EE 495 Modern Navigation Systems Aided INS Monday, April 07 EE 495 Modern Navigation Systems Slide 1 of 10

Aided INS Notation Monday, April 07 EE 495 Modern Navigation Systems Recall the notation  True Value of the vector:  Measured value of the vector:  Estimated value of the vector:  Error in the vector: o Truth – estimate Slide 2 of 10

Aided INS Notation Monday, April 07 EE 495 Modern Navigation Systems Recall the notation  Accelerometer Measurements:  If we estimate all but the bias instability & additive noise  and = Estimate of errors in the measurement - True errors in the measurement = Estimate of errors in the measurement - True errors in the measurement Continuous time model Slide 3 of 10

Aided INS Notation Monday, April 07 EE 495 Modern Navigation Systems  Gyro Measurements  If we model all but the bias instability & additive noise  and = Estimate of errors in the measurement - True errors in the measurement = Estimate of errors in the measurement - True errors in the measurement Continuous time model Slide 4 of 10

Aided INS Monday, April 07 EE 495 Modern Navigation Systems Recalling the ECEF Error Mechanization Augmenting the above yields Slide 5 of 10

Aided INS Monday, April 07 EE 495 Modern Navigation Systems Rewriting  Discretizing the above yields  where and Slide 6 of 10

Aided INS Monday, April 07 EE 495 Modern Navigation Systems  The measurement equation is  where Slide 7 of 10

Aided INS Monday, April 07 EE 495 Modern Navigation Systems The need for integration SYSTEMSTRENGTHWEAKNESS INS  High-bandwidth  Good short-term accuracy (PVA)  Unaffected by RF jamming  Initialization required  Suffers from drift errors (unbounded errors)  High-cost  Requires a high-fidelity gravity model GPS  Good long-term position & velocity accuracy (bounded errors)  Not sensitive to gravity  Relatively low-cost  Low-bandwidth system  Difficult to obtain attitude  Susceptible to satellite signal blockage/jamming INS + GPS  High-bandwidth system  Good short and long-term accuracy (PVA)  Can perform during GPS loss  INS can aid GPS receiver (& vice-versa)  Robust system  Greater complexity Slide 8 of 10

Aided INS Monday, April 07 EE 495 Modern Navigation Systems Integration Architecture to Date  Loosely Coupled Open-Loop Integration Problems as the INS error grows “large” Linearization approximations fail Slide 9 of 10

Aided INS Monday, April 07 EE 495 Modern Navigation Systems Same error-domain approach to integration can be employed for  Compass (orientation aiding) o Attitude and heading reference system (AHRS)  Odometery (position aiding)  Star Tracker (orientation aiding)  Altimeter … Slide 10 of 10