ENCODERS

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ENCODERS

• Presented by
• Jianguo (Max) Wang
• October 4, 2004

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Concepts related to encoders

• What is a sensor?
• A sensor is a device that detects the state of
  the environment such as energy, heat, light,
  magnet, supersonic, etc. and convert them to
  electric signals.

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Concepts related to encoders

• What is an encoder?
• An encoder is a sensor for converting rotary
  motion or position to a series of electronic
  pulses

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Basic architectures of encoders

• Linear architecture
• Linear encoders, which consist of a long linear
  read track (analogous to the code disk of a
  rotary encoder), together with a compact read
  head, address these concerns. We offer three
  grades of linear encoders, to suit a variety of
  application requirements.

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Basic architectures of encoders

• Rotary architecture
• Rotary encoders serve as measuring sensors for
  rotary motion and for linear motion when used in
  conjunction with mechanical measuring standards
  such as leadscrews, and convert rotary motion
  (incremental or absolute) into electrical
  signals. They are both effective and low cost
  feedback devices. In high-accuracy applications,
  a number of error sources (leadscrew cumulative
  and periodic error, thermal expansion, and nut
  backlash, for example)
• render rotary feedback inadequate.

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The types of encoders

• Absolute encoders
• Absolute encoders have a unique code that can
  be detected for each angular position
• Absolute encoders are much more complex and
  expensive than incremental encoders

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The types of encoders

• Incremental encoders
• Pulses from LEDS are counted to provide rotary
  position
• Two detectors are used to determine direction
  (quadrature)
• Index pulse used to denote start point
• Otherwise pulses are not unique

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The applications

• Positioning
• While a lead screw or rack-and-pinion
  converts rotary motion to linear motion, an
  encoder converts the same motion into electronic
  pulses. The pulses typically are used as input
  signals for counters, PLCs, or numerical-control
  equipment

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The applications

• Length measurement
• Roll or sheet materials need to be measured
  during transport through converting or
  cut-to-length machinery. An encoder, when
  combined with a measuring wheel or coupled to a
  roller, will produce electronic pulses equal to
  units of length. Since fractional units may be
  measured, very precise operation is possible

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Current state

• Encoders are wildly used in industry
• machine tools
• textile machinery
• printing presses
• wood working machines
• handling technology
• conveying and storage technology
• robotics

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Costs of encoders

• From less than 100 to more than 10,000 . It
  depends on your requirement.

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Rules and limitations of encoders

• Linear rotary
• Linear encoders are more accurate.
• Absolute incremental
• Absolute encoders are more expensive.
• Incremental encoders spend more time for
  startup

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Rules and limitations of encoders

• Magnetic Optical

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Vendors

• Heidenhain
• Renco
• Renishaw
• autonics
• Stegmann
• PepperlFuchs

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How to Choose an encoder

• What the encoder is used for?
• Cost
• Working environment
• Resolution
• Requirement for the output standard of the
  encoder
• Dimensions
• Limits such as warm-up or startup time, maximum
  operating speed, bear life and so forth
• Choose an appropriate model and type of encoder

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An example for choosing an encoder
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Specification examples

• Linear encoders

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Specification examples

• Rotary encoders

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How to integrate
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Application examples

• Model 716 (Cube Encoder) made by ECP were
  equipped on the lumber devices to produce up to
  15 more lumber from each log

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Application examples

• The Company of Ground Force mounts EPC encoder
  on the trucks used at mining operations to
  measure the rotation of pump shafts and of
  augers. The pumps deliver wet ingredients, while
  the augers deliver the dry ingredients.

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Application video
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Class Application

• Robots uses rotary encoders wildly

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References

• H.R. Everett,Sensor for Mobile Robots,
  page41-45.
• http//machinery.articleinsider.com
• http//www.sick.de
• http//web6.automationdirect.com
• http//www.euchner-usa.com
• http//news.managingautomation.com
• http//www.renco.com
• http//www.ssirobotics.com
• http//www.senix.com
• http//www.heidenhain.com
• http//www.ab.com
• http//www. encoderdevices.com