Siemens SINAMICS S120, Function Manual

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Function modules
8.14 Advanced Position Control (including Active Vibration Suppression)
Drive functions
592
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
8.14 Advanced Position Control (including Active Vibration Suppression)
8.14.1 Introduction
The "Advanced Position Control" (APC) function module provides closed-loop control related
functions to actively dampen/influence mechanical oscillations. APC is not a filter. The
function actively responds to measured oscillations using an appropriate manipulated
variable. The motor moves to compensate for the oscillation. If the oscillation frequency
changes as a result of axis load or mechanical changes, then APC also responds to the
modified frequency. The APC function module is calculated in the speed control loop.
Oscillations can be influenced using the motor speed controller (P gain, integrator). There
are 2 strategies: With a high gain, the controller is set to optimally respond to disturbances.
Frequently, load side oscillations are increased as a result. For a setting that is optimized for
damping, although the oscillation is reduced, the control gain must be reduced. This means
that the ability to suppress disturbances is reduced. The APC function module provides
additional functions, which resolve this conflict. Using APC, it is possible to
dampen/attenuate oscillation, and at the same suppress disturbances with a high speed
control gain.
Mechanical oscillations can be excited in 2 ways:
● Excitation by the command variable (setpoint motion of the axis)
In this case, oscillation can be reduced by influencing the command variable (setpoint),
e.g. by changing the acceleration, limiting jerk or by using a setpoint filter. This function
has the disadvantage that generally machining or cycle times are increased. Further,
using a setpoint filter frequently results in a higher degree of inaccuracy when emulating
contours.
APC can reduce oscillation without having this disadvantage.
● Excitation by disturbing variables (e.g. as a result of periodic process forces)
In this particular case, oscillation can only be influenced using active closed-loop control.
In both cases, in order to successfully and effectively use APC, the oscillation must be
able to be measured using a measuring system/sensor assigned to the axis. The function
module offers different versions to achieve this. APC can only be adjusted using motor
variables (motor encoder, current). A direct measuring system if available can be used for
the APC. Further, it is possible to integrate an external acceleration sensor into the
system and use this for the APC.