Experiences with an Architecture for Intelligent Reactive Agents

1. By R. Peter Bonasso, R. James Firby, Erann Gat, David Kortenkamp, David P Miller, Marc G Slack Presented By Tony Morelli 9/16/2004 Experiences with an Architecture for Intelligent Reactive Agents

2. 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.

3. 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)

4. 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

5. 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

6. 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

7. 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.

8. 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

9. 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

10. A Mobile Robot that Recognizes People - Skill Network

11. 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

12. 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.

13. A Mobile Robot that Navigates Office Buildings

14. 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.

15. 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.

16. 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.

17. Comparison With Other Work • 2 Categories of autonomous agents • Control physically embedded agents • Explore issues in general intelligence • 3T an example of the first

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

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

20. Robot ArchitecturesTask Control Architecture • No tiers • Cumbersome to have a general planner • All failures are lumped together • 3T handles failures at all three levels

21. 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

22. 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

23. Questions?