Question:Problem with Dsolve, error "unable to evaluate the partial derivatives of f(x,y) for stiff solution"

Question:Problem with Dsolve, error "unable to evaluate the partial derivatives of f(x,y) for stiff solution"

Maple

Hi,

I'm facing this issue when I try to use the Dsolve function in maple, it indicates me the following error :

"Error, (in dsolve/numeric/SC/firststep) unable to evaluate the partial derivatives of f(x,y) for stiff solution"

Here is part of the code :

```Lagerkraft:=rhs(Eq__Sys_4_ohneZwang[1][2])=0;
2
/ d        \
Lagerkraft := cos(phi(t)) |--- phi(t)|  a__ks m__k
\ dt       /

2
/ d        \
+ cos(phi(t)) |--- phi(t)|  a__sss m__ss
\ dt       /

2
/ d        \
+ cos(phi(t)) |--- phi(t)|  l__k m__ko
\ dt       /

2
/ d        \
+ cos(phi(t)) |--- phi(t)|  l__k m__p
\ dt       /

/  2        \
| d         |
+ |---- phi(t)| sin(phi(t)) a__ks m__k
|   2       |
\ dt        /

/  2        \
| d         |
+ |---- phi(t)| sin(phi(t)) a__sss m__ss
|   2       |
\ dt        /

/  2        \
| d         |
+ |---- phi(t)| sin(phi(t)) l__k m__ko
|   2       |
\ dt        /

/  2        \                                      /
| d         |                                      |   4
+ |---- phi(t)| sin(phi(t)) l__k m__p + 5000000 A exp|- ---
|   2       |                                      \  961
\ dt        /

2\
/            /phi(t) + Pi\                \ |
|100 Pi trunc|-----------| - 25 phi(t) + 9| | u + 200000 u A = 0
\            \   4 Pi    /                / /

indets(Lagerkraft,name)
{A, Pi, a__ks, a__sss, l__k, m__k, m__ko, m__p, m__ss, t, u}

Parameterliste__5:=[
A=4071.5*10^(-6),
a__ks=-20.94481*10^(-3),
a__kos=14.063837*10^(-3),
a__sss=0,
l__k=100*10^(-3),
m__k=11.02736,
m__ko=0.7237868,
m__p=1.437419,
m__ss=15,
u=1
];
[
Parameterliste__5 := [A = 0.004071500000, a__ks = -0.02094481000,
[

1
a__kos = 0.01406383700, a__sss = 0, l__k = --, m__k = 11.02736,
10

]
m__ko = 0.7237868, m__p = 1.437419, m__ss = 15, u = 1]
]

Lagerkraft5a:=subs(Parameterliste__5, Lagerkraft);
2
/ d        \
Lagerkraft5a := -0.01484538000 cos(phi(t)) |--- phi(t)|
\ dt       /

/  2        \
| d         |
+ 814.3000000 - 0.01484538000 |---- phi(t)| sin(phi(t)) +
|   2       |
\ dt        /

/
|   4
20357.50000 exp|- ---
\  961

2\
/            /phi(t) + Pi\                \ |
|100 Pi trunc|-----------| - 25 phi(t) + 9| | = 0
\            \   4 Pi    /                / /

indets(Lagerkraft5a,name)
{Pi, t}

Lösung_Lagerkraft:=dsolve({Lagerkraft5a,AB},phi(t),numeric,dsolve_options);
```

Thanks

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