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motor transfer function problem

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ibrahim03

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dc motor transfer function

I want to find out the transfer of a DC motor for modeling it in Matlab , Simulink.
For this i referred to my course book, Control Systems Engineering by Norman N Nise.
In the book the DC motor was modeled and the formula for its transfer function was given.

But the problem is that the brushless motor that i am using , has a built in tachogenerator which gives out pulses according to the speed of the motor and also it has an input control voltage from 0 to 4 volts which is used to control the speed of the motor.

Now my question is that in this case how do I find the transfer function of my motor ?
Will the transfer function be the same as that of an ordinary DC motor ( without any built in tachogen and speed control) ? If not then what will be the difference?
 

motor transfer function

Control systems always need feedback. If you want to control motor speed, you need it to be fed back so as to control optimally. You can use any mathematical forms, but, they usually use controller transfer functions. Then, according to their own criteria, they optimize the control system coefficients.
 

speed control system transfer function

Control systems always need feedback. If you want to control motor speed, you need it to be fed back so as to control optimally. You can use any mathematical forms, but, they usually use controller transfer functions. Then, according to their own criteria, they optimize the control system coefficients.
Click to expand...

What you said is right but my problem is that I dont know anything about the transfer function of the controller which is built into the motor. I have to design a feedback control system which regulates the speed of the motor according to the load on it. Also i have to model my design in Matlab. How can i do that when i dont know the actual transfer function of the motor and its in built circuitry.

In other words if I want to find out the transfer function of an unknown system (the motor and its in built circuitry in this case), is there any method for that ?

(I know a method to calculate the transfer function of a 'first order' system by analysis from its step response but is there any similar method to find out the transfer function of a 'second order' or higher order system ? )
 

2nd order control system transfer function

Sorry for my mistaking what you want. If you want, I can send you some presentation material that I made several years ago. I have just translated it into English for you. Just give me your e-mail address. I wonder if this material will be helpful to you.

Added after 16 minutes:

The contents of the presentation material is as follows:
Title: Control System and MATLAB
1. Mathematical Models of Physical Systems (MATLAB and Simulink used)
2. System Modelling
State-Variable and Output Equations
Transfer Function
State-Space Form
MATLAB Representation in An M-File
3. PID Control using MATLAB
Open-Loop Step Response
Proportional Control
Proportional-Derivative Control
Proportional-Integral Control
Proportional-Integration-Derivative Control
4. DC Motor Speed Modeling
Physical Setup and System Equations
MATLAB Code using Transfer Function
MATLAB Code using State-Space Equations
5. PID Design for DC Motor Speed
Controller Transfer Function
Design Goals
MATLAB Code
Optimized Result
6. Modeling DC Motor Position
Physical Setup and System Equations
Design Goals
MATLAB Code
Optimized Result
7. PID Design for DC Motor Position
Controller Transfer Function
Design Goals
MATLAB Code
Optimized Result

I had made this material from the resources in the internet. But, now I cannot remember the sites.
 

    I

    ibrahim03

    Points: 2
    Helpful Answer Positive Rating
transfer function for motor

sounds like your feedback is a sort of voltage to frequency converter. how many pulses per revolution? this information should be enough to build a transfer function for the feedback.

your feedforward 0 to 4V control is taking that voltage and converting it into a speed which can be translated into torque. the more torque the more speed. where 0 equals zero torque and 4V equals max rated power.

goodluck,
Mr.Cool
 

transfer function of dc motor

No, Mr.Cool. I used neither voltage-to-frequency scheme nor pulses. The physical motor is modeled using some frequently used mathematical tools and directly solved using MATLAB and/or Simulink. It can be directly (in my sense) implemented in analog and/or digital manner.
 

transfer function motor

Ok I am attaching the datasheet of the motor I want to model. Can anyone please explain the steps of making a mathematical model of this motor. Also if anyone has some articles regarding the mathematical modeling of dc motors please post it.
 

transfer funcetion problem with solution

i think if U dont know about model mathematic of motor U can see in modern control by ogata

and after U know that U can use matlab toolbox in Simulink to simulate it..

i hope this will help U
 

transfer function problem sheet

ibrahim03 said:
What you said is right but my problem is that I dont know anything about the transfer function of the controller which is built into the motor. I have to design a feedback control system which regulates the speed of the motor according to the load on it. Also i have to model my design in Matlab. How can i do that when i dont know the actual transfer function of the motor and its in built circuitry.
Click to expand...

Your BLDC already has electronics with speed control. Speed will be independant of load untill maximum is reached. To model it, you have to measure it. Data given in data sheet does not give nowhere near information about system behaviour, as you already concluded.
Sweep input with various frequencies and amplitudes and under various loads including various amplitudes of steps. By measuring frequency, amplitude and phase on monitoring output you can measure frequency, phase and step response of your system. Then from your data you can try to model it and fit it under curve that is satisfactory for desired tolerance.
Click to expand...
 

dc motor mathematical modeling+transfer function

What if I treat the motor as a black box system ? There is a toolbox in matlab which can be used to find the transfer function of a system by input and output data. How would that be ? any suggestions ?
 

matlab coding for dc motor

ibrahim03 said:
What if I treat the motor as a black box system ? There is a toolbox in matlab which can be used to find the transfer function of a system by input and output data. How would that be ? any suggestions ?
Click to expand...
That's identification toolbox, right?
May be u can use 'unit-step' test signal to obtain the transfer function...

Interesting links, no harm to pay a visit...
**broken link removed**
**broken link removed**
 

    I

    ibrahim03

    Points: 2
    Helpful Answer Positive Rating
transfer function position control system

I have a similar problem now but as far as my case is concerned i have to build a controller (position control) in matlab for a ptz camera ( dome camera ).PC is physically connected via RS232 with it.How can i find its transfer fcn?Any ideas would very very helpful!!
 

unit step funcion for dc motor

hi sir,

I am also facing same problem to find the Transfer function of position controller system using a BLDC motor and feedback is a encoder.

if you know how to find the transfer function of a position control system please help me.............

mail: pramod.syscontrols@yahoo.in


regards
Pramod
 

how find transfer function of dc motor

Pramod-chavan said:
hi sir,

I am also facing same problem to find the Transfer function of position controller system using a BLDC motor and feedback is a encoder.
if you know how to find the transfer function of a position control system please help me.............
mail: pramod.syscontrols(at)yahoo.in
regards
Pramod
Click to expand...

A simple but working position control system (xy-plotter) is described in "Modern Control systems" by R.C. Dorf. But realize that there is not only one solution for the design of a the controller (e. g. lead-lad or lag or ....). In most cases it will be sufficient to model the DC motor alone like a P-T2 system (proportional with a second order delay).
 

matlab pid coefficient from transfer function

Hello

I am currently working on a project that requires the transfer function of the dc motor in order to simulate it with matlab... can you help me ??

I appreciate any kind of help !
 

Re: 2nd order control system transfer function

yjkwon57 said:
Sorry for my mistaking what you want. If you want, I can send you some presentation material that I made several years ago. I have just translated it into English for you. Just give me your e-mail address. I wonder if this material will be helpful to you.

Added after 16 minutes:

The contents of the presentation material is as follows:
Title: Control System and MATLAB
1. Mathematical Models of Physical Systems (MATLAB and Simulink used)
2. System Modelling
State-Variable and Output Equations
Transfer Function
State-Space Form
MATLAB Representation in An M-File
3. PID Control using MATLAB
Open-Loop Step Response
Proportional Control
Proportional-Derivative Control
Proportional-Integral Control
Proportional-Integration-Derivative Control
4. DC Motor Speed Modeling
Physical Setup and System Equations
MATLAB Code using Transfer Function
MATLAB Code using State-Space Equations
5. PID Design for DC Motor Speed
Controller Transfer Function
Design Goals
MATLAB Code
Optimized Result
6. Modeling DC Motor Position
Physical Setup and System Equations
Design Goals
MATLAB Code
Optimized Result
7. PID Design for DC Motor Position
Controller Transfer Function
Design Goals
MATLAB Code
Optimized Result

I had made this material from the resources in the internet. But, now I cannot remember the sites.
Click to expand...



Hi,

Can you forward the same to my mail ID. villuribhanu@gmail.com
Thanks in advance.

Regards,
Bhanu
 

yjkwon57

2nd order control system transfer function
Sorry for my mistaking what you want. If you want, I can send you some presentation material that I made several years ago. I have just translated it into English for you. Just give me your e-mail address. I wonder if this material will be helpful to you.

Added after 16 minutes:

The contents of the presentation material is as follows:
Title: Control System and MATLAB
1. Mathematical Models of Physical Systems (MATLAB and Simulink used)
2. System Modelling
State-Variable and Output Equations
Transfer Function
State-Space Form
MATLAB Representation in An M-File
3. PID Control using MATLAB
Open-Loop Step Response
Proportional Control
Proportional-Derivative Control
Proportional-Integral Control
Proportional-Integration-Derivative Control
4. DC Motor Speed Modeling
Physical Setup and System Equations
MATLAB Code using Transfer Function
MATLAB Code using State-Space Equations
5. PID Design for DC Motor Speed
Controller Transfer Function
Design Goals
MATLAB Code
Optimized Result
6. Modeling DC Motor Position
Physical Setup and System Equations
Design Goals
MATLAB Code
Optimized Result
7. PID Design for DC Motor Position
Controller Transfer Function
Design Goals
MATLAB Code
Optimized Result

I had made this material from the resources in the internet. But, now I cannot remember the sites.


Can you Pl send me the copy of the material...my email id is
lokesh.27111@gmail.com

thanks in advance
 
Last edited:

Re: 2nd order control system transfer function

yjkwon57 said:
Sorry for my mistaking what you want. If you want, I can send you some presentation material that I made several years ago. I have just translated it into English for you. Just give me your e-mail address. I wonder if this material will be helpful to you.

Added after 16 minutes:

The contents of the presentation material is as follows:
Title: Control System and MATLAB
1. Mathematical Models of Physical Systems (MATLAB and Simulink used)
2. System Modelling
State-Variable and Output Equations
Transfer Function
State-Space Form
MATLAB Representation in An M-File
3. PID Control using MATLAB
Open-Loop Step Response
Proportional Control
Proportional-Derivative Control
Proportional-Integral Control
Proportional-Integration-Derivative Control
4. DC Motor Speed Modeling
Physical Setup and System Equations
MATLAB Code using Transfer Function
MATLAB Code using State-Space Equations
5. PID Design for DC Motor Speed
Controller Transfer Function
Design Goals
MATLAB Code
Optimized Result
6. Modeling DC Motor Position
Physical Setup and System Equations
Design Goals
MATLAB Code
Optimized Result
7. PID Design for DC Motor Position
Controller Transfer Function
Design Goals
MATLAB Code
Optimized Result

I had made this material from the resources in the internet. But, now I cannot remember the sites.
Click to expand...

please send me that material I need someting like that A SOON AS POSIBLE!!!! MY E-MAIL IS "hocakita@hotmail.com" please
 

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