Non smooth plot, undesired points in chart.
Hello collegues,
I have a modell in motionview, and I locate an output of the torque applied in a rotational motion. The motion follows the next expression:
`STEP5(TIME,0,0,0.5,(185*3*(2*PI/40)))+STEP5(TIME,0.5,0,1,(-185*3*(2*PI/40)))+STEP5(TIME,1,0,1.5,(185*3*(2*PI/40)))+STEP5(TIME,1.5,0,2,(-185*3*(2*PI/40)))+STEP5(TIME,2,0,2.5,(185*3*(2*PI/40)))+STEP5(TIME,2.5,0,2.75,(-185*3*(2*PI/80)))`
When I plot the results of the torque, I obtain the attached chart, very irregular.
Do you know the root cause, and if it's possible to solve this undesirable result?
Thanks!
Best Answer
-
In addition to Adam's excellent suggestions, I'd also recommend you verify your model has "reasonable" mass and inertia properties. If you have a lot of massless parts in your model, that can also lead to the kinds of numerical instabilities shown.
1
Answers
-
Hi Carlos,
A Motion is a constraint that you apply to a certain Joint, so the applied/plotted torque is the amount of torque required to force the system to complete the prescribed Motion.
Those spikes usually point to integrator error settings being too coarse (allowing too much error), your output step size being too small (not plotting enough data), or the Motion has to overcome imperfect kinematics to assert the desired movement on the Joint.
Hope this helps!
Adam Reid
1 -
In addition to Adam's excellent suggestions, I'd also recommend you verify your model has "reasonable" mass and inertia properties. If you have a lot of massless parts in your model, that can also lead to the kinds of numerical instabilities shown.
1 -
Thanks! T triyed to modify the Maximum step size, and integrator tolerance, and the plots has been drawed fine.
0 -
Carlos Fondevila said:
Thanks! T triyed to modify the Maximum step size, and integrator tolerance, and the plots has been drawed fine.
Hi Carlos,
That's great to hear. Please make sure you mark the reply as correct so other Users can quickly find the same answer as well.
Thanks,
Adam Reid
0
Altair Employee