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IMU User Guide revision 3.1 SMC Ship Motion Control www.shipmotion.eu
5
MOTION SENSOR OPERATION
5.1
SETTLING TIME
The SMC IMU internal filtering system uses both past and present data to calculate the output.
Hence, immediately after being connected to its power source, the sensor will produce less accurate
measurements since there are only short sequences of historical data available for processing.
The SMC IMU has a settling time of approximately 1 minute, from the motion sensor startup it will
take 1 minute till output data is shown. During this settling time, the sensor output dependent on
protocol selected could read for example $PSMCS,+rr.rr,+pp.pp,+hh.hh
5.2
HEAVE OPERATION
SMC IMU-008, IMU-106 and IMU-108 uses a heave measurement and filter system that continually
monitors the motions and reviews the previous motions to maintain accurate results whatever the
vessel size and sea state. Heave is not available in the IMU-007 and IMU-107 motion sensor.
Heave Zero Point, the zero point is set by the spectral analysis of the sinusoidal waveform along with
using filtering techniques that can track the zero point of the heave motions within a maximum of 5
cycles. There is no need to input data of vessel type and sea states expected.
Heave Period; The SMC IMU technology enables the measurement of heave cycles with different
periods without any manual setup. The IMU-008, IMU-106 and IMU-108 units adjust their
calculations after the current motion and sea state and heave period.