Research On Dynamic Evolution Mechanism Based On Pedestrian Collective Motion

The distributional characteristic of pedestrian flow is a key issue in the study of pedestrian dynamics.The description of collective motions becomes difficult due to the coupling of the differences in walking habits of pedestrians and the interaction of pedestrians in the group.However,the macroscopic collective motion characteristics of crowds and the individual micro-behavioral habits have important practical significance of the management of mass passenger flow,as well as the design of evacuation strategy.Therefore,the collective motion behavior of crowds had been discussed through this paper.The research methods of this paper include controlled experiment and computer simulation.We extracted some characteristic parameters to make a study of the distributional characteristic of pedestrian flow in experiments from micro view and macro view.At first,we took an observation experiment in front of the security check in subway station.It is observed that there is the correlation between the queue width of queuing processes and the arrival rate of passengers.We called the phenomenon that the increasing of queue width as queue-splitting.Then,the queuing behavior of pedestrian had been researched by social force model.This paper considerd that there were four states in the queuing processes for each person:freely walking(FW);queue-searching(QS);waiting in queue(WQ);being served(BS).The change of state for pedestrian were achieved by environmental perception mechanism.According to the above,the reason for the increasing of queue width is because several arrivals follow the same person when arriving one after the other at short intervals.An important state parameter which is called average queue width(AQW)for pedestrian was proposed by the leadership among pedestrian to define the distributional characteristic of pedestrian flow.The variation trend of AQW under different inflow and different reaction time were found in the result of computer simulation modeling.It played a key role in AQW that the difference in time interval when individual pedestrians arrive at the last of the queue.Queue-spliting mainly occurs in the process of QS.In addition,the result indicated that it positivily correlated with the pedestrian inflow and reaction time,which means the decrease of reaction time made the distribution of pedestrian more gathered,and the AQW increased with pedestrain inflow.There were four phase transition points which took the influence of AQW by the pedestrian inflow:1.6 per/s,2.2 per/s,2.9 per/s,4.0 per/s.Collective motion in pedestrian crowds is also a part of collective animal behavior.It is a pity that so far there was no universally valid method for describing the distribution law of pedestrian collective motion.This paper built a fundamental linear relationship about the pedestrian distribution based on the previously behavioral study.That proposed a method in quantitative depiction of the distribution characteristics of collective motion in human crowds,and drew a curve of characteristics of dynamical crowd distribution(CDCD).Then we validated that fundamental linear relationship by the controlled pedestrian experiments in three different aspects:environmental differences,gender differences and the individual size differences.The experimental results demonstrated that CDCD can not only depict the unity of pedestrian collective motions,but the difference in different conditions.According to the proposed parametric description,we found some existing spontaneous crowd behavior in pedestrian movement such like“natural broadening”effect and“bottleneck broadening”effect.Those collective effects explained the crowd management measures successfully which were taken in the international Marathon.In addition,this method is not limited to a specific research object,and it is also applicable to the directed cluster motion process of any object in a two-dimensional planar environment.Such as traffic flow,ant colony movement,etc.We found that the fluctuation of pedestrian order was greater in when the confined space had just a few pedestrian.That is because the differences in individual walking habits would be amplified with the low density,which could not be accurately representated in the existing pedestrian dynamic models(such as in social force model).This difference mainly reflects in two individual aspects of linear and turning movement.Therefore,we conducted an individual walking experiment in different physical environments to cover the shortage of the evolution mechanism simulation for turning behavior in social force model.This study discussed the difference between the pedestrian's individually linear and turning movement in two aspects of velocity and angle velocity.A dynamical parameter which wass called turning scale was proposed to describe the characteristic of turning behavior based on the dynamical analysis of self-driven force.The calculation result indicated that the pedestrian tend to assign more self-driven force to turning when the turning radius is small.The research results presented in this work can be applied to the development and validation of the social force model.