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Simulation Based Automotive Communication Design using MATLAB- SimEvent
1
Sudhakaran M Anand H General Motors
MATLAB Expo 2013
Agenda
• Introduction
• Different Analysis Methods
• Analytical vs. Simulation Approach
• Why and when to use Simulation Based Approach
• Use cases
• Q&A
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ABS: Antilock Brake System ACC: Adaptive Cruise Control BCM: Body Control Module DoD: Displacement On Demand ECS: Electronics, Controls, and Software
EGR: Exhaust Gas Recirculation. GDI: Gas Direct Injection OBD: Onboard Diagnostics TCC: Torque Converter Clutch PT: Powertrain
Value
from
Elect
ronics
& So
ftware
Hybrid PT
Electric Ignition
ACC
Rear Vision
Passive Entry
Side Airbags
Fuel Cell
X-By-Wire
…
OnStar
OBD II
HI Spd Data
Rear aud/vid
CDs
BCM
ABS
TCC
EGR
Electric Fan
Head Airbags ...
Electric Brake
DoD
GDI
…
…
…
… …
…
1970s 1980s 1990s 2000s 2010s 2020s
Evolution of Electronics and Software Functionality
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Exponential Increase in Bus Bandwidth Capacity
Caveat: This is assuming that the same architectural pattern is maintained in the future.
Available Bus Capacity
0
2
4
6
8
10
12
14
16
2000 2005 2010 2015 2020
year
To
tal
Ne
two
rk
Ba
nd
wid
th (
Mb
ps
)
.
.
Known Data
Forecasted Data
4
Emerging Technical Challenges
• Exponential increase in communication bus and computing processor requirements • Broadcast communication and synchronization • Increase in supervisory control layers and distributed closed loop control • Heterogeneity in transmit models
• Move from 1 function – 1 ECU paradigm to up-integration of functions • Reduce No of ECUs
• Move from fail safe towards fail operational • Active Front steering to Steer by Wire • Federated vs. integrated fault tolerant devices
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Architectural Patterns • Some of the potential network architectural patterns
• Isolated Backbone •Use a public bus as a high speed, high bandwidth means to share data between domain gateway modules and support some modules directly
• Utilized Backbone •Use a public bus as a high speed, high bandwidth means to share data between domain gateway modules
P/T BODY INF/TEL
Info
tainm
ent
CH
CA
N
Bo
dy C
AN
Safety
PT C
AN
LIN
DLC
LIN
CHASSIS
Ch
assis
P/T BODY INF/TEL
Info
tainm
ent
CH
CA
N
Bo
dy C
AN
Safety CA
N
PT C
AN
LIN
Public Bus DLC
LIN LIN
CHASSIS SAFETY
• Router •Use a router as a means to share data between domain busses
Info
tainm
ent
CH
CA
N
Bo
dy C
AN
Safety CA
N
PT C
AN
LIN
DLC
LIN LIN
Router P/T BODY INF/TEL
Info
tainm
ent
CH
CA
N
Bo
dy C
AN
PT C
AN
LIN DLC
LIN
CHASSIS SAFETY
• Grid •Use Multiple Buses to contend with needed bandwidth.
• Linear •Single CAN bus. Features are added as needed as new modules, or integrated into existing modules.
P/T BODY INF/TEL
LIN DLC
LIN
EBCM SDM
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Complexity in satisfying the architectural needs
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0
1
2
3
4
5
6
Low Infrastructure Cost
Expandability
Flexibility
Low Cost to Add Features
Safety
Energy Efficiency
Domain IsolationTiming - Latency
Packaging
Re-use
Timing - Jitter
Complexity
Maintainability/serviceability
Mid Content
Isolated Backbone
Requirement exceeds capability
Capability exceeds requirement
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Question?
What methods and tools will assist the system architect to come up with an architecture that meets these challenges?
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System level performance analysis
Analytical approach “ Mathematically represent the
system for worst case and best case scenario for a given design”
Simulation approach
“ Simulates the system for a given scenario and is time based to predict best
design”
Analysis Methods
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Best case
model
Upper Bound Worst case
model
Lower Bound
T analytical
Simulation Vs Analytical
Implementation Simulation Analytical
Treal Tsim
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Metrics
Metric\Approach Analytical Simulation
Latency Y (Worst case) Y (Average)
Load (CPU or Network)
Y (Worst case) Y (Average)
Buffer Management
Y (Worst case) Y (Average)
Jitter N Y
Initialization Time
N Y
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Why Simulation Approach
• Study the behavior of a system without building the real system.
• Find un-expected phenomenon, behavior of the system.
• Easy to perform ''What-If'' analysis.
• Simulations take the building/rebuilding phase out of the loop by using the model already created in the design phase
• Simulation testing is cheaper and faster can be done at very early stage of development
• Simulators can be used as an effective means for teaching or demonstrating concepts of a real system.
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SimEvent Toolbox Library set
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• SimEvents provides a discrete-event simulation engine and component library for Simulink
• Enables modeling event-driven communication between components to analyze and optimize end-to-end latencies, throughput, packet loss, and other performance characteristics
• It has Libraries of predefined blocks, such as queues, servers, and switches, which enables to accurately represent actual system
• SimEvents can design distributed control systems, hardware architectures, sensor and communication networks etc…
Introduction to CAN Protocol
• CAN bus (Controller Area Network) is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer.
• CAN features an automatic arbitration-free transmission. A CAN message that is transmitted with highest priority will succeed, and the node transmitting the lower priority message will sense this and back off and wait.
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CAN Frame Format
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CAN Network Simulation Model
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Bus load vs Time
Time in (ms)
Load
17
CAN ID vs Time C
AN
ID
Time 18
Histogram if Inter- arrival Time of a Message
Time in (ms)
No
of
occ
urr
ence
s
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Conclusions
• Simulation based approach can help us in verifying the design without actually building it.
• It can be used to re-create field issues including boundary conditions, which is not possible using analytical method.
• Many design alternatives can easily be compared.
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