ODE solve give very spiky response ?

Forum|Forum|3 years ago
November 15, 2022
13 replies
4321 views

To all

I am looking at the ODESolve with a “saw tooth” input (y’’) and I get a very spiky response – see attached (mcad 15 wsheet will follow)

Why is that?

Tried different time steps but always get this rather spiky response

Thanks

John

Best answer by AlanStevens

Works better as set of first order equations:

Avoid numerical differentiation wherever possible!

Alan

V

ValeryOchkov

24-Ruby IV

Try to convert one 2-d ODE into two 1-st Odes!

W

Werner_E

25-Diamond I

Would suggest that you attach your worksheet.

Would adding more steps in odesolve (third, optional argument) be of help?

Maybe worth a try although i guess that the problem stems from the numeric derivations and not from the result of odesolve.

Hard to be of more hep without having the sheet to play with.

L

LucMeekes

23-Emerald IV

I guess Amax=20 and tf=0.011. What are your values for and ?

If they are 3 and 5 respectively I get:

Success!

Luc

P

prop_design

15-Moonstone

odesolve use to be mathcad's best solver. however, their statespace solver is much better. the help and quicksheets can get you started. if you want some example files, I can post them. the users here on the forum helped me get a pwm input working. i haven't tried a sawtooth wave but i expect it would handle it well. the nice thing about the statespace solver is it can handle a lot more inputs than odesolve can.

J

JXBWk

Author

14-Alexandrite

can't find the option to edit original post ! attached mcad 15 worksheet.

The Prime 8 conversion is not quite working. Does not like the y''(t) notation

1_odeissue_1---Copy.zip