Sperry Marine NAVIKNOT 600 SE, Руководство по эксплуатации, установке и обслуживанию

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NAVIKNOT 600 SE 056349/C
Operating Principle 1-3
1.2 Operating Principle
To determine the longitudinal and transverse ground speeds, the sys-
tem makes use of a self-contained satellite sensing system, consisting of
the satellite PCB with two GPS receivers inside the electronics unit and
the antenna unit connected to it.
The satellite PCB combines the data from the GPS receivers with data
from built-in rate gyros to determine the vessel’s heading, velocity,
course, and attitude. While the heading is referenced to the vessel’s
fore-and-aft line, the velocity and course represent the vessel’s motion
vector, i.e. the magnitude and direction of its motion over ground.
The sensed data are sent to the processing PCB inside the electronics
unit, which resolves the velocity data into the vessel-referenced longitu-
dinal and transverse ground speeds.
The speed vectors combined with the sensed rate of turn data are used
to discern between translational and rotational movements of the ves-
sel. These are used to determine the bow and stern transverse speeds
shown on the “docking display” page.
To determine the longitudinal water speed, the system utilizes the elec-
tromagnetic principle.
The EM sensor generates a magnetic field around itself when an AC cur-
rent is applied to its excitation coil. The ship’s motion through the water
gives rise to an electrical field (E) perpendicular to the magnetic field (B)
and the ship’s motion (V). The resulting signal is picked up by the sensor
electrodes and passed on to the preamplifier. The preamplifier converts
the sensed (“raw”) speed to a digital format (NAVIKNOT protocol) and
transmits it to the electronics unit.
Figure 1-2:
sensed and calculated
speeds and directions
The electronics unit transmits all speed data to receiving external equip-
ment and to the connected CDUs. From the longitudinal ground and
water speeds, the electronics unit also calculates the distances travelled
and maintains the total and daily mile counters for both the ground and
water distances.
vessel's mot i on ve c tor
over ground ( c ourse a nd
velo ci ty; sensed)
long i tud i n a l ground speed
( ca l c ul a ted)
long i tud i n a l w a ter speed
(sensed)
he a d i ng (sensed)
tr a nsverse ground speed
( ca l c ul a ted)
B
E
V