Disclaimer: The information on these pages relates to my professional and personal interests. While work such as the technical papers listed here may have been done while at Agilent/HP, the opinions listed here are my own and are statistically independent from those of my employer. In other words, don't get mad at Agilent if you something I say in here disagrees with you.

Technical Publications (Danny Abramovitch)

Externally Published

As of April 1, 2000, I have been at Agilent Labs. Thus, the work published since then has been largely done at Agilent Labs. In particular the papers on disk drive history and the tutorial on disk drives were done on my own time while I was at Agilent. They are most likely my swan song for the disk drive work. My new work involves a lot of different aspects of high speed measurement systems. One component of these that involves feedback is a Phase-Locked Loop, so one can expect to see some more PLL work show up here (if I'm lucky).

During most of my time at HP Labs, I worked on storage. In particular, I worked on both fixed magnetic disks (often referred to as hard drives) and optical disks (both magneto-optic and DVD+RW). Many of these papers are therefore about hard drives.

The Outrigger: A Prehistoric Feedback Mechanism:
- This paper was presented at a Special History Plenary Session of the 2003 IEEE Conference on Decision and Control and is in the conference proceedings. A later version was published in the August, 2005 issue of the IEEE Control Systems Magazine. The Outrigger: A Prehistoric Feedback Mechanism The significance of this paper is that it shows that the outrigger is a human built feedback mechanism that predates the water clock by at least a millenium. This means that Chapter 1 of a lot of controls books are going to have to change in the next edition. I did almost all of this in the evenings and at lunch time, but I did get a lot of reference help from the Agilent Labs Library.
  
  The conference paper (in Adobe Acrobat format) and a late draft of the CSM paper (in Adobe Acrobat format) are listed. The "final" version of the paper, from the magazine is available from the IEEE web site if one is subscribed to that.
Lyapunov Redesign of Classical Digital PLLs:

The work on the PLL tutorial paper as well as the time I spent simulating PLLs for our jitter measurement project made me realize that I could use Lyapunov redesign on Classical Digital PLLs as well as analog PLLs. The paper itself is part excised tutorial from the PLL tutorial paper and part change of variables from the original Lyapunov Redesign of Analog Phase-Locked Loops paper.
- This paper is scheduled to be presented at the 2003 American Controls Conference, June 5, 2003, and is in the conference proceedings. Lyapunov Redesign of Classical Digital Phase-Locked Loops Both the paper and the slides are listed (in Adobe Acrobat format).
Disk Drive History:
The following two papers are co-authored with my thesis advisor, general role model, and all around good guy, Gene Franklin. Once these papers are published, pre-press versions of them will appear here.
- A brief history of the control systems used in hard disk drives appeared in the June 2002 issue IEEE Control Systems Magazine. A Brief History of Disk Drive Control . A version which is mangled around for to make it easy for the copy editor to work with is found here.
- The original draft had to be substantially reduced to get it into the magazine. Thus, an exerpt from the early portion of the uncut paper provides inisight into the early days of disk drive control. This will be published and presented at the 2002 International Federation of Automatic Control (IFAC) Congress. Disk Drive Control: The Early Days . An extended version of this appeared in the February, 2003 IFAC Anual Reviews.
The first published paper emenating from work at Agilent Labs, the following is on phase-locked loops.
Control Centric PLL Tutorial: : These are different versions of the public paper.
- This is a tutorial given at the 2002 American Controls Conference, May, 2002, and is in the conference proceedings. Phase-Locked Loops: A Control Centric Tutorial Both the paper and the slides are listed (in Adobe Acrobat format).

As of April 1, 2000, I have been at Agilent Labs. Thus, the work published since then has been largely done at Agilent Labs. In particular the papers on disk drive history and the tutorial on disk drives were done on my own time while I was at Agilent. They are most likely my swan song for the disk drive work. My new work involves a lot of different aspects of high speed measurement systems. One component of these that involves feedback is a Phase-Locked Loop, so one can expect to see some more PLL work show up here (if I'm lucky).
During most of my time at HP Labs, I worked on storage. In particular, I worked on both fixed magnetic disks (often referred to as hard drives) and optical disks (both magneto-optic and DVD+RW). Many of these papers are therefore about hard drives.

Disk Drive Tutorial:

This is a tutorial given at the 2001 American 2002 American Controls Conference, June 25, 2001, and is in the conference proceedings. Magnetic and Optical Disk Control: Parallels and Contrasts Both the paper and the slides are listed (in Adobe Acrobat format).

What is DVD+RW based on? Pretty much the high frequency wobble. At least, that's the key technology that makes it different from other formats and allows DVD+RW disks to be readable by most existing DVD ROMS and players. Here are some papers on the subject.

High Frequency Wobble Papers : These are different versions of the public paper.
- This treatment of the subject focuses more on the servo tricks played to improve the performance of the wobbles. It was presented at the 2000 American Controls Conference, June 29, 2000, and is in the conference proceedings. Turning the Tracking Problem Sideways: Servo Tricks for DVD+RW Clock Generation Both the paper (in Postscript or Adobe Acrobat format) and the slides (in Postscript or Adobe Acrobat format) are listed.
- This version of the paper was presented at the 1999 ODS Conference, July 12, 1999, and is in the conference digest. High Frequency Wobbles: A Write Clock Generation Method for Rewritable DVD That Enables Near Drop-In Compatibility with DVD-ROMs Both the paper (in Postscript or Adobe Acrobat format) and the slides (in Postscript or Adobe Acrobat format) are listed.
- A longer version of the paper will appear in the conference proceedings and yet another version may appear in the Japanese Journal of Applied Physics.
A published set of comments entitled Discussion on: `Advanced Motion Control: An Industrial Perspective' by M. Steinbuch and M. L. Norg (in Postscript or Adobe Acrobat format) by Daniel Abramovitch which was published in the European Journal of Control (1998) 4:294-297. The formatting of the text is slightly different in the journal, but the content of the article is identical to the version that I have available here.
Customizable Coherent Demodulator Papers : These are different versions of the public paper.
- This version of the paper was presented at the 1998 ACC, June 26, 1998. Customizable Coherent Servo Demodulation for Disk Drives Both the paper (in Postscript or Adobe Acrobat format) and the slides (in Postscript or Adobe Acrobat format) are listed.
- A longer version of the paper was published in September 1998 IEEE/ASME Transactions on Mechatronics. My draft of this (in Postscript or Adobe Acrobat format) is available here.
PES Pareto Overview (TMRC):I presented this summary of the PES Pareto Method at TMRC 1997 in September. It is entitled: An Overview of the PES Pareto Method for Decomposing Baseline Noise Sources in Hard Disk Position Error Signals . Here are the various pieces of the publication:
- The two page digest in Postscript or Adobe Acrobat format.
- The talk was extremely well received. The color slides of the talk are available in Postscript or Adobe Acrobat format.
- The paper itself appeared in the January 1998 IEEE Transactions on Magnetics. It is available here in Postscript or Adobe Acrobat format.
PES Pareto Papers (ACC): Terril Hurst and I presented papers to the 1997 ACC on the PES Pareto Method.
- The PES Pareto Method: Uncovering the Strata of Position Error Signals in Disk Drives Both the paper (in Postscript or Adobe Acrobat format) and the slides (in Postscript or Adobe Acrobat format) are listed.
- Measurements for the PES Pareto Method of Identifying Contributors to Disk Drive Servo System Errors Both the paper (in Postscript or Adobe Acrobat format) and the slides (in Postscript or Adobe Acrobat format) are listed.
- Decomposition of Baseline Noise Sources in Hard Disk Position Error Signals Both the paper (in Postscript or Adobe Acrobat format) and the slides (in Postscript or Adobe Acrobat format) are listed.
A paper entitled Rejecting Rotational Disturbances on Small Disk Drives Using Rotational Accelerometers by Daniel Abramovitch:
- The paper from the Proceedings of the 1996 International Federation of Automatic Control (IFAC) World Congress in San Francisco, CA (in Postsript or Adobe Acrobat format).
- A slightly edited version also appeared in the November 1997 issue of Control Engineering Practice. The last edit that I made on it before sending it in is available here in Postscript or Adobe Acrobat format.
- There were several versions of the overhead slides. What was presented at the IFAC poster session is available (in Postsript or Adobe Acrobat format).
- Parts of this work form the basis for US Patent # 5663847, noted below.
My thoughts on fuzzy logic. The paper still gets me emails occasionally (most of them friendly).
- A paper entitled Some Crisp Thoughts on Fuzzy Logic (in Postscript or Adobe Acrobat format) by Daniel Abramovitch which was presented at the 1994 American Controls Conference in Baltimore, MD.
- Slides for the talk from the above paper. Some Crisp Thoughts on Fuzzy Logic (in Postscript or Adobe Acrobat format) by Daniel Abramovitch by Daniel Y. Abramovitch. This talk was also presented at the BISC Forum in Berkeley, March 10, 1994. I also have a version with better fonts in (in Postscript or Adobe Acrobat format). This is probably the better version to view since the content is unchanged, but it's easier on the eyes.
Working on HP's 1.3'' KittyHawk disk drive (later abandoned) led to some interesing work on friction.
A paper entitled Disk Drive Pivot Nonlinearity Modeling Part I: Frequency Domain (in Postscript or Adobe Acrobat format) by Daniel Abramovitch, Feei Wang, and Gene Franklin which was presented at the 1994 American Controls Conference in Baltimore, MD.
A paper entitled Disk Drive Pivot Nonlinearity Modeling Part II: Time Domain (in Postscript or Adobe Acrobat format) by Feei Wang, Daniel Abramovitch, and Gene Franklin which was presented at the 1994 American Controls Conference in Baltimore, MD.
A paper entitled A Method for Verifying Measurements and Models of Linear and Nonlinear Systems (in Postscript or Adobe Acrobat format) by Feei Wang, Daniel Abramovitch, and Gene Franklin which was presented at the 1993 American Controls Conference in San Francisco, CA.
A paper entitled The Banshee Multivariable Workstation: A Tool for Disk Drive Servo Research by Daniel Abramovitch which was presented at the 1992 ASME Winter Annual Meeting in Anehiem, CA and was later published in the ASME Advances in Information Storage Systems (Vol. 5, 1993).

An early forray into phase-locked loops.
A paper entitled Lyapunov Redesign of Analog Phase-Lock Loops (in Postscript or Adobe Acrobat format) by Daniel Abramovitch which was presented at the 1989 American Controls Conference in Pittsburg, PA and was later published in the IEEE Transactions on Communications (Vol. 38, No. 12, December 1990).
A paper entitled Identification of Sampled Data Systems at Frequencies Beyond the Nyquist Rate by Rick Ehrlich, Carl Taussig, and Daniel Abramovitch which was presented at the 1989 IEEE Conference on Decision and Control in Tampa, FL.

Patents
- The following was issued May 21, 2002.: US Patent # 6393596: Missing Pulse Detector Using Synchronous Detection. This was a proposed method for encoding addresses into high frequency wobbles for DVD+RW. The idea was to have some wobbles missing and that the position of the detected missing pulse. This was an effective and intriguing idea, but we could never get it past our partners at Philips, so it was not part of the current implemented DVD+RW format. Note that unlike most of these, I had a minor role on this patent. The chief inventors were Mike Fischer and Josh Hogan. Other inventors included Terril Hurst and Carl Taussig.
- The following was issued April 4, 2000.: US Patent # 6046968:Re-Writable Optical Disk Having Reference Clock Information Permanently Formed on the Disk. This is the high frequency wobbles patent, which directly led to the DVD+RW format. In November, 2001, those members of the project team that were still at HP Labs were given the Joel Birnbaum Prize, the highest internal award given by HP Labs. The idea first came to me back in September of 1996, when I first joined the project team. However, it sat for a few months, and was only made practical by the considerable knowledge of optics by my co-inventor, David Towner.
- The following was issued June 1, 1999. The application was filed May 30, 1997 and was allowed in ???: US Patent # 5909661:Method and Apparatus for Decomposing Drive Derror Signal Noise Sources. This is the PES Pareto Patent. The work is summarized below, and was be published at the 1997 American Controls Conference, The Magnetic Recording Conference (TMRC) 1997, the and in the January 1998 IEEE Transactions on Magnetics. Reports are that this method is in widespread use throughout the disk drive industry, or at least what is left of it. My co-inventors on this were Terril Hurst and Dick Henze.
- The following was issued September 1, 1998. The application was filed May 28, 1996 and was allowed in September/October 1997: US Patent # 5801895:A Disk Drive Servo Demodulation System Which Suppresses Noise on the Position Error Signal. This is the customizable, coherent servo demodulation patent, and was published at the 1998 American Controls Conference and in the September 1998 IEEE/ASME Transactions on Mechatronics.
- The following patent was issued September 2, 1997: US Patent # 5663847: Rejection of Disturbances on a Disk Drive By Use of an Accelerometer This patent deals with removing the effects of external shock and vibration from a disk drive by using an accelerometer signal in a multi-rate, adaptive algorithm.
- The following patent was issued in August of 1995: US Patent # 5446648: Determination of Open Loop Response from Closed Loop Measurements This patent deals with extracting open loop responses from closed-loop measurements of multivariable systems. My co-inventor on this was Carl Taussig.

Technical Publications (Danny Abramovitch)

Externally Published

Patents