On 3/25/2016 5:29 PM, Nicklas Karlsson wrote: >>>>> As someone mentioned before a the an axis/joint may/will run away >>>>> in case of an encoder failure. >>>>> >>>>> It would be possible to detect an encoder failure by comparing >>>>> output signal with encoder signal. A velocity signal may be >>>>> integrated and do not allow to wander to much or an encoder error >>>>> will be detected. A torque signal would be worse. >>>> An encoder that fails into runaway (motion erroneously detected >>>> when none is occurring) or that fails into stop (no motion detected >>>> when motion *is* occurring) will both result in a following error, >>>> precisely for the reason you say above: linuxcnc compares the >>>> commanded position with the feedback position from the encoder. >>>> >>>> >>>> -- Sebastian Kuzminsky >>> No if no motion is detected and there is a small error linuxcnc will >>> output a signal to correct it and machine start to move. Since no >>> feedback is detected integrator will turn up speed and machine run >>> away. >> Are you describing a scenario where the signals from the encoder are not >> getting to LinuxCNC? So it always looks to linuxcnc like there is no >> motion happening, no matter what's actually happening in the motion >> hardware? >> >> In that situation, if LinuxCNC is "at rest" and not commanding any >> motion, it's true that any small PID output will be applied forever, >> with no change in the feedback, and the motor will run away. >> >> And you're suggesting to look at the PID output, and if it's commanding >> motion but the encoder is reporting no motion, then trigger some sort of >> "hardware malfunction" estop? >> >> That sounds like it would work. >> >> >> -- >> Sebastian Kuzminsky > Yes I am suggesting comparing the PID output and encoder input. > > > Nicklas Karlsson >
I think that could only be a problem with torque mode servo drives. If you are using velocity drives the most that can happen is that the drives drift away. But even in those conditions I always seem to get a following error that drops the enable to the drives and shows a fault on the screen. Dave ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785351&iu=/4140 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
