PRODUCT PROFILE 49
Sensors for road tests and test rigs
Micro-Epsilon discusses some of the more
challenging vehicle test applications for
non-contact displacement measurement
and draw-wire sensors
ABOVE: The ILD1420
sensor uses laser
technology to
determine ride
height as a car
travels around
a racetrack
LEFT: Micro-
Epsilon’s
thermoMeter and
capaNCDT sensors
help engineers
to monitor brake
temperature
and thickness
on a test rig
May/June 2020 • VehicleDynamicsInternational.com
monitor the ride height of cars as they
travel around a track.
Draw-wire sensors are used in road
tests, crash tests and simulators, where
they must meet the highest requirements
in terms of wire accelerations, vibrations,
shocks and limited installation space.
For example, with a measuring range of
40mm and cable acceleration of up to
60g, the wireSensor MT19 is suitable for
applications that require high dynamics,
such as crash test dummies, simulators
and impact test rigs.
In spring travel measurements, MPM
draw-wire displacement sensors from
Micro-Epsilon are mounted in parallel to
the shock absorber, to record the data
under various road conditions. Based
on the displacement signal obtained,
vibration velocity and vibration
acceleration can be calculated. In crash
tests, multiple MPM draw-wire sensors
measure the effects of an impact on the
vehicle body and passengers. Their high
wire acceleration enables the sensors to
measure the movement of the object.
In order to optimise the braking
behaviour and pedal travel, the F50
››As the development of nextgeneration
vehicles continues
apace, OEMs increasingly need to
understand the movement and behaviour
of components and structures as part
of NVH testing, and it is important that
the instrumentation used doesn’t itself
affect the NVH results.
Micro-Epsilon has been developing
contact and non-contact displacement
sensors for vehicle test applications
for almost 50 years. These sensors are
used in R&D, test cells and production,
and for on-vehicle testing in almost
every conceivable area of a vehicle.
Applications include laser sensors for
vehicle ride height, draw-wire (string
pot) sensors for measuring suspension
spring/damper movements and pedal
travel; capacitive sensors for measuring
brake disc deformation; and non-contact
temperature sensors and thermal
imaging cameras for measuring the
temperature of on-vehicle components.
“In automotive and motorsport
applications, measuring vehicle ride
height is critical. As speeds increase, the
stability of the car and the aerodynamics
employed must be carefully monitored
to ensure the car stays on the ground,”
explains Glenn Wedgbrow, business
development manager at Micro-Epsilon.
Non-contact laser displacement
sensors have been developed to
withstand the shock and vibration of
being mounted to a vehicle. The laser
window points down towards the ground
or race track, and the ILD1420 sensor
series has been used extensively across
all motorsport classes to measure and
draw-wire sensors offer a rotatable
potentiometer, which enables the user
to select the measuring range within
the entire extraction length (150mm).
The integrated deflection pulley allows
the sensor to be flexibly integrated in
a footwell or engine compartment.
Non-contact capacitive displacement
sensors are also used to obtain accurate
data on the deformation of brake
discs under stress. With high surface
temperatures up to 600°C and typical
deformations of less than 100μm, the
high-resolution capaNCDT non-contact
capacitive displacement measurement
system from Micro-Epsilon measures
the deformation of the brake disc under
loading conditions. The system also
offers high bandwidth for frequency
analysis up to the 10th harmonic, as
well as high-accuracy minimum zeroshift
with changes in temperature.
In order to move the measurements
from the dynamometer onto the vehicle,
the capaNCDT DTV system is available
for measuring variation in brake disc
thickness. The included software allows
engineers to take surface runout and
thickness variation measurements in-situ
before and after each test run without
dismounting the wheel – a process which
would normally influence the results. In
addition, a custom four-channel sensor
enables simultaneous measurement of
a full vehicle braking cycle, with four
tracks on each side of the brake disc.
The single-point IR temperature
sensors and thermal cameras from the
thermoMeter and thermoImager range
help vehicle development in terms of
brake temperature testing and tyre
performance. In Formula Student, for
example, the thermometer CT range is
used by many universities to monitor
brake disc temperature during onroad
testing, whereas in Formula 1 the
thermoImager series of compact thermal
imaging cameras has been used to allow
recording and monitoring of IR video
in real-time, with the data used to
determine the effects of the car setup
and its influence on tyre temperature
and operating condition.
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