1 Benjamin Kruse Libraries for Model-Based Mechatronic Concept Design in SysML Benjamin Kruse Engineering Design and Computing Laboratory, ETH Zurich.

1Benjamin Kruse

Libraries for Model-Based Mechatronic Concept Design in SysMLBenjamin KruseEngineering Design and Computing Laboratory, ETH Zurich

2Benjamin Kruse

Agenda

Motivation & Introduction Functional Modeling Library in SysML

Library Definition and Usage User Study for Library Evaluation

Amesim Simulation Library in SysML Component Modeling Library in SysML Outlook Summary

Engineering Design + Computing Laboratory

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Motivation: Rising Complexity


Systems Engineering Vision 2025 Project Team. “A World in Motion – Systems Engineering Vision

2025.” International Council on Systems Engineering. 2014.

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State of the Art in Research & Industry

Functional Architectures in SysML1 (FAS) Method for obtaining functional architectures

for systems in block-oriented form By using heuristics for grouping functions

and allocating them to functional blocks State of usage of SysML2

Functional modeling has the most added value for users

Needed improvements: Usability of SysML needs to be improved Modeling methods and guidelines are needed


1) Lamm, J. G., and Weilkiens, T. “Method for Deriving Functional Architectures from Use Cases.” Systems Engineering, 2014; 17:2, p. 225-236.

2) Albers, A., and Zingel, C. “Challenges of Model-Based Systems Engineering: A Study Towards Unified Term Understanding and the State of Usage of SysML.” Smart Product Engineering, Springer, 2013.

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Vision 2025 & Evolving MBSE

SE Vision 20251

Formal systems modeling Composable design: A key to productivity

By combining formal models from libraries

Evolving SysML2

Include precise semantics that avoid ambiguity

Be usable for multiple application domains Integrate across discipline-specific

engineering tools Primary consideration: Usability!


1) Systems Engineering Vision 2025 Project Team. “A World in Motion – Systems Engineering Vision 2025.” International Council on Systems Engineering. 2014.

2) Friedenthal, S. and Burkhart, R. “Evolving SysML and the System Modeling Environment to Support MBSE.” in: Insight, INCOSE, 2015, 18:2, p.39-41

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Approach for Mechatronic Concept Generation

Mechatronic Concept Models

…

Electrical

Mechanical

Generic Multi-Disciplinary Model Libraries

ModelSimulation

ModelGeneration

Formal & Standardized Language

Task

Specification


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NIST Functional Basis (FB)

Established collection of operators and flows to be combined into elementary functions of engineering systems

RotationalEnergy: Decrease

ControlSignal

RotationalEnergy

RotationalEnergy

i.e. braking of electric carDecrease. To reduce a flow in response to a control signal. Example: Closing the value further decreases the flow of propane to the gas grill.

Rotational energy. Energy that results from a rotation or a virtual rotation. Example: …


Hirtz, J., Stone, R. B., Mcadams, D. A., Szykman, S., and Wood, K. L. A: “Functional Basis for Engineering Design: Reconciling and Evolving Previous Efforts.” No. 1447, USA: NIST. 2002.

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ElementaryFunction: FB operator as SysML activity BasicFlow: SysML block to define object flows

Functional Modeling Library in SysML


Kruse, Münzer, et al.: “Workflow and Modeling Conventions for Function and Product Structure Modeling of Mechatronic Systems in SysML using Libraries”. Mechatronics 2012, Linz, Austria, 2012

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Functional Modeling


deco

mpo

s

e

electric car main function

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Functional Decomposition Step-by-step functional

decomposition, until

elementary functions

from library are usedOverall Function:e.g. Control Motion

User-Defined Function:e.g. Recuperate Braking Energy

Elementary Function:e.g. ElectricalEnergy : Store


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Function Library Evaluation

Common advantages of reuse in software development1 and engineering design2: Better understanding of a system

built from building blocks Higher model and system quality Faster development

Achievable through Function Library? Experiment Hypotheses:

Using the library leads to better models Using the library leads to reduced workload


1) Chughtai, A., and Oliver V. "Software-Wiederverwendung-Theoretische Grundlagen, Vorteile und realistische Beurteilung." in: Software-Management: Beherrschung des Lifecycles. Editor: Versteegen, G., Springer, 2002.

2) Duffy, A. H. B., and Ferns, A. F. “An Analysis of Design Reuse Benefits.” Proceedings of the 12th International Conference on Engineering Design (ICED ’99). 1998; p. 799-804.

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User Study for Library Evaluation

Measurements for model quality: More functionalities covered (compared to master models)

to access task completion Higher relative number of functions of the Functional Basis Not: bigger model size (because not corresponding to model

quality) Measurements for modeling workload (Better

Usability?): TLX1 test to measure the perceived workload of participants

(Established test by NASA) ETH tools course for functional modeling & SysML:

11 participants (inexperienced students) 3 afternoon sessions


1) Hart, S. G. & Staveland, L. E.: “Development of NASA-TLX (Task Load Index): Results of empirical and theoretical research.” in: Human Mental Workload. Amsterdam: North Holland Press. 1988.

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Experiment Plan

Factor: With SysML library:

Functional Basis incorporated in SysML

Without SysML library:Functional Basis given on paper

Tasks: Creating functional models of a coffee maker Task 1:

Brewing coffee Task 2: Grinding

coffee beansEngineering Design + Computing Laboratory

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Results: Learning effect Library increased workload!

0

10

20

30

40

50

60

70

80

90

100

Overall Perceived Workload

Day 1 (without SysML library) Day 2 (with SysML library)Day 3-1 (without SysML library) Day 3-2 (with SysML library)

Results: TLX (NASA)


010203040506070

Day 3-1 Workload (without library)

Mental Physical TemporalPerformance Effort Frustration

Importance Weight

Rating

010203040506070

Day 3-2 Workload (with library)

Mental Physical TemporalPerformance Effort Frustration

Importance Weight

Rating

(0 = minimum workload, 100 = maximum workload)

1: n

o

libr

ary

2: w

ith

libr

ary

3-1:

no

libra

ry

3-2:

with

lib

rary

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Results: Questionnaire & Comments

Questionnaire: “Modeling with the library in SysML improved the resulting

model / modeling process compared to not having the library.”

Approval rating: 59 – 60 (0 = completely disagree, 100 = completely agree)

Comments about library usage:


“library forces you to break down the activity further”

“having to look up functions, decide which are appropriate”

“triggers my thought process”

“resulting model is more fundamental”

“very limited by the functions of the library”

Increased workload & comments: Results of using Functional Basis

and NOT directly of using the library

Productivit

y

Time

S. Rifkin: “Why new software processes are not adopted”, Advances in Computers, (59). 2003

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Results: Library & FB Acceptance

Library & FB acceptance: Significant correlation (p < 0.001) between availability of

library and the number of functions from library Significant correlation

(p < 0.001) between availability of library and relative number of FB functions

Library used when available(good user acceptance)

Functional Basis barely used without library


No SysML Library With SysML Library

Rel

ati

ve

# o

f F

B f

un

ctio

ns

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Results: Task Completion

Grade of task completion1: Significant correlation

(p < 0.018) between availability of library and ratio of covered functionalities

Significant correlation (p < 0.021) between ratio of FB functions and ratio of covered functionalities


1) Annett, J.: “Hierarchical Task Analysis”. In: Hollnagel, E., Ed., Handbook of Cognitive Task Design, Lawrence Erlbaum Assoc. Inc., Mahwah. 2003. 17-35.

Having the library (and therefore using the Functional Basis) leads to a broader coverage of the necessary functionalities

Rel

ati

ve

# o

f fu

nct

ion

alit

ies

No SysML Library With SysML Library

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User Study – Summary


Better & more formal models

Higher usage of formal FB terms

More functionalities

covered

Increased workload

(Due to usage of FB, not due to the

library)

Experiment assumption of general usage of FB

not applicable

Reuse benefits?

Better understanding

of a system

Higher model /

system quality

Faster development

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Requirements

Use Cases

Functions

Behavior

Structure

Further development process


Task

…

ComponentLibrary

BehaviorLibrary

Function Library

(FBS)

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Amesim Simulation Library in SysML

Incorporation of Amesim library into SysML

Model transformations between SysML IBDs & Amesim models


Library (SysML)

Model (SysML)

Model (Amesim)

Library (Amesim)

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Component Modeling Library in SysML

Structural Components: (Mostly) Physical entity or module Following eCl@ss standard

Model: Block with attributes (e.g. weight,

etc) Interfaces:

Ports with additional information (e.g. type, etc) and flow types corresponding to function library


Library

Model

Image source: http://www.cross-morse.co.uk/timing_belt.asp

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column: elementary functions

as actions (operator & flow)

row: (mostly physical)

components from library

ElectricalEnergy:Sto

re

(for recuperation)

is allocated to

the component

“Car Battery”

Allocation Matrix: Usage-to-Definition


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Library Summary

Function Library Based on the defined terms of the Functional Basis Increased workload for inexperienced users Higher usage of FB terms More functionalities covered

Amesim Simulation Library Corresponding to Amesim

simulation elements

Component Modeling Library Based on eCl@ss standard For reusing common elements


Better & more formal functional models

Composing configurations

Composing traceable partialsimulation models in SysML

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Outlook

Combination of model-based libraries in SysML and automated design synthesis Model transformation for solution space exploration

using boolean satisfiability1 Model transformations for system behavior simulation Automated synthesis & evaluation of SysML models

Further testing and validation with industry


1) Münzer, C., Helms, B., and Shea, K. “Automatically Transforming Object-Oriented Graph-Based Representations into Boolean Satisfiability Problems for Computational Design Synthesis.” Journal of Mechanical Design, 2013; 135:10

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Münzer, C., Helms, B., and Shea, K. “Automatically Transforming Object-Oriented Graph-Based Representations into Boolean Satisfiability Problems for Computational Design Synthesis.” Journal of Mechanical Design, 2013; 135:10

Motion

Engine rpm

Problem

TGearboxR R

Combustion Engine R

Brakes andWheels

RT

System Boundary

Automated Design Synthesis

Acceleration

Gear

Brake

System Boundary

T

RElectric

MachineWheels

and Vehicle

RT

Battery

RCombustion

EngineAcceleration

junctionRR

GearboxPlanetary

DriveR

RR

System Boundary

T

Wheels and

Vehicle

RT

Battery

RCombustion

EngineAcceleration

junctionRR

GearboxElectric

Machine RR

System Boundary

T

Wheels and

Vehicle

RT

Battery

RCombustion

EngineAcceleration

junctionRR

Gearbox

Electric Machine R

R


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Problem

TGearboxR R

Combustion Engine R

Brakes andWheels

RT

System Boundary

Automated Simulation

Automated map between elements and corresponding simulation models

Enables quantitative feedback on generated concepts and optimizationMünzer, C. and Shea, K.: “A Simulation-based CDS Approach:

Automated Generation Of Simulation Models Based From Generated Concept Model Graphs”, Proceedings of the ASME IDETC/CIE 2015, DETC2015-47353


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Simulated vs. Optimized Solutionsin

teg

rate

d e

rro

r e i

[m

]

total CO2 emissions [g]


Münzer, C. and Shea, K.: ASME IDETC/CIE 2015

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Summary


• Physical entity or module

ComponentLibrary

Simulation

Model

Image source: http://www.cross-morse.co.uk/timing_belt.asp

Solution Space Explorer

using Boolean

Satisfiability

SysML Model

• Amesim component

BehaviorLibrary

• Operator & Flow

• Functional Basis

Function Library

System Boundary

TR

RR

Planetary Drive 1

R TWheels 1

RElectrical

Machine 1

Electric Junction

RCombustion

Engine

RElectrical

Machine 2

R

RR

Planetary Drive 2

System Boundary

TR

RR

Planetary Drive 1

R TWheels 1

RElectrical

Machine 1

Electric Junction

RCombustion

Engine

RElectrical

Machine 2

R

RR

Planetary Drive 2

System Boundary

TR

RR

Planetary Drive 1

R TWheels 1

RElectrical

Machine 1

Electric Junction

RCombustion

Engine

RElectrical

Machine 2

R

RR

Planetary Drive 2

System Boundary

TR

RR

Planetary Drive 1

R TWheels 1

RElectrical

Machine 1

Electric Junction

RCombustion

Engine

RElectrical

Machine 2

R

RR

Planetary Drive 2

(FBS)

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Thank you for your attention!

Benjamin KruseEngineering Design and Computing Laboratory, ETH ZurichCLA F 32.2, Tannenstrasse 3, 8092 Zurich, Switzerlandhttp://[email protected]


http://www.edac.ethz.ch/



mailto:[email protected]

1 Benjamin Kruse Libraries for Model-Based Mechatronic Concept Design in SysML Benjamin Kruse Engineering Design and Computing Laboratory, ETH Zurich.

Documents

based systems engineering

smart product engineering

mechatronic concept

evolving sysml

sysml libraries

usability of sysml

benjamin kruse2motivation

benjamin kruse5approach