Explain the logic of collision detection function.
Solution
When machine simulation is done, a faceted representation of all the components in the model is created. This faceted representation is then stepped along a motion path according to the move and measurement commands in the DMIS program. At each step a check is made to see if the faceted models of all the defined collision pairs interfere with each other. If any do, then a collision is reported.
These parameters are important for a successful simulation and collision detection
The maximum length increment defines the largest step size during the simulation. If it is too large, the simulation can step over collisions. The "rule of thumb" that we use, is that the maximum length increment should be no larger than 50% of the smallest feature in the setup. This includes probes, fixtures and the part. For a typical CMM setup, it is the probe stylus that determines this number since they are generally 1-2 mm in diameter. This leads to a best maximum length increment of 0.5 mm. This parameter affects performance of simulation since a smaller value means that more steps need to be taken
The next parameter is faceting tolerance for collision detection. This defines how precise the faceted models represent the real geometry. The rule of thumb here is that this number should be smaller than 10% of the size of the smallest feature. Once again it is generally the probe stylus that determines this value. Typically this is 0.1 mm or less. This parameter has some impact on performance, but for modern computers with lots of memory running 64 bit operating systems we recommend a value of 0.05mm or smaller
Notes