Obstacle Avoidance Path Planning For UAV Based On Improved RRT~* Algorithm

Obstacle avoidance path planning capability,as one of the key capabilities of UAV to achieve safe autonomous flight,has always been a hot research topic in UAV research filed.As a commonly used obstacle avoidance path planning algorithm,RRT~* algorithm can carry out obstacle avoidance path planning in real time and online,and can obtain the obstacle avoidance path with asymptotically optimal performance while ensuring the probabilistic completeness.Since the RRT~* algorithm adds the process of path optimization,the convergence rate of the algorithm decreases.In order to make up for this shortcoming of RRT~* algorithm,this paper proposes an improved RRT~* algorithm based on heuristic function for bias sampling to speed up the convergence of the algorithm.The research and application of the improved algorithm for obstacle avoidance path planning of UAV are studied.The main contents of this paper are as follows:1.The obstacle avoidance path planning problem of UAV is analyzed and described,and the model related to the problem is established.Firstly,the problem of UAV obstacle avoidance path planning is analyzed.In order to facilitate the research,the problem is described by mathematical language.Then the motion model of UAV is established.Finally,according to the different characteristics of the common threat sources of UAV in the war environment,the threats are divided into two categories: environmental threat and air defense system threat,and the main threat sources in the two categories are analyzed and modeled.2.Based on the analysis of the traditional RRT~* algorithm,an improved RRT~* algorithm is proposed,and the improved RRT~* algorithm is applied in the two-dimensional space for the obstacle avoidance path planning of the UAV.Firstly,explained the principle of RRT algorithm which is the origin of RRT~* algorithm,and pointed out it's advantages and disadvantages and improvement directions.Then illustrated the principle,advantages and disadvantages and improvement directions of RRT~* algorithm.Finally,an improved RRT~* algorithm based on heuristic function for bias sampling is proposed for the shortcoming of RRT~* algorithm.The feasibility and superiority of the algorithm are verified by simulation experiments in two-dimensional space.Considering that different thresholds for biased sampling will have an impact on the path planning effect of the improved RRT~* algorithm,experiments are carried out for different thresholds.The experimental results show that when the partial sampling thresholds is set at 0.5,the improved RRT~* algorithm has the best effect on obstacle avoidance path planning of uav in two-dimensional space.3.Because UAV is maneuvering in three-dimensional space,in order to observe the performance of the improved RRT~* algorithm more realistically and intuitively,the heuristic function in the improved RRT~* algorithm is extended and adjusted.Then the algorithm is applied to the obstacle avoidance path planning of UAV in three-dimensional space.The simulation experiment verifies the feasibility and superiority of the improved RRT~* algorithm in obstacle avoidance path planning of UAV in three-dimensional space.