Trajectory Planning And Control Method Of Tractor-Trailer System In Obstacle Avoidance Scenarios

Tractor-Trailer system is a kind of modular multi-body robot composed of tractor and trailer,which has the advantages of large cargo capacity,flexible mechanism and variable number of sections,so it is widely used in baggage transportation,material transmission,military reconnaissance and other aspects.However,in practical application,Tractor-Trailer system is inevitably affected by the surrounding obstacles.In view of this,this paper is devoted to solving the obstacle avoidance control problem of Tractor-Trailer system and improving the environmental adaptability.The details are as follows:Firstly,the high-precision mathematical model of Tractor-Trailer system is established,which lays the foundation for the subsequent controller design.Tractor-Trailer system is a kind of special multi-body mechanical system.Due to the connection structure between tractor and trailer,it has different motion mechanism when moving forward and backward.Therefore,the kinematics models are derived respectively for these two conditions.Then the dynamic modeling of the system was completed based on Euler-Lagrange theorem.Secondly,a obstacle avoidance control strategy based on polynomial theory is proposed to realize the dynamic coordinated obstacle avoidance of Tractor-Trailer system under the structured road.For the sake of safety,comfort and traffic efficiency,two types of obstacle avoidance trajectories are planned by using quintic polynomial function.In addition,because collision risk is highly related to the obstacle avoidance time and distance,the cost function is designed to optimize these two indexes.Then,based on the model predictive control,a posture controller is designed to realize accurate tracking of obstacle avoidance trajectory.Thirdly,considering that in the complex multi-obstacle environment,it is impossible to obtain satisfactory obstacle avoidance effect by only relying on a single form of trajectory.Therefore,the artificial potential field algorithm is introduced to further improve the obstacle avoidance ability of the system.Aiming at the problem of unreachable target point and local minimum in the traditional artificial potential field,a solution is proposed to improve the planning effect of the algorithm.In addition,because the calculation of the model predictive control algorithm used in Chapter 3 is very large,it focuses on theoretical exploration,but it is still difficult in practical application.Therefore,this chapter designs a trajectory tracking controller based on linear quadratic regulator.Lastly,by adding the relative velocity factors between Tractor-Trailer system,the target point and the obstacle into the gravitational potential field function and repulsion potential field function,the obstacle avoidance can be realized in the complex environment with mixed dynamic and static obstacles.In addition,in view of the variability of driving environment,the control accuracy is required to be higher.Therefore,a double closed-loop control strategy is designed to realize the position / force coordinated tracking control,so as to improve the robustness of the system.S-function is compiled,Simulink model is built,software simulation and parameter debugging are carried out in Matlab environment.Simulation results verify the effectiveness of the proposed obstacle avoidance control method.The research results of this paper can significantly improve the obstacle avoidance ability of Tractor-Trailer system,and also provide theoretical basis and reference significance for the articulated vehicle.