Figure 3. Three-axis low-frequency piezoelectric sensor
Inertial mass 7, 8 and 9 attached to the bottom of piezoelectric elements 1, 3 and
5 of one channel and the top of piezoelectric elements 2, 4 and 6 of the second channel.
Outputs of piezoelectric elements both channels of the three sensing elements are
connected to the inputs of operational amplifiers 10, 11 and 12, the outputs of which
are connected to inputs of BCOM 13.
The piezoelectric elements of both channels of the three sensing elements Az, Ax,
Ay, which are located along the axes Oz , Ox and Oy are acting gravity
z
g
,
х
g
and
у
g
respectively. Also on each measuring axis acting a vertical acceleration of the aircraft
and instrumental errors from the influence of the residual non-identical structures of
the same piezoelectric elements and masses from the influence of changes in
temperature, humidity and pressure of the external environment.
If you use three dual-channel piezoelectric elements Az, Ax, Ay, the algorithm
of two-channel measurement setup described in [12], we get the inputs BCOM 13 three
signals, which contain double values
z
g
2
,
х
g
2
and
у
g
2
in which there is no value of
vertical acceleration of the aircraft and instrumental errors from the influence of the
residual non-identical structures of the same piezoelectric elements and masses from
the influence of changes in temperature, humidity and pressure of the external
environment. These signals are summed and amplified in the operational amplifiers
ОP10, OP11, ОP12 and served in BCOM 13, where the determining:
−
complete vector of gravity:
z
y
x
g
g
g
g
+
+
=
;
−
full acceleration module gravity:
2
2
2
2
2
2
2
)
2
(
)
2
(
)
2
(
z
y
x
z
y
x
g
g
g
km
kmg
kmg
kmg
g
+
+
=
+
+
=
,
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