Practical development
Illustrated using the GAIUS windtunnel
automation system
By: Evert van de Waal
Imtech ICT Technical Systems
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Background Imtech
Imtech
■ Imtech is a large (19.000) company
■ Focus on technical services
– Infrastructure
– Buildings, ships, communications, traffic
Imtech ICT Technical Systems
■ 70 Professionals
■ Focus on ‘technical software’
■ Customers include Shell, Vanderlande, Philips, GE
Healthcare, Rijkswaterstaat, Assembleon, NXP, etc.
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Background Evert
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MSc Electrical Engineering (1993)
Research Fellow Strathclyde University (Control)
Firmware developer small company
Consultant at Imtech TS (since 2001)
■ Focus: Architecture, Control, Firmware
■ National Champion SW Architecture Description 2007
■ URL: http://www.nkictarchitectuur.nl/2007/Downloads/inzendingen/7-ImtechGaius/Gaius_Architecture_nka.pdf
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Background GAIUS / DNW
■ DNW (German-Dutch Windtunnels) manages tunnels in
Amsterdam, Marknesse, Braunschweig, Göttingen and Cologne
■ DNW management wanted a new control system, that
– Is able to unify to look-and-feel of all tunnels
– Allows a high level of experiment automation
– Will give a competitive edge for 10 years
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NWERC 2008
22 nov 2008
Wind tunnel Structure
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Test Object
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Data Acquisition
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Presentation
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Characteristics of a wind tunnel
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Large and complex system
Most wind tunnels are unique
Constant changes and improvements
Many types of experiments are performed
Wind tunnel tests are essential for wind tunnel users
Most tunnels operate at the edge of physical
limitations
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Examples of Experiments
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Wind tunnel Characteristics:
Dutch Tunnels:
■ Amsterdam HST: High Speed: 1.3M, 2.0x1.8m, 0.25 to 4 Bar, 16MW
■ N-O Polder LLF: Large Low Speed: 80 m/s, 9.5x9.5m, 20 MW
■ N-O Polder LST: Low Speed: 80 m/s, 3x2.25m, 700KW
Auxilery systems:
■ Pressurized air: 5 kg/s at 80 Bar
■ Positioningsystems: better than 0.01 graden at 70KNm
■ Moving belt for ground effects
Data Acquisitioning:
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1000+ presure sensors
Microphone array for locating sound sources
Camera for measuring color changes in pressure sensitive paint
Laser / camera systems that track movement of oil droplets
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
A Request
■ Please, make me an automation system
■ How would you proceed???
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
SW success factors
■ What is important for a wind tunnel automation
system?
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Algoritms
Performance?
Database structure?
OO design?
Architecture?
Development process?
GUI layout?
Requirements engineering?
■ Who decides what is important???
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Actual SW success factors
■ The software must perform its main purpose well
– The user defines ‘main purpose’ and ‘well’
– Usually there are several user types: stakeholders
■ ‘well’ indicates that we are talking about nonfunctional behavior
– That is e.g. user friendliness, robustness, performance,
stability, maintainability, extendibility, testability, etc.
■ What determines non-functional behavior???
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Factors in non-functional behavior
■ Most non-functional behavior is determined by:
– Algorithms used
– Structure of software
■ Obviously, suitable algorithms need to be used
The design and architecture of SW determine
non-func behavior
■ In fact, a design is only needed to meet non-func
requirements
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Different Worlds
Customer:
· Wishes
· Sub-conscious
· Plain English
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Developers:
· Code
· Formal requirements
· Constraints
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22 nov 2008
Bridging the Gap
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Details
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10
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Architect
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107
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
An Architecure
■ An architecture bridges the gap between customer
and programmer
– Compare with civil engineering
■ Architecture concretizes customer wishes
■ Then it makes choices that will satisfy these wishes
■ An architecture logs all main choices
– including alternatives and rationale
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Architecture as a bridge
Create
Create
Principles
Verify
Verify
Choices
Decomposition
Verify
Failure
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Steps in bridging the gap
■ Start with customer wishes
■ Several steps are necessary to bridge the gap
– First, a layers of principles for evaluating choices
– Second, a layer of fundamental choices
– Finally, the decomposition a developer can use
■ Be careful to rationalize choices
– Use the principles as rationale for choices, etc
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Customer wishes
■ Focus on stakeholders and their views
■ There are several types of stakeholders:
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Internal & external
Different stakeholders for phases in product lifecycle
Actual users of the system
Those who pay for the system
Etc, etc
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
GAIUS Stakeholders
External (DNW)
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Management
Project Engineer
Test configurator
Tunnel Operator
Developer
Internal (Imtech)
– Management
– Developer
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Summary of GAIUS customer wishes
■ GAIUS is an open system, with open interfaces to which new systems
can be attached easily.
■ The data available in parts of the system is easy to share with other
parts of the system.
■ It is easy to use ‘scripts’ to automate the control and measure systems.
■ It is easy to test & improve scripts in a simulated environment, without
using the actual wind tunnel.
■ The GAIUS system is adaptable to accommodate the differences
between various wind tunnels, and also changes in a wind tunnel
system.
■ The GAIUS system is cost-effective.
■ The GAIUS system runs on readily available hardware (PC’s).
■ The GAIUS system is supported for a long period, in the order of 10
years.
■ It is possible to deploy the GAIUS system gradually, and with as little
interference with tunnel operations as possible.
■ The configuration of GAIUS is easy to read and edit.
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
GAIUS ?
GAIUS refers to Gaius Julius Ceasar, one of the most
famous dictators in history.
The ‘dictator’ (Latin for ‘someone who dictates orders’)
was innovation in the Roman republic: a special
magistrate with authority over regular magistrates. It
was the most senior magistrate.
The GAIUS software system was designed using this
philosophy.
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Some key characteristics of GAIUS
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Interconnect various sub systems
Integrates these to one coherent system
Simplifies testing by automatic test procedures
Facilitates evolutionary Change
– Adding, modifying and removing sub systems
– Changing procedures
■ Flexible enough for custom experiments
■ Safe and fault tolerant
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Architecture Principles
■ These are the key decisions in a project
– Take them with care
– Verify them with stakeholders
■ Principles originate from several sources:
– Customer wishes & other project context
– Best practices (patterns)
– You own experience & preferences
■ Be Creative!
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Principles for GAIUS
1. Use Open Source Software
(as much as possible)
■ Open and cost effective
2. Use Python
(as much as possible)
■ Proven high-productivity language, very open, portable
3. Use Industry Standards
■ Again, open & cost effective
4. Use the GAIUS Bus (=blackboard pattern)
■ Open, adaptable, best practice
5. Use a standard module interface
■ Allows scripting
Imtech ICT Technical Systems
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22 nov 2008
Additional principles
6. GUI’s are separate components
■ Easy to simulate, allows automated testing
■ Communicate with modules using GAIUS bus
■ Scripting uses same interface as GUI!
7. Communicate with HW through TCP/IP
■ Open, easy to simulate & test without tunnel
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Refinement of principles
■ Once formulated, the principles can be refined
■ Refinement is done by making choices
■ These choices undergird the principles
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Some Fundamental choices in GAIUS
■ Use of RTPS as back-bone of GAIUS bus
■ Use three different semantics in the bus
– Time-Triggered, real-time, no resend
– Event-Triggered, no resend
– Event-triggered with acknowledge for Commands
■ Use LabVIEW to create GUI’s
– Interface to the GAIUS bus
■ Modules derive from base class, which:
– Retrieves module configuration
– Enforces compliance with the state model
– Provides race-condition free event handling
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Divide and conqueror
■ Next, the architecture will partition the software
– Define modules and their interfaces
■ Thus development can be done in parallel
– Up to a certain level! (‘The mythical Man-month’)
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Main tunnel systems
■ Wind generation (‘Facility’)
■ Model positioning (Test Object Positioning And
Control, ‘TOPAC’)
– Controls all movable objects in the measurement area
■ Data Acquisition
■ Data Processing
– Derives aeronautical data from measurements
■ Safety
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Wind tunnel systems
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
A GAIUS system
GUI
Preparation
Presentation
Automated
GAS
RT data area Measurement Cycle
Integrated
Computer
Manual
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Facility
Controller
TOPAC
Data
Acquisition
Low Level
Controller
PLC
NWERC 2008
Data
Processing
Apropos
Sensor
Systems
22 nov 2008
GAS
GUI
GAIUS Bus
RTPS
TOPAC
Data Processing
Data Acquisition
Facility Control
NFS
Mass Storage
(NFS server)
Backup
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Architecture & Requirements???
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Requirements focus on functional behaviour
Architecture focuses on non-functional characteristics
Both are usually needed
However, non-func determines customer satisfaction!
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Architecture & Requirements
Acceptance
Testing
Requirements
Principles
Principles
Choices
Choices
Decomposition
Decomposition
Project
Project
Estimate
Estimate
Architecture
Architecture
Detailed
Detailed
Design
Design
Integration
Plan
Project
Project
Planning
Planning
Implementation
Implementation
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Architecture & Agile Development
■ GAIUS was an Agile project
– Cost of full requirements analysis was prohibitive
■ Even in an Agile project, you need foundations
– Architecture is the foundation of your software
■ Agile development is suicidal before architecture is
clear!
– Use prototypes to quickly finalize architecture
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Lessons learnt
■ Don’t increase team size too soon
– Architecture needs to be mature first!
■ When using Open Source, check for maturity
– Open Source RTPS implementation not sufficiently mature
– Made our own implementation in 1.5 manmonths
■ LabVIEW is not as open as advertized
– Lots of quirks and missing documentation in C interface
– Would not use it again for this purpose
■ Python offers an excellent programming platform
– Saved the day!
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008
Questions?
Imtech ICT Technical Systems
NWERC 2008
22 nov 2008