> What we use (in our very limited code space = 1K) for SoftDMC is over-drive > detection, This is implemented with a 16 bit counter that is incremented by N > when Drive (PWM etc) is 100 % and decremented by M when Drive is less than > 100 > % each sample period. The counter is dead-ended at zero. If the counter ever > wraps, we do a shutdown on that axis. > This allows us to program the trip time in sample periods, yet not have false > triggers when drive is near 100% (a value of M much larger than N will reset > the count if drive is ever less then full) > With this simple system (and some reasonable amount of integral term in the > PID loop) you can pull an encoder connector and have the motor shut down in > 10 > mS or so
this sounds doable in HAL. It would be completely independent of motion planning, but a safety measure nonetheless. The duty cycle limiter would look at the DAC signal and effectively limit its duty cycle (time integral) to some value. I think you only need to define two parameters: the time-window, i.e. how much history is taken into account, and the duty cycle limit. If the duty cycle ever reaches the limit the component triggers E-stop. From looking at the motor specs I can probably figure out what DAC value corresponds to the rated continuous current. But if the servo amps are voltage mode, the DAC value will not determine current directly... So a question for Jon: are your PWM servo amps voltage or current mode ? i.e. when I set the DAC to a certain value, does that result in a constant motor voltage or in a constant motor current ? I'm going to test something like this when I get my motors and amps going. AW ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
