Inertial Navigation Flashcards
What is the primary function of an Inertial Navigation System (INS)?
Provide continuous latitude and longitude positional information.
List three advantages of using an INS.
- Self-contained
- Not affected by weather or aircraft orientation
- Very accurate
Identify the outputs at A, B, C, D in an INS.
A: distance
B: present position
C: distance to destination
D: component of groundspeed
What are the typical inputs provided by an INS?
- Start position
- Destination position
- Power supplies
What are the typical outputs provided by an INS?
- Present position
- True heading
- True track
- Groundspeed
- Height
- Vertical velocity
- Attitude
List three advantages of using a Strapdown INS over a conventional INS.
- More reliable
- Quicker alignment
- Lower cost
What type of accelerometer is used in an INS?
Force feedback or Pendulous force balance
What is a problem with early ‘Ring Laser Gyros (RLG)’ and how is it resolved?
The problem is ‘lock in’; it is resolved by dithering or vibrating the ring laser cavity using a ‘dither motor’.
Explain the operation of a Ring Laser Gyro.
They measure angular rates of rotation by sensing the difference in time taken for two beams of Laser light, travelling in opposite directions, to travel around a closed path.
List the four stages of the Strapdown INS Normal alignment sequence.
- Power up and BIT
- Present Position insertion
- Level detection
- Gyrocompassing
Explain the two methods of updating INS.
- Position fixing: when the aircraft flies over a known point and updates the INS output with the latitude and longitude of a fixed position.
- Position error compensation: uses a recursive software called a Kalman filter which carries out statistical analysis to predict future errors from the INS.
Why does a Strapdown INS require Gravity Correction?
Gravity correction is required to counteract the effects of local gravity on all accelerometers.
Describe Kalman Filtering.
The Kalman Filter carries out statistical analysis of information from the INS and other Navigation sensors and provides estimates of future INS errors.
