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- Two wheeler - Rebuilding the base.
With the robot showing
at least some will to cooperate it was time to
rebuild the base of it so that incremental encoders
could be fitted to the wheels. This will let me measure the actual speed of the wheels.
A new baseplate was
designed and cut out of 3mm aluminum plate. Except
for the holes around the perimeter used for stacking
the various levels quite a few mounting holes where cut in it so that circuitboards,
sensors and what not could be mounted to it.
Here's a couple of
photos showing the manufacturing of the base plate.
The first photo shows
the raw aluminum plate mounted on the machine table.
The second one shows all the holes drilled, on the
third all milling operation have been done and the
last one shows the finished plate cut out.
The next three photos
shows the other three parts needed (two each). The
first one shows the inner support bracket where the
encoder will be mounted. The second one shows the
outer support bracket and the third one shows the
This shot shows the
finished parts. You can see the wheels retrofitted
with pulleys for standard T2.5 belts, inner and
outer support bracket with it's bearings, the wheel
axles and incremental encoders.
With all the parts
ready it was time to put them together.
Here's two photos
showing the parts for the motors. The first one
shows the motors, mounting brackets and pulleys. The
second one shows the two motors with pulleys mounted.
In the following three
shots you can see how the wheels are mounted to the
base. The black thing on the inner support bracket
is the encoder mounting plate, the actual encoder is
snapped on to this plate and the encoder disc is
then fixed to the shaft with a small set screw.
There is a square hole in the base plate right next
to the inner support bracket that's supposed to line
up with the connector on the encoder so that the
cable from it can be routed thru the base plate.
The first of these two
photos shows the base with the wheels and motors
mounted. The second one has the encoders and IMU
mounted. The IMU consists of two boards, the lower
one (closest to the base) houses the
accelerometer and gyro and the upper board is the
amplifier board. This board is needed since the
impendance at the output of the sensor are a little
high seen from the PIC's A/D. By placing the IMU in
between the wheel like this it is very close to the
robots center of rotation.
The motor driver IC's
where moved from the solder less breadboard to a
some what more permanent veroboard mounted on top of
the base deck. This board is now replaced by an etched PCB
containing its own PIC microcontoller.<BACK><NEXT>