Measurement of deformation of a rudder

The measurement of the deformation of a rudder as it moves through water is particularly complicated using conventional sensors for two main reasons. Firstly because of the obvious need to insulate the submerged electrical system completely, and secondly the difficulty of positioning awkward sensors on the external surface of the rudder.

The simplicity of FBG sensors allows these problems to be easily overcome. Without electrical signals the problem of insulation disappears completely, whilst the simple physical form of the sensors allows them to be attached to the rudder with great versatility; in this particular case wed used adhesive tape, as shown in Fig. 1 and Fig. 2.

Fig. 1

 

 

Fig. 2

 

The axis of the rudder is connected to a system able to measure all of the forces and the moments felt by the rudder during its movement. With these dual measurements we can correlate the deformation felt by the FBG sensors and the forces acting on the rudder.

The measurements were taken for different angles and at varying speeds, and the sensors were positioned at various points on the rudder. Fig 3 & 4 show one such configuration.

Fig. 3

Fig. 4

 

The animation visualizes the result achieved by positioning four sensors parallel to the direction of the flow.

The intensities of colors on the rudder surface show the varying deformations at different levels in the water.

Click to see the animation

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