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Autonomous Parallel ParkingAlex Braun & Sergey Katsev

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Overview

• Objectives• User Interface• Algorithms• Utilized Hardware• Hardware Design• Current Status

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Objectives/Performance Specs

•Follow a reflective track•Receive user commands over a wireless interface•Leave track and parallel park•Leave parking space and reacquire track

•Minimum parking space 2 car lengths•Travel speed .5 – 1 foot per second•Capable of following any turns greater than vehicle turning radius

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Implementation•Vehicle:

–1:12 Scale model of a Lincoln Navigator–Chassis and drive motor from original RC car–Steering implemented with Futaba S3003 Servo motor

•Power–9.6V rechargeable NiCad battery pack–Voltage regulators used to provide 5V power to electronics and isolate power planes

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User Interface

•Remote control used to issue user commands•Vehicle responds with actions and LED status lights•Remote uses 9V battery

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User Interface• Status lights will indicate:

– Current operating mode:•Manual•Automatic

– Looking for track– Following track– Looking for Space– Parking– Parked

•Error

– Waiting for user parking override•“Turn Signal”

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Sensor Layout•IR arrows show direction of beam

•Wireless interface used for remote control user commands (more later)

C1

C3

FRONT OF VEHICLE

REAR OF VEHICLE

T1 T2 T3

T4 T5

C2

C4

S1

Wireless

Analog IRsensor

Digital IRSensor

IR TrackSensor

RF Wireless

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Algorithms – Track Following

•Front sensors used to determine when to turn•Two turning angles•Rear sensors used when acquiring the track and as a backup if all front sensors are lost

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Algorithms – Track FollowingAll five track sensors are on track.

Moveforward

Scan FrontSensors

Turn 10 degreesaway from lost

sensor

Turn 20 degreesaway from lost

sensor

Two on track

Oneon track

Noneon track

Reverse, setvehicle to low

speed

Scan RearSensors

At least one on track

Noneon track

ERROR

Set vehicle tohigh speed

All threeon track

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Algorithms – Parking •Minimum parking spot size 2 car lengths•Algorithm iterates if can not fit in spot in one motion

B4

B2

FRONT

BACK

B4

B2FR O N T

B A C K

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Begin ParkingAlgorithm

Turn wheels max.towards curb

Reverse

Rear curb?

Stop, turn wheelsmax. away from

curb

No

Reverse

Check RearMiddle Vehicle

Collision

Monitor RearCurb

Detection

No

Check FrontCurb

Detection

No

No

ParkedSuccessfully

Reverse at halfspeed

Yes

Curb equaldistances?

Yes

No

Yes

Algorithms – Parking(Basic Algorithm)

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Algorithms – Parking Space Exit

Reverse

Detect RearObstacle

Has maximumbackup distancebeen reached?

No

No

Stop, Turnwheels away

from curb.

Yes

Yes

PullForward

Detect FrontCorner

Collision

Detect Track (FrontTrack Sensor Return)

No

No

Successfully ExitedParking Space

Yes

Turn WheelsTowards Curb

Yes

DetectCurb

Yes

Back Up

No

Begin ExitingParking Space

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Utilized Hardware

•Processing:–Onboard HCS12

•Sensors–Track Sensors

•Fairchild QRE00034 Infrared Reflective Sensor•Used with a comparator to provided digital input to the HCS12

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Utilized Hardware

– Speed Sensor•Fairchild QRE00034 Infrared Reflective

Sensor•Used with a comparator and a shaft

encoder to produce a timer interrupt every quarter revolution of the rear wheels

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Utilized Hardware

•Collision Detection–Sharp GP2D120 Infrared Distance Sensors–Analog value fed to HCS12 through ADC

•Parking Space Detection

–Sharp GP2D150A Infrared Distance Sensor–Provides digital detection at ~15cm

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Component Estimated Maximum Power Consumption

DC Motor 2.7W

Servo Motor 2W

Curb and Vehicle Collision Sensors 0.30W x 4 = 1.2W

Parking Space Sensor 0.30W

Track Sensors .2W x 5 = 1W

Vehicle Speed Sensor .2W

Wireless Receiver 164mW

HC-12 1W

Misc ICs and LEDs ~ .2W x 10 = 2W

TOTAL 10.6W

Power Consumption

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Hardware

•Ribbon cable used to connect HC12 to PCBs•PCBs stacked to maximize available board space•Final product will (hopefully) fit inside original vehicle cover

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Hardware – Drive Electronics

•Motor draws 1.6A max.•Texas Instruments SN754410 Quad Half H-Bridge used.•1A sustained load capacity, 2A peak load (per half H-bridge)•Two H-bridges used in parallel H-bridge functional schematic

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Hardware – Wireless Interface

•Ming 4-bit Tx/Rx•300MHz AM•Uses Holtek Encoder and Decoder chips•Remote contains 74LS922 Key matrix decoder with debounce protection

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Hardware – Sensor Input Conditioning

•Two quad binary comparator circuits•Threshold set at 4.0V, established experimentally•Separate voltage regulator•Will contain HC12 inputs for all digital sensors

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Costs

Component Retail Price Actual Price

Vehicle Assembly $50 $50

Track Sensors (5 total) $3.25 $0

Collision Detection (4 total) $48.80 $48.80

Parking Space Detection $13.23 $13.23

Wireless Kit $30.00 $30.00

Servomotor $9.80 $0

H-Bridge $1.35 $0

HCS12 $160 $0

Misc $70 $50

TOTAL $386.03 $192.03

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Current Vehicle Status

8/17/2004 8/24/2004 8/31/2004 9/7/2004 9/14/2004 9/21/2004 9/28/2004 10/5/2004 10/12/2004 10/19/2004 10/26/2004

Major system design - AB SK

Determine and acquire components - AB SK

Build vehicle assembly - SK

Interface track sensors w ith microcontroller - AB SK

Interfacing microcontroller w ith vehicle - AB SK

Track tracking - AB

Speed controller - AB SK

Track re-acquisition - AB SK

Parking space detection - AB

Interface collision sensors w ith microcontroller - AB SK

Parking algorithm - AB

User Interface - SK

Testing/Debugging - AB SK

Project Write-up - AB SK

Project Website - AB SK

Completed Remaining

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Current Vehicle Status

Front Track Sensors

Comparators HCS12 H-Bridge

Receiver

Rear track sensors

DC Motor

Steering Servo

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Difficulties• Speed Controller – “Pseudo” Shaft

Encoder • Heat Dissipation – May have to

place a second voltage regulator in parallel for drive electronics

• HCS12 operates differently in DBUG12 mode than it does in LoadEE mode, so tracing code is practically impossible

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Testing Methodology• Unit testing of both software and

hardware units• Unit integration and system-wide

testing• Extensive operation to ensure

proper burn-in

• For code: “Desk Checks” by the person who didn’t write the code

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Track Following Demo

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Questions?

• Thank you!