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

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Chapter 3 / Sensors / Accelerometers<br />

_ _<br />

400<br />

~<br />

f<br />

B<br />

r, u<br />

: =<br />

400<br />

1<br />

2<br />

⎛<br />

⋅ ⎜<br />

⎝<br />

V ~<br />

∆<br />

B<br />

r,<br />

u<br />

800<br />

3.5-10<br />

~<br />

f<br />

: =<br />

B<br />

r, u<br />

+<br />

400<br />

~<br />

f<br />

800<br />

~<br />

f<br />

B<br />

r, u<br />

B<br />

r, u<br />

⎛<br />

⎜ t −<br />

⎝<br />

For convenience the accelerometer outputs are collected together,<br />

3.5.5 Sensor Limitations<br />

Z ~<br />

≡<br />

⎛<br />

⎜<br />

⎜<br />

⎜<br />

⎝<br />

Z ~<br />

AA<br />

Z ~<br />

L<br />

AI<br />

⎞<br />

⎟<br />

⎟<br />

⎟<br />

⎠<br />

≡<br />

⎛<br />

⎜<br />

⎜<br />

⎜<br />

⎜<br />

⎝<br />

400<br />

400<br />

AC<br />

~<br />

f<br />

f<br />

∆V<br />

~<br />

L<br />

O<br />

B<br />

r,<br />

u<br />

B<br />

r,<br />

u<br />

AC<br />

1<br />

f<br />

⎞<br />

⎟<br />

⎟<br />

⎟<br />

⎟<br />

⎠<br />

R<br />

⎞<br />

⎟<br />

⎠<br />

⎞<br />

⎟<br />

⎠<br />

Equation 3.5-25<br />

Equation 3.5-26<br />

Equation 3.5-27<br />

Provision of accelerometer measurements at the sensor output interface<br />

depends on:<br />

• User measurement selection ( MS_MSAV1 bit 7-9 cleared )<br />

• Forcer acceleration limiting ( MS_AC_ER bit 22 is set )<br />

When active, if any of these limitations are violated, bits 7-9 (RPY) in the<br />

measurement ready flag MS_MSRY1 are cleared. Failure to provide<br />

measurements at the user’s request is indicated by setting bits 1-3 of<br />

MS_AC_VF. If the acceleration limit is exceeded bits 4-6 of MS_AC_VF<br />

are set depending on which of the accelerometers is affected.<br />

3.5.6 Output Interface<br />

The acceleration and velocity increments pass through a signed 16 bit digital<br />

interface at a frequency (ACfO) of 400 Hz (clock 9). These measurements<br />

are subject to interface range limits of ± 1 m/s and ± 400 m/s 2 respectively,<br />

and a one-cycle transmission delay.<br />

AC<br />

Z ~<br />

: =<br />

IF<br />

ϕ<br />

TD<br />

( ( ( ( Z ) ) ) ) ~<br />

IF IF IF<br />

ϕ ϕ ϕ<br />

Q<br />

LIM<br />

ZOH<br />

Equation 3.5-28

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