Experiences with an Architecture for Intelligent Reactive Agents

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Experiences with an Architecture for Intelligent
Reactive Agents

• By R. Peter Bonasso, R. James Firby, Erann Gat,
  David Kortenkamp, David P Miller, Marc G Slack
• Presented By Tony Morelli 9/16/2004

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Abstract

• 3T Robot Architecture
• 3 Levels of abstraction
• Variety of software tools have been created to
  implement this on multiple real robots
• Has been implemented on several different robot
  systems with different processors, operating
  systems, effectors, and sensors.

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Introduction

• Three interacting layers
• Dynamically reprogrammable set of reactive skills
  cooridnated by a skill manager
• Sequencer that controls skills to accomplis a
  specific task. Use the Reactive Action Packages
  (RAP)
• Deliberative planner that reasons in depth about
  goals, resources and timing constraints. Use the
  Adversarial Planner (AP)

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Software Tools for Arcitechture Implementation

• A number of tools were developed for integrating
  the three tiers together and providing the user
  with a paradigm for developing robotic
  applications

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Skills

• Input and Out Specification Each skill must
  provide a description of the inputs it expects
  and the outputs it generates
• Computational Transform The actual work
• Initialization Routine What to do on power up
• An Enable Function
• A Disable Function

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Sequencing

• Accomplish routinely performed tasks
• Task is dependent upon the robot's knowledge of
  the situation.
• Replies are through skills called events.
• Events take inputs from other skills
• Events notify the sequencer when a desired state
  has been detected.
• Lacks the foresite to achieve global behavior

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Planning

• Operates at the highest level of abstraction to
  make its problem space as small as possible
• Using the AP planner
• Multiagent control (robots usually have
  interaction with either people or other robots)
• Robots need to be able to work together
• CounterPlanning --- Need to do change plans when
  something an uncontrolled agent enters the
  picture.

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Applications of the Architecture

• Discuss the robot.
• Describe the task, the skills, the RAPs, and the
  plans
• Give results and lessons learned of the
  architecture

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A Mobile Robot that Recognizes People

• Search for a particular color shirt
• Crop the face and identify the person
• Skills Searching and tracking colors, cropping
  the face, recognizing the face, and obstacle
  avoidance.
• 20 RAPs to disable/enable skill sets and recover
  from errors.
• Did not use the planning tier of the architecture

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A Mobile Robot that Recognizes People - Skill
Network
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A Trash Collecting Mobile Robot

• Named Chip
• Skills Moving while avoiding obstacles, face a
  particular direction, finding an object visually,
  tracking an object, and reaching towards an
  object.
• Middle tier combined low level RAPs to make
  higher level RAPs
• No upper tier
• Successful in their experiments

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A Mobile Robot that Navigates Office Buildings

• Use sonar data for obstacle avoidance and laser
  scanner with bar coded tages for landmark
  recognition.
• Skills Watching for landmarks, moving to
  landmarks, and moving through doorways.
• RAPs for moving to a landmark or moving through a
  set of connecting spaces.
• Planner can plan a new path if the hallway is
  blocked.

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A Mobile Robot that Navigates Office Buildings
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Space Station Robots

• Plans are made by humans and sent to the planner
• The planner creates a series of RAPs.
• Simple failures are handled at the RAP level
• Drastic failures will could cause the planner to
  abandon all plans
• Implemented on a simulator prior to real life.
• Differences were in the interfaces and the level
  of autonomy. The planner and the RAPs were
  basically unchanged.

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Allocating Knowledge Across the Architecture

• Time Skill level has time in milliseconds,
  sequencer in tenths of a second, and the planning
  level in seconds.
• Bandwidth Skills are high bandwidth (image
  transferring). Between skill system and the RAP
  is small (enable/disable).
• Task Requirements A RAP should be broken down
  into skills. If a RAP starts doing look ahead,
  it should be considered an AP.

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Allocating Knowledge Across the Architecture (2)

• Modifiability Skills are compiled into runtime
  events. RAP and planner are based on
  interpreters and their behavior can be changed by
  changing RAP descriptions and planning operators.

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Comparison With Other Work

• 2 Categories of autonomous agents
• Control physically embedded agents
• Explore issues in general intelligence
• 3T an example of the first

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Robot ArchitecturesSubsumption

• Subsumption Decomposes robot control by task,
  rather than function.
• No architectural support for abstraction,
  planning or resource management.

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Robot ArchitecturesSSS

• Three layer architecture
• Subsumption is the middle layer
• Only been demonstrated on tasks involving pure
  navigation

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Robot ArchitecturesTask Control Architecture

• No tiers
• Cumbersome to have a general planner
• All failures are lumped together
• 3T handles failures at all three levels

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Non-robotic Agent Architectures

• Guardian Similar to 3T but with sequencing and
  deliberation performed by the same mechanism
• Decision making can be faster
• Cypress Their version of RAPs were difficult to
  integrate as they were not designed to allow
  integration with conventional AI planners

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Future Work and Conclusions

• Division of labor permits the generalization of
  knowledge across multiple projects.
• 3T can ease the development of software control
  code.
• 3T use in non-robotic control systems
• WWW Robot (retrieves maps to fight fires)
• Closed Ecological Life Support Systems
• Determine the planting cycles of various crops

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Questions?