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Deploying RAXEM2 Planning Improvements in Daily Work Practice. Giulio Bernardi , Amedeo Cesta & Gabriella Cortellessa ISTC-CNR [PST] Institute for Cognitive Science and Technology National Research Council of Italy Planning and Scheduling Team http://pst.istc.cnr.it.

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Deploying raxem2 planning improvements in daily work practice

Deploying RAXEM2Planning Improvements in Daily Work Practice

Giulio Bernardi, Amedeo Cesta & Gabriella Cortellessa

ISTC-CNR [PST]

Institute for Cognitive Science and Technology

National Research Council of Italy

Planning and Scheduling Team

http://pst.istc.cnr.it

Work supported by ESA - the European Space Agency


Introduction
Introduction

  • Raxem is a software system developed to plan the upload of commands to the Mars Express spacecraft (orbiting around Mars since 2004)

  • Raxem project started after the success of Mexar2, which is used to plan data dumping activities from the spacecraft since 2005


Introduction1
Introduction

RAXEM

MEXAR


Commands from earth
Commands from Earth

  • The Mars Express probe receives instructions from Earth

  • Instructions are time-tagged telecommands (TCs)

  • On board, TCs are stored in a memory buffer, the Master Timeline (MTL)

  • TCs are discarded after execution

  • Deciding how to send data is not trivial…


How to send commands
How to send commands?

  • Related TCs are grouped in MTL Detailed Agenda Files (MDAFs)

  • Analogous to programs: they must be uplinked in an unique pass

  • Many constraints:

    • Communication is only possible during certain uplink windows

    • Sending data to Mars takes time

    • The Master Timeline has a finite capacity

    • A contingency plan is needed in case of failure


The mex up problem
The Mex-Up problem

  • An uplink plan must satisfy these goals

    • specifying when to uplink each MDAF

    • which modality of transmission should be employed, and

    • identifying a secondary uplink window to use in case of failures

All requested MDAFs must be uplinked as early as possible,

so that they are on board in time, given the finite capacity of

the MTL and the limited bandwidth of the transmission

channel, while trying to keep the MTL as full as possible


The mex up problem1

Master Time Line (MTL)

Telecommands (TCs)

AASFO1A3

AASFO1AX

AASFO1A3

AASFO1A4

AASFO1A3

AASFO1A5

AASFO1B3

AASFO1B3

AASFO1J3

Mars

Uplink Windows

OWLT -- One-Way Light Time

The Mex-Up problem

Spacon Instruction Form

(SIF)

RAXEM2

MDAF files

Earth


Before raxem
Before Raxem

  • The complexity of the Mex-Up problem was initially underestimated

  • Planning was carried on manually with paper and pencil

  • Disadvantages of manual planning:

    • Very time-consuming

    • Prone to errors

    • Poor optimization

    • Emergency re-planning was extremely difficult


The raxem solution
The Raxem Solution

  • A first version of Raxem was developed to assist users in solving the Mex-Up problem

  • Notable features:

    • Interactive plan generation

    • Graphical output of the solution (charts)

    • Inspection of spacecraft status

  • Raxem has been operational since summer 2007 [see Cesta et al ECAI-08]

  • The success of Raxem encouraged users to ask for a more complete tool…


Need for better integration
Need for better integration

  • A semi-manual procedure was employed to parse Raxem’s output and produce SIF forms (the official instructions delivered to uplink operators)

  • History of performed uplinks was held by external means

  • There was the opportunity to transform Raxem in a tool able to embrace the whole uplink work cycle


More than a planning tool
More than a planning tool

  • New goals for Raxem2:

    • Ability of maintaining the whole history of uplink operations (uplink database)

    • Acknowledgement of arbitrary changes on the planned solution by the users

      • This is necessary to accurately record actual uplink operations

    • SIF generation and management

    • User management and graphical improvements


The raxem2 solution

Raxem2 includes a new module that ensures complete and continuous management of the uplink problem

Existing functionalities have been comprehensively enhanced

The Raxem2 solution

AI Module

Interaction Module

Plan life cycle services

Domain Modeling

Uplink

DataBase

User

Management

Problem Solving

User Interaction

Spacon Instruction Form

(SIF) Generator

RAXEM2


Modeling with timelines
Modeling with Timelines continuous management of the uplink problem

  • Two relevant components of the model are the MTL and the Communication Channel

  • They are timelines:

    • They can report their status over time

    • Data can be allocated/deallocated on them over time

  • The MTL is a cumulative resource

    • Has a finite capacity

  • The Channel is a binary resource

    • Is either busy or free in a particular instant


Modeling with timelines1
Modeling with Timelines continuous management of the uplink problem

  • The act of data uplink is an Activity

  • An activity is modeled by two operations:

    • Channel operation

      • Represents the transmission of data during an uplink window

      • Requires the whole bandwidth of the channel for the entire duration

    • MTL operation

      • The act of storing data in the MTL

      • It “instantaneously” increases the amount of data in the MTL


Modeling with timelines2

MTL operation continuous management of the uplink problem

Size(MDAF)

Channel operation

durUpLink

stUpLink

Modeling with Timelines

1) MTL

Cumulative

resource

Last(MDAF)

First(MDAF)

2) Channel

Binary

resource


The solver
The Solver continuous management of the uplink problem

  • The software component that generates a plan

  • It employs a relatively simple constructive algorithm which provides a good trade-off between speed and optimality of the solution

  • It can relax constraints for some MDAFs if needed:

    • Confirmation Scheme (full or reduced?)

    • Uplink Scheme (secondary window or not?)

  • The user can change them too by providing hints to the solver


The main algorithm
The main algorithm continuous management of the uplink problem

foreachmdaftouplinkdo

whilenotallocateMDAF(mdaf,currentTime) do

if can relax then

relax(mdaf)

else

break

end while

ifallocated(mdaf) then

currentTime primaryUplinkEnd(mdaf)

end for

functionallocateMDAF(mdaf, currentTime)

start firstAvailableInstant(currentTime)

whilenotallocated(mdaf) do

try

ifnotmultiMDAFAllocation(mdaf,start) then

singleMDAFAllocation(mdaf,start)

onRetryLaterErrordo

start instantToRetry

end try

end while

end function


The persistence module
The Persistence Module continuous management of the uplink problem

  • Raxem’s data is held in the uplink database

    • It contains both the historical data and the working set

  • Persistence is handled using DAO objects implementing CRUD methods

  • The database backend is provided by SQLite library

    • All data is contained in a single file

    • No need for an external system

    • Backups and software deployment are easy

uplink.db

Uplink

DataBase

SQLite


Interactive planning
Interactive planning continuous management of the uplink problem

  • Raxem2 encourages user’s involvement in planning

  • Planning parameters can be altered for individual MDAFs:

    • Use reduced confirmation (shorter uplink)

    • Don’t allocate a secondary window

    • Exclude some MDAFs from the plan

  • Possibility of tuning the solution

  • Allows to perform what-if analysis


The raxem2 interaction
The Raxem2 interaction continuous management of the uplink problem

MDAF view

“Solve” button

  • Input for the AI solver

  • Confirmation scheme

  • Uplink scheme

SIF view


Great flexibility
Great Flexibility continuous management of the uplink problem

  • Users can override any decision made by the solver

  • Raxem2 accepts any change, and issues warnings if needed

  • Users can also inform the system about uplinks that actually happened

  • In both cases, the internal model of the problem is updated accordingly


The sif form view
The SIF form view continuous management of the uplink problem

Uplink intervals

(can be overridden)

Comment areas


Solution view before raxem
Solution view: before Raxem continuous management of the uplink problem

Olligram: hand-made gantt-like chart


Initial solutions in raxem v1
Initial solutions in Raxem v1 continuous management of the uplink problem

MTL Usage level

Uplink Graph

OnBoard Execution Graph


The integrated view in raxem2
The integrated view in Raxem2 continuous management of the uplink problem

MTL Usage level

Uplink Graph

OnBoard Execution Graph


Experimental results
Experimental Results continuous management of the uplink problem

  • Accuracy and performance tests

    • Accuracy: degree of adherence of the solution to user’s expectations (percentage)

    • Performance: time needed to produce a plan (seconds)

  • Two sets of data, about 60 MDAFs each

  • Tests show program behavior with different planning parameters

  • Raxem2 always outperforms Raxem by a great extent


Experimental results 2
Experimental Results (2) continuous management of the uplink problem


User assessment
User Assessment continuous management of the uplink problem

  • Raxem2 is operational at ESA since March 2009

  • Engineer work load was reduced from 5 hours to below 1 hour

  • The software was up to expectations with regards to

    • plan generation

    • handling of emergency situations

    • flexibility

  • SIF management has proven to be a very valuable feature


Conclusions
Conclusions continuous management of the uplink problem

  • Raxem2 is a successful example of integration of different technologies

  • Planning & Scheduling capabilities alone are not enough: users need a complete system to effectively perform their work

  • Seamless integration with the established work practice is necessary for acceptance in a rather conservative environment


Conclusions1
Conclusions continuous management of the uplink problem

  • Key factors for success

    • Continuous user involvement in planning

      • Small adjustments, what-if analysis

    • Centrality of user in the decisional process

      • Not a “black box” system

      • Operators can override any choice

    • Integration of different technologies

      • Needed to provide the most effective and complete user services


Questions
Questions continuous management of the uplink problem

?


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