Introduction to AI Robotics Chapter 7. The Hybrid Deliberative/Reactive Paradigm 2012. 11. 14

1. Introduction to AI RoboticsChapter 7. The Hybrid Deliberative/Reactive Paradigm 2012. 11. 14 Hyeokjae Kwon

2. Objectives • Describe the hybrid paradigm in terms of 1) SPA and 2) sensing organization. • Given a list of responsibilities, be able to say whether it belongs in the deliberative layer or in the reactive layer. • List the five basic components of a Hybrid architecture: sequencer agent, resource manager, cartographer, mission planner, performance monitoring and problem solving agent. • Be able to describe the difference between managerial, state hierarchy, and model-oriented styles of Hybrid architectures. • Be able to describe the use of state to define behaviors and deliberative responsibilities in state hierarchy styles of Hybrid architectures.

3. Basic Important concept • Paradigm • Paradigm is both a way of looking at the world and an implied set of tools for solving problems. • Sense, Plan, Act. • Commonly accepted robotic primitives. • Robotics have to go through these three, or at least two process to complete a mission. • Local Processing and Global World Model • Local: sensor data used in specific for each function. • Global: all sensor data is processed to single model.

4. SENSE PLAN ACT Hierarchical Paradigm • What are the two main features? • Robot operates in a top-down fashion. • All sensor data tends to be gathered to one global world model. A single representation that planner can use to rout the action.

5. SENSE Reactive Paradigm • What are the two main features? • Throw out planning all together. • The inputs to an act are the direct output of sensors. ACT

6. Hybrid Paradigm • Features of Hybrid Deliberative/Reactive Paradigm • It is reactive planning, Planning to subtask is done at one step. • Deliberative planning take a long time comparing to the time of reactive execution. • Sensor data go directly to each behavior but also available to the planner for construction of task-oriented global world model. • Model-based Architecture focuses on the creation and maintenance of a global world model.

7. Hybrid Paradigm • The basic models of Hybrid Paradigm • Sequencer: generates a set of behaviors for subtasks. • Resource manger: allocates resources to behavior • Cartographer: for creating, storing, maintaining map or spatial information. • Mission Planner: Interact with human and create a plan to achieve a goal • Performance Monitoring: monitor the process of the executing, It’s self-awareness.

8. PLAN Reactor Deliberator ACT SENSE Hybrid Paradigm • Organization : Plan, Sense-Act

9. Motivation of Hybrids • Cohesion (object oriented programming) • Reactivity: • Short time horizon (Present) • No global knowledge • Work with sensors and actuators • Deliberation: • Long time horizon (Past, Future) • Global knowledge • Work with symbols • Multi-tasking • Deliberative functions execute in parallel with reactive functions.

10. World Map/ Knowledge Rep Eavesdrop Virtual sensor Feedback Behavior Behavior Behavior control only Behavior Planning only Sensor 1 Sensor 3 Sensor 2 Sensing Organization The Map (World Model) • Can have its own sensors • Can “eavesdrop” on other sensors • Can act as “virtual” sensor

11. Connotations of Global • “Global” isn’t always truly global in Hybrids. • Behavioral Management • Planning which behaviors to use requires knowledge about current and future world state • Performance monitoring • Detecting task progress and sensor confliction require knowledge about the robot hardware and the overall goals. "Global" - "Deliberative" "Local" - "Reactive"

12. Architecture Styles • Managerial (division of responsibility as in business) • AuRA : Autonomous Robot Architecture • SFX : Sensor Fusion Effects • State Hierarchies (strictly by time scope) • 3T : 3-Tiered • Model-Oriented (Model serve as virtual sensors) • Saphira • TCA : Task Control Architecture

13. Styles of hybrid architectures ● Managerial styles● State hierarchies styles● Model-oriented styles

14. Managerial Architectures • Description -- top agents – high level planning ↓subordinate agents – refine plan, gather resources ↓ lowest level agents ▲ AuRAArchitectures ▲ SFX Architectures

15. Autonomous Robot Architecture (AuRA) • It consists of five subsystems -- planner : responsible for mission and task planning -- cartographer : all map making, reading functions -- motor : motor schema -- sensor -- homeostatic control : modify the relationship between behaviors by changing the gain as a function of robot or other constraints

16. Performance Monitoring Cartographer Mission Planner Sequencer Behavioral manager (mgr+schemas) Emergent behavior AuRA Architectural Layout deliberative reactive

17. The table below summarizes AuRA in term of the common components and style of emergent behavior

18. Sensor Fusion Effects (SFX) • description –It is an extension to AuRA. The extension was to add modules to specify how sensing and handling sensor failure.

19. Sensor Fusion Effects (SFX) • Deliberative layers -- Mission planner : acts as a CEO giving a directions -- effector -- Task -- SensorAll of three of above determine the best allocation of effect, sensing resource and perceptual schema. -- Cartographer : map making, path planning

20. Recognition perception Cartographer (model/map making) Deliberative Layer Managers Cerebral Cortex-like functions Deliberative Layer Choice of behaviors, resource allocation, motivation, context Sensor Whiteboard Behavioral Whiteboard Parameters to behaviors, sensor failures, task progress Behaviors (using direct perception, fusion) Superior Colliculus-like functions Sense Reactive Layer Sense Sense Receptive Field actions Sense Sense Sense Muscle Sense Sense Muscle Sense Sense Muscle Focus of attention, recalibration Sensor Actuators SFX (Sensor Fusion Effects)

21. Sensor Fusion Effects (SFX) • Reactive layersAll these layers reflect to - strategic behaviors and tactical behaviorsTactical behavior serves as filter on strategic commands to ensure to robot acts in a safe manner in as close accordance with the strategic intent as possibleThe interaction of strategic and tactical behaviors is still considered emergent behavior.

22. Tactical Behaviors

23. The table below summarizes SFX in term of the common components and style of emergent behavior

24. State-hierarchy Architectures • 3 – tiered (3T)

25. 3 – tiered (3T) • Structure-- planner : setting goal and strategic plans-- sequencer : select a set of primitive behaviors develop a task network-- skill manager : in this layer the skills have associated events to verify explicitly that an action has had to correct effect

26. 3T Architecture

27. The table below summarizes 3T in term of the common components and style of emergent behavior

28. Model-oriented Architectures • Two of best-known model-oriented architecture▲SaphiraArchitecture▲Task Control Architecture

29. Saphira Architecture -- PRS-Liteit is capable of taking natural language voice commands from humans and then operationalizing that into navigation tasks and perceptual recognition routines. -- virtual sensor -- navigation tasksmanage the behaviors -- LPS (Local Perceptual Space)determine the planning and execution improve the quality of the robot’s overall behavior

30. Saphira Architecture

31. The table below summarizes Saphira in term of the common components and style of emergent behavior

32. Task Control Architecture (TCA) -- Task Scheduling (Mission Planner)determine the goal and order of execution -- Path Planning (Cartographer) -- Navigation (Sequencer)to determine what the robot should be looking for, where it is, where it has been. -- Obstacle AvoidanceTo factor in not only obstacle but how to respond with a smooth trajectory for the robot’s current velocity.

33. Task Control Architecture (TCA)

34. The table below summarizes TCA in term of the common components and style of emergent behavior

35. Thank you!