Verification of embedded system specifications
using collaborative simulation
of SysML and Simulink models
Ryo Kawahara*, Hiroaki Nakamura*, Dolev Dotan**, Andrei
Kirshin**, Takashi Sakairi*, Shinichi Hirose*, Kohichi Ono*,
Hiroshi Ishikawa*
*Tokyo Research Laboratory, IBM Research
**Haifa Research Laboratory, IBM Research
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Abstract
 The authors propose an extension of SysML
which enables description of continuous-time
behavior.
 The authors also develop its execution tool
integrated on Eclipse-based platform by
exploiting co-simulation of SysML and MATLAB /
Simulink.
 To demonstrate the effectiveness of the tool and
the extension to SysML in verifying
specifications of an embedded system, we
create a sample model and analyze its execution
results by checking constraints under a test case.
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Introduction
 In the development of an embedded system, it is
important to verify that the specification of the
system satisfies the requirements at an early
stage
– One approach to achieve this is to model and
simulate the system during the analysis
– Systems Modeling Language (SysML) is an
extension of UML for embedded systems to include
heterogeneous elements such as software,
electronics, or mechanics
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Subject
 Embedded systems often include control systems
– A control system is usually a hybrid system, the
mixture of continuous-time and discrete behavior
– Continuous-time behavior in UML / SysML has not
been defined
– Simulation of control system is usually done in a specialized
tools, such as the MathWorks MATLAB / Simulink
– A UML / SysML behavior is not associated with time
 Integration of the continuous-time behavior into
the systems model is desired
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Background: SysML
 SysML is an extension of UML2 for systems engineering
Requirements
–Requirement diagram
Behaviors
–Activity diagram
–State machine diagram
Structures
–Block definition diagram
=> class diagram
Parametrics
–Parametric diagram
=> internal block diagram
–Internal block diagram
=> composite structure diagram
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Background: Simulink
 Simulink uses Block diagram
– Block diagram describes the flow of signal
between blocks, which process the signal
– This example calculates:
t
f Out1(t )   2 f In1( )d
0
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Approach
 Use SysML for a system architecture description
 Use specific languages for each domain
– Simulink for continuous-time behavior in a control
system
 Time duration assignment to SysML action
 Verify specification by collaborative simulation
– Run multiple simulation in parallel with time
synchronization
– Independent time management module
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Extended Modeling for
Simulation in SysML
Time assignment to
action
Continuous data
exchange between
blocks
MARTE <<GaStep>> SysML flow ports with
stereotype, or sleep() connectors in internal
method in action code block diagram
Specifying Simulink
model as a block
behavior
<<externalModel>>
stereotype to specify
model file
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
SysML Execution and Debugging

Debugging of behavioral UML models by emulation, supporting:
-
Class, Composite Structure Diagrams
State Machines, Activities
Java as Action Language

Extensible to support UML profiles (in this case SysML)


Debugging UI – Model Debugging Perspective (next slide)
Diagram animation


Debugging modes:
Traditional Debugging
-

Running
Transition
Start “main”
Run to breakpoint
Stepping
Interactive debugging
(model “exerciser”)
-
Execution
Pending
Manually create objects
Invoke operations
Send signals
Current
State
Breakpoint
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Model Debugging Perspective
Breakpoints
Debug
Variables
Diagram
Animation
Console
Sleeping
Event Pools
Watch
Instances
Signals
Snippet
I/O
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Sleeping View
Shows the queue of sleeping behaviors and behavior elements.
Current virtual time
Wakeup time
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Time Management
 Data is exchanged and the next Simulink step is
executed at:
– End of timed SysML behavioral step (<<GaStep>> or sleep())
– Periodic data exchange event
Discrete events
Action2
Action1
SysML
object
Action3
SysML
object
…
Demands of time
Add periodic data exchange events into
the list consists of the discrete events
Periodic data exchange events
SysML
object
MATLAB / Simulink
Simulation start / stop
MATLAB / Simulink command
execution
Time demands to scheduler
Time management module
Time
0
100
200
300
400
Timed scheduler
UML execution engine
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Co-simulation with Simulink
 All the Simulink models are referred from a
single temporary Simulink model
– Only one Simulink process is used
 Simulation data is sent or received through
Input/Output S-Functions
Temporary generated Simulink model
Input
S-Function
Model
reference1
Model
reference2
Output
S-Function
Data from SysML
Model 1
Data to SysML
Model 2
Simulink models which are assigned to
SysML behaviors
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Overview of Sample model: Humidifier
 Basic mechanism
– The water is boiled by the heater
Circulator
fan
– Vapor is emitted to the
environment by circulator fan
 Requirements
Pan
Heater
Reservoir
– The humidifier starts vapor emission within 5 minutes
since the power on signal
– The humidifier ends cool down within 10 minutes since
the power off signal
– The humidifier keeps the room humidity at a constant
level specified by the user automatically
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Structure of HumidifierSystem
Internal block diagram
of HumidifierSystem
Block
definition
diagram
Flow ports for
continuous I/O
Simulink model
assigned block
State machine
assigned block
State machine
assigned block
Standard ports for
discrete signals
Simulink model
assigned block
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Behavior of Control block
State machine
diagram
Signal from
user interface
Change event that
monitors values from a
Simulink blocks
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Simulink model for
VaporGenerationPlant
heating subsystem
radiation subsystem
evaporation subsystem
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Test context
Block
definition
diagram
Internal block diagram
of TestContext
Definition of test
environment
Simulink model
assigned block
Flow ports for
continuous I/O to consist
a closed loop
Test target
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Test case and results
Time(s)
Command
0
Test start
10
Power on
2000
Power off
3600
Test end
Cooling down taking too
long time
Automatic
humidity
control
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Parametric and time constraint
evaluation
Parametric diagram
Constraint block:
Humidity should be kept
near target value
Sequence diagram with time constraint
using MARTE profile
Timed constraint:
Cool down should be finished
within 10 minutes
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Conclusion
 We have developed a verification tool based on
co-simulation of Simulink and SysML
 We have extended the modeling capability of
SysML to be able to reference Simulink models
and specify timed behavior
 These extensions enable one to test
specifications of a system which includes
continuous-time behavior in a closed control loop
© 2009 IBM Corporation
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Overview of the verification tool
TPTP-based
test driver
Time-aware UML
execution engine
Timed test cases
Timed discrete behavior
Simulink
Continuous behavior
Virtual time scheduler
Binary tree for fast eval.
<x,y,z>
{a,b,c}
Time constraints
|{d,e,(f|g}} {h,i}
(OMG MARTE profile)
Eval > 80
eval
Parametric constraints
(OMG SysML)
Integer eval
Block2
p
eval
Integer b = 1
eval = f(bb, cc)
bb
Block3
Integer c = 2
{j,k}
q
l
p
q
m
{n,o}
cc
Parametric constraint evaluator
Time constraint evaluator
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Simulink model for Room block
relative_humidity subsystem
saturation_vapor_pressure subsystem
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
State machine diagram of
HeaterControl block
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Related works
Studies on coupling of UML/SysML and continuous-time simulation (e.g., Simulink)
Coupling
method
Reichmann et al.
(2004),
Telelogic
Rhapsody®
C. Nytsch-Geusen Hooman et al. Our
(2007),
(2004)
approach
A. Pop et al.,
(2007),
T. A. Johnson et al.,
(2008)
Conversion to
source code
Conversion to
Modelica
Cosimulation of
Simulink and
Rose® RT
Cosimulation
By Modelica
By Simulink
By
independent
module
Simulation
By independent
time
module
management (Rhapsody)
© 2009 IBM Corporation
Haifa Research Lab – Model Driven Engineering Technologies Group
Related works
 Source code level linkage of UML and Simulink
– Reichmann et al., 2004. Telelogic Rhapsody®
 Co-simulation of Simulink and UML model on
IBM Rational Rose® RealTime
– J. Hooman, N. Mulyar and L. Posta, 2004
 Conversion of UML/SysML to Modelica language
– C. Nytsch-Geusen, 2007. A. Pop et al., 2007. T. A. Johnson et
al., 2008
– Modelica is a new language to model continuous-time
system
© 2009 IBM Corporation