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Behavior Based Control

Behavior Based Control. Institute for Personal Robots in Education (IPRE) ‏. Behavior Based Control. Behavior 2. Behavior 1. Behavior 3. Arbitrator. Robot Actions. Behavior Based Control. Behavior based control allows you (the programmer) to specify robot behaviors.

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Behavior Based Control

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  1. Behavior Based Control Institute for Personal Robots in Education (IPRE)‏

  2. Behavior Based Control Behavior 2 Behavior 1 Behavior 3 Arbitrator Robot Actions

  3. Behavior Based Control • Behavior based control allows you (the programmer) to specify robot behaviors. • Multiple behaviors “fight it out” for control of the robot.

  4. Each Behavior • May use sensor values to determine what to ask the robot to do, or may not. • Makes a recommendation to the arbitrator about what action the robot should take. • or....tells the arbitrator that it doesn't have an opinion.

  5. The Arbitrator • Asks each behavior what the robot should do. • Decides which behavior(s) to use. • Advanced Arbitrators may even allow the robot to do a mixture of different behaviors at the same time!

  6. Implementing a Behavior based control system • You need to specify each behavior...and... • An arbitrator that decides which behavior to follow at any particular point in time and makes the robot's actuators follow that behavior's recommendation.

  7. Problem Statement: • Your robot should move continuously looking for a bright light. When it finds a bright light, it should go towards it. The robot should turn to avoid hitting obstacles.

  8. Finding Behaviors (look for verbs!)‏ • Your robot should move continuously looking for a bright light. When it finds a bright light, it should go towards it. The robot should turn to avoid hitting obstacles.

  9. Summarized: • Move • Look (for light)‏ • Go to the light • Avoid obstacles

  10. Combined/Simplified: • Move • Go towards light • Avoid obstacles

  11. Prioritized: • 1st: Avoid obstacles • 2nd: Go towards light • 3rd: Move

  12. Questions about behaviors • How does the behavior communicate with the arbitrator? • How does it indicate what action it wants the robot to take? • How does it indicate that it doesn't have a recommendation? • All of these questions can be answered by building the Arbitrator.

  13. The Arbitrator • Calls each behavior. • Sees what each behavior wants to do. • Selects the recommendation from the highest priority behavior. • Tells the robot to do that behavior's recommended action.

  14. The Arbitrator/Behavior interface • Each behavior needs to return the same data (in the same order) to the Arbitrator. • You can pick any data and any order you want, but you must be consistent in all of your code. • For this example, we choose to return: • Boolean – Tells if a behavior has a recommendation (True) or not (False)‏ • Translate Value – Float from -1.0 to 1.0 telling the recommended translate amount. (0.0 is stopped)‏ • Rotate Value – Float from -1.0 to 1.0 telling the recommended rotate amount. (0.0 is no rotation)‏ [ True, 0.0, 0.0 ] - Represents a recommendation to stop completely.

  15. Behavior 1: Cruse #Move behavior: Always recommends that the robot move. def move(): return( [ True, -1.0 , 0.0 ] )‏

  16. Behavior 2: Avoid Obstacles #Avoid behavior, makes the robot turn away from obstacles. def avoid(): sensorVals = getIR()‏ leftV = sensorVals[0] rightV = sensorVals[1] if (leftV == 0) or (rightV == 0): return( [ True, 0.0 , 1.0 ] )‏ else: return( [ False, 0.0, 0.0 ] )‏

  17. The Arbitrator: Putting Avoid & Move together! #Calls each behavior in the order listed. If a behavior gives a recommendation, # arbitrate passes the recommended action on to the robot and then skips the # rest of the behaviors. (So avoid has a higher priority than move.)‏ def arbitrate(): behaviors = [avoid, move] for behavior in behaviors: values = behavior()‏ hasRec = values[0] transVal = values[1] rotVal = values[2] if (hasRec == True): translate(transVal)‏ rotate(rotVal)‏ return()‏

  18. Behavior 3: Seek Light #seekLight behavior: turns towards (bright) light def seekLight(): values = getLight()‏ leftV = values[0] rightV = values[2] if ( leftV > 200) and (rightV > 200): return( [False, 0.0, 0.0] )‏ else: if (leftV < rightV): return( [True, -0.5, 0.33] )‏ else: return( [True, -0.5, -0.33] )‏

  19. Updating the Arbitrator for a new behavior #Calls each behavior in the order listed. If a behavior gives a recommendation, # arbitrate passes the recommended action on to the robot and then skips the # rest of the behaviors. (So avoid has a higher priority than move.)‏ def arbitrate(): behaviors = [avoid,seekLight, move] for behavior in behaviors: values = behavior()‏ hasRec = values[0] transVal = values[1] rotVal = values[2] if (hasRec == True): translate(transVal)‏ rotate(rotVal)‏ return()‏

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