Siemens SINAMICS S120 Function Manual page 553

Mechanical oscillations are always dampened using the motor speed controller (P gain,
integrator). When dampening an axis, two counteracting adjustment principles are available.
1. In order to efficiently suppress disturbances, the speed controller is optimally set using a
high speed controller gain. However, by optimally setting the speed controller, oscillations
on the load side are frequently increased.
2. The speed controller gain must be reduced in order to optimally dampen the axis and to
reduce mechanical oscillations. Reducing the speed controller gain, means that
disturbance suppression is also reduced.
APC therefore offers several functions that facilitate efficient dampening and disturbance
suppression - and allows them to be optimally coordinated with one another. As a
consequence, using APC, you achieve two important closed-loop control related objectives:
● Mechanical oscillations are dampened
● Disturbances are efficiently suppressed with a high speed controller gain
Methods for the excitation of mechanical oscillations
Mechanical oscillation is excited using the following methods:
● Excitation by the command variable (setpoint motion of the axis)
With this method, mechanical oscillation is reduced by influencing the reference variable;
e.g. by changing the acceleration, by limiting the jerk or by using a setpoint filter. Influencing
the reference variable can be realized as follows:
– Changing the acceleration
– Limiting the jerk
– Using a setpoint filter
The disadvantage of this method is that processing or cycle times are extended. Further,
using a setpoint filter frequently results in a higher degree of inaccuracy when emulating
contours.
By using APC, you can reduce mechanical oscillation without having any of the
disadvantages listed above.
● Excitation by disturbing variables (e.g. as a result of periodic process forces)
With this method, mechanical oscillation is only influenced using an active closed-loop
control strategy.
Irrespective of the method used, any mechanical oscillation must be able to be measured using
the measuring system assigned to the particular axis. This is the reason that the following
methods are available when using APC.
1. APC is set just using motor variables (motor encoder, current).
2. APC is deployed together with a direct measuring system.
3. APC is deployed with an external acceleration sensor installed in the system.
Drive functions
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
9.14 Advanced Position Control (including Active Vibration Suppression)
Function modules
551