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Avoidance
Avoidance strategies are the algorithms that will decide how the vehicle should react when and obstacle has been detected. They are responsible to determine if and obstacle pose a threat to the vehicle or if they can be ignored for the time being.
The project provides three Avoidance Strategies. Note that the prefix in the strategy name defines for what type of vehicle this avoidance can actuate.
Quadcopter shift avoidance is a strategy that tries to go around obstacles by shifting the vehicle to the left. If an obstacle has been detected as a threat to the vehicle, this strategy will break it and rotate the vehicle a fixed distance to the left, using the mission target as the center point for the rotation. Once the rotation is over, the algorithm reevaluates the obstacle. It will keep rotating until the path from the vehicle to the target is clear of obstacles given the safe distance threshold.
Quadcopter Stop Avoidance is the simplest form of Avoidance Strategy. It will consider any detected obstacle as a threat to the vehicle and will send a break command, stopping the vehicle. Once the vehicle has finished breaking, the control will be sent back to the previous controller. The process will repeat every time an obstacle is detected.
VFF is based on the concept that the mission target "applies a force" in the vehicle that pulls it towards itself, while obstacles "apply a force" in the vehicle that push it away from them. For every detected obstacle, this algorithm will calculate this 'force' base on its distance from the vehicle and its position. Them, it will add all the forces and the resulting force will determine the direction which the vehicle should move.