Abstract
A reactive collision avoidance algorithm is proposed to enable safe autonomous flight in the presence of multiple dynamic obstacles. A position-controlled hexacopter equipped with a visual sensor obtaining obstacle information is considered as an Unmanned Aerial Vehicle (UAV) platform. The proposed method centers on the concept of bounding tube which intrinsically extends the static bounding box to incorporate forthcoming movement of the obstacles into the collision avoidance framework. The processing pipeline consists of separate components for each of the sequential tasks in obstacle sensing and tracking. Computation of a spherical bounding box for each obstacle is followed by discrete-time Kalman filtering for prediction of obstacle trajectory to detect potential collision. If the current course of UAV turns out highly likely to end in collision with any of the obstacles, the vehicle steers to an aiming point chosen from among the bundle of candidates produced by constructing a bounding tube that takes account of predicted obstacle motion. The bounding-tube-based aiming point generation extends seamlessly to the case with multiple moving obstacles through running in series with multi-obstacle track management that combines hierarchical clustering of sensory data points for obstacle identification and a simple geometric method for data association. Numerical simulations are conducted to verify the performance of the proposed collision avoidance algorithm.
Highlights
R ECENT development of the autonomy and aerospace technologies has brought increased opportunities for Unmanned Aerial Vehicles (UAVs) to replace manned operations in the civil and military applications
Numerical simulations considering maneuvering obstacles show that the proposed algorithm based on the bounding tube successfully avoids collision by producing aiming point candidates that are not invaded by the movement of the obstacle, whereas the previous algorithm developed in [24] based only on the instantaneous bounding box results in failure
The proposed method utilized the aiming point candidates generated on the bounding tube which was introduced in this study to take explicit account of the movement of obstacles at the stage of avoidance maneuver planning
Summary
R ECENT development of the autonomy and aerospace technologies has brought increased opportunities for Unmanned Aerial Vehicles (UAVs) to replace manned operations in the civil and military applications. This study presents a reactive collision avoidance guidance algorithm for multi-rotor UAVs to prevent close encounter with multiple moving obstacles with lateral acceleration in three-dimensional space. The proposed method constructs a bounding tube around each obstacle to find aiming point candidates for the avoidance maneuver whenever the UAV is determined to be on a collision course with the obstacle. Numerical simulations considering maneuvering obstacles show that the proposed algorithm based on the bounding tube successfully avoids collision by producing aiming point candidates that are not invaded by the movement of the obstacle, whereas the previous algorithm developed in [24] based only on the instantaneous bounding box results in failure. Two main parts: i) obstacle sensor and tracking filter, and ii) position tracking controller
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