Optical flow balancing guidance laws used to avoidobstacles are investigated. First, a 2-D analysis is presentedwhere the rate of the Line Of Sight (LOS) from the vehicle toeach obstacle on the right and left hand sides of the camera'sboresight is measured and a guidance law nulls the LOS rates'difference. Simulation results are obtained initially using noFOV limitations, then applying Field Of View (FOV) restrictionswith additional obstacles in the scene. Equalizing the LOS rateswith no FOV limitations, actually results in a collision, exceptif the vehicle is initially on the orthogonal bisector of the lineconnecting two obstacles. In this instance, the trajectory is notstable and a collision with an obstacle might ensue. However,multiple obstacles and FOV limitations in conjunction withsimple reactive guidance commands is conducive to obstacleavoidance. Evidence is presented that leads to the conclusionthat balancing the optic flows seems to cause the UAV toavoid the obstacles. The special symmetric case is analyzed.This trajectory is unstable to perturbations, but obstacles areavoided. Finally, looming is then quantified as an increase inthe included angle between the LOS's to two features. Thelooming of an object in the camera's FOV is measured andis used with LOS rate balancing for synthesizing a collisionavoidance guidance law.
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