Obstacle-free Areas Research Articles

The Impact of Pedestrian Lane Formation by Obstacles on Fire Evacuation Efficiency in the Presence of Unfair Competition

After a fire breaks out, pedestrians simultaneously move towards the exit and quickly form a crowded area near the exit. With the intensification of pedestrians’ tendencies towards unfair competition, there is an increase in pushing and collisions within the crowd. The possibility of stampedes within the crowd also gradually increases. Analyzing the causes and psychological tendencies behind pedestrian pushing and collisions has a positive effect on reducing crowd instability and improving evacuation efficiency. This research proposes a modified social force model considering the unfair competition tendency of pedestrians. The model considers factors such as the gap between pedestrians’ actual and maximum achievable speed, effective radius, and their distance from the exit. In order to overcome the shortage of “deadlock” in the classical social force model in a high-density environment, this research introduces the feature of variable pedestrian effective radius. The effective radius of pedestrians dynamically changes according to the density of the surrounding crowd and queuing time. Through validation, the evacuation efficiency of this model aligns well with the actual situation and effectively reflects pedestrians’ pushing and squeezing behaviors in high-density environments. This research also analyzes how to strategically arrange obstacles to mitigate the exacerbating effect of unfair pedestrian competition on exit congestion. Five experiments were conducted to analyze how the relative position of obstacles and exits, the number of evacuation paths, and the size of the obstacle-free area before the exit affect evacuation efficiency in the presence of unfair pedestrian competition. The results show that evacuation efficiency can be improved when obstacles play a role in guiding or reducing the interaction of pedestrians in different queues. However, when obstacles hinder pedestrians, the evacuation efficiency is reduced to a certain extent.

Research on Multi-Robot Formation Control Based on MATD3 Algorithm

This paper investigates the problem of multi-robot formation control strategies in environments with obstacles based on deep reinforcement learning methods. To solve the problem of value function overestimation in the deep deterministic policy gradient (DDPG) algorithm, this paper proposes an improved multi-agent twin delayed deep deterministic policy gradient (MATD3) algorithm under the CTDE framework combined with the twin delayed deep deterministic policy gradient (TD3) algorithm, which adopts a prioritized experience replay strategy to improve the learning efficiency. For the problem of difficult obstacle avoidance for a robot formation, a hybrid reward mechanism is designed to use different formation maintenance strategies in obstacle areas and obstacle-free areas to achieve the control goal of obstacle avoidance by reasonably changing the formation. The simulation experiments verified the effectiveness of the multi-robot formation control strategy designed in this paper, and comparative simulations verified that the algorithm has a faster convergence speed and more stable performance.

로봇운영체제를 이용한 보트의 자율운항 알고리즘 개발

According to the increasing interest and demand for the Autonomous Surface Vessels (ASV), the autonomous navigation system is being developed such as obstacle detection, avoidance, and path planning. In general, autonomous navigation algorithm controls the ship by detecting the obstacles with various sensors and planning path for collision avoidance. This study aims to construct and prove autonomous algorithm with integrated various sensor using the Robot Operating System (ROS). In this study, the safety zone technique was used to avoid obstacles. The safety zone was selected by an algorithm to determine an obstacle-free area using 2D LiDAR. Then, drift angle of the ship was controlled by the propulsion difference of the port and starboard side that based on PID control. The algorithm performance was verified by participating in the 2020 Korea Autonomous BOAT (KABOAT).

Toward Pleomorphic Reconfigurable Robots for Optimum Coverage

Buildings are constructed for accommodating living and industrial needs. Floor cleaning robots have been developed to cater to the demand of these buildings. Area coverage and coverage time are crucial performance factors of a floor cleaning robot. Reconfigurable tiling robots have been introduced over fixed shape robots to improve area coverage in floor cleaning applications compared to robots with fixed morphologies. However, area coverage and coverage time of a tiling robot compromised one another. This study proposes a novel concept that considers the ability of a tiling robot to configure both its morphology and size according to the environment. This concept is inspired by the pleomorphism that could be seen in bacteria. In this regard, P-hTetro, a pleomorphic tiling robot that can reconfigure its morphology and size, is considered. A novel coverage strategy for realizing the size reconfiguration is also proposed. According to this strategy, the robot covers obstacle-free areas with its maximum size, while an obstacle cluster is covered after shrinking to an optimum size. The optimum size for reconfiguration is determined by the genetic algorithm based on the arrangement of the environment. The performance and behavior of the proposed P-hTetro have been compared against that of an existing tiling robot which has a fixed size. According to the statistical outcomes, a tiling robot with the ability to reconfigure its size can significantly improve the performance in the aspects of area coverage and coverage time compared to a tiling robot with no ability to reconfigure its size.

Sledding-Related Injuries Among Children and Adults Treated in US Emergency Departments From 2008 to 2017.

To describe the epidemiology of sledding-related injuries among children and adults treated in US emergency departments (EDs). The researchers performed a retrospective analysis using data from the National Electronic Injury Surveillance System (NEISS). The NEISS collects data on consumer products-related and sports-related injuries treated in US EDs from approximately 100 hospitals that represent a probability sample of >5000 hospitals. Children (≤19 years of age) and adults who were treated for sledding-related injuries in EDs from 2008 to 2017. The researchers analyzed characteristics that included sex, body part injured, injury diagnosis, disposition from the ED, injury locale, injury mechanism, and sled type. All cases of sledding-related injuries were identified using NEISS product codes for sleds (1217), toboggans (1273), snow disks (1274), and snow tubes (1299). An estimated 220 488 patients [95% confidence interval (CI): 169 839-271 137] were treated in EDs for sledding-related injuries. Overall, the injury rate decreased significantly for both children and adults. Children accounted for 69.7% of the injury cases. Fractures were the most common injury diagnosis for children (23.9%) and adults (27.4%). Compared to adults, children were more likely to sustain a head injury [relative risk (RR): 1.91 (95% CI: 1.73-2.13)] and be diagnosed with a concussion or closed-head injury (CHI) [RR: 1.58 (95% CI: 1.35-1.84)]. Most patients were injured by a collision (63.2%). Snow tube and disk riders were more likely to sustain a concussion or CHI compared to sled and toboggan riders [RR: 1.53 (95% CI: 1.18-1.99)]. Injuries predominantly occurred when patients collided with objects in the environment (47.2%). Although sledding-related injuries decreased over the study period, more research and education to prevent these injuries is needed. The injury patterns and risk of injury type differed by age, with more head injuries sustained by children. Sledding should be performed in obstacle-free areas to reduce the risk of collision and while wearing helmets to mitigate head injuries.

Case study: Analysis of the propagation of noise generated by construction equipment

In the construction industry, workers are exposed to several risks, among them is the noise generated by construction equipment. This research had as its objective to evaluate the noise emitted by circular saws and concrete mixers, equipments usually present on construction sites, in order to propose noise control measures. For that purpose, the propagation curves (isoclines) of the sound pressure level (SPL) were measured and analyzed during the operation of three concrete mixers and three circular saws. The sound measurements were conductedwith the type 2 sound level meter, while for air temperature and wind speed a digital thermo-anemometer was used. Contour lines representing the isoclines of SPL were generated, and control measures were proposed. The results show that values of SPL above 85 dB(A) were observed at a maximal distance of 7 m from the source for concrete mixers and 16 m for circular saws. It was also confirmed that the furthest distance that the SPL is greater than 85 dB(A) depends on the number of barriers, screens and masonry walls. In obstacle-free areas, the rate of reduction of sound intensity was 1.26 dB(A) per meter for concrete mixers and 1.47 dB(A) per meter for circular saws. The SPL isoclines should be considered in planning of construction sites and organizing adequate control measures.

A constrained Delaunay Triangulation based RSUs deployment strategy to cover a convex region with obstacles for maximizing communications probability between V2I

In context of competent communication in Vehicular Ad-hoc Networks (VANets), an efficient algorithm for roadside units (RSUs) placement is considered to be a challenging task mainly due to the obstacles like buildings, trees, water-bodies and other constructions. The existing solutions available for this problem come with several limitations. While some of them consider only vehicle density and intersection popularity for RSUs position calculation (bypassing the global coverage), some others are unable to consider the obstacles present in the map to validate the model. In case of the hotspot based RSUs placement method, if the hotspot areas are changed for some reasons, the method does not work properly and even fails for real complex traffic scenarios. This paper presents a novel scheme for placing a given number of RSUs in a convex map and assigning transmission range to each of the RSUs in such a way that each and every position in the map can be covered certainly by at least one RSU despite several obstacles. The proposed method at first initial RSUs position is determined based on a Constrained Delaunay Triangulation (CDT) method to deploy the RSUs in obstacle free area, followed by an optimization method to find out the more significant position for RSUs deployment based on RSUs cost and end-to-end delay. And finally a multi-criteria decision making strategy for RSU selection is introduced for efficient communication between vehicle to infrastructure (V2I) or infrastructure to vehicle (I2V). The simulations have been performed in a real complex road traffic scenario of Ottawas downtown area considering all the obstacles. The simulation results show that the proposed method outperforms the existing methods with the improvement of about 7.7% in packet delivery rate, about 9% reduction in packet loss and about 22% reduction in end-to-end delay. Further, the impact has been analyzed by varying the vehicle density, vehicle flow and RSU cost. The proposed method is tested in different scenarios like Manhattan: Simple map, Erlangen: Medium map and Rome: Complex map to get more precise results.

Hybrid Method Based on Artificial Potential Field and Differential Game Theory for the UAV Path Planing

In this paper, a method of the UAV path planing in the complex environment by using artificial potential field and differential game theory is introduced. This article studies the pursuit evasion game of the dynamic path planing for the UAV. The fly zone of either the pursuer or the evader is divided into two categories, namely the obstacle areas and the obstacle-free areas. So we can use the artificial potential field in the obstacle areas,and we use differential game theory in the obstacle-free areas for the UAV. This method can apply to pursuit-evasion game in the complex environment for the UAV path planing.Not only the UAV can avoid obstacles but also they can find the best capture path.Finally,the simulation results verify its correctness and validity .

Trajectory tracking control with obstacle avoidance capability for unicycle-like mobile robot

Abstract In this paper the trajectory tracking control algorithm with obstacle avoidance capability is presented. As a robot gets into a neighborhood of the obstacle, the collision avoidance behavior is turned on. It is implemented using the artificial potential function (APF) that increases to infinity as the robot approaches a boundary of the obstacle. This feature guarantees collision avoidance. As avoidance behavior is active only in the neighborhood of the obstacle it does not affect the motion when there is no risk of the collision. Authors show that trajectory of the robot converges to desired one when a robot is out of the APF area. Due to a local characteristic of the APF, the implementation of the algorithm of the robot that uses only on-board sensors is possible. The stability proof is presented for both a near obstacle and obstacle-free areas. Effectiveness of the algorithm is illustrated with experiments on a real robot in an environment with static circle-shaped obstacles.

A 13-year analysis from Switzerland of non-fatal sledging (sledding or tobogganing) injuries

IntroductionWinter sports have evolved from an upper class activity to a mass industry. Especially sledging regained popularity at the start of this century, with more and more winter sports resorts offering sledge runs. This study investigated the rates of sledging injuries over the last 13 years and analysed injury patterns specific for certain age groups, enabling us to make suggestions for preventive measures. MethodsWe present a retrospective analysis of prospectively collected data. From 1996/1997 to 2008/2009, all patients involved in sledging injuries were recorded upon admission to a Level III trauma centre. Injuries were classified into body regions according to the Abbreviated Injury Scale (AIS). The Injury Severity Score (ISS) was calculated. Patients were stratified into 7 age groups. Associations between age and injured body region were tested using the chi-squared test. The slope of the linear regression with 95% confidence intervals was calculated for the proportion of patients with different injured body regions and winter season. Results4956 winter sports patients were recorded. 263 patients (5%) sustained sledging injuries. Sledging injury patients had a median age of 22 years (interquartile range [IQR] 14–38 years) and a median ISS of 4 (IQR 1–4). 136 (51.7%) were male. Injuries (AIS≥2) were most frequent to the lower extremities (n=91, 51.7% of all AIS≥2 injuries), followed by the upper extremities (n=48, 27.3%), the head (n=17, 9.7%), the spine (n=7, 4.0%). AIS≥2 injuries to different body regions varied from season to season, with no significant trends (p>0.19). However, the number of patients admitted with AIS≥2 injuries increased significantly over the seasons analysed (p=0.031), as did the number of patients with any kind of sledging injury (p=0.004). Mild head injuries were most frequent in the youngest age group (1–10 years old). Injuries to the lower extremities were more often seen in the age groups from 21 to 60 years (p<0.001). ConclusionMild head trauma was mainly found in very young sledgers, and injuries to the lower extremities were more frequent in adults. In accordance with the current literature, we suggest that sledging should be performed in designated, obstacle-free areas that are specially prepared, and that children should always be supervised by adults. The effect of routine use of helmets and other protective devices needs further evaluation, but it seems evident that these should be obligatory on official runs.

Robot Navigation Control Based on Monocular Images: An Image Processing Algorithm for Obstacle Avoidance Decisions

This paper covers the use of monocular vision to control autonomous navigation for a robot in a dynamically changing environment. The solution focused on using colour segmentation against a selected floor plane to distinctly separate obstacles from traversable space: this is then supplemented with canny edge detection to separate similarly coloured boundaries to the floor plane. The resulting binary map (where white identifies an obstacle‐free area and black identifies an obstacle) could then be processed by fuzzy logic or neural networks to control the robot’s next movements. Findings show that the algorithm performed strongly on solid coloured carpets, wooden, and concrete floors but had difficulty in separating colours in multicoloured floor types such as patterned carpets.

Effects of surface microtopography on the assembly of the osteoclast resorption apparatus

Bone degradation by osteoclasts depends on the formation of a sealing zone, composed of an interlinked network of podosomes, which delimits the degradation lacuna into which osteoclasts secrete acid and proteolytic enzymes. For resorption to occur, the sealing zone must be coherent and stable for extended periods of time. Using titanium roughness gradients ranging from 1 to 4.5 µm R(a) as substrates for osteoclast adhesion, we show that microtopographic obstacles of a length scale well beyond the range of the 'footprint' of an individual podosome can slow down sealing-zone expansion. A clear inverse correlation was found between ring stability, structural integrity and sealing-zone translocation rate. Direct live-cell microscopy indicated that the expansion of the sealing zone is locally arrested by steep, three-dimensional 'ridge-like barriers', running parallel to its perimeter. It was, however, also evident that the sealing zone can bypass such obstacles, if pulled by neighbouring regions, extending through flanking, obstacle-free areas. We propose that sealing-zone dynamics, while being locally regulated by surface roughness, are globally integrated via the associated actin cytoskeleton. The effect of substrate roughness on osteoclast behaviour is significant in relation to osteoclast function under physiological and pathological conditions, and may constitute an important consideration in the design of advanced bone replacements.

Present status and development of prevention of blindness and ophthalmic epidemiologic studies in China

Blindness prevention and ophthalmic epidemiology studies in China have obtained greatest progress in the past five years since 2005. For example, the secondary sampling epidemiologic study of disabled persons in China in 2006 showed that the major causes of blindness and vision impairment were cataract (56.7%), retinal and uveal diseases (14.1%) and corneal diseases (10.3%). Important blindness prevention projects, such as "Sight first, China action" stage II project and "Free cataract surgeries for one million poor patients" project, have achieved their goals. From 2005 to 2009, 3.871 millions of cataract surgeries were performed in China, and the cataract surgical rate increased to 796.2 per million population in 2009. Cataract surgery obstacle-free areas have been built in 673 counties, 70 cities and 2 provinces since 2007. The visual performance of 175,501 low-vision patients have been improved by low-vision aids, and 47,009 blind persons have been offered walk mobility training course. Furthermore, achievements and progress have been obtained in primary eye care, prevention and treatment for trachoma, childhood eye diseases and diabetic retinopathy. These results has met the requirements established by Chinese government, but has not reached the goal of "Vision 2020". Certain problems still exist in China, including low cataract surgical rate, major avoidable blinding diseases not eliminated, and lack of innovative and profound epidemiological studies. Future Chinese ophthalmic epidemiology studies may focus on original investigation and molecular research. In order to realize the goal of "Vision 2020" and eliminate avoidable cataract blindness, all kinds of eye care services should be integrated, and various prevention and treatment strategies with low cost and superior quality for cataract, retinal diseases, corneal diseases, trachoma, refractive error, low vision, and glaucoma should be used.

Efficient learning of variable-resolution cognitive maps for autonomous indoor navigation

This paper presents an adaptive method that allows mobile robots to learn cognitive maps of indoor environments incrementally and online. Our approach models the environment. By means of a variable-resolution partitioning that discretizes the world in perceptually homogeneous regions. The resulting model incorporates both a compact geometrical representation of the environment and a topological map of the spatial relationships between its obstacle-free areas. The efficiency of the learning process is based on the use of local memory-based techniques for partitioning and of active learning techniques for selecting the most appropriate region to be explored next. In addition, a feedforward neural network is used to interpret sensor readings. We present experimental results obtained with two different mobile robots, the Nomad 200 and Khepera. The current implementation of the method relies on the assumption that obstacles are parallel or perpendicular to each other. This results in variable-resolution partitioning consisting of simple rectangular partitions and reduces the complexity of treating the underlying geometrical properties.