关键词: 车辆工程；智能电动车；自适应巡航；可变车间时距策略；线性二次型最优控制；分数阶PID控制

Abstract: Aiming at the problem of poor tracking of electric vehicles caused by frequent shifts of the preceding vehicle, an adaptive cruise control system based on hierarchical control was established. Firstly, considering the influence of the acceleration and deceleration changes of the preceding vehicle, the variable headway strategy was adopted as the expected safe vehicle distance, and the polynomial fitting method was used to analyze the influence of different vehicle time interval on the feedback gain matrix of the linear quadratic optimal control algorithm and build an upper-level controller based on improved linear quadratic optimal control. Then, the fractional PID control theory was applied to establish the lower controller to accurately track the expected driving torque and braking pressure, and genetic optimization algorithm was used to optimize and adjust the fractional PID parameters. The research shows that the adaptive cruise controller based on hierarchical control can ensure the safety and comfort of the vehicle, which has good adaptability to the frequent acceleration and deceleration conditions of the preceding vehicle and has good tracking performance.

Key words: vehicle engineering; intelligent electric vehicle; adaptive cruise control; variable headway strategy; linear quadratic optimal control; fractional order PID control