DMU Kinematics- Detect Clash (Catia)
Good morning.
I bumped into the following issue while trying to learn DMU Kinematics. Tried an easy example, a mechanism consisting from 2 square blocks, 50mm clearance between them, with one of them fixed and the other one a length driven prismatic joint, which I set to 100mm. I select the clash/contact sensors, so that the mechanism stops when they collide, not after 100mm. The weird thing that occurs is, the mechanism stops at 50.667 mm, after the contact already happened, and there is a collision of 0.667 mm. I believe it has to do with the amount of steps you set for the simulation, but I am not positive. Does anyone have any idea and/or possible solution? Thank you in advance
1 Answer
Yes, Catia unfortunatley is still a numerical program and has it's resolution in current normal scale about 1um and 1nm for small scale.
Add more steps to detect the clash. Use simulation with commands instead of simulation from DMU generic animation menu. In simulation with command you can set however many steps, and to fully pass to the resolution of Catia use a movement around the clash from 49,5 to 50.1 mm in about 2000 steps or more. Then the clash will set off at the first micron of clash.
Also detecting clashes can be done in more ways. The best i've found is a targeted clash analysys inserted by Insert-> clash and select contact+clash between those two parts. This clash will be in the tree and at simulation with command you can click on activate sensors and look at when the contact goes off and when clash is going off. If there is no contact but only clash, the the steps are too large, add more steps. When contact is achieved then you have enough steps to simultate every increment in movement achievable in CATIA
Also be aware of multiples. If you set a simulation in 10 steps from 0 to 100, one of those steps is exactly at 50 and should the contact go off which is good enough to identify the first moment of clash even if the next step will be at 60mm.
So to sum it up, check for contact instead of clash and adjust the steps untill you do get a contact before clash and that will be the first moment of clash.
