Hello,

I could obtain the simulation of my multibody with kinematic closed chain (CKC).

However, it seems that from a specific time (around 12s) in my model I believe that I have some numerical instabilities. Indeed, I could compare my simulation results with another mulbody software. I obtain the same simulation until 12s and after in MapleSim, it appears many perturbations as you can see on the figures belows.

So, I think that I tune the numerical solver. This numerical solver must solve DAEs equations since my model contains 4 kinematic closed loops.

If i read correctly the help menu, there are the following methods to solve the DAEs :

- use specific DAE numerical solver (3 differents solvers are used : ck45 method, RKF45 method and Rosenbrock method

- use reformulation equations techniques (Baumgarte, Projection) which can be associated (I believe) with a classic solver like (RK4).

For the moment, I have obtained my results with the rosenbrock solver with error absolute : 1.0*10^(-4) and eror relative :error absolute : 1.0*10^(-4) 

Do you have some ideas or advices so as to find a better method to solve my multibody systems with kinematic closed loops ? This method should  prevent the creation of numerical instabilities.

Thanks a lot for your help

Hello,

I would like to apply a torque directly on a revolute joint. I use a torque modulated by a signal source which is modified chirp signal.

I have done like in the figure below :

After having added this torque, my model no longer runs. The error message is only "simulation interrupted".

Do I correctly plug the torque ? Should I plug the torque element more in the flange a or b of the considered revolute joint ?

Do I tick "use support flange" ? Anyway, with or without, my model crashes.

Thanks a lot for your help.

Hello,

I have a little question about the display of the kinematic joints which are usually in red.

I didn't know why the kinematic joints have disappeared and I don't know how to display them again.

Do you have an idea about the button I have to use so as to display the kinematic joints.

Thanks for your help.

Hello,

I would like to modify the chirp signal source. In fact, I would like to put a function for the amplitude parameter instead of a constant.

I would like to obtain this kind of curve that is to say to increase progressively the amplitude.

Do you have some ideas how I can implement a function defined with several parts to define the amplitude parameter of the chirp signal ?

Thanks a lot for your help.

Hello,

I have a question concerning the initial conditions.

One interest of MapleSim is to enable to model a multibody systems with different kinds of coordinates : namely relative and absolute coordinates.

For a complex system, it seems to me that the determination of the initial position is not an easy task.

Consequently, I wonder if it is possible to determine the initial positions for the system in absolute coordinates thanks to the knowledge of the initials positions in relative coordinates.

In other words, I have already determined the initial positions of my system in relative coordinates but as I would like to simulate my system with absolute coordinates. I wonder if I can have a process to deduct the initial positions for the absolute coordinates for the initial positions in relative coordinates.

Thanks a lot for your ideas and help.