# How to set initial velocity to Simscape (with wheels with input torque)?

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Clemente Juan Oliver on 5 Dec 2018
Commented: Christoph Hahn on 5 Jul 2019
Hello,
I am trying to simulate a pod for the Hyperloop 4 competition, and I already have the main parts finished, nevertheless, the goal is to study the vibrational behavior of the structure applying some gaps between rails. At the moment, the pod accelerates with the provided imput. The problem arises when a small change is made in the Simulink and it has to compile and simulate again (2+ hours) to see the new results. This is due to the fact that the pod has to be at max speed when facing the gaps, so an initial rail of 500 m has been set so that the pod accelerates, which makes the simulation too long and heavy to process (800+ m in total). My question is, is there any other way to provide the wheels with some initial angular velocity so that the pod achieves the desired velocity and MATLAB only had to simulate few seconds?
I attach some screenshots of the SimScape and simulation. Please ask for any additional info you may need.
Thanks for considering my request,
Clemente.

Christoph Hahn on 9 Jan 2019
Hi Clemente,
of course you can set an initial angular veloctiy. You seem to be using Revolute joints. By adding Properties -> Motion -> Provided by Input (see figure), you get an additional input port called 'q' where you can add a signal (see second figure). Make sure you specify a suitable unit.
Hope that helps!
Best, Christoph

sergio castellani on 1 Jul 2019
hello
by doing this u specify indeed a motion --> a position. Which is not what is was asked in the post. We are asking how do you specify an initial velocity, which can change after due to external forces. So, i would at least revert the way in which the joint is controlled using " Motion, automatically computed" and then finding a way to insert an initial velocity, which is sitll not clear by your answer.
Sergio
Christoph Hahn on 5 Jul 2019
Hi Sergio,
Would you mind asking a new question where you explain your specific problem and ideally share a model to illustrate.
Please send the URL of the new question to racinglounge@mathworks.com. We'll be happy to help.
Thanks and Best,
Christoph