4.3
Other Software Notes
5
QUADROTOR PROTOTYPE CONSTRUCTION
Our estimates show that we can have an inner control loop of 260Hz, and if
we parallelize the moment and altitude calculations as shown above then we can
get about 40Hz faster for a control loop frequency of 300 Hz. Also of interest
is that the quadrotor control loop has a response time of 3.3 milliseconds. For
reference, the average human reaction time is roughly 200 milliseconds ([14]).
Finally, we are interested in code size. The floating point library has a
number of required support functions that do things such as convert to and
from floating point, compare floats, and so on that require space. We also
assume that 4 longs on average are used to setup each operation. This gives
totals of
Block
Longs
Moment
552
Altitude
275
Motors
468
So, if we were to do each instruction in sequence then it would take approxi-
mately 850 longs (sum without duplicates). Unfortunately, a Propeller cog only
has enough memory for 496 longs. If we break it into sections then the altitude
and motor calculations will fit into a single cog, but the moment block is too
big. Some optimizations will probably be able to reduce the size to fit.
All in all, the code performance estimates are looking very promising. We
should be able to achieve 100Hz update rates and the use of only two cogs
without too much trouble.
4.3
Other Software Notes
The other software in this project is standard. This project uses a Phython
GUI and a shell script for program compilation.
5
Quadrotor Prototype Construction
A quadrotor to the specifications is being constructed for this project.
5.1
Hardware
At this point in the project, we have developed four main areas of hardware:
the quadrotor frame, the motors and propellers used, the power board PCB,
and the thrust torque test stand. These components are, roughly, what will be
used for the rest of the project and are relatively static.
Frame Dimensions without rotors attached.
(longways)
28 1/4 inches (718 mm) X 28 1/4 inches (718 mm) X 4 5/8 inches (117mm)
Frame Dimensions with rotors attached.
(longways)
36 1/4 inches (921 mm) X 36 1/4 inches (921 mm) X 6 3/8 inches (161mm)
18
