Look up table for a dynamics problem

I am currently running an analysis for a Quarter Car suspension Model using an M-file. I have manually derived the transfer functions and entered them into the M-file to get a magnitude plot which I am happy with.

This has been done using a constant spring force. I would now like to make this force variable dependant on the movement of the wheel. So basically the more the suspension compresses the higher the spring force becomes.

Is it possible to define this using a table? So eg. between values of suspension compression 10mm and 20mm the spring force is 30000N/m and between 20mm and 30mm the spring force is 35000N/m. I would then like to feed this back into the M-file to run it.

Answer 1

[Nirmal Gunaseelan]

One way to do this would be to create a MAT file with the data (there are some interpolation functions to generate the data automatically if you so desire) based on your variables and store them. While computing, you could load the MAT file and continue with your script.

Answer 2

[Fangjun Jiang]

I see more serious problem with your approach. You are simulating your model using MATLAB. When you say transfer function, do you mean it in a general sense which means a mathematical function, or do you mean it in a specific sense, like the transfer function using Laplace transform.

I would assume you mean transfer function using Laplace transform. So keep in mind that will require your system to be linear. The spring force is likely to impact your transfer function. With a constant spring force, you derived your transfer function, then you want to simulate the transfer function but you want to change the spring force again dynamically? It's possible to do it in MATLAB or Simulink but you do need to think about whether it will give you the correct result. I'll find some useful link and post it later.

Here is the link to the post.