On 05/03/2021 02:34 PM, Gene Heskett wrote:
Friction will of coarse vary, but assume the amplitude of the jitter is constantly reset to zero by a passing edge from the encoder, but it times out in 2 millisecs. Leaving the pwmgen outputing a very low duration pulse in one direction or the other because the combo of friction and a d term combines to coast it to a friction stop, some 30 arc-seconds from where the gcode sent it. Now, because the jitter control has timed out, a counter watching each direction pulse is free to increment its count. That counter is added to the control signal in the direction to reduce the error. And its incremented by the pulse from that pwgmen's dir+ or dir- output. And in a few milliseconds the motor will move enough to output an encoder edge. That resets the counters, and the motor will not have enough to keep moving. But the pwmgen isn't satisfied yet so it keeps on outputting a 1% duty pulse on one or the other of its dir signals, Wash, rinse repeat, the motor is constantly being tickled enough by a 1 count move in the wanted direction until the pwmgen sees a match and stops tickling the motor.
Well, this is sort of what the I and D are supposed to accomplish. I creeps up the command to make it move toward the null point, but D backs it off as soon as it moves past an encoder edge.
Jon _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
