NASA Ames Research Center

1
Executive(s)

• Life in the Atacama Design ReviewDecember 19,
  2003
• Nicola Muscettola
• Vijayakumar Baskaran
• NASA Ames Research Center

2
Description and Motivation

• Model-Based Executive(s) for LITA
• Rover Executive
• Instrument Manager
• Modules were presented in September 2003

3
Rover Architecture using IDEA
Operator Interface
Offboard
Telemetry Router
Mission Planner
Waypoints
IDEA Mission Executive
Mission Executive
Status
Waypoint
Curvature, Speed Time
Curvature, Speed Time
Navigator
Health Monitor
Onboard
Stop
TerrainEvaluation
Odometry
Vehicle Controller
State Estimator
Stereo Mapper
Status
Status
Sensors
Images
4
Description and Motivation

• Model-Based Executive(s) for LITA
• Rover Executive
• Instrument Manager
• Modules were presented in September 2003
• Motivating System Requirements 3.1, 4.4, 5.4.1
  (but what does that mean really?), 5.5, 6.0

5
Key Requirements

• Rover Executive provide goal-driven commanding
  for high-level traverse and science operations
• Go to waypoint and Perform Detailed
  Investigations
• Instrument Manager allows single goal commanding
• Do mosaic instead of sequence of individual
  snapshots
• Executive invokes planner(s) if necessary to
  optimize course of action
• Executive translates between abstract goals and
  low-level commands
• Executive issues commands and responses as a
  consequence of internal (synchronous) or external
  (asynchronous) events
• Executive must be robust to wide range of faults
  (to be defined)
• Executive must guarantee response within required
  time limits

6
Software Organization
Rover Interface
Science Interface
Telemetry
Goals
Health Monitor
Telemetry Manager
Mission Planner
SciencePlanner
Measurements
Faults
Plans
Plans
State
State
Plans
Measurements
StateObserver
Rover Executive
State(All)
Positions
Stop
Actions
Waypoints
Instrument Manager
Mapper
Navigator
Position Estimator
Odometry
Curvature Speed
Vehicle Controller
Far-field Evaluator
Instrument Controllers
Near-field Detector
Images
Measurements
Data
Images
Proprioception Sun Image
Commands
Commands
7
Design Considerations

• Informing Design Principle
• The logic of execution and recovery shall be
  fully inspectable
• A model-based approach combines a declarative
  model, a general-purpose plan synthesis engine
  and heuristics
• A model-based approach is expected to allow quick
  incremental encoding of new recoveries from
  failure conditions as they are discovered
• Metrics
• Coverage of failure conditions
• Reaction time (as a function of model complexity)
• The design is influenced from Remote Agent and
  Gromit rover experience
• Reimplementation of the DS1 Executive as a
  model-based system vs the old procedural
  Executive in ESL
• Gromit (ATRV Junior) rover executive reimplement
  PRS-based executive from LAAS/CNRS

8
Technical Approach

• Multiple executives (Rover Executive and
  Instrument Manager) vs single executive
• Coupling between rover components
• Reaction time
• Currently focusing on single executive
  (consistent with Daves architecture concept)
• Modeled constraints can be switched on or off to
  support direct teleoperation modes (monitored
  mode of requirements 6.0)

9
Implementation Issues

• Prototype tests
• Simulator
• Mission Simulator Facility? Not clear if it is
  usable for real-time simulation
• Rover
• Multi-day scaled-down autonomous traverse with
  Gromit
• Expected timeframe April 2004
• Risks
• Complexity of incremental modeling
• Mitigations full engagement of trained Ames
  personnel, training, better modeling
  tools/languages
• Reaction latency
• Mitigations faster planning framework (new
  EUROPA), use of procedural task expansion (TDL)
• Issues
• Relation of executive to health monitoring and
  telemetry server. External modules or internal
  modules?
• What happens to executive during hybernation?
  Current design assumes it is always active,
  i.e., capable of reacting. Is this reasonable?
• Schedule issues need to firm up ASAP instrument
  models, message/command dictionary, mission
  operations concept.