Applying Frontier Cells Based Exploration and Lazy Theta* Path Planning over Single Grid-Based World Representation for Autonomous Inspection of Large 3D Structures with an UAS

Abstract

Aerial robots are a promising platform to perform autonomous inspection of infrastructures. For this application, the world is a large and unknown space, requiring light data structures to store its representation while performing autonomous exploration and path planning for obstacle avoidance. In this paper, we combine frontier cells based exploration with the Lazy Theta* path planning algorithm over the same light sparse grid-the octree implementation of octomap. Test-driven development has been adopted for the software implementation and the subsequent automated testing process. These tests provided insight into the amount of iterations needed to generate a path with different voxel configurations. The results for synthetic and real datasets are analyzed having as baseline a regular grid with the same resolution as the maximum resolution of the octree. The number of iterations needed to find frontier cells for exploration was smaller in all cases by, at least, one order of magnitude. For the Lazy Theta* algorithm there was a reduction in the number of iterations needed to find the solution in 75% of the cases. These reductions can be explained both by the existent grouping of regions with the same status and by the ability to confine inspection to the known voxels of the octree.

Fast Frontier-based Information-driven Autonomous Exploration with an MAV

“…Gao et al [8] focus on keeping track of visited key nodes in a topological graph while conducting frontier exploration. A more recent work on frontier-based autonomous inspection is presented in [9].…”

Efficient Lazy Theta* Path Planning over a Sparse Grid to Explore Large 3D Volumes with a Multirotor UAV

“…This research improves the efficiency of the implementation of Lazy Theta* previously presented in [7], an algorithm that has been applied successfully in competitions with multirotor UAVs [18] and fulfills the requirements mentioned above. For realistic obstacle avoidance, the concept of a flight corridor was introduced to detect obstacles that are around the trajectory.…”

“…Their applicability is bounded chiefly by creativity and novelty. Examples of tasks aided by UAVs are package transportation [1,2], industrial inspection [3,4,5,6,7,8], scene reconstruction [9,10,11], and environmental monitoring [12,13,14]. These applications, in daily life, take place outside controlled environments.…”

Guided Next Best View for 3D Reconstruction of Large Complex Structures

“…The ability to reconstruct 3D models of large structures has been utilized in various applications such as infrastructure inspection [1][2][3] and search and rescue [4,5]. Reconstruction tasks are typically performed using conventional methods either by following an autonomous procedure such as moving a sensor around the structure of interest at fixed waypoints or following manual procedure.…”

“…The genetic algorithm would then select the best path by evaluating the random paths based on the specified task. Moreover, frontier methods perform well in constrained areas and indoors [1,16]. In these environments, the frontier may exist at the start of a room or the end of a corridor.…”