Picking up good vibrations

Citation

Loughlin, C. (2005), "Picking up good vibrations", Sensor Review, Vol. 25 No. 2. https://doi.org/10.1108/sr.2005.08725baa.001

Picking up good vibrations

Picking up good vibrations

Our theme for this issue of Sensor Review is “Vibration and impact sensing”. This is a tremendously useful area of technology, but one that is perhaps often overlooked by engineers – at least as far as automatic sensing is concerned.

How often is your attention first drawn to a fault in a piece of machinery because “it didn't sound quite right”. It must be one of the main curses of motor mechanics when people bring in their cars and limit their diagnostic report to “it makes a funny noise when I do such and such”.

Diagnosis of mechanical ailments by vibration analysis is nothing new, and this issue includes a paper by Wegerich (Similarity based modeling of vibration features for fault detection and identification, pp. 114–122) which shines light on the latest approaches to just this subject. However it is still in my view an under utilised area of technology. Our cars are stuffed full with sensors of various descriptions but to the best of my knowledge they do not include any for vibration analysis.

However, vibration analysis is not just about fault detection as our paper by Paradiso and Che King Leo (Tracking and characterizing knocks atop large interactive displays, pp 134–143) makes clear. Vibration also gives us a way of visualising information that is outside of the visual spectrum. Bats, whales and dolphins all use sophisticated sonic imaging technology to make their way in the world, and we can do the same if we develop the appropriate technologies.

Vibration sensing can be both active and passive. Passive includes cases such as vibration analysis for detecting faults in machinery. The machinery is the source of the vibration and the sensors just need to listen and interpret the results. Active sensing also involves the targeted application of a source of vibration, such as the knock tracking in Paradiso, or our friendly dolphins ultrasonic “radar”.

Train drivers always used to tap the train's wheels and listen for the sound. Perhaps they still do, but I have not seen it. The resultant “ring”, or lack of it, would help them determine if the wheels were sound or if a crack was developing. They knew where to tap them with a hammer and how a good wheel should sound. The only drawback to this system is that it does require physical contact with the hammer, and this makes this and other similar operations rather tricky to automate.

If we could find a way of initiating strong vibrations from a distance without direct physical contact then the door would be opened for a whole range of new applications. Measuring vibrations from a distance is not a major problem as lasers, etc. can come in to play, but creating vibrations is a lot more difficult, especially if you do not want to damage or physically alter the object under test.

Any ideas?

Clive Loughlin