Method for calibrating nominal frequencies
The invention relates to a method by means of which a system that is capable of oscillating can be monitored. The method comprises detection of natural oscillation modes of the system that can oscillate as a function of at least one operating parameter and/or as a function of at least one environmental parameter of the system that is capable of oscillating, creation of a frequency distribution of the detected natural oscillating modes, division of the natural oscillating modes into frequency classes and, in at least one frequency class, determination of a mode profile over the operating parameter and/or over the environmental parameter.
1. A method for determining a mode profile, wherein the method comprises:
detection of natural oscillation modes of the system capable of oscillating as a function of the at least one operating parameter and/or as a function of the at least one environmental parameter of the system capable of oscillating in at least one operating range;
creation of a frequency distribution of the detected natural oscillation modes as a function of a mode frequency and of the at least one operating parameter and/or of the at least one environmental parameter in the operating range;
depending on the created frequency distribution, division of the natural oscillation modes into frequency classes, wherein the division of the natural oscillation modes into frequency classes is carried out by determining a peak value of the frequency distribution of natural modes which exceeds a predetermined threshold and which has a continuity over the entire operating range; and
in at least one frequency class, determination of the mode profile over the operating parameter and/or over the environmental parameter.
2. The method according to claim 1 , wherein the at least one operating parameter of the system capable of oscillating is selected from the group which consists of: a rotor speed, a setting angle of a rotor blade, an angle of attack, a pitch angle of a rotor blade, a yaw-angle of a rotor nacelle, a generator speed, a generator power, and any combination thereof.
3. The method according to claim 1 , wherein the at least one environmental parameter of the system capable of oscillating is selected from the group which consists of: the ambient temperature, an ice coating on a rotor blade, impinging of foreign material on a rotor blade, air humidity, a wind pressure, a wind direction, a wind speed, a surface loading on a rotor blade, an angle of attack, a speed of attack, a pressure difference, a rotor blade temperature, a rotor blade rigidity, a rotor blade mass distribution, and any combination thereof.
4. The method according to claim 1 , wherein the detection of natural oscillation modes of the system capable of oscillating comprises a detection of at least one of the following parameters: one or more natural frequencies, mode forms, mode angles and damping.
5. The method according to claim 1 , further comprising a fixing of nominal modes to be monitored in at least one frequency class from the determined mode profile over the operating parameter and/or over the environmental parameter.
6. The method according to claim 1 , wherein the creation of a frequency distribution comprises the creation of a histogram.
7. The method according to claim 6 , wherein the histogram is divided into different frequency classes.
8. The method according to claim 1 , wherein the system capable of oscillating is a rotor blade of a wind turbine.
9. A hardware module, comprising a computer program which is configured to carry out the method according to claim 1 .