A H_∞ Control Approach To MR-Damper Semi-Active Suspension Via Reverse Hyperbolic Tangent Model

The semi-active suspension has advantages of small volume, good performance, low price, and has won the extensive research and application of engineering and academic circles both at home and abroad. Because of less power consumption, having the advantages of fast response and good controllability, magneto-rheological(MR) damper has become an important research object of the semi-active suspension. So researching the MR semi-active suspension control method of vehicle suspension system is of great significance.In this paper, in view of the uneven road surface(such as bump or pothole) and in order to improve the trade-off between comfort and suspension travel, a H∞ controller for damping force of semi-active suspension equipped with magneto-rheological(MR) damper is presented, and combined with the inverse hyperbolic tangent model of MR damper to obtain driven current, thereby, to achieve the controlling of vehicle semi-active suspension.In order to achieve the MR semi-active suspension control, chapter 2 firstly analyzes the characteristics of the MR damper, MR damper exhibit strong nonlinear dynamical behavior including bi-viscous and hysteretic behaviors. then the existing model of MR damper is simulated and analyzed. According to the simulation model’s data, a two varying parameters of Hyperbolic tangent model of MR damper is showed, on the basis of this model, an inverse model to obtain driven current is calculated. Last, simulation results show the validity of the inverse model. Due to MR damper’s strong nonlinear, complex structure, it is very difficulty in designing controller according to MR damper model. So, this paper presents a solution for semi-active suspension control in which a controller for damping force of semi-active suspension equipped with MR damper is presented, and combined with the inverse model of MR damper to obtain driven current.In the damping force controller design process, in order to achieve control of suspension system, chapter 3, first of all, analyze the inherent nature of suspension system, give the ride comfort, road holding and suspension stroke limitation’s relationship, providing theoretical guidance for the controller design and analysis. Then the uneven road surface model is given to prepare for the simulation analysis. In view of the uneven road surface, given the suspension performance objectives, chapter 3 presents a H∞ state feedback controller, and based on inverse MR damper model calculate the control current, and simulation analysis shows the validity of the control effect. However, this method requires the system state all measurable, brings to the application difficult of system that state cannot be directly measured. Moreover, the increasing of number of sensors enhances the control cost and reduces the system reliability.In view of the defects of H∞ state feedback control method, in chapter 4, a H∞ output feedback controller is given, expecting to get as much as possible H∞ state feedback controller’s control effect. The method adds the weighting functions to performance output to get the objective functions, and then solve linear matrix inequality(LMI) to obtain dynamic controller. Comparison H∞ state feedback control method, the simulation shows that the validity of the control effect.