9 Replies Latest reply on Nov 21, 2007 10:25 AM by Ian Hogg

    Sampling/frame rate in motion

      Hi i have a an assembly in motion, and i am trying to increase theframe rate of the simulation. It has a default value of 32 in 0.93seconds for the duration of the simulation. When i try to changethis default value to a more respectable value of 10000 and thenpress simulate it reverts back to the default value of 32frames/sec. Any ideas why it does this? i have a powerful enoughcomputer to run at this desired rate. Thanks! Notay
        • Sampling/frame rate in motion
          Ian Hogg
          Hi Notay,

          Are you using Physical Simulation or COSMOSMotion? This sounds more like a physical simulation type of time definition (especially in SW2007). Both animator and physical simulation are not going to give you that level of resolution. The frame rate is really intended to control replay speed (to get a real time like movement).

          If you really want numerical accuracy to that level, then COSMOSMotion has more precise control over the steps in the simulation. Although, putting 9300 frames is going to bog down your system and increase solution time. What is your real goal here?

          Cheers,

          Ian
            • Sampling/frame rate in motion
              Hi Ian thanks for your reply. i am using motions intelligent motionbuilder, and for the assembly that you helped me with earlier, i amtrying to simulate the simple crank at 6750rpm (40500 degrees/sec),and have a graph of the magnitude of the forces at the conrod pivotpoints. However, due to the default value of 32 frames/sec, thesimulation only samples at 32 times in a sec and hence the samplingrate is too low. but for some reason it doesn't let me change thedefault value of 32 frames. any idea? i have uploaded my model.thanks. Notay
                • Sampling/frame rate in motion
                  Ian Hogg
                  The best way to define a simulation is based on the end time and the number of frames. When you have high rpm, you specify an end time for only a coupld of cycles (say 0.035556 seconds in your case) and then 200 or 300 frames should be more than adequate for clear resolution over that time.

                  To control this, right click on the top branch of the motion tree and select simulation settings. You can do it via the menu as well.

                  Cheers,

                  Ian
                    • Sampling/frame rate in motion
                      Thanks Ian it worked! do you know how accurate motion is? alsowouldn't the individual masses of the parts affect the reading? Iwent into 'component properties' but there is no option to changethe density or material type? am i looking at the correct menu toadjust the material properties? thanks! Notay
                        • Sampling/frame rate in motion
                          Ian Hogg
                          Divide your rpm by 60 to get to cycles per second. Invert the numbedr to get the time for 1 cycle and then I did the time for 4 cycles.

                          When dealing with cyclic motion, you need to be aware of the duration of one cycle to realistically set the end time, especially at high rpms.

                          Glad it worked out for you.

                          Cheers,

                          Ian
                            • Sampling/frame rate in motion
                              Thanks Ian, but how do you change the density of the parts in theassembly in motion? thanks! Notay
                                • Sampling/frame rate in motion
                                  Ian Hogg
                                  Hi Notay,

                                  There are 2 things you can do:
                                  1. Modify the material in SolidWorks and the density change will propogate automatically to COSMOSMotion

                                  2. Override the density in COSMOS motion (right click on the part and select properties. Select custom density or pick from simple built in list. This custom density will adjust not only the mass but the inertia of the part.

                                  As I said earlier, the motion builder is pretty old technology and has not been updated for quite some time and the feature tree is the best place to perform these tasks.

                                  cheers,

                                  Ian
                                    • Sampling/frame rate in motion
                                      Hi Ian, as the force magnitude graph is against time, is itpossible to get it against crank angle? so it would be force percrank angle? thanks! Notay
                                        • Sampling/frame rate in motion
                                          Ian Hogg
                                          Yes.
                                          In 2007, expand the plot in the tree so you can see the x and y axis. locate the joint/mate that connects the crankshaft to ground and drag it onto the x-axis of the plot. Select projection angle - z axis for the result to use and this will then become the x-axis of the graph.

                                          In 2008, you define the x-axis as time or a result in the property manager during creation.

                                          The online help should discuss how to use results for the x-axis.

                                          Hope this helps.

                                          Cheers,

                                          Ian