Mining Project: Investigation of Simple Cost Effective Whole-Body Vibration Measure Tools: Capabilities, Vibration Measures, & Expansion
To assess the accuracy of the whole-body vibration app and determine if its capabilities can be expanded to include seat transmissibility.
Exposure to whole-body vibration (WBV) negatively impacts the health and safety of exposed mine workers. Off-road mining equipment operates on rough surfaces under harsh operating conditions that produce WBV and mechanical shock. Vibration is often complex, contains many frequencies, occurs in several directions, and changes over time. WBV exposure can cause muscles to contract in a voluntary or involuntary way and lead to fatigue or a lowering of motor performance capacity. Research points to WBV as a contributing factor in the development of musculoskeletal disorders (MSDs) of the spine among workers exposed to a vibration environment.
A need exists to prevent vibration-induced injuries through improved awareness of vibration exposure. Operators of large, off-road, mobile mining equipment and vehicles are exposed to WBV on a routine basis. There is growing awareness in the mining community of the issues surrounding WBV exposures to mining equipment operators. However, mining companies do not have a simple and low-cost means for assessing the WBV exposures of operators on off-road mining vehicles and equipment. Moreover, there is not a simple, low-cost, yet effective way for mine managers to recognize when a vehicle seat may need to be repaired, replaced, or adjusted due to its poor vibration attenuation. This is important in that an off-road heavy vehicle seat can range from $400 to $3,000 or more, depending on its design and features. Presently, WBV measurement systems are somewhat complex, involving a recording device with other accessory instruments, such as accelerometers that must be used together with the recording device, at a cost from $5,000 to $50,000 or more.
Personal electronic devices (e.g., iPhones and iPods) pervade our world today. These devices typically are equipped with sensors that have different measurement capabilities including vibration. Until recently, the only methods to measure WBV required costly measurement systems as well as technical expertise to analyze the data. Researchers at the University of Queensland (UQ) have developed the WBV app to provide a straightforward and economical method to estimate WBV. The application collects accelerometer data and calculates frequency-weighted estimates of WBV exposure according to the methods described in international and national standards. The iPod app has been tested for use on a 5th generation iPod Touch running an iOS7 operating system. The results of field studies examining the WBV app have been favorable. Key findings of studies by the Australian researchers, Burgess-Limerick and Lynas, have indicated that the average variance between a Svantek SV 106 (reference system) and the iPod app was 0.033 m/s2. Moreover, the average constant error for the iPod measurements was 0.013 m/s2 with a standard deviation of constant error at 0.039 m/s2. Furthermore, the researchers concluded that using the WBV app installed on an iPod Touch provided a 95% confidence level of ± 0.07 m/s2 for the vertical direction.
This pilot research project has addressed the need for a single, low-cost device by evaluating the use and accuracy of a commercially available mobile app and its utility for quantifying seat vibration isolation performance. The WBV app has the potential for providing mining companies with a simple tool to collect exposure data and assess injury risk, as well as to evaluate seat performance relative to vibration isolation. While previous research has shown favorable performance of the WBV app for quantifying WBV exposure, its ability to evaluate seat performance on the basis of vibration isolation has not been evaluated. Thus, the goal of this research study was to determine if the WBV app could be used to determine seat performance by quantifying vibration transmitted through the vehicle to the vehicle driver or machinery operator on mobile mining equipment.
The project objective was successfully met through the completion of two research aims, summarized as follows:
Research Aim 1. Conduct field evaluations to determine the accuracy of WBV App on an iPod Touch device as compared to the Siemens/LMS SCADAS data recording system.
Research Aim 2. To conduct a field evaluation using two iPod Touch devices running the WBV App to quantify seat transmissibility.
The results of this study show that utilizing the iPod Touch with the WBV app can serve as a low-cost, simple tool to estimate operator whole-body vibration exposures on mobile mining equipment. Findings for Seat Effective Amplitude Transmissibility (SEAT) values, which describe seat performance, exhibited increased variability for the iPod pair and reference systems as noted by the frequency-weighted, root-mean-square acceleration and vibration dose value computational methods. However, these metrics still demonstrated a high positive correlation between the two systems.
The findings of this study show that the WBV app is capable of assessing seat performance relative to SEAT value when installed on two iPod Touch devices. Moreover, data collected with the WBV app can be stored by mine operators to provide short-term and long-term monitoring information for heavy mobile equipment. The data can be cross-referenced with subjective feedback from equipment operators for closer scrutiny of the equipment to determine whether it is being operated properly or if the conditions of the equipment or even the roadways are creating issues. When two iPod Touch devices are used together, the results can then be used to inform mine managers of the condition of the vehicle seat and whether it needs to be adjusted, repaired, or replaced. Proper maintenance of mobile equipment and operator seats can help lower injury risk of low-back pain and other back- and neck-related injuries for the equipment operators.
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