Matlab: transfer function determination

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Discussion Overview

The discussion revolves around determining the transfer function of a two degrees of freedom (2 dof) vibration system using MATLAB, specifically addressing the challenges of avoiding manual algebraic operations in the process. Participants explore the application of Laplace transformations and MATLAB functions in this context.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant describes their differential equation model for a 2 dof vibration system and seeks a MATLAB method to determine the transfer function without manual calculations.
  • Another participant suggests rearranging the Laplace-transformed equation to isolate the transfer function and mentions using MATLAB tools such as tf, bode, and ltview for analysis.
  • A later reply reiterates the previous suggestion about rearranging the equation and emphasizes that manual calculation time is minimal for such systems, while also mentioning the use of dsolve for symbolic solutions.
  • The original poster expresses familiarity with the tf and bode functions but questions their applicability in systems with multiple degrees of freedom.

Areas of Agreement / Disagreement

Participants generally agree on the feasibility of using MATLAB to analyze the transfer function, but there is no consensus on the best approach for systems with multiple degrees of freedom, as the original poster raises a specific concern regarding this complexity.

Contextual Notes

The discussion does not resolve the specific challenges associated with applying MATLAB functions to multi-dof systems, and assumptions regarding the system's parameters and configurations remain unaddressed.

serbring
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I have a 2 dof vibration system, I have determined the differential equation of the model, can I determine the trasfer function readily with matlab, without using manual algebra operation?
In other word, I have that differential equation system:

[m]x''+[c]x'+[k]x=[f]

where:
[m] mass matrix
[c] damping matrix
[k] stiffness matrix
[f] external forces matrix

through laplace transformation I obtain:

s^[m]x(s)+s[c]x(x)+[k]x(s)=[f]

where s is the laplace variable, how can I find [f]/[x]?
I'm searching a way for estimating readily the transfer function of mechanical system, it is a loss of time to perform the calculation every time
 
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may anyone help me?
 
You've pretty much got the TF. Rearrange the laplace you've done above so you get f/x = tf (factorise the left side wrt to X). From there, you can use MATLAB to analyse the TF.
MATLAB tools(look in help): tf, bode, ltview.
The time required to manually calculate the TF is trivial for systems like this. You can use dsolve to get a symbolic solution to the ODE but it's not really necessary
 
ddarvil said:
You've pretty much got the TF. Rearrange the laplace you've done above so you get f/x = tf (factorise the left side wrt to X). From there, you can use MATLAB to analyse the TF.
MATLAB tools(look in help): tf, bode, ltview.
The time required to manually calculate the TF is trivial for systems like this. You can use dsolve to get a symbolic solution to the ODE but it's not really necessary

I know the tf, bode function, but how can I use them when the system has more than one dofs?
 

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