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Screen shot #12 (Merely a picture to illustrate that our GUI is totally self-explanatory) Click here to go to our overview of Atmospheric Models. Click here to go to our discussion of Robust Control Topics. Click here to go to our relevant Anagrams and Palindromes. Dr. Paul J. Cefola, the expert referenced above, has a consultancy in Sudbury, Massachusetts: cefola at comcast.net.
With Prompters_On, we are less diplomatic and say what we really think (and can back-up)! Work on Robust Control over a decade and a half by the mid 1990's could merely handle Linear Time Invariant (LTI) systems with no nonlinearities, no time-varying parameters, and no noise disturbances present. The only disturbance Robust Control could handle successfully was a persistent constant bias offset. The real world is nonlinear and, even when locally linearized, it is usually properly modeled as being time-varying in general. One prominent Laboratory for Information and Decision Systems (LIDS) formulation at MIT for Robust Control (Lopez, J. E., Athans, M, On Synthesizing Robust Decentralized Control, American Control Conference, 1994-TK7855.M41.E3845 no. 2197 at Barker Library at MIT) requires that the system state dimension, the number of components of the output measurements, and the number of components of the control all be of the same exact dimension in common as well as the system being just LTI. This formulation is not very realistic (as an understatement since most systems will not exhibit these characteristics). Yet TK-MIP still reports here on the best that TeK Associates has found that: (1) heroically handles one scalar nonlinearity in an otherwise LTI system; (2) heroically handles one scalar time-varying parameter in an otherwise LTI system; and (3) heroically handles one scalar noise component in an otherwise LTI system. Apparently, none of these Robust Control formulations can yet handle all three of these situations simultaneously [in the mid-1990's]. Therefore Robust Control is evidently a much less capable methodology than what can be routinely handled in a straightforward manner within existing standard prior state variable formulations. LTI is needed to apply the Robust Control methodology since the new toy for these analysts, consisting of left and right lambda matrix factorizations, are performed in the frequency domain. By being so very conservative (in a minimax sense) by how Robust Control handles system control aspects by single-mindedly focusing on the worse case system characteristics and then by trying to do the best it can with the worse aspects, the subsequent system response is typically very, very sluggish! Few real applications can tolerate such unpleasantly slow response characteristics except, perhaps, in process control. This limited applicability should be emphasized more in the Robust Control literature as a standard disclaimer to the unwary. To date, this has not happened. TeK Associates is aware that, in 2009, there were about 40 books by different authors on how to apply Robust Control to applications. In our opinion, if the only objective is a ticket to a technical conference to present a paper on the subject, then this topic is germane. If the objective is to solve real-world problems in a timely manner with realistic resources (as historically had been the goal), then perhaps use of Robust Control is not the path to follow. (TeK Associates has even actually overheard [in a public forum prior to the speaker going to participate in a crew event that weekend at The Head of the Charles Regatta (at Harvard University but the meeting where this event took place was not at Harvard)] this visiting Robust Control and Intelligent Control researchers flim-flam artist-like response to project funders at the end of the rainbow (to allow the researcher to save face): Oops, the resulting solution is, unfortunately NP-hard, and therefore not tenable. Sorry!, as he rehearsed and broadcast as a shout out for others to use as well in similar situations or circumstances. Talk about biting the hand that feeds you! Is this not welfare for Ph.D.s? In a bygone era, control theorists used their considerable intellect to actually improve the world. Who, with undue or unwarranted influence, lead them so far astray? Fortunately or unfortunately, TeK Associates thinks it knows the answer. What was muttered in antiquity at the walls of Troy, at the sight of the large wooden horse?
(The above cartoon refers merely to one particular person at MIT and not to a group or class) With the apparent current lack of technical integrity and adequate oversight in a closed club, is it any wonder the U.S. is in its current predicament? [Well that pretty much proves that I have the jaw bone of an ass.... Now all I need to do is to let my hair grow longer and find a Delilah. Finding one shouldn't be too hard since so many of them abound.]
I need to properly acknowledge the research team that was able to accomplish Robust Control solutions via the above cited "heroic" methods: within a 2 year MIT Lincoln Laboratory funded IR&D contract that was performed ~1991 by Dr. Appa Madiwale (MIT Lincoln Labatory) and consultant Prof. Lena Valavani (MIT).
At the 1992 (or was it 1998?) Conference on Decision and Control, a Robust Control Design Challenge was levied, and several investigators rose to the challenge and submitted abstracts promising solutions to be presented at the subsequent years Conference on Decision and Control. The authors who planned to participate with their solutions looked like a whos who in modern control. Despite the simplicity of the low dimensional example comprising the system to be designed for robust control, every anticipated presenter has a void in the proceedings of this subsequent years conference where the promised solutions should have appeared. What an embarrassment! This should have been a reality check early on regarding problems with the robust control methodology. Although the late George Zames is credited in a moving (and extremely informative) tribute
by MIT Prof. Sanjoy Mitter on pp. 590-595 in the May 1998 issue of
IEEE Trans. on Automatic Control with, essentially, single-handedly bringing mathematical functional analysis to the aid of control and system theory via use of the
contraction mapping principle (CMP) in Zames, G., Feedback and Optimal Sensitivity: model reference transformations, multiplicative semi-norms, and approximate
inverses, IEEE Trans. on Auto.
Contr., Vol. 26, pp. 744-752, Apr. 1981. (see Bensoussan, A., Stochastic Control by Functional Analysis Methods, Vol. II, North-Holland Publishing, NY,
1982 and see Kreyszig, E., Introductory Functional Analysis with Applications,
John Wiley & Sons, NY, 1978), please peruse the earlier contribution by Jack M.
Holtzmans (Bell Telephone Lab., Whippany, NJ) Nonlinear System Theory: A Functional Analysis
Approach, Prentice-Hall, 1970, which also has the use of CMP as its main theme in such systems. However, Holtzman worked everything out in detail in
the above cited book so that his results were on a platter in such a form that they could be easily understood and conveniently applied immediately to practical system design by engineering readers faced with real applications and who may not necessarily be interested in abstract results in a technical paper whose significance is not known until several years later. Charles
Desoers and M. Vidyasagars (U. C., Berkley) textbook came out several years earlier than Zames too and also had a functional analysis bent. A. V. Balakrishnan (UCLA) has also been an avid practitioner of functional analysis in analyzing the behavior of systems and in understanding optimal control (including
his contributions to numerical solution algorithms) since the early
1960s. There is even another precedent for utilizing a contraction
mapping to converge to the fixed point solution in:
Kerr,
T. H., Real-Time Failure Detection: A Static Nonlinear Optimization
Problem that Yields a Two Ellipsoid Overlap Test, Journal of
Optimization Theory and Applications, Vol. 22, No. 4, pp. 509-535,
August 1977.
Again for MIT, the well-known Not Invented Here ("NIH")
syndrome seems to be at play (i.e., only cite work from people affiliated with MIT in some way and
ignore the rest even if they had priority in their results). With this, I keep
my personal promise to the late Dr. Harold Chestnut, VP at General Electric in
Schenectady, NY in the early 1970s, to be vigilant on these issues
(see Chestnut, H., Bridging the Gap in Control - Status 1965,
IEEE Trans. on Automatic Control, Vol. 10, pp. 125-126, Apr. 1965 [and evidently still a problem today if not more so]).
Also see more about Dr. Harold Chestnut in: http://dictionary.sensagent.com/Harold%20Chestnut/en-en/
, https://www.youtube.com/watch?v=Ln9pR1xxB0A
, https://www.youtube.com/watch?v=eyqaBaOrM8g In our opinion, if Control Theorists were actually interested in implementing a
Robust Control, they would embrace the work of the IEEE Reliability Society
(as it has evolved since the end of WWII) by also viewing the problem at a higher level involving the same constituent components participating within the principal path of implementing the solution
and also utilize:
An example on how to handle such considerations is found in: Kerr, T. H., Failure Detection Aids for Human Operator Decisions in a Precision Inertial Navigation System Complex, Proceedings of Symposium on Applications of Decision Theory to Problems of Diagnosis and Repair, Keith Womer (editor), Wright-Patterson AFB, OH: AFIT TR 76-15, AFIT/EN, Oct. 1976, sponsored by Dayton Chapter of the American Statistical Association, Fairborn, Ohio, June 1976. For failsafe or Fault-Tolerant computer capabilities, look to
Stratus Computers (now Stratus Technologies with its [Virtual
Operating System-VOS] and EMC https://www.delltechnologies.com/en-us/index.htm?gacd=9650523-1073-5763017-266683695-0&dgc=st&msclkid=911afd35b7811b5d0e39a256c5dc0dab&gclid=COPC7oKz8OsCFULxswodhf0OuQ&gclsrc=ds) Robust Control methodology (apparently a "new toy" of control theorists
in the last 30 years is evidently of limited applicability in practice since Robust Control implementations have a sluggish response that few applications can tolerate other than those in the process control industry and even then this theory is stymied by presence of nonlinearities, time-varying parameters, or noises). While I am not intimidated by measure theory, nor by Lebesgue integrals in rigorous probability theoretic considerations, nor by other stochastic integrals such as that of Ito or Stratonovich or MacShane, nor by exotic norms in a Banach Space nor exotic inner products in a Hilbert Space, I fail to see any enticing overriding lure of Hardy spaces, and especially H∞ for control and/or estimation. I am satisfied and happy with L1 or L2 convergence or other Lp spaces, and conjugate exponents: 1/p + 1/q = 1 for related pairs of Lebesgue integrals, L∞, and Essential Supremum. I am definitely not impressed by "Robust Control" and all its apparent pretensions. However, some useful motivation for its use is provided here: https://en.wikipedia.org/wiki/Hardy_space and, subsequently or consequentially, here: https://en.wikipedia.org/wiki/Control_theory. Notice that the language is indeed that of "process control": slow and steady wins the race as in the story of the "Tortoise and the Hare" (so I did not exaggerate in my earlier criticism of Robust Control or H∞ estimation as having an inherently sluggish response similar to the characteristic response of an "over damped" system rather than to the preferred "critically damped" 2nd order LTI system that does not exhibit ringing oscillations nor overshoot but quickly and smoothly goes to the final target state in response to the most recent set-point value submitted). While we understand that Lp spaces have pathologies when p < 1, that Hp spaces don't exhibit when p < 1 (useful for further mathematical analysis but not related to Control Theory applications [even for process control], we are less enthusiastic concerning use of Hp spaces for practical engineering applications). For the inner and outer loops of Fighter Aircraft guidance and control, several generations of linkages have evolved since Generation 1: pneumatic linkages and mechanical levers to exercise control actuators; through Generation 2: fly-by-wire (electrical cables) to exercise control actuators; to Generation 3: fly-by-light (i.e., fiber optic links) to exercise control actuators. Fiber optic cables would previously be bleached and turn cloudy (interfering with successful communications transmission) upon exposure to a nuclear environment unless they were doped with a "Halide" such as fluorine. There are now more modern solutions to that historical problem. M. G. Safonov and M. K. H. Fan, eds., Special Issue on Multivariable Stability Margin.
INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, VOL. 7, 97103 (1997). Kevin A. Wise, Bank-to-turn missile autopilot design using loop transfer recovery, AIAA Journal of Guidance, Control, and Dynamics, Vol. 13, No. 1, pp. 145-152, Jan-Feb. 1990. Christopher I. Marrison and Robert F. Stengel, Design of Robust Control Systems for a Hypersonic Aircraft,
AIAA Journal of Guidance, Control, and Dynamics, Vol. 21, No. 1, pp. 58-63, Jan-Feb 1998. We at TeK Associates are optimistic about the status of control theory in general and we are enthusiastic about:
To complete the expose started above, recall the creatively designed endeavor below which featured a multiple model bank of N Kalman filters in parallel with an LQ feedback regulator control law for each Kalman filter equipped feedback branch after which the aggregated net result of the particular scalar weightings consisting of the individual probabilities, as calculated on-line in real-time, and corresponding to any particular branch of the LQG being correctly associated with the present mode (of only N different possible modes being modeled) for the actual multi-mode system under consideration: Athans, M., Castanon, D., Dunn, K.-P., Lee, W. H., Sandell, N. R., Willsky, A. S., The Stochastic Control of the F-8C Aircraft using a Multiple Model Adaptive Control (MMAC) method - I: Equilibrium Flight, IEEE Trans. on Automatic Control, Vol. 22, No. 5, pp. 768-780, Oct. 1977. Was non-equilibrum flight ever considered or handled (where non-equilibrium flight is take-offs and landings and dog fight maneuvers or even maneuvers as benign as just coordinated turns)? Did this approach actually work? Was there ever a Phase II follow-on thus indicating success of the particular approach? The answer appears to be no on all three counts. This constitutes a high profile publicity stunt or charade without any useful payoff to the NASA customer. This was business as usual in some circles! I definitely would like to chase the money changers from the temple (of learning and useful knowledge). If they had not been pretending so hard that LQG theory was not fatally flawed, they could have equipped each LQG leg with a stable replacement LQG/Loop Transfer Recovery, as its correction. The resulting redesign may now actually work as they had hoped the initial version would. Perhaps the funniest situation was when several people complained that the IEEE TAC paper review system was, perhaps, apparently being abused by reviewers or assistant editors being the first to see and then recognize a significant new result and then dispatch a graduate student (among an ample pool of available talent) to either use the topic of the paper under review as their thesis or write a paper on the topic themselves and then submit it for publication even before the original paper had appeared in print for the first time (a process that took about two years in those days). Afterwards, people at a particular institution would just reference the work of the authors affiliated with the same institution and ignore the true originator (who should have been acknowledged as having had the precedent) as yet another example of the "NIH" syndrome. What was funny was who was on the two man committee: Prof. Michael Athans and Prof. Y.-C. "Larry" Ho [one who almost always indulged in "NIH" behavior and the other who didn't and was known for his steadfast integrity, respectively] to look into the possible problem and who jointly reported their conclusions that everything regarding the current IEEE TAC review process was just fine! Isn't that particular situation like having the fox guard the chicken coop? In the old days (1970's and, perhaps, before), in order for a Navy
Sea Hawk SH-60 helicopter to land on a ship's deck during
high winds and a corresponding "high sea state", it would drop a strong
steel cable that would be attached to a winch aboard ship. Then the helicopter would pull
up against the cable to make the cable taught as the winch reeled it in. In that way, the helicopter would perfectly match the ship's motion on roughest of
seas as it landed. RAN MH-60 Helicopter RAST Recovery Assist Explained: One further example: I am not accusing all of MIT of practicing "NIH" but am only complaining about the inner workings of one particular department that I am very familiar with: Electronic Systems Laboratory (ESL), which changed its name to Laboratory for Information and Decision Systems (LIDS). My complaint is only for a particular time epoch from the late 1960's until some aspects of the present and does not include or apply to everybody working in this department, nor to the students who graduated from this department; but merely to the "trickster" at the top for many of those years [who was also a brilliant teacher and insightful researcher with extensive breath and depth and an ability to communicate ideas simply and clearly so that ALL could understand]. (My own [115] was based on some of his earlier work.) However, in the 1990's, he even told his graduate students in class (which I overheard, as an outside member of the audience) how he handled the following situation: "One of my prior students, who had already graduated and was now working in industry, in seeking to apply some aspect of my prior published technique to a particular application in seeking to apply my earlier results to but then, unfortunately, encountered a problem in taking it to fruition in the manner expected. This graduate, now in industry, successfully persuaded his supervisor to finance a consulting visit for me to help resolve the problem and help them get over the perceived temporary hurdle. While there on location, I sought a private audience with my prior student's supervisor from whom this employee, got that consulting assignment for me; I told his supervisor that he "was not the sharpest knife in the drawer"!" Again, biting the hand that feeds him! Paying back an act of kindness by throwing his former student "under the bus". Prof. Michael Athans' meaning was clear: "If you bother me with some theoretical aspect or "wrinkle" associated with the material of this course after you leave here, I will do the same thing to you!" Usually, subsequent consulting work on the same topics and material already known and conveyed in prior classes on the subject is viewed as an opportunity to be a hero and "save the day" for its industrial application! It's a pity that Prof. Athans, apparently, did not view it that way. Perhaps later in life, he was merely too busy and did not want to interrupt what he was working on at the time. I will remember the fun times (e.g., at several meetings of the CDC in New Orleans, as he crossed Canal Street, with an impish grin on his face, and as he proceeded down Bourbon Street with Sol Gully [https://www.linkedin.com/in/sol-gully-4779a326] to take in some of the many performances there). Prof. Athans had a very colorful personality. He will indeed be missed! We at TeK Associates consider ourselves to have been extremely lucky for over more than forty years by our employers being in convenient proximity of two major educational institutions of higher learning where outstanding leaders in control theory taught; and who allowed us to attend important outside lecturers and presentations for free at both Harvard University (where Y. C. "Larry" Ho allowed us to hear but not ask questions nor make comments) and MIT (where we were allowed to ask probing questions). We also had library cards at both institutions, which greatly aided our research into these subjects. Weekly attendance at TASC "White Noise Hours" also provided us with experience more encompassing than our own mere first-person experience because we benefited from direct cross-corroboration with others who had different challenges. I also frequently used the Engineering and Science Library at Boston University, the Snell Library at Northeastern University, the Air Force Geophysical Library at Hanscom Field AFB (which became the Phillips Library) before it all moved to Albuquerque, New Mexico, the Lincoln Laboratory Library while I was working there, and the MITRE library in Bedford, MA (while I was consulting there) before it was dismantled in the early 2000's to be merely a "shadow of its former self". Another variation of sorts of the dreaded NIH syndrome, discussed above, occurs in the following:
where no reference is made to the following prior publication on this Cramer-Rao Lower Bound topic:
yet several of the references cited in the above papers by Stephen Smith (of the Lincoln Laboratory of MIT) do, in fact, reference the above Kerr article as a significant historical precedent in the Cramer-Rao Lower Bound topic area that was published in a different IEEE Journal even though Kerr was in fact an employee of Lincoln Laboratory when his paper was published but is no longer (for good reasons such as this). Substantiation of its significance may be found on page 9 in: Branko Ristic, Cramer Rao Bounds for Target Tracking, International Conference on Sensor Networks and Information Processing, 6 Dec. 2005.
No there is not a new sheriff in town since THK III has pretty been here and on station all along with eternal vigilance since 1971: Making a list and checking it twice---trying to find out whos naughty or nice....
Explanations pop-up instantaneously where you need them but only when requested, as seen below for the single button appearing on the screen above. An exception is if the USER sets Prompters_On as an option that can be activated from the Menu Bar appearing on most of the primary Screens. When Prompters_On is set, many of the informational screens open automatically when that screen is visited as a helpful mnemonic device. This feature is especially useful when a substantial period of time elapses between TK-MIP activation as other tasks are being pursued. No user manual is ever necessary to feel comfortable and confident in running TK-MIP. This prompting does not make use of the Internet. Otherwise TK-MIP could not be run in a secure stand-alone CLASSIFIED mode. The close (equivalent) model relationship between a Box-Jenkins time-series representation and a state variable representation has been known for a least 4 or 5 decades, as spelled out in: A. Gelb (Ed.), Applied Optimal Estimation, MIT Press, Cambridge, MA, 1974.
Update: Now 50 years of experience with Kalman Filter applications and he is an IEEE Life Senior Member and an Associate Fellow of the AIAA in GNC and a Member of SPIE. https://spie.org/profile/Thomas.KerrIII-2982?SSO=1
Please click on http://filext.com/file-extension/TEK for free ways to check your Window's registry for compatibility with TK-MIP and its ability to automatically access the various file extensions that it needs to access (as representatively sampled in the file view above) in order that TK-MIP work properly without conflict after it is installed.
Please click on http://filext.com/file-extension/TEK for free ways to check your Window's registry for compatibility with TK-MIP and its ability to automatically access the various file extensions that it needs to access (as representatively sampled in the file view above) in order that TK-MIP work properly without conflict after it is installed.
Sh, Tom sees moths. Are we not drawn onward to new era? To Idi Amin. I'm a idiot. Splat! I hit Alps. Norma is as selfless as I am, Ron. radar racecar
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