Research On Microscopic Simulation Model Of Pedestrian Flow Based On Voronoi Diagram

With the continuous development of social economy and urbanization,pedestrian gathering and transfer activities are becoming more and more frequent in various pedestrian facilities such as shopping centers,stadiums,cinemas and theaters,and transportation hubs.How to optimize and improve the mobility efficiency of pedestrians under normal conditions will effectively affect the travel experience and the sense of happiness of each pedestrian.Among all kinds of pedestrian facilities,the mobility efficiency of pedestrians is easily affected by the organization and management of pedestrians and the space design and layout of facilities.Walking as the most basic mode of travel has received more and more attention and research.As a typical interdisciplinary discipline,pedestrian dynamics needs to integrate the knowledge of traffic engineering,statistical physics,computer science,behavioral science,safety science,system science,psychology and other disciplines.The commonly used research methods mainly include: simulation research based on the microscopic behavior characteristics of pedestrians and statistical analysis based on the movement characteristics experimental data of pedestrians.When the pedestrian flow pass through the basic units of large walking facilities,such as spatial bottlenecks,straight corridors and L-shaped corridors,the macroscopic phenomena of pedestrians such as crowd gathering before the bottleneck,pedestrian zipper effect and invisible bottleneck in the turning area will appear due to the basic microscopic behaviors of pedestrians such as detour,follow,offset and turn.Through the research on the micro behavior and macro characteristics of pedestrian flow,digging out the generation mechanism of macro phenomenon characteristics of pedestrian flow is helpful to guide the spatial layout design and pedestrian flow organization and management,so as to improve the mobility efficiency of pedestrians and achieve the maximum utilization of pedestrian facilities.This paper takes the pedestrian flow through spatial bottlenecks,straight corridors,and L-shaped corridors under non-panic and non-crowded conditions as the research object.Based on geometric features such as the irregular division of Voronoi diagrams,the microscopic simulation model of pedestrian flow is constructed to analyze and study the detour,follow,offset,turn and other basic microscopic behaviors of pedestrians,explore the generation mechanism of macroscopic phenomena such as “fan-shaped” queuing in front of the bottleneck,pedestrian zipper effect,and invisible bottleneck in the turning area based on simulation,and establish the relationship between the individual microscopic behavior characteristics of pedestrians and the macroscopic characteristics of the group.This paper mainly carries out the following research:(1)Based on Voronoi diagram,a new heuristic micro simulation model of pedestrian flow is constructedBased on the Voronoi diagram,a new heuristic model is constructed to simulate the pedestrian flow under non-panic and non-crowded conditions.The model takes into account the heuristic rules of pedestrian preferences and willingness needs,and embeds the dynamic space requirements of pedestrians,spatial movement,and the mechanisms of detouring and following,microscopic anti-deadlock,and site-fine-tuning.In the model,dynamic space requirement is used to calculate the effective area ratio;pedestrian movement rules are used to avoid pedestrian overlap and collision;preference and willingness needs are used to describe the willingness of pedestrians to detour or follow other pedestrians;in the detour and follow rules,the concepts of“allow-areas and denial-areas” are put forward to optimize the direction and magnitude of velocity of pedestrian avoidance and detour others based on the position of all the neighbors,so as to achieve a balance between avoiding conflict and minimizing detour distance;the mechanism of microscopic anti-deadlock is used to avoid the micro-conflict between pedestrians;the mechanism of site-fine-tuning is used to avoid the excessive proximity between pedestrians.The model simulates the pedestrian dynamics of non-panic and non-crowded scenarios,such as straight corridor with or without obstacles,and single exit evacuation,which reproduces the micro behaviors of pedestrians,such as avoiding single or group obstacles,following forward movement of pedestrians,and reproduces many macro phenomena,such as pedestrian "line" movement,"fan-shaped" queue in front of bottleneck,and "diamond shaped" area in front of and behind obstacles.Under different overall density conditions,the relationship between the velocity and density of pedestrians is consistent with the empirical data.It is verified that "detour" is helpful to improve the mobility efficiency in the case of low density,and "follow" is helpful to ensure the mobility order in the case of high density.This model combines the advantages of cellular automata model and social force model,and overcomes the disadvantages of cellular automata model,such as fixed spatial division,superposition of social force model and lack of active detour.(2)The generation mechanism of zipper phenomenon of pedestrian flow in walking corridor is excavatedThe unidirectional pedestrian flow in the corridor is taken as a research object,the generation mechanism of the pedestrian zipper phenomenon is analyzed from the perspective of optimal visual field and walking comfort of pedestrians.Then the visual attention and visual occlusion of pedestrians are used to describe the factors which affect the zipper deviation during pedestrian movement,the local density of pedestrians is used to describe the walking comfort of pedestrians.It is assumed that the zipper phenomenon is mainly caused by the pedestrians' seeking for the best visual field and walking comfort in the walking process,and it is used to guide the simulation of the micro-behavior of pedestrian flow.(3)Based on Voronoi diagram,a micro-simulation model of pedestrian flow considering the mechanism of zipper phenomenon is constructedConsidering the influence of pedestrians in different distances and directions in the central pedestrian's field of vision on their moving velocity,the moving velocity of the central pedestrian is corrected,and a velocity correction model of pedestrians based on the Voronoi diagram is constructed to be suitable for the pedestrian flow simulation under normal state and non-crowded conditions,which overcomes the deficiency of the jitter and overlap phenomenon of the traditional social force model.Based on the generation mechanism of the zipper phenomenon in pedestrian flow,the zipper sensitivity coefficient is introduced to describe the willingness degree of pedestrian objective deviation.Based on the optimal state of the pedestrian zipper effect,the lateral deviation mechanism of pedestrian movement is proposed to describe the behavior of the pedestrian seeking the optimal vision and walking comfort,so as to obtain the optimal position of the pedestrian movement.By means of deviation willingness degree and deviation rule,the willingness degree and concrete process of pedestrian movement deviation are described respectively.The simulation results truly reproduce the normal pedestrian flow through the corridor.The self-organized pedestrian flow with uniform distribution and the pedestrian zipper effect can also be observed.Furthermore,through the simulation results,we can see that the number of zipper layers for pedestrians is proportional to the width of the corridor.The comparison of simulated pedestrian data with the empirical data indicates that the fundamental diagram of velocity-density relation of our model is in good agreement with the empirical data.A comparison between with and without considering the zipper effect shows that the larger the proportion of pedestrians actively willing to laterally deviate,the more helpful it will be to improve the moving velocity,comfort and space utilization of pedestrians in the corridor.(4)The turning characteristics of pedestrian flow in L-shaped pedestrian corridor are excavatedThe unidirectional pedestrian flow in an L-shaped corridor is taken as the research object,three experimental scenarios,no obstacles in the turning zone,diagonal layout of obstacles along the turning zone,and diagonal layout of obstacles in the vertical turning zone are constructed.Behavioral characteristics such as pedestrian movement trajectory and velocity distribution are analyzed through controllable experiments of pedestrians.Based on the pedestrian movement point,the L-shaped corridor can be divided into four parts: the vertical straight area,the transition area,the turning area and the horizontal straight area.In the transition area,pedestrians approach the top of the corner;in the turning area,the longer the distance from the center of the corner is,the longer the distance of the pedestrian around the arc will be.The pedestrians pass through the curve in a smooth arc can form the multiple track clusters,and the phenomena of "invisible bottleneck" and "curved triangle idle area" can be seen.(5)Based on Voronoi diagram,a micro-simulation model of pedestrian flow considering pedestrian turning behavior is constructedBased on the movement characteristics of pedestrians in different areas of L-shaped corridor,the movement rules of pedestrians in different areas are constructed.Based on the Voronoi diagram,a velocity correction model considering the turning behavior of pedestrians is built,and the turning rules of pedestrians through L-shaped corridor are embedded.The simulation research is conducted on the scenes with or without obstacles and asymmetric L-shaped corridors respectively to simulate and reproduce the turning behavior of pedestrians,and analyze the distribution of pedestrian velocity and individual density at different stages.The L-shaped corridor can be divided into the vertical straight area,the transition area,the turning area,and the horizontal straight area.When pedestrians pass through the turning walking area,the phenomena of "invisible bottleneck" and "curved triangle idle area" can be observed.Besides,the streamline compression and multiple rows of pedestrian track clusters can be seen in the region.According to the characteristics of pedestrians walking through the L-shaped corridor,the turning rules of pedestrians are made,and the scenes with or without obstacles and asymmetric L-shaped corridor are simulated.Then,through the pedestrian simulation with our model,the turning behavior of pedestrians passing through curves like a smooth arc can be effectively reproduced.Moreover,the phenomena of "invisible bottleneck" and "curved triangle idle area" in the turning walking area can be seen in the simulation.At the same time,when the pedestrian flow passes through the four areas of the L-shaped corridor successively,the velocity distribution is consistent with the experimental data of the pedestrian,showing a "wavy" change characteristic of increasing first,then decreasing and then increasing.The simulation model also simulates the local density change of pedestrians due to the turning behavior,which verifies the unity of pedestrian velocity and local density change.The cognition of invisible bottleneck is helpful for the rational utilization and design of L-shaped corridor turning area.