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Rajiv Singh


MathWorks

156 total contributions since 2011

Software developer, controls and identification products
Professional Interests: system identification, signal processing, controls

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Answered
The system identification models I've exported to my work space do not match the results from the toolbox. Why is this happening?
What initial conditions are you using for simulation? Note that by default, the App estimates the initial conditions to maximize...

7 months ago | 0

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Submitted


Data based modeling of nonlinear dynamic systems using System Identification Toolbox
Perspectives on nonlinear identification using a throttle valve modeling example.

3 years ago | 10 downloads |

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Answered
Transfer function from ARX-model
Does the example on http://www.mathworks.com/help/ident/ref/idnlarxlinearize.html help?

4 years ago | 0

Answered
Suggestion for System id toolbox
How about: NoiseModel = noise2meas(IdentifiedModel); Then use NoiseModel as a regular LTI model in Simulink and run it wi...

5 years ago | 0

Answered
How do I model a time series in MATLAB using ARMA?
You should evaluate the quality of prediction results and perform some correlation analysis of the model residuals to verify how...

5 years ago | 0

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Bump ---> Identification using invfreqs
Have you tried using the weight input argument? You can specify higher weights for the frequencies around which you are interest...

6 years ago | 0

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how to create a state-space model without disturbance and how does the disturbance influence the solution
The difference between the output of the model and the actual (measured) output is, in general, not going to be zero. So, there ...

6 years ago | 1

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Answered
How to use the under knees code of state space model "ident" toolbox in mfile
Double click on estimated model icon. A window containing information on the model is shown. This window offers commands that wi...

6 years ago | 0

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Answered
Use N4sid for system identification (for new data estimation)
Computing response of a model to a given input is called simulation. Use the idParametric/sim command for that as in: Ud = i...

6 years ago | 0

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Answered
How to define a polynomial orders ARX model [na nb nk], for a MISO system
Look up the documentation of delayest on how to put some limits on the values to be tested. Delay can also be determined by a st...

6 years ago | 0

Answered
improve the performance of system identification MISO
There are different types of choices to consider to get the most out of an identification: * Model orders: controlled by orde...

6 years ago | 0

Answered
initial state in n4sid
Note that N4SID always estimates initial states when using time domain data; the InitialState option does not really help here. ...

6 years ago | 0

Answered
Problem with ident GUI while predicting time-series
When predicting, the results depend upon the initial conditions. The GUI estimates the initial conditions to maximize the fit to...

6 years ago | 0

Answered
Prediction confidence intervals using a state-space model
For discrete-time systems, the forecasting model is same as the simulation (original) model. So you can use commands such as SIM...

6 years ago | 1

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Answered
system identification command line- impulseest
The "60" refers to the length of the FIR filter. An FIR model typically has larger number of coefficients than a rational transf...

6 years ago | 0

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Answered
system identification gui - fit to estimation data
When the amx3322 model was estimated, it was estimated to minimize the 1-step ahead prediction error. The fit value between the ...

6 years ago | 1

Answered
How to design controller with control toolbox tools
You could try something along the lines of: m0 = idtf(ir, [1 zeros(1, length(ir)-1], 1/48000); m1 = balred(idss(m0), N); %...

6 years ago | 0

Answered
What is the criterion of best fit in system identification toolbox?
Normalized Root Mean Square (NRMSE) criterion is used to generate the fit % number. It is a measure of how much better the model...

6 years ago | 1

Answered
My model output is different with use of Simulink and sim function
For iddata source, it helps to set Tstart to 0 since the simulation in Simulink starts there by default. That is, use: XX = idda...

6 years ago | 0

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Answered
how to use the model which is done by System identification toolbox?
Did you set the initial conditions correctly? See: http://www.mathworks.com/matlabcentral/answers/72338-how-fix-the-problem-...

6 years ago | 0

Answered
how to find parameters (A and B ) for a non linear arx model and how can i convert this non linear arx model into transfer function
"Converting" a nonlinear model into a linear one is an exercise in linearization. See idnlarx/linearize and idnlarx/linapp funct...

6 years ago | 0

Answered
About the underlying principle of the function "predict"
The prediction is based on computing a kalman filter. See chapter 3 in "System Identification, Theory for the User", 2nd ed, Len...

6 years ago | 0

Answered
Model generated by system identification tool when transported into simulink, does not match and is unstable
Hi Saurabh, Could you try running the SIM command in the MATLAB Command Window (e.g. y = sim(pss3, input)) and check if the sim...

6 years ago | 0

Answered
Is there a way to output the final simulated time-response from procest()?
Ah, I see it now: it is the InputOffset that you estimated or supplied during process model estimation but perhaps did not speci...

6 years ago | 0

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Answered
Bode diagram of poor input/output signal
bode(sys,[w1 w2],'.'), where w1 and w2 are your two input frequencies and sys is the identified model.

6 years ago | 0

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Answered
Identification of MISO / MIMO models based on transfer functions: poles multiply contained in resulting model
The repeated poles are probably a result of concatenation; do pole(ss(zpk(rss(2,2,2)))) to check this phenomenon. You can use SM...

6 years ago | 0

Answered
Is there a way to output the final simulated time-response from procest()?
Hi James, If the estimation focus is "simulation", you should not really see this difference. What MATLAB release are you seein...

6 years ago | 0

Answered
How to fit data into nonlinear model
Is there an input/output relationship among the 2 variables? That is, does changing one affects the other in a cause-effect mann...

6 years ago | 0

Answered
What are the 7 states for the model?
Can you elaborate on what you mean by "defining the states"? If you want to calculate the state-trajectory (as a function of tim...

6 years ago | 0

Answered
What is the cost function in the optimization problem of the pem and greyest functions for multiple outputs?
The weighting matrix by default is inverse of noise variance which is simultaneously estimated along with the model parameters. ...

6 years ago | 0

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