55 INS Flashcards
INS def
An INS is a navigation aid that uses a computer and motion sensors (accelerometers) to continuously calculate via dead reckoning the position, orientation, and velocity (direction and speed of movement) of a moving object without the need for external references
Advantages of INS 6
- Self contained
- Does not radiate
- Unjammable
- Allweather operation
- Worldwide operation
- By its true nature, INS provides relatively accurate position and very accurate attitude information
Generic INS Components 4
- Accelerometers
- Computers (calculate data from accelerometer)
- Stable Platform
- CDU
Newton 1st law of motion
Law of inertia
A body at rest or, if already in motion, remains in uniform motion with constant speed in a straight line, unless it is acted on by an unbalanced external force
2nd law of motion
Mass is constant in any static system
Therefore a specific acceleration will result from a specific force
Must measure F to find a
The force applied to the mass is proportional to the resultant acceleration
F=ma
Mechanical INS
the original INS was a mechanical system mounted on a free moving stable platform
A stable platform uses gimbals and mechanical gyroscopes to maintain a level reference about 3 orthogonal axes for the accelerometers to sense movement
Strapdown INS
Modern INS are strapdown systems, the accelerometers and gyroscopes are mounted directly on the aircraft frame
Inputs from gyroscopes help create a computer generated transformation matrix (Quaternion or simulated stable platform) to replace the stable platform and provide a level reference for the accelerometers.
Mechanical gyroscopes have been replaced with ring laser gyroscopes.
Desired characteristics of accelerometers
1 low threshold of sensitivity
2 wide range of sensitivity
3 linear output
4 high resolution
Earth rate
15.04º/hr
