Condition monitoring of wind turbine blades and tower via an automated laser scanning system

Abstract

During its service life, a wind turbine has to withstand very challenging loads and severe environmental factors which can cause some deteriorations and cracks on structural components. Yearly periodic controls may not be sufficient to diagnose a fault at early stages. Therefore, wind turbines are very important systems which have to be monitored continuously. This work aims at developing an automated scanning system for IR (Infrared) laser vibrometers to conduct the tests and measurements, which are required for condition monitoring, in a more accurate and efficient manner. Unlike visible green or red lasers, IR laser is reflected by most surfaces (especially by blade material) with a very high intensity without needing a preparation or surface enhancement on the target. However, IR laser cannot be guided by refracting/reflecting the beam by lenses and mirrors used by conventional laser scanners. This work proposes a new methodology which is based on mounting the laser source on a motorized platform and then rotating the platform rather than guiding the laser beam by optical systems. The tests performed by using wind turbine models show that the proposed system is capable of guiding the laser to the desired measurement points with very high precision and efficiency. The results of the analyses also show that some important dynamic characteristics of the system such as Eigenfrequencies and mode shapes can be extracted very accurately.