Fig. 6.

Plots of torsional position and speed over time for an annulus mounted on a stepper motor. (a) and (c) correspond to the video where the camera is directly in front of the annulus, while (b) and (d) correspond to the video where the camera has been placed such that it is imaging the annulus from 43° off-centre. In all plots, the points are the estimates from our method, and the circles are the estimates obtained by rotating and visually matching the images. For the position plots, the lines represent the estimates from cross-correlation, and in the angular speed plots, the lines represent the gyroscope data. The damped oscillations of the stepper motor just after each movement are also present in the torsion plots. The inherent granularity of the cross-correlation estimates resulting from the angular resolution of 3 pixels/degree is visible as an oscillation artefact with an amplitude of a third of a degree.