Thesis - Leigh Moody.pdf - Bad Request - Cranfield University

Chapter 3 / Sensors / Gyroscopes
_ _
quantisation is 400/2 11 ≈ 0.2°/s. Default values are set to compensation for
the time delay and 2 nd order dynamics.
⎛
⎜
⎝
( ) ⎟ ω ω = ⎜
GS 2DL
,
:
,
GS
NC
GS
DC
2⋅
3.4-12
GS
ζ
2DL
ω
+ ω
GS
2DL
⋅
GS
t
TD
GS
1
t
TD
⎞
⎠
Equation 3.4-21
Typical values for the gyroscope error sources used in aircraft (AC), cruise
missile (LRM), and a short-range missile (SRM) are given in Table 3-10.
For mechanical instruments the scale factor, constant and g-sensitive bias
characteristics are initialised from Gaussian distributions. Mechanical
instrument errors tend to be bi-modally distributed having passed through a
manufacturing grading process. This is reflected in the provision of bimodal
distributions defined by N(0.75σ,0.25σ) as described in §22.1.4.3.
Table 3-10 : Gyroscope Error Characteristics
Error Characteristic Alias AC LRM SRM Units
Case misalignment GSσ MA 0.1 0.3 5 mrad
Non-orthogonality GSσ NO 0.1 0.3 5 mrad
Constant bias GSσ CB 0.01 1.0 50 deg/hr
In-run bias stability 0.002 0.2 10 deg/hr
Gaussian noise (Optical) GSΦ RN 0.02 1.0 10 deg/√hr
Gaussian noise (Mechanical) GSΦ RN 0.005 0.02 3 deg/√hr
Constant scale factor error GSσ CS 20 80 300 ppm
Scale factor linearity GSσ AS 10 30 100 ppm
Maximum pulse/output GS NMP 2 24 2 20 2 16 -
Bandwidth D2L
GSω 100 Hz
Natural Frequency GSζ D2L
0.7 -
Mechanical g-dependent drift GS σ GD 0.2 0.2 - deg/hr/g
Mechanical g 2 -dependent drift GSσGG 0.003 0.003 - deg/hr/g 2
The position (∆P) and velocity (∆V) errors induced by the constant drift,
Gaussian noise and constant scale factor errors over a time period (∆t) are,
E
π ⋅ GSσ
CB
2
3
( ∆ V , ∆P
) : =
⋅ g ⋅ ( ∆t
2 , ∆t
6 )
CB
CB
180 ⋅ 3600
u
Equation 3.4-22