autonomous control of scalextric slot car on user-defined track

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

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

Rails

Resistor

Control

ler

Power Pack

http://www.wikipedia.com

Project OverviewProject Overview

Race slot car autonomously against Race slot car autonomously against human playerhuman player

Target existing customers who Target existing customers who cannot easily find opponentscannot easily find opponents

Keep user base active and boost Keep user base active and boost number of repeat customersnumber of repeat customers

System ImplementationSystem ImplementationPosition Data

Digital In

USBAnalog Out

Electric Contacts

Motor

Power Pack

http://www.wikipedia.com

Powered Rails

Design Advantages

Line detector and reflective strips Cheap to implement Easy for end user Scalable

LabVIEW and NI DAQ Rapid prototyping environment Integrated data collection Potential software updates

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 once per Position – Increment counter once per checkpointcheckpoint

Velocity – Velocity – (One value per (One value per checkpoint)checkpoint)

5V

0VTime

Reflective Strip

50mm

Δt

50mm

Δt

Spacing Requirements

Max slot car speed = 2500 mm/sMax distance between checkpoints =

170 mmMax ping rate = 15 pings/secTransmission rate = 56,000 bits/sec

< 17cm

Checkpoint n Checkpoint n+1

Checkpoint Detect

HIGH

5V

0VTime

Checkpoint Pass

LOW

5V

0VTime

Data TransmissionData Transmission

Data transmitted from car to PCData transmitted from car to PC Wireless transfer using Linx HP3Wireless transfer using Linx HP3 Data read in through NI DAQ into Data read in through NI DAQ into

LabVIEW on PCLabVIEW on PC

Voltage from PC to trackVoltage from PC to track Control voltage from NI DAQControl voltage from NI DAQ DAQ output voltage amplified to DAQ output voltage amplified to

meet voltage specifications of meet voltage specifications of tracktrack

http://www.linxtechnologies.comhttp://www.ni.com

Wireless Transmission Captures

Crack within pulse

16 pulses/la

p

Power SupplyPower Supply CR2450 Button cell – Powers the line CR2450 Button cell – Powers the line

detector, wireless transmitter on cardetector, wireless transmitter on car 5V Voltage regulator – Power efficient, 5V Voltage regulator – Power efficient,

steady outputsteady output

http://www.wikipedia.com

Voltage Regulator

Amplifier LM 741 – Non-inverting amplifier circuit Input – 0-5V from NI DAQ Output – 0-12V to track

Amplifier Screen Capture

Input to Amplifier (0-5V)

Output from Amplifier (0-12V)

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

c - Tunes the importance of the Tunes the importance of the curvature relative to distance curvature relative to distance from carfrom car

Complexity Complexity ImplementationImplementation

CurrentlyCurrently Precision of position is one track segmentPrecision of position is one track segment Next three track segments consideredNext three track segments considered Single voltage calculated per track Single voltage calculated per track

segmentsegment

In progressIn progress Estimate position between checkpointsEstimate position between checkpoints Consider fixed distance ahead of carConsider fixed distance ahead of car Attain more accurate speed profileAttain more accurate speed profile

Data Errors

Problem Solution

Missing a checkpoint– Change batteries – Adjust line detector

False checkpoint detection

– Apply noise filter (10ms threshold)– Recombine cracked pulses (2ms threshold)

Example Data

Pulse due to noise

(<10ms)

Crack in Pulse

(<2ms)

Voltage

Time

Race Replay Feature

Sample track voltage during a race Data acquired at 10,000 Hz Save profile to file Plays profile back

Potential uses of race replay feature Compete against their own race profiles Compete against other competitor

saved profiles

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

Unit CostUnit Cost $230$230

Demonstration PlanDemonstration Plan Main demoMain demo

System drives slot car around circuit System drives slot car around circuit without derailingwithout derailing

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

Supplemental demoSupplemental demo Race slot car against a human opponent Race slot car against a human opponent Scale system’s performance based on Scale system’s performance based on

difficulty settingdifficulty setting

ResultsResults

Parameter ValuePosition Sensing – Checkpoint

detection99.4%

Velocity Sensing Error 0.6%

Pulse Error Rate 12.5%

Control Voltage onto Track0-12V (DC)

Speed Range0-

2500mm/s

Failures per Lap 0.1

Car Development

Original weight of car= 85g New weight of car = 110g

Attach line detector and circuit board to slot car with Velcro

Line detector no more than 0.5’’ above track

Optional use of antennae for receiver and transmitter

Car Dimensions

75mm

Car ViewsBattery

with Switch

Line Detector

Wireless Transmitt

er

Voltage Regulator

System OverviewSystem OverviewPosition Data

Digital In

USBAnalog Out

Electric Contacts

Motor

Power Pack

http://www.wikipedia.com

Powered Rails

System Hierarchy

Position Data

Digita

l In

USB

Analog Out

Demonstration Video

Current TasksCurrent Tasks

Better position estimates required to improve control

Ability to differentiate start checkpoint from other checkpoints

Control algorithm needs more fine tuning

Current StatusCurrent Status

Position detectionPosition detectionVelocity detectionVelocity detectionData transmissionData transmissionApplying amplified voltage to Applying amplified voltage to tracktrackDisplay last checkpoint passedDisplay last checkpoint passedCar developmentCar developmentRecord and play voltage profileRecord and play voltage profileImprove control algorithmImprove control algorithm

Questions?Questions?

Position Detection Position Detection SensorSensor

http://www.lynxmotion.com/

Line DetectorLine Detector

LOW

HIGH

IR LED

Phototransistor

Wireless Transmitter

Car Components