Treadwell

built by Mark Weston

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Target Environment Locomotion Method
Indoors Treads
Sensors / Input Devices Actuators / Output Devices
2 edge detectors
2 Sharp GP2D15 IR sensors
2 DC motors
Control Method Power Source
Autonomous Battery
CPU Type Operating System
Atmel AVR8535 None
Programming Lanuage Weight
BASIC N/A
Time to build Cost to build
about 42 hours about $250Cdn
URL for more information
N/A
Comments
This robot was my assignment #2 entry for the Autonomous Mobile Robots course CCPS607 at Ryerson Polytech in Toronto, fall 2004. The objective was to build a robot that could move around a test surface without falling off, and could detect objects without colliding.

Treadwell is based on the lower half of a toy crane I bought at WalMart for $20Cdn. I removed the cab and crane arm and re-wired the motor harness. I glued an expanded PVC foam (similar to Sintra) base on top as a platform for the electronics. Since this was a work in progress, everything is breadboarded on the platform. There are two battery packs, one for the motors and one for the electronics. There are four sensors on Treadwell. Aluminum arms on either side of the tracks provide edge detection, and two Sharp GP2D15 infrared sensors are mounted under the front of the robot for object avoidance.

Treadwell is controlled by an Atmel AVR8535 uProcessor, with 8K of flash and 256 bytes of RAM. The motors are controlled by an L293DNE H-bridge chip. Programming is only about sixty lines of code in BascomAVR Basic.

Problems encountered? My motor controllers kept bombing out on me and I went through several chips before I realized the problem was a nominal power source. I was using a single 4-cell pack of NiMH batteries for logic, and it just wasn't enough to power the three chips. Uppping to an 8-cell pack and adding a 7805 gave me a perfectly reliable 5v supply and everything ran great after that.

Treadwell took about 42 hours to build, not including the lost week of debugging the power problem, and has probably cost about $250Cdn. This robot has earned it's place on the shelf, as the base has been pretty well maxxed out for weight capacity. I got perfect scores using this base for lab assignment 1 and 2, but he won't be suitable for lab's 3 and 4 which lead up to autonomous Sumo competition. He'll remain intact, as a constant reminder not to underestimate power consumption.

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