Sunday, April 26, 2009

CERS by Glenn Fannin

My name is Glenn Fannin from Texas. This is my first attempt at building a robot named CERS,
"Computer Enhanced Robi Senior". I purchased Robi a number of years ago but was very disappointed
with it as far as what I thought a robot should be. It had no computer at all, just a cassette
player that you could record control input from a remote control and play it back. No decision
making at all. I gutted the electronics, salvaging only the motor control I/C's. Installed a BS/2
wired to the motor controller I/C's, writing a quick program to check the motor controller. Next
came the sonar, a SRF04. Again a quick program to test the sonar. So far this was without the body
attached. I had to modify the body to accommodate the electronics I installed, also to allow a quick
access to the RS232 port. The head was fixed to the body so to add some realism I decided to attach
a servo to the head so it could pan right and left with the sonar mounted to the head. The sonar
works fairly well but it does have drawbacks. The sonar has difficulty detecting soft objects such
as upholstered furniture, a pile of clothes and even curtains covering a wall. To compensate for
this I added whiskers I made from wire coat hangers and a couple of lever switches. This has helped
a lot. But still not perfect. Other problems I encountered were the robot gets stuck in a loop. It
will encounter two or more walls and/or objects and spin back and forth trying to find a way out.
Another problem was CERS would take off while trying to download or after downloading a program. At
first I just added a pause at the beginning of the program. I later added a momentary push button
switch and programmed a loop that would continue looping until the button was pushed followed by a
short pause. I plan to add more sensors to compensate for some of the problems of object detection
and avoiding.
Cost to build was about $150, not including materials I already had. Time to build is hard to say.
As I was always modifying it both hardware wise and software wise as I was testing it. Collectively
as it sits now I would say about 7 days. Happy Roboting.

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