Igor Chudov wrote: > I have the W axis working. > > > There is one problem, however: after the motion stops, ppmc.0.DAC.3 does not > go down to zero, and instead stays high, while the system is not moving. I > explain this by remaining under power to move "one more hair distance" > against friction, nothing is moving, and nothing is there to decrease the > output. > > This is normal, even the X and Y axes do this to some extent. > If it decreases a little bit, no disaster should happen, the knee will not > drop, the system is self braking etc. > > Instead, current is provided to the motor, the not enough to move the rotor, > but enough to heat it up too much. > > Yes, this is due to finite P gain, and a lot of weight and friction in the system. All that weight leaning on the ways makes them stiff. > So. How would I somehow configure EMC to stop providing any current to "W", > when not really moving it? > I don't think you can really do this for an "axis", ie. something moved by G-code. What you need to do is see if you can get the I term of the PID to eventually zero out the error. That is what it is supposed to do, and it may make a last "jerk" to bump it past the stiction to zero out the error. (I have to say I have not had much luck with the PID's I term, but that is what it is SUPPOSED to do.) There is also the BIAS term that can apply a constant offset to the DAC output to compensate for gravity. But, if the motor is already running hot, then that is not what you want to do.
What you may have here is an impedance mismatch, ie. the motor really needs a much greater gear reduction to keep the steady-state force needed to resist gravity well below the continuous torque rating of the motor. Alternatively, maybe the air assist pressure needs adjustment to lighten the load on the motor. Jon ------------------------------------------------------------------------------ Free Software Download: Index, Search & Analyze Logs and other IT data in Real-Time with Splunk. Collect, index and harness all the fast moving IT data generated by your applications, servers and devices whether physical, virtual or in the cloud. Deliver compliance at lower cost and gain new business insights. http://p.sf.net/sfu/splunk-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
