Natural Frequency Of The Hydraulic Drive - Siemens SINAMICS S120 System Manual

Configuration
3.3 Configuring the hydraulics
3.3.4

Natural frequency of the hydraulic drive

Controlled system gain
The possible controlled system gain is essentially determined by the natural frequency ω
the cylinder and its load, as well as the frequency limit of the servo solenoid valve ω
The cylinder and its load constitute a spring/mass damping system whose natural frequency
is calculated using the following formula:
Where:
Oil volumes in the cylinder pipes must also be taken into account.
The minimum natural frequency only occurs at a certain position around the middle and
increases as the end positions are approached.
After you have entered the HLA parameters, the HLA module automatically calculates the
natural frequency of the hydraulic drive, which is then taken into account in the controller.
The dynamic response of the servo solenoid valves depends on the amplitude of the valve
modulation. For valves that are used in controlled axes, the natural frequency is typically
determined for a modulation amplitude of "10% and a phase offset of -180°. The relevant
information is specified in the valve manufacturer's catalog.
For precontrolled servo solenoid valves, the dynamic response is determined by the
precontrol pressure p
Servo valves can reach corner frequencies of up to 1000 Hz, but are very sensitive to
pollution.
46
E = modulus of elasticity [N/m
A = piston surface area [m
A = ring surface area [m
2
R
α = surface area relationship A
h = stroke [m]
m = weight [kg]
in addition to the valve type:
pre
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2
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2
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/A
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Hydraulic Drive