Download
haptics and virtual reality n.
Skip this Video
Loading SlideShow in 5 Seconds..
Haptics and Virtual Reality PowerPoint Presentation
Download Presentation
Haptics and Virtual Reality

Haptics and Virtual Reality

115 Views Download Presentation
Download Presentation

Haptics and Virtual Reality

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Haptics and Virtual Reality Lecture 3: • Sensors & Actuators-1 M. Zareinejad

  2. Outline # Sensors Sensortypes Sensorexamples – – #Actuators Actuatortypes Actuatorexamples – –

  3. TheHapticSystem Human

  4. Passive & Active joint

  5. SensorApplications Eyetracking Headtracking Bodytracking Handtracking     Mostimportantfortypicalhapticinterfaces –

  6. Sensortypes Magnetic Optical Acoustic Inertial Mechanical      Mostimportantfortypicalhapticinterfaces –

  7. MechanicalTrackers Ground-basedlinkagesmostcommonlyused PositionSensors   digital:opticalencoders analog:Hall-effect(magnetic) – –

  8. OpticalEncoders Emitter Howdotheywork? Detector  Afocusedbeamoflightaimedatamatched photodetectorisinterruptedperiodicallybyacoded patternonadisk Producesanumberofpulsesperrevolution(Lotsof pulses=highcost) – – Quantizationproblemsatlowspeeds Absolutevs.Incremental  

  9. OpticalEncoders Absolutevs. Incremental  Resolution?

  10. OpticalEncoders Phase-quadratureencoder 2channels,90°outofphase   allowssensingofdirectionofrotation –

  11. Encoder States & Decoding

  12. Hall-EffectSensors Howdotheywork?  – Asmalltransversevoltageisgeneratedacrossa current-carryingconductorinthepresenceofa magneticfield (Discoverymadein 1879,butnotuseful untiltheadventof semiconductor technology.)

  13. Hall-Effect Sensors Vh=Hallvoltage Rh=Hall coefficient RhIB t I=Current B=Magnetic fluxdensity t=Elementthickness Vh= Amountofvoltageoutputrelatedtothe strengthofmagneticfieldpassingthrough. Linearoversmallrangeofmotion   Needtobecalibrated – Affectedbytemperature,othermagnetic objectsintheenvironments 

  14. Hall-Effect Sensors Vh=Hallvoltage Rh=Hall coefficient I=Current B=Magnetic fluxdensity t=Elementthickness RhIB t Vh= • The voltage varies sinusoidally with rotation angle Resolution?

  15. Potentiometers

  16. Potentiometers Resolution?

  17. Acoustic Tracker Speaker Microphone

  18. Acoustic Tracker

  19. Magnetic Tracker

  20. Magnetic Tracker

  21. Optical Tracker • Outside-Looking-In • Inside-Looking-Out

  22. Optical Tracker

  23. Data gloves

  24. Data gloves

  25. ActuatorTypes Electricmotors  • DC(direct current) • Brushed & Brushless • PM(permanent magnet) • Stepper Motors Pneumatic Actuators  Hydraulic Actuators 

  26. PMDCbrushedmotors Howdothey work?  Rotatingarmature withcoilwindings iscausedtorotate relativetoa permanentmagnet currentistransmittedthroughbrushesto armature,andisconstantlyswitchedsothatthe armaturemagneticfieldremainsfixed. – –

  27. DCmotorcomponents

  28. DCmotorcomponents

  29. MotorEquations Torqueconstant,K Dynamicequation  

  30. PneumaticActuators Howdotheywork?  Compressedairpressureisusedtotransferenergy fromthepowersourcetohapticinterface. – Manydifferenttypes Concernsarefrictionandbandwidth  

  31. MeasuringVelocity Differentiateposition  advantage:usesamesensoraspositionsensor disadvantage:getnoisesignal – – Alternative  forencoders,measuretimebetweenticks –

  32. Digitaldifferentiation P1-P2 t Manydifferentmethods SimpleExample:   V= Average20readings=P1 Averagenext20readings=P2 wheretisthetheperiodoftheservoloop – – – Differentiation Increases noise 

  33. Time-between-ticks Time per ticks rather than ticks per time  useaspecialchipthatmeasurestime betweenticks  Especially good to do at slow speeds – Farespoorlyathighvelocities – p t v=

  34. SomeTerms AD/DA  analogtodigital digitaltoanalog – – Interruptroutine ServoLoop Servorate    Usuallyneedstobe>500Hz –

  35. D/AandA/D Convertsbetween voltagesandcounts Computerstores informationdigitally, andcommunicates withtheoutside worldusing+/-5V signals 101010101    LSB MSB

  36. D/AandA/D Convertsvoltagestocountsandviceversa A12-bitcard:   212decimalnumbers(4096) – 2994 Decimal(base10): Binary(base2): 1 0 1 1 1 0 1 1 0 0 1 0 Hexadecimal(base16): 1 0 1 1 1 0 1 1 0 0 1 0 B B 2 = BB2