Spring and Damper Elements in Mechanical Systems

I just have a question for a model of dynamics system , I am suppose to do the g(s)=x(s)/F(s) then assuming the F(s)=10; I want it to see how I can plot all the results of the transform function. I wanted to plot the position , velocity and each mass of a total (3 masses with different springs and dampers). Which function I use to plot velocity and each mass. The position is plotted with the step function that I know . well thanks !

Answer 1

[Star Strider]

I am not certain exactly what you want to do. If your equations are now in the Laplace ‘s’ domain and you have all the constants, there are two methods that you can use.

• Symbolic Math Toolbox: Enter your equations, then use the partfrac and ilaplace functions to transform them into the time domain. Exploring the frequency characteristics is somewhat more difficult with the Symbolic Math Toolbox, but is possible. You have to write your own functions to plot them. If you want to explore the mathematical properties of your system in a symbolic context, the Symbolic Math Toolbox may be best.
• Control System Toolbox: Specify that you want your transfer function in the 's' or 'z' domain (see the tf function documentation), then create your model and simulate it in the time domain with the lsim function. You can also use the bode function to see the frequency characteristics of your system. You can also get Nyquist plots and root locus analyses.

I prefer the Control System Toolbox for problems such as yours. See the documentation for the introduction sections of both Toolboxes to see what works best for you.

[alberto ortiz]

yes I think the step function is to determine the position, I was thinking about the lsim will show the velocity due to being in time domain, will you recommend the impulse function to show the mass ? thank you very much for all

[Star Strider]

My pleasure.

Either the impulse function or bode function (to show the effect of the mass on the frequency of the system) would both work.