Research On Multi-objecitve Optimization Of The Pedestrian Evacuation In Stadium Based On Partitioned Network

Different evacuation scenarios possess different evacuation features. The features of evacuation scenarios, such as the exits positions, the inner structure, and so on, have important influences on evacuation process. Evacuation modeling according to the features of evacuation scenarios facilitates the improvement of evacuation plans performances. The stadium assumes approximate ring form, bleachers distribute around inner ring, multiple exits distribute around outer ring, bleachers and exits partitionedly correspond to each other. This kind of structure determines the pedestrian evacuation in stadium possesses special features that the evacuees move from bleachers areas around the inner ring to the exits around the outer ring. Nowadays, the pedestrian evacuation planning in stadium could be divided into two sorts:the simiulation-based evacuation planning and the optimization-based evacuation planning. Most of researches on optimization-based evacuation planning in stadium were single objective optimization or transforming multi-objective optimization to single objective optimization. Only a few multi-objective optimization based evacuation planning researches were based on the multi-objective optimization theory. The multi-objective optimization theory based evacuation planning usually adopted general multi-objetive optimization algorithm. Merely a few multi-objective optimization theory based evacuation planning researches were based on the features of stadium to design the special multi-objetive optimization algorithm. The general multi-objetive optimization algorithms use pseudo-random proportional processes to search the evacuation routes. As lacking the guidance of domain knowledge, the general multi-objetive optimization algorithms are apt to result in blind searching. The special multi-objetive optimization algorithms resort to the domain knowledge which lead to purposeful searching could reduce the range of searching, thus it is easier to find out the evacuation routes plans with higher evaucaiton efficiency and performances than the general multi-objetive optimization algorithms. Therefore, for raising the evacuation efficiency and improving the performance of evacuation plans, the multi-objective evacuation routes planning problem based on the features of pedestrian evacuation in stadium is an urgent problem to tackle. For solving this problem, some innovative works were done in this paper:l)For raising evacuation efficiency and improving evacuation performances, according to the topology structure features that the bleachers and exits partitionedly correspond to each other, the stadium was abstracted as a partitioned network. The stadium features based partitioned network pedestrian evacuation model was established. Based on this model, the partitioned multi-objective evacuation routes optimization algorithm was presented.The stadium shows approximate ring form, bleachers distribute around inner ring, multiple exits distribute around outer ring, bleachers and exits partitionedly correspond to each other. On account of this kind of structure features, the stadium was abstracted as a partitioned network, which is used to guide the evacuation process of evacuees. Guided by this network, each evacuee can merely evacuate from the exits in which partition he sit, avoiding the emergence of longer cross-partitioned evacuation route. This facilitate to shorten the length of evacuation route and raise evacuation efficiency. Based on the partitioned network, the stadium features based partitioned network pedestrian evacuation model was constructed. This model takes three optimization objectives into consideration, namely, the network clearence time, the total routes length and the cumulative congestion degrees. Based on this model, the partitioned multi-objective evacuation routes optimization algorithm was proposed.The numerical experiments indicate that, compared with hierarchical multi-objective evacuation routing problem algorithm, the partitioned multi-objective evacuation routes optimization algorithm possess higher evacuation efficiency and better convergence of non-dominated solutions set. However, compared with the hierarchical multi-objective evacuation routing problem algorithm, the congestion situation of the evacuation solutions derived from the partitioned multi-objective evacuation routes optimization algorithm is worse.2)For improving congestion situation and further raising evacuation efficiency, the priority Pareto partial order relation and the vector pheromone routing method based on it were proposed.The priority Pareto partial order relation based vector pheromone routing method give priority to the factors which is closely related with evacuation performances, including evacuation efficiency and congestion situation, so as to get rid of interference of the secondary factors. Thus, it could effectively improve the evacuation performances, such as efficiency, congestion situation and so on. For improving the congestion situation of the solutions derived from the partitioned multi-objective evacuation routes optimization algorithm, the priority Pareto partial order relation based vector pheromone routing method was proposed in this paper to replace the traditional Pareto partial order relation based vector pheromone routing method in the partitioned multi-objective evacuation routes optimization algorithm.The factors affected the routing in probability transition function in the routing method of traditional ACO algorithm should be mutually independent. However, in evacuation process, the factors affected the routing are not always mutually independent. For fully considering the factors affecting the routing, this paper adopts the traditional Pareto partial order relation based vector pheromone routing method to replace traditional ACO algorithm routing method. The traditional Pareto partial order relation based vector pheromone routing method considers all the affecting factors have the same influence on the evacuation performances, such as evacuation efficiency, congestion situation and so on. However, actually, some of the affecting factors, such as the distance to the exit and the distance to the center of stadium, have larger influence than other factors. Thus, the priority Pareto partial order relation was presented in this paper. And based on the priority Pareto partial order relation, the priority Pareto partial order relation based vector pheromone routing method was proposed. Compared with the traditional Pareto partial order relation based vector pheromone routing method, the priority Pareto partial order relation based vector pheromone routing method give priority to the factors which is closely related with evacuation performances, including evacuation efficiency and congestion situation, so as to get rid of interference of the secondary factors. Thus, it could effectively improve the evacuation performances, such as efficiency, congestion situation and so on. However, the diversity of the non-dominated solutions derived from the partitioned multi-objective evacuation routes optimization algorithm with the priority Pareto partial order relation based vector pheromone routing method is worse than the partitioned multi-objective evacuation routes optimization algorithm with the traditional Pareto partial order relation based vector pheromone routing method. 3)For raising evacuation efficiency and improving congestion situation as well as raising diversity of non-dominated solutions set, the population pheromone updating strategy was proposed.The population pheromone updating strategy makes the pheromone on each edge varies to different directions. Compared with the traditional pheromone updating strategy, the population pheromone updating strategy makes the pheromone updating more diversified, thus improve the diversity of the non-dominated solutions. For improving the diversity of the non-dominated solutions derived from the partitioned multi-objective evacuation routes optimization algorithm with the priority Pareto partial order relation based vector pheromone routing method, the population pheromone updating strategy was proposed to replace the traditional pheromone updating strategy in this algorithm.The numerical experiments show that, the partitioned multi-objective evacuation routes optimization algorithm with the priority Pareto partial order relation based vector pheromone routing method which employs the population pheromone updating strategy possess better diversity. As well as, evacuation efficiency and congestion situation is the same as using traditional pheromone updating strategy. And, the convergence of non-dominated solutions set is better than the algorithm using traditional pheromone updating strategy.