Study Of The Dynamics Of Multi-axle Vehicle With Zero Turning Radius

For multi-axle heavy vehicles,especially military armored vehicles,improving its mobility has been focused by domestic and foreign scholars.Aiming at the way of Skidsteering of tracked vehicle,the research on Skid-steering wheeled vehicle is increasing.The research of Skid-steering wheeled vehicle is the basis of wheeled vehicle Zero radius steering study.Therefore,in order to improve the steering maneuverability of the wheeled vehicle,multi-axis wheeled vehicle in Zero radius steering research has also been focused by domestic and foreign scholars.Owing to the increase of steering resistance torque caused by Skid-steering,Tire slippery grind and other problems become serious.Therefore,this paper studies the Zero radius steering of wheel deflection angle guidance,although the wheel deflection angle can reduce the tire longitudinal slip and its side angle,the tire is still in a large longitudinal slip and large side deviation conditions because of the particularity of the Zero radius steering.The alter of wheel deflection angle will make the longitudinal and lateral angle changes,thus affects the lateral adhesion and tire slip characteristics.The traditional "Magic Formula" tire model is no longer applicable to the study of tire dynamic characteristics in this condition.Therefore,based on the “Unitire tire model”,we established the formula of lateral angle of tire ground imprinting micro element,established a model of longitudinal and lateral deformation of ground imprint.analyzed the characteristics of the tires slip characteristics and the influencing factors.Based on this,the dynamic characteristics of the tire are analyzed.Based on the nonlinear dynamic characteristics of the tire,we established a 6X6 vehicle Zero radius steering dynamics model,and established the analytical formulas of resistance moment and longitudinal force.The effects of wheel deflection angle,wheelbase,track distance and centroid position of mass to lateral force,resistance torque and longitudinal force of Zero radius steering are studied.And we studied the characteristics of low power consumption,the results show that increasing the wheel deflection angle,reducing the wheelbase,increasing the track distance and the certain longitudinal offset rate of centroid are all beneficial to reduce energy consumption of Zero radius steering.In this paper,we established the dynamic model of three different Zero radius steering modes of 8X8 vehicles,and compared the total power consumption and longitudinal force with 6X6 vehicle.In the same conditions,the total power consumption of 8X8 vehicle Zero radius steering from low to high is: all-wheel 1: 1 proportional deflection,all-wheel Ackerman proportional deflection,and part of the wheel deflection.When the wheel deflection angle is small,6X6 vehicle steering resistance torque and total power consumption are less than 8X8 vehicle all-wheel 1: 1 proportional deflection.Finally,we set up an 8X8 distributed driving all-wheel steering test platform,and conduct experimental verification.The experimental results are consistent with the theoretical analysis,the maximum numerical error is less than 18%,so the results can be used to guide the design of multi-axle vehicle Zero radius steering.