Estimation Of Vehicle State And Road Adhesion Coefficient Of Four-wheel Independent Drive Electric Vehicle

The ever-increasing variety of passenger cars and the increasingly complicated vehicle dynamic control strategies have set higher requirements for the accuracy of vehicle state parameters.As the key components of the vehicle state parameters,vehicle side slip angle and maximum tire-road friction coefficient cannot be measured in real time on the passenger car platform,and it is particularly important to estimate their state parameters effectively.To estimating vehicle side slip angle,tire and vehicle models in the field of vehicle dynamics are used to design a closed-loop state observer that acts perfectly.To be specifically,the linear two-degree-of-freedom(DOF2)vehicle model acts as the original system of the state observer,what is,simultaneously,The Unified Tire Model(UniTire)is used to construct the state feedback of the observer.The two models are combined to form the closed loop of "vehicle speed-slip rate-tire force-acceleration-vehicle speed".From the experimental verification results,the centroid roll angle observer in this paper can effectively suppress the noise and offset carried by the acceleration measurement value,and achieve an effective estimation of the vehicle speed and vehicle side slip angle.To estimating maximum tire-road friction coefficient,this paper creatively deduces the original system using "In time adhesion coefficient-Tire stiffness".Basing on this original system,a closed-loop state observer shows up perfectly using "closed-loop" characteristics of adhesion coefficient.In the design of the observer,considering that the dynamic characteristics of the vehicle and tire under the conditions of longitudinal slip and side slip are quite different,the maximum tire-road friction coefficient observer designed in this paper is different,while facing the situation of longitudinal and lateral.For the maximum tire-road friction coefficient observer facing the longitudinal slip condition,since the longitudinal vehicle speed state estimation error is not large,the estimated value of the wheel longitudinal slip ratio state is easy to obtain.When designing the observer,only the"utilization adhesion coefficient" "Closed-loop correction is sufficient.According to the basic idea of state observer design,this paper first designs the original maximum tire-road friction coefficient observer system for longitudinal sliding conditions.The UniTire model is then used to construct a feedback correction term for the longitudinal tire force of the state observer,so that the observer forms a closed loop.Finally,from the results of experimental verification,the pavement peak adhesion coefficient observer for longitudinal sliding conditions in this paper can effectively identify ice and snow pavements and provide reliable estimates of the state of the pavement peak adhesion coefficient,achieving the expected results.In order to further effectively identify wet cement pavement and dry cement pavement,this paper develops a maximum tire-road friction coefficient observer facing the side slip condition.During the design of the observer,it was found that it must be coupled with the centroid side-slope angle observer.For example,to estimate the road peak adhesion coefficient,you must enter the sidespeed,and the centroid side-angle estimation must require the tire sideways stiffness input.In order to ensure the reliability of the designed observer,this article uses the idea of "control variable".First,install a combined inertial navigation device on the test vehicle,and take the side deviation angle of the center of mass and the lateral speed as the known quantities.Observation of pavement peak adhesion coefficient under working conditions and verification.From the verification results,when the side deviation angle of the center of mass is known,the pavement peak adhesion coefficient observer for the side-sliding condition can effectively identify ice and snow roads,wet cement roads and dry cement roads.Based on this research,this article continues to design a joint state observer for the centroid sideslip angle and the pavement peak adhesion coefficient.When designing the state observer,it is not just a simple splicing of the centroid side deviation angle observer and the pavement peak adhesion coefficient observer In addition,from the perspective of global optimization of the observer,the estimation of the centroid sideslip angle and the estimation of the pavement peak adhesion coefficient have been changed in the context of the joint state observer.From the results of experimental verification,the joint state observer of the centroid slip angle and the maximum tire-road friction coefficient in this paper can not only recognize different road surfaces,but also effectively estimate the centroid slip angle and tire lateral force.Because the joint state observer only needs the most basic signals on the passenger car as the observer input,and has considerable parameter estimation effects,it has a good application prospect in the field of passenger cars that demand "low cost and reliable".