The Research Of VFH Path Planning Algorithm Based On Environment Complexity Model

Automobile has brought much convenience to people’s lives since its advent,but many problems arising with its advent such as traffic accidents,environment pollution also troubled people a lot.To solve this problem,people put forward the concept of Intelligent Transportation,using advanced communication,control,computer,AI and other technologies to construct the Intelligent Transportation System,which has become a powerful way to solve these problems and improve efficiency of transportation.Intelligent Driving is an important part of ITS,it is also the main impetus of future development of ITS.Intelligent Driving has been developed for a long time.One of the most important parts of Intelligent Driving is path planning,it can be divided into global path planning and local path planning depending on the amount of information obtained about surroundings.Many algorithms have been produced in the development course of path planning,among which vector field histogram(VFH)is an algorithm with good stability and has been studied for a long time.Many scholars have done a lot of research on it and improved VFH a lot.Our research is also based on this algorithm,and we studied and analyzed the CV(Certainty Values)of this algorithm.Owing to the sensitivity of thresholds,we used self-adapting threshold in the algorithm based on the study of dynamic thresholds,in the process of projecting we traversed from maximum to minimum of thresholds,and selected the best one to determine the best direction for next move,which is the way we used to optimize the algorithm.Most application scenarios of VFH are static environments,however,it is not complete enough to achieve real Intelligent Driving.Under the national conditions like our country,it is very necessary to study the path planning of dynamic environment.After studying the influence of environment,we proposed to construct the dynamic environment complexity model in consideration of these factors: static obstacles,dynamic obstacles,the valleys of polar histogram and the rate of environment changing,finally,we calculated the value of environment complexity by use of these factors.The weight coefficients of all factors we considered are determined by the method called Analytic Hierarchy Process(AHP),which combined the advantages of human subjective experience and quantitative calculation,so as to make the weight coefficients more objective.After the environment complexity model was constructed,we began the path planning in dynamic environment.After introducing dynamic obstacles,we analyzed the impact of key variables and adjusted the key variables dynamically in process of path planning to make it more reasonable.Based on the value of environment complexity and analysis of factors in environment,we used the Fuzzy logic method to adjust these variables dynamically: velocity of vehicle,view size and the bound of threshold traversal,improved the safety of path planning process.Finally we simulated the algorithm through Matlab,analyzed the change and impact of these variables under the influence of environment complexity model and confirmed the rationality of dynamic adjustment.