This paper describes two linked technology development projects to support Space Shuttle ground operations personnel, both during mission preparation analysis and related analyses in missions. The Space Propulsion Robust Analysis Tool (SPRAT) will provide intelligent support and automation for mission analysis setup, interpretation, reporting and documentation. SPRAT models the actions taken by flight support personnel during mission preparation and uses this model to generate an action plan. CONFIG will provide intelligent automation for procedure analyses and failure impact analyses, by simulating the interactions between operations and systems with embedded failures. CONFIG models the actions taken by crew during space vehicle malfunctions and simulates how the planned action sequences in procedures affect a device model. Jointly the SPRAT and CONFIG projects provide an opportunity to investigate how the nature of a task affects the representation of actions, and to determine a more general action representation supporting a broad range of tasks. This paper describes the problems in representing actions for mission preparation and their relation to planning and scheduling

Malin, Jane T.

Ryan, D. P.

Schreckenghost, D. L.

English

NASA Technical Reports Server

N95- 23750
Modeling Actions and Operations
Jane T. Malin
NASA Johnson Space Center
Automation & Robotics Div., MC ER2
Houston, TX 77058
Phone: (713) 483-2046 FAX: (713) 483-3704
malin@ aio.j sc.nasa.gov
to Support Mission Preparation
D. P. Ryan and D. L. Schreckenghost
Metrica, Inc.
NASA JSC, ER2
Houston, TX 77058
Phone: (713) 244-6135 FAX: (713) 483-3204
schreck@aio.jsc.nasa.gov
KEY WORDS AND PHRASES
Planning, action representation, modeling.
ABSTRACT
This paper describes two linked technology
development projects to support Space Shuttle
ground operations personnel, both during
mission preparation analysis and related analyses
in missions. The Space Propulsion Robust
Analysis Tool (SPRAT) will provide intelligent
support and automation for mission analysis set-
up, interpretation, reporting and documentation.
SPRAT models the actions taken by flight
support personnel during mission preparation
and uses this model to generate an action plan.
CONHG will provide intelligent automation for
procedure analyses and failure impact analyses,
by simulating the interactions between operations
and systems with embedded failures. CONFIG
models the actions taken by crew during space
vehicle malfunctions and simulates how the
planned action sequences in procedures affect a
device model. Jointly the SPRAT and CONFIG
projects provide an opportunity to investigate
how the nature of a task affects the representation
of actions, and to determine a more general action
representation supporting a broad range of tasks.
This paper describes the problems in representing
actions for mission preparation and their relation
to planning and scheduling.
INTRODUCTION
We are developing methods and tools to
provide intelligent automation and support for
mission preparation tasks. These require the
representation of mission preparation actions,
and this representation is affected by the nature of
the task being performed. We are investigating
action representations for two distinct types of
tasks, propulsion (PROP) consumables analysis
and operations procedures evaluation.
385
PRECEDING ,_',-,, -.': ......... _"" '" ":_ :_:_-_"
The consumables analyses conducted by
PROP consumables officers are a complex, time-
consuming mission analysis task. Throughout
the year preceding a flight, several types of
mission changes initiate new cycles of analysis
to determine how these changes affect
consumables. Iterative evaluations are needed
for nominal and contingency situations and for
proposed mission plans and objectives,
priorities, flight rules and procedures. These
mission and situation what-if analyses are used
to determine impacts to mission objectives and
procedures. During missions, additional
analyses are performed as needed.
Procedure evaluation has similar
characteristics. It is important both in impact
analysis during missions when an anomaly
causes space system reconfiguration, and in
procedure development and analysis during
mission preparation. Operations personnel
evaluate procedures against nominal and
contingency configurations, to assess which
procedures will be impacted and which should be
altered. When procedures are altered to fit the
current mission configuration, they are again
evaluated against the current mission situation
and related "next-worst" contingency situations.
These mission preparation tasks have common
characteristics and problems. They both involve
action representations, but for two distinct types
of tasks:
• Scientific and engineering analysis: data
generation and interpretation to answer
specific questions; e.g., consumables analysis
(SPRAT)
• Device operation and process control:
monitoring and control of physical devices and
processes in operations to achieve specific
behaviors and to respond to failures; e.g.,
procedure evaluation (CONFIG)
Action representations developed for scientific
and engineering analysis include the task of
developing scientific models [1] and data
analysis tasks for geological exploration [4].
https://ntrs.nasa.gov/search.jsp?R=19950017330 2020-06-16T08:33:10+00:00Z
Representationsdevelopedfor deviceoperation
andprocesscontroltasksincludemalfunction
proceduresandprocesscontroloperations.In
theSPRATandCONFIGprojects,weare
developingtechnologiesto addressbothtypesof
tasks,with thegoalof developingamoregeneral
actionrepresentation.A mutualbenefitisbeing
gainedbyderivinganactionandprocedure
representationwhichembracesbothtypesof task
domains.
SPRAT
Thegoalof the SPRAT project is to provide
advanced technology support for flight design
personnel and flight controllers to use when
conducting analyses prior to a mission, and
when performing new analyses in response to
anomalous situations that occur during a mission.
Initially, the project is focused on tools that
support the management of mission preparation
actions (the flight controller mission analysis
"procedures" performed pre-mission).
Mission preparation actions include the
execution of simulation and analysis software,
the interpretation of results from these
computations, and the generation of mission
preparation reports summarizing decisions.
Action management consists of creating and
modifying an action item list, tracking the
outcome of actions on the list, and creating and
modifying action descriptions and their relations.
Action list creation can be viewed as form of
planning, and action tracking as monitoring plan
execution. A knowledge base of domain actions
is defined in terms of goals and associated
activities. Actions from this knowledge base are
selected and placed on a managed list. The
execution of actions on this list is monitored to
determine how actions are dispositioned and to
document the outcome of actions. This tracking
information is stored in an action disposition
"database". This separation of the knowledge
base of available actions and the data base of
action tracking objects permits multiple actions
of the same type to be managed on one list. The
Figure illustrates this distinction.
SPRATs action representation has two parts:
• Description: goal of the action and conditions
that must hold prior to action execution.
• Tracking Record: information about action
assignment and disposition. The action
tracking information is retained as part of a
usage record stored in the action archive.
SPRAT provides for goal hierarchy and levels
of abstraction in actions by permitting subactions
(with subgoals) to be associated with an action.
Subactions are viewed as constituent actions, or
actions that must all be completed for a higher
level goal to be satisfied.
SPRAT represents action dependencies in
terms of inputs required by an action (data and
information from other actions) and outputs
generated by an action (software and manual).
When a change in mission def'mition data occurs,
Knowledge Base of Actions
Action Operator
Figure. The SPRAT Action Representation
386
the dependency constraints are used to determine
what new actions must be performed in response
to this change. Simple ordering constraints are
used to construct a list of actions. These
constraints include delivery deadlines and
priorities, and software precedence constraints.
The information needed to track the
disposition of actions includes information about
the intent of the action, the way the action was
conducted, and the outcome of the action. The
intent of the action is defined by the user's goal
or purpose in performing the action and the
mission context in which the action is relevant
(e.g., rendezvous, mission definition data). The
way the action is conducted is characterized by
the activities/steps composing the action (e.g.,
analyses performed) and the characteristics of the
tools used when performing these activities/steps
(e.g., low fidelity model of gravity used).
Information needed to track the action includes
information about deadline, priority, completion
status, and action responsibility.
The outcome of an action includes the
results of the analyses (e.g., computation of
consumables usage), the consistency of these
results with flight rules and mission objectives,
and the impact of these results on flight
procedures. It also includes information about
the execution of the action (was the action
completed and how was it completed, was the
action successful and if not why, why was the
action canceled or aborted, what was done in
response to an unsuccessful action). Information
about analyses that were canceled or
unsuccessful is useful, since knowledge about
why an approach wasn't pursued or what caused
it to fail may be useful when performing similar
analyses in the future.
The SPRAT prototype is implemented in G2,
extended with C routines for the data interface to
analysis software. It runs on Unix workstations.
Although the initial domain is consumables
analysis, the SPRAT project will develop both
flight-discipline-specific and generic tools for
other disciplines to build similar systems.
CONFIG
CONFIG is a prototype software tool which
provides integrated support for the modeling,
simulation and analysis of the structure,
behavior, failures, and operation of system
designs [5,6]. System models are structures of
connected component models, with embedded
time-related behavior models partitioned into
nominal and failure modes. The behavior of each
device during a simulation depends on its current
mode and on changes in its input caused by
operations or from other devices via local
connections or global flow path changes. These
capabilities enable several types of evaluation of
system operability, including analysis of impacts
over time of faults, failures, and procedural or
environmental difficulties.
CONFIG operations models support analysis
of plans and procedures for operation of systems
in nominal and contingency configurations.
They can also support simulation and analysis of
proposed changes (reconfigured systems and
revised procedures) that are developed during
operations in response to failures. The
operations modeling approach integrates both
with operations-execution-monitoring
representations that are based on device and
command states and with goal-based planning
representations [3].
CONFIG operations models represent
procedure actions and dependencies among these
actions. CONFIG operations models are
activity structure models that can be developed
independently from system models, yet link and
dynamically interact during simulation with
system models. Activities are the basic
components of a CONFIG operations model, and
are connected together in action structures. These
structures represent procedures or protocols that
interact with the system, to control and use it to
achieve goals or functions. Relations define
sequencing and control between activities and
connect devices with device-controlling activities.
CONFIG is implemented in the Common Lisp
Object System (CLOS) language, and runs on
Unix workstations. The current test model
domain for CONFIG is thermal bus systems,
including a model of a pump sating procedure.
PLANNING & SCHEDULING ISSUES
Action list management in SPRAT raises a
number of issues related to both plan creation and
plan repair. An objective of the SPRAT project
is to provide a tool that permits the flight
controller to create new actions dynamically,
and to link those actions into the representation
of precedence constraints. Such a capability
minimizes domain knowledge engineering, since
new actions can be added as needed. The ability
for the user to create new types of actions (not
yet developed) is related to the work by Martin
and Firby [7] on human repair of robot plans
387
"on the fly".
The dispositioning of actions on the action list
includes archiving the outcome of actions for use
in future missions. These action archives will be
used as starting points for creating action lists for
missions with similar issues and constraints.
Accessing and modifying these archived actions
remains an issue. These archived actions
resemble case bases of partial plans [8].
An issue related to the disposition of actions
is merging new items onto the list and deleting
items on the list that no longer hold. To be added
to the list, an action must be consistent with
• the mission definition (e.g., flight design data)
• the phase of the mission preparation
• the intent of the controller performing the
analysis (e.g., orbital vs. ascent analyses)
As the mission definition and user intent change
throughout mission preparation, actions items on
the list may be no longer relevant (e.g., new
flight design data). For SPRAT, the challenge is
to provide an adaptable plan with a goal structure
which models flight controller intent. The intent
of an action is needed to track the action (did
the action achieve the desired effect? was an
observed change intended?), and to provide
goals that can be manipulated using traditional
replanning techniques [2,3].
Procedure modeling in CONFIG uses an
action representation that interfaces with planning
systems, and that will be able to use SPRAT-
style action management. CONFIG and SPRAT
action representations can become more powerful
if action representations in planning and
scheduling become integrated.
BENEFITS
SPRAT models the actions taken by flight
support personnel during mission preparation.
CONFIG models the actions taken by crew
executing procedures. Jointly the SPRAT and
CONFIG projects provide an opportunity to
investigate how the nature of a task affects the
representation of actions, and to determine a
more general action representation supporting a
broad range of tasks. Such representations can
be applied to other types of activities (such as
software development and analysis over large
data bases). They also enable the development
of more flexible tools for representing and
reasoning about actions.
Application of CONFIG and SPRAT can
reduce ground operations costs not only on
console, but in a large and costly operations area,
mission preparation. Increased automation and
support for mission analysis and procedure
analysis will reduce analysis time, make impact
assessment quicker, reduce the number of
unnecessary analyses, reduce training time and
support better documentation. Common
representations for procedures, action lists, plans
and schedules can support the integration of
several types of operations support tools.
ACKNOWLEDGMENTS
Thanks to JSC flight controller Matthew
Barry, for his insight into mission preparation
tasks and design concepts for support systems.
Thanks to Tim Hill for his significant efforts in
the design and development of the SPRAT action
representation. Thanks to Land Fleming for
CONFIG design and programming. Thanks to
Barry Fox for his review comments.
REFERENCES
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[3] Georgeff, M.; A. Lansky., 1987. Reactive
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[4] Kant, E., 1988. Interactive problem
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[5] Malin, J.; B.Basham; R. Harris., 1990.
Use of qualitative models in discrete event
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[6] Malin, J.; D. Ryan; L. Fleming., 1993.
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