© 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

2

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

4

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

5

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

7

Ingredients of a SysML Parametric Analysis

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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)

12

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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Parametrics DiagramsLinking Constraints with Parameters

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Instantiation of the Ground System ModelBlock Definition Diagram in Instance Package

Data Values go here

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Part V Solve the InstanceParameter Assignment for Paramagic Solution

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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

7

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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