ece 477 final presentation group 8 fall 2004. outline project overviewproject overview block...
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ECE 477 Final ECE 477 Final Presentation Presentation Group 8 Group 8 Fall Fall
20042004
OutlineOutline
• Project overviewProject overview• Block diagramBlock diagram• Professional componentsProfessional components• Design componentsDesign components• Success criteria demonstrationsSuccess criteria demonstrations• Individual contributionsIndividual contributions• Project summaryProject summary• Questions / discussionQuestions / discussion
Project OverviewProject Overview
• Objective: To design and build a shopping Objective: To design and build a shopping cart capable of following a shopper around a cart capable of following a shopper around a storestore– Shopper carries an ultrasonic beaconShopper carries an ultrasonic beacon– Cart follows beacon by maintaining fixed Cart follows beacon by maintaining fixed
signal strength (within a small range)signal strength (within a small range)– Infrared sensors mounted on cart enable it Infrared sensors mounted on cart enable it
to avoid obstaclesto avoid obstacles
Block DiagramBlock Diagram
Atmel ATMega32L
Motor1
Sharp GP2D15
Sharp GP2D15
Ultrasonic Receiver 1
UltrasonicReceiver 2
Motor2
PWM
PWMIRQ
IRQ
A/D A/D
Professional ComponentsProfessional Components
• Constraint analysis and component selection Constraint analysis and component selection rationalerationale
• Patent liability analysisPatent liability analysis• Reliability and safety analysisReliability and safety analysis• Ethical and environmental impact analysisEthical and environmental impact analysis
Constraint AnalysisConstraint Analysis
• Microcontroller Constraints:Microcontroller Constraints:– Moderate clocking speed (1 – 4 MHz)Moderate clocking speed (1 – 4 MHz)– Modest space constraintsModest space constraints– Peripheral requirementsPeripheral requirements
• A/D ConverterA/D Converter• RTI/Timer module and PWMRTI/Timer module and PWM• External InterruptsExternal Interrupts
– Power and cost efficientPower and cost efficient
Constraint AnalysisConstraint Analysis
• Microcontroller Candidates:Microcontroller Candidates:– Rabbit / PIC:Rabbit / PIC: Did not offer required Did not offer required
combination of peripheralscombination of peripherals– HC05 / HC11:HC05 / HC11: One-time programmable One-time programmable
memorymemory– MC9S08GT32 / ATMega32L:MC9S08GT32 / ATMega32L: Identical Identical
feature set – Atmel chip was chosen feature set – Atmel chip was chosen
due to ready availability of due to ready availability of
development toolsdevelopment tools
Constraint AnalysisConstraint Analysis
• Infrared Proximity SensorInfrared Proximity Sensor
– Prime candidates were Sharp GP2D12 and Prime candidates were Sharp GP2D12 and Sharp GP2D15 (analog vs digital)Sharp GP2D15 (analog vs digital)
– Chose GP2D15 – digital output was more Chose GP2D15 – digital output was more convenient and did not tie up A/Dconvenient and did not tie up A/D
• DC MotorDC Motor
– Fast enough to keep up with a personFast enough to keep up with a person
– Sufficient torque to power 6lb. cart Sufficient torque to power 6lb. cart
– Jameco 10:1, 600RPM,12V DC Jameco 10:1, 600RPM,12V DC
geared motorgeared motor
Patent Liability AnalysisPatent Liability Analysis
• Using Sensors to track / locate objectsUsing Sensors to track / locate objects– US Pat # 5,165,064 US Pat # 5,165,064
• Uses array of ultrasonic transducers to locate a beaconUses array of ultrasonic transducers to locate a beacon
– US Pat # 5,491,670 US Pat # 5,491,670 • Uses multiple ultrasonic beacons to triangulate positionUses multiple ultrasonic beacons to triangulate position
– US Pat # 6,567,044US Pat # 6,567,044 • Uses sensors to determine locationUses sensors to determine location
• All cause problems under doctrineAll cause problems under doctrineof equivalents. First is also literalof equivalents. First is also literal
Patent Liability AnalysisPatent Liability Analysis
• Other Patent Liability issuesOther Patent Liability issues– US Pat # 4,751,658 US Pat # 4,751,658
• Uses sensors to avoid obstaclesUses sensors to avoid obstacles
– US Pat # 5,911,767 US Pat # 5,911,767 • Has a central control that uses sensor data to determine Has a central control that uses sensor data to determine
future actionfuture action
– US Pat # 4,710,020 US Pat # 4,710,020 • Uses sensors to determine distance of a transmitterUses sensors to determine distance of a transmitter
• The first is a literal infringementThe first is a literal infringementrest are infringements under the rest are infringements under the doctrine of equivalentsdoctrine of equivalents
Reliability/Safety AnalysisReliability/Safety Analysis
• Reliability Drivers:Reliability Drivers:– Heat : Increased heat increases unreliabilityHeat : Increased heat increases unreliability– Component Derating: Prevents wear outComponent Derating: Prevents wear out
• Product Specific Drivers:Product Specific Drivers:– Low power microcontroller, good ventilation, Low power microcontroller, good ventilation,
lowers unreliability caused by heatlowers unreliability caused by heat– High current through motorsHigh current through motors
and IR leads to non-derated and IR leads to non-derated
power chipspower chips
Reliability/Safety AnalysisReliability/Safety Analysis
• Components have failure rates of the order of Components have failure rates of the order of 10E-6 or better 10E-6 or better
• Acceptable for a non-critical applicationAcceptable for a non-critical application• Components analyzed for failure:Components analyzed for failure:
– ATMega32L – 4.29E-6 failsATMega32L – 4.29E-6 fails– Max663 – 3.336E-6 failsMax663 – 3.336E-6 fails– IRL530N – 4.795E-6 failsIRL530N – 4.795E-6 fails
Reliability/Safety AnalysisReliability/Safety Analysis
• FMECA- FMECA- – 5 major blocks: U/S transmitter, U/S receivers, IR 5 major blocks: U/S transmitter, U/S receivers, IR
sensors, Motor drive circuitry, Power circuitrysensors, Motor drive circuitry, Power circuitry– Critical reliability problem - potential collision Critical reliability problem - potential collision
with user:with user:• Motors stuck onMotors stuck on• Defective IR sensorsDefective IR sensors
– Both components well derated, Both components well derated,
and should not fail, leading to highand should not fail, leading to high
overall safety of cart. overall safety of cart.
Ethical/Environmental AnalysisEthical/Environmental Analysis
Environmental ImpactEnvironmental Impact• Manufacture of semiconductors Manufacture of semiconductors
– Environmentally unfriendlyEnvironmentally unfriendly• Soldering on PCBsSoldering on PCBs
– Exposure to leadExposure to lead• Plastic casingPlastic casing
– RecyclableRecyclable
Ethical/Environmental AnalysisEthical/Environmental Analysis
Environmental ImpactEnvironmental Impact• ElectricityElectricity
– Precious resource usedPrecious resource used• Battery DisposalBattery Disposal
– Careful and correct disposal neededCareful and correct disposal needed
Ethical/Environmental AnalysisEthical/Environmental Analysis
Ethical ImpactEthical Impact• SafetySafety
– Warning labelsWarning labels– DocumentationDocumentation– Safety mechanismsSafety mechanisms
• ReliabilityReliability– Perform as stated in user manualPerform as stated in user manual
Design ComponentsDesign Components
• Packaging design considerationsPackaging design considerations• Schematic design considerationsSchematic design considerations• PCB layout design considerationsPCB layout design considerations• Software design considerationsSoftware design considerations
Packaging DesignPackaging Design
• Board mounted on bottom trayBoard mounted on bottom tray• Board dimensions - 4” x 6Board dimensions - 4” x 6””
• Motors with wheels attached mounted at Motors with wheels attached mounted at bottom – front wheel drivebottom – front wheel drive
• Two ultrasonic sensors mounted at front endTwo ultrasonic sensors mounted at front end• Two infrared sensors mounted atTwo infrared sensors mounted at
front cornersfront corners
Packaging DesignPackaging Design
• Cart only moves forward Cart only moves forward – IR sensors only needed at front two IR sensors only needed at front two
cornerscorners– Ultrasonic sensors placed strategically to Ultrasonic sensors placed strategically to
allow determination of beacon bearingallow determination of beacon bearing• Back wheels are freely rotating caster wheelsBack wheels are freely rotating caster wheels
– Provides for smaller turning radiusProvides for smaller turning radius
Packaging DesignPackaging Design
• Beacon carried by shopperBeacon carried by shopper– Small and lightSmall and light
• Circuit may be damaged/tampered withCircuit may be damaged/tampered with– All circuitry hiddenAll circuitry hidden
• Storage space must be maximizedStorage space must be maximized– No components placed in cartNo components placed in cart
• Batteries must be accessibleBatteries must be accessible– Batteries not hiddenBatteries not hidden
Schematic DesignSchematic Design• Main Main
SchematicSchematic– Headers Headers
for all for all sensorssensors
– Motor Motor control control MOSFETsMOSFETs
– IR input IR input invertedinverted
Schematic DesignSchematic Design
• Cart Power Cart Power SupplySupply
– Power: Power: 9.6V9.6V
– 6V rail6V rail
– -6V rail-6V rail
– 3.3V 3.3V railrail
Schematic DesignSchematic Design
• TransmitterTransmitter– Max 663Max 663– 12 V 12 V
batterybattery– 555 timer555 timer
Schematic DesignSchematic Design
• ReceiverReceiver
– LF353 op LF353 op ampsamps
– Gain of 90Gain of 90
– Filter for Filter for noisenoise
PCB Layout DesignPCB Layout Design
• 5 PCBs – 1 U/S Transmitter, 3 U/S Receivers, 1 Main 5 PCBs – 1 U/S Transmitter, 3 U/S Receivers, 1 Main Board. Board.
• Need modular layout to enable cutting of single Need modular layout to enable cutting of single board. board.
• Noise immunityNoise immunity::– Bypass capacitors close to microcontroller and Bypass capacitors close to microcontroller and
noise suppression capacitors between power and noise suppression capacitors between power and ground at intervalsground at intervals
– Need wide, short traces to reduce Need wide, short traces to reduce
inductance, thereby reducing current inductance, thereby reducing current
spikes and noise. spikes and noise.
PCB Layout DesignPCB Layout Design
• Noise ImmunityNoise Immunity::– No 90No 90oo angles minimize wave reflections angles minimize wave reflections
which lead to noise and radiationwhich lead to noise and radiation– Reduce interference between sub-circuits, Reduce interference between sub-circuits,
by placing individual power and ground in by placing individual power and ground in parallelparallel
– High current motors need to be isolated High current motors need to be isolated from rest of circuit, powered from rest of circuit, powered
directly from battery directly from battery – Copper pourCopper pour
PCB Layout DesignPCB Layout DesignReceivers Transmitter Main board
Software DesignSoftware Design
• 32Kb flash, 2Kb SRAM – EEPROM not used32Kb flash, 2Kb SRAM – EEPROM not used• Application code is organized in a command-Application code is organized in a command-
driven fashiondriven fashion– Ultrasonic receivers are polled periodicallyUltrasonic receivers are polled periodically– Infrared sensors generate interrupt Infrared sensors generate interrupt
requestsrequests– Main loop reads voltage samplesMain loop reads voltage samples
and adjusts motor speedsand adjusts motor speeds
Software DesignSoftware Design
Main loopMain loop
FlowchartFlowchart
Start
Initialize on-board peripherals
Enable global interrupts
Read the last sampled front left, and front right voltages
Is left or right voltage non-
zero?
Motor speed duty cycles = (255 – Voltage) * 1.5
Y
Turn off both motors
N
Software DesignSoftware Design
Periodic Periodic ExternalExternal
Interrupt Interrupt InterruptInterrupt
Service ServiceService Service
Routine RoutineRoutine Routine
Start
Clear the interrupt flag
Read left receiver
Read right receiver
Store voltage samples in global data structure
Return
Start
Clear the interrupt flag
Turn off opposite motor
Adjust motor on same side
Disable ultrasonic receiver polling
Return
Success Criteria DemonstrationsSuccess Criteria Demonstrations
1.1. Ability to generate a beacon signal - Ability to generate a beacon signal - demodemo
2.2. Ability to identify the bearing of the beacon Ability to identify the bearing of the beacon - - demodemo
3.3. Ability to approximate the distance to the Ability to approximate the distance to the beacon using relative signal strength - beacon using relative signal strength - demodemo
4.4. Ability to follow the beacon - Ability to follow the beacon - demodemo
5.5. Ability to avoid obstacles in theAbility to avoid obstacles in the
path of motion - path of motion - demodemo
Individual ContributionsIndividual Contributions
• Team Leader – Aliasgar PoonawalaTeam Leader – Aliasgar Poonawala• Team Member 2 – Raghuram RamanujanTeam Member 2 – Raghuram Ramanujan• Team Member 3 – Clive LopezTeam Member 3 – Clive Lopez• Team Member 4 – Mohan RokkamTeam Member 4 – Mohan Rokkam
Team Leader – Aliasgar PoonawalaTeam Leader – Aliasgar Poonawala
• Packaging designPackaging design• Ethical and environmental impact analysisEthical and environmental impact analysis• Software debuggingSoftware debugging• Component selectionComponent selection
Member 2 – Raghuram RamanujanMember 2 – Raghuram Ramanujan
• Design constraint analysis and component Design constraint analysis and component selectionselection
• Software design Software design – Wrote diagnostic routinesWrote diagnostic routines– Devised control algorithm and wrote core Devised control algorithm and wrote core
software modulessoftware modules• Hardware design Hardware design
– Microcontroller interfacingMicrocontroller interfacing– Infrared sensor interfacingInfrared sensor interfacing
• Hardware debuggingHardware debugging
Member 3 – Clive LopezMember 3 – Clive Lopez
• PCB layout designPCB layout design• Hardware designHardware design
– Designed (and redesigned) ultrasonic circuitsDesigned (and redesigned) ultrasonic circuits– Microcontroller interfacingMicrocontroller interfacing
• Hardware debuggingHardware debugging• Soldering and population of boardSoldering and population of board• Reliability and safety analysisReliability and safety analysis• Component selectionComponent selection• PackagingPackaging
Member 4 – Mohan RokkamMember 4 – Mohan Rokkam
• Hardware design Hardware design – Ultrasonic circuitryUltrasonic circuitry– Microcontroller interfacingMicrocontroller interfacing
• Created and maintained webpageCreated and maintained webpage• Hardware debuggingHardware debugging• Soldering and population of boardSoldering and population of board• Schematic designSchematic design• Patent liability analysisPatent liability analysis• Component selectionComponent selection• PackagingPackaging
Project SummaryProject Summary
• Important lessons Important lessons learnedlearned– Fuses!Fuses!– Use bypass Use bypass
capacitorscapacitors– Effective time Effective time
managementmanagement– Trust team matesTrust team mates
• Important skills learnedImportant skills learned– OrCAD Capture and OrCAD Capture and
LayoutLayout– Soldering techniquesSoldering techniques– Power supply designPower supply design– Ability to interpret Ability to interpret
datasheetsdatasheets
Project SummaryProject Summary
• Second iteration enhancementsSecond iteration enhancements– Better control algorithmBetter control algorithm– Better noise immunity for sensorsBetter noise immunity for sensors– Ability to send different instructions via Ability to send different instructions via
beaconbeacon– Support for multiple cartsSupport for multiple carts– Better beacon rangeBetter beacon range– Additional sensorsAdditional sensors
Questions / DiscussionQuestions / Discussion