Encoders New
Transcript of Encoders New
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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. andconvert 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 ofelectronic 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 rotaryencoder), together with a compact read head,address these concerns. We offer three grades oflinear encoders, to suit a variety of application
requirements.
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Rotary architectureRotary encoders serve as measuring sensors forrotary motion and for linear motion when used inconjunction with mechanical measuring standardssuch as leadscrews, and convert rotary motion(incremental or absolute) into electrical signals. Theyare both effective and low cost feedback devices. Inhigh-accuracy applications, a number of errorsources (leadscrew cumulative and periodic error,thermal expansion, and nut backlash, for example)
render rotary feedback inadequate.
Basic architectures of encoders
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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 andexpensive 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 tolinear motion, an encoder converts the same motion intoelectronic pulses. The pulses typically are used as input signalsfor counters, PLCs, or numerical-control equipment
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The applications
Length measurement
Roll or sheet materials need to be measured during transportthrough 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. Sincefractional units may be measured, very precise operation ispossible
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Encoders are wildly used in industry
machine tools
textile machinery printing presses
wood working machines
handling technology conveying and storage technology
robotics
Current state
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Costs of encoders
From less than 100$ to more than10,000 $. It depends on your
requirement.
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Rules and limitations of encoders
Linear & rotaryLinear encoders are more accurate.
Absolute & incrementalAbsolute encoders are more expensive.
Incremental encoders spend more time for startup
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Rules and limitations of encoders
Magnetic & OpticalMagnetic Encoders Optical Encoders
Unaffected by Contamination Very Susceptible to Contaminates
Increased Temperature Range
-40 to +125Limited Temperature Range -25 to +80
Improved Shock ResistanceOptical Rotors and Electronics Connections are
Susceptible
Absolute and Incremental Outputs Absolute Encoders Not Available in same Price Range
Reduced Cost Higher Cost due to 50% more Components
No Tuning or Mechanical
Adjustments
Optical encoders typically use a potentiometer to
compensate for manufacturing tolerances.
Potentiometers within all optical encoders are a
primary source of field failures and manufacturing
defects.
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Vendors
Heidenhain
Renco
Renishaw
autonics
Stegmann Pepperl+Fuchs
http://www.am.pepperl-fuchs.com/home/default.asphttp://www.encoderdevices.com/index.htm -
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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, maximumoperating speed, bear life and so forth
Choose an appropriate model and type of encoder
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An example for choosingan encoder
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Specification examples
Linear encoders
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Specification examples
Rotary encoders
http://www.encoderdevices.com/ed_14/ed_14.htm -
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How to integrate
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Application examples
Model 716 (Cube Encoder) made by ECP wereequipped on the lumber devices to produce up to15% more lumber from each log
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Application examples
The Company of Ground Force mounts EPC encoderon the trucks used at mining operations to measurethe rotation of pump shafts and of augers. The
pumps deliver wet ingredients, while the augersdeliver 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
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.b.com/http://www.b.com/http://www.ab.com/http://www.heidenhain.com/http://www.senix.com/http://www.ssirobotics.com/http://www.renco.com/http://news.managingautomation.com/http://www.euchner-usa.com/http://www.euchner-usa.com/http://www.euchner-usa.com/http://web6.automationdirect.com/http://www.sick.de/http://machinery.articleinsider.com/