Dave Cole wrote: > Most of the robots I have worked with - like this 6 axis, rely on the > absolute encoders retaining their position as rehoming after a power > loss cannot be insured as many of them will crash if they do not know > where they are at on powerup. > > To "rehome" they they have to be manual jogged into a certain position, > shot pins installed in the joints, and then some sequence followed to > reset their position, usually via the pendant. > Well, that may be the case with the Fanuc control, but LinuxCNC may allow a more generalized homing sequence to be performed. The problem is when LinuxCNC starts, it generally clears the encoder counters to zero. This would be the best way to go, as then the machine could be restarted from a complete power down condition. But, I understand that homing a robot in a work cell environment can be much trickier than homing a simple Cartesian machine.
It may be possible to use the Fanuc ABS encoder logic to work with an encoder counter such as our PWM controller, by switching power to the encoders under computer control. When you start LinuxCNC, it can then wait until the ppmc driver is reading the encoder position before powering on the encoders, which will cause them to send their offset from index, which will in effect give absolute position. Even if this is not an exact position, it might get you close enough to do a safe homing sequence, joint by joint. (This will require a backup battery for the encoders.) (And, of course, you might just leave LinuxCNC running for long periods, to avoid having to home often.) Jon ------------------------------------------------------------------------------ October Webinars: Code for Performance Free Intel webinars can help you accelerate application performance. Explore tips for MPI, OpenMP, advanced profiling, and more. Get the most from the latest Intel processors and coprocessors. See abstracts and register > http://pubads.g.doubleclick.net/gampad/clk?id=60135991&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
