SOLUTION: Sensing Planning Acting information | My Assignment Tutor

Industrial systemsLecture 4Overview of Sensors!for Roboticswhere should I dig?whereis thetruck?Sensing Planning Actinginformationabout theenvironmentactionon theenvironmentWhat makes a machine a robot?Definition of a RobotA reprogrammable multi-functional manipulatordesigned to move materials, parts, tools or specializeddevices through various programmed motions for theperformance of a variety of Tasks.Components of a Robot•  Manipulator: Main body of robot (Links, Joints, otherstructural element of the robot)•  End Effector: The part that is connected to the lastjoint hand of a manipulator.•  Actuators: Muscles of the manipulators (servomotor,stepper motor, pneumatic and hydraulic cylinder).•  Sensors: To collect information about the internal stateof the robot or To communicate with the outsideenvironment.Components of a Robot- Continued•  Controller: Controls and co-ordinates the motion of theactuators.•  Processor: The brain of the robot. It calculates themotions and the velocity of the robot’s joints, etc.•  Software: Operating system, robotic software and thecollection of routines.Why do robots need sensors?θ?What is the angle of my arm?Internal InformationWhat is Sensing ?•  Collect information about the world•  Sensor – an electrical/mechanical/chemical device thatmaps an environmental attribute to a quantitativemeasurement–  attribute mixtures – often no one to one map–  hidden state in environment•  Each sensor is based on a transduction principle –conversion of energy from one form to another•  Also known as transducersWhy do robots need sensors??Where am I?LocalisationWhy do robots need sensors?Will I hit anything?Obstacle detectionSensing for specific tasksWhere is the crop line?AutonomousharvestingSensing for specific tasksWhere are the fork holes?Autonomous material handlingSensing for specific tasksFace detection and tracking•  Active–  send signal into environment and measureinteraction of signal w/ environment–  e.g. radar, sonar•  Passive–  record signals already present in environment–  e.g. video camerasTypes of SensorsTypes of Sensors•  Classification by medium used–  based on electromagnetic radiation of variouswavelengths–  vibrations in a medium–  concentration of chemicals in environment–  by physical contactTypes of Sensors•  Exteroceptive: deal w/ external world–  where is something ?–  how does it look ? (camera, laser rangefinder)•  Proprioceptive: deal w/ self–  where are my hands ? (encoders, stretchreceptors)–  am I balanced ? (gyroscopes, INS)Types of Sensors•  Interoceptive–  what is my thirst level ? (biochemical)–  what is my battery charge ? (voltmeter)❏ Touch sensors❏ Tilt sensors❏ Encoders❏ Bend sensors❏ Light sensors❏ Temperature sensors❏ Potentiometers❏ Laser rangefinders❏ CamerasSimple Practical Sensors that we canpurchaseTouch sensorsforcevoltagemeasurementa simple electrical flowswitchTilt sensorsanother simpleswitchgravity❏ Encoders measure rotational motion.❏ They can be used to measure the rotation of awheel.❏ Servo motors: Used in conjunction with anelectric motor to measure the motor’s positionand, in turn, control its position.EncodersEncodersImportant spec:Number of countsper revolutionVoltage square waveon onoff off off1 2 3 4 …Sample problemsSensor Analysis❏  How far does the wheel travel for 1 encoder count?❏  What happens if we change the wheel diameter?❏  How many counts are there per meter of travel?16 counts per rev. 10 cm wheel diameter10 cmSample problemsDiameterCircumferenceC = πDC = 10π cm10π cm1 rev =1 revx16 counts1.96 cmcountSample problemsSuppose I want 1.0 cm / count.What should my wheel diameter be?1.0 cmcount 1 rev =16 countsx16 cmrevC = 16 cmD = Cπ = 16 π =5.09 cmSample problemsFor my 10 cm wheel, how many encodercounts will there be for 1 meter of travel?1.96 cmcount 100 cm =1 meterx0.0196 mcount=0.0196 m/ct151 counts/mPhysics ExampleOhm’s LawV = I x RVRIvoltage current resistance9 = 0.009 x 1000(9 Volts)(1000 Ohms)(0.009 Amps)Electrical analogyVoltage CurrentResistancea larger pipe isless resistanceso more watera smaller pipe ismore resistanceso less waterBend sensora variable resistorresistance changesas it bends V = I x Rassuming constantcurrent, the measuredvoltage changes withresistanceLight sensorphoto-resistorresistance changeswith light intensityTemperature sensorthermal resistor“thermistor”resistance changeswith temperaturePotentiometeranotherrotational sensorresistance changeswith positionof dialRSample problemBend sensor specs:100 Ω when straight1000 Ω when bentGiven a 5 V source,what is the min. and max.current that is drawn?V = I x RI = VRmin = 51000 = 5 mAmax =5100 = 50 mA•  Basically used for ranging•  Light sensitive–  eyes, cameras, photocells etc.•  Operating principle–  CCD – charge coupled devices–  photoelectric effect•  IR sensitive – FLIR–  sense heat differences and construct images–  night vision applicationSensors based on EM SpectrumEM Spectrum•  Radio and Microwave–  RADAR: Radio Detection and Ranging–  Microwave radar: insensitive to clouds•  Coherent light–  all photons have same phase and wavelength–  LASER: Light Amplification by StimulatedEmission of Radiation–  LASER RADAR: LADAR – accurate rangingThe SICK Laser RangefinderEM Spectrum•  Nuclear Magnetic Resonance (NMR)–  heavy duty magnetic field lines up atoms in abody–  now expose body to radio signals–  different nuclei resonate at different frequencieswhich can be measured leading to an imageLocal Proximity Sensing in EM•  Infrared LEDs–  cheap, active sensing–  usually low resolution – normally used forpresence/absence of obstacles rather than ranging–  operate over small range•  SONAR: Sound Navigation and Ranging–  bounce sound off of something–  measure time for reflection to be heard – gives a rangemeasurement–  measure change in frequency – gives the relative speed of theobject (Doppler effect)–  bats and dolphins use it with amazing results–  robots use it w/ less than amazing resultsSensors based on SoundSonar and IR Proxmity•  Detection of chemical compounds and theirdensity in an area–  spectroscopy – mostly lab restricted–  fibre-optic techniques – recently developed–  chemical detection – sniffers and electronic nosesvia “wet chemistry on a chip”•  No major penetration in robotics yetapplications are vast (e.g. mine detection)Odor Sensors•  Whiskers, bumpers etc.–  mechanical contact leads to•  closing/opening of a switch•  change in resistance of some element•  change in capacitance of some element•  change in spring tension•  …Touch SensorsProprioceptive SensorsProprioceptive sensors measure values internal to thesystem (robot); e.g. motor speed, wheel load, robot armjoint angles, battery voltage. Exteroceptive sensorsacquire information from the robot’s environment; e.g.distance mea- surements, light intensity, soundamplitude•  Encoders, Potentiometers–  measure angle of turn via change in resistance or bycounting optical pulses•  Gyroscopes–  measure rate of change of angles–  fiber-optic (newer, better), magnetic (older)•  Compass–  measure which way is north•  GPS: measure location relative to globeProprioceptive Sensors•  What sensors to employ ?•  E.g. mapping–  ranging – laser, sonar, IR, stereo camera pair–  salient feature detection – doors using color•  Factors–  accuracy, cost, information needed etc etc.Problem: Sensor Choice•  Where do you put them ?•  On/off board (e.g. localization using odometryvs. localization using beacons)•  If onboard – where ?–  Reasonable arrangements – heuristic–  Optimal arrangements – mathematically rigorousProblem: Sensor PlacementActivityDescribe your idea of using a GPS sensor in a mobilerobot. Discuss accuracy, how connected. Whatapplication of the robot?Video to watch:https://www.youtube.com/watch?v=2JtSAW_W4T0https://www.youtube.com/watch?v=4UVSOEBws-EThank You