Simulation Based Automotive Communication Design using MATLAB- SimEvent

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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

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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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