Beckhoff AX5000 Series Function Manual

Velocity - Controller Structure
Function description86
Version: 1.5
20.1.1 Setpoint value calculation
Depending on the set operation mode (S-0-0032) the control value (P-0-0558) for the position controller is
provided as velocity command value or directly from the interface (S-0-0036). The pre-control value
(S-0-0037) is then added.
20.1.2 Setpoint limiting
Setpoint limiting (see block diagram on page 1) affects the velocity command value. The limitations are
bipolar (S-0-0091).
20.1.3 Velocity controller
Note
The „Velocity controller“ section is currently still in preparation and will be released as soon
as possible.
20.1.4 Determining the actual velocity value (differentiation)
In the AX5000 a speed signal is calculated from the position signal of the motor feedback (through
mathematical differentiation). This signal quickly responds to changes, but it contains noise and can surge in
the presence of mechanical resonances. Mapping takes place in parameter P-0-0519.
20.1.5 Determining the actual velocity value (Velocity Observer)
Note
Reference values of the Velocity Observer:
S-0-0040; S-0-0109; S-0-0111; P-0-0070; P-0-0071; P-0-0073; P-0-0074; P-0-0126;
P-0-0127 P-0-0128
An Observer is a system for representing parameters that are difficult to measure, based on a model and known input and measured
variables.
For frequencies above around 300 Hz the noise associated with the velocity signal calculated from the feedback becomes problematic.
The Velocity Observer of the AX5000 is used to solve this problem. It estimates the acceleration from the measured current and from
this the speed signal (through numerical integration). This speed signal is smoother and less susceptible to mechanical resonances.
When the Velocity Observer is used, up to the set bandwidth the velocity controller takes into account the speed signal calculated from
the feedback, at higher frequencies it takes into account the speed signal estimated from the torque-forming current. The purpose of
the Velocity Observer is to provide the velocity controller with a speed signal without resonance-induced oscillations over a wide fre-
quency range. It acts similar to a low-pass filter, but without the disadvantage of a phase shift.
The result of the actual velocity value determination with the aid of the Velocity Observer is mapped in parameter S-0-0040.
Note
Velocity Observer settings and internal filters!
Further information about Velocity Observer settings and a detailed description of the pro-
cedure can be found below in this section.
Further information about the filter types mentioned above can be found in chapter: „Con-
trol quality – internal filters [}36]“ in the function manual for the AX5000 servo drive.

Beckhoff AX5000 Series Specifications

General

Control	EtherCAT
Protection Class	IP20
Feedback	Resolver, EnDat, Hiperface, SSI
Safety	STO (Safe Torque Off)
Relative Humidity	5% to 95%, non-condensing
Certifications	CE, UL, cUL
Operating Temperature	0…+45 °C