Research On Trajectory Tracking Algorithm For Intelligent Electric Bus Based On Model Predictive Control

Intelligent vehicle is an important part of the intelligent transportation system.Intelligent electric bus can not only reduce traffic accidents caused by the misuse of the drivers,but also alleviate environmental pollution and relieve traffic congestion problems.Hence,it is significant for the health traffic system by developing the intelligent electric bus vigorously.The two key point technologies for intelligent vehicles are path planning and trajectory tracking.How to quickly and accurately follow the desired trajectory under the known path has been a hot topic,which attracts lots of scholars researching and discussing at home and abroad.Taking the intelligent electric bus as the research object,and establish the vehicle model and model predictive control(MPC)are studied in this paper.The main contents and conclusions of this paper are as follows:Firstly,vehicle kinematics model and vehicle dynamics model are established respectively.And by reasonable assumptions and simplification,a nonlinear vehicle model that can be applied to MPC is obtained.In order to keep the stability of vehicle,the model of vehicle tire is established.At the same time,a small angle hypothesis is put forward,which simplifies the mathematical model and improves the speed of the MPC,which provides a model basis for the following vehicle trajectory tracking control.Combined with the nonlinear model,the nonlinear MPC algorithm and its numerical solution are introduced.However,due to the limitations and computational cost of nonlinear models,a linear time-varying MPC method is introduced.Then,different MPCs are designed in two models,including the design of target function,constraint conditions and feedback mechanism.Co-simulation of Trucksim and MATLAB/Simulink is used to verify the feasibility and effectiveness of the MPC in the intelligent electric bus.From the simulation results,the MPC based on kinematics can only be applied to low speed conditions,while the controller designed based on the dynamic model has good adaptability and robustness to vehicle speed variation,and it can accomplish trajectory following control accurately.Due to overtaking lane change with constant speed cannot reflect the real condition of driver’s overtaking operation,the algorithm of MPC based on dynamics is optimized,which increases the longitudinal acceleration constraints in the controller.From the simulation results,it is found that the control stability of the vehicle becomes better after the longitudinal velocity control is added.Based on Hardware-in-the-Loop(Hi L)simulation technology,a d SPACE HIL test platform for electric bus steering-by-wire is built.Meanwhile,it further verifies the effectiveness of the MPC algorithm.And than,the MPC is applied to FOTON-12 m-pure-electric bus,and the real vehicle test is carried out.The results show that the proposed control algorithm has good trajectory tracking control.