Analysis Of Yaw Stability Of Small Scale Electric Vehicle Based On Human-machine Dynamics Coupling Effect

The miniature electric vehicle, with advantages of small size, light weight, simple structure, low manufacture costs, energy saving, environment protection, and so on, will be an ideal transportation to alleviate the city congestion, environmental pollution and energy crisis in the future. The small scale electric vehicle, which concentrates the miniaturization, light weight and electric, has advantages in energy conservation and environmental protection.With the development of society and the advancement of technology, vehicle driving safety has attracted more and more attention, while the driving safety is closely related to the vehicle handling and stability. This is because that after miniaturization, the longitudinal and horizontal dimensions of vehicle body have been greatly reduced compared with the traditional vehicle and the dynamics coupling effect between the body and vehicle is evident, resulting in the mechanical properties of the human body, the change of on attitude and behavior will have important influence on the dynamics stability of the vehicle. Therefore, as to yaw dynamic, it should and must consider the human-machine dynamic coupling between human and vehicle while researching the handling and stability of the miniature vehicle.In order to research the influence of human-machine dynamic coupling effect on the small scale electric vehicle yaw stability, the following tasks have been mainly carried out:First, an innovative three degree-of-freedom yaw dynamics simplified model, human-bicycle model is proposed and theoretical derivation is carried out in detail.Second, the dynamical model of a small scale electric vehicle has been established based on multi-body dynamics theory and ADAMS/Car software. What’s more, the multi-body model of human body related to the vehicle handling stability, has been developed based on the previous studies about human body dynamics. Finally, the human-machine multi-body dynamics system model is established. In order to ensure the accuracy of the whole vehicle model, the dynamic simulations of the whole vehicle, related to vehicle handling stability have been designed and accomplished based on the theories and methods of vehicle handling and stability road tests.Third, the differences of vehicle dynamic response between before and after consideration of the human-machine dynamic coupling have been analyzed comparatively with the help of the co-simulation of ADAMS/Car and Simulink controlling and simulating active behavior of the sitting driver based on the theories of human-machine dynamic coupling effect and vehicle handling stability. The influence of human-machine dynamic coupling effect on small scale electric vehicle has been studied. Meanwhile, the influences of some external factors on the effects of human-machine dynamic coupling effect have been explored.The analysis results indicate that:First, the yaw dynamics simplified model human-bicycle model is suitable for the study of human-machine dynamics coupling effect, verifying the influence of human-machine dynamic coupling effect on the small scale electric vehicle yaw stability from the theoretical level.Second, the changes of body posture has influenceon the steering movement track of small scale electric vehicle:the existence of coupling effect makes the small scale electric vehicle characteristic has sharp distinction and the trajectory has shifted and it is more likely to cause instability.Third, the human-machine dynamics coupling effect extends the response time and stability time of yawing response and increases the peak response and overshoot. However, it lags the peak response time. When the mass of vehicle is close to the human body, the overshoot amount of yawing response will differ 2-9% between considering and ignoring the human-machine dynamics coupling effect under the condition of the same system parameters.Four, the human-machine dynamics coupling effect on yawing characteristicis related to the proportion of the driver body mass to the whole vehicle mass and road friction coefficient: the greater the proportion of the driver body mass to the whole vehicle mass and the road friction coefficient are, the more obvious the effect of human-machine dynamic coupling on the yawing characteristic will be.Above all, the human-machine dynamics coupling effect and interaction between the human body movement and the vehicleis needed to be taken into account in the yawing stability design and dynamics analysis of small scale electric vehicle.