A High-Rate Virtual Instrument of Marine Vehicle Motions for by Chrystel Gelin

By Chrystel Gelin

Dead-Reckoning aided with Doppler pace size has been the commonest procedure for underwater navigation for small autos. regrettably DR calls for common place recalibrations and underwater motor vehicle navigation structures are restricted to periodic place replace after they floor. eventually common worldwide Positioning process (GPS) receivers are not able to supply the speed or precision required while used on a small vessel. to beat this, a most economical excessive fee movement dimension approach for an Unmanned floor car (USV) with underwater and oceanographic reasons is proposed. The proposed onboard approach for the USV contains an Inertial dimension Unit (IMU) with accelerometers and fee gyros, a GPS receiver, a flux-gate compass, a roll and tilt sensor and an ADCP. Interfacing all of the sensors proved relatively not easy as a result of their diverse features. The proposed info fusion procedure integrates the sensors and develops an embeddable software program package deal, utilizing actual time facts fusion tools, for a USV to assist in navigation and keep watch over in addition to controlling an onboard Acoustic Doppler present Profiler (ADCP). whereas ADCPs non-intrusively degree water move, the vessel movement should be got rid of to research the information and the process constructed presents the movement measurements and processing to complete this activity.

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E. for frequencies lower than the cutoff frequency the position estimate is provided by the GPS, while for frequencies above the cutoff frequency the measure of position is derived from the merged velocity signal. The experiments take place in an open parking lot to ensure the GPS system has a clear and unimpeded signal. The experimental setup consists in mounting the IMU, the tilt sensor and the compass on a rigid plate that is fixed to a cart (Figure 42) where the rest of the data acquisition system (without the ADCP) is mounted.

This was done using an accelerometer to measure acceleration along its axis of sensitivity and at frequencies where the translational acceleration of the IMU is negligible so that the accelerometers only measure gravity. Thus, at low frequencies, with little translational motion, the accelerometers can provide an independent measure of the Euler angles, (Figure 23), (Lueck, Nahon 2000): sin , , (20) and , cos sin (21) 28 3 Data Processing Fig. 23 Acceleration measurements in function of the rotation angles To compare the angular measurements of the tilt sensor with these of the accelerometer, the IMU and tilt sensor were mounted on the same rigid plate and very slowly rotated through the expected tilt range.

0. 66% and delayed by 11 samples. 38% with no delay. The compass is a digital serial device that is first processed and coded into RS-232 format at the compass, broadcast, then received and processed by the data acquisition computer. Any delay is due to the lag associated with this overhead and should be accounted for within the motion correction of the ADCP although in our case an agreement of more than 99% is considered acceptable. 32 3 Data Processing Phi [deg] To validate the high frequency component of (Figure 25), the Euler rates are integrated and compared to the Euler angles, , yield through the data fusion (Figure 27).

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