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# Electromechanics - Science topic

Explore the latest questions and answers in Electromechanics, and find Electromechanics experts.
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Hello All, I simulated a resonator in comsol and I use electromechanical physics. I need displacement in result and I want cir physics at the same time to add resistance. Is it possible?
Me simulate the B-H curves to V-I of different magnetic materials used in transformers to study the inrush patterns in transformers, could refer my paper “ Laboratory methods to generate inrush current patterns of power transformers “….
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I mean, in articles, everyone refers to the piezoelectric charge constant d31 or the electromechanical coupling factor k33 or the piezoelectric voltage constant g15 and so on, as if it is the most natural notation in piezoelectricity to state the constants in function of the axes, as described here:
In my view, it is not such a trivial notation that one can understand naturally without studying it. However, very rarely is any explanation given about this notation and the vast majority of articles begin to present piezoelectric constants without the slightest clarification of what they refer to. Even review articles! I already saw the notation of d11 and d33 in an article from 1934, therefore not recent at all:
But I cannot find a reference source where the convention of this notation is defined.
In short, I want to write "the coefficient d33 according to the notation by [citation X]." Is there any convention or standard that we can refer to?
Refer to IEEE standards on piezoelectricity,
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Is there anyone using an electrochemical working station CHI660E for characterisation of electromechanical performance of piezoresistive pressure sensor?
Could you suggest source, references or web sites about the using process?
Nurhan Onar Çamlıbel The CHI660E electrochemical workstation is specialist equipment for electrochemical research and testing. It is often used to characterize the electromechanical performance of piezoresistive pressure sensors, as well as a number of other electrochemical tests.
You may get additional information about using the CHI660E workstation by searching online for user manuals, technical documentation, and application notes for this instrument. The manufacturer's website, academic research papers, publications, and internet forums or discussion groups devoted to electrochemical measurement and testing are all viable sources of information.
Contacting the manufacturer directly may also be beneficial, as they may have more extensive information and resources regarding utilizing the CHI660E workstation for piezoresistive pressure sensor characterization. They may be able to provide you with more advice, technical assistance, and references to get you started with your measurements.
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I am working on an electro-mechanical system for which PID tuner gives best step regulation with settling time of about 80s. But as it is commonly observed, ILC leads to step regulation with negligible settling time after several iterations, Is is possible for delayed system too? If yes, what should be approach (P, PD, PID or anything else) in ILC update function? Please share your experience and some literature!
Thanks
Dear Naveed Mazhar , yes you can use the parametrization method to tune PID controller, please see the following:
Book: Quantitative process control theory. Vol. 45. CRC press, 2011.
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Basically, I am doing M.tech project on damage detection using piezoelectric sensor by obtaining change in Electromechanical Impedance (EMI) plot for this I want plot between conductance/susceptance vs frequency.Can anyone Suggest how to do this .I am getting some result in my analysis which I have attached below which I have obtained through modal analysis but i feel this is right way to do it.Please anyone guide me
Please have a look at these articles which can give you some idea on the question you are asking:
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i am designing RF MEMS Switch, for that i need to solve two physics i.e. electromechanics and electromagnetics. And i need to use the results of the electromechanics to solve electromagnetic physics. i doing the entire project in COMSOL tool.
now my questions are:
1. In electromechanics:::  I kept the gap between the cantilever the the base is 0.8um, but when i apply the actuation voltage i am getting the displacement more than o.8um, here base material is silicon dioxide in solid state. [shown in figure 1]
2. In electromagnetics::: the rf input signal is not propagating to output through displaced cantilever , here i tried to match the impedance but theree is no use. [Shown in Figure 2]
3. how to use the results of one physics as the initial values of other physics. [shown in figure 3]
Each physics can run respectively, how can I couple the two physics together? I have tried to add two studies. Disable the laminar flow and run the solid mechanics using study 1, then disable solid mechanics and run laminar flow using study 2. In study 2, use "Initial value of variables solved for" "study 1".
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To study the Dual Fed Induction Generator principle in closed loop arrangement, I want the least possible motor generator set, example I want 0.25 HP or less than that system. Any specific make is available, please suggest.
Thanks you so much Mohamed Azab, your answer helped me a lot.
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The specifications are in term of R, L, B, J, kv, kt
The max output force of  electromechanical  braking system is 3500N
Hi, I initially face a same problem in my research. It solved :)
Kindly refer my publication attached.
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Which method has the highest sensitivity for SHM evaluation using piezoelectrics: ultrasound or electromechanical impedance?
Both methods could be very sensitive. It depends on the frequency. However, ultrasonic guided wave are able to monitore surfaces. The impedance measurements are (to my knowledge) monitore effects next to the sensor.
What system you choose depends on the problem you want to solve or monitore.
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I want to find data about oil viscosity, water in oil, metallic wear debris particles for condition monitoring for electromechanical systems. The data should be monitored by online sensors because the sampling period of offline analysis is large. Let me know if you have any suggestion.
Your order is in the lubricant centers of interest to you
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I did the simulation using electromechanics module in comsol but, ended up getting solution which shows variation (not a smooth curve) with parametric sweep (changing the dimensions of the plate with small iteration). I am a beginner in comsol and any help in this domain will be helpful !
is there any other software which could solve this problem ?
In principle the smoothness of a curve is defined with the mesh size. In Ansys I have the possibility to define the fineness by mesh operations. I don't know if Comsol has this feature.
Additionally, Ansys has an energy-difference sensitive refinement iteration build in. I can define how precision the entire solution (and electric field distribution) must be. This is a rougher method because it "waste" a lot of computing power.
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how it operate?, what are it uses of in the industry?
Muhamad arif ashraf abd satar ..... Good question… Please check references below.. hope it will be helpful for you…
Regards…
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I have mostly seen composites made of piezoelectric ceramics layered with magnetostrictive alloys for the demonstration of the magneto-electric effect.
My understanding is that piezoceramics are typically softer (easier to deformation) and have a higher electromechanical coupling than piezoelectric single crystal materials like quartz and LiNbO3.
So they seem like a more obvious choice for magneto-electric devices.
But are there examples of magnetoelectric devices using a single crystal material layered with a magnetostrictive material? And would there be any benefits to this arrangement?
I am curious if any particular device structures might be beneficial, instead of just layering the materials.
I have seen 0-3 PZT/PvDF composites in the past.
I found this:
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I'm actually investigating the RFD proprieties in aging and so I need to describe alsothe electromechanical delay (EMD). Interestingly, with my current acquisition apparatus, the delay is really short (<40ms) while when I analyse the data from a different one (same software and hardware brand) the delay is consistenly higher (around 100-150 ms).
Excluding the EMG wave summation's effect and the variability within/between subjects, can it depends from the apparatus itself? Does someone have the same problem?
And more generally, could the EMD be so dipendent from the apparatus to invalidate every usefulness of absolute data?
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I prepared PVDF-ceramic composite thick film (dimension is 1cm x 1cm x 0.45 mm)and I want to know, how can I determine the electromechanical coupling factor of this sample. what is the formula used for this and what is the experimental/measurement technique to determine the electromechanical coupling factor.
Kindly help me to resolve this problem.
Dear Chandra,
Thank you very much for such information.
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The sample machine has been fabricated with 110N-m ....
The maximum torque is inversely proportional to the D-axis synchronous inductance. If you are able to make the air gap longer or reduce the number of turns you can decrease the D-axis synchronous inductance value. Reducing the stator leakage helps also a bit. Another alternative is to drive the machine with increased voltage (if there is room for extra flux in the magnetic circuit and efficient enough cooling).
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I need to open a poppet valve which face a pressure up to 20 bar. The result is that there will be 7000 newton and I need a very fast opening (few milliseconds) for a 7.5 mm stroke.
The only actuator which go closer is this pneumatic one(http://www.smcpneumatics.com/pdfs/smc/70AMGP.pdf) but it could reach 400 mm/s. For my purpose I would need something around 3000 mm/s.
So, is there anybody who knows some different types of actuator, even electrical, piezo etc. with this features
-7000 N
-up to 3000 mm/s speed
-7.5 mm stroke
Thank you
Saif,
The original poster requires an actuator that can shoulder a load of 7kN for a significant fraction of the stroke. Parker makes no ETT actuators with that ability.
I doubt that any linear electrical actuator will have this combination of speed and strength. Other methods have merit.
(a huge solenoid? a pneumatic ram?)
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i want to use the servomotors but i don't know that hoe much torque is required, so i can buy the appropriate motor..
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We are working of six small hydropower projects each plant has two francis machines with capacity of 3.5 MW to 15MW and head 32m to 65m. What could be the reasonable E&M cost for those plants.
Thanks Luis,
My problem was for Hydropower plants and not for chemical plants.
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Several papers tend to bring in generator torque, and also electrical torque, which I think is the same thing as electromechanical torque. The issue is that all these terminologies get mixed up so I tend to be confused . Apart from the wind torque, every other torque in the WT system is confusing right now. So please help with an explanation and diagrams if possible. Thank you very much
In general case, electro_mechanical torque is the torque that is specified in motors, that is when u give a electrical energy it is converted to the rotational force for this rotational force a torque is produced this torque is called electromechanical torque. in simpler words the torque produced in mechanical parts by the electrical source then it is called as electro mechanical torque.so the generator is not related with this electro mechanical torque hence it is nothing but a torque required to the generator produced by the wind.
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Hi all
I would like to know, what is the dynamic range of gyroscope and how the dynamic range of a MEMS gyroscope is estimated during mechanical structure design.
Thank you
Jayaprakash Reddy
Hello Jay,
It's better to refer to the datasheet of the specific gyro that you are using. It must have been specified by the manufacturer. It varies from device to device (the sensors).
Alternately, first evaluate what is the signal range of (estimated) your mechanical system and then choose a gyro to accommodate this range.
I hope this will be helpful to you.
Thanks and best wishes!
-Prasanna Waichal
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I know generally it contains a maze of channels and passages that direct hydraulic fluid to the numerous valves which then activate the appropriate clutch pack or band servo to smoothly shift to the appropriate gear for each driving situation. How exactly the process occur?
Dear Uma,
i advice you to see this video:
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Hi,
I think that you have done excellent work in validating that the magnetic micropropellers can be used for medical purposes. In your IEEE 2017 article (Rubbing Against Blood Clots using Helical Robots: Modeling and In Vitro Experimental Validation) you reported a linear approach velocity and magnetic frequency relation while the removal rate started to drop beyond 35 Hz. Could it be that the decrease in the removal rate is due to a decrease in the step-out frequency of the propeller because of "wall effects", which is the blood clot in this case? My other question is, will multiple propellers simultaneously rubbing the blood clot improve the removal rate?
Thank you,
Michiko
Hi Michiko,
The presence of an optimal (as in Fig. 9) rubbing frequency is attributed to two reasons. First,  the helical robot is swimming against flow rate of 10 ml/hr. Therefore, at low frequencies it does not generate enough propulsive force to overcome the flow and the rubbing is not effective. Second, at high frequency the damping increases and result in a decrease in the removal rate.
As to the contact, our model takes the contact force into consideration (Eq. 4). We have also characterized the frequency response of the robot during contact with the channel but without rubbing, and the relation is almost linear (Fig. 9). The step out frequency is beyond the range we studied.
Do not hesitate to contact  any of the co-authors if you have any questions :-))
Islam
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The Best COMSOL module for Piezo electric Polymeric Substrtates which uses SAW, FPW etc., Acoustic modes. Kindly suggest the best out of 3 with explanation??
a) Structural Mechanics
b) Acoustic
c) MEMS modules
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Dear colleges,
I am working on a parallel robot where the actuated joints are in one leg, i.e. q1 and q2 in the figure.
Then, I have problems with inverse geometry model (IGM) and kinematic model.
In terms of the IGM, I obtain the equations by suppressing the passive angles:
from the left leg: (x-q1)^2+(y-q2)^2=l^2
from the right leg: (x-d)^2+y^2 = l^2.
However, it seems to be impossible to solve q1 and q2. Is there another way to get IGM for this model?
Also, I differentiate the geometry model and get the kinematic model, which has a similar problem.
A[dx; dy]+B[dq1;dq2] = 0
But the B is a matrix [2(q1-x), 2(q2-y);   0 , 0];
I guess the main difficulty is because all the actuated joints are in the same leg.
Dear Zhongmou Li
Yes also i think so that difficulty is because all the actuated joints are in the same leg.
Actually, there is little research on (model and control) the parallel robot with one leg.
However, here are some attached files that interest from near or far the subject.
Best regards
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Will it be a sine wave of very low amplitude....which is not effected by the change in resistance of a particular arm??
Thank you Prasanna Waichal
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What piezoelectric coefficient is considered in stretching mode and how can we calculate it. Is there any specific equipment for this like d33 meter.
Regards,
Hello,
You can take a look at our paper on measuring g31 coefficient of PVDF during stretching. I hope it can help.
Boris
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I'm designing a log periodic toothed planner antenna for frequency range (400 MHz-5800 MHz). Anyone can help me out how can I calculate the exact no. of teeth that give resonance on specific frequencies.
Situ Rani is there any calculations/formula to find out geometric ratio and spacing factor or we have to choose it randomly? Suppose i want to design it for (400-5800) MHz then how i'll do all the calculations?
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We are performing micro machining with Electro Chemical Machining (ECM)  process. We look forward for a mechanism to maintain constant gap between electrodes during machining
All so speechless?
We speak of ECM, and the work gap is defined by tool, electrolyte path and workpiece. Electrically, these are the two double layers between the electrodes and the electrolyte (resistance in parallel of the double layer capacitance) and the ohmic resistance of the electrolyte (electrical flow field). Therefore, if the working gap is to be kept constant, the voltage drop across the electrolyte must be constant. Since this distance is increased by the removal, this distance must be adjusted back to the desired degree.
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I want to measure the phase lag (time lag) between LDV vibrometer and other equipment such as voltage and current probes with accuracy of 1 degree (~nanoseconds). Unfortunately, the vibrometer has a "response delay" in micro second order, comparing to ns order "response delay" in current and voltage probes. For measuring with nanosecond accuracy I should get rid of sensors response delays.
I am using a Polytech OFV-3001 LVD using velocity decoder (based on doppler effect) for measuring displacement/velocity around 20kHz-50kHz frequencies.
Have you tried matched filter?
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If I apply a DC voltage on peltier element, will the source voltages changes or not?
A well regulated source should not change its voltage one change in load.
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Over the past few years, a number of handheld devices that report nanoparticle concentrations have become commercially available. Several of these devices rely on an electrometer detector, which measures the charge of deposited particles (incl. the Testo DiSCmini, Naneos Partector, and Aerasense NanoTracer). Several studies on the accuracy of these devices have been published by leading research groups e.g. BAUA, IDAEA-CSIC, IGF, IUTA, INRS, U of Iowa and TUT. These studies report that the measurement accuracy is mostly within ±30% for a particle size range from 20 nm to 300/400 nm. I would be interested in learning how vibrations and mechanical shocks impact that measurement accuracy during mobile aerosol measurements, e.g. in a moving vehicle.
Disclaimer first: I invented the DiSCmini and the partector, and sell the partector, so I have a conflict of interest here.
Dear Oliver,
you would first have to define "vibration" and "mechanical shock" to get a definite answer. I have often taken DiSCmini or partector devices with me when walking, cycling and, infrequently, in cars. We have had long-term deployments (2 years each) of DiSCmini and Partector devices on Trams and Buses of public transport. I have never seen any real issue with the performance of the devices. A bit more quantitatively, I once took a DiSCmini in a backpack with me while riding a bicycle and put a filter on the inlet and simply recorded the electrometer signal, and analyzed the noise in the end, which was identical (+-10%) of what I got in stationary testing.
That said, in all these modes of transportation the devices only see weak accelerations. If I drop a partector or a DiSCmini from a few cm on a hard surface (table, floor), I usually see a spike in the electrometer, so in principle there could be effects if the accelerations are too great. For normal operation, I don't think it's relevant, but to answer your question in more detail one would have to really measure the accelerations quantitatively along with the electrometer signals.
I have heard that the TSI FMPS is sensitive to vibrations (the PSI group had to mount it very carefully in their mobile lab, with shock absorbers etc.). I once put an electrical diffusion battery (which uses similar technologies) in the same mobile lab for comparison with the FMPS and we didn't have to do anything regarding the mounting, it just worked fine. I'm not sure where this difference comes from; my hypothesis is that since the FMPS is a much larger device, the insulators will see much larger forces during accelerations - because F = m*a and m is much larger so for the same acceleration larger forces are applied. Insulators can exhibit piezoelectric and/or triboelectric effects which I would suspect are at work here. By keeping m low, such effects can be minimized. One more good reason for building miniature devices :-)
If you are at ETH conference next week we can do some experiments at our booth where we squeeze, shake and drop partectors and watch the signal in real time on a PC.
best regards
Martin
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I want to make a set up for micro-edm machine in which workpiece will vibrate with the help of PZT actuator. I want to understand how power amplifier connected with it? And also, how can i create different frequency and amplitude of vibration. I have heard function generator does this, but how?
PZT actuators can be actuated using a voltage amplifier or a charge amplifier. Charge amplifier will reduce the hysteresis of the PZT. Chose the amplifier based on your piezo specifications and voltage ratings.
Normally a PZT actuator has a very high bandwidth >20kHz, therefore creating different frequencies is possible below the bandwidth of the actuator.  You can use any real time interface(eg. simulink real time with dSpace/ speedgoat IO boards) to generate your frequency signals and feed into the amplifier.
I used a Speedgoat IO104 FPGA with simulink real time to generate signals.
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Hi,
I am trying to find variation in capacitance between two plates with applied body load. I defined an air box around the plates. Now I'm trying with electromechanics physics for applying body load and finding capacitance. I defined the two plates as linear elastic material. Applied body load to the moving plate. I applied 1V to moving plate and fixed plate is grounded. I also gave parametric sweep for body load. But capacitance is not varying with body load.
Thank You,
If you do not enable non-linear geometry under your Study node, you essentially have zero displacement between the plates, no matter the body load. Perhaps you would fine some inspiration in the "bk 4134 microphone" under Application Library.
-René
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Why biaxial stretched dielectric elastomers have higher electromechanical actuation in comparison to uniaxially stretched samples even if we take same thickness strain?
Biaxial pre-strech can eliminate the instability of dielectric elastomer actuator to avoid electrical breakdown. The actuation strain highly depend on how you apply the forces, biaxial or uniaixal.
You may refer to the following publicastion:
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Attempting to measure slew rates (of a large electromechanical assembly) as low as 0.1mrad/sec
There is a lot of encoders out there. Starting with encoder pickups (e.g. avagotech.com) and ending with encoders with digital interfaces transmitting angle and number of revolutions (e.g. heidenhain.com).
Searching for "rotary encoder" will reveal more hits than you can ever check.
Another term would be "angular sensor"/"angular position sensor". These are typically some kind of magnetic sensor (GMR, AMR, TMR) - delivering sin/cos signals. (Just like the AS5048 Ron Reiser described above.)
Last but not least: if you've got a toothed wheel with many, many teeth, you can use a hall sensor that will deliver one or two pulses per tooth.
The most important thing may be to have measurement periods >> 1 s as all these sensors have practical limits at about 5000 inpulses per revolution. Or to use a gearbox, rotating the sensor pickup at a higher speed than the machine itself.
There are many ways to do it. It is up to you to assess what's applicable in your environment.
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While measuring D33 coefficient on piezoelectric ceramic pellets, that have been polled in DC electric field and silver electrode platted by D33 meter, a positive D33 coefficient is observed every time, no change of sign of coefficient occurs upon changing side of pellets. So my question is, should the sign of d33 coefficient be changed when reversing pellet or it is always positive? If not, then what might be reasons for this?
It is always a good practice to check the d33 measurements on both sides.
your measured d33 values should be approximately the same, but opposite in sign, this indicates effective poling treatment given to your samples.
K. Sreenivas
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To make coding for arduino mega, we need to know the suitable angle to make the leg of a quadruped robot can move smoothly and from calculation we can enter the angle at coding to move the robot. Because when we know the equation, it will be easier to compare with trial and error to find the best angle that servo motor turn to move the legs.
In physics simulation you can try different maximum angles and compute the forces in the joints and check the smoothness of overall locomotion. By utilising genetic algorithms or reinforcement learning methods of your preference. Then you should easily find appropriate parameters.
You can also have a look here:
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While using EDM for different inputs Roughness is varying . What is the min roughness and range that can be attained by EDM Cutting
Hello friends,
Let's talk of  WEDM and the best Ra values. Whence such values as 0.8 µm to come; or 3 µm; or µm?
Of course I can reach such values, if I let a strong influence on surface and through lead wire EDM with pulse durations of 20 to 200 µs.
First of all it must be clarified what kind of material to be cut. The next question is what Ra values are to be achieved. Can the machining with a main section made or must be re-cuts.
With reputable WEDM equipment you should come without problems less than 1 µm (Ra) in a productive main section. Today, it is also not a problem with a main section under 0.5 microns (Ra) to come. With appropriate after cuts Ra values are 0.2 µm feasible.
Basically, we need to re-discuss with the W-EDM of hard metals and ceramics.
Best regards
Hans-Peter
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Is there any other method to measure piezoelectric coefficient besides using Piezo response force microscopy ( PFM) for thin film piezoelectric MEMS such as AIN?
Laser Doppler Vibrometer (LDV) are also used by some to measure the displacement of thin film AlN.
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I have a smart bean coupled with two piezoelectric patches and I want to control it using Simulink. In order to do so, the modal matrices that have the eletromechanical properties, are necessary.
In order to control a piezoelectric stage, you don't need to extract all of mechanical properties of your stage, so I propose some steps:
1. Specify your important points: You have some important points in your mechanical stage, for example maybe your stage is a table and then roll and pitch angles are important.
2. Excite model's actuators: Excite piezoelectric elements one-by-one and record the movement of each important point.
3. Build the stiffness matrix: Now you can build the stiffness matrix easily.
4. Mass matrix: For the mass matrix you can use modal analysis in ANSYS and with the calculated natural frequencies and the known stiffness matrix, it can be easily computed.
5. Damping matrix: You can build damping matrix directly from K and M by mechanical properties that you entered in ANSYS material definition.
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Identification of the servo electromechanical actuator, held directly on the real loaded actuator experimentally is the most effective way for determining its structure and parameters. Thus obtained mathematical model can be used for both velocity/position closed loop design and verification of analytical modeling.
I I want to discuss this issue for preparing common research paper further.
Dear Leonid,
I’m a member of a research group which deals with high-performance motion control systems. We develop special purpose identification algorithms for flexible electromechanical systems based on the estimation of plant frequency response. We also work on the problem of model-based controller design for the automatic commissioning of electric drive systems. You can find some of the results in the research papers published on my RG profile. Feel free to contact me, I’m open to any kind of cooperation on this topic.
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hi
Are Mechanical and Electromechanical Time constants in any sense different and related to electric time constant?
Thanks
The electromechanical time constant is the time needed for servo to speed up from zero to a nominal no load speed, with stall torque acting and no load torque present on the shaft.
The mechanical time constant is the time needed for servo to speed up from zero to a nominal speed, with nominal torque acting and no load torque present on the shaft.
The electrical or armature time constant is the ratio of armature inductance L and resistance R, and it is not directly related to electromechanical or mechanical time constant.
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Hi, i want to simulate the thermal stress effect (e.g. temperature and heat flux) on prestressed eigen frequency analysis of a MEMS model which has built in "Electromechanics" and has input voltage, but i haven't seen any changes in results in natural frequencies, like COMSOL ignoring the thermal stress physics for eigen frequency analysis. can anyone help?
Hello Mahdi,
What you need to do is to add two study steps, "Stationary" and "Eigenfrequency". "Stationary" study should perform the stress analysis. Results from this study need to be passed to "Eigenfrequency" study for successful implementation.
This can be done automatically by selecting "Prestressed Analysis, Eigenfrequency" study. A few such examples with this study type are also present in COMSOL Model Library.
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Hi all
I have read an example in the electric machinery book by Professor Bimbhara in the chapter related to electromechanical energy conversion. There, he calculates the force exerted to the rotor due to an increase of airgap by x in one side and a decrease by x in the other side. His calculations show that if the airgap is not unifirm, then there will be a radial force on the rotor, in the direction with the lesser gap length. My question is regard his calculations. As we know, the force can be calculated using: F=B^2/(2mu0)*surface area that the flux passes. It seems to me that using this equation, there are still equal forces on the rotor if the airgap length on one side increases by x and decreases by x in the other side. This is because the airgap flux density (B in the equation) is equal on both sides.
How could you justify that book's derivation?
The key concept is variable gap permeance.  For an off-center rotor, the closer gap has a greater permeance and the further gap has a lesser permeance.  The permeance varies around the rotor circumference.  For a given excitation current, the permeance determines the magnetic field,  which means it is not the same for each pole. The rotor force is the surface integral of the magnetic stress: Fx = Integr(sigma*R*L*cos(q)*dq,0,2*pi); sigma=B^2/2*mu_knot; B=mu_knot*N*I/(g-x*cos(q)).  q is angle from 0 to 2*pi.  So your force integral is: Fx=B0^2*R*L*integr(cos(q)*dq/(g-x*cos(q))^2/2*mu_knot,0 2*pi), where B0=mu_knot*N*I/g.  The integral is difficult, but you can expand the integral in a Taylor series for small x.  After some algebra, the reference equation 2.72 is achieved with the second term approximated as (x/g).  [Math is hard to write when limited to text.]
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Can anyone help about using the PID controller based in PLC devices to control reactor temp.? Thank you
Hi
I'm not sure about what exactly is the problem.
Do you require info on using the PID controller in the PLC. If this is the case then you should consult the manual or look online.
Do you require to tune the device? Then you should consider using tuning methods like ZN or any other of the popular methods.
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Besides the above answer, optimisation of turbine speed using echocardiography guidance should be also performed. Some patients may develop VTs that could be ablated in an expert center. The implant is only the first step, most of the care is required after...
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What type of actuator(s) is/are suitable for simultaneous axial and torsional fatigue loading on a cantilever round bar with frequency of 5 Hz in load control range of 0-8000 N and 0-25 N.m respectively? I have found Direct Drive actuators both for linear and rotary. I have also choices of linear servomotors and piezo actuators as linear actuators. Concerns are:
• No backlash.
• achieving the loads with no motion as it is a cantilever beam
• 1 million cycle of loading (regular maintenance can be considered during the test)
Hi
I am not in any way an expert on this topic so please treat my thoughts on the matter with caution.
Electrodynamic shakers usually are used for frequencies higher than 5 Hz as their mass-spring resonance is this ballpark or higher frequency.
Piezoelectric actuators are stiff, can take lots of load cycks and some may generate the force required but they tend to be hard to drive as their load is reactive, i.e. you would need a serious amplifier to drive them. In any case, they are worth considering and a good place to start looking may be here http://www.physikinstrumente.com/products/integrated-piezo-actuators.html
The other way to go would be to consider servohydraulic excitation. Again, this is not cheap and the premier supplier would be MTS (http://www.mts.com). Hydraulic excitation can easily do the loads you require, MTS shakers are fatigue rated and can take the load cycles you specify. The main limitation would be minimum displacement amplitude which is limited by internal stick.slip effects in the shakers. The MTS shaker I have toyed with managed to go down to the ball park 1-0.5 micrometer. Other limitations will be on velocity and governed by flow rates in control servos. The suggested frequency 5 Hz should be easy for a hydraulic shaker.
If you are on a tight budget, you may want to consider resonant excitation, i.e. you design a simple, e.g. mass-spring type, system to be at resonance at 5 Hz. You should then be able to find a low cost way of driving this system and use the resonance to amplify your loading.
Last, one should not bang one's own drum but, if you want to determine structural properties during your test, you may, or may not, have use of looking at this reference to study the effects of massloading of combined force/moment excitation. https://www.researchgate.net/publication/256801180_Direct_measurement_of_moment_mobility_Part_I_A_theoretical_study?ev=prf_pub
Sincerely
Claes
• asked a question related to Electromechanics
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I am studying the mechanical properties of the inhibitory jaw reflex evoked by the electrical stimulation of the upper lip in man (I record bite force by using an isometric force transducer between the anterior teeth, and I record bilateral EMG from both masseter muscles). In the course of my study, I found that the reflex relaxation had a slower onset and lasted longer than the corresponding period of suppression of electromyographic (EMG) activity. While the latter finding is exactly as one would expect, the former is, arguably, more surprising.
The mean latencies of onset of this response were: biting force, 52.7ms (SD:9.5ms); right masseter EMG, 37.9ms (SD:4.3ms); left masseter EMG, 38.5ms (SD:4.7ms). The latency of the bite force response was significantly longer than those for either EMG (Repeated Measures ANOVA with Bonferroni corrected paired t tests: P<0.0001). The onset of the force reduction was delayed comparing to the EMG inhibition by about 14.5ms. This was not due to any inertia in the force transducer.
When trying to find an explanation for this delay, I came across the Poggesi et al. paper (see below). Do you think this delay could be explained by the feedback mechanism between attached cross-bridges and thin filament activation? Or this mechanism couldn't last for 14ms and therefore it might be something else? Could it be due to more than one factor?
InsyAllah I will explain in detail soon.
• asked a question related to Electromechanics
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I am interested in any Ideas in improving the classical solutions known for bimetal actuators .
Mihail AIGNATOAIE
Tech. Uni. Iasi, Romania
Dear Mihail AIGNATOAIE,
You look this site. There can be you will find the answer of your question.
Best regards, Shafagat
• asked a question related to Electromechanics
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I am trying to model a position control problem with simulink simscape components. The following components are used. 1. PI(s),H Bridge , controlled PWM , a comparator to generate a direction for H bridge, DC motor, Gear box, and spring representing gear box stiffness and a load as inertia ,inertia of the order of 10e6 kg*m^2, and suitable PS-S and S-PS blocks and a ideal rotational reference sensor.
2. When i try to simulate the system the system works and tracks the input with few SS error and with small oscillation. Now i am required to tune the system using PID tunning.
As i understood prior to tuning of the plant I am required to linearize the plant and the only i can apply automated PID Tuning.
I tried the linearization of the plant with system identification using simulutated I/O in the PID tunning tool box. During this i observed the instead of tracking step command the output continuously increase like a ramp. Can any one help to solve the issue ?
Also I  attached two plots one with simulation result with P=1 and I=1 and running simulation for 40 sec( tried upto 200 sec) , the observation is that output is trying to track the input value of 0.01 degree , but during the system identification the output looks like a ramp and not settling , the figure pid.png show system identification GUI. Any clue for solving the issue?
Thanks & regards
Prima.R