SURFACE SENSING: fibre optic 'tape' with spatial memory
A British transducer company is preparing to market a remarkable fibre
optics based product from the USA that is able to overcome the
difficulties researchers and designers sometimes experience when
measuring irregular and awkward three-dimensional shapes
A development of the US company, Measurand, 'Shape Sensor' technology is
a novel application of fibre optics techniques that provides an extremely
simple and economic solution to demanding 3D measurement tasks.
The technology is now available in the UK from transducer and measuring
instrument specialist, RDP Electronics, which unveiled it at the Mtech'99
show and conference earlier this year. Shape technology uses fibre optic
sensors either in single or array combinations, the latter comprising
tight loops of fibres paired along a length of tape; the fibres are
specially treated to lose light proportional to bending, and as they are
bipolar, the intensity of the transmitted signal varies linearly relative
to the amount of bending.
The principle has been applied to two classes of products: Shape Sensors,
comprising two opposed loops of fibre, and Shape Tape (illustrated here),
which is a 3D sensor array with curvature sensors arranged in twist/bend
pairs. The tape knows where it is along its length and its output is
used to form a six-degree-of-freedom image on a computer. Shape Tape can
be attached in a draped shape between any two or more objects - a
person's torso and upper arm, for example - and will report the relative
six-degree-of-freedom position and orientation of the two.
The power of the system stems from its 'knowledge' of its own location in
space when not in contact with a surface. It can thus be used to track
arm segments, even though it travels in a loose, arbitrary curve over the
joints between segments. In dynamic mode, Shape Tape can be used to scan
surfaces, collecting shape profiles relative to a fixed location to build
up a surface model.
Other dynamic 3D measuring applications include impact testing,
structural testing under simulated earthquake or wind conditions,
automotive ergonomics, robot development, machine measurements and
wherever your imagination takes you!
Back to Design Office Technology April 1999
Back to Design Office Technology Archive