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Multi-Robot Behavioural Algorithms Implementation in Khepera III Robots. David Arán Bernabeu Supervisors: Lyuba Alboul Hussein Abdul-Rahman. Index. Introduction Player/Stage Khepera III robot Behavioural Algorithms Obstacle avoidance Wall following Robot following Conclusions.

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Presentation Transcript
slide1

Multi-Robot Behavioural

Algorithms Implementation in

Khepera III Robots

David Arán Bernabeu

Supervisors:

Lyuba Alboul

Hussein Abdul-Rahman

index
Index
  • Introduction
  • Player/Stage
  • Khepera III robot
  • Behavioural Algorithms
    • Obstacle avoidance
    • Wall following
    • Robot following
  • Conclusions
introduction
Introduction
  • Background
    • Multi-robot systems
    • Non-communicative systems
  • Objectives
    • Develop non-communicative behavioural algorithms
    • Implementation in Khepera III robots
  • Algorithms
    • Wall follow, obstacle avoidance & robot follow algorithms
  • Drawbacks
    • Two-robot system
    • Follower can not scan while moving
    • Leader out of the laser field of view
player stage
Player/Stage
  • Player: robot device interface
  • Stage: 2D simulator
  • Proxies
    • Position2dProxy
    • LaserProxy
player stage1
Player/Stage
  • Position2dProxy
    • void SetSpeed(double aXSpeed, double aDriveAngle)
    • double GetXPos()
    • double GetYPos()
    • double GetYaw()
  • LaserProxy
    • uint32_t GetCount () const
    • double GetRange (uint32_t aIndex) const
    • double GetBearing (uint32_t aIndex) const

β

α

Global axes

Local axes

khepera iii robot
Khepera III robot
  • Small differential wheeled mobile robot
  • 11 IR and 5 ultrasonic sensors
  • 2 DC motors
  • KoreBot: Embedded Linux
  • Wifi communication
khepera iii robot1
Khepera III robot
  • Laser range finder → Hokuyo URG-04LX
    • FoV: 240º
    • Angular resolution: 0.36º
    • 240/0.36 → ~667 points/scan
    • Range: 4 m
    • Max. scan rate 10 Hz → 0.1 sec

0º / 334

-120º / 0

120º / 667

behavioural algorithms
Behavioural Algorithms

Obstacle Avoidance

Wall Following

Robot Following

  • Leader robot
  • Function DivideLaser()
    • for all laser scans
      • if index is on the right
        • add range
        • new minimum
      • if index is on the left
        • add range
        • new minimum
      • if index is on the center
        • new minimum
      • calculate right / left mean
  • if left mean < right mean: turn right
  • if right mean < left mean: turn left

25º

-25º

Front side

Left side

Right side

-120º

120º

behavioural algorithms1
Behavioural Algorithms

Obstacle Avoidance

Wall Following

Robot Following

  • Follower robot
  • Also using DivideLaser()
    • if central minimum < stop distance
      • SetSpeed(0,0);
    • else
      • SetSpeed(Speed,0);
behavioural algorithms2
Behavioural Algorithms

Obstacle Avoidance

Wall Following

Robot Following

  • Keep constant distance

to the wall

  • Calculate slope of

a straight line

  • Functioning modes

SEARCH

If distance wall < detection distance

WALL FOLLOW

If left mean < right mean

If right mean < left mean

LEFT

RIGHT

If robot loses the wall

behavioural algorithms3
Behavioural Algorithms

Obstacle Avoidance

Wall Following

Robot Following

  • Slope of Straight Line

x1 = GetRange(165º)·cos(GetBearing(165º))

y1 = GetRange(165º)·sin(GetBearing(165º))

x2 = GetRange(205º)·cos(GetBearing(205º))

y2 = GetRange(205º)·sin(GetBearing(205º))

Wall to follow

x1,y1

75º

165º

35º

205º

x2,y2

behavioural algorithms4
Behavioural Algorithms

Obstacle Avoidance

Wall Following

Robot Following

  • Simulation
behavioural algorithms5
Behavioural Algorithms

Obstacle Avoidance

Wall Following

Robot Following

1st approach: Non-obstacle environment

  • Follower can only detect the leader
  • if laser detects something

save detecting indexes

calculate mean index

GetBearing(mean index)

do

diff = |GetBearing – GetYaw|

SetSpeed(0,±turn rate)

update GetYaw

whilediff ≠ 0

  • if GetRange(mean index) > Stop distance
    • SetSpeed(Speed,0)
behavioural algorithms6
Behavioural Algorithms

Obstacle Avoidance

Wall Following

Robot Following

2nd approach: Environment with obstacles

  • Movement recognition algorithm
  • If there is any movement, it\'s the leader
  • t0: scan and save ranges → vector0

t1: scan and save ranges → vector1

v_diff = vector0-vector1

if |v_diff[i]| ≠ 0 → movement → leader

calculate mean index of those detecting

GetBearing(mean index)

Final direction to follow

t1, final position

t0, initial position

behavioural algorithms7
Behavioural Algorithms

Obstacle Avoidance

Wall Following

Robot Following

2nd approach: Environment with obstacles

do

diff = |GetBearing – GetYaw|

SetSpeed(0,±turn rate)

update GetYaw

whilediff ≠ 0

  • if GetRange(mean index)>Stop dist
    • SetSpeed(Speed,0)
    • if GetRange()>Alone distance
      • SetSpeed(0,0)
      • Scan again
behavioural algorithms8
Behavioural Algorithms

Obstacle Avoidance

Wall Following

Robot Following

3rd approach: Physical robot

  • GetYaw() coordinate system different than in simulation

+2π

0

0

-2π

0

+π/2

-π/2

-3π/2

π/2

-π/2

π

Stage simulation

Khepera III robot

drawbacks
Drawbacks
  • Two robot system (1 leader, 1 follower)
  • Robot can not scan while moving
  • Robot out of the laser field of view
conclusions
Conclusions
  • Non-communicative multi-robot system
  • Simple algorithms
  • Basis of further developments
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