software is not the only fruit -...

SWISSED 2017Copyright © 2017 Colin Hood Systems Engineering Ltd

Software is not the only Fruit

Modelling Mechatronic Systems

Colin Hood Systems Engineering Ltd4 Summerhouse RoadNorthampton NN3 6BJGreat Britain

[email protected]

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Aims

▪ To discuss modelling, its history, and its applicability to many domains of

systems engineering

Copyright © 2017 Colin Hood Systems Engineering Ltd

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Use of Modelling

Modelling can help to:

i. understand what is required

ii. to explain what has been understood to promote a common

understanding

iii. to plan the implementation of a solution by creating a design

iv. enable checking a specification for consistency and other quality criteria

v. to support simulation and prediction, or

vi. to generate implementation directly from a model, by abstracting reality to

enable concentration on the matter interest


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Modelling in the 1970‘s


Source:

https://www.indiamart.com/svpservices/cad-draughtsman.html

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Modelling Mechanical Parts

• From orthogonal views the

whole part is specified


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1

1

On

Ladder Logic


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1

1

1

On

Ladder Logic


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1

1

1

On Off

Ladder Logic


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1

1

1

On 2

Ladder Logic


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1

1

1

On 2

3

Ladder Logic


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On

Digital Logic Gates


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On

Off

Digital Logic Gates


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On

Off

3

Digital Logic Gates


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On

3

2

Digital Logic Gates


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▪ The light will be on if

the on button is pressed


the on button is pressed or the light is on


(the on button is pressed or the light is on)

and the off button is not pressed


(the on button is pressed or the light is on or signal 3 is true)

and signal 2 is not true

Pseudo Code


• Not all modelling is graphical

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▪ In the 1980‘s it became popular to program industrially hardened

computers known as Programmable Logic Controllers (PLCs) using

ladder logic, as if designing a control system made of relays.

▪ This step forward combined modelling skills from the past 30 years with

modern technology for a modern solution.

▪ This was an easy step for some people changing from relays to

computer control,

BUT

it limited some people to continue to think in 30 year old solutions and

not to explore new possibilities.

Progression from Relays to Computers


• Automatic implementation from a specification

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Speed Control

Start Motor button pressed

Running speed reachedStop Motor button pressed

Speed = 0

Stop Motor

button pressed

Idle

Start MotorShutdown

• Decomposition based upon

objects,

functionality, or

sequence

Decomposition: DFD and STD


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<<Block>>

LightController

Switch

light on

[else]

[else]

[ON button

pressed][light is on]

lightStatus

ON button

lightStatus

Act LightController• SysML intended to

specify systems

• but….

is mainly used for SW

Systems Modeling Language (SysML)


Switch

light off

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• Using SysML to specify mechanical properties

Sketch and Port-Model


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▪ We see that modelling has been used throughout history, and remains

applicable to many domains of systems engineering

▪ Our experience should not limit us.

Learning from the past allows us to make progress more quickly than

re-inventing everything

Conclusions


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Colin Hood Systems Engineering Limited

Evans Business Centre

Regents Pavilion

4 Summerhouse Road

Northampton NN3 6BJ – UK

[email protected]

Systems Engineering since 1985

Founding Board Member of IREB 2006

(International Requirements Engineering Board)

INCOSE member since 1991


www.munich-openspace.de

Save the date: 22 – 24 February 2018 in Munich

http://www.certified-re.de/

http://www.munich-openspace.de/

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