Estimation of nozzle axis and vector angle by infrared photoelectric measurement technology

An innovative estimation method for nozzle axis and vector angle from multi-camera stereo image sequences based on IR reflective markers is presented in this paper. It is assumed that four high-speed cameras fixed with IR LED board and IR filter have been calibrated previously. Firstly, the axis of nozzle is fitted based on a large amount of sample of IR markers coordinates, and the cone apex and the vector of cone axis are estimated. Secondly, a mass of axes of rotation of nozzle are estimated and used to fit the optimized axis of rotation by least square method, and then the common vertical line between nozzle axis and axis of rotation is calculated. The pivot point is obtained from the intersection point of nozzle axis and the common vertical line. Finally, the vector angle, angular velocity and acceleration of nozzle rotation are estimated by the relation between these markers coordinates and the time interval. The simulation is conducted using synthesized stereo image sequences based on the motion calibration instrument swaying through two axes and moving along the straight line. The measurement error of pivot point, vector angle, angular velocity and angular acceleration are respectively about 0.17 mm, 0.03°, 0.12(°)/s, and 0.4(°)/s², which verifies the validity of the presented method.