ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Linear Optical Encoder Specific

1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Linear Optical Encoder Specific by: Heidenhain Prepared by: Josh Grange Email: joshua.grange@aggiemail.usu.edu 3/11/2010

2. Outline • Reference list • To explore further • Major applications • Basic working principle illustrated • A typical sample configuration in application • Major specifications • Limitations • Types of Scales • How to Choose • Cost • Where to Buy ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

3. Reference list • Heidenhain. (2010). Brochures: Length Measurement - Heidenhain. Retrieved February 20, 2010, from Heidenhain: http://www.heidenhain.com/en_US/services_and_documentation/documentation_information/brochures/ ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

4. To explore further • http://www.heidenhain.com Other Brand: • http://www.farrandoptical.com • http://www.mitsubishi.com ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

5. Major applications • CNC Machine Positioning • Digital Readouts for Position • Measuring and Production equipment in the semiconductor industry • PCB assembly machines • High accuracy machine tools • Precision Machining for Lathes and Mills • Measuring Instruments ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

6. (Heidenhain, 2010) (Heidenhain, 2010) Working Principle Heidenhain encoders with optical scanning incorporate measuring standards of periodic structures known as graduations. These graduations are applied to a carrier substrate of glass or steel (Heidenhain, 2010). Schematic representation of an incremental graduation with distance-coded reference marks. (Heidenhain, 2010) (Heidenhain, 2010) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

7. Working Principle Following illustration is: Photoelectric scanning in accordance with the imaging scanning principle with steel scale and single-field scanning (Heidenhain, 2010). Heidenhain encoders operate using the principle of photoelectric scanning . Photoelectric scanning of a measuring standard is contact-free, and as such free of wear. Heidenhain typically uses two types of scanning principles with linear encoders (Heidenhain, 2010): The imaging scanning principle for grating periods from 10μm to 200 μm. The interferential scanning principle for very fine graduations with grating periods of 4 μm and smaller. (Heidenhain, 2010) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

8. Working Principle Following illustration is: Photoelectric scanning in accordance with the interferential scanning principle and single-field scanning. The interferential scanning principle exploits the diffraction and interference of light on a fine graduation to produce signal used to measure displacement. (Heidenhain, 2010) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

9. Sample Configuration 12’ Horizontal Mill (Base) 12’ Gray Mill Linear Scale ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

10. Sample Configuration In the previous slide the two pictures gave an example of a Heidenhain linear encoder scale in application. This scale ran 60’ in the x direction of the machine and was used to keep linear measurements within one ten thousandths of an inch. In the following picture are the drives used to manipulate and read the encoder signals and the reader head. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

11. Major Specifications • Specifications: • Temperature Range: • -20̊ C to +70 ̊ C • The tapes have different Coefficients of Thermal Expansion that need to be considered • Max Value for Vibration: • 55 Hz to 2000 Hz • Scanning Frequency: • ≤ 98 kHz (max pulse count) • Traversing Speed: • ≤ .75 m/min to 7.6 m/min • The accuracy of the linear measurement is mainly determined by: • The quality of the graduation • The quality of the scanning process • The quality of the signal processing electronics • The error from the scale guide way relative to the scanning unit or head ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

12. Limitations and Considerations Some of the following are limitations or considerations to the linear encoders: • Needs a clean or sealed environment • Do not use force to insert head such as a striking blow to align or seat • Should be mounted as close to the working plane as possible • Need to be mounted on solid part of machine or moving surface • Susceptible to continuous vibrations • Scales and Reader Head should be mounted away from heat and fluctuating temperature • Subject to thermal expansion • Best application in a controlled environment • Length of scale must be considered in which type of reader head and scale material is desired ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

13. Types of Scales Diadur Aurodur Aurodur graduations consists of highly reflective gold lines and matte etched gaps. Aurodur graduations are usually on steel carriers (Heidenhain, 2010). Diadur precision graduations are composed of an extremely thin layer of chromium on a substrate-usually of glass or glass ceramic. The accuracy of the graduation structure lies within the micron and submicron (Heidenhain, 2010). Metallur With its special optical composition of reflective gold layers, Metallur graduations show a virtually planar structure. They are therefore particularly tolerant to contamination (Heidenhain, 2010). ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

14. Types of Scales Magnodur Supradur Graduations manufactured with the Supradur process act optically like three-dimensional phase gratings, but they have a planar structure and are therefore particularly insensitive to contamination (Heidenhain, 2010). Thin magnetically active layers in the micron range are structured for very fine, magnetized graduations (Heidenhain, 2010). Phase Gratings Special manufacturing processes make it possible to produce three-dimensional graduation structures, possessing special optical characteristics. The structure widths are in the range of a few microns down to quarters of a micron (Heidenhain, 2010). ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

15. How to Choose Length of Travel Accuracy Speed of Travel Area for Placement of Reader Head Location of Scale Vibration Temperature Cleanliness Signal Type (Heidenhain, 2010) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

16. Location of ScalesConsiderations for Choosing (Heidenhain, 2010) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

17. Cost Length Accuracy Enclosed Exposed Connection Type Scale Material Reader Type Cost on Linear Glass/Tape Scales: $2,000 - $10,000 (Heidenhain, 2010) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

18. $2,000 Includes: Glass Scale up to 1 meter Accuracy of up to 2 micron One continuous piece (Heidenhain, 2010) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

19. $10,000 Includes: Tape Scale up to 15 meters Accuracy of up to 5 micron Aluminum Extrusions with one continuous tape scale Sealed Positive air displacement (Heidenhain, 2010) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

20. Where to Buy Heidenhain Sales Dept. Address: 333 East state Parkway Schaumburg, IL 60173-5337 Phone: 800-233-0388 Email: info@heidenhain.com ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators