# Electrical Engineering

Tuning PID without process transfer function?
I am having a closed loop control system where i use a PID controller. But if the transfer function of the process is complex to derive, then how can i tune the gains of the controller to have my desired response? Please attach any tech notes or papers. Thanks in advance.
Viswanath Devan · Indian Institute of Technology Guwahati
Your question relates to process control, to be specific auto-tuning. Process control often uses a mathematical model for a plant which is derived either from the theoretical physical modeling or by identification of input-output data. When tests are performed to determine parameters or information other than system/plant parameters, the approach is known as auto-tuning. As Professor Igor Boiko brought out, the cyclic or Ziegler-Nichols (Z-N) closed loop method is one of the popular methods for auto-tuning to find information like proportional, integral or differential gains, time constant, etc. based on the values of 2T and K_c measured from a stable limit cycle. However in a practical system Z-N test may be difficult to obtain since plant is never linear. Relay based describing function methods are becoming popular nowadays for process identification. Primary advantage of relay based method over Z-N is that the limit cycle can be controlled by relay output levels. You can refer "Advanced Control Theory - A Relay Feedback Approach" By Professor Somanath Majhi (C-Engage Learning) for more on this.
What are the good open source alternatives to MATLAB?
I am trying to find an open source software package that should be as good as MATLAB.
Raymond Rumpf · University of Texas at El Paso
I added a hyper-linked list of this type of free software here: http://emlab.utep.edu/resources.htm Hope this helps!
What are your thoughts on renewable ocean energy, such as wave, wind and tidal energy?
For example, Marine Renewables off the coast of Ireland has the potential to produce over 70GW of energy, more than 14 times the country’s current energy demand. There are many such examples speaking about the viability of ocean energy. A floating windfarm off Coos Bay in Oregon was approved! Are there such attempts in your country, maybe realized projects?
Andrew Avent · University of Plymouth
I'm simply trying to place into context the lack of cohesive thinking on green issues, a simple sensitivity analysis would dictate that we are fiddling whilst Rome burns....
What actually happens to a conductor at very high frequencies where Ohm's Circuit Law V=R.I breaches ?
In many books it is given that Ohm's Circuit Law V= R.I breaches at frequencies greater than 4 Ghz while Ohm's Field Theory J= σ.E is valid at all frequency ( right from dc to Ghz). I don't understand the concept behind the fact that how a conductor behaves at Ghz frequencies such that one law has failed while another is still valid. Somewhere it is given that at high frequencies we can't assume circuit elements as lumped because they turn into distributive. In some other literature it is given that at high frequencies inductive and capacitive natures of conductors dominate the resistive nature. But I'm not able to understand what actually happens at high frequency.
Jiang xiu zhu · China University of Mining Technology
Maybe answer the question like so:The ohm‘s law is now demonstrated to be correct in many frequencies，but there are different shows with different frequency ranges for a identical conductor. u=zi there u,i,and z all vary with frequncies,there will be a skin effect on the surface of the conduct when it work at high frequencies. "the surface roughness starts playing an increasinly important role for frequencies above 100 Mhz for the metallic losses"(see above Fritz's answer).when the frequency is more than 4Ghz there need a special measuring way to verify the ohm's law. it is impossible to prove it using traditional method.
Does anyone have all of the values of 3MW synchronous generator for simulation?
I would like to simulate a 3MW synchronous generator and I need raectals inductance of the synchronous machine.
Is it possible to get the mathematical equation of the simulated output in MATLAB/PSPICE/Other?
If the circuit simulation is simple then it is very easy to express the output waveform with mathematical equation. It becomes very difficult when circuit becomes complex. Is there any simulation tool to address this issue?
Lutz von Wangenheim · Hochschule Bremen
There are symbolic simulation programs which are able to calculate (linear) transfer functions (symbolic formulas) for electronic circuits. But what do you expect as "output voltage"? This voltage, of course, depends on the particular input signal. In case you want a techcnial expression (formula) for the output voltage you can use the Fourier transform to get such an expression. Or what is your desire?
Do you have a block diagram of a transceiver uwb?
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Seyedjavad Vaezjalali · Iran University of Science and Technology
A scientist is like a tree when he puts his knowledge with others is like fruit Thanks sjvjs
An RG-like voting system for student presentations?
Sometimes, the upvotes/downvotes you receive on RG could be a useful indication of what the listeners are thinking. It is almost as if you are reading their minds, without actually having them talk to you. The effectiveness of this system comes from its simplicity. Only two options are allowed: UPVOTE, DOWNVOTE. I found that, when we have an inexperienced student who is preparing the presentation of a new paper we will present at a conference, (s)he has to build experience in understanding what the listeners are thinking, or, what sounds good and is presented well, and what doesn't. I am wondering if an RG-like simple voting system for student presentations would be possible, where, every listener (say, 10, 20 of them) has an upvote and downvote button. That way, the student gets a good idea about the presentation, and tries to improve his/her presentation on the next round. Is this practical ? Any thoughts ?
Elisabeth Kauba · Wirtschaftsuniversität Wien
The votes would give the students a general idea how well his presentation was received by the voters. However, based on the voting alone, he/she would find it difficult to identify areas for improvement. Successful presentations have a number of success factors: apart from the content, it is the storyline, the wording, the way the story is presented including body language, mimics, voice melody, usage of presentation media, the way a speaker relates to the audience – to name just a few. In my experience there is nothing equally suited to help an inexperienced speaker to improve then personal feed-back and sparring with an experienced presenter.
How can I relate the change in threshold voltage from drain bias voltage with change in the surface potential at channel-drain junction?
I want to measure the change in threshold voltage due to drain bias voltage for Graphene field effect transistor, but it has zero band gap. So, it produces larger punch-through and it is difficult to calculate the change in threshold voltage from drain current vs gate voltage characteristics as we did in the conventional MOSFET.
William Frensley · University of Texas at Dallas
What is the origin of the results in the last figure? Since discrete points are being plotted, I presume that this must be from some experimental technique for profiling along the channel, which probably involves some scanned-probe apparatus. You have an indication of the limits of this technique in the ~700 mV offset in the source region, which was presumably held constant between the two measurements. Please be aware that it is exceedingly difficult to accurately profile the channel potential. The electrostatic potential is a very different quantity from any circuit node voltage. It can only be measured indirectly, by techniques such as the vibrating capacitor method. For an active device under bias, any sort of probing will perturb the device to a degree that makes the results very uncertain. If the figure represents a theoretical calculation, then the model has the answer to your question, but has some rather obvious problems.
Can anyone provide suggestions on how to design a high altitude solar inverter?
I want to design a solar-based inverter for high altitude ranges. So I want to know the parameters to be considered or that would affect the inverter's performance. Please suggest the topologies used for the inverter design at high altitudes, i.e. whether VSI or CSI design will have better performance? Also which software can be used to simulate high altitude inverter design. I also want to know the maximum power capacity of these high altitude inverters so far.
A.K. Mukerjee · Indian Institute of Technology Delhi
I agree with the others that apart from cooling issues there is nothing different. At 11,000 feet or above the low temperature will compensate for the wind flow for cooling. At best a cooling fan may be added or larger heat sinks for the power devices may be used with their fins vertical.
• What makes WiTricity technology unique?
I've looked through their patents and papers and haven't been able to put my finger on exactly what their intellectual property is. Magnetic induction has of course been around for ages. Tuning the coils using a capacitor goes back to drawings I've seen from Tesla himself. Is it the use of magnetic resonators? Do they have a specific method of achieving "highly tuned" coupling that I overlooked?
Sameh Elnaggar · University of New Brunswick
I believe the main contribution is using resonance coupling. This increases the transfer efficiency which now depends on the coils quality factors. I am not sure if Tesla used the same concept or not
• Syed Rizal Alfam Wan Alwi asked a question:
Can anyone help me find the reduction ratio as done so in the attached figure?
I tried using the methods mentioned but I cannot get the same reduction ratio of 0.33 like in Figure 4. And how do you determine the data to plot Fig 4 (a) and Fig 4 (b)?
Are there any good papers on the substitution method used in the design of oscillators?
I want to learn the basics of the substitution method. I guess it is used for optimizing oscillator designs. I've read the concept in Michal Odyniec's book on designing RF/MW oscillators. However I am still not clear. Hoping to gain some clarity here. Thanks!
Srikanth Pullabhatla · Larsen & Toubro Construction, Kolkata
Though I'm not from RF Oscillators research..... I suggest you to browse in IEEEXPLORE website which is a huge library of research papers...Mainly refer IEEE TRANSACTIONS papers as they have got much technical weight. Other than this go with ELSEVIER, EUROPEAN TRANSACTIONS, IET JOURNALS also.
Nikola Tesla's resonant circuit - Why does this circuit seem so complex?
Nikola Tesla (1856-1943) is considered to be the real father of our three-phase electric power systems. He's mind was ahead of his time with about 200 years . Perhaps one of the most impossible and incomprehensible idea he has was the transportation and distribution of electricity without using copper wires. Nowadays, we speak a lot about the lost electrical energy harvesting. We are living into an electromagnetic (EM) radiation field (electrosmog) that we created. One of the basis of Tesla's inventions is the resonant inductance (L)-capacitor (C) circuit. Seems to be a simple circuit, well explained here (thanks Cyril for the link): https://en.wikibooks.org/wiki/Circuit_Idea/How_do_We_Create_Sinusoidal_Oscillations%3F However, Tesla's resonant circuit was designed to amplify, rather than creating damped oscillations sustained by external power. See for example one of his patents (US718412/1905) here: http://www.rexresearch.com/teslamt/tmagxmtr.htm How was (is) that possible? International Journal of Practical Electronics is offering 200 euro prize for the best peer reviewed paper accepted for publication: http://www.sciencepubco.com/index.php/IJPE
Gregory Diana · University of KwaZulu-Natal
If you do this at the zero point of the current in each inductor during the resonant cycle then it is not a problem and almost all the energy will accumulate in the capacitor. As you see with the simulation it takes ~500 sec to build up to 40 kV. Tesla was getting 20 million volts. Note I only used sources of 12v. You are correct in that the "devil is in the detail".
Modeling of Permanent Magnetic Generator?
Does anyone have experience of modeling a PMSG on the d/q reference frame? I built one simple model according to the governing equation. The inputs are Vd, Vq and Omega. Outputs are id and iq. I set values for input variables which corresponds to zero d-axis value in a steady state of the generator. So I was hoping a zero id value would be obtained. But the results was not as that I wanted. I checked the equation and everything, seemed like nothing was wrong. Anyone had this problem before? Please tell me how to solve the problem.
Wei Zhou · Beijing Institute Of Technology
Thank you SO MUCH! Gregory.
What are the available techniques to operate smart grids?
How can smart grids be operated and how does the operation work?
Nabeeh Kandalaft · University of Sherbrooke MiQro Innovation Collaborative Center (C2MI) / Teledyne DALSA
Computational intelligence for smart grid optimization and planning http://www.fiercesmartgrid.com/story/computational-intelligence-key-making-smart-grids-really-smart/2013-10-09
• Nelson JAYAKUMAR Dhanaraj asked a question:
Is valve point loading an issue in modern day super critical boilers?
• Shanmugapriya Sumanth asked a question:
What are the current trends in contingency analysis?
Research topic in contingency analysis.
Could someone give me a concrete definition of the Vcc and Vac?
This question arose because a colleague holds that the alternating current must cross zero and change its' sign, while it is sufficient to the direct current to prevent the changes sign. I would like to ask for your support on the matter, I know that it is a very fundamental question but I could not convince him with my arguments, although my interest is to clarify any doubts on the subject.
Gregory Diana · University of KwaZulu-Natal
Douglas one could reason that DC is just AC at 0 Hz. That is why the general terms average value, RMS and Form Factor were developed as a basis to enable waveforms to be compared. If you look at any power systems of circuits books these form the basic definitions. However they are not absolute as you and Vasile correctly note. In the real world there're many applications for waveforms both linear and nonlinear, periodic and non-periodic and it is well known and understood that some areas require a more considered approach and that not all can be cast into a single unified definition.
Which instrument can be used to find out the harmonic content in the DC supply?
DC supply of 30 V and 200V
Douglas De Boer · Dordt College
Just looking at the output voltage vs. time on a conventional oscilloscope display (with AC coupling) will not reveal which harmonics are the worst, but at least will reveal the peak-to-peak ripple. If this is a linear power supply with a constant or nearly constant current load, there is an abundance of theory you could apply to the design to improve the "ripple filter." and thus no need to use more sophisticated instrumentation. However, if the load current is not steady, or worse yet is impulsive, or if the power supply is a switching type power supply, I'd use a spectrum analyzer or a network analyzer (set up as a spectrum analyzer). Some higher-end oscilloscopes are outfitted with FFT software. Those might be good enough, depending on how low you need the noise-floor of your instrumentation to be. These instruments will show you which harmonics are the worst and how strong they are. This will give you a better idea of how to design an effective filter. BTW sensitive inputs to spectrum analyzers, network analyzers, and oscilloscopes cannot withstand a direct connection to 200 V or even 30 V. Be sure to use appropriate voltage divider-type probes.
What are the scope and features of 2D transition metal dichalcogenides, to prepare by wet milling and used for energy related applications?
Graphene is not optimistic in semiconductor industry, on the other hand other 2D materials have lot of scope in it. I guess we cannot make defect free and lengthier 2D materials using wet milling. Is it a good option? Or should we go for CVD? We want to concentrate on supercapacitor, thermoelectric and Li-ion battery applications. I have to start from the scratch, so need some basic knowledge and hope you can suggest me good ones.
Gilles Lacour · DELACHAUX
For 2D materials vacuum deposit is a good solution, nearly any kind of material can be deposited in thin layer. I did a small dry supercapacitor using this technology 30 years ago. Now, vacuum technologies are no more expensive. For batteries I think that 3D materials are better. I hope this will help you
Is internet making us lose our skills to exercise our brain ?
Human brain is an amazing thing. What we call intelligence puzzled scientists for decades. Artificial Intelligence (AI) will not reach any level close to a human brain any time soon. Humans are amazing at things like object-oriented recognition. Our ability to recognize faces is a daunting task for a computer. With conferences, and journals dedicated to this topics, 100's of researchers couldn't even get us to the point, where there is a pattern recognition system that is as good as a human ... On the other hand, human brain is pathetic at tasks like multiplying two three- digit numbers. Who can calculate the result of 467*342 in less than a minute ? A computer can do a billion of these in a second ! Why so ? Because, human brain is simply not designed for these tasks, since it is not vital to survival. Object recognition is ... If you can't immediately recognize a lion attacking you, you have much bigger problems than knowing that, the lion is 1% bigger than the average ! With the internet, we now have a perfect world. We can do internet searches, we barely have to go to libraries anymore, we have our smartphones telling us when an appointment is due, and remember phone numbers. I wouldn't know my wife's phone number, if it wasn't programmed into my smartphone. If my smartphone died, I wouldn't be able to call my wife !!! Being so reliant on computers is great, in that, we are using the technology to help us. But, I can't stop asking myself, if this is making us lose the ability of our brain to perform other functions that we would otherwise be good at ? For example, remembering things. Even being responsible for remembering things ? Or, am I over-thinking this?
Tomy Patzelt · Czech Telecommunication Office
To tell it simply, we'll become the hostages of electricity. The return to the age of steam would be probably possible, although not easy. But without any IT based tools and gadgets.
How to simulate a BELBiC controller in matlab for transformer protection?
How to simulate BELBiC controller in matlab for transformer protection?
Aria Tsam · Aristotle University of Thessaloniki
How do I get controlled losses in a (solid) material?
I'm looking for a possibility to play with the losses of a solid material (from very low to tan(delta)=1 typically) in the 2-20 GHz range.
I. Golovin · National University of Science and Technology MISIS
You are not alone. Probably you mean that you are looking for materials from low damping capacity to hidamets - high damping materials, correct? There is a lot of literature about that. Or do you have more specific question?
Is a square wave signal digital or analog or neither analog nor digital?
In many examples we take square waves as digital signals. But a digital signal should be discontinuous in time and must have a finite amplitude level. Another explanation that negates a square wave being digital is " According to fourier analysis a square wave can be represented as the sum of harmonics of infinite number of sinusoidal signal". Hence we can say that a square wave is not digital in nature. As it has only two level of amplitude it would be wrong if one says that it is analog because an analog signal must have an infinite number of amplitudes, i.e. be continuous in amplitude.
Lutz von Wangenheim · Hochschule Bremen
It is not easy to give a satisfying answer. Is there really a common agreement that a unit step is to be "treated as a signal"? I am not sure about this. And - as you know, everyday used technical language is not always in concidence with (sometimes abstract) definitions. I know that it is common to speak about a "step signal" or a "squarewave signal". But if we try to be exact and in accordance with corresponding definitions, I think the unit step is NOT a signal. According to my knowledge, only a time-varying quantity that carries any kind of information can be called a "signal". May be I am wrong? On the other hand, a voltage step CAN be considered as a signal if its pure existence carries the information. Example: * A input step for measuring the step response of a system is not a "signal" * If within a certain communication system the existence of such a step at a certain time gives the user an information, it must be seen as a "signal".
I have started a Phd and looking for a topic in the field in DC partial discharge. Can anyone please suggest which area I should focus?
Partial Discharge in DC... Which area should I focus in this field. Thanks
Erik Isberg · IK Elektronik R&D
I would suggest the problem of water treeing in dielectric breakdown. This is of great practical as well as theoretical importance. Don´t be put down by negative comments. Asking Your peers for interesting subjects to pursue is a good and proper use of forums like Researchgate.
• Devi Dhurai asked a question:
Why pacifier cannot be used to address the crying baby problem in streaming application?
Pacifier mainly designed to avoid crying baby problems in wireless mesh network. But it cant address that problem in streaming application. I want to know the reason.
Can anyone suggest 2input 3output anfis loaddata, checkdata and traindata?
PID neuro fuzzy
Sundar Balan · Anna University, Chennai
How to take checking data from training data?