Unable to find explicit solution

Question

daniel tarp 2022-11-9

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https://ww2.mathworks.cn/matlabcentral/answers/1846878-unable-to-find-explicit-solution

评论： Bjorn Gustavsson 2022-11-29

I have this equation which returns "Warning: Unable to find explicit solution" when i use solve on it, the equation and the variabel is symfun. And i am not sure what is wrong?

i have tried dsolve whit no luck same return.

i have tried with and without numerical values

tau_1 = diff(diff(L,diff(theta,t)),t)-diff(L,theta)
tau_m = Dm*(PS-PT)*alpha_m-Bv*diff(theta,t)
equ = tau_1==tau_m
thetadd = diff(theta,t,t);
THETAdd = solve(equ,thetadd)

and if more info is needed it can be provided

if someone have an idea it would help alot thanks

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Answer 1

Bjorn Gustavsson 2022-11-9

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1846878-unable-to-find-explicit-solution#answer_1094903

This looks like an attempt to derive and solve equations of motion with Euler-Lagrange equations. If that's the case there are tools to facilitate that available on the file exchange: euler-lagrange on FEX. The euler-lagrange-tool-package is the one I think I started using.

HTH