双出口房间内疏散行人流的仿真和实验研究

为研究行人疏散过程中的路径选择行为, 提出了一个基于元胞自动机的行人微观模型, 并组织了三组双出口教室内的学生疏散实验. 模型中, 行人路径选择行为受其到出口距离、前方路径通行能力和行人间排斥力影响. 通过观察实验结果, 得到一些相关现象. 利用实验结果对模型参数进行校正. 利用校正模型对该教室内疏散学生流进行仿真, 结果表明 模型能有效地刻画教室内学生流的疏散特征, 疏散时间随学生人数线性增加. 该研究有助于类似场景中行人疏散策略和方案的制定. 关键词： 元胞自动机 行人疏散 仿真 实验     

The escape of pedestrians with view radius

In this brief letter, we modify the classic social force model of Helbing which is applied to simulate how a pedestrian gets outside a hall full of smoke. As the Vicsek model does, the view radius is introduced to describe the range the pedestrian can see. The relation between the evacuation time and the view radius is studied with different numbers of pedestrians. The results show that the shorter the view radius is, the more time walkers will spend escaping, and even fail to escape. And the relation between the number of remaining walkers and the view radius shows non-monotonicity, if the number of pedestrians is larger than 600. And lastly, we propose to enlarge the width of the exit or to add two small exits in the corners, which may decrease the evacuation time greatly and obviously reduce the number of remaining walkers.     

A new collision avoidance model for pedestrian dynamics

The pedestrians can only avoid collisions passively under the action of forces during simulations using the social force model, which may lead to unnatural behaviors. This paper proposes an optimization-based model for the avoidance of collisions, where the social repulsive force is removed in favor of a search for the quickest path to destination in the pedestrian's vision field. In this way, the behaviors of pedestrians are governed by changing their desired walking direction and desired speed. By combining the critical factors of pedestrian movement, such as positions of the exit and obstacles and velocities of the neighbors, the choice of desired velocity has been rendered to a discrete optimization problem. Therefore,it is the self-driven force that leads pedestrians to a free path rather than the repulsive force, which means the pedestrians can actively avoid collisions. The new model is verified by comparing with the fundamental diagram and actual data. The simulation results of individual avoidance trajectories and crowd avoidance behaviors demonstrate the reasonability of the proposed model.     

基于元胞自动机的行人疏散流仿真研究

基于元胞自动机对行人疏散流进行仿真研究.模型利用两个动态参数反映行人移动区域内的疏散情况,从而决定行人的行为选择.模型中行人可以根据自身周围的情况选择移动、等待行为.本文仿真研究了行人在正常疏散环境下,系统规模、疏散人数、安全出口宽度、多个安全出口布局对行人疏散时间的影响.研究结果表明,行人疏散时间随行人数量呈线性增加;随安全出口宽度呈负指数性减少;同时,多个安全出口布局的不平衡也会对行人的疏散过程和疏散时间产生一定的影响. 关键词： 元胞自动机 行人疏散流 动态参数 疏散时间     

Experiment and modeling of paired effect on evacuation from a three-dimensional space

A novel three-dimensional cellular automata evacuation model was proposed based on stairs factor for paired effect and variety velocities in pedestrian evacuation. In the model pedestrians' moving probability of target position at the next moment was defined based on distance profit and repulsive force profit, and evacuation strategy was elaborated in detail through analyzing variety velocities and repulsive phenomenon in moving process. At last, experiments with the simulation platform were conducted to study the relationships of evacuation time, average velocity and pedestrian velocity. The results showed that when the ratio of single pedestrian was higher in the system, the shortest route strategy was good for improving evacuation efficiency; in turn, if ratio of paired pedestrians was higher, it is good for improving evacuation efficiency to adopt strategy that avoided conflicts, and priority should be given to scattered evacuation.     

An extended model for describing pedestrian evacuation under the threat of artificial attack

An extended floor field model was proposed to investigate evacuation behaviors of pedestrians under the threat of artificial attack. In this model, pedestrian movement governed by the static and dynamic floor field, and the motion and assault of artificial attacker were involved simultaneously. Further, injuries with lower velocity and deaths of pedestrians caused by the attacker during evacuation were considered. And a new parameter $k_t$ was introduced. It is the sensitivity coefficient of attack threat floor field and could reflect quantitatively the extent of effect of attack threat on the decision-making of the individual. Moreover, effects of several key parameters such as the sensitivity coefficient, assault intensity and pedestrian density on evacuation dynamics were studied. Results show that pedestrian evacuation would display interesting phenomena transiting from rolling behavior to along-the-wall motion with aggravating extent of the impact of attackers on pedestrians, which refers $k_t$ in the model varying from 0.5 to 0.8. As assault intensity increases, more casualties would be caused and the available evacuation time would decrease, which means people have to flee the room in a shorter time period for survival. When the pedestrian density increases, more clogging at the exit would be generated and pedestrians would be more difficult to evacuate due to the limited capacity of egress and the reduction in the average speed of pedestrian flow caused by the injured. And the injured with limited motion capacity could hardly complete the evacuation owing to that they need more evacuation time and would retard the speed of the pedestrian flow.     

The excluded-volume effect in microscopic pedestrian simulations

We propose a pedestrian position update rule, which is added to a microscopic pedestrian model to avoid pedestrian overlap. In the rule, the step size of a pedestrian moving in a selected direction at each update is in inverse proportion to the repulsive actions imposed by other pedestrians moving in a direction with an exponential rate. The positions of the pedestrians are then updated in each small time interval. In this way, a barrier between the pedestrians can be generated, and after updating their positions the pedestrians do not overlap with each other. The modified model is compared to the original model through a simulation of the evacuation process of pedestrians in a closed area. The simulation results indicate that the modified model is superior to the original model in several aspects.     

Simulation of pedestrian evacuation based on an improved dynamic parameter model

An improved dynamic parameter model is presented based on cellular automata. The dynamic parameters, including direction parameter, empty parameter, and cognition parameter, are formulated to simplify tactically the process of making decisions for pedestrians. The improved model reflects the judgement of pedestrians on surrounding conditions and the action of choosing or decision. According to the two-dimensional cellular automaton Moore neighborhood we establish the pedestrian moving rule, and carry out corresponding simulations of pedestrian evacuation. The improved model considers the impact of pedestrian density near exits on the evacuation process. Simulated and experimental results demonstrate that the improvement makes sense due to the fact that except for the spatial distance to exits, people also choose an exit according to the pedestrian density around exits. The impact factors α, β, and γ are introduced to describe transition payoff, and their optimal values are determined through simulation. Moreover, the effects of pedestrian distribution, pedestrian density, and the width of exits on the evacuation time are discussed. The optimal exit layout, i.e., the optimal position and width, is offered. The comparison between the simulated results obtained with the improved model and that from a previous model and experiments indicates that the improved model can reproduce experimental results well. Thus, it has great significance for further study, and important instructional meaning for pedestrian evacuation so as to reduce the number of casualties.     

通过博弈的室内行人疏散动力学研究

在室内行人疏散过程中,行人博弈对疏散效率有着重要的影响.本文把抵制博弈策略更新的强度定义为抵制强度. 为了研究抵制强度对疏散效率的影响, 通过在行人博弈策略更新的概率中引入抵制强度,基于元胞自动机模型数值计算在不同的行人密度, 出口宽度下疏散总时间随抵制强度变化的关系.结果表明: 室内行人疏散过程中, 抵制强度小会使得争抢行为极其容易蔓延. 当行人密度小且出口宽大时, 输入以急速疏散为主的规范信息,鼓励行人模仿优胜者更新博弈策略, 当行人密度大且出口狭小时, 输入以避让为主的规范信息抑制行人争抢,都能提高疏散效率. 最后找出不同条件下与最短疏散总时间相对应的优化抵制强度, 为提高室内行人疏散效率提供一个新的视角.     

菱形网格的行人疏散元胞自动机模型

利用改进的层次域元胞自动机模型,研究了正菱形网格空间中的行人疏散问题.这类网格可以避免行人贴近房间墙壁或障碍物,转移概率考虑了各种逃生受阻因素.数值仿真显示,出口处的行人分布与实验快照展示的行人分布基本相同,疏散时间和出口宽度呈线性关系,行人流率接近实验结果.     

Simulation study on cooperation behaviors and crowd dynamics in pedestrian evacuation

Pedestrian evacuation is actually a process of behavioral evolution. Interaction behaviors between pedestrians affect not only the evolution of their cooperation strategy, but also their evacuation paths-scheduling and dynamics features. The existence of interaction behaviors and cooperation evolution is therefore critical for pedestrian evacuation. To address this issue, an extended cellular automaton(CA) evacuation model considering the effects of interaction behaviors and cooperation evolution is proposed here. The influence mechanism of the environment factor and interaction behaviors between neighbors on the decision-making of one pedestrian to path scheduling is focused. Average payoffs interacting with neighbors are used to represent the competitive ability of one pedestrian, aiming to solve the conflicts when more than one pedestrian competes for the same position based on a new method. Influences of interaction behaviors, the panic degree and the conflict cost on the evacuation dynamics and cooperation evolution of pedestrians are discussed. Simulation results of the room evacuation show that the interaction behaviors between pedestrians to a certain extent are beneficial to the evacuation efficiency and the formation of cooperation behaviors as well. The increase of conflict cost prolongs the evacuation time. Panic emotions of pedestrians are bad for cooperation behaviors of the crowd and have complex effects on evacuation time. A new self-organization effect is also presented.     

双出口房间人群疏散的实验研究和数学建模

本文设计了一个双出口房间内人群疏散的实验方案,通过不同条件下疏散过程的实况录像及视频检测,得到不同人数疏散时间的许多定量结果.提出了双出口房间吸引区间的概念,证明了较小出口吸引区间的边界总是一段圆弧,可以解释行人流出口处的圆形成拱现象.通过类比地铁候车厅内人群疏散过程,建立了双出口房间内疏散时间的二次函数模型,成功拟合不同条件下的实测数据.疏散人数较少时,疏散时间随着人数增加而线性增长;人数较多,在出口附近出现待行区域时,疏散时间则呈二次函数增长.与一些已知疏散时间数学模型相比,本文模型对出口宽度变化的反应更敏感.     

Effect of a static pedestrian as an exit obstacle on evacuation

Building exit as a bottleneck structure is the last and the most congested stage in building evacuation. It is well known that obstacles at the exit affect the evacuation process, but few researchers pay attention to the effect of stationary pedestrians (the elderly with slow speed, the injured, and the static evacuation guide) as obstacles at the exit on the evacuation process. This paper explores the influence of the presence of a stationary pedestrian as an obstacle at the exit on the evacuation from experiments and simulations. We use a software, Pathfinder, based on the agent-based model to study the effect of ratios of exit width ($D$) to distance ($d$) between the static pedestrian and the exit, the asymmetric structure by shifting the static pedestrian upward, and types of obstacles on evacuation. Results show that the evacuation time of scenes with a static pedestrian is longer than that of scenes with an obstacle due to the unexpected hindering effect of the static pedestrian. Different ratios of $D/d$ have different effects on evacuation efficiency. Among the five $D/d$ ratios in this paper, the evacuation efficiency is the largest when $d$ is equal to $0.75D$, and the existence of the static pedestrian has a positive impact on evacuation in this condition. The influence of the asymmetric structure of the static pedestrian on evacuation efficiency is affected by $D/d$. This study can provide a theoretical basis for crowd management and evacuation plan near the exit of complex buildings and facilities.     

Agitated behavior and elastic characteristics of pedestrians in an alternative floor field model for pedestrian dynamics

An alternative floor field (FF) model is proposed by incorporating the agitated behavior and elastic characteristics of pedestrians. The agitated behavior which is regarded as an important factor to pedestrian dynamics is depicted by introducing a parameter to revise the transition probability of pedestrians to move to the neighboring cells. To characterize elasticity of pedestrians, it is assumed that a cell can hold more than one pedestrians in crowd condition, while it can hold only one pedestrian in normal condition. In addition, a method to deal with conflicts is employed by considering the effects of agitated behavior and desired velocity. Numerical simulations are carried out to investigate pedestrian evacuation from a room. The results show, that as the value of agitated parameter increases, the evacuation time decreases to the minimum value and then increases gradually. Also, the faster-is-slower effect which is obtained by some other simulation models can be reproduced by the proposed model. Finally, the influence of exit width and the corresponding mechanism on evacuation process is investigated which is expected to be helpful to the exit design of public rooms.     

Simulation of evacuation processes using a multi-grid model for pedestrian dynamics

Introducing the force concept of a social force model into the lattice gas (LG) model, a new LG-based discrete model entitled “multi-grid model” is composed. In the new model, finer lattice is used; thus each pedestrian occupies multiple grids instead of one, and the rules of interactions among pedestrians or pedestrians and constructions are built. The interaction forces including extrusion, repulsion and friction are considered as passive factors for evacuation. The strength of the drift, or the intensity of the pedestrians to move toward the exit rapidly, is considered an active factor. A simple situation is studied in which pedestrians try to evacuate from a large room with only one door. The influences of interaction forces and drift on evacuation time are analyzed. The mutual restriction relation of the two factors in the course of evacuating is found.     

基于教室人群疏散实验的行人流建模和模拟

基于教室人群疏散实验, 从中归纳出疏散过程中行人的基本运动特征. 将桌椅分别视为不可穿越和可穿越的静态障碍物, 而行人则被当成可移动的障碍物, 这将导致背景场随人群的运动而动态更新, 因此可以更好地反映前方拥挤程度对后面人群路径选择行为的影响. 采用基于动态背景场的元胞自动机模型研究了不同桌椅排列和出口宽度的教室人群疏散过程, 给出了疏散时间的空间分布以及平均和最大疏散时间, 再现了实验中人群疏散的基本特征. 数值模拟结果表明, 疏散时间取决于桌椅的排列方式和教室出口的宽度. 对于同一种排列, 出口越小则疏散时间越长; 对于给定的出口宽度, 通常随着过道数的增加, 疏散时间随之减少; 当过道数增加且过道宽度不足以两人并行, 从两侧进入过道的行人会发生冲突, 使疏散效率有所降低; 靠近出口一侧墙壁设置过道有利于人群的疏散. 文中进一步分析了模拟与实验结果存在差异的原因.     

Cellular automaton model for evacuation process with obstacles

A bidimensional cellular automaton model is used to simulate the process of evacuation of pedestrians in a room with fixed obstacles. A floor field is defined so that moving to a cell with lower floor field means approaching an exit door. The model becomes non-deterministic by introducing a “panic” parameter, given by a probability of not moving, and by a random choice to resolve conflicts in the update of pedestrian positions. Two types of exit doors are considered: single (where only one person can pass) and double (two persons can pass simultaneously). For a double door, the longest evacuation time turns out to occur for a very traditional location of the door. The optimum door position is determined. Replacing the double door by two single doors does not improve evacuation times noticeably. On the other hand, for a room without obstacles, a simple scaling law is proposed to model the dependence of evacuation time with the number of persons and exit width. This model fails when obstacles are present, as their presence introduces local bottlenecks whose effect outweighs the benefits of increasing door width beyond a certain threshold.     

Constant evacuation time gap: Experimental study and modeling

In this paper, the evacuation dynamics in an artificial room with only one exit is investigated via experiments and modeling. Two sets of experiments are implemented, in which pedestrians are asked to escape individually. It is found that the average evacuation time gap is essentially constant. To model the evacuation dynamics, an improved social force model is proposed, in which it is assumed that the driving force of a pedestrian cannot be performed when the resultant physical force exceeds a threshold. Simulation results are in good agreement with the experimental ones.     

步行通道内行人流拉链现象的生成机理与仿真研究

以步行通道内的单向行人流为研究对象,分析研究行人拉链现象的生成机理,并建立基于Voronoi图的速度修正模型对其仿真研究.首先,从行人追求视野最佳和步行舒适的角度分析拉链现象的生成机理,以行人的视野关注和视野遮挡描述影响行人移动过程中产生拉链偏移的因素;以行人局部密度描述行人的步行舒适度;引入拉链敏感系数描述行人客观偏移的意愿程度;提出单个行人侧向偏移的机制,获得行人最佳的偏移位置.然后,构建基于Voronoi图的行人速度修正仿真模型,考虑行人是否有偏移倾向的主观意愿,并嵌入偏移规则,模拟再现行人的拉链现象.仿真发现:行人的拉链层数与通道宽度成正比,该模型速度密度关系图与实证数据吻合较好;与不考虑拉链效应相比,倾向主动进行侧向偏移的行人占比越大,越有助于提高通道内行人的移动速度、舒适度和空间利用率.