Tham khảo tài liệu 'active visual inference of surface shape - roberto cipolla part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 142 Chap. 5 Orientation and Time to Contact from etc. a d Figure Using image divergence for collision avoidance. A CCD camera mounted on a robot manipulator a fixates on the lens of a pair of glasses worn by a mannequin b . The contour is localised by a B-spline snake which expands out from a point in the centre of the image and deforms to the shape of a high contrast closed contour the rim of the lens . The robot then executes a deliberate motion towards the target. The image undergoes an isotropic expansion divergence c which can be estimated by tracking the closed loop snake and monitoring the rate of change of the area of the image contour. This determines the time to contact - a measure of the distance to the target in units of time. This is used to guide the manipulator safely to the target so that it stops before collision d . . Implementation and experimental results 143 Figure Using image divergence to estimate time to contact. Four samples of a video sequence taken from a moving observer approaching a stationary car at a uniform velocity approximately Im per time unit . A B-spline snake automatically tracks the area of the rear windscreen figure . The image divergence is used to estimate the time to contact figure . The next image in the sequence corresponds to collision 144 Chap. 5 Orientation and Time to Contact from etc. Time frame number Figure Apparent area of windscreen for approaching observer. Time to contact frames 7 3 4 5 6 7 Time frame number Figure Estimated time to contact for approaching .
