Matlab/simulink sample sharing for solving differential equations

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This sharing is about a student who asked about simulink Solve differential equation problems , So I'll share it with readers through this topic Matlab/Simulink Solve differential equations

The stem of the question is shown in the figure , This topic has 2 A special place

1、 Unlike conventional differential equations , give x3 The differential equation of

2、x1+x2+x3=8 It doesn't hold at the initial value ,

hypothesis 1： that x1+x2+x3=8 It must be established at the beginning , Then there is a problem with the initial value given by the topic , That is to change it into x1=x2=0,x3=8

hypothesis 2：x1=x2=x3=0 The initial value must be true , that x1+x2+x3=8 Don't consider at the beginning

Let's follow these two assumptions to solve

First, correspondence x1 and x2 Differential solution of , First write the differential part separately , Direct differentiation yields x1 and x2

The second step , Respectively according to the x1 and x2 Solve the corresponding differential equation of 1/s The number before the module , Red framed 8 It should be changed to 10, Thanks for your help and correction

The third step , Give to separately x1 x2 and x3 Corresponding initial value

In two different assumptions

hypothesis 1 The results are as follows ,

hypothesis 2 Under the circumstances , because x3 You have to give the initial value 0, Then you need to add an additional memory modular , to x3 initial value

give the result as follows

With the increase of simulation time , There will be errors reported by the non convergent system

Therefore, combined with the simulation results , Biased towards assumptions 1 establish , There is a problem with the initial value given by the title , That is to change it into x1=x2=0,x3=8