Technical data

Appendix
CPU 317T: Technology Functions
A-22 A5E00251798-03
A.3.2 Axis settings
A.3.2.1 Commissioning the position controllers of positioning axes
The position controller should be tuned in order to avoid overshoot of the
positioning axis during positioning. Procedure:
Requirements
• The axis is configured, except for the acceleration limits and the controller
settings.
• Commissioning guidelines for tuning without overshoot are provided.
• The cascaded control loops are commissioned, and the velocity control loop is
overshoot-free by means of feed-forward control.
Commissioning the P-controller with feed-forward control
1. Apply step velocity changes in the position controller (about 10 % of vmax).
Observe the current. It must not reach the limit. Remedy: Reduce the step
amplitude.
2. Change the K
v coefficient in the axis screen form for position control until the
actual velocity value no longer overshoots at the point of transition, and then
note this setting.
3. Set the following tuning values: K
v to 0.00 ... 1, enable velocity pre-control and
set the rating to 100%.
4. Apply the velocity step changes to the position controller once again;
see item 1.
5. Compare the setpoint and process values, based on the Trace recording:
The setpoint is found in Technology > Technology object > [Axis name] >
servodata.symmetricServoCommandVelocity
The actual value is found in Technology > Technology object > [Axis name]
> sensordata...[1].velocity.
6. Align the qualitative profile of both curve profiles by changing the velocity
controller time constants when you configure the axis
(see the Experts list:
TypeOfAxis.NumberOfDataSets.DataSet_x.DynamicData.velocityTimeConstan
t or position control > Expert mode > Dynamic controller data).
Note: Dead-time in the position control cycle or an offset in the display is
runtime-relevant and does not have to be compensated for.
7. Reset K
v to the previously determined value at which the transition process
no longer overshoots.