Dynamic Feedforward Control (Following Error Compensation); General Properties - Siemens SINUMERIK 840D sl Function Manual

5.5

Dynamic feedforward control (following error compensation)

5.5
5.5.1

General properties

Axial following error
The remaining system deviation of the position controller when traversing a machining axis is
known as axial following error. Expressed in another way, the axial following error is the
difference between the setpoint position and the actual position of the machine axis.
Effects
Particularly during acceleration in contour curvatures, e.g. circles and corners, this following
error leads to undesirable, velocity-dependent contour violations.
Compensation
The axial following error can be reduced almost to zero with the help of the "dynamic
feedforward control". The function is therefore also called "following error compensation".
Methods
There are two "dynamic feedforward control" methods:
● Speed feedforward control(velocity dependent)
● Torque feedforward control(acceleration dependent)
Activation
The feedforward control method is selected and activated using the machine data:
MD32620 $MA_FFW_MODE (feedforward control mode)
Value
0
1
2
3
4
Extended Functions
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
Note
The torque feedforward control is an option that must be licensed and is only available for
SINUMERIK 840D sl. The function is not available for SINUMERIK 828D.
Significance
No feedforward control
Speed feedforward control with PT1 balancing
Torque feedforward control with PT1 balancing
Speed feedforward control with Tt balancing (standard setting for 840D sl / 840Di sl)
Torque feedforward control with Tt balancing
5.5 Dynamic feedforward control (following error compensation)
K3: Compensation
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