Ergonomics - Atlas Copco

Vibration
All machines vibrate to some extent.
Depending on the design, the vibration
can cause malfunction, fatigue and
breakage of the tool. When operators are
exposed, vibration can also cause health
problems. In power tools the magnitude
of vibration is determined by oscillating
forces acting on the machine mass, the
excitation of the natural frequencies of
machine parts, and vibration from the
process itself.
What is vibration?
Vibration is the oscillating motion of an
object caused by forces acting on that object,
which may be a power tool. Although this
back and forth motion, or displacement, can
be oriented along one axis, in most cases
it has a more complex pattern. To describe
the motion you often need three axes and
sometimes rotational axes as well, allowing
description of movement in a number of
different directions.
If the frequency of the oscillating force
coincides with the natural frequency of a
component in the tool design, the displace-
ment will be amplified. Machine parts such
as handles, for example, can be considered
as a mass spring system with their own
natural frequencies.
How do we measure vibration?
Vibration can be described in many different
ways. The most common method is to use
acceleration as the parameter. By integrating
the acceleration signal once, the motion is
described as velocity. Integrating the velocity
gives a description of the displacement.
Acceleration is a rather abstract param-
eter to be used to describe a motion. There
are, however, a number of reasons why it has
become the most widely used method.
The most common transducer is a
piezo-electric accelerometer, which has a
mass pre-loaded by a spring against a
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