Torque Feedforward Control - Siemens SINUMERIK 840D sl Function Manual

Machine data MD10082 determines the lead time for the output of speed setpoints. The
larger the value entered, the sooner the drive transfers the speed setpoints.
The following meanings apply:
● 0 %: Setpoints are transferred at the beginning of the next position control cycle
● 50 %: Setpoints are already transferred after execution of half of the position control cycle
A reasonable lead time can only be determined by measuring the maximum position control
calculating time. Machine data MD10083 suggests a value measured by the control. As this
is a net value, a security reduction of e.g. 5 % must be undertaken by the user.
Note
If lead times that are input are too high, this can cause output of drive alarm 300506.
The input value is rounded to the next lower speed controller pulse rate in the drive. If the
speed controller pulse rates of the drives are different, changing the value will not
necessarily lead to the same degree of controller improvement for all configured drives.
5.5.4

Torque feedforward control

In the case of torque feedforward control, an additional current setpoint proportional to the
torque is applied directly to the current controller input. This value is formed using the
acceleration and moment of inertia.
The equivalent time constant of the current control loop must be determined accurately and
input as machine data to adjust the torque type of feedforward control correctly, refer to:
MD32800 $MA_EQUIV_CURRCTRL_TIME
Because of the direct current setpoint injection, torque feedforward control is only possible
on digital drives (SIMODRIVE 611D).
Figure 5-18
Extended Functions
Function Manual, 01/2008, 6FC5397-1BP10-3BA0
5.5 Dynamic feedforward control (following error compensation)
Torque feedforward control
Compensations (K3)
391