Comfort-oriented Semi-suspension Robust Control And Velocity Optimization Of Intelligent Vehicles

Intelligent vehicles are the trend of future automobile industry and the most innovative technology areas.As the ultimate goal of intelligent vehicles,driverless vehicles bring lots of challenges for sensor technology,intelligent technology,and control technology.Presently,the researches of intelligent vehicles mostly focus on solving the problem about driving safety,and the researches on ride comfort are rare.But in fact,comfort performance is an important performance index for vehicles.Therefore,this paper focuses on the promotion of comfort performance and provides effective control methods for intelligent vehicles.This paper does the researches in two aspects.Based on the characteristics of intelligent vehicles with more road information,one aspect is studying the semi-active suspension control algorithms to suppress disturbance.The other is exploring a velocity control method when driving on uneven roads for further improvement.In this paper,the research methods and results are described in three parts: vertical dynamics modeling,semi-active suspension robust control,and velocity optimization.In order to achieve above objectives,firstly,as the quarter suspension model can just represent the vertical movement,a 7 Do F(Degree of Freedom)model which can reflect the vertical,pitch and roll movements of vehicle body is given and a hyperbolic tangent model containing the nonlinear properties of MR(Magneto Rheological)dampers is presented.In order to describe the road excitations in different road conditions,this paper gives the description of four-wheel excitation signals on random roads and discrete roads,based on the equivalent covariance method and the analysis of correlation of left and right wheel excitations and the time lag of front and rear wheel excitations.The dynamical models in this part lay a foundation for the analysis of comfort performance and the controller design.Further,in order to solve the problem that current semi-active suspension control methods mostly adopt one controller gain to adapt various complex road conditions,this paper firstly analyzes the impact on comfort performance when changing MR damper characteristics in different road conditions,and summarizes the problems of existing control algorithms.Then,based on the road recognition technology of intelligent vehicles,the paper proposes a robust control method combining a feed-forward controller to determine the damper working point in different road conditions and a feedback controller to adjust near the point.The simulation results show the effectiveness of proposed method for the improvement of comfort performance in different road conditions.Finally,the paper proposes a velocity control method to improve the ride comfort performance of intelligent vehicles,which is different from the general researches that focus on the driving safety.Firstly,the relationship between vehicle velocity and the comfort index is analyzed and a non-monotonic polynomial is presented.Then,a velocity control requirement considering driving performance and comfort performance is constructed and transformed into a multi-objective optimization problem.By using Pareto optimization theory,a set of Pareto optimal solutions is obtained.Finally,to choose a velocity from the Pareto optimal set,a strategy considering the comfort indexes is given.This strategy can be applied to velocity planning of intelligent vehicles on uneven roads.The simulation results show that the proposed velocity control method is effective and feasible.