Frequency Domain Analysis of Control Systems in MATLAB | MATLAB Tutorial
Articles,  Blog

Frequency Domain Analysis of Control Systems in MATLAB | MATLAB Tutorial

Hey guys welcome to yet another tutorial by MATLAB Helper today we will be talking about frequency domain analysis in control system frequency domain analysis is basically the study of how my signal amplitude changes with different frequency while time domain analysis shows how signal changes over time frequency domain analysis shows how signal energy is distributed over a range of frequency this is far more important because most of the application required the use of my frequency and how my energy varying now frequency domain analysis is very important and it find application in signal processing areas of communications, zoology, remote sensing image processing etc. to start of where we defining the system whose frequency domain analysis we want to perform we do that by the help of defining the transfer function command and enclosing our transfer function within it, if you need any help with transfer function you can refer to our previous tutorial so here i have my system object which define my control system which i want to analyze so frequency domain analysis we have lot of tools lot of plots quite simmiler to time domain for example we have the booth plot the nyquist plot the nicoles charge the poller plot the mandn circle so we would be starting by one of the most simplest plot that is the booth plot and in parenthesis i had been enclosing my transfer function object so booth plot basically it gives me two plots first is the magnitude response and second is the face response booth plot is a logarithmic plot and it gives me the magnitude of the Cyrano circle transfer function and phase angle in degrees which is omega now booth plot the use for stabilities studies of system with minimum phase loop transfer function and they help they can easily help in frequency domain specification calculation now another very common used plot is my nyquist plot i plot my nyquist diagram with the help of command nyquist plot now as you can see nyquist plot the nyquist diagram is just a single plot with x axis is the real axis and the y axis is the imaginary axis and it gives me a closed loop diagram now the position of the roots weather they lie within the circle or outside of it determine the stability of my control system; therefore i used the nyquist plot in stability analysis and its a great use now we will be moving on another plot which is very widely used and it is called the nicholes plot and the nicholes charge of nicholes plot whatever you called it its command again a very simple nichole plot and it gives me a sort of nicholes loop what it does it displays me the locals of log of the magnitude vs the argument of my transfer function it similar to the booth plot in terms of the fact that it is again a logarithmic plot you can determine that by the fact y axis is in decibel and decibels is a notation for logarithmic plot and it is used in lot of feedback control design and find several application now again similar to time domain specification we also have frequency domain specification of our control system and they help us in determining how my system behave bandwidth is a frequency domain specification that helps me how wide range of my signal is and another very commonly uses specification is the DC gain again the DC gain it helps me the gain of my system over particular range next i have my gain cross over frequency now what i simply do is in my gain cross over i do not just write the system in the parenthesis i have to follow this by the gain so for example my gain is 1 and then determine where is my frequency is crossing my system at the given value of the gains; as you can see if i just wrote the system it shows an error another very commonly used frequency domain specification is the peak gain; as the name suggest it helps me the highest value of the gain now these were is the few examples of frequency domain analysis specification if you have any questions you can leave then in comments below and don’t forget to keep watching MATLAB Helper Thank you


  • shivani singh

    This video deals with #frequency domain analysis which is used in variety of applications.there are various methods to find frequency analysis-using #Bodeplot#nyquistplot etc.

  • Disha Nikam

    #Frequency domain analysis is the study of how signal amplitude changes with different frequencies.Define a transfer function using the command #tf([ ]).For drawing a #bodeplot,use a command #bodeplot(sys).It gives magnitude and phase response.It is logarithmic plot.It is used to study stability of a system with minimum phase loop transfer function.
    For Nyquist plot we use command as #nyquistplot(sys).Here x-axis=real axis,y-axis=imaginary axis.It gives closed loop diagram.It is also used in #stability analysis.
    For obtaining Nichols chart we use command as #nicholschart(sys).It gives open loop.It displays a locus of log of magnitude versus argument of transfer function.
    The specification of frequency domain analyasis are #Bandwidth,#DC gain,#Gain crossover frequency,#Peak gain,etc.


    As we have seen about Time domain analysis we were forwarding to Frequency Domain analysis(FDM) which is crucial one for understanding our system. FDM tells about how signal amplitude changing with different frequencies.To analyse those we have #bode plot#nyquist plot.We have commands for Nyquist plot and Bode plot.Mainly these are used to know the stability of the system.

  • Harpreet Singh

    Overall the video explains the concept properly with a brief introduction of bode plot, Nyquist plot, Nichols chart about speciation’s it is clearly described as what is the necessity of it. Few modifications can be added (like making the code general for any values)
    otherwise it is easy for a learner to learn the concept with that good video editing and the soundtrack.

  • Parth B

    Demonstrations and theory was great, of framing of the functions used could also be explained it should be perfect!

  • heena lulla

    The best thing about vedio is concept of every tiny action is explained very beautifully. According to my suggetion the programme and results should be zoomed for proper view.

  • Sowvik Aditya

    Really nice video with a clean presentation.
    All these predefined functions in Matlab is very much case sensitive. Especially these two methods "getGainCrossover"[where 'G' and 'C' must be in capital] and "getPeakGain"[where 'P'and 'G' must be in Captical] must be given too much attention. So these phenomena could just be mentioned in these video for complete perfection. But it is good to learn those things by hands-on mistakes.


    very nice video for understanding frequency domain analysis and to study it's implementation using matlab.It shows how signal and it's energy changes over frequency.
    Nichols plot is new thing I learn it is useful in feedback system.

  • Arti Kumari

    Voice quality is low. Sound must be audible. And the video gives ideas about bode plot, nyquist etc but it may expplained more.

Leave a Reply

Your email address will not be published. Required fields are marked *