Design And Performance Analysis Of H_∞ Controller For Automotive Semi-active Suspension Under Discrete Impact Conditions

The vehicle suspension system plays an important role in supporting the body and isolating the road surface excitation,and plays an important role in ensuring ride comfort and driving safety.Magnetorheological semi-active suspension can change the damping by adjusting the current to better suppress the vibration caused by uneven roads,and has the characteristics of wide damping adjustment range,simple mechanical structure,and low energy consumption,which has attracted wide attention.At present,the research of magnetorheological semi-active suspension is mainly aimed at the road surface with low excitation amplitude and small frequency change.Different from graded roads,discrete impact roads have large excitation amplitude,short duration,and large changes in excitation frequency,making the semi-active suspension under discrete impact roads have more complex control problems.For this reason,this paper studies the suspension control problem under discrete impact road.From the perspective of vehicle vertical vibration suppression and pitch suppression,this paper establishes a 1/2 vehicle model for studying vehicle pitch dynamics through simplified vehicle structure,and a 1/4 vehicle model for studying vehicle vertical vibration dynamics.The hyperbolic tangent model is used to describe the nonlinearity of the magnetorheological damper,and the mathematical description of the vehicle-road coupling excitation is established.Use high-precision vehicle dynamics simulation software for simulation under discrete impact conditions to verify the accuracy of the modeling.Aiming at the characteristics of large excitation amplitude in discrete shock conditions,a method for modeling the damping force of a damper with segmental constraints is presented.Through the analysis of damping force characteristics,the segmented constraint modeling method given in this paper has a larger damping force range and reduces the number of segments,which is beneficial to controller design and control performance analysis.On this basis,the H∞ controller is designed with the damping force as the control quantity.By comparing with soft suspension,hard suspension,and hybrid sky-hook control,the feasibility of the controller given in this paper is verified under discrete impact conditions.The development of intelligent network technology allows vehicles to obtain information on uneven roads such as speed bumps and pit-bag contours.In this context,the external disturbance energy in the H∞ controller design is changed from unknown to known,which brings about a new vibration suppression H∞controller design problem with known discrete shock excitation information.Aiming at the suspension control problem in the context of intelligent network connection,this paper analyzes the influence of interference energy on the vibration suppression H∞ control performance under discrete impact roads,and explores a control method that uses a front-end compensation item to improve vibration suppression.By analyzing the characteristics of vibration when the wheel is in contact with and disengaging from the bulge,a method for adjusting the front-end compensation item according to the contact state of the wheel and the bulge is given.In order to obtain the contact between the wheel and the bulge,a vehicle-road coupling state recognition method based on long and short-term memory neural network is designed using vehicle vibration information.The neural network was trained using the data generated by the vehicle-road coupling model,and the recognition accuracy of the vehicle-road coupling state of the recognition method was verified.Combined with the influence of the front-end compensation item on the vibration suppression performance,a switching strategy based on road recognition is designed,which effectively improves the comfort of the vehicle.In addition,a damper model mismatch correction method is proposed for the road section where the wheels are away from the bulge,which improves the control performance.Aiming at the pitch problem caused by the vehicle driving on uneven roads,an integrated controller for the front and rear suspension is designed based on the 1/2 vehicle model.In order to solve the problem of high model dimensionality and the H∞ controller design process based on the LMI technology,the 1/2 vehicle model is simplified,and a rear suspension controller considering the pitch of the vehicle is given.Compared with the controller designed independently for the front and rear suspension,the controller can better restrain the pitch of the vehicle,and can effectively improve the comfort of the ride.