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© The Aerospace Corporation 2014
SysML Reliability Modeling of Ground Based Systems with Virtualized Architectures
Myron Hecht and Daniel WintonThe Aerospace Corporation
Presented to
Ground Systems Architecture WorkshopFebruary, 2014
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Organization
• Overview
• A Very Quick Introduction to SysML
• Model Description and Modeling Approach
• Example Result
• Conclusions
3
Overview
• Question– How can Reliability Modeling and Prediction be Incorporated
into SysML models of Virtualized Ground Systems?• Motivation
– Growing use of SysML – Significant Potential Benefits for Tightly Integrating
Dependability Analysis into System Engineering
• Method– Package Structure– Abstract Classes– Structural and Parametric Models– Model Transformation and Results
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Reliability and Dependability are Important
• Required by Law– Public Law 111-123 “Weapons System Acquisition Reform Act of
2009,” Section 102 (codified as 10 USC 4 Section 139d)• DoD Policies
– CJCSI 3170.01, “Operation Of The Joint Capabilities Integration And Development System,” May, 2007: “ Materiel Availability and Operational Availability as Key Performance Parameters (KPPs) Reliability and Ownership Costs as Key System Attributes”
– DTM 11-03 “Reliability Analysis, Planning, Tracking, and Reporting”, OUSD AT&L, March 21, 2011
• Investment in RMA Pays Off– See GAO 2003 and DLA reports: Predator, Global Hawk cited as
showing Return on Investment of Reliability Improvement of 5:1 to 128:1
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ibd [B lock] A nti-Lock C ontro lle r1
«B lock»Anti-Lock C ontro ller
«B lockP roperty»d1 : T raction D e tecto r
«B lockP roperty»m 1 : B rake M odula to r
«B lockP roperty»d1 : T raction D e tecto r
«B lockP roperty»m 1 : B rake M odula to r
c1 :m odula to r inte rface
use
A Very Quick Introduction to SysML
interaction1. Structure
4. Parametrics
2. Behavior
3. Requirements
bdd [P ackage ] V ehic le [A B S ]
«B lock»Library ::
E lectronicP rocessor
«B lock»Anti-LockC ontro ller
«B lock»Library::
E lectro-H ydraulicV alve
«B lock»TractionD etector
«B lock»B rake
M odula tor
d1 m 1
definition
G rip p in g S lip p in g
L o s s O fT ra c t i o n /
R e g a in T r a c t i o n /
s tm T ire [T ra c tio n ] state machine
D e t e c t L o s s O f T ra c t io n
T ra c tio nL o ss M o d u la t e B ra k in g F o rc e
a c t P re ve ntL o c k up activity/function
OMG SysML Tutorial (www.omgsysml.org)
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Parametric Analysis with SysML (top level)
ibd [block] Anti-LockController [Internal Block Diagram]
d1:Traction Detector
m1:Brake Modulator
c1:modulator interface
ibd [block] Anti-LockController [Internal Block Diagram]
allocatedFrom«activity»DetectLosOfTraction
d1:TractionDetector
allocatedFrom «activity»Modulate BrakingForce
m1:BrakeModulatorallocatedFrom«ObjectNode»TractionLoss:
c1:modulatorInterface
1. Structure
4. Parametrics
ibd [block] Anti-LockController [Internal Block Diagram]
allocatedFrom«activity»DetectLosOfTraction
d1:TractionDetector
allocatedFrom «activity»Modulate BrakingForce
m1:BrakeModulatorallocatedFrom«ObjectNode»TractionLoss:
c1:modulatorInterface
satisfies«requirement»Anti-LockPerformance
par [constraintBlock] StraightLineVehicleDynamics [Parametric Diagram]
:AccellerationEquation[F = ma]
:VelocityEquation[a = dv/dt]
:DistanceEquation[v = dx/dt]
:BrakingForceEquation
[f = (tf*bf)*(1-tl)]
tf: bf:tl:
f:
F:
m:
a:a:
v:
v:
x:
v.Position:
v.Weight:v.chassis.tire.Friction:
v.brake.abs.m1.DutyCycle:
v.brake.rotor.BrakingForce:
Results
OMG SysML Tutorial (www.omgsysml.org)
Constraints
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Model Packages• Documentation
– Both source documents and documentation of the model• Abstract Classes
– Classes contain properties and behaviors that component blocks inherit• System
– Component Blocks– Block Definition Diagrams for composition of system, subsystem, and
components– Internal Block Diagrams for connectivity
• Constraints-Parameters– Constraint blocks for equations– Parametric diagrams for relations
• ValueTypes– Units in the model
• Instances– Separate package for each instance: Blocks and relations
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Abstract Classes Package
• Properties propagated to all child components
• Transverses composition hierarchies
• Examples• Reliability/Availability• IT Security• Failure Behavior• Capacity and
response time• Facility requirements
SysML Block Definition Diagram Used as a Class Diagram
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System ModelBlock Definition Diagram• The SysML Block Definition shows the blocks bound with directed
composition arrows
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Virtual Machines
Part Properties
Assumes Static Allocation of Virtual
Machines to Processors (if not, virtual machines
become part of Data Center Block)
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Constraints and Parameters PackageConstraint Blocks
• Internal Constraint Blocks– Use restricted syntax of SysML
constraint language
100
1 1 11 μ 01 μ
• External Constraint Blocks– Allows for more complex
functionality
Structural
Transactional
Internal Constraint Blocks can be mixed with Externals
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Instantiation of the Ground System ModelBlock Definition Diagram in Instance Package
Data Values go here
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Results of Quantitative Model: Derived recovery probability requirement
Coverage, failure rate, and restoration rate from SysML model were transformed by Paramagicand analyzed using a MatlabFunction
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
2
3
4
5
6
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x 104 Reliability
Coverage
Sys
tem
MTB
F
MTBF requirement of 2500 hours
Derived Replicated virtual server recovery probability requirement of 0.95
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Conclusions
• SysML can support quantitative analysis of ground systems with virtualized architectures– Methodology, Approach, and Results Demonstrated
• Benefits – Integration with system baseline
• Models can be immediately evaluated for conformance with dependability, safety, and other related requirements
• Traceability of conformance to requirements up through the TRD and into the CDD KPPs and KSAs
– Reduce cost and schedule impacts of • Evaluation of change proposals• Demonstrating compliance with RMA requirements and • Architecture and design rework in the event of non-compliance
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References
• Cameo Systems Modeler User Guide, Nomagic Inc., www.nomagic.com © 2013
• MATLAB version R2013a: http://www.mathworks.com• Paramagic User’s Guide, InterCAX, http://www.intercax.com, ©
2013• SA Friedenthal, A. Moore, R. Steiner, A Practical Guide to SysML,
The MK/OMG Press, www.mkp.com, © 2012 http://www.elsevierdirect.com/product.jsp?isbn=9780123786074
• RS Peak, RM Burkhart, SA Friedenthal, MW Wilson, M Bajaj, I Kim (2007) Simulation-Based Design Using SysML—Part 1: A Parametrics Primer. INCOSE Intl. Symposium, San Diego.
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