verhaert innovation day 2011 – koenraad rombaut & michiel de paepe (verhaert) - model based...
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CONFIDENTIAL
26.10.2012 Slide 1
CONFIDENTIAL
Model Based Design for Embedded Control Systems
Koenraad Rombaut
Coordinator applied physics & systems
Koenraad.rombaut@verhaert.com
Michiel De Paepe
Consultant applied physics & systems
Michiel.depaepe@verhaert.com
CONFIDENTIAL
26.10.2012 Slide 2
Model Based Design in general:
• What ?
• Why ?
• How ?
A model based design case study:
• Case study
• Models
• Conclusions & demonstration
Content
CONFIDENTIAL
26.10.2012 Slide 3
What ? Model driven engineering ?
Model based development ?
Build model Plant / Process
Product design
Design Concepts
Verification
Implement Product code
Testing
Mo
del s
pace
C
od
e s
pace
Model = system + control + environment + stimuli
Multi-domain = control + system behaviour
Coupling / transformations models design
requirements design implementation test scenario
CONFIDENTIAL
26.10.2012 Slide 4
Why ?
Why ?
• Cheaper & faster
• Higher reliability
• Better definition
When ?
• Complex processes / designs Complex control strategies
• High reliability
• Early validation
• Fast developments
• Changing requirements
Outputs:
• design inputs
• insights
• derisk
CONFIDENTIAL
26.10.2012 Slide 5
Why : definition
Communication
between disciplines,
with customer & subcontractors,
over project phases
Re-use of subsystems
Safety factor for (sw) budget &
schedule
Needs Requirements Specs Design Implementation Documentation
Needs (what do we want) vs.
specifications (how do we define)
Specifying new (innovating) products
and subsystems
Changing requirements
CONFIDENTIAL
26.10.2012 Slide 6
Why simulation : early validation
Benefits
• More and faster iterations
• Parallel hw & sw development
• Multiple off-nominal and fault
testing (non feasible tests)
• Early full system validation
and risk mitigation without hw
• Less real-life testing
(= the poor man’s approach)
• More optimal system design
by sw-physics co-simulation
• Improved communication &
design specification
=> time & cost reduction
Traditional:
• sequential = lengthy
• validation on hw = late
Model based:
• Parallel = fast
• validation on model = early
Device
Requirements
System
Design
Subsystem
requirements
Detailled
Design
Functional
Test
Component
Test
Device
Validation
System
Verfication
CONFIDENTIAL
26.10.2012 Slide 7
Why early: cost vs. freedom
• Design & test
freedom
• Unlimited
measurements
in simulation
• Lots of risks
• Cost (project,
build,
measurement,
change)
• Real world
representation
• Number of
people
involved
Lab
model
Field
model Virtual
model
Ris
k / E
ffo
rt
Time
CONFIDENTIAL
26.10.2012 Slide 8
Re-use proven tools from high reliability
domains?
• Space, aeronautics, nuclear, automotive,
chemical plants
• Domain specific tools
• Tool cost not an issue
• Long learning curve, less flexibility
Need for a new toolchain
• affordable
• flexible, scalable
for generic developments
• easy learning (graphical ?)
• open (no vendor lock-in)
• automatic transformations
How ?
CONFIDENTIAL
26.10.2012 Slide 9
How: examples
Multi domain tools:
• Matlab/Simulink +
SimMech+StateFlow
+ RTW + AutoSar
• Dymola / Modelica
• LabView
• SysML / Raphsody
Some research projects
• Modelisar: Modelica +
Autosar
• Destecs: co-sim CT + DE
• Deploy: B for dependable
sw
CONFIDENTIAL
26.10.2012 Slide 10
How : Modelisar / Autosar ?
Application sw
Hardware
standardized
HW-specific
Customer needs
Adaptive Cruise Control
Lane Departure
Warning
Advanced Front
Lighting System
Using standards
Communication Stack
OSEK
Diagnostics
CAN, FlexRay
Autosar =
Automotive
hw interface
Modelica =
Plant modelling
CONFIDENTIAL
26.10.2012 Slide 11
Case study : excavator with Destecs
Complex
• manual operations
• => inherent fault tolerant design
• 3D dynamic motion, digging map & boundaries
• unknown soil conditions
• multidomain: hydraulics, mechanics, sw
Well known case
• Manual operator as a reference
• Scalable & testable
Destecs differentiators:
• discrete event (sw) & continuous time (physics)
• fault injection & error checking
• open
CONFIDENTIAL
26.10.2012 Slide 12
Model Based Design in general:
• What ?
• Why ?
• How ?
A model based design case study:
• Case study introduction
• Models
• Scale model
• Continuous time model
• Discrete event model
• Conclusions & demonstration
Content
CONFIDENTIAL
26.10.2012 Slide 13
DESTECS inspiration
• Inspiration
• Use collaborative multidisciplinary design of Embedded Systems
• Rapid construction and evaluation of system models
• Evaluated on industrial applications
• Need because of Embedded Systems
• More demanding functional & non-functional requirements
• Reliability, Fault Tolerance
• Increasingly distributed
• More design possibilities, and faults
• Communication between physics and control
CONFIDENTIAL
26.10.2012 Slide 14
DESTECS approach
• Methods and Open tools
• Model-based approach for collaborative design of ECS
• Co-simulation
• Different tools, reflecting relevant aspects of design
• Rapid, consistent analysis & comparison of models
• Advances needed in
• Continuous time modeling
• Discrete event modeling
• Fault modeling and fault tolerance
• Open tool frameworks
CONFIDENTIAL
26.10.2012 Slide 15
Dredging
• Dredging
= Underwater excavation
• No visual
• Introducing semi automated control
CONFIDENTIAL
26.10.2012 Slide 16
Scale model
CONFIDENTIAL
26.10.2012 Slide 17
Actuators
Full scale Hydraulic pistons
vs.
Scale model Electric linear actuators
12V full speed out
0V no movement
-12V full speed retract
CONFIDENTIAL
26.10.2012 Slide 18
Sensors
Incremental encoders
2 shifted square waves
Step and direction information
Driving step counter (up and down)
1 index pulse / revolution
Absolute positioning
CONFIDENTIAL
26.10.2012 Slide 19
Continuous Time model
CONFIDENTIAL
26.10.2012 Slide 20
3D Model
• STL-files for visualisation
• Mass & Inertia
• Dimmensions
CONFIDENTIAL
26.10.2012 Slide 21
Discrete Event model
CONFIDENTIAL
26.10.2012 Slide 22
Excavator model
CONFIDENTIAL
26.10.2012 Slide 23
Operator
• Joystick inputs (from CSV files)
• Pressing buttons
• Power on
• Start/Stop
• Manual/Assisted mode
CONFIDENTIAL
26.10.2012 Slide 24
Safety unit
• Redundant system
• In normal circumstances, no action
• Overrules controller at controller failure Software bug,
unforeseen situation,
hardware failure
• If triggered, 3 actions: Trigger emergency state on controller
Overrule output and thereby stop all motion
Cut off power to the motors (unimplemented, slows down CT)
CONFIDENTIAL
26.10.2012 Slide 25
Controller
CONFIDENTIAL
26.10.2012 Slide 26
Operation modes
Direct mode Assisted mode
CONFIDENTIAL
26.10.2012 Slide 27
Assisted mode
Boom encoder
Stick encoder
Bucket encoder
X-joystick
Y-joystick
Scoop-joystick
Kinematics Inverse
kinematics
Angular velocities:
Boom, Stick,
Bucket
Actuator velocities:
Boom, Stick,
Bucket Boom linear actuator
Stick linear actuator
Bucket linear actuator
CONFIDENTIAL
26.10.2012 Slide 28
Conclusions
• Ability to implement large level of complexity at both sides:
Physics and Controller
• Currently it’s an academic tool, not mature.
• Steep learning curve, only for large and complex projects
CONFIDENTIAL
26.10.2012 Slide 29
Excavator : current practice
Mechanics
• 3D CAD
System design
• requirements doc
• architecture doc
• design specs doc
Electronics
• schematic
Hydraulics
• 1D model
control sw
• C-code
Detailed design
Build &
Integration
Final product
• Test & verification
sensor
actuator
CONFIDENTIAL
26.10.2012 Slide 30
20sim
• continuous time
• multi-disciplinary
• graphical
• open libraries with
validated components
• from high level to detailed
Co-Sim IF
• version tracking
• co-sim solver
• design space exploration
• fault injection
VDM++
• discrete event
• inherent condition checking
• formal
• graphical (via UML)
• support for sw methods
• C-code generation
Excavator : with DESTECS
CONFIDENTIAL
26.10.2012 Slide 31
CONFIDENTIAL
Time for a demonstration
CONFIDENTIAL
26.10.2012 Slide 32
Any questions?
CONFIDENTIAL
26.10.2012 Slide 33
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More at www.verhaert.com
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