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

Chapter 3 / Sensors / Accelerometers
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model is implemented so that errors are superimposed on the specific
accelerations from which velocity increments are derived.
1
GUI
F_BRU
FX_URU
FY_URU
PENDULUM ANGLE
FZ_URU
ACCELEROMETER
INPUT
3.5.3 Reference Specific Acceleration
3.5-2
ROLL ACCELEROMETER
I_FX_BRU
FX_URU I_VX_INC
ROLL ANGLE
PITCH ACCELEROMETER
I_FY_BRU
FY_URU I_VY_INC
PITCH ANGLE
YAW ACCELEROMETER
I_FZ_BRU
FZ_URU I_VZ_INC
YAW ANGLE
Figure 3-32 : Accelerometer Triad Model
The average specific acceleration along Missile Body axes is processed at
the reference rate (ACfR) of 800 Hz. The acceleration acting along each
input axis depends on the alignment and orthogonality of the case with
respect to the missile body, and each sensor relative to the case as shown in
Figure 3-33.
F_BRU
1
CASE
MISALIGNMENT
NON
ORTHOGONALITY
PENDULUM
ANGLE
2
CROSS
COUPLING
1
2
3
4
5
6
FX_URU
1
FY_URU
2
FZ_URU
Figure 3-33 : Accelerometer Input Model
Mechanical instruments are also subject to cross-coupling errors that depend
on the pendulum angle that require similar RPY sensor axes defined for
gyroscopes in §3.4.3. These additional error sources are invoked by setting
the MS_GS_ER bits 11-13 listed in Table 3-11.
Table 3-11 : Accelerometer Reference Errors
MS_AC_ER Sensor Error Source
11 IMU case misalignment
12 Non-orthogonality wrt case
13 Cross coupling error
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