FC-Planner: A Skeleton-guided Planning Framework for Fast Aerial Coverage of Complex 3D Scenes

3D coverage path planning for UAVs is a crucial problem in diverse practical applications. However, existing methods have shown unsatisfactory system simplicity, computation efficiency, and path quality in large and complex scenes. To address these challenges, we propose FC-Planner, a skeleton-guided planning framework that can achieve fast aerial coverage of complex 3D scenes without pre-processing. We decompose the scene into several simple subspaces by a skeleton-based space decomposition (SSD). Additionally, the skeleton guides us to effortlessly determine free space. We utilize the skeleton to efficiently generate a minimal set of specialized and informative viewpoints for complete coverage. Based on SSD, a hierarchical planner effectively divides the large planning problem into independent sub-problems, enabling parallel planning for each subspace. The carefully designed global and local planning strategies are then incorporated to guarantee both high quality and efficiency in path generation. We conduct extensive benchmark and real-world tests, where FC-Planner computes over 10 times faster compared to state-of-the-art methods with shorter path and more complete coverage. The source code will be open at https://github.com/HKUST-Aerial-Robotics/FC-Planner.Comment: Submitted to ICRA2024. 6 Pages, 6 Figures, 3 Tables. Code: https://github.com/HKUST-Aerial-Robotics/FC-Planner. Video: https://www.bilibili.com/video/BV1h84y1D7u5/?spm_id_from=333.999.0.0&vd_source=0af61c122e5e37c944053b57e313025

AutoTrans: A Complete Planning and Control Framework for Autonomous UAV Payload Transportation

The robotics community is increasingly interested in autonomous aerial transportation. Unmanned aerial vehicles with suspended payloads have advantages over other systems, including mechanical simplicity and agility, but pose great challenges in planning and control. To realize fully autonomous aerial transportation, this paper presents a systematic solution to address these difficulties. First, we present a real-time planning method that generates smooth trajectories considering the time-varying shape and non-linear dynamics of the system, ensuring whole-body safety and dynamic feasibility. Additionally, an adaptive NMPC with a hierarchical disturbance compensation strategy is designed to overcome unknown external perturbations and inaccurate model parameters. Extensive experiments show that our method is capable of generating high-quality trajectories online, even in highly constrained environments, and tracking aggressive flight trajectories accurately, even under significant uncertainty. We plan to release our code to benefit the community.Comment: Accepted by IEEE Robotics and Automation Letter

Research and Application of Shale Gas Reservoir-Wellbore Integrated Model Coupling Method

As a representative of emerging unconventional energy, shale gas has the characteristics of large reserves, long production cycle, and environmental protection. However, due to the complex geological characteristics of shale gas reservoirs, the economic development of shale gas reservoirs is difficult. In this paper, on the basis of a full investigation of relevant literature, according to the permeability mechanism of shale gas reservoirs, the productivity of horizontal wells in low-permeability gas reservoirs is studied, and an integrated dynamic simulation model of gas reservoir wellbore is established. And the historical fitting and dynamic forecasting are carried out, and the results are in good agreement with the actual situation

Study on stress sensitivity of bedding fractures and sand-filled fractures in shale oil reservoirs

Shale oil reservoirs are characterized by low porosity and ultra-low permeability, and hydraulic fracturing technology is needed to realize industrial oil flow. The sand-filled fractures formed in the shale fracturing process and the bedding fractures developed in the reservoir itself interact to form a shale oil fracture network system, which is the main migration channel for shale oil production. Studies have shown that the higher the degree of fracture development, the stronger the stress sensitivity of the reservoir, and the stress sensitive damage is an important factor that causes the decline of reservoir seepage capacity during shale oil production. In this paper, based on the shale samples in the Jiyang Depression, the flow capacity experiments of bedding fractures and sand-filled fractures were carried out to analyze the stress sensitivity characteristics of shale bedding fractures and sand-filled fractures, and to clarify the seepage capacity decline mechanism of complex fractures in shale. Provide experimental data and theoretical support for productivity prediction of block shale reservoirs after fracturing

Meta Architecture for Point Cloud Analysis

Recent advances in 3D point cloud analysis bring a diverse set of network architectures to the field. However, the lack of a unified framework to interpret those networks makes any systematic comparison, contrast, or analysis challenging, and practically limits healthy development of the field. In this paper, we take the initiative to explore and propose a unified framework called PointMeta, to which the popular 3D point cloud analysis approaches could fit. This brings three benefits. First, it allows us to compare different approaches in a fair manner, and use quick experiments to verify any empirical observations or assumptions summarized from the comparison. Second, the big picture brought by PointMeta enables us to think across different components, and revisit common beliefs and key design decisions made by the popular approaches. Third, based on the learnings from the previous two analyses, by doing simple tweaks on the existing approaches, we are able to derive a basic building block, termed PointMetaBase. It shows very strong performance in efficiency and effectiveness through extensive experiments on challenging benchmarks, and thus verifies the necessity and benefits of high-level interpretation, contrast, and comparison like PointMeta. In particular, PointMetaBase surpasses the previous state-of-the-art method by 0.7%/1.4/%2.1% mIoU with only 2%/11%/13% of the computation cost on the S3DIS datasets

Experimental study on evolution behaviors of triaxial-shearing parameters for hydrate-bearing intermediate fine sediment

Evolution behaviors of triaxial shearing parameters are very important for geo-technical re- sponse analysis during the process of extracting natural gas from hydrate-bearing reservoirs. In order to explore the effects of hydrate formation/decomposition on triaxial shearing behaviors of intermediate fine sediment, natural beach sand in Qingdao, China, which was sieved from 0.1 to 0.85 mm, was used and a series of triaxial shear tests were carried out in this paper. The principle of critical state was firstly used to explain the mechanism of strain softening and/or hardening failure mode. Moreover, an empirical model was provided for axial-lateral strain and corresponding model parameters calculation. Evolution rules of critical strength parameters were analyzed prominently. The results show that failure mode of sediment is controlled by several parameters, such as effective confining pressure, hydrate saturation, etc. Different axial-lateral strain model coefficients’ effect on strain relationships are different, probing into the physical meaning of each coefficient is essential for further understanding of strain relationships. Complex geo-technical response should be faced with the progress of producing natural gas from hydrate-bearing reservoir, because of sudden change of failure pattern and formation modulus. Further compressive study on critical condition of failure pattern is needed for proposed promising hydrate-bearing reservoirs.Cited as: Li, Y., Liu, C., Liu, L., Sun, J., Liu, H., Meng, Q. Experimental study on evolution behaviors of triaxial-shearing parameters for hydrate-bearing intermediate fine sediment. Advances in Geo-Energy Research, 2018, 2(1): 43-52, doi: 10.26804/ager.2018.01.0