![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1296335/image.png)
How to solve this system of differential equations in Simulink ?
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I have to solve the following system of differential equations in Simulink. I have attached what I have done. I think there must be something wrong with the block diagram that I built, but I cannot figure out what. The independent variable is the time. ms, mu, cs, ks, ku, cu are constants. y is the road which I gave to the Simulink model as input using 1-D LookUp Table block.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1287625/image.png)
From which:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1287630/image.png)
It is a 2-DOF system coressponding to a vehicle. It has been obtained using the laws of motion.
I cannot figure what it is wrong with the diagram I created. Below is an example of why I am saying this. In the left picture is the kind of graph for SWS I would like to obain. In the right picture is what I actually get. It looks like, at the beginning, the SWS I obtain is ok, but afterwards, it is constanlty very close to 0, and it is not oscillating anymore like in the right picture. I guess there might be something wrong with input road (the y - 1DLookUpTable). Note, also, that the range is completely different. In the left image i goet values up to 300, while in the right image I get values of 10 to the power of -4.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1287635/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1287640/image.png)
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Answers (1)
Amit Dhakite
on 15 Feb 2023
Hi Patrausanu Andrei,
As per my understanding, you are not able to solve the system of equations in the simulink model. In you model, you have considered y and y_dot as the same entity. However, y and y_dot are different.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1296335/image.png)
Kindly try to correct the equations and modify the Simulink model.
For more information you can refer to: https://www.mathworks.com/help/simulink/ug/model-a-differential-algebraic-equation.html
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