Optoelectronic strain measurement for flywheels

Uncertainty Analysis of an Optoelectronic Strain Measurement System for Flywheel Rotors

“…This section explains the principle operation of an optoelectronic strain measurement (OESM) method for flywheel rotors as shown in Figure 1 [10]. A pattern of spiral sections is applied to the top surface of the rotor.…”

“…The local deformation u at each sensor position can then be determined by the difference of the reference value and the instantaneous measurement. Systematic influences of the flywheel rotor such as in-plane and out-of-plane vibrations can be corrected by using multiple sensors at different angular sensor positions and utilizing calibration patterns on the rotor surface [10]. An expansion to include a more detailed rotor behavior is possible but would exceed the scope of this paper [13].…”

“…where N lobe is the number of lobes in the pattern, u min = 1.2 µm is the minimum deformation we want to measure (1% of du at the interface between the middle and outer CFRP ring) and r = 210 mm is the radial position of the interface between the middle and outer CFRP ring [10].…”

“…The shift in ∆ thresh caused by this potential change in h is substantial but constant, and can be reduced by calibration. Calibration is possible by additional measurement of the flywheel's radial and axial position and by including reference marks of constant width on the OESM pattern [10]. The inductive distance sensors we use for axial position measurements show a measurement noise of 3.4 µm when averaging over a full flywheel revolution at the maximum speed of 500 Hz.…”

“…Optoelectronic strain measurement (OESM) relies on a special printed pattern on the flywheel which is read remotely by an optoelectronic system [10]. There are no electronics required on the flywheel itself but only on the stationary housing.…”