6.4 Servo Gain Adjustments
6 -31
Feed-forward Functions
The responsiveness is increased by using one of the feed-forward functions. A feed-forward
function isnot so effective, however,if theposition loopgain isset toa highenough value.Adjust
the feed-forward set value of Pn109 as described below.
1.
Adjust the speed loop and position loop according to the method described on page 6 -30.
2.
Gradually increase the set value of Pn109 so that the positioning completion signal (/COIN)
will be output quickly.
Make sure that the positioning completion signal (/COIN) is not broken (i.e., turned on and
off repeatedly within a short period) and that speed overshooting does not result. These are
likely to occur if the feed-forward value is too high.
It is possible to add a primary delay filter (to be set in Pn10A) to the feed-forward function.
The primary delay filter may prevent the positioning completion signal from breaking and
the system speed from overshooting.
Bias Function
This function adds the bias set in Pn107 to the output (i.e., speed reference) of the error counter
if the number of accumulated pulses of the error counter exceeds the bias increment width set
in Pn108 and stops adding the bias if the output is within the bias increment width. As a result,
the number of accumulated pulses of the error counter decreases and the time required for posi-
tioning can be shortened.
If the bias set value of Pn107 is too large, the motor rotation will be unstable. The optimum bias
value varies with the load, gain, and biasincrement width. Make biasadjustments while observ-
ing the response. When not using this function, set Pn107 to 0.
Speed
Speed
reference
Bias
Pn107
Motor speed without bias function
Motor speed with bias function
Time
ON
OFF
OFF
Bias increment width
(Accumulated pulse setting)
Pn108
6.4.4 Gain Setting Reference Values
This section describes information on servo gain values as reference for making gain adjust-
ments.
Refer to the following for standardsfor gain adjustmentsaccording to the rigidity of themechan-
icalsystem.Refertothesevaluesanduse thepreviously mentionedmethodstomake gainadjust-
ments. These values are for reference only and do not mean that the mechanical system hasgood
response characteristics or is free from oscillation in the specified ranges.
Observe the response by monitoring the response waveform and make the optimum gain adjust-
ments. If the rigidity of the machinery is high, further gain increments exceeding the described
ranges are possible.
6
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