Research On Simulation Of Pedestrian Flow Evacuation Based On Improved Social Force Model

With the growing of the global population and the accelerating of urbanization process,there has been a great deal of crowd accidents in the past twenty years.Previous studies have shown that the main cause of crowd accidents is the poor design and management of pedestrian facilities.How to improve the design and management of pedestrian facilities scientifically and effectively,how to ensure safety,efficiency and comfort of pedestrian in a variety of complex traffic environment,has become an urgent problem to be solved.The study on pedestrian evacuation simulation and the reproduction of pedestrian movement can effectively support the construction of pedestrian facilities and the optimization of the management scheme.The individual behavior decision-making mechanism of pedestrians,the mechanisms of interactions among pedestrians,the phase transition law of pedestrian flow and relevant threshold value can be obtained by simulation analysis.Using the information above,the limitations of the traditional data analysis experience can be made up,reasonable design of pedestrian facilities can be promoted,organization and management level of pedestrian assembly can be improved,and warning and handling capability of pedestrian crowd accidents can be strengthened,and then the scientific management theory of pedestrian flow can be constructed.Based on the research on characteristics of pedestrian behavior,microscopic modeling method of pedestrian flow and simulation experiment design method,taking the pedestrian's individual behavior,group consciousness and the psychological state in emergency conditions as the breakthrough point,the modeling and simulation analysis of the pedestrian flow in the channel and the evacuation in the room are carried out based on the social force model.Then the pedestrian behavior factors and guidance methods that affect the evacuation efficiency in the room and in the channel are studied.Through the application of the research results,a microscopic simulation experiment platform of pedestrian flow is established.Specific research contents are as follows:(1)Research on the theory of pedestrian flow simulationThe development of research on pedestrian flow is reviewed: from the early research that confined to "Field Investigation",to establishment of pedestrian flow forecasting model,to invention of pedestrian flow simulation software,the main results of each phase are introduced.And the advantages and disadvantages of the macro,mesoscopic and micro pedestrian flow simulation models are analyzed.And then this paper establishes the thinking of carrying out the simulation of pedestrian flow from the micro level.Experiences of several typical researches on pedestrian flow simulation are summarized,and the breakthrough points,research route and technical means of these studies are analyzed,and the shortcomings of existing research are pointed out.Finally,the design principle and parameter value of the social force model are emphatically analyzed,and the advantages and disadvantages of the social force model and the improvement methods are discussed.(2)Microscopic simulation of counter flow in a channelA microscopic simulation model reflecting the moving preferences of pedestrians during collision avoidance is established.Through the controllable experiment of counter flow's collision avoidance,the factors that influence the choice of pedestrians' orientation are analyzed.The empirical data shows that the relative distance between pedestrians can meet the right tendency in certain conditions.Based on this conclusion,on the basis of the social force model,a new dynamic model reflecting pedestrians' movement tendency is proposed,in which the factors just as search range of pedestrian collision avoidance and relative distance between pedestrians are taken.The evacuation process of counter flow is simulated using the improved model,which finds that: the social force model considering pedestrian's right preferences can make up for the problems which the original social force model caused in the simulation process,and make the collision avoidance time and pedestrian trajectory closer to reality;the moving preferences of pedestrian impacts the canalization phenomenon of counter flow,if the pedestrian movement has the same preferences,it is conducive to the formation of pedestrian flow self-organization phenomenon,and it can also reduce the frequency of conflicts of counter flow and improve the efficiency in the channel.The follower behavior caused in counter flow is studied.Based on the social force model,a new dynamic model for simulating pedestrian following behavior is proposed.The new mechanical model takes into account the factors just as search range of pedestrians' following behavior,the state of self motion,and the motion state of pedestrians in front,and analyzes the conditions of generation and stop of following behavior.In the simulation experiment,the influence of pedestrians' following behavior on lane-formation of counter flow and traffic efficiency is studied by using the improved social force model.It is found that: the following behavior can promote the formation of lane-formation phenomenon,and relieve congestion of pedestrians;following behavior can reduce the frequency of conflicts of counter flow,improve the efficiency of duplex channel.(3)The microscopic simulation of pedestrian evacuation in a roomAn improved social force model is proposed to simulate the evacuation process in a smoky room.The model takes into account the influence of the wall,ground evacuation sign,wall evacuation sign and the exit on herding behavior,moving direction and expected speed on the process of evacuation.The model is also used to simulate the evacuation process under the guidance of the evacuation sign of the ground and the evacuation sign of the wall.The influence of two kinds of evacuation signs on evacuation is analyzed in three aspects: guiding the direction of escape,reducing the will of following and increasing the expected speed.And then the two kinds of evacuation signs layout from the evacuation efficiency and safety risk is compared,the results showed that evacuation efficiency of ground evacuation sign is higher compared with wall evacuation sign,but at the same time,the security risk is greater.In addition,the combination scheme of two evacuation signs are studied,the results show that,if the wall evacuation sign and the ground evacuation sign can be properly assembled and arranged,the evacuation efficiency of the wall evacuation sign layout scheme can be improved,and the risk of congestion accident of the ground evacuation sign layout scheme can be reduced.But when the combination scheme is designed,ground evacuation signs must be placed according to the actual characteristics of the evacuation environment in the appropriate area,if the area placed ground evacuation signs is too large,the purpose of the combination layout scheme will be not achieved,the evacuation effect will be close to the layout scheme that there are ground evacuation signs only.(4)The establishment of micro simulation experiment platform for pedestrian flowOn the basis of micro simulation model,combined with computer programming technology and multi-agent modeling theory,a microscopic simulation platform for pedestrian flow is built.The platform is divided into three modules: walking space modeling module,pedestrian movement simulation module and pedestrian movement data extraction module.In walking space modeling module,CAD drawings of pedestrian facilities can be imported,traffic facilities and regional modeling and walking streamlines can be restored.In pedestrian movement simulation module,the setting function of pedestrians' related attributes is implemented,several microscopic simulation models corresponding to different regions or facilities are encapsulated,and pedestrian Agent identification of congestion,visibility,facilities,or areas in walking space is achieved,according to which information the applicable micro simulation model can switch automatically,and also,the two-dimensional visualization process of pedestrians' movement is realized by combining Open GL image programming technology.In the data extraction module,it can extract pedestrians' movement data just as average speed,average density,flow rate and average occupancy space in the evacuation process in real time.The main innovations are as follows:(1)The asymmetry of pedestrian following is quantified in the first time.The asymmetry derives from the range of pedestrians,the similarity of the direction of the pedestrians,and the limitation of the current state of the pedestrian.The numerical results show that the asymmetrical model can more accurately reflect and predict the pedestrian following behavior.(2)A controllable experimental design method for obtaining the motion preferences data during pedestrian collision avoidance is designed.Based on the data obtained from the experiment,a new mechanical model is established considering the influence of the relative position of pedestrians on the pedestrian movement tendency.The model can more accurately reflect the dynamic changes and channelization characteristics of the current flow(3)On the basis of the traditional social force model,the influence of the relative position of pedestrians on the pedestrian movement preference is considered,and a new mechanical model is established.The model can more accurately reflect the dynamic changes and channelization of the current flow(4)A micro flow simulation platform for pedestrian flow is constructed,which can accurately restore the functional characteristics of various transportation facilities,walk the streamline and conduct intelligent switching of multiple sets of microscopic simulation models according to the walking environment information.