SYNCHRO/RESOLVER CONVERSION HANDBOOK

1 SYNCHRO/RESOLVERCONVERSIONHANDBOOK105 Wilbur Place, Bohemia, New York 11716-2426 For Technical Support - 1-800-DDC-5757 ext. 7771 Headquarters - Tel: (631) 567-5600, Fax: (631) 567-7358 United Kingdom - Tel: +44-(0) 1635-811140, Fax: +44-(0) 1635-32264 France - Tel: +33-(0) 1-41-16-3424, Fax: +33-(0) 1-41-16-3425 Germany - Tel: +49-(0) 8141-349-087, Fax: +49-(0) 8141-349-089 Japan - Tel: +81-(0) 3-3814-7688, Fax: +81-(0) 3-3814-7689 World Wide Web - EDITIONUPDATED 03/2009iiiiiTheSynchro/ resolver CONVERSION Handbookis designed as a practical reference source.

2 It discusses thetheory of operation of data converter products (synchro, resolver , and linear variable differential transformer[LVDT]), performance parameters, and design factors for typical applications. The subject matter and appli-cations are chosen to be those of greatest interest and concern for the designers, systems engineers, andsystems operators with whom DDC has worked over the years. The text treats both DDC s own approach toshaft encoding and other generally accepted techniques. Because various points of view are presented, theHandbookhas served well as a teaching aid over the first Synchro CONVERSION Handbookwas conceived in 1973 during a series of technical seminars con-ducted at DDC.

3 It was the first integrated reference source on SYNCHRO/RESOLVER data after 30 plus years, this hardcopy book is released as an electronic 1968 DDC has been the leader in new product development in the field of SYNCHRO/RESOLVER convert-ers. DDC s introduction, in 1968, of the first modular synchro converters (in a x x inch package)instantly made the existing rack, box, and card-set converters obsolete. Indeed, the biggest sales problemwas convincing engineers that they were able to design complete SYNCHRO/RESOLVER systems using only a fewsmall DDC hybrids.

4 Shortly thereafter, hybrid technology matured and we were able to once again make adramatic size reduction - down to single DIP packages. Now, with the advent of custom monolithic technolo-gy, we are making major advances in functionality and cost (size is more and more being determined by pincount requirements). Today, as in 1968, DDC is still committed to being the leader in synchro conversionand related test equipment. We intend to do this by offering superior products that meet the needs of theengineering community and supporting those products with the best application support world-wide in PAGE INTENTIONALLY LEFT BLANKvTABLE OF CONTENTSSECTION I - FundamentalsAngle-Sensing Transducers.

5 1 Reliability and Functional Stability ..2 Cost ..2 Attainable Performance ..2 Static and Dynamic Mechanical Loading ..3 Environmental Sensitivity ..3 Angle-Data CONVERSION Devices ..3 Fundamental Mathematical Relationships in SYNCHRO/RESOLVER Equipment ..4 Synchro Control Transmitter (Figure ) ..4 Synchro Control Transformer (Figure ) ..5 Control Differential Transmitter (Figure ) ..5 resolver (Figure ) ..5 Transolver (Figure ) ..6 The Scott-T Transformer (Figure ) ..6 Torque Components ..6 Typical SYNCHRO/RESOLVER System Architecture.

6 10 Single-Speed System ..10 Multispeed System ..11 Stick-off Voltage ..13 Digital Data CONVERSION Techniques for SYNCHRO/RESOLVER Systems ..15 Single-RD Phase-Shift Synchro-to-Digital Converter ..16 Double-RD Phase-Shift Synchro-to-Digital Converter ..17 Real-Time Trigonometric Function - Generator Approach ..17 Demodulation, A/D, and P Approach to SYNCHRO/RESOLVER ..18 SECTION II - Theory of Operation of Modern Synchro-to-Digital Converters ..19 The Tracking Converter ..19 Use of a "Synthesized" Reference ..22 Sampling A/D Converters.

7 26 Successive-Approximation Sampling Synchro-to-Digital Converter ..27 The Sampling Harmonic Oscillator Synchro-to-Digital Converter ..29 Multiplexing Synchro-to-Digital Converters ..31 Synchro- or resolver -To-Digital Converters for Two-Speed Systems ..33 Testing S/D Converters ..35 Single Channel S/D or R/D Converter ..35 Multiplexed S/D Converters ..36 Dynamic Testing ..36 SECTION III - Theory of Operation of Synchro-to-DC Converters ..39 Theory of Operation of Synchro- or resolver -to-Linear DC Converters ..39 SYNCHRO/RESOLVER -to-Nonvariant DC Sine/Cosine Converters.

8 40 SECTION IV - Theory of Operation of Modern RVDT/LVDT-to-Digital Converters ..45 RVDT/LVDT Rotary and Linear Variable Differential Transformers ..45 RVDT/LVDT-to-Digital Converter ..45viDynamic Performance ..47 SECTION V - Theory of Operation of Modern Digital-to-Synchro Converters ..49 The Programmed-Function Generator Digital-to-Synchro Converter ..49 Types of Function Generators ..50 The Stored-Table-Lookup Digital-to-Synchro Converter ..52 Output Circuits for D/S and D/R Converters ..52 System Considerations ..53 Power Surge at Turn on.

9 53 Torque Load Management ..53 Pulsating Power Supplies ..53 Thermal Considerations ..53 Passive Inductive Load ..53 Pulsating Supplies ..54 Active Load ..55 Remote Sense ..57 Feedback Transformer ..58 Tuning the Load ..58 Computing Value of Capacitor for Tuning Synchro Stator Windings ..58 Testing D/S Converters ..59 How to Calculate Power Requirements for D/S Converters ..60 Control Transformers and Torque Receiver Parameters ..62 Digital-to- SYNCHRO/RESOLVER Converters ..62 SECTION VI - Other Functions and Instruments ..63 Solid-State Control Transformer (SSCT).

10 63 Electronic Control Differential Transmitter (ECDX) ..64 Isolation and Format- CONVERSION Transformers ..65 Signal Booster Amplifiers ..65 Driving Torque Receiver Loads ..67 Reference Oscillators ..67 Power-Output Transformers ..67 SECTION VII - Measuring and Computing Performance Parameters of Synchro/Digital andSynchro/DC Converters ..69 Worst-Case Error Analysis of Typical S/D Converters ..69 Velocity and Acceleration Errors in Type I and Type II Servos ..71 Type I Converter ..71 Type II Converter ..72 The Relationship between Bandwidth, Tracking Rate and Settling Time for SYNCHRO/RESOLVER -to-DigitalConversion.