built by Daniel Kalny

Target Environment Locomotion Method
Indoors 3 Wheels
Sensors / Input Devices Actuators / Output Devices
2 simple encoders
4 button keypad
2 DC motors with gears
LCD from Nokia 3410
4 LEDs
Control Method Power Source
Autonomous Battery
CPU Type Operating System
Freescale 68HC908MR32 Forth
Programming Lanuage Weight
Forth less than 1 kg
Time to build Cost to build
1 year, still in progress about $150
URL for more information
Chela is my first robotic project. The aim of this project is primarily to gain some experience in autonomous mobile robot building. Therefore, I have chosen a classical design and taken a lot of inspiration from other robot builders presenting their robots here and elsewhere.

The robot has two wheels and one rear castor. The differential drive is provided by two DC motors with gears. The motors are equipped with simple home-made encoders. At the heart of the robot is Freescale microcontroller 68HC908MR32. This microcontroller provides PWM unit, SPI and UART units for communication, timers for encoders, and many digital and A/D channels for sensors and actuators.

Currently no sensor and only some input/output devices needed mainly for debugging (LCD, LEDs, beeper, keypad) are installed. When a basic motion feature - travelling to a given position - will be functionning, I plan to add more sensors, e.g. bumpers, an array of IR proximity sensors, a sonar, PIR detectors, photoresistors and so on. The last thing to add will be a gripper, allowing the robot to manipulate small objects (like soda cans).

The software for the robot is written in Forth language. I have spent a significant portion of time writing a Forth interpreter (in assembly) for my robot. Due to the fact that Forth language is self-contained, it is considered as an operating system as well. At the moment, the interpreter is almost finished, and I am currently working on odometry and navigation routines.

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