粒子群优化线控转向变角传动比模糊控制器设计

Design of the fuzzy controller for variable angle transmission ratio of steer-by-wire system through particle swarm optimization

为了提高汽车低速时的转向轻便性与高速时的转向稳定性,设计了一种线控转向变角传动比粒子群模糊控制器。采用线控转向系统可变传动比的特性,利用模糊控制将方向盘转角和车速进行模糊处理,输出精确的传动比,同时根据粒子群算法思想,提出一种粒子群算法优化模糊控制算法。设计仿真控制器,将模糊控制与粒子群算法相结合,通过低速和高速的双移线仿真工况,以及角阶跃仿真工况进行联合仿真控制系统研究。结果表明:粒子群优化模糊控制所设计的变角传动比相比于定传动比和未优化的模糊控制器,能够更好地实现汽车低速转向灵敏和高速转向的稳定性,减轻了驾驶员的疲劳程度,提高了汽车的操纵稳定性和行驶安全性。

In order to improve steering portability at a low speed and steering stability at a high speed of a smart vehicle,this paper designs a fuzzy controller for variable angle transmission ratio of steer-by-wire system through particle swarm optimization.Based on the characteristics of variable angle transmission ratio of steer-by-wire system,angle of the steering wheel and vehicle speed are fuzzy processed by fuzzy control.With an accurate transmission ratio as the output,at the same time,a fuzzy control algorithm is proposed according to the idea of the particle swarm optimization algorithm.Aiming at the shortcomings of the fuzzy control design of variable angle transmission ratio,and combined with the global optimization ability of particle swarm,the particle swarm fuzzy controller is applied to the automotive steer-by-wire system to optimize the control effect,which solves the repeated debugging of the fuzzy controller design and the limitation of the designer’s experience.The simulation controller is designed to combine the fuzzy control algorithm and the particle swarm optimization algorithm,and the co-simulation control system is studied under simulation working conditions of double line shifting both at low and high speeds,as well as under simulation working conditions of angular step at a high speed of the smart vehicle.The results of this study show that,in double line shifting,when the vehicle is running at a low speed,the steering wheel angle of the variable angle transmission ratio designed by the particle swarm fuzzy controller is obviously smaller than that of the fixed angle transmission ratio or by a non-optimized fuzzy controller.Moreover,the peak values of yaw rate and side slip angle are slightly smaller than under the two above mentioned conditions,indicating that the designed variable angle transmission ratio meets the portability of steering when the vehicle is running at a low speed.When the vehicle is running at a high speed,the steering wheel angle of the variable angle transmission ratio designed by the particle swarm fuzzy controller is larger than that of the fixed angle transmission ratio or by a non-optimized fuzzy controller,and the maximum values of yaw rate and centroid side slip angle are also slightly smaller.It can be seen that the control effect of the particle swarm fuzzy controller is better than under the other two conditions,so that the vehicle can maintain a better driving stability.At the same time,under the angular step simulation condition,the overshoot and steady-state values of the yaw rate and the side slip angle controlled by the particle swarm fuzzy controller are smaller than under the other two conditions,which shows that the control effect of the particle swarm fuzzy controller is better.To sum up,compared with the fixed angle or non-optimized fuzzy controller,the variable angle transmission ratio designed by the particle swarm optimization fuzzy control can better realize the sensitivity of a low speed steering and the stability of a high speed steering,reduce the fatigue of the driver,and improve handling stability and driving safety of the vehicle.