An alternative approach to whole-body vibration measurement Rantaharju T., University of Oulu, Measurement and Sensor Laboratory, Kajaani Ruotsalainen K., University of Oulu, Centre for Wireless Communications, Vuokatti Romppainen P. & Partanen A., Kajaani University of Applied Sciences Whole-body vibration (WBV) refers to vibration that is transmitted through supporting surfaces to the human body. Many occupational groups, such as operators of heavy machinery, are exposed to WBV during their daily working routines. Long-term WBV exposure is associated with health symptoms, such as low back pain [1]. WBV also causes discomfort and disturbs task performance. The prevention of health risks has been taken into account in the European Parliament directive 2002/44/EC [2]. The amount of vibration, expressed as the frequency weighted root mean square (RMS) value of acceleration, should not exceed certain limits during any 8-hour working day. The measurement methods are defined in the ISO standard [3]. According to the standard, vibration shall be measured at the human-seat interface using a triaxial accelerometer mounted in a semi-rigid disc. Basis for the new approach The long-term measurement of WBV is not required by the directive, even if the health effects arise in the long-run. In addition, the standardized measurement method is quite uncomfortable for the operator. Kajaani University of Applied Sciences, The Measurement and Sensor Laboratory of Oulu University (MILA) and The Centre for Wireless Communications (CWC) of Oulu University have adopted an alternative approach to the WBV measurement. The goal is the development of a comprehensive solution for the long-term measurement. Alternative sensor solutions Alternative sensor configurations, better suited for the continuous monitoring of the WBV exposure of the operator, have been studied and tested. Promising results have been obtained when burying accelerometers in the seat pad at the region of the ischial tuberosities (figure 2). When compared with the standard method, there were only minor differences in the RMS values of the alternative method [4]. The wireless measurement system The wireless measurement system is modular and conforms to the requirements defined in the directive 2002/44/EC. The main use of the system is the continuous measurement in a machinery environment. The architecture of the system is represented in figure 1. Description of the system The measurement card acts as the main module of the system. It establishes a body sensor network by the Zigbee interface. The body sensor network is used for data acquisition from the wireless sensors. Additionally, the measurement card is able to calculate frequency weighted RMS values of the acquired acceleration data. In the machinery environment, this information can be transferred to the vehicle information system by the CAN interface. This information can also be transferred to a PC or a mobile phone using the WLAN interface. The mobile phone buffers and then transmits the data to a remote server using the GPRS/3G or any other possible connection. Figure 1. Architecture of the wireless measurement system for WBV. Figure 2. Standard and alternative methods. Benefits of the new approach Long-term, individualized WBV measurement will enable the detection of harmful working periods. Data can be used by employers, machine manufacturers and researchers to improve working conditions and study WBV as a whole. Introduction Figure 3. 6DOF motion base (Moog Inc.). References [1] Bovenzi M. et al. (1999) Int Arch Occup Environ Health 72, s [2] Directive 2002/44/EC of the European Parliament and of the Council [3] ISO :1997 Mechanical vibration and shock [4] Rantaharju T. (2009) Vaihtoehtoinen kiihtyvyysanturointi kehotärinän jatkuva-aikaiseen mittaamiseen Vibration simulation laboratory A repeatable and reliable vibration stimulus can be provided by a 6DOF motion system also being able to replicate vibration measured from machinery (figure 3).