Page 193 - Innovations in Intelligent Machines

State Estimation for Micro Air Vehicles 185
100
actual
p (deg/s)
estimated
0

- 100
0 5 10 15 20 25
400
actual
200 estimated
q (deg/s)
0
- 200
0 5 10 15 20 25
50
r (deg/s)
0
actual
estimated
- 50
0 5 10 15 20 25
time (sec)
Fig. 4. Actual and estimated values of the angular rates p, q,and r after low pass
filtering the rate gyros

Airspeed

Recall that
1 2
y diff pres = ρV + η diff pres .
a
2
Therefore, a simple estimation scheme is
$
2
ˆ
V a = C(s){y diff pres }. (18)
ρ
Figure 5 shows the actual and estimated altitude and airspeed using this
scheme. Again note that inverting the sensor models results in acceptable
estimates of altitude and airspeed.

Roll and Pitch Angles

Roll and pitch angles are the most difficult variables to estimate well on small
UAVs. A simple scheme, that works in unaccelerated flight, can be derived as
follows. Recalling that
˙ u + qw − rv + g sin θ
y accel,x = + η accel,x
g