Condition monitoring of windmill rotor blades

The presented paper describes a condition monitoring system based on acoustic emission and acousto-ultrasonic techniques. Sensor near units for signal processing detect wave modes and contribute to reduce noise as much as possible. They can be connected as nodes within a network and may be integrated in the structure to be monitored. A compact signal processing structure has been realized containing components for analog preprocessing of acoustic signals, their digitization, algorithms for data reduction, and network communication. The core component is a digital signal processor (DSP), which performs the basic algorithms necessary for filtering, down-sampling, mode selection, and correlation of spectral components. As a first application, a monitoring system for impact detection and characterization of delaminations has been realized for a glass fiber composite rotor blade. Starting from the simulation of wave propagation, characteristic signal parameters were determined first. Impact locations and delaminations are detected by deriving these damage indicators from the detected guided wave signals. The final goal of this ongoing work consists in developing a structural health monitoring system for rotor blades of wind power plants based on elastic waves and vibrations.