DE20111539U1 - Fiber optic sensor for the detection of displacements - Google Patents

Description

Fiber optic sensor for detecting displacements

With known technical solutions, component deformations, for example on rotor blades of wind turbines with strain gauges, are recorded and evaluated with fiber-optic Bragg gratings when electrical devices are not permitted. Another variant evaluates the intensity changes of a focused light beam resulting from deformation at the individual locations of a matrix-shaped optical receiver surface.

The invention presented represents a solution which again meets the requirements for exclusively optical measuring technology in the blade area, but generates evaluable intensity differences in the individual fibers by utilizing geometric displacements of two optical fiber bundles relative to each other.

Figure 1 provides an example of how the sensor works.

Light from a light source (1) is guided as a beam path (2) of almost uniform intensity via a cable-shaped bundle of optical fibers (3) to the location of the displacement to be detected and exits there at a ground end (4) of the bundle via the individual fiber cross-sections. A defined gap (5), which does not optically change the beam path significantly but enables a displacement of the end (4) relative to the end (6) via suitable guides (8) and a rotation axis (9), couples the end (4) to the end (6), which in turn feeds the light with an intensity distribution in the beam path (2) that may have changed during the passage through the gap via a fiber bundle (3) to an evaluation unit (7).

Depending on the position of the two ends (4) and (6) relative to each other, the cross-sections (10;l 1) of the individual fibers either lie congruently on top of each other, as shown in the upper image, or are offset relative to each other, as shown below. The two ends (4) and (6) are each firmly connected to different points on the component to be detected, so that a deformation of the component results in a displacement of the ends (4) and (6) relative to each other in direct proportion.

In the case of congruence, the light transmission occurs with almost no reduction in intensity; in the case of displacements, the intensity will decrease in proportion to the resulting smaller overlap area (12). The comparison of the intensities of several displaced overlap areas (12) allows, after evaluation, a statement to be made about the type and size of the displacement of the ends (4) and (6) relative to each other.

By appropriate dimensioning of the guides (8), the axis of rotation (9) and the fastening of the ends (4) and (6) to the component to be detected, for example a rotor blade of a wind turbine, the relationship between the change in intensity in the beam path and the displacement size can be optimized.

Claims (6)

1. Fiber optic sensor for detecting displacements, characterized in that: an optical waveguide fiber bundle is interrupted in a plane surface and the two ends of the bundle are each firmly connected to one side of the deformed component to be detected. 2. Fiber optic sensor for detecting displacements, characterized in that: the fiber bundle ends are arranged in such a way that the light transmission in the non-deformed state is almost undamped in all fibers, but when the fiber bundle ends are twisted or shifted in the cutting plane against each other, evaluable intensity differences occur in the individual optical fibers because the fiber cross-sections are no longer optimally aligned. 3. Fiber optic sensor for detecting displacements, characterized in that: the gap between the fiber bundle ends is designed by suitable filling so that neither scattering of the light nor additional attenuation occurs. 4. Fiber optic sensor for detecting displacements, characterized in that: the gap between the fiber bundle ends allows a relative movement of the two ground surfaces against each other in the gap plane by means of a suitable filling and contamination and light scattering are excluded. 5. Fiber optic sensor for detecting displacements, characterized in that: the guide or the pivot point for fixing the two fiber bundle ends is designed in such a way that there are clear relationships between the deformation of the component to be detected and the resulting intensity differences in the individual fibers and the intensity differences are sufficiently large for evaluation. 6. Fiber optic sensor for detecting displacements, characterized in that: the stop points of the sensor on the component to be detected are designed and dimensioned in such a way that inherent deformations of the sensor and restoring forces on the component are minimized and the existing deformations are sufficiently increased by suitable length ratios.