Physics Based Formation Behavior in Autonomous Robots

Mark Patterson

Emergent Behavior

• Emergent or global behavior is observed in the interactions between homogeneous robots.

• Autonomy / Independence– Local decision procedures

• Social based and hierarchal based behavior• Physics based behavior

– Provides theoretical guarantees about behavior.

Formation Behavior

• Robots will naturally form into structures using a force vector.– Four structures of interest

Diamond Wedge Line Column

Formation Behavior• Formations within a volume

– Even distribution regardless of the number of robots.

Practical Applications of Formation Behavior

• Distributed Arrays / Matrices–Investigation

–Search

–Exploration

–Surveillance

–Defense

System Development

• Design, fabricate, and implement fleet of inexpensive autonomous mobile robots

– Localization / Where am I?• Detecting the presence of other robots

– Communication

• Knowledge of environment– Sensors

– Error control• IR Protocol

– 8 bit data/32 bit signal

• RF Protocol– 8 bit data/8 bit signal

– Stop and wait ARQ

• Asynchronous Serial Communication– Implementations - Pulse Code Modulation (PCM)

• Infrared– Transmitter and receiver “on board” the controller module.

• Radio frequency - 300 Mhz – Inexpensive garage door transmitters and receivers.

Communication

Localization

• Force vector– Range– Bearing

• Beacon system– Trilateration

• Position relative to at least two other objects– Distance between each of three objects

a

b

c

(0,0)

Ultrasonic transducer beacons

• Inexpensive

• Omni-directional

• Effective range – approx. 1 meter

• Reflexive response• response time + (2)(time of flight)

(0,0)

Prototype Lego™ robot

Current & future work

• Finish development of ultrasonic transducer beacons.

• Implement localization algorithm

• Demonstrate and record physics based formation behavior.

• Validate the behavior using formal methods.