Abstract
Abstract. Health monitoring by conventional sensors like accelerometers or strain gauges becomes challenging for large rotating structures due to the issues with feasibility, sensing and data transmission. In addition, acceleration measurements have low capability of presenting very small frequencies, which happen very often for large structures (for instance, frequencies between 0.2 and 0.5 Hz in horizontal-axis wind turbines). By contrast, displacement measurement using stereo vision is rapid, non-contacting and distributed over the structure. The sensors are cheaper and more easily applied to many places on the object to be measured. Horizontal-axis wind turbines are one of the most important large rotating structures and need to be measured and monitored in time to prevent damage and failure, and the blade tip position is one of the key parameters to measure in order to prevent the blade hitting the turbine tower. This paper presents a clearly described and easily applicable procedure for measuring the displacement on the components of a rotating horizontal-axis wind turbine with stereophotogrammetry. Paper markers have been applied on the rotor and tower of a scaled-down horizontal-axis wind turbine model in the workshop and the displacement measurement method has been demonstrated by measuring displacement during operation. The method is mainly developed in two parts: (1) camera calibration and (2) tracking algorithm. We introduce an efficient camera calibration method for measurement in large fields of view, which has always been a challenge. This method is easy and practical and offers better accuracy compared with 2-D traditional camera calibration. The tracking algorithm also works successfully and is able to track the points during rotation within the measurement time. Finally, the accuracy analysis has been conducted and has shown better accuracy of the new calibration method compared with 2-D traditional camera calibration.
Highlights
Regarding the increasing industrial advances and the world’s population growth, fossil fuel sources will not meet the human need for energy in the near future
A clearly described and applicable stereophotogrammetry approach is introduced to measure the displacement of a rotating horizontal-axis wind turbine
The camera calibration and marker tracking algorithm are studied in this work
Summary
Regarding the increasing industrial advances and the world’s population growth, fossil fuel sources will not meet the human need for energy in the near future. Growth of wind turbine technology has led to important concerns about the reliability of energy production and wind turbine efficiency, and reliable turbine operation requires proper experimental tools and high-quality testing methods to monitor the turbine behavior Traditional contact transducers such as strain gauges and accelerometers have been used for vibration analysis, health monitoring, damage detection and structural displacement of wind turbines (Weijtjens et al, 2017; Yang et al, 2014; Osgood et al, 2010; Lorenzo et al, 2016; and Manzato et al, 2014) and other large structures like bridges (Hoffmann, 1989; Fukuda et al, 2013; Park et al, 2005; Ye et al, 2012; Xia et al, 2014, and Siriwardane, 2015), but they have difficulties measuring on a large scale; the installation process, which often includes wiring, is costly and time consuming. A traditional way of calibration uses a calibration object with known and precise coordinates to calibrate the camera This method is accurate and efficient, but it is unpractical for large field-of-view applications because of the calibration object size. We compared the results of the updated 3-D calibration method with the traditional calibration that is conducted with a large grid in the background and the comparison shows better accuracy of the new 3-D calibration procedure
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
