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Design & Prototyping of a Reflective Optical Hybrid Incremental-Absolute Encoder Based on Compact Disc Technology

Sadri, Sobhan | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 40406 (58)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Vossoughi, Gholamreza
  7. Abstract:
  8. The reflective optical rotary encoders are used greatly in automation systems for speed and position measurements. Their approach of reading code as pulses which results in position and speed information is very similar to what a CD-ROM driver performs to read the saved data as pits and lands on the compact disc data layer. Moreover, the micron size of pits and lands in compact disc promise a high-resolution, and low cost rotary encoder based on CD-ROM technology. In this thesis, two concepts of length coding and hybrid incremental-absolute coded discs are proposed. To verify the implementation of these concepts, the rotary encoder set based on CD-ROM technology is designed and tested. It uses both the CD-ROM driver and encoder designed components in one set. The experimental results on a rotating blank CD-R and a coded disc confirm the successful operation of designed rotary encoder. By implementing the conventional incremental disc and proposed coded discs on the CD-R, the designed rotary encoder is used to read these coded patterns. Although this approach of making coded discs imposes incredible limitation on the resolution, results confirms the effectiveness of proposed concepts and verifies that by designing a special coded disc with micron size codes on a circular path, the high-resolution and low cost rotary encoder is achievable.
  9. Keywords:
  10. Reflective Optical Encoder ; Optical Pickup Modeling ; Optical Pickup Identification ; Compact Disk Driver ; Focus Servo Circuit ; Focus Search Circuit

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  • AUTHOR'S DECLARATION
  • Abstract
  • Acknowledgements
  • Dedication
  • List of Tables
  • Chapter 1
  • Introduction
    • Background literature
    • Project Objectives
    • Thesis arrangement
  • Chapter 2
  • Introduction to Encoders, Compact Disc and CD-ROM Drives
    • Incremental Encoders
    • Absolute Rotary Encoders
    • CD-ROM [1,11]
      • Compact Disc
      • Pressed CD-ROM [11]
      • CD-Recordable [10]
      • Optical Pick-up block
      • Photodiode array
      • 2-axes device
      • The Servo Circuits in the CD-ROM
      • Focus Servo Circuits
      • Fine Tracking Servo Circuits
      • The sled servo circuits
      • The Spindle Servo Circuit
      • Compact Disc Encoding
      • Signal Processing
    • Conclusion
  • Chapter 3
  • Model Selection and Reverse Engineering
    • Model selection
    • Reverse Engineering
      • Optical Pick-up
      • CD -Laser Driver
      • PDIC
      • Power Driver IC
    • Conclusion
  • Chapter 4
  • Design of proposed rotary encoder blocks
    • Power Supply
    • 40-pin Adapter
    • Laser Driver IC block
    • Power Driver IC
    • PDIC
    • RF Signal Conditioner
      • Buffers Block
      • Differential Amplifier
      • Inverter Amplifier
      • Low Pass Filter
    • Error Signal Conditioner
    • Focus Search Circuit
    • Focus Servo Circuit
    • Conclusion
  • Chapter 5
  • Design of the Focus Servo Circuit
    • Focus Actuator Modeling
    • Dynamic Disturbances
    • Servo loop
    • CD-ROM Standardized Vertical Deviation
    • PID Controller
      • Offline PID Tuning
      • Implementation of the PID controller for the offline method and the Results
      • Online PID Gain Tuning and Results
    • Phase-Lead Controller
      • Implementation of the Lead Compensator and Results
    • Implementing PIDs and Lead Controllers on the Code Disc
    • Conclusion
  • Chapter 6
  • Implementation of the Rotary Encoders and Code Discs
    • Code Disc
      • Two channel Incremental Code Disc and Implementation Results
      • One Channel Incremental Code with Length Code Concept and Results
      • Hybrid Incremental- Absolute Disc Code Concept and Results
    • Conclusion
  • Chapter 7
  • Conclusion and Future Works
    • Conclusion
    • Proposed Future Works
  • References
  • Appendix A
  • Spindle motor Speed Changer
  • Appendix B
  • PCB Designed Maps
  • Appendix C
  • Codes for focus search circuit and spindle motor speed changer circuit
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