Research On Intelligent Vehicle Obstacle Avoidance Path Planning Based On Direct Collocation Method

With the rapid increase of car ownership,the problems of traffic safety,road congestion and parking space shortage are gradually exposed.Research on intelligent vehicles is an effective way to solve the above problems.Obstacle avoidance path planning is the key part of intelligent vehicle technology,which has great research significance and application prospect.In the process of vehicle driving,the road environment is complex and uncertain.At the same time,it is necessary to meet the constraints of the vehicle itself to make the path planning difficult.How to find the optimal path that meets the actual needs of intelligent vehicles is the most difficult point of path planning.The traditional local path planning algorithm is easy to fall into the local optimum,the path is not reachable,the obstacle avoidance model is complex,which leads to a large amount of calculation.Based on the vehicle dynamics model,according to the characteristics of vehicle motion,this paper describes the road model of intelligent vehicle on the straight road.In this paper,an obstacle modeling method based on the head circle and the tail circle is proposed,and the optimal control model of local path planning is established.The direct collocation method is used to study the path planning of intelligent vehicle lane changing.The direct collocation method approximates the state variables and control variables in time and space by fitting polynomials,and obtains the first derivative of polynomials to approximate the state differential quantities at discrete points,thus transforming the optimal control problem into a nonlinear programming problem(NLP).The direct collocation method avoids the tedious theoretical derivation process of indirect analytical method and has faster calculation efficiency.Taking the typical working condition of the intelligent vehicle overtaking to avoid the anchor car as an example,the trajectory optimization scheme is solved by the combination of the direct collocation method and the sequential quadratic programming method.The simulation results show the ability of solving path planning based on direct collocation method.The conditions of intelligent vehicle overtaking and lane changing after avoiding staticobstacles and returning to the original lane,including avoiding anchored cars and buses,and avoiding low-speed moving obstacles,are expanded and studied.The path planning can be successfully realized by using the direct collocation method.The direct collocation method can determine the optimal path of the vehicle in the driving process,and can solve the problem of obstacle avoidance among various types of obstacles.It has good real-time performance and little delay.The difference of overtaking and lane changing of intelligent vehicle to avoid low-speed vehicle and anchor vehicle is analyzed,which shows the necessity of differential treatment.And the four conditions of intelligent vehicle obstacle avoidance path planning are compared and analyzed.The solution time of the four conditions is less than1.5 seconds.It shows that the direct collocation method is an effective discrete method to solve the optimal control problem.The direct collocation method has the advantages of small calculation and good numerical stability in solving the optimal control problem.