Hi, anybody ever done a simulation on a quarter car model suspension system to analyze the vehicle behavior when encountering a speed bump?

My question is, why doesn't my result show a reaction of the rear wheels when the front wheels encounter the speed bump. As you can see, there are oscillation, but the initial rear reaction is 0. This is not realistic. There should be some rear reaction. What is wrong in my model? I have altered the spring and damping constants to see the effects. However, the effects only happend after 05.s. So this is weird, changing these parameters should alter all the action and reaction movements. I have added the relevant files.

[Sam Chak]

Hi @sadat golz

You currently have three (3) unclosed questions that still require attention. If you're having trouble clicking the buttons or understanding the answers provided, feel free to request further assistance or clarification. Here are the links to your unclosed questions:

1. Graphs not showing despite values being displayed in the workspace: Link 1
2. No display on graphs despite using plot commands in the script: Link 2
3. Converting a boolean value to an integer: Link 3

On a different note, could you provide any scientific equations to support your claim that the rear wheel should immediately exhibit significant oscillation when the front wheel encounters a speed bump?

However, please keep in mind that the vehicle's center of gravity is slightly shifted towards the rear, resulting in a gravitational gradient affecting the rear suspension.

[sadat golz]

Hi @Sam Chak,

thanks for your answer, but as you can see when the rear encounters the speed bump at 0.7s, there is a reaction from the front. But does not make sence that when the front weheel encounter the speed bump before 0.5s. The rear wheel should exibit more reaction. Currently its 0.001.

This is also seen in the 0 force reaction at the rear, when looking at the force graph. There should be some spikes due to the coupling mass between the front and rear, but the force is litterally 0.

The given differential equation of this single track vehicle are:

Equation front: Z''_f= -[k_f(z'_f-z'_i)+C_f(Z_f-Z_i)+(m_c*(a*b)/L^2)z''_r] / (m_f+(b^2/l^2)m_c)

Equation rear: Z''_r= -[k_r(z'_r-z'_i)+C_r(Z_r-Z_i)+(m_c*(a*b)/L^2)z''_f] / (m_r+(b^2/l^2)m_c)

Answer 1

[Sam Chak]

Hi @sadat golz

I wanted to bring to your attention that it seems you accidentally deleted the graph that you had attached yesterday.

To be honest, I am uncertain about how to provide a technical response that is directly related to MATLAB/Simulink without referencing existing literature. If you believe that you have correctly executed the simulation based on the given equations of motion but are finding the results confusing, there are two possibilities: either you are seeking someone who can scientifically explain and validate the results, or you are hoping to 'bump into' a suspension expert in this forum who can identify any errors in your MATLAB script or Simulink model.

Could you review the following graphical representation if it makes sense to you?