Using Virtual Instrumentation to Measure Human Vibrations

Author(s):
Pietro Moschioni - Studiogamma

Industry:
Automotive

Products:
LabVIEW, USB-9233

The Challenge:
Developing a cost-effective system for measuring human vibrations that is free of legacy equipment limitations.

The Solution:
Using NI software and hardware to develop the hand-arm, whole-body vibration kit (Hawk).

Exposure to vibration is becoming a fundamental issue in the evaluation of workers’ health risks and comfort levels. New standards and national laws have raised the priority of evaluating and measuring the vibrations workers experience. The growing concern over this issue has also drawn the attention of vehicle manufacturers when considering the comfort of their passengers.

The vibrations a human body can tolerate consist of whole-body vibrations, both when standing and seated, and hand-arm-system vibrations, for example, those produced by a handheld tool, such as a drill.

According to ISO standards, vibration measurements should be taken along three axes by means of a triaxial accelerometer. Acceleration signals must be frequency-weighted with proper standardized filters that represent the transfer functions of the body or its parts. Finally, the acceleration signals are combined and rectified to obtain a variety of parameters that must be compared to limits imposed by national laws.

Currently, the instrumentation available for this testing is either a low-cost or a high-cost system. Low-cost systems typically perform poorly and offer limited analysis capabilities. These systems are intended for simple in-field investigations, such as a peer-to-peer worker exposure control. High-cost systems, on the other hand, perform well and provide sophisticated analysis tools and transducer conditioning options, but they are expensive.

 The Hawk System

Studiogamma and Spectra developed a revolutionary system for the measurement of human vibrations called Hawk. The system is composed of a data acquisition and real-time analysis software package, as well as a powerful data post-processor that we implemented in the NI LabVIEW graphical programming environment. Hawk also offers an innovative package of proprietary analysis tools using the portable NI USB-9233 data acquisition (DAQ) module and a bundle of accelerometers and adapters.

Hawk was developed to overcome the performance and economic limitations of legacy systems. The system performs all basic functions in real time (frequency weighting and all types of averaging activities required as standard value), as well as the most advanced analyses (1/3 octave, fast Fourier transform, or FFT) with user-defined frequency resolution from 0.5 to 16 Hz, range 0.5/2000 Hz). The system is also issued as “full optional,” with no further costs or after-market add-ons.

Because the system is PC-based and generally portable, memory space is not an issue. Furthermore, operators do not need to download data from the instrument to a memory card while taking measurements because standard instrumentation handles this operation.

Data, stored on the PC hard disk, can be analyzed offline. Users can easily complete complex operations such as full recalculations of all parameters, extraction of time history portions, and suppression of spurious data in records They can also perform joint time-frequency analysis and offline frequency weighting. Due to an innovative proprietary algorithm, users can recalculate all time-constant-based quantities offline. This makes Hawk the most powerful system in offline processing.

Because the system is PC-based, it is extremely user-friendly. According to the classic approach of Studiogamma, the data acquisition program, which can be used in hostile conditions, is a one-button-software so the operators can safely and easily use it with just one click.

Thanks to the virtual instrumentation approach, all the advantages of low-cost instrumentation (portability, ease of use, synthetic indication) are combined in Hawk with the power of high-level systems (powerful analysis capabilities and overall performance). With a quality comparable to top-level signal analyzers, the system can also rely on the powerful, 4-channel USB-9233 data acquisition module featuring antialiasing filters, IEPE conditioning, and a 24-bit ADC. With these components, Hawk meets the requirements of most operators, including users in the field and researchers. It also offers a software package at a price lower than even the low-cost systems. With Hawk, users can also reuse the same data acquisition hardware for sound-analysis purposes.

Author Information:
For more information on this Case Study, contact:
Pietro Moschioni
Studiogamma
22100 Como
La MasiaIT
Tel: +39 (0)31 57.40.10
Fax: +39 (0)31 57.12.25
info@studiogamma.org

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