Science topic

Observer - Science topic

Explore the latest questions and answers in Observer, and find Observer experts.
Questions related to Observer
  • asked a question related to Observer
Question
8 answers
I want to use Kalman filter to estimate battery parameter and observer for state estimation together (SOC)
Relevant answer
Answer
This problem has been studied in the control theory community at least since the 70s. You can start with Prof. Ljung's famous paper:
Also, I would also consider subspace identification methods for estimating the model. By using the subspace identification method you can "only" estimate the system state-space model up to unknown similarity transformation. However, the estimated model can still be used for control.
  • asked a question related to Observer
Question
20 answers
The measurement problem in quantum physics shows that an observer can manipulate the outcome of experiments studying the behaviour of light (Young, 1802 double-slit experiments) and control whether light will manifest as a particle or a wave (Bohm, 1952; Cho, 2017; Kocsis et al., 2011). This shows that consciousness may be compatible with light or may be able to communicate with light (Kroeker, 2019). I was wondering if consciousness could be quantized if the observer effect experiments were reversed engineered to measure the behaviour of consciousness, rather than the behaviour of light?
Discuss...
Relevant answer
Answer
Anything in the Multi-Universw can be quantized and both continuized.
  • asked a question related to Observer
Question
20 answers
Why isn't the velocity of light given by the speed of the observer plus the speed of the light (addition of velocities)?
Why does the light ray slow down and compensate or speed up and compensate for your motion, so that it is always travels at the speed of light? notwithstanding your motion?
In short, what is the mechanism that means the velocity of light always remains the same, irrespective of the motion of the torch issuing the light ray?
Relevant answer
Answer
Thank you very much for your kind invitation to answer this question. My gratitude.
The principle of light speed invariance is obtained by solving Maxwell's equations simultaneously, and is confirmed by Michelson Morey experiment.
And Special Relativity Theory take the principle of light speed invariance as one of its basic postulates and deduced many valuable conclusions.
In my humble opinion inside this article:
A DISCUSSION ABOUT THE NATURE OF TIME
https://doi.org/10.5281/zenodo.7079721 Light propagation in medium, such as water, crystal, vacuum, etc, but not in the void(Vacuum is not void, vacuum are filled with gravitational fields and gravitational fields are physical existence. Thus vacuum is full but not empty).
Therefore, the speed of light depends on the medium, but irrespective of the motion of the torch issuing the light ray.(if light travels in water, it is multiple medium, water plus gravitational field, so it might be more complicated?)
inside this article, I wrote, light does travel in ether,
"ether should be gravitational fields. This is logical because it is known to all that vacuum gravitational fields, in which light can travel, can interact with electromagnetic wave and can bend light, as transparent crystal, in which light can also travel, can also interact with electromagnetic wave. That’s why, when we measure light speed on the surface of the earth, the light speeds are the same in every direction, because light travels at the same speed in the same gravitational fields"
Just for your kind reference.
BR
  • asked a question related to Observer
Question
1 answer
Is the -apparent- progress of light, along the left and right-hand limbs, different for different observers?-- in the standard arrangement for the Relativity of Simultaneity, as suggested by the animation in "apparent pogress.docx" .
And if so, just considering the right-hand limb, why can't we place an event E, such that, for one observer the light has already reached and enveloped it, while for another observer, the light has yet to reach it, -- as viewed by these two different observers?
Relevant answer
Answer
In the "apparentprogress__.docx" attached above, it is to be noted that we have two cases : an observer stationary with the plank of wood, and an observer moving uniformly to the left with respect to the plank of wood.
These are the two frames discussed.
-----------------------------------------------------------------------
The reason why the light rays issued from the left and right ends of the plank of wood must meet in the middle, as shown in the animation, is only obvious when one considers an event placed in the middle that might be triggered only by the arrival of BOTH light rays at that one place at the same time, say as viewed by the stationary observer.
And so for the observer moving uniformly to the left, or any other observer for that matter, that same event would also have to triggered, or we would be left with two realities. That event can only trigger if, in all these other frames, the light arrives at the same place (in the middle) at the same time.
This is why the light must hasten along one limb, and lag along another, as viewed by the observer moving uniformly to the left, in order to reach the middle of the plank of wood "on time" so to speak.
This reality requirement for this standard setup is discussed here:
A Discussion on the Relativity of Simultaneity
October 2021
Xinghong Wang
We don't agree with the conclusion in Wang's paper, that “The relativity of simultaneity is not a valid theory". All that is demonstrated here, is that the light must reach the middle in all frames (which is does in our animations).
  • asked a question related to Observer
Question
4 answers
Is the -apparent- progress of light, along the left and right-hand limbs, different for different observers?-- in the standard arrangement for the Relativity of Simultaneity, as suggested by the animation in "apparent pogress.docx" .
And if so, just considering the right-hand limb, why can't we place an event E, such that, for one observer the light has already reached and enveloped it, while for another observer, the light has yet to reach it, -- as viewed by these two different observers?
Relevant answer
Answer
In the "apparentprogress__.docx" attached above, it is to be noted that we have two cases : an observer stationary with the plank of wood, and an observer moving uniformly to the left with respect to the plank of wood.
These are the two frames discussed.
-----------------------------------------------------------------------
The reason why the light rays issued from the left and right ends of the plank of wood must meet in the middle, as shown in the animation, is only obvious when one considers an event placed in the middle that might be triggered only by the arrival of BOTH light rays at that one place at the same time, say as viewed by the stationary observer.
And so for the observer moving uniformly to the left, or any other observer for that matter, that same event would also have to triggered, or we would be left with two realities. That event can only trigger if, in all these other frames, the light arrives at the same place (in the middle) at the same time.
This is why the light must hasten along one limb, and lag along another, as viewed by the observer moving uniformly to the left, in order to reach the middle of the plank of wood "on time" so to speak.
This reality requirement for this standard setup is discussed here:
A Discussion on the Relativity of Simultaneity
October 2021
Xinghong Wang
We don't agree with the conclusion in Wang's paper, that “The relativity of simultaneity is not a valid theory". All that is demonstrated here, is that the light must reach the middle in all frames (which is does in our animations).
  • asked a question related to Observer
Question
2 answers
If we are to correct the long-range action of the global inertial frame of Newtonian mechanics, shouldn't we make it the close action of the relative velocity of light?
Relevant answer
Answer
Shinsuke Hamaji The thought experiment linked below shows that the postulates of Special Relativity cannot be maintained and the Lorentz transformation of coordinates has to be discarded:
link
Then the postulates of special relativity are replaced with the concept of a space rest frame.
link
The conclusion is that distance is invariant between moving frames of reference but objects experience length contraction depending on their velocity v relative to the space rest frame K0.
Richard
  • asked a question related to Observer
Question
4 answers
The Hawking temperature $T_h$ is proportional to the surface gravity $\varkappa$ which, in spherical-symmetric case, one calculates on the Killing horizon. This temperature is very small but where? at infinity? Then if we use the formula $T\sqrt{g_{00}}=const$ then, one obtains infinity temperatures near the event horizon. Help me with this question please. I thought that one measures $T_h$ near the event horizon and the temperature near the horizon is small. Or my opponents are right and this temperature is measured in infinity?
Relevant answer
Answer
No, it's not like the early universe (a black hole's event horizon is a future horizon, not a past horizon).
Yes, the formula isn't universally valid, for, among other reasons, because the components of the metric aren't observable quantities-they're gauge fields. The Hawking temperature makes sense as an observable at infinity-assuming that the spacetime is asymptotically flat there.
  • asked a question related to Observer
Question
2 answers
I am working on observer based active fault tolerant control( Fault detection and isolation (FDI) scheme) for handling sensor faults in a system. The system has also a dynamic disturbance component also which is difficult to have a proper observer design to design the FDI of the FTC scheme. I would like to know the effective methods to handle such situations with observer based FTC schemes. How to handle the issues of disturbance modelling and threshold selection in such schemes? Also what could be the limitations for such schemes?
Relevant answer
Thank you for the response Rim Hamdaoui. I would definitely look into the resources suggested by you.
  • asked a question related to Observer
Question
2 answers
Apropos: the Andromeda paradox.
Can anyone tell me which of the below, if any, describe the arrangement in the Andromeda paradox?
For event 1 I am assuming this to be 'the decision' to launch the fleet, and for event 2 I am assuming this to be a later event signifying that the 'fleet is deployed'. Event 2 occurs after event 1, of course, for the Aliens.
According to the paradox, the light from these events reaches the observers in such a way that event 1 is seen first by one observer, and while event 2 is seen first by the other observer?
If that is what the paradox is saying, can anyone explain (ideally with an animation or a picture) how this happens?
Relevant answer
Answer
Cf. full answer attached.
CW1 = Discussion. Special Relativity and Determinism. C. W. Reitdijk
CW2 = A Rigorous proof of determinism derived from the Special Theory of Relativity - C. W. Reitdijk
  • asked a question related to Observer
Question
1 answer
Apropos: the Andromeda paradox.
Can anyone tell me which of the below, if any, describe the arrangement in the Andromeda paradox?
For event 1 I am assuming this to be 'the decision' to launch the fleet, and for event 2 I am assuming this to be a later event signifying that the 'fleet is deployed'. Event 2 occurs after event 1, of course, for the Aliens.
According to the paradox, the light from these events reaches the observers in such a way that event 1 is seen first by one observer, and while event 2 is seen first by the other observer?
If that is what the paradox is saying, can anyone explain (ideally with an animation or a picture) how this happens?
Relevant answer
Answer
Cf. full answer attached.
CW1 = Discussion. Special Relativity and Determinism. C. W. Reitdijk
CW2 = A Rigorous proof of determinism derived from the Special Theory of Relativity - C. W. Reitdijk
  • asked a question related to Observer
Question
4 answers
How to calculate the gain matrix of Luenberger /state observer?and also what is the role of eigen values during the mathematical modeling?
The current system have 2 input and 2 controllable states. The system is observable.
Relevant answer
Answer
Hi Habib,
if your system has a single output, I believe you can use Ackermann's formula (acker in Matlab, use the dual property for observers). In this formula you have to provide a polynomial whose roots are the eigenvalues you want. As for the choice of the eigenvalues the basic rules are: 1) the should be faster (2 to 4x) than the closed-loop intended, that is faster than the eigenvalues resulting from pole-placement, 2) but the faster they are the wider will be the passing band of the system and if you have noise, that could be an issue.
Regards.
  • asked a question related to Observer
Question
1 answer
We have developed an arrangement in the Relativity of Simultaneity framework that must be wrong, as we cannot have a situation where two events, situated at the same place (event E, and an arrival of light event) are switched in time-order, for two different observers moving uniformly (or non-uniformly) relative to these events.
Is it that the placement of event E in animation Figure 4 is somehow not allowed?
Is it that it is not always possible to make two events separated in space simultaneous? by suitable choice of the motion of the observer? (cf. Einstein's train gedenken experiment.)
If anyone can pinpoint the error, much appreciated.
Vide : "Short Precis" below for desciption of new arrangement and animations.
See also question:
Relevant answer
Answer
The 4 main problems of special relativity: ~^~
1 Motivational deviation
Deviating from the tasks of the laws of physics, attempting to replace physics with mathematics;
2 method contradictions
Saving the ether should solve the problem of the electromagnetic ether, but modifying the Galileo transformation is a contradictory method;
3 Assumptions violate experience
Invariance of the speed of light violates the general experience of relative speed and denies the foundation of physics;
4 Difficult to observe and infeasible to verify logic
The laws of physics cannot be proven, only falsified. Efforts to seek proof with a small number of low-confidence observations are logically infeasible. In fact, the magnitude of the acceleration of the Spaceborne Atomic Clock time is much greater than the predicted value of the time delay.
Here are some empirical discussions on the relative speed of light, looking forward to your valuable criticism. ~^~
THANKS!
  • asked a question related to Observer
Question
4 answers
There is this paradox in quantum theory involving the measurement of entangled particles. Say separated observers (even widely separated), A and B, measure the spins of an entangled two-photon state whose total spin is zero. If A gets spin +1, B must get spin -1 and vice versa. But what if there are two observers, M and N, moving such that observer M sees A measure first but observer N sees B measure first. In particular say M is abreast of A when A measures and N is abreast of B when B measures. It would seem that for M, A's measurement would determine what B's should be. But, it would also seem that for N, B's measurement would determine what A's would be. By symmetry, it would seem that neither measurement should be primary but neither secondary. Note that A and B do not have to be in the rest frame of the device that issued the entangled photons. Has any experiment been done to test this paradox? I'm pretty sure the experiment would be very difficult -- maybe not even possible?
Relevant answer
Answer
This is a very interesting question. I think retrocausality and it's converse-- advanced causality have to be brought in. ie. that matter is extended in time. Cf. https://en.wikipedia.org/wiki/Olivier_Costa_de_Beauregard
Unfortunately the website : http://www.costa-de-beauregard.com containing all the papers and information on this topic seems to be down at the moment.
  • asked a question related to Observer
Question
2 answers
I want to build a Bayesian observer model of an interceptor that uses information of (prey) location and speed. Any suggestions of where to start? Papers, MATLAB code, etc.
Relevant answer
Answer
Начать надо с функции устройства захвата, можно использовать видео + радар. Потом, захват видео преобразовать к обработке координат.
  • asked a question related to Observer
Question
3 answers
In the following figures, the adaptive gain (c_i and rho_i) selection is also having problem??
Relevant answer
Answer
-----------------------------------DIRECTION TO Solve ---------------------------
Dear Arnab Pal ,
1. Firstly you need to know the difference between Asymptotic Stability and other type of stabilities (specially required for observer).
(a) Asymptotic Stability: system states converges to equilibrium points as time tends to infinity.
(b) other type of stabilities: In any observer, they have error dynamics, so there may be a fixed error in the states at time tends to infinity (meaning that error will be uniformly bounded at time tends to infinity), and this error denotes by Big 'O' notation. And in this case, the Globally Uniformly Ultimately Bounded (GUUB)/Semi-Globally Uniformly Ultimately Bounded (SGUUB)/ stabilities [1] will be employed.
You can refer Hassan Khalil Book about this concept.
Note: there may have other methods to solve this question. because in some paper, I have seen the papers where this problem has been solved by Input-to-stability.
Reference:
[1] Attached pdf
--------------------------------------THANKS-------------------------------------
  • asked a question related to Observer
Question
6 answers
Hello everyone,
How I can program a Lundberg state space observer using the Simulink block "Matlab function" and display the result on a scope ?
Relevant answer
Answer
Helle Dr. Yew-Chung Chak
Thank you for your answer, Dr. Pierpaolo Dini has given me the answer that I was looking for.
Thank you again for your time.
  • asked a question related to Observer
Question
12 answers
In Einstein’s 1095 paper 'On the Electrodynamics of Moving Bodies' he presents two clocks: Clock A is moving in a linear fashion relative to clock B, and hence Clock A would experience a dilation in time, ticking slower through each second, despite before beginning its horizontal translation it being synchronized with same.
Hence if time can bend for a moving observer (due to the perspective of a fixed observer watching them) Einstein's first postulate of relativity (that all frames of reference are equally valid) tells us that it can also bend for the fixed observer (from the perspective of the moving observer.) This is mutual time-dilation. It is a perceived relative phenomenon (depending on the perspective of the observer in question), however the principles from which it arises are psychological in nature; not physical, yet they are regarded as an accurate representation of the mechanics of the physical world by the bulk of the scientific community.
Perspective does not equate to reality. Time moves mountains and turns grasslands into forests; how can it be touched? Let alone bent.
So the question as it has remained for over a century still stands:
Which clock is moving faster? As it is a physical impossibility that both clocks are moving faster and slower than each other. Mutually-exclusive simultaneous events can only occur in the mind.
Relevant answer
Answer
I was unaware of Herbert Dingle (1890-1978) and his objection to the Special Theory of Relativity (STR).
[1] G. J. Whitrow; Herbert Dingle; Nature (London); Vol. 277; 15 February 1979; pp. 584-585.
The reason I was unaware of Dingle and his specific objection to the STR is because his name is not to be found in most textbooks that deal with relativity either briefly or comprehensively.
[2] Paul A. Tipler; Foundations of Modern Physics; Worth Publishers, Inc.; 1969.
[3] Charles W. Misner, Kip S. Thorne, John Archibald Wheeler; Gravitation; W. H. Freeman and Company, Inc.; 1973.
And, I believe, his clock objection has been recast as the "Twin Paradox". That term, "Twin Paradox", basically eliminates any mention of Dingle, and the part he played in the decades long (late 1930s until the early 1970s) discussion in the pages of Nature (London), and by referring to it as a paradox (a true statement that appears false) as opposed to a sophism (a false statement that appears true) rebuffs Dingle's objection and sides with Dingle's opponents.
When I recently discovered RG question on Dingle's Paradox, I was stumped as to how to find any citations to Dingle's work on the STR since even the two most popular answers seemed devoid of any citations save vaguely mentioning Nature. And, of course, I was not about to click the "Show previous answers" link 260+ times in order to see if someone else had provided citiations. It turned out, by chance, that I had in my library a Methuen's Monograph on Physical Subjects by Dingle, in which he mentioned his clock objection.
[4] Herbert Dingle; The Special Theory of Relativity, 3rd Ed.; Methuen & Co. Ltd. (London), John Wiley & Sons Inc. (New York); 1950; pp. 39-40.
A perusal of the online Nature archives revealed that, as in the case of your question, there were both opponents and suporters of Dingle's clock objection. The more things change, the more they remain the same, eh. Here are some citiations to Dingle's supporters.
[5] L. Essen; The Error in the Special Theory of Relativity; Nature; Vol. 217; 6 January 1968; p. 19.
[6] H. L. Armstrong; In Defence of Dingle; Nature; Vol. 242; 16 March 1973; p. 214.
I suppose it is not surprising that an unrepentant questioner (heretic to some), such as Dingle, should be expurgated from the body politic, but, as far as I can tell, his was an honest question, which he defended eloquently. In many ways, Dingle was a latter day version of Bishop George Berkeley (1685-1753), who, to his credit, pointed out the logical inconsistencies in Newton's method of fluxions to the eventual benefit of all who would later visit this subject, even briefly, as it forced later mathematicians to firm up and clarify their proofs of this important and useful subject.
[7] Carl B. Boyer; A History of Mathematics; Princeton University Press; 1968; pp 469-470.
Alfred North Whitehead and Bertrand Russell, like Bishop Berkeley before them, were aware of logical inconsistencies in the foundations of mathematics, and they unsuccessfully tried to remedy them in their volumes of "Principia Mathematica".
According to the following reference book, the first mention of the twin paradox occurred in 1911.
[8] E. U. Condon, Hugh Odishaw (editors); Handbook of Physics, Second Edition; McGraw-Hill Book Company; 1967; p. 2-43 (text) & 2-53 (citations).
The 1911 citation was to a paper by Langevin, although it is not clear that he used the term "Twin Paradox". It was also mentioned that this term "... had received much attention in the literature [cites two other papers in 1962]...".
[9] Paul Langevin; L'Évolution de l'space et du temps; Scientia; Vol. 10; 1911; pp. 31-54.
[10] Sebastian von Hoerner; The general limits to space travel; Science; Vol. 137; No. 3523; 6 July 1962; pp. 18-23.
[11] L. O. Pilgeram; Time dilations; Science; Vol. 138; No. 3545; 7 December 1962; p. 1180.
The paper by von Hoerner could be thought of as relativistic engineering since it simply applies the time dilation from STR to the problem of human space travel. The objection by Pilgeram points out that physical time and biological time (chemical and biochemical reactions) may not be interchangeable without experimental verification, a view rejected by von Hoerner in his rebuttal letter, which follows Pilgeram's objection letter on p. 1180. To those people who would agree with von Hoerner's rebuttal, I would ask do they think that the gedanken experiment known as Schrödinger's Cat would have the same philosophical weight if the cat were replaced with a stuffed animal? Anyway, the guiding principle in science should always be: trust but verify.
It is not clear that any of these three discussions actually employs the term "Twin Paradox". When I first read the RG question about Dingle's Paradox, I was unaware that Paul Langevin had first proposed the idea, which, today, is referred to as the "Twin Paradox". I only thought to rename it to "Dingle's Sophism" after I learned the word 'sophism' from the title of the book of clever physics problems by Lange.
[12] V. N. Lange, Valerii Ilyushchenko (translator); Physical Paradoxes and Sophisms; Mir Publishers Moscow; 1987.
One could, of course, equally ask why it is not referred to as "Langevin's Paradox", just the way we refer to Ohm's Law, Joule Heating, Maxwell's Demon, Schrödinger's Cat, etc. To those people who would say that 'twin paradox' is more self-explanatory or evocative, I would point to the following counterexample. We used to have perfectly good units for frequency, cps (Cycles per Second), that was self-explanatory or evocative, only to have it replaced by the units of Hz (Hertz).
As to why Dingle's name has been expurgated from physics textbooks and reference books, including the reference book by Condon & Odishaw, it seems that physicists like to burn their heretics in private as opposed to public burnings, although both processes have about the same carbon neutrality or lack thereof. I suppose a public burning is more liable to attract a mob of the hoi polloi shouting unwanted criticisms such as "Why are you burning him?" as opposed to the expected acclamations such as "Burn the bastard!".
Regards,
Tom Cuf
  • asked a question related to Observer
Question
4 answers
Sensorless Control of a Doubly Fed Induction Machine Based
on an Extended Kalman Filter
Improved Sensorless Control of Doubly Fed Induction Motor
Drive Based on Full Order Extended Kalman Filter Observer
  • asked a question related to Observer
Question
1 answer
Time seems to be related to the continuous destruction of the wave function ψ between an observer and an abstract objective reality. So space and time is a subjective coordination for the past of one of the many parallel universes, but on the contrary the future must contains all future dynamic universes. Is it an objectively false?
Relevant answer
Answer
That is correct. The tree of parallel alternative realities (Multiverse) in the past and as well in the future of any finite observer is the image of an eternal infinite container of information that seem to be projected in to the theorems of numbers etc. By definition the spacetime's variables are results of subjective measurements representing the interaction between observer and an abstract reality through the destruction of wave function ψ, but the objective reality seems to be an abstract eternal entity that throw its shadow on the entrance of the gate constructing of a motionless Mathematical mental world of ideas of Plato very far of the finite observer perseption.
  • asked a question related to Observer
Question
1 answer
I am trying to convert the spectral radiance values of an HSI acquired from the E0-1 Hyperion Sensor into reflectance. However, I couldn't continue the calculation without the Mean Solar Exo-atmospheric Irradiance values.
Relevant answer
Answer
If you know its distance to the Sun at any instant, you can use the broadband and/or spectral values at the top of the Earth atmosphere and correct them with the inverse-squared distance law.
  • asked a question related to Observer
Question
13 answers
According to classical electrodynamics theory, an accelerating charged particle emits an electromagnetic radiation. Unruh on the other hand found that an accelerating observer (charge) will find itself immersed in a black body radiation from the vacuum. How the de Broglie wave interacts with the electromagnetic radiation created by the particle? Is there a relation between wavelength and acceleration for an accelerated charged particle? Does the black hole evaporate completely or end in a finite mass (e.g., planck mass)?
Relevant answer
Answer
I guess that the Heisenberg uncertainty principle for energy and time holds well in experiments where the lifetime of certain quasiparticles can be measured,
so (Δ t)2 square won't give additional information in this case.
Best Regards.
  • asked a question related to Observer
Question
5 answers
I've been told:
“As measured by proper time, a radially falling traveler quickly reaches and crosses the critical radius of a black hole. The reality that the traveler quickly reaches the critical radius appears to the distant observer to take an infinite amount of time because of the propagation of light.”
But let’s test this with a thought experiment:
Put a reflector on the back of the traveler as he freefalls towards the event horizon of a black hole. Have a distant observer periodically shine a light beam at the traveler. Use the Schwarzschild metric to calculate the radial location at which the faster moving light beam will overtake the slower moving traveler and reflect back to indicate the location of the traveler to the distant observer. No matter how much of a head start the traveler has before the light is turned on, according to the Schwarzschild metric the light will always overtake the traveler before the event horizon is reached. Let the distant observer continue to shine light beams at the traveler until the distant observer observes that the black hole evaporates because of Hawking radiation. Granted, this will take a long time. But the entire time, the reflected light will continue to reflect back from the traveler showing that the traveler fails to reach the event horizon before the black hole evaporates.
How can this be?
Relevant answer
Answer
Richard: Given that the universe is 300 billion years old, let's do the same thought experiment, starting 300 billion years ago. After 300 billion years of traveling, the traveler has not yet reached the event horizon. This indicates that never, since the beginning of the universe, has anyone or anything crossed the event horizon of a black hole.
  • asked a question related to Observer
Question
3 answers
  1. Is there any statistical method
  2. Is there any physical /technical way to do that
Relevant answer
Answer
If the observer is a junior, a pilot study should be done, and the measurements and decisions of the junior should be compared with the results of a senior. A statistical test should be done and the differences should not be significant. The degree of agreement between the two observers would also be assessed. So if there are no big differences between the two observers, in this case the junior can start collecting the data.
  • asked a question related to Observer
Question
51 answers
Something which has always bugged me about the standard model is how can we approximate the age of the universe, when at the beginning, the incredible density would dilate time to the point to where proper time since would approach infinity? Which reference frame are we talking about? Further, if it is truly space which is expanding, and not massive particles moving further away from each other, an observer frame outside the curvature would not exist in the physical universe at the time in question. Another question I have is how might the Planck length be affected in such a dramatically curved space-time?
Relevant answer
Answer
James A Putnam & Sergey Shevchenko I hold the opinion that philosophy has no place in the sciences, especially physics. As far as being able to define these physical properties, you are both simply wrong. Mass is a manifestation of energy, directly related to Einstein's famous equation which every elementary kid knows... The meter is defined as the distance which light travels in that fraction of a second. Temperature is defined as the Boltzmann constant multiplied by the derivative of entropy. One second is defined as the length of time of a number of radiation emissions of a Cesium atom.
All of these quantities can be measured directly in any reference frame, whether it be inertial or non-inertial. These inertial or non-inertial frames defining space-time are explained precisely by the theories of special and general relativity, using the Minkowsky metric... Other metrics mentioned from other answers are more or less mathematically equivalent, yet the math is more convenient to solve certain problems. Where did you guys go to school? This is undergrad stuff...
I am leaving this question unsolved until I receive a satisfactory answer.
  • asked a question related to Observer
Question
42 answers
I would like to add some visual example to illustrate the different types of participant observation (complete observer, observer as participant, participant as observer, and complete participant). Any suggestion is welcome.
Thank you,
Isabella
Relevant answer
Answer
  • asked a question related to Observer
Question
7 answers
State observers are very frequently used to estimate the states of the system to design controllers. The question is what are the disadvantages/limitations of using observers? Does output feedback control solve those problems? If not, then what are other methods to solve issues with observers?
Relevant answer
Answer
Dear Pushkar Prakash Arya,
The implementation of the control by state feedback u (x) needs sensors allowing to give at each instant ‘t’ an approximate value of the state x (t). Two types of sensors of different natures are used: The first is that of physical sensors, coming from the instrumentation. These sensors are sometimes too expensive or difficult to produce for technical reasons. For this reason, we have to design a second type of sensors, software sensors, more commonly called observers. These are algorithms based on a model of the system and using relevant information given by physical sensors. These software sensors provide an online estimate of unmeasured system state variables at any time.
The state is estimated by virtually copying the dynamics of the system, taking into account not only the command u, but also the outputs of the system (the measurements) y in order to correct any deviations.
For more details and information about this subject, i suggest you to see links on topic.
Best regards
  • asked a question related to Observer
Question
3 answers
if I want to add a disturbance observer to an existing feedback controller (i have design a controller C(s); suppose it is a double loop PI controller fo an IBC converter. ) what would I do get this done ? and How does this affect the stability of the closed-loop system?
  • asked a question related to Observer
Question
13 answers
The Nyquist-Shannon theorem provides an upper bound for the sampling period when designing a Kalman filter. Leaving apart the computational cost, are there any other reasons, e.g., noise-related issues, to set a lower bound for the sampling period? And, if so, is there an optimal value between these bounds?
Relevant answer
Answer
More samples are generally better until such point as the difference in the real signal between samples is smaller than the quantization or other noise. At that point, especially with quantization, it may be a point of diminishing returns.
The other thing that nobody mentions is that faster sampling means less real-time processing time. In many systems, it's not really an issue as the time constants of the physical system are so slow as to never challenge the processing. In others, say high speed flexible meachatronic systems, the required sample rates may challenge the number of processing cycles available to complete the task.
Generally, the best bet is to return to the physical system's time constants and (if possible) sample 20-100x as fast as them.
  • asked a question related to Observer
Question
2 answers
can we used observer based controller to commercial water heater plant in order to make a correct decision of the output and simultaneously to observe the system
  • asked a question related to Observer
Question
12 answers
I have designed the mathematical model of the plant with nonlinear hystersis function f(x1) and is validated using simulation. Now I want to design the nonlinear observer to esttimate the speed (x2). Not that I have also modeled the nonlinear function in the model.
My state space model of the plant is
x1_dot = x2
x2_dot = q*x1 + c*x2 + f(x1) + u
Please suggest suitable observer to estimate the angular speed x2.
x1 is the angular position of the plant.
Relevant answer
Answer
High Gain Observer (HGO) is good techniques for nonlinear system to estimate their states, which also hold the separation principle. I think HGO will be better.
  • asked a question related to Observer
Question
1 answer
It is known in a input / output feedback linearization control that in a closed loop the physical state of the system is transformed into a linear mathematical state, which we have to stabilize by a linear auxiliary control, this linear mathematical state must be obtained, either by successive derivations of its outputs which is not recommended in case of implementation, or by a Luenberger observer.
In this question we want to know how demonstrate that this stabilizing linear control of the closed loop system can be developed via the physical state estimated by a nonlinear Thau observer.
  • asked a question related to Observer
Question
3 answers
Hi
I am conducting an interobserver variability study where we have 12 raters who are going to rate samples of lesions. They will rate up to 10 variables per sample. Although the size of the population is quite limited due to the nature of the lesions, it is a bit of a headache to find a well-written method to estimate the sample size needed for this study. Several searches on the internet have overwhelmed me with many possibilities, most of them being quite complicated.
Is there any statistical method you can recommend? Any help is appreciated!
kind regards,
Roger
Relevant answer
Answer
I think it is calculated by dividing the smaller total count observed (from one observer, relative to the other) by the larger total count (from the other observer).
  • asked a question related to Observer
Question
58 answers
Our knowledge of the world begins not with matter, but with perception. There are no physical quantities independent of the observer. All physical quantities used to describe Nature refer to the observer. Moreover, different observers can take into account the same sequence of events in different ways. Consequently, each observer assumes a “stay” in his physical world, which is determined by the context of his own observations.
If mathematics and physics, which describe the surrounding reality, are effective human creations, then we must consider the relationship between human consciousness and reality. Undoubtedly, the existing unprecedented scientific and technological progress will continue. However, if there is a limit to this progress, the rate of discovery will slow down. This remark is especially important for artificial intelligence, which seeks to create a truly super intelligent machine.
Relevant answer
Answer
Dear Boris Menin ,
Golden ratio is a geometric mean or average . it could be apply to every aspect of life even in which amount we have to inhale and exhale to getting the perfectness that also explain by the meditation. The perfectness can achieve by the meditation that reflects in many Indian temples architecture those follow the Fibonacci series pattern in the temple architecture without knowledge of the series but due the devotion towards the god temple construction they constructed temple with meditation. There are also the statue of Gautam Buddha in which we found the golden ratio without knowledge of golden ration . So some where you can see the golden ration and meditation and devotion are the synonyms .
  • asked a question related to Observer
Question
8 answers
I am working in speed sensor-less control of induction motor and for estimation of speed i have used sliding mode observer. Using SMO I have estimated alpha-beta axis stator current and alpha-beta axis rotor flux accurately. though I have estimated currents and rotor fluxes accurately, I can not estimated speed. Is there any one who can help me with this issue?
I have also added the images of results that i have obtained.
Relevant answer
Answer
If You divide by square od rotor flux value please limit this to 0.01 from down.
  • asked a question related to Observer
Question
3 answers
I am designing a flight controller for a quadrotor.
At first I am designing a nested/cascaded controller consisting of only proportional controllers Kp . Now, if i tune the rate controller for 10 rad/s cross-over frequency, what should be the cross-over frequency for the angle, velocity and then the position loops. Also, what else do i need to know while designing a flight controller for practical implementation purposes?
Secondly, How do we implement a own flight controller such as observer based via arducopter?
Relevant answer
Answer
Thanks alot for your time! These links are really helpful!
  • asked a question related to Observer
Question
11 answers
I am trying to discretize a continuous time state space model using the following code
s=tf('s');
G=1/(Iyy*(s^2))
Gs=ss(G)
Gd=c2d(Gs,0.01,'zoh');
Now, when i use this discretized model 'Discrete State-space Model' in simulink, my close loop system goes unstable. Same is happening with observer, like discretized observer is making close loop system unstable. Can someone help me here?
Relevant answer
Answer
Your system is basicly a double integrator, so a borderline stable system. If you look at your phase value of the bode plot for the continious system (bode(G)), you will see that it has a phase of -180° over all frequencies. Since any kind of delay causes the phase of a system to drop, if you introduce an arbitrarily small amount of delay on your continious tf G, and use the command "margin(G)", you will find that your system will always have a negative phase margin. And since discretizing will always introduce delay into your system, closing the loop on it will automatically destabalize it. You can use 'tustin' as you discretizing method, which essentialy uses trapezoidal integration, a more stable integration algorithm, and simulink should probably get your discrete system stable this way.
  • asked a question related to Observer
Question
12 answers
I am exploring the possibility of using a mixed method research design to investigate creative cognition in dance. My aim is to describe cognitive processes in choreography, according to cognitive psychological theories. For this purpose, I intend to use a mixed method research design (including observation and psychometric tests), I have, however, not come across a study that uses the participant observer method in such design. I would appreciate insights/ relevant literature.
Relevant answer
Answer
From my perspective, there's no reason not to use observations in a mixed-method study. Qualitative researchers, who use triangulation will often use interviews, observations, and another data collection source. I did that when I studied the knowledge base of critical care nurses. I interviewed the nurses, watched them take care of patients, and analyzed their nursing notes. I could easily have given them a quantitative test.
You just need to tie the data collection methods. If you have a theory of creativity from which a test or survey is developed, look at what you could observe watching the dancers and/or choreographers. If you use the Torrance test of creativity, for example, one of the abilities they test is the ability to come up with multiple ways of doing something. How many different ways can you use a paper clip? is a favorite. I'm assuming your choreographers' process through different ways of doing a dance. That would show up on a creativity test and you could observe it in action.
Good luck with this study. Sound very interesting
  • asked a question related to Observer
Question
2 answers
We have several measures for a given event in our longitudinal study (e.g., Year 1). Some are surveys we are sending to participants and their families, while others will be entered by study staff. For the surveys, some measures should be completed by the participant, while others should be completed by a parent or observer. Other than creating separate arms for each type of respondent (which creates its own issues), is there a way to send out only a portion of the surveys to one respondent and the other portion to another, and still have them linked to the same record?
Relevant answer
Answer
Can use survey-specific email address now.
  • asked a question related to Observer
Question
5 answers
I want to know whether a luenberger observer or a modified form of it be effective for estimating the states of a system of the following forms:
1. x_dot = f(x,u,d); y = x
2. x_dot = f(x,u); y = x
where x_dot is the derivative of the state vector, u is the control input and d is the external disturbance input. f is a nonlinear function with the product of states, control inputs, and disturbances.
Please give some specific suggestions regarding the observers which are best suitable for state estimation of such models.
Relevant answer
Answer
You can use a Luenberger-like observer for nonlinear systems, please see the link below which is exactly your answer:
  • asked a question related to Observer
Question
13 answers
Am I starting a discussion because I made a discovery or did I make a discovery because I started the discussion?
What if it is not that I am speaking true or false and definately it isn't about Free Will vs Determinism anymore, Why?
Because what if there aren't two sides any more but there appears to be two sides,
Can I not say that the observer and the observed are both "IN SYNC" with one another?
So could it be that it's not about whether or not the observed is because of the observer but it is about that the observer and observed seems to give rise to two contradictory notions but the fact is that both the observer and the observed exist,
So can I really say that and what does it mean if I say they are "IN SYNC"
Could it also be that mass and energy are appearances of something that exist and because of what I think is the right term to communicate my observation and because of the "IN SYNC" that I refer to, could it be that both mass and energy are there but also not really there, it just appears to be there, but what would be responsible for that appearance then?
What does it mean not literally but in understanding of what I am trying to put in words based on observation and sound reasoning of what it means to be in the "NOW" and why it is a fact that both the observer and the observer exists rather than whether or not observed exists because of observer.
But in essence,
What does it mean if I say that the observer and the observed are "IN SYNC"?
Relevant answer
Answer
QM answers that observer and observer are dependent on each other. In other words, QM says that observer and oberserver are NOT independent.
For example, nothing can observe something without influencing it. However, there can be isolation based on energy, time, frequency, or momentum. We call this effect, by the name "sympathetic resonance" and is very much used and demostrated in music, to conduct energy, and in anything when viewed as vibration -- such as matter itself. It is also observed in gravitation, as another example.
This has made the solar system stable, until a certain resonance disturbs it, and even planets can be easily disturbed in their orbits. Example, the possibility that the orbit of Mercury is open (see my preprins) under QM and GR, not really closed, enables an expanding radius, and its capture in a different orbit, progressively. This could lead to exchange orbits with the Earth, and the extinction of organic life on Earth. This is an unlikely event, but possible,
  • asked a question related to Observer
Question
5 answers
Can an alternative to Minskowski’s space-time diagram explain all this?
How the world-lines of all bodies in uniform motion have the same length in spacetime;
that bodies in relative motion have different orientations in space as well as time;
how observers with relative motion between them will each observe the other to be
moving more slowly in time;
why the speed of light is the absolute limit of speed;
that light is a constant, and for any observer, the speed of light is ~300,000 km
(or ~186,000 miles) per second, because in the continuum of spacetime,
the distance it is observed to cover in space is equal in length to one second in time.
Relevant answer
Answer
The axial Doppler shift gives time time has many dimensions if omissions in relativity are fixed; the details:
Independent of the MM experiment: The Fourier time series proves all Doppler shifts change observed time and adds dimensions to time.  It does this by breaking any signal into sine and cosines if the frequency of each are multiplied a Doppler shift frequency ratio,  each value now happens at t/K instead of t. Therefore by superposition it is true for the original function.   That adds dimensions to time because the axial shift is directional. That impacts a lot of relativity. Also, we sense all things by forces traveling at the speed of light and have Doppler shifts. For the full proof and another different one and some impacts open this link:
The importance of that is for most angles the axial shift is larger than the transverse; the axial shift is directional giving direction to all things it affect and we measure all things by forces whose transmitted energy have Doppler shifts.The source of Einstein and Lorentz NOT giving the axial shift that power is Lorentz wrote about aether winds which cancel each other out in the axial direction. Which enabled isolation of the transverse shift. But after the light in the Michelson experiment hit the first stationary mirror, the Doppler shift puts it in the stationary reference plane. No more shifts to cancel the first. Also in most situations the axial shift exists.
Link to a paper describing an omission in the application of relativity to beams in most books: https://drive.google.com/file/d/17wia8LJNxjRAnDqK_XwAOABK5yqs8qM/view?usp=sharing
This link is to a paper on: One important constant is NOT invariant during change of reference frame: https://drive.google.com/file/d/1ljTtjvx5HiFi3vguznj8p-8XRtXa85NV/view?usp=sharing
Thank you for your time and I hope the above gave you some new ideas. Samuel Lewis Reich sLrch53@gmail.com
  • asked a question related to Observer
Question
4 answers
Hi
I am working on Active Disturbance rejection control of a quadrotor, which consists of an extended state observer. Can anyone guide me about it or suggest any book/thesis that is available. I shall be grateful.
Regards
Relevant answer
Answer
Saeb AmirAhmadi Chomachar Thanks alot. This is very helpful.
  • asked a question related to Observer
Question
6 answers
Is it theoretically possible, that after discretization by using Talyor Series Expansion, a non-observable nonlinear system will became an observable?
It was proved, that used continuous model of PMSM is non-observable (see attached). I want to know, if resulting discrete system is observable or not. Any comment appreciated. Thanks.
  • asked a question related to Observer
Question
3 answers
Dear All,
I did Nyquist plots ac impedance measurements and I found the following plot. Can anyone help me to explain the observer trend with different concentration on steel with blank?
Thanks for your help.
Regards,
B. Thanga Giri
Relevant answer
Answer
It seems that you need to simulate your plot by Zview software to get electrical equivalent circuit. In low frequencies you are observing inductive behavior which could be related to the delamination of the formed film in the surface but some researchers believe that these could be wrong data because negative impedance doesn’t exist in reality. I propose you to find papers worked in your research area and then compare your Nyquist plots and equivalent circuits by them.
  • asked a question related to Observer
Question
15 answers
Please suggest to me some alternative state observers which are comparatively more effective than Sliding mode observers (SMO) for handling nonlinear systems with disturbances.
Relevant answer
Answer
The purpose of an observer is to estimate the unmeasurable states of a system based only on the measured outputs and inputs. It is essentially a mathematical replica of the system, driven by the input of the system together with a signal representing the difference between the measured system and observer outputs. A sliding mode observer, which feeds back the output estimation error via a nonlinear switching term, provides an attractive solution in the presence of unknown signals or uncertainty. However, the control gain cannot be chosen arbitrary large due to practical considerations such as reaching control surface deflection limits. Furthermore, control chattering is undesirable in practice because it involves high control activity and may excite high-frequency unmodeled dynamics. Conventionally, the width of the boundary layer has expanded to reduce chattering but this resulted in large steady-state errors.
  • asked a question related to Observer
Question
2 answers
Two observer evaluate the same qualitative variable; what is the best statistics descriptor to evaluate concordance? K cohen, concordance correlation coefficient, phi coefficient of pearson, other?
I try with K cohen, but despite 66/67 of concordance (98.50%) k cohen was too low (K=0.659). while with 58/67 (86.57%) of concordance k cohen was 0.730. Why?
Thanks
Relevant answer
Answer
Dear Mohamed-Mourad Lafifi,
thanks for your precious documents.
Best regards.
  • asked a question related to Observer
Question
6 answers
I've used Noldus Observer before, but can't afford it now. I'm not sure that it matters, but this is for scoring frequencies and durations of rodent behaviors within neuroscience/ethology studies using digitally recorded videos.
I'd like to have the capability of running simultaneous timers that can be independent or dependent on one another (depending on my optimizations), while also being able to tally frequencies of select behaviors/events independently. Ideally, the tallying and/or starting or stopping of timers would be tied to selected (ideally programmable) keystrokes.
Relevant answer
Answer
I used BORIS, a free and open-source software. it allows you to run simultaneous timers independent or dependent on each other, it calculates the frequencies of behaviors. the keys related to the behaviors are easily programmable as well as the mutual exclusion of the variables between them, if needed.
  • asked a question related to Observer
Question
1 answer
Does anybody knows of a systematic monitoring methodology which is indipendet on the skill and the eyes of the observer i.e. any one that monitors will end with same result
Relevant answer
Answer
I am not familiar with agro and bio-tech, but if you could resolve and identify a unique chemical composition/spectroscopy signature of the mites, then you might be able to devise a detector to detect it, and then apply to statistically powerful number of some random sample of plants.
As I said, this is outside my field, but it can maybe get your problem solving creativity flowing!
I hope you would find a solution using organic permaculture, so I would also suggest to see if you can find any organic farmers of citrus and see how they are managing the problem. :)
  • asked a question related to Observer
Question
4 answers
I have implemented utkin observer for drum boiler turbine system...The estimated state converge to actual state at a different initial condition but it is not converging at arbitraty intial condition..can someone knows the reason?
Relevant answer
Answer
you can use the reaching law as $s(k+1)=d(k)$ instead of $s(k+1)=0$ where $d(k)\leq d_m$ assuming the bound of $d(k)$ is known.
  • asked a question related to Observer
Question
3 answers
I am a control engineer and also a student who is studying the doctor's degree. I am interested in the disturbance observer now, I need some information about the discrete-time implementation of the DOB . Could anyone give me some advice?Thank U very much 。
Relevant answer
Answer
It is easy to design disturbance observer in discrete mode but the error will be within an error bound. Please clear whether you want to design with the state information or with output information only. State-based designs are very easy while output-based designs are of high interest to date.
  • asked a question related to Observer
Question
9 answers
Black swan risks are described as an extreme outlier events that come as a surprise to the observer, and in hindsight, the observer rationalizes that they should have predicted it. Those risks have the maximum impact, but the minimum likelihood, and it's never easy to predict them. How can we draw the line between realistic risk scenarios and those perceived as unrealistic, but nevertheless possible ones, with catastrophic outcomes?
Relevant answer
Answer
Black swans are events that happen once in a long time and in time series data it will be an outlier. Whatever estimates we have will not be accurate because of the outliers which will be averaged out. Perhaps a std deviation analysis will help to take into account outliers like black swans. In scenarios analysis, a deviation of 40-50% have been built into models to take into account crisis. Predicting such events is not within our tools of analysis yet because it happens out of the blue. Most prediction used a trend analysis.
  • asked a question related to Observer
Question
3 answers
Hi everybody,
I'm using ebeam evaporator to deposit 20-50 nm of Cr on PMMA (950k A4). I coat PMMA on glass by spin coating at 1000 rpm then bake at 170 C in 10 min. However, I observer so many cracks on Cr layer after deposition. Could you please suggest a potential solution?
Also, the adhesive between Cr and PMMA of my sample is not good that I can easily remove the Cr layer by scotch tape. Is there any way to improve the adhesive between Cr and PMMA since I have tried Ti, Ni but it did not work.
Thank you.
Relevant answer
Answer
Dear Dr. Minh Nguyen ,
I suggest you to have a look at the following papers hoping they are useful for your interesting research:
-Cracking effects in squashable and stretchable thin metal films on PDMS for flexible microsystems and electronics
Tiffany Baëtens, Emiliano Pallecchi, Vincent Thomy, and Steve Arscott
Sci Rep. 8: 9492 (2018)
-Improved electro-mechanical performance of gold films on polyimide without adhesion layers
Barbara Putz, Rachel L. Schoeppner, Oleksandr Glushko, David F.Bahr, Megan J.Cordill
Scripta Materialia, 102 pp. 23-26 (2015)
-Fracture and Delamination of Chromium Thin Filmson Polymer Substrates
M.J. CORDILL, A. TAYLOR, J. SCHALKO, and G. DEHM
METALLURGICAL AND MATERIALS TRANSACTIONS A, 41A, 870 (2010)
Enjoy reading and best regards, Pierluigi Traverso
  • asked a question related to Observer
Question
3 answers
recently I faced to a problem in extracting an advantageous mathematical model of a pneumatic servo positioning system which uses a normal cylinder and piston actuated with a proportional pneumatic valve, to be applicable for designing an intelligent neural network-based adaptive controller with the use of sliding mode observer for the aim of trajectory tracking with the presence of matched and unmatched uncertainties and nonlinearities and disturbances. the approach will be considered as a disturbance rejection or fault-tolerant method. But the problem is the emerging complicated high order relations specifically in modeling the proportional valve. we have the mass flow rate ''m dot'' equation which is a function of valve-generated compressed air pressure ''P1 and P2'' flows into both sides of the cylinder and the generated control signal ''u''. but the main equation for describing the whole process is based on the second law of newton which is written as "m(y double dot)=(P1.A1 - P2.A2) - Ff - FL- Fd". the challenge is on the term (P1.A1 - P2.A2) and more specifically on how to define P1 and P2 in order to be as simple as possible and not to increase the order of the system equations. in some researches (like my recent IEEE 2018), P1 and P2 define by using thermodynamic laws and physical description. in these approaches, you may face with the derivative of P1 and P2 and so you forced to differentiate the whole equation and turns it into "m(y third dot)=(P1dot.A1 - P2dot.A2) - Ff - FL- Fd". in other hands in a few types of research in order to avoid the complexity and decrease the order of system equations, the term (P1.A1 - P2.A2) turns into a simple form of b.f(u) in which b is a positive constant and f(u) is a function of control signal. this form of description is a bit conservative but helps a lot in extracting a state-space and control form representation which is of necessities for designing the nonlinear controller.
now the question is if I need a sliding mode observer thorough designing the disturbance rejection intelligent adaptive controller, what can I do and which way is more effective? any other so far so good ideas and comments which are not mentioned in the explanation or any kind of corrections if I am wrong in any parts are all welcomed.
Relevant answer
Answer
  • asked a question related to Observer
Question
2 answers
What type of slides and cover glass you use while working on an inverted fluorescent microscope (We are about to get an Axio Observer 7)
Also it would be good to know what kind of petri dishes / microplates / flasks can be used. Can we use plastic ones or they should be glass only?
Relevant answer
Answer
The coverglass is what you will be imaging through and is the key. The lenses are designed to image through #1.5 thickness coverslips. If you use others (#1, #0, or plastic) there will be spherical aberration issues. In particular with plastic, high mag high NA immersion lenses will not have enough working distance to focus through thick plastic or slide. Low mag low NA lenses can, but the image will be degraded due to the above. There are companies that sell plastic vessels where it is supposed to be comparable to glass, like Ibidi, but in my experience they are still not quite as good as coverglass #1.5.
  • asked a question related to Observer
Question
6 answers
I have designed an observer based control strategy. Now I want to analyze its stability analysis. So my query is; that we must sort out the stability of the closed-loop system or we can find it for a separate section.
Relevant answer
Answer
First, before designing an observer-based control scheme, you have to ensure that the separation principle holds for that. If the separation principle holds, then we can say the stability can be guaranteed individually, i.e for controller and observer.
  • asked a question related to Observer
Question
4 answers
Hi there,
I got data of multiple observers that measured the weight of an animal (the same). It's literally just one column with categorial value for the observer and another for the measured weight. Each observer measured the animal 3 times.
One particular observer is new in the field (so has no or little experience) and I would like to test if that observer might deviate from the others in his measurements -- I would go for a one-way ANOVA here, is that correct?
And another hypothesis is that whoever measured the animal has a significant effect on the estimated weight -- how do I test for that? Isn't it both the same? It's two different questions for this research, so I am a bit confused if it's actually different tests?
Thanks a lot!
Saskia
Relevant answer
Answer
Thanks Mohamed and Merga,
even though there was some informative and useful links/PDFs I’m still not able to find the right test to use for my case, unfortunately.
I think I’ll stick to the ANOVA comparing all means with each other and a post-hoc to see which observer differed significantly to others.
And to see if the observers have a significant effect on the estimated weight, I’ll probably go for a t-test comparing each observer (mean) to the overall mean of all observers together assuming it’s the true estimated weight.
  • asked a question related to Observer
Question
15 answers
Suppose time is proportional to entropy. Then time would be related to energy and how it distributes. Is time a kind of projection of a feature of the universe. Is it possible to conceive that our universe looked at from outside would appear to be unchanging and featureless (like a black hole) and that the inhabitants inside perceive changes that are from the outside observer’s perspective illusions?
Relevant answer
Answer
Physics and our understanding (ability to predict observations) start from basic assumptions from which other things are modeled. "Time" is one of those assumptions that are basic to our understanding. However, change form one event to another is in the observed category - which must be modeled. This question is confusing the abstract "time" with change which also includes the entropy as an abstract change from one energy level to another. We should consider the observed events as real. Otherwise leads to nonsense and not useful waste of effort.
  • asked a question related to Observer
Question
2 answers
Hi fellow reserachers,
Quick question:
I was wondering if anyone has suggestions for where to find open access datasets on observer agreement involving >= 3 observers?
An example of such a study is this one:
"Interobserver and Intraobserver Variability in Measurement of Non–Small-Cell Carcinoma Lung Lesions: Implications for Assessment of Tumor Response".
Yours sincerely
Relevant answer
Answer
Dear Friend Jens Borgbjerg
kindly check the links..
Open Access dataset repositories
1. UCI Machine Learning Repository
2. UCI KDD Archive
3. MLData
4. Opendatasoft
Commercial Dataset Repositories
1.Xignite
2. IEEEdata port
  • asked a question related to Observer
Question
13 answers
Generally when we describe motion of an object, we think of a `` point mass''and use the hypotheses of geometry to pictorially depict its trajectory as a curve. Then usual methods of calculating slope, etc. are used to define velocity, etc. This is the way, a person standing by the side of a road, will describe the motion of a moving car. However, if the person stands on the road, and a car is approaching him/her, then the car will gradually grow bigger according to our visual perception. When the car was far from the person, the ``point mass'' approximation was valid, but as it approaches, the approximation fails, although there is a perception of motion of the car. Therefore, the hypotheses of geometry certainly does not hold all the way. Then, what is the way of describing such motion?
Relevant answer
Answer
The term you are looking for is "optical flow." I believe there are several mathematical models that explains optical flow. I'd recommend digging into the literature with this keyword.
  • asked a question related to Observer
Question
6 answers
I have a state space model of the system with dimension of various matrices as follow,
A = 4*4
B = 4*2
C = 2*4
Relevant answer
Answer
To the best of my knowledge, I think your system has to be observable first. Secondly, you have to select closed loop poles such a way that the eigen values of matrix (A-L*C) lies in the left half of complex plane where, L is the observer gain matrix.
Hope this will help you.
Thank you.
  • asked a question related to Observer
Question
6 answers
if initial condition for a basic system not be zero(cause, system not response) then how much can be put initial condition for the system observer?
or how can find the initial condition for observer that the best response for observer?
Relevant answer
Answer
Generally, the equilibrium point of the most systems is the origin, so selecting zero for observer initial state means that the system was at its equilibrium point before starting.
If the system behavior is statistically available, the initial state with the most frequency can be chosen as the good initial selection.
However, it is generally attempted to increase the convergence rate of the observer by adjusting its parameters, and in general the choice of initial state for observer is rarely applicable.
  • asked a question related to Observer
Question
2 answers
The linked file is a proof that the axial Doppler shift changes observed time:
Being a Doppler shift it changes observed distance dimensions also. That if a point on an observed object is measured in observers world to be at x,y,z,t =6,9,2,0 in the world of the observed it is at x',y',z',t'=3,-7,9,5 assuming a relativistic velocity between the observer and the observed. Unlike the transverse Doppler shift it is proportional to the cosine of an observation angle.
Relevant answer
Answer
Hi I'm Professor Soheil Sayyed Hosseini To solve the problem see my article on this issue of my control, which is published by the University of Rochester. If it is acceptable, say I wish you well.
  • asked a question related to Observer
Question
5 answers
Hello
To start off, the question deals with non relativistic system.
It is known that Biot-Savart law gives the magnetic field at position r (the position of the observer) , created by a current density at position r", if the current is static and the element is stationary in the observer rest frame. In the case of a time dependent current, one may use Jeffiminko equations to account for the delay.
However if the current element is moving with respect to the observer in a non inertial reference frame. Can we still use Jeffiminko equations ?
Thank you in advance
Relevant answer
Answer
Hi Newgato,
in my opinion, if, in the rest frame of the current element, the current is constant, but seen from the rest frame of the charge, the current element is moving, then the d J(r', tr) / d t term in Jefimenko's equation for E is not zero because it is related to an r' which rests relative to the restframe of the charge, and at this point the current is not constant but changes direction and/or strength.
  • asked a question related to Observer
Question
2 answers
I would like to compare the intra and inter observe reliability in three different groups (each has 3 observer). How can I do this? Cohen kappa and Fleiss' kappa are for individuals and Fleiss' kappa can help for individual intraobserver analysis. Findings are categorical. But what should I have to do for interobserver analysis of groups, should I get the mean or do you suggest something else?
Relevant answer
Answer
Dear Yiloren,
I suggest you to see links and attached file i hope those references are on topic.
Interrater reliability: the kappa statistic - NCBI
https://www.ncbi.nlm.nih.gov › articles › PMC3900052
Psychiatry: An evidence-based text
Reliability Assessment Using SPSS - ASSESS SPSS User group
www.spssusers.co.uk › Events › ALDRIDGE2015
Best regards
  • asked a question related to Observer
Question
3 answers
Dear colleagues,
the majority of EKF/UKF implementations for speed sensorless control of PMSM are in alpha,beta frame (i.e. observer is implemented in stationary frame). I wonder why? Equations in dq fame are much more simpler, so the computational requirements should be lower. Is there any evidence that observer doesn't work implemented in dq frame?
Relevant answer
Answer
In fact , the simplified EKF reduced state dimention( in dq frame) is used for only speed estimation, and without rotor position estimation .... the resons resides mainly in the abc/dq cordinate transformation.... .
Elsewhere, you can read carfully this research paper.
best regards,
  • asked a question related to Observer
Question
4 answers
And what will be the speed of the wave perceived by an observer sitting at the source itself, which is moving ?
The speed of a ball thrown from a moving source ( Inertial ), is seen differently by the person sitting at the source and a person standing somewhere else (a inertial frame though). Why can't the same approach be applied to wave ?
Relevant answer
Answer
though the speed of the wave is independent of the speed of the source in both cases, the details are different for sound and EM waves:
Assuming that the sound propagates in a gas (or fluid), and that the flow of the gas is homogeneous (no divergence, no curl), then there is one "rest frame" defined by the fact that the gas is resting as seen from this reference frame. Sound waves are not inertial objects (in contrast to the the ball you mention) but disturbances of the density of the gas. Measured from the rest frame, the speed of the sound waves depends mainly on mass, density, and thermal velocity (i. e. temperature) of the gas molecules. Pictorially speaking, the source reaches out just to a thin layer of neighboring molecules, the further propagation is independent of the source and the initial speed of the molecules. Seen from other inertial frames, the velocity of the sound propagation and the velocity of the frame relative to the rest frame add up vectorial. So, if the source is moving relative to the rest frame in, say, positive x-direction, then an observer moving with the source will see the sound propagating slower in positive x-direction, and faster in negative x-direction.
EM waves (in vacuum) are not disturbances propagating in a surrounding medium but carry their own medium (electromagnetic energy) with them. The speed depends on the permittivity and on the permeability of vacuum, and since these quantities are the same in all inertial frames, the speed of EM waves is the same in all frames. Consequently, there is no special "rest frame".
To put it another way, that the speed of light is the same in all inertial frames is a basic hypothesis of Special Relativity Theory (SRT), and since SRT wasn't refuted experimentally until now, this hypothesis seems to be correct.
That observers moving at different velocities relative to a source do not make contradictory measurements is based on the fact that there is no simultaneity among different frames; instead, an observer looking at a moving the source will see the region behind the source at an advanced time, and the region in front of the source at a delayed time.
  • asked a question related to Observer