within the context of impact on health, the methods prescribed by ISO 2631-1 (1997) stipulate evaluation of WBV within the frequency range 0.5 Hz to 80 Hz.However, the standard also states that when assessing WBV in terms of impact on health "If it has been established that the frequency range below 1 Hz is not relevant nor important, a frequency range from 1 Hz to 80 Hz can be substituted". ISO 2631-1 does not give criteria by which in one can deem WBV components below 1 Hz as 'not relevant nor important'. One interpretation of the statement could be that if there exists negligible vibration energy below 1 Hz, then there is no need to measure vibration using instrumentation capable of measuring such low frequencies as it is 'not important' (although this would mean that the instrumentation would fail to meet requirements specified in ISO 8041 10) ). Another possible interpretation could be that if the vibration is operator-induced then it is 'not relevant' to an assessment of vibration emission, as it is not caused by the machine per se, but by the driver; an example of this could be an individual driving a machine with repeated acceleration and deceleration with a short cycle time. Energy from each braking/acceleration manoeuvre would constitute part of the measured acceleration signal and, if there are a high number of such manoeuvres, these could dominate the
In engineering, combining a number of solutions and technologies can result in more effective systems than using only one approach on its own. In particular, it has been shown that in condition monitoring (CM), smarter maintenance systems may be obtained by integrating various sensors together. This paper extends this idea by integrating various non-homogeneous technologies horizontally. The proposed system is an internet-based condition monitoring (e-CM) prototype that can identify abnormal tension in moving belts. It is shown that by applying a classification technique, known as novelty detection, it is possible to decide the status of belt tension by processing the belt vibration signals from an optical sensor (i.e. an indirect sensing approach). A novel method for industrial network communication using XML to create a single standard format for sensor information is also used to link the sensor to the process controller via the internet using the flexible CAN bus technology; this is used together with low-cost microcontrollers with a built-in ethernet link for data acquisition and transmission. The resulting integrated approach is more efficient because: (a) it can reduce waste by minimizing process interruptions caused by direct belt inspection methods while obtaining high detection accuracy (99.67 per cent) and (b) it can provide on-line remote CM that is cost-effective, simple, standardized, and scalable across a wide area and for a relatively large number of sensors. This improvement is especially important when applied to bottleneck processes and critical components.
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