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

Chapter 3 / Sensors
_ _
A model of this error currently fixed at 3 bits of quantised noise is shown in
Figure 3-17 and its output in Figure 3-18.
QUANTISED NOISE ( LSB )
8
6
4
2
0
-2
-4
-6
-8
0 200 400 600 800 1000
TIMESTEPS ( MSEC )
Figure 3-18 : ADC 3 Bit Random Noise
If this error is present on measurements used in a state observer based on
Kalman filtering principles it can have a destabilising effect unless
compensated for, since it is not Gaussian in nature.
3.2.2.4 Sensor Output Interface
In the simulation each sensor measurement passes through module IF_1553
described in §22.7.13. This superimposes the following digital interface
(I/F) transmission errors:
• I/F range quantisation ( bit 27 )
• I/F range limiting without 2s compliment wrapping ( bit 28 )
• I/F range limit with 2s compliment wrapping ( bit 29 )
• I/F time delay based on complete output intervals ( bit 30 )
The error control word is applied at sensor level hence the errors invoked
are applied to all the measurements from a sensor. The equivalent
MATLAB model is shown in Figure 3-19 in which the low frequency
update ZOH is evident to the sensor measurement output rate.
SM_I
1
OUTPUT
ZOH
RANGE
LIMIT
3.2-26
RANGE
WRAP
I/F
QUANT
I/F
DELAY
Figure 3-19 : Sensor Output Interface
SM_O
1