Screen Page "Bode Plot - Beckhoff AX2000 Setup Manual

BECKHOFF
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Screen page "Bode Plot"

This function is reserved for engineers and technicians who are experienced in control technology. We can offer
you appropriate training on request.
With the aid of the Bode plot you can analyze and optimize the speed control loop, taking into account the
mechanical characteristics of the machine.
The Bode plot draws the frequency response of the speed control loop. The system is stimulated by a
sinusoidal input variable. The output variable has the same frequency, but a different amplitude and some
degree of phase shift.
The relationship between the amplitude as a function of frequency (amplitude response) and the phase shift as
a function of frequency (phase response) provides a complete description of the dynamic characteristics of the
control loop.
Amplitude response
The amplitude response is the frequency-dependent amplitude characteristic (gain), shown on a logarithmic
scale.
Phase response
The phase response is the frequency-dependent phase-shift characteristic.
The following characteristic data are used for a qualitative description of the open loop frequency response:
Phase reserve (open loop)
The spacing between the phase characteristic curve and the -180° phase-shift line at the cut-off frequency, i.e.
the frequency at which the amplitude characteristic (gain) has fallen to 0 dB.
Amplitude reserve (open loop)
The spacing between the amplitude characteristic (gain) and the 0 dB level at a phase shift of -180°.
The characteristics of the closed control loop are evaluated with the aid of the Bode plot, using the expressions
"bandwidth" and "peaking":
Bandwidth (closed loop)
Bandwidth is the range of frequencies limited by the frequencies where the logarithmic amplitude characteristic
(gain) falls off by -3 dB.
Peaking (closed loop)
The expression "peaking" describes an overshoot of the closed control loop, corresponding to the maximum in
the amplitude response.
Starts recording the data.
Bode plot
This function should only be used by experts. As soon as the confirmation query has
been confirmed, the movement immediately starts automatically, using the internal
setpoint provision !
Stops recording data.
Stop
Saves the measurements that were recorded to a data medium in CSV format (can be evaluated by MS-Excel).
Save
Load Loads a CSV file and displays the curves in a diagram.
Update Loads and display the latest set of recorded data.
Cursor function When a set of data is displayed (from a file, or by starting a recording), a mouse click in the coordinate system
displays the measured values for the signals at the selected time. A click outside the coordinate system sets the
display values back to 0.
Call up the screen page "Bode Plot Parameter"
Parameter ...
This page is used to define the frequency range and the number of steps.
Setup Software
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Screen page "Bode Plot"
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