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5-14 Operation MN1904
5.6 Tuning an axis for current control
5.6.1 Selecting servo loop gains
All servo loop parameters default to zero, meaning that the demand output will be zero at
power up. Most servo amplifiers can be set to current (torque) control mode or velocity control
mode; check that the servo amplifier will operate in the correct mode. The procedure for
setting system gains differs slightly for each. To tune an axis for velocity control, go straight to
section 5.8. It is recommended that the system is initially tested and tuned with the motor shaft
disconnected from other machinery.
Note: The method explained in this section should allow you to gain good control of the
motor, but will not necessarily provide the optimum response without further
fine-tuning. Unavoidably, this requires a good understanding of the effect of the
gain terms.
1. In the Toolbox, click the Fine-tuning icon.
The Fine-tuning window is displayed at the
right of the screen. The main area of the
WorkBench v5 window displays the Capture
window. When tuning tests are performed, this
will display a graph representing the r esponse.
2. In the Fine-tuning window, click i n the KDERIV
box and enter a starting value of 1.
Click Apply and then turn the motor shaft by
hand. Repeat this process, slowly increasing
the value of KDERIV until you begin to feel
some resistance in the motor shaft. The exact
value of KDERIV is not critical at this stage.
3. Click in the KPROP box and enter a value that
is approximately one quarter of the value of
KDERIV. If the motor begins to vibrate,
decrease the value of KPROP or increase the
value of KDERIV until the vibration stops.
Small changes may be all that is necessary .