how to set hmax in MotionSolve 2021

Question

Hi,

I am using a template to solve my problem. First there is a dummy transient which I would like to solve quickly. Then the real simulation starts and I need to reduce hmax.

I have different calls to "Simulate" command in the template and I want to set hmax. How?

GTT Adam · Accepted Answer

Hi @Luca Cavagna,

This can be solved using a Sensor in which the output step size or integration step size can be changed after a certain time value has been reached:

Typically, this approach is used when you are waiting for a system to reach a certain position/condition, when the setup isn't important. The output step size or integration step size can be set very coarsely in the event settings and then changed to a mew refined value after a TIME value has been reached or a certain distance measurement has been achieved.

As for Templates, the

https://help.altair.com/hwsolvers/ms/topics/solvers/ms/xml-format_31.htm

command in a Template can only change the following values:

However,

https://help.altair.com/hwsolvers/ms/topics/solvers/ms/xml-format_79.htm

the can be used to change the h_max and integrator tolerance to speed things up:

Therefore, you can use something like the following in a Template to achieve the coarse run and then the refined run:

Which can be shown to work in the LOG file.

First TRANSIENT:

Second TRANSIENT:

Hope this helps!

Adam Reid

Luca Cavagna · Accepted Answer

Hi Adam, thanks a lot for your detailed answer. Good job as always!

Before opening the question, I had tried with the sensor but could not get what I wanted. I triggered the sensor by checking TIME but then I got confused because from the MV panel I cannot get the hmax information according to:

hmax is not written in the xml file and despite I hacked the xml file I could not make it work. It seems like the MV panel sets "stepsize" and "dt":

Important to note: stepsize expires after one step. Maybe I went too quick but the hmax set in the xml file was not doing the job. In any case, your second proposal is exactly what I was looking for (my bad I should watch more carefully the documentation).

Thanks a lot for the answer!