Shabbir Hussain wrote: > Dear All, > > I have set up a lathe machine with analog AC servos and Mesa 7i43 and 7i33. > The following error is 0.017 mm at start (acceleration) and then reduced to > 0.008 mm at 6000 mm/min. Everything is just fine except: > > When the machine is homed the axis moves towards home switch, touches it and > then moves away with latch velocity. As the index pulse is encoutered the > axis stops with a "DHUCKK" sound. The sound only comes in homing when the > axis are away from home switch ( say 150 mm). The machine runs fine rest of > the moves. I can jog it at 7200 mm/min, stop it then move it in reverse > direction without any sound. The setting for HOME_SEARCH_VEL is 20 mm/sec and > HOME_LATCH_VEL is set at -1.0 mm/sec. The hal scope trace of the f-error > signal shows an error of 0.06 mm and pid output saturated for very small time. > > When the index signal is seen during the final homing stage, it resets the position count to zero. The encoder counter and/or PID should ignore the velocity on the following servo cycle, as it is completely unknown. One trick is to use the velocity from the last servo cycle. It sounds like the velocity is being computed from the difference between the last know position and the new zero value, which will likely be a huge number and cause a large spike output from the PID.
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