encoders new

7/29/2019 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/

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