Deterministic Ethernet: Addressing the Challenges of ......3rd Workshop on Safety and Security of...

3rd Workshop on Safety and Security of Intelligent Vehicles (SSIV 2017)

Deterministic Ethernet: Addressing the Challenges of Asynchronous Sensing in Sensor Fusion Systems

Date: 2017.06.25

Ayhan Mehmed

[email protected]

Sasikumar PunnekkatMDH Västerås, Sweden

[email protected]

Wilfried SteinerTTTech Computertechnik AG

[email protected] Computertechnik AG

Outline

• Advanced Driver Assistance Systems (ADAS)

• Problem definition

• Understanding the OOSM problem

• Methods for measurement timestamping

• The use of deterministic Ethernet networks

for precise timestamping

• Results

• Conclusions and future work2

Outline


3

ADAS Introduction

4

Informing Warning

Controlling

Sensor fusion

5

Sensing:• Long and Short Range Radars

• Ultrasonic sensors

• LiDARs

• Mono and Stereo Cameras

Ego-vehicle sensors• Gyro, accelerometer

• Wheel speed sensors

• Steering angle sensor

• GPS

Virtual sensors:• Digital maps

• Wireless communication

Se

nso

r fusio

n

Outline



7

Performance of sensor fusion

systems

8

Quality of the input data

Efficiency of the fusion algorithm

• Average number of missed targets,

• Average number of extra targets and etc..

Improvement and quality assessment of the input data:

• Specifically the degree in confidence in terms of attributes

such as reliability and credibility

Rate at which the data is provided to the fusion system:

• Rate of the sensors (measurement cycle)

• Quality of the communication link (latency, jitter)

Neglect OOSM Perf. Decrease

Outline



• Understanding OOSM problem

9

Open questions

10

HOW DOES THEOOSM

EFFECTS THE SENSOR FUSION SYSTEM?

Kalman filter

HOW DOES THEOOSM OCCUR?

The Kalman Filter

11

THE BEST ESTIMATEWE CAN MAKE OF

THE LOCATION OF AN OBJECTIS PROVIDED BY COMBINING OUR

KNOWLEDGE FROM THE PREDICTIONAND THE MEASUREMENT

An optimal recursive data processing algorithm, that computes the best

estimate of the current target state, based on the preceding target state

estimate, the current measurement and the control input (ut).

The Kalman Filter

12

1

2

3

Application of Kalman filter for

multiple sensors

13

The occurrence of OOSM

14

• Differing measurement latency times

• Asynchronous sensing

The effect of OOSM

15

NTMO

The amount of the error

introduced by NTMU

16

Size of NTMU The Kalman gain Velocity

Constant speedConstant K=1

Error introduced by the NTMU

Handling the OOSM

17

Single-lag and multi-lag OOSM

Sophisticated algorithms Simple algorithms

Buffering algorithm

Assumption

Precise timestamp

Not valid

Lack of SWRC

Chronological order

Not guaranteed

NTMU

InevitableOOSM

The amount of the error introduced

by imprecise measurement

18

130 Km/h

Vehicle speed

Error <= 20cm

Objective

Size of NTMU

Error of the timestamp

Error introduced by

Outline





19

Timestamping data at arrival

(Centralized method)

20

Measurement cycle time

Measurement transf. time

Measurement latency. time Error of the timestamp

Precision of the cycle time

Communication jitter

Triggering method

21

Trigger latency. time

Trigger transfer latency

Activation latency


Communication jitter

Constant trigger lat. time

Timestamping at the time of

acquisition (distributed method)

22

Measurement with

timestamp

Sensors

No cycle times

Benefit

No transfer times

Global time

Difficulty

Needed

Global sync. mechanism

Precision of the sensor

internal clock with respect

to UTC time.

Precision of the timestamp


Outline







23

What do we target

24

Distributed app.Centralized approach Triggering app.

• Ensure a system-wide synchronized time

• Low jitter data transmission

Communication standards

Standard Ethernet

IEEE 802.1AS

+

SAE AS6802Sync accuracy 1 µs

IEEE 802.1Qav Jitter ~10 – 100 µs

IEEE 802.1Qbv Jitter 1 µs

AV

BT

SN

Jitter 1 µs +

Sync accuracy 1 µs

Suitability of the standards for

achieving precise timestamps

25

• Traffic class

• The data that is transmitted

• Maximum communication jitter(Numbers taken from simulation based

performance comparisons)

Standards and their spec.

Assumed to be achieved with:

• Centralized, triggering or

distributed approach.

• If one or more comm. Standards

are used.

Timestamp precision

Outline







• Results

26

Error introduced by the

timestamp precision

27

Outline







• Results

• Conclusions and future work28

Conclusions

29

Objectives of our research

Study the benefits of different communications standards for the

application area of sensor fusion systems..

Prerequisites

1. Understanding the Kalman filter

2. The cause of OOSM and how they affects the Kalman filter

3. How the absence of precise measurement timestamp leads to

NTMU, same as the caused by the OOSM,

4. And finally investigate the methods for sensor measurement

timestamping and formulate their precision

Based on this knowledge

• We were able to show that communication standards can

contribute for solving the problem of NTMU.

• By minimizing the error introduced to the optimal state estimate

down to the range from 0 to less than 0,5cm depending on the

timestamping methods and the communication standards used.

Future work

30

Optimistic results

consequence of idealized conditions and communication

Specifications.

Verification

Simulation based studies to verify the correctness of the theoretical

assumptions made in this paper.

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Thank You for

Your Attention!

Timestamping data at arrival

(Centralized method)

32

Measurement cycle time

Measurement transf. time

Measurement latency. time

Drawback of current solutions

33

• Assume a timestamp with precise timestamp

• Not valid: due to the lack of system wide-reference

clock.

Deterministic sensor data acquisition

34

• Deterministic Behavior

A system exhibits a deterministic behavior when the performance measures of its services are

predicable under a number of conditions and characterized by specific nonrandom equations

• Context of in-vehicle networks

The most important performance measure is message latency

• Context of multi-sensor data

Result of non-deterministic message latency are multi-sensor data fusion systems are the out-of-

sequence measurements.

• Solution

• Exploring the features of different real-time network technologies:

• TTEtthernet,

• AVB,

• TSM

• Explore their ability of achieving deterministic behavior in the process of acquisition of sensory

data from different ADAS sensors

• Abilities:

• Tightly synchronize the data acquisition from multiple cameras, LiDARs, LRR and SRR

• Provide a “time-stamp” for each measurement

Summary Timeline Sensor Fusion LayerStudies Deterministic SDA

The Kalman Filter

35

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Deterministic Ethernet: Addressing the Challenges of ......3rd Workshop on Safety and Security of...

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