Gyro Compass (MIDTERM AND FINALS) Flashcards
a non magnetic compass in which the direction of true north is maintained by a continuously driven gyroscope whose axis is parallel to the earth’s axis of rotation
gyro compass
consists of a spinning wheel or rotor contained within gimbals which permit movement about three mutually perpendicular axes, known as the horizontal axis, the vertical axis, and the spin axis
gyroscope
two basic properties of gyroscopes
Rigidity and Precession
The axis of rotation (spin axis) of the gyro wheel tends to remain in a fixed direction in space if no force is applied to it.(gyroscopic inertia)
RIGIDITY
depends on the angular velocity, mass, and radius of the wheel or rotor
Gyroscopic inertia
The axis of rotation has a tendency to turn at a right angle to the direction of an applied force
PRECESSION
the rate of precession is proportional to the
applied torque
a change in the orientation of the rotational axis of a rotating body
PRECISSION
This phenomenon is found only in spinning bodies. It is the movement of the spin axis when a force is applied to the spin axis of gyroscope. When a couple is applied about its horizontal axis, the spin axis will turn at right angles to the applied force in the direction of the spin of the wheel. Similarly couple applied about the vertical axis will make the spin axis turn about the horizontal axis in the direction of the spin axis of the wheel
PRECESSION
If the applied torque has a component which is perpendicular to the initial angular momentum the gyroscope will
PRECESS
is a measure of how much a force acting on an object causes that object to rotate
Torque
three vectors
torque, spin, and precession
are all oriented with respect to each other according to the right-hand rule
three vectors, (torque, spin, and precession)
It has 3 degrees of freedom:
- It is free to spin about spinning axis
- It is free to rotate about vertical axis
- It is free to rotate about horizontal axis
The motion of the spin axis in the horizontal plane is known as
drift
The movement of spin axis in the direction of Azimuth is
drift
The rate of change of drift is
drifting
The motion of spin axis in the vertical plane is known as
tilt
The angle of elevation or depression of the spin axis above or below the horizontal is
tilt
The rate of change of tilt is
tilting
The gyrocompass depends upon four natural phenomena:
gyroscopic inertia, precession, earth’s rotation, and gravity
To make a gyroscope into a gyro compass, the wheel or rotor is mounted in a sphere, called the _, and the sphere is then supported in a _
gyro sphere, vertical ring
The whole is mounted on a base called the
phantom
The rotor may weigh as little as half a kilogram to
over 25 kg
To make the gyro seek north, a system of reservoirs filled with mercury, known as _, is used to apply a force against the spin axis
mercury ballistics
used to apply a force against the spin axis
mercury ballistics
usually four in number, are placed so that their centers of gravity exactly coincide with the CG of the gyroscope
ballistics
then causes the spin axis to trace an ellipse, one ellipse taking about 84 minutes to complete
Precession
To make it seek and maintain true north, three things are necessary.
First, the gyro must be made to stay on the plane of the meridian.
*Second, it must be made to remain horizontal.
*Third, it must stay in this position once it reaches it regardless of what the vessel on which it is mounted does or where it goes on the earth
one ellipse taking about _ to complete
84 minutes
two methods of damping:
Damping in tilt and Damping in azimuth
In this method a force is applied in the horizontal plane (a torque to the vertical axis) which results in a precession in the vertical plane, reducing the
Damping in tilt
In this method a precession is developed which assists the movement in the azimuth plane when the axis moves towards the meridian, and opposes the movement when the spin axis moves away from the meridian
Damping in azimuth
means that when the North-seeking end of the gyroscope axis is - a damping torque is applied in a horizontal plane in such a direction that the resultant precession in a vertical plane causes the - of the axis to decrease
Damping in tilt
The amplitude of each oscillation is reduced to _ and thereby resulting in the axis finally setting down in the meridian
1/3 of the previous oscillation
is achieved by introducing a torque in a vertical plane, which causes a precession opposite to the gravity control precession but out of phase with it, i.e, with a time delay.
Damping in azimuth
The _ causes the axis to overshoot the meridian less each time it crosses it until the gyroscope axis reaches its setting position
resultant precession in a horizontal plane
is a very important and unique tool in marine navigation as it does not operate automatically like other magnetic compasses
Fluxgate compass
is an electromagnetic compass which solves the purpose of a conventional compass
fluxgate compass
is a device that helps to correctly pinpoint the geographical direction while on a sea going vessel
compass
is a very important and unique tool in marine navigation as it does not operate automatically like other magnetic compasses
fluxgate compass
is an electromagnetic compass which solves the purpose of a conventional compass
fluxgate compass
is used in ships mainly for the purpose of steering.
fluxgate compass
the compass is an electronic one, the scope of errors is greatly reduced. In addition to manual steering, such a compass can also be utilised when the ship is on autopilot. Even chart plotters and radars use this system to provide them with accurate geographic indications
fluxgate compass
there are no pointers that specify the direction
electronic compass
There are two coils of wire that are located perpendicular to each other around a permeable magnetic material. When electric current is passed through the coils the core material works an electromagnet and senses the direction of the horizontal component of the earth’s magnetic field. This completely eradicates the problem caused due to the interference of the magnetic north is completely avoided
electronic compass
Another advantage of installing this type of compass in the ship is that these types of compasses are unaffected by their placement on the ship.
electronic compass
They can be placed anywhere and the directions pointed by the compass can be relied on completely.
electronic compass
can prove very useful during rough seas as they are unaffected by position and unusual movements
Fluxgate compass
is one of the best navigating technologies that are available in the marine industry
fluxgate compass
which detects and transmits the ship’s Compass Heading over a digital connection to one or more CompassHeading Repeaters at any convenient location on a vessel.
Transmitting Magnetic Compass (TMC) System
provides a complete alternative (or a backup) to a gyro compass as a source of Heading.Magnetic Variation andDeviation can be corrected using theMarine Data to give True Heading.
TMC system
can provide a source of Heading for Compass Repeaters and other navigation equipment.
TMC
refers to electronic components, devices, and systems based entirely on the semiconductor
Solid-state
The expression was especially prevalent in the late 1950s and early 1960s, during the transition from vacuum tube technology to the semiconductor diode and transistor
Solid-state
