1. Magdalena Balazinska - Godfrey Tan
RoboGuard
Magdalena Balazinska - Godfrey Tan

2. Goals Guard a doorway or a hallway
Detect doorway: position in the middle.
Detect intruders and block their way.
Move along a straight line

3. Subsumption Architecture
IR Sensors
Guard d s
Stop
Bump Sensors
<Start> Bootstrap
Collide d
Motors
Shaft Encoders
Move Straight

4. Hardware and software components
Handyboard: MC68HC11, 32K RAM, 9V
Interactive C and Motorola assembly
2 DC motors (6.9V)
5 Sharp GP2D02 IR range sensors
5 bumper switches
2 shaft encoders
Lego body

5. 5 Sensors are positioned on a curve
3 Bumper switches
9V battery powering up the board and another 9V powering up the motors

6. Gear sets and motors

7. Sensors: the illusions and the reality
GP2D02 is an infrared sensor; it transmits an IR signal and receives it back to detect
The Specs say: 10cm to 80cm; an 8 bit number
GP2D02: 10cm to 80cm

8. Sensors: the illusions and the reality
Our experiments showed that the distance value given by the sensors were only reliable within a much shorter range (about half of the advertised range).
Each sensor is with its own personality.
Range: 4.5cm to 49.5cm
Angle: º to 13.7º

9. Demo…

10. Summary Successes Limitations:
Simple sensors and simple algorithms allow to achieve interesting behaviors
Autonomous creature performs what seems like an “intelligent” task
Limitations:
Sensors ranges
Batteries lifetime

11. Lessons learned Software eng. Robot eng. Reboot Change batteries.
Check last piece of code modified.
Check hardware connectors.
Optimize algorithms.Test!
Experiment!
Don’t trust doc: read code.
Don’t trust specs: experiment.
You may be poor.
Better be rich.