Experimental determination
As an alternative, you can experimentally define the ratio multi_gain_z/multi_gain_n by moving the axis at constant speed and by first determining the gain actually active in the position control loop on the basis of the following error and the axis speed.
Now the experimentally determined gain is compared with the kv factor (P-AXIS-00099) defined in the axis parameter list.
After that based on the current parameterized values of multi_gain_z and multi_gain_n the new multi_gain factor is calculated:
After change of the parameters these are to be checked again on the basis of the formula 1. The further optimization of the position control loop now is done exclusively on the basis of the parameter P-AXIS-00099 (getriebe[].kv).
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If the factor f is greater than 1, with the adaptation of the multi_gain factor the complete gain of the position control loop also increases. This can lead to an oscillation of the axis.To hold the complete gain of the position control loop constant, the position control gain P-AXIS-00099 should be set on the value P-AXIS-00099 / f . |
Example:
Following error s = 1.9 mm, axis speed v = 200 mm/min, P-AXIS-00099 = 400 * 1/s, multi_gain_z = multi_gain_n = 1.
Actual gain in the position control loop
k = v/s = 200 mm / (60 s * 1.9 mm)
k = 1.75
According to formula 1 the ratio of parameterized gain and really effective gain is:
Accordingly, multi_gain factor results in:
Therefore, possible entries in the axis parameter list would be:
P-AXIS-00129: getriebe[ ].multi_gain_z 2286
P-AXIS-00128: getriebe[ ].multi_gain_n 1000
Because with that entries the complete gain of the position control loop increases for the factor f, at the same time P-AXIS-0009 should be multiplicated with the factor 1/f. Because of that the complete gain of the control loop can be hold constant.
After checking of the determined parameters according to equation 1 the position control loop can be further adjusted by changing of P-AXIS-00099.