Non-Contact Ranging SensorsOutlineReference ListTo Explore Further…Major ApplicationsIntroductionRanging Techniques EmployedNon-Contact Range Sensor Basics...Non-Contact Range Sensor Basics…Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Laser-Based TOF SystemsSICK LMS 200Slide 18Slide 19Slide 20Slide 21Non-Contact Ranging SensorsRobert BlaserAssignment #1Mechatronics—ECE 5320Outline•Reference List•To Explore Further…•Major Applications•Introduction•Ranging Techniques Employed•Non-Contact Range Sensor Basics•Laser-Based TOF Systems•SICK LMS 200Reference ListRobert H. Bishop, THE MECHATRONICS HANDBOOK, CRC Press, 2002.Robosoft, (2004, Feb. 29). “Laser Measurement System (LMS)” (2003) [Online]. Available: http://www.robosoft.fr/SHEET/02Local/1004SickLMS200/SickLMS200.htmlSICK, (2004, Mar. 1). “SICK Products” (2004) [Online]. Available: http://www.sick.de/de/products/categories/auto/lasermeasurementsystemsindoor/lms200indoor/en.htmlTo Explore Further…•Large variety of range sensors useful with mobile robots –http://www.andrew.cmu.edu/~rjg/websensors/robot_sensors2.html#range•Resource sites explaining how different types of range sensors work–http://www.cs.brown.edu/people/tld/courses/cs148/02/sonar.html–http://abrobotics.tripod.com/Snuffy/GP2D12.htmMajor ApplicationsMeasurement of objects–Determination of object volumes–Determination of object ranges–Classification of objects–Monitoring storage capacityPositioning–Determining the position of objects–Navigational supportMonitoring areas–Collision prevention–Counting peopleIntroductionNon-Contact Range sensors use a number of technologies including light/optics, microwave, and ultrasonic to measure the distance from a reference point to an object.Non-Contact Range sensors all measure distances to an object with no physical contact, as the name implies.Ranging Techniques Employed•Time of Flight (pulsed)•Triangulation•Phase-shift Measurement•Frequency Modulation•Interferometry•Swept Focus•Return Signal IntensityNon-Contact Range Sensor Basics...•Classification–Active•Sensor radiates some form of energy into the field of interest. Some typical sensors in this category include radar, sonar and lidar.–Passive•Sensor relies on energy emitted from objects or targets of interest.Non-Contact Range Sensor Basics…Time Of Flight (TOF) Technique•The figure below shows a conceptual diagram with the Emitter and Receiver both located at the sensor.•The distance, d, in the diagram is defined as: where c is the speed of light andTOF is the time of flight measuredin seconds. This equation changes a little when using sub-speed of light ranging sensors.*2c TOFd =“The Mechatronics Handbook”•There are two basic methods for defining the Time Of Flight (TOF)–Beginning of signal burst to end of returning burst–Beginning of signal burst to maximum amplitude of returning burst (higher accuracies possible)Non-Contact Range Sensor Basics…“The Mechatronics Handbook”“The Mechatronics Handbook”•Potential sources of error for TOF systems–Variations in the speed of propagation (Large factor in acoustical systems)–Uncertainties in determining the exact time of arrival of a returning pulse–Inaccuracies in the timing circuitry used to measure the round-trip TOF–Interaction of the incident wave with the target surfaceNon-Contact Range Sensor Basics…•Variations in speed of popagation:–Propagation speed variations for electromagnetic energy are small and can be omitted for most applications except satellite-based systems and similar. However, when using acoustic systems propagation variations exist and need to be accounted for. Temperature changes, humidity and air content all influence the speed of sound enough to require proper adjustments.Non-Contact Range Sensor Basics…•Detection Uncertainties:–Detection time errors can occur because of two main reasons. The first is varying reflectivity of surfaces and the second is signal attenuation due to distance. Different target surfaces lead to a reflected pulse with varying degrees in amplitude for different targets at the same distance. Signal attenuation must also be accounted for due to spherical divergence.Non-Contact Range Sensor Basics…•Inaccuracies in the timing circuitry:–When using electromagnetic energy the timing circuitry has to be very precise due to the shorter wavelengths and fast propagation speeds. In fact, sub-nanosecond circuitry is required to even attain resolutions down to a foot. To attain resolutions down to 1mm requires circuitry with an accuracy of 3ps. This type of timing circuitry is expensive. Therefore without very expensive circuitry systems based on electromagnetic energy tend to show inaccuracies.Non-Contact Range Sensor Basics…•Target surface interactions:–When light, sound and radio waves strike a target surface they get scattered in different directions. The type of surface determines the amount of scattering. Some of these scattered waves can reflect off other objects also and essentially add ‘noise’ to the system. Angles of incidence are also important as reflected waves can not even make it back to the receiver if it hits the target above a critical angle. All of these factors make it harder to process the returned signal.Non-Contact Range Sensor Basics…•First appeared in the 1970s at the Jet Propulsion Laboratory, Pasadena CA.•Extremely short laser pulses are emitted rapidly pointed directly at the target.•Uses TOF measurements to find range•Accurate resolutions available but at increased costs.Laser-Based TOF SystemsSICK LMS 200• The LMS 200 is a non-contactLaser Measurement System thatscans its surroundings two-dimensionallylike laser radar. It operateswithin a temperature range of between0 °C and +50 °C and, as anactive scanning system, requiresno auxiliary passive componentssuch as reflectors or position markers.The LMS 200‘s high resolutionallows it to take on tasksthat were hitherto impossible orcould only be achieved withdifficulty or at great cost.“SICK Products”LMS 200 Operating Principle“Laser Measurement System (LMS)”SICK LMS 200•SICK LMS 200 Specifications:“SICK Products”“SICK Products”SICK LMS 200•Typical sample application of SICK LMS 200“SICK Products”Minimizing the time and costs of luggage logistics is a top priority for airport management.
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