ECT 459

1
ECT 459

• Lecture 8
• Encoder Feedback

2
Encoder Feedback

• Linear
• Absolute
• Incremental
• Both
• Rotary
• Absolute
• Incremental
• Both

3
Encoder Feedback

• Resolutions
• 2 . 32,768 cpr (absolute)
• 2 5 million cpr (incremental)
• Interfaces
• Push-Pull, Open Collector, TTL
• Power
• 5, 8, 10, ..24, 30 VDC
• Output Code Formats
• Gray
• Gray Excess
• Binary
• Binary Coded Decimal

4
Encoder Feedback

• Interfaces
• DeviceNet
• CanOpen
• Profibus
• SSI
• Heads
• Mechanical
• Optical
• Magnetic
• Turns
• Single
• Multi

5
Encoder Feedback

• Shaft Sizes
• Various
• Hollow shaft
• Single or Double-ended
• Applications
• Automatic Storage and Retrieval
• Valve Controls
• Robotics

6
Encoder Feedback

• Sensor Arrays
• The SinCos pickup system is also different from
  conventional encoder systems. The sensitive area
  of the OPTO-ASIC consists of a sophisticated
  sensor array, where individual sensors are
  selectively accessible. The sensor array reads
  complete serial data strings from the barcode
  track.

7
Encoder Feedback

• Code Disk Design
• The small SinCos code disk condenses absolute
  position information into one non-repeating
  circular barcode pattern. A second track with
  analog sine/cosine signals is used to enhance
  resolution and accuracy. Absolute position up to
  15-bit is available upon motor start-up, and any
  time it is requested by the motor drive - such as
  for synchronization.

8
Encoder Feedback

• Single and Multi-Turn Absolute Encoders
• Use single turn encoders when the full range of
  motion in the application occurs within one full
  revolution (360) of the encoder shaft.
  Multi-turn encoders are recommended for
  applications involving multiple revolutions of
  the encoder shaft. In multi-turn encoders, a high
  precision, miniaturized gear train, with a magnet
  on each gear stage, is used to mechanically store
  position information over as many as 4,096 turns.
  The position of each gear stage is determined
  with a pair of Hall sensors. This eliminates the
  need for costly and often unreliable counters and
  battery back up systems. Also, position changes
  that occur while the power is off are
  automatically tracked.

9
Encoder Feedback
10
Encoder Feedback
11
Encoder Feedback

• Wire Draw Encoders
• Encoder integrated with string pot up to 1.67
  kilometers
• Wire draw mechanisms are linear-to rotational,
  industrial motion conversion modules, coupled
  with encoder feedback, to provide cost-effective
  linear position measurement solutions that
  precisely fit your requirements. These systems
  are housed in rugged industrial enclosures, and
  contain a stainless steel or thermoplastic
  composite cable wound on a precise,
  constant-diameter spool. The cable is attached to
  the apparatus whose position is being measured,
  and is extended and retracted as the apparatus
  moves. A spring on the spool maintains cable
  tension. Position feedback is provided by a
  standard incremental or absolute rotary shaft
  encoder. These position transducers allow very
  flexible measuring paths, since the cable can be
  guided around obstacles using pulleys, etc. The
  heavy-duty enclosure of the encoder and spool
  housing provide excellent protection against
  contaminants, shock and other abuses.

12
Encoder Feedback

• Linear Magnetic Tape Encoder
• Consists of a magnetic tape and sensor head. The
  magnetic tape provides the scale for measuring
  systems up to 40 meters long. The absolute
  information is magnetized onto the tape in a
  12-bit sequential code. This position information
  is enhanced by interpolation of sine/cosine
  signals provided by an additional incremental
  track that is magnetized on the tape. The
  magnetic tape is laminated onto a ferromagnetic
  steel strip which is used both as a magnetic
  return path and a dimensionally stable mounting
  aid. The magnetic tape is supplied with an
  adhesive back for mounting by the user. A
  non-contact magnetic sensor with integrated
  electronics is mounted to the apparatus whose
  position is to be measured. As the sensor moves
  over the measuring tape, its position is output
  with a resolution as low as 1 µm over a 16 meter
  range, or 10 µm over a 40 meter range. Position
  data is output via real-time compensated SSI
  (Synchronous Serial Interface), or RS-485. A
  number of parameters such as offset, resolution
  and start points can be configured by the user.

13
Encoder Feedback

• Custom Programmable
• Incremental encoders by SICK Stegmann empower the
  customer to freely program the number of lines
  from 1 to 8,192 and the width of the zero pulse
  using a USB cable and a simple programming
  software tool.
• http//www.stegmann.com/media/drs61.swf