Research On Vehicle Adaptive Cruise Control Strategy Based On MPC

As an important part of advanced driver assistance system,the vehicle adaptive cruise system can effectively improve driving safety,occupant comfort and fuel economy.In the basic composition of adaptive cruise system,the controller belongs to the core part of the ACC system,in which the control strategy and algorithm are designed and embedded,and the vehicle state information is feedback to the information sensing unit after control strategy is implemented in the execution unit.Based on the research funded by the National Key R&D Program of China(2018YFB1600701): Development and application of new multifunctional intelligent vehicle terminal,this paper studies the control strategy according to the basic principles of adaptive cruise system,including the following research contents:(1)Aiming at the working mode of adaptive cruise system,it is divided into speed control mode and distance control mode;Based on Constant Time Headway algorithm,a safe distance model is established considering the lateral and longitudinal motion of the front and rear vehicles,which satisfies the nonlinear characteristics of the vehicle during driving;In view of the diversity of road driving conditions,the sub-mode of distance control is divided in detail,considering two classification standards of collision time and vehicle spacing error.(2)Hierarchical control is selected as the the control architecture of the ACC controller;The vehicle inverse longitudinal dynamics model is established including the inverse model of the engine,brake and transmission,and the conversion relationship between the desired acceleration and the throttle opening and the brake master cylinder pressure is obtained;The traditional PID control algorithm is improved,and the integral separation PID control algorithm is used to design the lower controller to prevent frequent switching of the actuators near the critical acceleration.(3)The upper controller is designed based on the model predictive control theory.A state space equation reflecting the relative motion of the front and rear vehicles is established,which is linearized and discretized;A cost function is established,which meets the requirements for tracking and comfort,and considering the physical limitations of the vehicle itself,the combination of hard and soft constraints is used to control the vehicle spacing error,relative speed and desired acceleration within a reasonable range.In the end,the constrained optimization problem is transformed into an online solution sequence quadratic programming problem.(4)The upper controller and the lower controller model are built under the MATLAB/Simulink simulation platform,and the simulation environment is defined in the Carsim,through setting up six typical front vehicle driving conditions;Through the joint simulation of the two,The pros and cons of the ACC controller are verified and analyzed.