Autonomous Control of a Autonomous Control of a Scalextric Slot Car on a Scalextric Slot Car on a

User-Defined TrackUser-Defined Track

Siddharth KamathSiddharth Kamath

Souma MondalSouma Mondal

Dhaval PatelDhaval Patel

School of Electrical and Computer Engineering

Georgia Institute of Technology

http://www.scalextric-usa.com/

What is Slot Car Racing?What is Slot Car Racing?Electric Contacts

Motor

Powered Rails

Resistor

Handheld Controller

Power Pack

http://www.wikipedia.com

Project OverviewProject Overview

Design a system that allows a car to Design a system that allows a car to autonomously race against a human playerautonomously race against a human player

Marketed toward existing Scalextric Marketed toward existing Scalextric customers who cannot easily find customers who cannot easily find opponentsopponents

The product will keep the user base active The product will keep the user base active and boost the number of repeat customersand boost the number of repeat customers

The base station will cost $180 and each The base station will cost $180 and each car will cost $50car will cost $50

Design ObjectivesDesign ObjectivesAutonomously control car by:Autonomously control car by:

Monitoring position of car around track Monitoring position of car around track in real-timein real-timeAnalyzing position data and applying Analyzing position data and applying appropriate voltage to trackappropriate voltage to track

Display last checkpoint passed if slot Display last checkpoint passed if slot car falls off the trackcar falls off the track

Record performance metrics such as Record performance metrics such as lap times and top speedlap times and top speed

System OverviewSystem OverviewPosition Data

Digital In

USB

Analog Out

Electric Contacts

Motor

Powered Rails

Power Pack

http://www.wikipedia.com

Main SubsystemsMain Subsystems

Control AlgorithmControl

Algorithm

Data Transmissi

on

Data Transmissi

on

Position/Speed

Detection

Position/Speed

Detection

Position and Speed Detection

Position – Increment counter per pair of Position – Increment counter per pair of reflective stripsreflective strips

Velocity – Obtain one velocity per Velocity – Obtain one velocity per checkpointcheckpoint

5V

0VTime

Checkpoints

Reflective Strips

Line DetectorLine Detector

LOW

HIGH

IR LED

Phototransistor

Wireless Transmitter

Advantages of a Line Detector

InexpensiveInexpensive Easy to useEasy to use Digital output – convenient for Digital output – convenient for

wireless transmissionwireless transmission Continuous sensing – no polling Continuous sensing – no polling

necessarynecessaryhttp://www.lynxmotion.com/

Data TransmissionData Transmission

Data transmitted from car to PCData transmitted from car to PC Wireless transfer from Slot Car using Linx Wireless transfer from Slot Car using Linx

Technologies HP3 wireless transmitter and Technologies HP3 wireless transmitter and receiverreceiver

Data read in through NI USB DAQ into Data read in through NI USB DAQ into LabVIEW on PCLabVIEW on PC

Voltage from PC to trackVoltage from PC to track Control Voltage from LabVIEW output through Control Voltage from LabVIEW output through

NI USB DAQNI USB DAQ DAQ output voltage amplified to meet voltage DAQ output voltage amplified to meet voltage

specifications of trackspecifications of track

Power Supply SelectionPower Supply Selection

CR2450 Li-MnOCR2450 Li-MnO22 Cell - Used to power the Cell - Used to power the photo-interrupter and wireless modules photo-interrupter and wireless modules on the caron the car

ConstraintsConstraints Low weight (6gm)Low weight (6gm) Nominal voltage (3V)Nominal voltage (3V) High capacity (600mAh)High capacity (600mAh) InexpensiveInexpensive Easily obtainableEasily obtainable

http://www.wikipedia.com

Control AlgorithmControl Algorithm

Get Upcoming

Track Layout

Get Upcoming

Track Layout

Position

Speed

Calculate Track

Complexity

Calculate Track

Complexity

Determine Optimal Track

Voltage

Determine Optimal Track

Voltage

Desired Track Voltage

Track Input by User

Calculating ComplexityCalculating Complexity

x – distance from the front of the car

K – curvature of the track at that point

50cm – the horizon

The Mysterious Exponent The Mysterious Exponent cc

Multiplicative constants can be Multiplicative constants can be factored out and therefore do not factored out and therefore do not workwork

The exponent c therefore helps tune The exponent c therefore helps tune the importance of the curvature the importance of the curvature relative to the distancerelative to the distance

Other Software FactorsOther Software Factors

User selected difficulty – affects the User selected difficulty – affects the aggressiveness and the top speedaggressiveness and the top speed

Learning from crashes – the Learning from crashes – the complexity rating for that section of complexity rating for that section of track is increasedtrack is increased

Demonstration PlanDemonstration Plan

System drives slot car around circuit System drives slot car around circuit without falling off trackwithout falling off track

Race the slot car against an Race the slot car against an experienced user on an arbitrary trackexperienced user on an arbitrary track

Scale system’s performance depending Scale system’s performance depending on user’s difficulty settingon user’s difficulty setting

In case of derailing, slot car can be In case of derailing, slot car can be placed onto last checkpoint and placed onto last checkpoint and resume normal operationresume normal operation

Problems and IssuesProblems and Issues

Scaling voltage and power when Scaling voltage and power when connecting NI DAQ to trackconnecting NI DAQ to track

Optimizing algorithmOptimizing algorithm Empirically determining the constant Empirically determining the constant

parametersparameters Scaling performance based on difficulty Scaling performance based on difficulty

levels levels

Project ScheduleProject Schedule

OctoberOctober

NovembeNovemberr

DecemberDecember

Hardware Testing and Software Development: Crash Tolerance, Control Parameters,

Multiple Difficulty Levels

Interfacing: Sensors, Control Unit and Race Track

Power Supply, Wireless Transmission, NI-DAQ

Additions: Optional Software Features

Final Demo

Budget and Cost AnalysisBudget and Cost Analysis NI USB 6008 (DAQ)NI USB 6008 (DAQ) $150$150 HP3 Series Receiver HP3 Series Receiver $30$30

Base StationBase Station $180$180

HP3 Series Transmitter HP3 Series Transmitter $25$25 Line Tracker Line Tracker $20$20 Five 3V Coin BatteriesFive 3V Coin Batteries $5$5

CarCar $50$50

TotalTotal $230$230

Current StatusCurrent Status

CompleteComplete Line tracker and NI-DAQ testedLine tracker and NI-DAQ tested Algorithm simulationAlgorithm simulation

Upcoming MilestonesUpcoming Milestones Testing of wireless interface by Oct Testing of wireless interface by Oct

2525thth Data transfer from car to PC to track Data transfer from car to PC to track

by Oct 30by Oct 30thth

Questions?Questions?

Position Detection Position Detection SensorSensor

http://www.lynxmotion.com/

Spacing Requirements

Max slot car speed = 1000 mm/sMax distance between checkpoints =

100 mmMax ping rate = 10 pings/secTransmission rate = 56,000 pings/sec

< 10cm

Checkpoint n Checkpoint n+1