Development Of Vehicle Semi-active Suspension Control System And Research On Optimal Control Method

With the continuous increase in the per capita disposable income of Chinese citizens and the popularization of automobiles,private car travel has become one of the main modes of travel for people,and the ride comfort of the car which is a major factor affecting the driving experience has become more important.The suspension system,as the connection part between the wheel and the body,is the most important factor affecting people’s ride comfort.Due to the fixed structure,the passive suspension is inconvenient to adjust,and its performance is limited.With the development of electronic technology,various electronically controlled suspensions came into being.Among various electronically controlled suspensions,semi-active suspensions have received extensive attention from scholars and automobile manufacturers due to their high performance-to-power ratio,high reliability,and low structural complexity.They are currently a hot topic in suspension research.This paper studies several classic and hybrid control strategies of semi-active suspensions,analyzes and verifies the existing control strategies,and improves them in combination with practical applications.The semi-active suspension electronic control unit is designed and tested.Mainly include the following:The establishment of semi-active suspension related models: According to the nature of different signals and the characteristics of the suspension system,four kinds of road excitation models commonly used in suspension analysis have been established,including sine and swept frequency pavement model used for frequency characteristics analysis.Model,used to simulate the random road surface model of actual road conditions and the bump road surface model for simulating specific road conditions;using damping force to replace the shock absorber unit of passive suspension,and establishing single wheels that can be used to describe passive and semi-active suspensions respectively two-degree-of-freedom quarter-vehicle suspension model and seven-degree-of-freedom vehicle suspension model;a quantitative calculation method for suspension comfort and road adhesion is proposed.Semi-active suspension control strategy analysis,simulation and improvement:The energy transfer of the suspension system is discussed and three classic control and two hybrid control strategies used in semi-active suspension are analyzed,including SH,ADD,PDD,SH-ADD,and single-sensor hybrid control.Based on Simulink environment,each control strategy is modeled and verified by simulation.The characteristics and shortcomings of each control strategy are analyzed,and the frequency band selector used by the two hybrid control strategies is explained.In view of the integral drift phenomenon in practical applications,the frequency band selector is improved,using differentiation instead of integration,and the single-sensor control strategy of the improved frequency band selector is simulated and verified.Design of the electronic control unit of the semi-active suspension: the hardware circuit of the electronic control unit is designed in combination with the test requirements and the actual vehicle use,the differential acquisition unit is added to reduce the common mode interference and improve the acquisition accuracy,and the damping adjustable shock absorber is designed Drive circuit;the software development of the electronic control unit is carried out using the method of model-based design,the Simulink code generation technology,combined with the STM32 Mat Target target support toolbox,has realized the automatic generation of Simulink model to STM32 embedded code.Suspension bench test: A bench test was carried out using a quarter-suspension bench of the physical simulation and the designed electronic control unit to verify the effectiveness of the improved control algorithm.The experiment showed that the improved control algorithm is similar to the original algorithm in improving the comfort,and has a significant improvement compared with passive suspension.This paper systematically analyzes the performances and characteristics of several semi-active suspension control strategies by way of comparison,chooses single-sensor hybrid control as the optimal control strategy for practical applications,and conducts the single-sensor hybrid control strategy based on practical applications.The improvement,in principle,avoids the cumulative error caused by the sensor signal integration.