Siemens SINUMERIK 840D sl Function Manual page 404

K3: Compensation
5.5 Dynamic feedforward control (following error compensation)
Commissioning
The following axis-specific parameters must be defined during commissioning for torque
feedforward control:
Equivalent time constant of the current control loop (MD32800)
The equivalent time constant of the current control loop must be determined accurately (e.g.
graphically from step response of the current control loop) and entered in the following
machine data in order to correctly set the torque feedforward control:
MD32800 $MA_EQUIV_CURRCTRL_TIME (equivalent time constant current control loop for
feedforward control)
Reference:
Function Manual Basic Functions; Velocities, Setpoint/Actual Value Systems, Closed-Loop
Control (G2), Chapter: "Optimizing the closed-loop control"
Total moment of inertia of axis (MD32650)
The total moment of inertia (moment of inertia of drive + load referred to the motor shaft) of
the axis must be determined and entered in the following machine data:
MD32650 $MA_AX_INERTIA (inertia for torque feedforward control)
Fine adjustment
The torque feedforward control for the particular axis/spindle can be optimized by making
slight changes (fine tuning) to the values in MD32800 and MD32650.
To make a check, the following error should be recorded via an analog setpoint output. In
addition to traversing at a constant velocity, the following error should be monitored
especially when the axis/spindle accelerates.
404
Function Manual, 09/2009, 6FC5397-1BP20-0BA0
Extended Functions