| Not only does the automobile adaptive cruise control (ACC) system have the function of traditional cruise control, but also keep the safety distance between ACC vehicle and front vehicle. It can monitor the front traffic environment by on-board radar. When other vehicles are found in the front of its lane, the control order of throttle or braking will be sent to the ACC vehicle to keep the safety distance based on the relative distance and velocity between the ACC vehicle and front vehicle. Meanwhile reducing the driver's task, saving fuel consumption and reducing the pollution, it can improve driving safety in the highway further.Based on the former decision and correction control algorithm of ACC system, the fuzzy control algorithm of ACC system was presented to solve the problem of the strong nonlinear of high-speed vehicle dynamics with the advantage of fuzzy system solving nonlinear problem. Meanwhile the adaptive fuzzy PID control algorithm was studied based on the classic fuzzy controller, which showed good dynamic and static performance under the change of driving environment. Finally the improving effect on fuel economy and the emission of CO, HC and NOx by different control algorithm was assessed quantitatively.1. A vehicle dynamic model was established by the software of AVL/CRUISE. In this model, the longitudinal dynamic assembly included engine, torque converter, auto gearbox, driving system and vehicle system. First different part of power-train were modeling. Then the assembly was linked with torque and speed. Finally the whole model of vehicle longitudinal dynamic system was gotten.2. The former decision algorithm was analyzed in detail. Then the fuzzy control system was brought into the correction control model, and the classic fuzzy controller of ACC system was established.3. Though classic fuzzy controller can solve the nonlinear problems effectively, it is too difficult to achieve good dynamic and steady performance because of fixed parameters and fixed fuzzy rules. So based on the classic fuzzy controller, an adaptive fuzzy PID control algorithm was studied. The adaptive fuzzy PID controller combined the classic fuzzy controller with PID controller. According to the relationship between the parameters of PID and input variables, the adaptive fuzzy PID controller adjusted the parameters of PID online in order to satisfy the requirements of the controlled object, and showed good adaptability to different conditions. Finally, the control algorithm was combined with the vehicle longitudinal dynamic model by the software of AVL/CRUISE and the ACC typical condition was simulated to prove the validity and effectivity.4. The principal maps of combustion and emission were used to simulate the emission model with the software of AVL/CRUISE. The former classic fuzzy controller and adaptive fuzzy PID controller were combined with vehicle longitudinal dynamic mode, some ACC typical condition were simulated, and the influence on emission and fuel economy of different control algorithm were evaluated. |
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