Researchers are increasingly focused on enabling groups of multiple unmanned vehicles to operate cohesively in complex,real-world environments,where coordinated formation control and obstacle avoidance are essential f...Researchers are increasingly focused on enabling groups of multiple unmanned vehicles to operate cohesively in complex,real-world environments,where coordinated formation control and obstacle avoidance are essential for executing sophisticated collective tasks.This paper presents a Distributed Formation Control and Obstacle Avoidance(DFCOA)framework for multi-unmanned ground vehicles(UGV).DFCOA integrates a virtual leader structure for global guidance,an improved A^(*)path planning algorithm with an advanced cost function for efficient path planning,and a repulsive-force-based improved vector field histogram star(VFH^(*))technique for collision avoidance.The virtual leader generates a reference trajectory while enabling distributed execution;the improved A^(*)algorithm reduces planning time and number of nodes to determine the shortest path from the starting position to the goal;and the improved VFH^(*)uses 2D LiDAR data with inter-agent repulsive force to simultaneously avoid collision with obstacles and maintain safe inter-vehicle distances.The formation stability of the proposed DFCOA reaches 95.8%and 94.6%in two scenarios,with root mean square(RMS)centroid errors of 0.9516 and 1.0008 m,respectively.Velocity tracking is precise(velocity centroid error RMS of 0.2699 and 0.1700 m/s),and linear velocities closely match the desired 0.3 m/s.Safety metrics showed average collision risks of 0.7773 and 0.5143,with minimum inter-vehicle distances of 0.4702 and 0.8763 m,confirming collision-free navigation of four UGVs.DFCOA outperforms conventional methods in formation stability,path efficiency,and scalability,proving its suitability for decentralized multi-UGV applications.展开更多
The main objective of the study is to assess the growth and expansion of public health(PH)research works by Bangladeshi authors from various perspectives such as quantum of growth,patterns of collaboration, and produc...The main objective of the study is to assess the growth and expansion of public health(PH)research works by Bangladeshi authors from various perspectives such as quantum of growth,patterns of collaboration, and productivity of authorship, among others. The present research uses a scientometric technique to examine secondary literature. Between 2000 and 2015, 871literature by Bangladeshi writers and 3,71,389 literature by worldwide authors on PH were retrieved from the Scopus database and evaluated using quantitative indicators to study growth and development from various perspectives. The highest growth in terms of the number of publications has been observed in the year 2015(133) and the lowest in 2001(10). The PR(Percent of Growth Rate) shows that 2001 was the deepest decreasing year(-38%) whereas 2002was the most increasing year(90%). During the study, RGR(Relative Growth Rate) values of Bangladeshi contributions to PH literature varied from 0.16 to 0.55, with an average of 0.27. The CC(Collaborative Coefficient) value indicates that during the research period, there was a substantial amount of collaboration among the authors. At the same time, the PPA(Productivity Per Author) value(0.31) denotes that throughout the era, each Bangladeshi author produced less than half of a publication per year. The mean Activity Index(AI) during 2000-2015 was 89.14,which reflects lower activity than the world’s average in PH literature. It was also observed that research productivity in public health of Bangladesh follows Lotka’s inverse rule of author production. According to the findings, there is a strong link between public health research output in emerging and developed nations.展开更多
文摘Researchers are increasingly focused on enabling groups of multiple unmanned vehicles to operate cohesively in complex,real-world environments,where coordinated formation control and obstacle avoidance are essential for executing sophisticated collective tasks.This paper presents a Distributed Formation Control and Obstacle Avoidance(DFCOA)framework for multi-unmanned ground vehicles(UGV).DFCOA integrates a virtual leader structure for global guidance,an improved A^(*)path planning algorithm with an advanced cost function for efficient path planning,and a repulsive-force-based improved vector field histogram star(VFH^(*))technique for collision avoidance.The virtual leader generates a reference trajectory while enabling distributed execution;the improved A^(*)algorithm reduces planning time and number of nodes to determine the shortest path from the starting position to the goal;and the improved VFH^(*)uses 2D LiDAR data with inter-agent repulsive force to simultaneously avoid collision with obstacles and maintain safe inter-vehicle distances.The formation stability of the proposed DFCOA reaches 95.8%and 94.6%in two scenarios,with root mean square(RMS)centroid errors of 0.9516 and 1.0008 m,respectively.Velocity tracking is precise(velocity centroid error RMS of 0.2699 and 0.1700 m/s),and linear velocities closely match the desired 0.3 m/s.Safety metrics showed average collision risks of 0.7773 and 0.5143,with minimum inter-vehicle distances of 0.4702 and 0.8763 m,confirming collision-free navigation of four UGVs.DFCOA outperforms conventional methods in formation stability,path efficiency,and scalability,proving its suitability for decentralized multi-UGV applications.
文摘The main objective of the study is to assess the growth and expansion of public health(PH)research works by Bangladeshi authors from various perspectives such as quantum of growth,patterns of collaboration, and productivity of authorship, among others. The present research uses a scientometric technique to examine secondary literature. Between 2000 and 2015, 871literature by Bangladeshi writers and 3,71,389 literature by worldwide authors on PH were retrieved from the Scopus database and evaluated using quantitative indicators to study growth and development from various perspectives. The highest growth in terms of the number of publications has been observed in the year 2015(133) and the lowest in 2001(10). The PR(Percent of Growth Rate) shows that 2001 was the deepest decreasing year(-38%) whereas 2002was the most increasing year(90%). During the study, RGR(Relative Growth Rate) values of Bangladeshi contributions to PH literature varied from 0.16 to 0.55, with an average of 0.27. The CC(Collaborative Coefficient) value indicates that during the research period, there was a substantial amount of collaboration among the authors. At the same time, the PPA(Productivity Per Author) value(0.31) denotes that throughout the era, each Bangladeshi author produced less than half of a publication per year. The mean Activity Index(AI) during 2000-2015 was 89.14,which reflects lower activity than the world’s average in PH literature. It was also observed that research productivity in public health of Bangladesh follows Lotka’s inverse rule of author production. According to the findings, there is a strong link between public health research output in emerging and developed nations.
