K3: Compensations
4.5 Dynamic feedforward control (following error compensation)
Extended Functions
Function Manual, 03/2013, 6FC5397-1BP40-3BA1
281
Feedforward control factor for speed feedforward control (MD32610)
The additional velocity setpoint can be weighted using a factor:
MD32610 $MA_VELO_FFW_WEIGHT
Range of values: 0 ... 1
"0" means: no feedforward control. As standard, the factor has a value of 1 (≙ 100%).
The factor should remain set at 100%, as this value is the optimum setting for an optimally
set control loop for the axis/spindle as well as a precisely determined equivalent time
constant of the speed control loop.
Fine adjustment
The speed feedforward control for the particular axis/spindle can be optimized by making
slight changes (fine tuning) to the equivalent time constants of the speed control loop
(MD32810).
To make this check, the axis/spindle should be traversed at a constant velocity and in the
service display "Axis/spindle", the "System deviation" should be checked.
A small acceleration and a high feedrate should be chosen so that the values can be easily
read on the service display. This produces very long acceleration phases from which it is
easy to read off the control deviation.
Example:
MD32300 $MA_MAX_AX_ACCEL = 0.1 ; Maximum axis acceleration = 0.1 m/s
2
MD32000 $MA_MAX_AX_VELO = 20000.0 ; Maximum axis velocity
= 20000.0 mm/min
; Part program for setting the equivalent time constant
G1 F20000
FFWON
LOOP:
X1000
X0
GOTOB LOOP
M30
References
For detailed information about setting the equivalent time constants of the speed control loop
(MD32810) refer to:
● Function Manual, Basic Functions; Velocities, Setpoint / Actual Value Systems, Closed-
Loop Control (G2), Section: Optimization of the control
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