Abstract: A method based on stereo vision is proposed to accurately measure the torsion of helicopter rotor blades and to simplify the operational process. First, three-dimensional coordinates of the circular markers in the camera coordinate are obtained by using the binocular stereo vision technique. Second, the rotor coordinate is established by the threedimensional coordinates of the markers which are measured when the blades are horizontally straight during low-speed rotation. Finally, the torsion of blades is calculated by the threedimensional coordinates of the markers which are obtained during low-speed rotation and high-speed rotation on the blades in the rotor coordinate. The method proposed in this paper is proved to be effective and accurate by a number of experiments and data analysis on measurement of the torsion of rigid blades. It also shows advantages of non-contact detection, dynamic measurement and easy operation.

Key words: binocular stereo vision, circular marker, torsion, rotor coordinate system