Friday, November 25, 2011

Hexapod Robot

Pololu hexapod robot

Ever since I was a little kid, I have wanted to build a robot.  My first pathetic attempt was probably 30 years ago.  My "robot" consisted of a motor ripped out of my Big Trak hooked to a wired remote and huge caster wheels, both mounted to an old piece of drywall because I didn't have to tools to cut wood.  That miserable failure likely scared me away from building robots for decades.

Older, wiser, and now with better tools, one day I came across this.  Eureka!  As an entomologist who also happens to have a passion for robots, how could I pass up the geek love offered by a robot insect!  This robot is based on the Pololu Micro Maestro programmable servo controller.  It controls 3 micro servos that make the hexapod walk.  Obstacle avoidance is achieved with two IR distance sensors.  The Maestro chooses which walking program to run (forward, backward, left or right) based on input from the sensors.  The excellent build instructions made me confident that I could successfully build it.

So I ordered all the parts and built the hexapod in April 2011.  However, it is powered by a rechargeable NiMH.  I didn't have a charger to charge that battery with until now.  So the first test runs didn't happen until two days ago.  If you are curious, I used a Turnigy Accucel 6 charger.  Very inexpensive and it worked great.

my completed hexapod

The one tricky part was programming the robot to turn left and right.  The build instructions give pretty clear guidance on how to walk forward and backward, but they leave it up to you to figure out left and right.  That was the hardest part of the build.  So here are the Maestro settings for left and right turns.  "High" and "Low" refer to servo positions, not leg positions.  If you have programmed forward and backward then this should make sense to you.

Left Turn
Right LegCenter LegLeft Leg
Frame 0highlowlow
Frame 1lowhigh
Frame 2high
Frame 3highlow

Right Turn
Right LegCenter LegLeft Leg
Frame 0lowlowhigh
Frame 1highlow
Frame 2high
Frame 3lowhigh

Easy to build, relatively easy to program, and inexpensive (especially for a hexapod).  You can see how it works in the videos below.  Look closely and you can see the IR transmitters firing.  If I get motivated, I may play with the programming a little and see what else I can get it to do.

Update:  A picture of my little hexapod was featured on Make Magazine's blog!

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