Non-Contact Ranging Sensors

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Non-Contact Ranging Sensors

• Robert Blaser
• Assignment 1
• MechatronicsECE 5320

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Outline

• Reference List
• To Explore Further
• Major Applications
• Introduction
• Ranging Techniques Employed
• Non-Contact Range Sensor Basics
• Laser-Based TOF Systems
• SICK LMS 200

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Reference List

• Robert 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/1004SickLMS20
  0/SickLMS200.html
• SICK, (2004, Mar. 1). SICK Products (2004)
  Online. Available http//www.sick.de/de/produ
  cts/categories/auto/lasermeasurementsystemsindoor/
  lms200indoor/en.html

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To Explore Further

• Large variety of range sensors useful with mobile
  robots
• http//www.andrew.cmu.edu/rjg/websensors/robot_se
  nsors2.htmlrange
• Resource sites explaining how different types of
  range sensors work
• http//www.cs.brown.edu/people/tld/courses/cs148/0
  2/sonar.html
• http//abrobotics.tripod.com/Snuffy/GP2D12.htm

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Major Applications

• Measurement of objects
• Determination of object volumes
• Determination of object ranges
• Classification of objects
• Monitoring storage capacity
• Positioning
• Determining the position of objects
• Navigational support
• Monitoring areas
• Collision prevention
• Counting people

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Introduction

• Non-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.

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Ranging Techniques Employed

• Time of Flight (pulsed)
• Triangulation
• Phase-shift Measurement
• Frequency Modulation
• Interferometry
• Swept Focus
• Return Signal Intensity

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Non-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.

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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 and
• TOF is the time of flight measured
• in seconds. This equation
• changes a little when using sub-
• speed of light ranging sensors.

The Mechatronics Handbook
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Non-Contact Range Sensor Basics

• 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)

The Mechatronics Handbook
The Mechatronics Handbook
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Non-Contact Range Sensor Basics

• 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
  surface

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Non-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.

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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.

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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.

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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.

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Laser-Based TOF Systems

• 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.

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SICK LMS 200

• The LMS 200 is a non-contact
• Laser Measurement System that
• scans its surroundings two-dimensionally
• like laser radar. It operates
• within a temperature range of between
• 0 C and 50 C and, as an
• active scanning system, requires
• no auxiliary passive components
• such as reflectors or position markers.
• The LMS 200s high resolution
• allows it to take on tasks
• that were hitherto impossible or
• could only be achieved with
• difficulty or at great cost.

SICK Products
LMS 200 Operating Principle
Laser Measurement System (LMS)
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SICK LMS 200

• SICK LMS 200 Specifications

SICK Products
SICK Products
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SICK LMS 200

• Typical sample application of SICK LMS 200

Minimizing the time and costs of luggage
logistics is a top priority for airport
management. With the help of the Laser
Measurement System LMS 200 it is possible to
classify luggage automatically during its
transportation. In this way it can be recognized
very soon, if a piece of luggage fits into a
conveyor container of known dimensions.
Standstill times and the costs of personnel will
be reduced.
SICK Products
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SICK LMS 200

• Other applications of SICK LMS 200

There are many applications that the SICK LMS 200
can be used for. The pictures below show just a
few varying applications.
SICK Products
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SICK LMS 200

• Advantages of SICK LMS 200
• Very accurate
• Great for many applications
• Reliable
• Disadvantages of SICK LMS 200
• Physically larger than other range sensors
• More expensive than other range sensors
• Complex design