Complex Environment Path Planning for Unmanned Aerial Vehicles

Flying safely in complex urban environments is a challenge for unmanned aerial vehicles because path planning in urban environments with many narrow passages and few dynamic flight obstacles is difficult. The path planning problem is decomposed into global path planning and local path adjustment in this paper. First, a branch-selected rapidly-exploring random tree (BS-RRT) algorithm is proposed to solve the global path planning problem in environments with narrow passages. A cyclic pruning algorithm is proposed to shorten the length of the planned path. Second, the GM(1,1) model is improved with optimized background value named RMGM(1,1) to predict the flight path of dynamic obstacles. Herein, the local path adjustment is made by analyzing the prediction results. BS-RRT demonstrated a faster convergence speed and higher stability in narrow passage environments when compared with RRT, RRT-Connect, P-RRT, 1-0 Bg-RRT, and RRT*. In addition, the path planned by BS-RRT through the use of the cyclic pruning algorithm was the shortest. The prediction error of RMGM(1,1) was compared with those of ECGM(1,1), PCGM(1,1), GM(1,1), MGM(1,1), and GDF. The trajectory predicted by RMGM(1,1) was closer to the actual trajectory. Finally, we use the two methods to realize path planning in urban environments.

ADD-RRV for motion planning in complex environments

In this paper, we present a novel sampling-based motion planning method in various complex environments, especially with narrow passages. We use online the results of the planner in the ADD-RRT framework to identify the types of the local configuration space based on the principal component analysis (PCA). The identification result is then used to accelerate the expansion similar to RRV around obstacles and through narrow passages. We also propose a modified bridge test to identify the entrance of a narrow passage and boost samples inside it. We have compared our method with known motion planners in several scenarios through simulations. Our method shows the best performance across all the tested planners in the tested scenarios.

Innovation and the Three Detours for Economic Growth beyond the Middle-Income Stage

This chapter begins by acknowledging the differences in the economic growth mechanisms employed by advanced economies and latecomer economies at middle- or lower-income stages and by highlighting a very “narrow passage” between these countries. The chapter explains the nature of the narrow passage in terms of three detours. The first detour is promoting imitative innovations in the form of petit patents and trademarks instead of trying to promote a high level of IPR protection, including patent rights. The second detour is first promoting domestic value-added and reducing a country’s reliance on GVCs before an economy is fully coupled with GVCs. The third detour is specializing in short-cycle technology-based sectors instead of trying to directly enter long-cycle technology-based sectors/segments. While the consolidation of technological capabilities has long been suggested as a vital requirement for economic catch-up, this chapter shows that such consolidation must be carefully designed and implemented.

Collision Free Smooth Path for Mobile Robots in Cluttered Environment Using an Economical Clamped Cubic B-Spline

Mobile robots have various applications in agriculture, autonomous cars, industrial automation, planetary exploration, security, and surveillance. The generation of the optimal smooth path is a significant aspect of mobile robotics. An optimal path for a mobile robot is measured by various factors such as path length, path smoothness, collision-free curve, execution time, and the total number of turns. However, most of the planners generate a non-smooth less optimal and linear piecewise path. Post processing smoothing is applied at the cost of increase in path length. Moreover, current research on post-processing path smoothing techniques does not address the issues of post smoothness collision and performance efficiency. This paper presents a path smoothing approach based on clamped cubic B-Spline to resolve the aforementioned issues. The proposed approach has introduced an economical point insertion scheme with automated knot vector generation while eliminating post smoothness collisions with obstacles. It generates C2 continuous path without any stitching point and passes more closely to the originally planned path. Experiments and comparison with previous approaches have shown that the proposed approach generates better results with reduced path length, and execution time. The test cases used for experiments include a simple structure environment, complex un-structured environment, an environment full of random cluttered narrow obstacles, and a case study of an indoor narrow passage.

Human stampedes at mass gatherings: An overview

The main aim of this study is to present an overview of human stampedes and to identify the major triggering factors with respect to the type of events leading to number of fatalities and injuries. Considering major crowd incidents, the stampedes were categorized based on location, triggering factor, type of event and year of occurrence. This paper lists a total of 137 stampedes occurred all over the world between the years 1883 and 2017. The details include the name and type of event, location of the event, number of injuries and fatalities, probable reason for the stampede and type of reliable source. Stampedes are classified based on type of events as religious, sports, entertainment, festival, political and others. Among all types of events, religious gatherings cause 64% of total fatalities and 51% injuries. The triggering factors are identified as rumours, fire, structural failure, narrow passage, overcrowding and others. Out of all the triggering factors mentioned above, narrow passage causes about 27% fatalities followed by overcrowding and rumours with 23 and 21% respectively. The majority of injuries caused by overcrowding turn out to be 35%. It is also observed that the frequency of stampede occurrences increasing since 1980. This study can be considered as an initial step in giving an overview of human stampedes, which would help to prepare a framework based on the past experiences. Further, it can give better insights for large-scale crowd management and to minimize the loss of human lives in future.

Free space of rigid objects: caging, path non-existence, and narrow passage detection

In this work, we propose algorithms to explicitly construct a conservative estimate of the configuration spaces of rigid objects in two and three dimensions. Our approach is able to detect compact path components and narrow passages in configuration space which are important for applications in robotic manipulation and path planning. Moreover, as we demonstrate, they are also applicable to identification of molecular cages in chemistry. Our algorithms are based on a decomposition of the resulting three- and six-dimensional configuration spaces into slices corresponding to a finite sample of fixed orientations in configuration space. We utilize dual diagrams of unions of balls and uniform grids of orientations to approximate the configuration space. Furthermore, we carry out experiments to evaluate the computational efficiency on a set of objects with different geometric features thus demonstrating that our approach is applicable to different object shapes. We investigate the performance of our algorithm by computing increasingly fine-grained approximations of the object’s configuration space. A multithreaded implementation of our approach is shown to result in significant speed improvements.