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For Regular Seminar Robot Software Dec. 23, 2003 Jaesoo Lee jslee@redwood.snu.ac.kr RTOS Lab., SoEECS, SNU Contents Requirements of Robot Software History of Robot Software Architecture SPA (Sense-Plan-Act) Subsumption Hybrid Our Robot Software Architecture

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robot software

For Regular Seminar

Robot Software

Dec. 23, 2003

Jaesoo Lee

jslee@redwood.snu.ac.kr

RTOS Lab., SoEECS, SNU

contents
Contents
  • Requirements of Robot Software
  • History of Robot Software Architecture
    • SPA (Sense-Plan-Act)
    • Subsumption
    • Hybrid
  • Our Robot Software Architecture
  • Unexplored Issues Requiring Further Research
  • Remarks on Robot Research
robot software requirements
Robot Software - Requirements
  • Basic capabilities: deliberation + reactivity
  • Requirements
    • Programmability – easiness of introducing new goals
    • Autonomy and adaptability – aware current goal, execution context
    • Consistent behavior – reactions guided by objectives
    • Robustness – fault tolerance
    • Extensibility – pluggable, reusable, and reconfigurable components
    • Coordination – multiple goals, multiple (redundant) sensors
spa sense plan act
SPA (Sense-Plan-Act)
  • Features
    • Unidirectional and linear flow of control
    • Easy execution of a plan (task execution)
      • Partial orderings, conditionals, and loops
  • Shortcomings
    • Planning and world modeling are very hard problems
    • Open-loop plan execution is inadequate in uncertain and unpredictable environment
    • Very slow !!
subsumption
Subsumption
  • Vertical (hierarchical) decomposition of tasks
    • Behaviors in higher layer implement more complex, specified task
    • Each behavior still follows SPA architecture
  • “The World is its own best model”
    • No internal models, sense the surroundings on need instead
    • Direct, ego-centric, and distributed perception
  • Lisp-like languages to describe behaviors (Augmented Finite State Machine and connecting wires)
subsumption6
Subsumption

Level 2: explore

Level 1: wander

every 10sec

Level 0: avoid objects

reset

subsumption7
Subsumption
  • Advantages
    • Good reactiveness, inherent concurrency
    • The lower levels have no awareness of higher levels
    • Competitive coordination with inhibition and suppression mechanisms
    • Provides a development architecture to incrementally build and test a complex system
  • Shortcomings
    • Bad modularity
      • Upper layers interfere-with/depend-on the internal functions of lower-level behaviors
      • Increasingly complex
    • Bad runtime flexibility
      • Priorities are hardwired
    • No support for reverse suppression
    • No global planning
hybrid architecture
Hybrid Architecture
  • Goal: reactive planning
    • Slow planning (SPA, vulnerable to stale decision)
    • + fast reactivity (Subsumption, subject to fail on sensor errors)
  • Approach: reintroducing/separating planning
  • Organization: Plan, (“Sequencing”), Sense-Act
hybrid architecture9
Hybrid Architecture
  • 3 layer architecture
    • Deliberate/planning/deliberator
      • State reflecting predictions about the future
      • Reasoning, deliberation, planning, world modeling
    • Task-execution/sequencing/sequencer
      • State reflecting memories about the past
      • Coordination of multiple tasks
    • Reactive/skill/controller/behavior
      • No state, relying on current knowledge
      • Tight feedback control loops

Ex. NASA 3T Architecture

huddles and the trends
Huddles and The Trends
  • Planning, world modeling and increasing complexity of autonomous mobile robot system are turned out to be huddles very hard to solve.
  • Among these, AI and robot people are trying to solve the complexity problem by eliminating direct communications between modules
    • TCA by Reid Simmons at CMU
      • Central Control Module, one of framework component, routes messages, manages resources, and executes task sequences
    • CORBA is getting used for telerobotics
our approach
Our Approach
  • Applications in our view point
    • Implements task to achieve specific goals
    • By concatenating behaviors using partial orderings, parallel executions, conditionals and loops
    • Has activation conditions, parameter lists, and affinity
our approach12
Robot software component architecture

Componentization

Modularity, reusability

ORB middleware & component model

Communications

Modularity

Robot software component communication architecture

Deployment, implementation

Transparency, efficiency, reusability, retargetability, time-to-market

UML-based development tool

Integrated robot simulator

Design, implementation, simulation, packaging

Our Approach
unexplored issues
Unexplored Issues
  • Middleware issues on QoS
    • End-to-end QoS (deadline, delay, jitter, throughput)
      • Global priority
      • Reservation-based vs. priority-based communication
      • Collocated optimization
      • Schedulability analysis based on constraints annotation
    • Control quality
      • Clock synchronization
      • Real-time event, time-triggered event
unexplored issues14
Unexplored Issues
  • Architectural issues
    • Robot software component communication architecture
      • Prioritized suppression/inhibition
      • Subscription/Un-subscription of sensor data
      • Application affinities
    • Sequencer service
    • Reconfiguration on-the-fly and permanent storage
      • Accustom the robot
      • Affinities and default parameters for applications
      • Learning results, acquired landmarks, constructed maps
  • Requires corresponding supports of underlying ORB, OS, and hardware
remarks on robot research
Remarks on Robot Research
  • We can do constructing framework better than them, but how about planning and controls ?
  • Even though our approach seems to be on the right way, our potential contributions would be small compared to the paid efforts