Using image sensor and tracking filter time-to-go to avoid mid-air collisions

A collision avoidance system for deciding whether an autonomous avoidance manoeuvre should be performed in order to avoid a mid-air collision between a host aerial vehicle equipped with the system and an intruding aerial vehicle, said system comprising:

• at least one electro optical sensor arranged to capture consecutive images of said intruding vehicle, the vehicle of which manifests itself as a target point in said images,
• an image processor arranged to estimate at least the azimuth and elevation angle from the host vehicle to the intruding vehicle based on the 2D position of the target point in said images, and a first time-to-collision estimate of the time to collision between the host vehicle and the intruding vehicle based on scale change in the target point between at least two of said consecutive images,
• a tracking filter arranged to estimate a second time-to-collision estimate of the time to collision between the host vehicle and the intruding vehicle using said estimated azimuth angle, said estimated elevation angle and said first time-to-collision estimate as input parameters, and
• a collision avoidance module arranged to decide whether or not the avoidance manoeuvre should be performed based on any of at least one decision parameter, of which at least one is indicative of said second time-to-collision estimate.