Transfer function + controller + Bode plot and root locus

Hi
I am trying to plot Bode plot and root locus for trasfer function
TF = 1/(s^4 + 2s^2)
Then I want to implement Ideal compensators (PI , PD or PID) or lag/lead compensator to get the required stability
I am trying to do this Labview 8.o in control design and simulation loop. (V2.0)
I have done some simulation but I am not understanding as to how implement controller on this.
I need little help.
I am attaching my VI. but you will find rootlocus not there and feed back loop control to implement controllers not there
Thankyou

I have one typical controlers question where I am using feedback control
alongwith compensators. My transfer function is like fourth order
TF = 1/S^2(S^2+2)
but rootlocus and transfer function in labview do not let me write equation more than 3rd order.
How can I write this 4th order equation.
Next I want to make one feedback control on this transfer function and then want to plot bode and rootlocus.
I have made one vi of fourth order by placing transfer function in series and then for feedback gain I have placed another transfer function with feedback. I have also attached rootlocus vi but it does not show me rootlocus since rootlocus Vi can not take more than fourth order transfer function.
I want to plot my step response, bode, and root locus for step input
I have also tried to make another VI with tansfer function VI which has feed back terminal in it, but I donot know how to get bode and rootlocus out of that.
I am attaching my both VIs for you.
see my two Vis please.
Attachments:
Bode_practice.zip ‏156 KB

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How to use Fuzzy Logic Controller for transfer function in labview control and simulation loop?

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Attachments:
fuzzy in simulation loop.JPG ‏52 KB

Hi Sankhadip,
Sorry for the late response. I was looking at your code and
I noticed that the graph scale does not start from zero. That might be the
reason why you don't see the transient in the simulation. To change the scales
simply double click on the lower limit and set it to zero. If this is not the
expected results, can you please post the expected results, so we can see what are the
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Thanks and have a great day.
Esmail Hamdan | Applications Engineering | National
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Replace Control & Simulation plots (Bode/Step/Root Locus) default control with Silver Controls

I just installed the 2013 trial version of LabVIEW and LabVIEW Control Design and Simulation Module. Normally, for control design I only use Matlab/Simulink but LabVIEW does have some advantages and I want to take these advantages. The problem I feel it is annoying is that I cannot use the Silver Controls to replace the default classis style control - like the bode gain and phase margin or root lotus plot below
Solved!
Go to Solution.

Hi muahang,
why not? What's the problem here?
Those plots look like standard XY graphs (maybe with some fancy background graphics for the root locus)...
Best regards,
GerdW
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I need a sample vi that can plot a transfer function given zeroes and poles (It should allow the user to input zeroes and poles). It should be done in the S domain.The user should be allowed to put poles and zeroes, with frequency

I need a sample vi that can plot a transfer function given zeroes and poles (It should allow the user to input zeroes and poles). The user should be allowed to put poles and zeroes, with frequency. DONE IN S DOMAIN.

I have created a VI (LabVIEW 6.1) that does what you want. Note that the poles and zeros have to be entered correctly that is in Rad/s and typically with negative real part. The VI offers you all options for lin/log frequency axis, magnitude in dB or not, phase in Radians or Degrees etc...
The VI is written with "academic" in mind, so it is not optimized for performances but (hopefully) for clarity. I hope this will work for you.
Attachments:
S-Domain_Transfer_Function_from_Poles-Zeros.vi ‏167 KB

I need a sample vi that can plot a transfer function given zeroes and poles (It should allow the user to input zeroes and poles)

I need a sample vi that can plot a transfer function given zeroes and poles (It should allow the user to input zeroes and poles). The user should be allowed to put poles and zeroes, with frequency.

Check the answer to your other posting
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=50650000000800000052A90000&UCATEGORY_0=_49_%24_6_&UCATEGORY_S=0

Multiple transfer functions in one bode graph

How can I plot multiple transfer functions in one bode graph? Can someone point me to an example
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Go to Solution.

Li,
First, if you use the mouse to grab the top of the plot legend and "pull" it up, multiple plots will appear. The graph node will expect multiple inputs. Does that solve your problem or is there more to it? If it doesn't it would help if you would post the code you have so far.
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************ kudos always appreciated, but only when deserved **************************

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Can anybody please help with the below question.
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Does it work? Quantify! Show us it is working
Hand in a short report on the PID project on the cruise control of the LEGO MINDSTORM NXT Robot. Your report should contain an introduction to cruise control and uses of PID controllers, a brief explanation of how PID feedback control works. The printout of the Block Diagram and Front Panel of your LabVIEW program should be attached at the end of your report.
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Here are some things that may be addressed: Check whether your system can stabilise speed to within 1%. What are the optimal PID parameters that you have found? Can you choose PID parameters to both reach the set speed quickly and also maintain the speed within good accuracy once the system has reached the set speed? Can you control the speed of small steps? Explain your results?

Thanks for that.
DanHarryman wrote:
HI ToolMonkey
You should be able to build control system to do this using PID control VIs. The following paper is a good place to start when working with PID systems.
http://www.ni.com/white-paper/6440/en
Let me know how you get on using some of the functions in this.
Thanks
Dan.H
UKAE

I have transefer function like (1/(s^2+s+5)) and i have a square wave input , i want to use this transfer function with this input to see the output , how can i do that , with example please.

i need to know also how to represent this transfer function in labview, try to send me example. answer me at my mail

"st" wrote:
> answer me at my mail
give a valid e-mail first, and your name, we don't like to help anonymous
people
> try to send me example.
how much do you pay ?
> i have transefer function like (1/(s^2+s+5)) and i have a square wave
> input , i want to use this transfer function with this input to see
> the output , how can i do that
First you have to know what you are doing, like an engineer : you have a
Laplace, continuous time transfer function but LabView handles discrete
signals only. Use matlab/simulink if you want to simulate continuous time
systems easily...
If you definitely want to use LabView, the first step is to discretize your
continuous-time transfer function, i.e. decide a sampling rate and convert
it to a "z transfor
m". Then you can directly use the "IIR Filter.vi" as I
said earlier.
Philippe Guglielmetti - www.dynabits.com me at my mail

Specifying the numerator and denominator of the transfer function equation

hi
I am going to simulate the second odder problem. But I have problem when I try to define the 2nd odder transfer function
by using externally. I have attached the VI in this mail .
any information in this regard highly appreciated
thanking you
danushka
Solved!
Go to Solution.
Attachments:
second_order_systerm_8.2.vi ‏80 KB

Hello Danushka,
You would need to create a control from the transfer function. Then on the front panel, just expand the denominator column to get zero and first order for the denominator as shown here. Let me know if this helps.
Andy Chang
National Instruments
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Hi
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Hi Ankit,
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Hey pflo,
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http://zone.ni.com/devzone/cda/tut/p/id/3560
http://zone.ni.com/reference/en-XX/help/372458B-01/lvsysid/bode_plot/
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PID root locus

I have open loop function 31.75/(s^3+3*s^2+1.25s) I am trying to design PID controller for this using given percentage overshoot n settling time. I m using root locus graphical technique to do it. I have design PD controller and PI controller separatleti I want to know how can i desing PID controller andits transfrom function .I also want to know how can i determine the PId compensator gain.Please provide any related information as i m new in it.
Dost

Hi
Thanks for reply.well for the time being using LAbview or matlab is not an issue infact I am desinging P dcontroller and calcualting the parameter of Kd and Kp.open loop transfer function for my problem is : 31.75/s(s+2.5)(s+0.5) .
you can see there is an integrator in the open loop and theortically it should nt give any steady state error the close loop function obtained from this openloop with feedback is:
5.286
---------------------------- the step respons of the close loop function shows a unbounded system ;any comments on it????? should we include 31.75 the numerator of the open l
s^3 + 3 s^2 + 1.25 s + 31.72
loop in the calcualtion of the close loop?
i developed aPD compensator using graphical root locus techniques using the following time doima specification overshoot 10% settling time 10 secod.the desired pole from this specification is -2.-+2,76i which gives from gemoetry the position of the required zero as -1.24 using this zero does not give the required specification so i used z=-.3 (any comments on it)I am also perplexed about the calculation of the Kd :from graphical root locus methos i have used following formula
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the obtained PD compensator is :
0.2866 s + 0.08599 and coreesponding open loop P Dcompensator is :
9.09 s + 2.727
s^3 + 3 s^2 + 1.25 s
the close loop is obtained as
1.515 s + 0.4545
s^3 + 3 s^2 + 10.34 s + 2.727
this gives settling time 3 second overshoot is 16 % but steady state is .167 i.e about 99 % steady state error.
Looking forrwad for ur reply.
Dost

Re: how to make bode plots in Labview 7.1 without using Control Toolbox

I am using Labview 10. I have connected a signal generator, a LP RC filter and an oscilloscope. I am using Labview in order to control the generator (sine with frequency sweep) and acquire the signal from the scope. I want to plot the Bode diagram without using the transfer function, from the amplitude of the sine signal and the frequency.
Thank you very much.
Best Regards.

Hi pflo,
Are you using the CD Bode Plot VI or the SI Bode Plot VI? For the CD plot you must use a transfer function. Below, please find a link to an example on how to create a Bode plot without using the toolkit.
https://decibel.ni.com/content/docs/DOC-14762
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Kira T

Error in Mathscript (FOPDT Transfer Function)

Hi all, i am trying to write a First Order Plus Dead Time system into the mathscript, unfortunetaly i found that it appear an error (please refer to the attachements), do anyone have idea or approach to write an FOPDT Transfer function in mathscript?
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Solved!
Go to Solution.
Attachments:
error.png ‏18 KB

Thank you very much barp, both method work for me, but now i had face another problem.
I had try your method and design the PI controller, but the result (overshoot) is different compare to the result (overshoot) by using Matlab.
I had try to copy and paste the code from the Mathscript to the Matlab and step plot it. Consequently, the overshoot shown different value.
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The value of the transfer function : Gain = 58.46; Time constant = 0.55 and time delay = 0.06.
The value of Pi controller : Kp = 0.0784 and the Ti = 0.24.
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Attachments:
matlab1.png ‏24 KB
labview bd1.png ‏28 KB
labview bd2.png ‏43 KB

Bode plot

Hi,
Is it possible to obtain bode magnitude plot and phase plot from FFTed frequency response curve without using the transfer function?how
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A bode plot is by definition a drawing with the poles and zeroes of the transfer function of a system.
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Old analog instruments used a sine sweep and a peak detector for amplitude, instead of FFT, very cool, but a bit tricky to get the phase response.

Transfer function + controller + Bode plot and root locus

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