FAQ  •  Login

Magnitude of initial residual

Moderators: Dan Negrut, RaduS

<<

f14-tvoss2

Newbie
Newbie

Posts: 17

Joined: Mon Sep 08, 2014 2:08 pm

Unread post Sat Dec 13, 2014 4:14 pm

Magnitude of initial residual

Hey y'all,

I was hoping that you could post your initial residual for project 2.

Mine is starting around 10^5, which seems waay too high. Just want to check if others are getting these kind of numbers.

residual = [Psi; Omega]
<<

f14-jwhendricks2

Newbie
Newbie

Posts: 21

Joined: Mon Sep 08, 2014 2:08 pm

Unread post Sun Dec 14, 2014 1:39 pm

Re: Magnitude of initial residual

My code takes forever to run but I get the right results. My first iteration I have a magnitude around 4.5*10^3 but at the second iteration it drops to about 0.3.

This is probably a long shot but earlier I was getting a magnitude around 10^5 and my program was diverging. After a couple hours I finally realized it was because I was multiplying M*q instead of M*qdd for the top equation in the residual. Maybe you're making the same mistake? Most likely not, but it's worth a shot.

-Jake Hendrickson
<<

Dan Negrut

Global Moderator
Global Moderator

Posts: 833

Joined: Wed Sep 03, 2008 12:24 pm

Unread post Sun Dec 14, 2014 5:01 pm

Re: Magnitude of initial residual

how large is the step size?
In principle, if the step size is small the residual should be small.
Think about it - in the limit, if h goes to zero, then the residual should be zero (since this would be the residual from the *old* time step, t_n).

If you got this running really well please post your first residual to that other people get a ballpark idea.
thank you.
dan

Return to ME451 Fall 2014: Kinematics and Dynamics of Machine Systems

Who is online

Users browsing this forum: No registered users and 1 guest

cron
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group.
Designed by ST Software.