Submitted version of the thesis - Airlab, the Artificial Intelligence ...

3.2. Motors 23
The initial design of the chassis was a bit different from the final configuration
seen in Figure 3.1. Even though the shape of the components did not
change, the position and orientation are changed in the final configuration.
The motor holders initially were intended to be placed on the top of the
bottom plexiglas layer. At the time when this decision was taken, we were
not planning to place the mice boards, but only to put the batteries and the
motor control boards. Later, with the decision of placing the mice boards in
this layer, in order to get more space, we decided to put the motors to their
final position. So this configuration increases the free space on the robot
layers to put the components, and also increases the robot height from the
ground that will result to better navigation.
Another change has been made by placing the second plexiglas layer.
Initially, we placed that layer using only three screws with each a height of
6 cm. The idea was using minimum screws, so that the final weight will
be lighter and the plexiglas will be more resistant to damage. Later, when
we placed the batteries, motor controller boards and the camera with its
holder, the total weight was too much to be handled by the three screws.
And additionally, we placed 6 more screws with the same height as before.
These screws, allowed us to divide the total weight on the plate equally on
all the screws and also enabled us to install springs and foams, to implement
bumpers that protect the robot from any damage that could be caused by
hits.
3.2 Motors
The actuator is one of the key components in the robot. Among the possible
actuation we decided to go with DC motors. Servo motors are not powerful
enough to reach the maximum speed. Due to noise and control circuitry
requirements, servos are less efficient than uncontrolled DC motors. The
control circuitry typically drains 5-8mA on idle. Secondly, noise can draw
more than triple current duringa holding position (not moving), and almost
double current during rotation. Noise is often a major source of servo inefficiency
and therefore they should be avoided. Brushless motors are more
power efficient, have a significantly reduced electrical noise, and last much
longer. However, they also have several disadvantages, such as higher price
and the requirement for a special brushless motor driver. Since they are
running at high speed we need to gear them down. This would also add