8 Replies Latest reply on Jun 25, 2013 7:17 AM by Ronan Carrroll

    Motion Analysis Question

    Ronan Carrroll

      I am trying to run a simple motion analysis. Have a rotating mass and 50:1 reduction ratio. Mass does one revolution stop to stop in 1 second

      So 0 to 90 constant acceleration.

      90 to 270 deg constant speed.

      270 to 360 deg constant deceleration to stop.

      Want to see the required motor torque. Attached is basic assembly with virtual components inside.

      Cant get it to run. get message saying motor speeds a very high.

        • Re: Motion Analysis Question
          Jared Conway

          hi ronan, i think you want to be in the motion forum.

           

          i pulled down your assembly, there was no motion analysis setup. which solver were you using? animation? basic motion or motion analysis?

           

          i applied a motor that rotated the big part 360deg in 1s with a motor, everything worked fine. one thing i always tell my customers in our mentoring service is to make sure that your motor ramps up and ramps down which is more realistic than saying that it starts spinning at a certain velocity right from the beginning.

           

          for required torque, you have to be careful with gear mates. i would make sure to double check the solution with an example that uses gear teeth and contact.

            • Re: Motion Analysis Question
              Ronan Carrroll

              Hi Jared

              Thank you for replying. I am using motion analysis, so I can have a plot of motor torque. Realise it is only a very basic model.  Have re-attached the the file with the motion study.

              If you can get it to work that would be great.  Please post the model you have used or some screen shots.

                • Re: Motion Analysis Question
                  Jared Conway

                  what speed do you want the small cylinder to spin at?

                   

                  if you take your model and slow it down, it works great. at the speed you have, it fails on my end.

                   

                  is that really the speed it rotates at? have you followed any of the suggestions in the warning/error?

                    • Re: Motion Analysis Question
                      Ronan Carrroll

                      That is the actual speed.It's the large part that does one rotation stop to stop in 1 second. The ratio of the diameters represent a 50:1 gearbox. I was originally trying to do a quick model so I could play with inertias, gear rations and rotation times quickly. I can solve it by hand, that is how I got the actual motor speed to begin with. It was worth a try.

                        • Re: Motion Analysis Question
                          Jared Conway

                          just to double check your calcs, apply your motor to the big part to get a 360 deg rotation in 1s. then output the result from the small motor. i don't think i got the 22600deg/s that you had input

                            • Re: Motion Analysis Question
                              Ronan Carrroll

                              Ok so the big part does 360 deg per second there fore the motor is doing 50X360deg/s =18000deg/s  (3000rpm)

                              Now that is just an average rotation speed. As the motor has to ramp up to speed and ramp down again (both is 0.25 sec eac) with a constant speed (for 0.5 sec ) the peak constant speed value works out at 3750rpm from my calculatiions.

                              So 18000 X 3750/3000=22500deg/s.

                                I think simulation needs a bit of added funtionality here. The ability to add a motor with gearbox.

                                • Re: Motion Analysis Question
                                  Jared Conway

                                  Hi Ronan, did you try any of the suggestions in the solver failure dialog that pop up? I just increased the number of frames per second to 200 and it solves without issue. Because of the high speed, I suspect that 25fps wasn't enough. This was done in 2013 sp3.0.

                                    • Re: Motion Analysis Question
                                      Ronan Carrroll

                                      Hi Jared

                                      I had only tried reducing the accuracy in the Motion study Properties. Got it working.

                                      I hadn't realised thar the fps was affecting the accuracy calculation, thought it was just to do with the amination display.

                                      Other was I deg/s speed was to high typo. I had 225000 should be 22500. Once I got it running. I change the solver to the WSTIFF.It will actually run a 50fps using this solver This gave accurate motor torque. Animation shows a motor torque of ) 0.64Nm. I had calculated 0.67Nm. Your help is much appreciated.