MTS SWIFT 40 Sensor - Manual (Page 133)

SWIFT 40 Sensors Troubleshooting 133
Spinning Application:
Vehicle Coordinate System
Outputs have unusual or
incorrect waveform shapes
to them. (Continued) A four-time-per-revolution
of tire signal is showing up
when the vehicle is driving
straight on a flat surface. Wheel force transducers often have a
modulation error with a cyclic frequency equal
to the number of beams on the transducer. The
SWIFT transducer has four beams, and will
inherently have some level of four times per
revolution modulation. This level will vary from
±0.5% to as high as ±5% of the equivalent radial
load.
For example, a 4000 N mean level vertical Fz
load (and negligible Fx loading) will result in a
±20 N to ±200 N error on the vertical Fz and Fx
channels.
The magnitude of this modulation error is based
on the geometries and stiffnesses of the
components in the assembly.
A SWIFT 40A (aluminum) on a steel rim will
have lower modulation than a SWIFT 40A
(aluminum) on a very lightweight aluminum
rim, which will have lower modulation than a
SWIFT 40T (titanium) on the same lightweight
aluminum rim. The trade-offs between lower
added mass, load capacity requirements, and
desired modulation should all be considered in
choosing components for the wheel force
transducer assembly.
Angular Output There is no angular output
while the transducer and slip
ring are spinning. Check that all power and signal cables are
connected, and that the antirotate device is
securely attached. The angular output should be
0 to 5 V sawtooth output per revolution of the
tire.
Check that the encoder output is present. The
angle output signal from the TI should be a 0 to
5 volt sawtooth output while the transducer is
spinning at a constant velocity.
If this signal is not present, check that the slip
ring/encoder assembly has not been damaged. If
you suspect encoder damage, swap the slip ring
assembly with a known functioning unit to
verify it. If the slip ring/encoder assembly is
damaged, call MTS or replace it with a spare
slip ring assembly.
Troubleshooting Guide (part 12 of 12)
S YMPTOM P OSSIBLE C AUSES S OLUTION