The Enforcer Laura Celentano Glenn Ramsey Michael Szalkowski

SPEED LIMIT 65 RF Overview Autonomous vehicle speed control system RFID speed limit signs RFID reader detects signs Car automatically changes speed to reflect limit

System Interface 2 Switches and 2 Lights –Power –Operation 2 7-Segment Displays –Speed (ft/s) –X.X format Power Off On Off On Operation

Radio Frequency Identification (RFID) Method of identifying unique items using radio waves - Identification, location, price, color, etc. - Found on products (Wal-Mart), E-ZPass, etc.

EM4102 Thin Card RF Transmitter Parallel Read Range = ~4.75'' Perpendicular Read Range = ~0.5'' ~4.75'' Vehicle Direction Inductive Coil 3.75'' Magnetic Field (Signal Range) ~0.5'' Radio Frequency Identification (RFID) RFID Subsystem Consists of a Reader and a Tag –Reader: one or more antennae used to interrogate a tag –Tag: relays pertinent information back to reader –Two types: Passive vs. Active

RFID Testing Results Analytic Components –Vehicle Speed Limitations How fast can we pass by a tag and make a successful communication? –Track Following Requirements How close must we be to the tag to make a successful communication?

RFID Detection Underpass Design –More robust method of detecting RFID Tags –Reader equipped to the top of the vehicle ensures that it will always be within the acceptable read range –Eases burden on track detection algorithm; loosens accuracy requirement for staying precisely on the track RFID Tag RFID Tag

Track Following IR Sensors Reflective Track

Sensor Specs Fairchild QRB1134 Rise and fall times 8 us Allows for over 500 samples per meter at vehicle’s possible max speed Comparator provides TTL output

Processing HCS12 timer fires at regular intervals and captures the sensor input Algorithm interprets sensor input For safety purposes, operation is suspended if the track is lost (“unknown state”)

Power System –9.6V Rechargeable Battery DC Motor –5V Regulator Servo Motor Microcontroller Support Hardware 1 A –Need 865 mA

Direction and Speed Control Direction Control –Servo Motor –16-bit PWM Speed Control –DC Motor –L6203 DMOS Full Bridge Driver –Capable of multi-speed forward and reverse operation –2 16-bit PWMs

Speed Detection Shaft Encoder –Notched Wheel OPB930W –Slotted Optical Switch –TTL Output –5 us Propagation Delay –Connected to a Timer Input Capture

Testing Strategy Individual Component Testing –RFID Communication Define 3 distinct speeds, associate unique ID# Construct underpass of appropriate dimensions –Track Following Algorithm Proper sensor operation verification Verify vehicle can make turns following track –Vehicle Speed Calculation & Control Verify direction control Verify speedometer Verify speed control unit for the 6 speed transitions Full System Integration Testing

Possible Problems Missed RFID tag communication Possible loss of track Different speeds require different turning angles Mounting the shaft encoders

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