Research On All-wheel Steering Control Of Three-axle Vehicle Based On Inertial Regulation Suspension System

Ride comfort and handling stability were important evaluation indexes of maneuverability of emergency rescue vehicles.At present,the active suspension system was an effective way to improve the ride comfort of vehicles.Therefore,it is of great theoretical significance and practical application value to study the driving stability of multi-axis emergency rescue vehicles with active suspension systems.This article combines the national key research and development plan project "Research and Application Demonstration of Key Technology of High Mobility and Multifunctional Emergency Rescue Vehicles"(Project Number: 2016YFC0802900),taking three-axis emergency rescue vehicles based on inertial control suspension system as the research object,by studying all-wheel steering Control strategies to improve vehicle handling stability.A two-degree-of-freedom linear model of a three-axis steering vehicle was established,and the position of the vehicle’s steering center and the angle of rotation of the outer wheels of the front wheels under the condition of a minimum turning radius of 8 m were calculated.The time domain response of three axle all wheel steering vehicle in transient and steady state was analyzed by using the zero center of mass side slip control theory.Taking the roll motion into account,a nonlinear three-degree-of-freedom steering dynamics model of a three-axis all-wheel steering vehicle was established.Considering the non-linearity of the tires,the calculation models of three-axle vehicle were built for the tire lateral force,vertical load and tire slip angle,and the vehicle steering system was simulated and analyzed.Based on the three degree of freedom nonlinear model of vehicle,the proportional feedforward controller and the optimal feedback controller as well as the proportional feedforward fuzzy feedback controller were designed.The steering performance indexes such as mass center side slip angle,yaw rate,side roll angle and yaw rate were simulated and compared.Considering the effect of active suspension on the steering system,the steering stability of the vehicle based on active suspension was simulated and the vehicle dynamics equations were derived.The road surface excitation calculation model and the vehicle steering simulation model were established,and the vehicle steering model was simulated and analyzed at different speeds.Based on the active suspension system,the vehicle steering stability is simulated.A steering model considering the influence of the suspension system is established,and a ninedegree-of-freedom suspension model and an H∞ state feedback controller are established.Carry out simulation analysis on the whole vehicle steering model,calculate the center of mass side slip angle,yaw rate,body roll angle and roll rate and the drop ratio under active suspension and passive suspension,and the results reflect the superiority of active suspension,verified the validity of the established vehicle steering model.