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# Using a Hierarchy of Reactive Behaviors to Simplify Nao Control

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My Bachelor thesis presentation.

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### Using a Hierarchy of Reactive Behaviors to Simplify Nao Control

1. 1. Using a Hierarchy of Reactive Behaviors to Simplify Nao Control
2. 2. Nao  25 Actuators  30 FPS Video  Infrared  Gyrometer  Accelerometer  Good at falling over Price: \$ 4000
3. 3. COMPLEX PROBLEM
4. 4. Ronaldo  639 Actuators  18 FPS Video  No Infrared  Good balance  Proven technology  Also good at falling over Price: \$ 94,000,000
5. 5. 94 000 000 / 4000 = 23 500 Can twenty-three-thousand- five-hundred Nao bots beat Ronaldo? (think about it)
6. 6. World VS Belgium VS Robots Cristiano Ronaldo \$ 94 000 000 Zinedine Zidane \$ 73 000 000 Marouane Fellaini \$ 20 000 000 Vincent Kompany \$ 12 500 000 Honda Asimo \$ 1 000 000 Nao RoboCup Edition \$ 4 000
7. 7. Using a Hierarchy of Reactive Behaviors to Simplify Nao Control
8. 8. “Reactive behavior” means  Output is a direct reaction to the input  No reasoning about symbolic world knowledge  End result emerges from the interaction of a number of behaviors  Interaction occurs through changing other behaviors' measure of activity
9. 9. “a Hierarchy”  Behaviors are ordered in layers  A behavior can only change the activation factor of a behavior on the layer directly below it
10. 10. Like subsumption...
11. 11. But with layers...
12. 12. What does this mean?  Behaviors on the bottom layer only influence actuators  The next layer can configure the last layer.  It can select or mix behaviors!  If the bottom layer has a behavior “go_left” and a behavior “go_right” the second layer decides where to go  This way each layer gets more abstract
13. 13. Speed  Each layer is updated by the control loop at a different speed.  Bottom = fastest  Speed decreases with each layer Why ?  Low level actuator control needs fast feedback  High level decisions don't need to be re- evaluated every 20 ms
14. 14. Speed IIo  Behaviors can only access sensors and actuators on their own layer  The speed at which a sensor updates determines which layer it is placed on  Similarly, actuators are placed on the layer the best correspond to  Behaviors are placed on the layer that gives them access to the right sensors, actuators and lower level behaviors
15. 15. Aggregated percepts  Sensors are given access to the history of the entire layer below  This way a sensor on layer z can “sense” the average output of sensors on layer z – 1  So as we move up the chain, sensors generate increasingly abstract percepts  Similarly, actuators can set abstract internal variables (parameters)
16. 16. A hypothetical example
17. 17. A real example
18. 18. Lessons learned
19. 19. A Layered Hierarchy of Reactive Behaviors can Reduce Complexity of Robot Control
20. 20. World Cup 2006 A Team of Dedicated Germans Can Beat Ronaldo 3 1 This is good news for UM