Research On Four-corner Interconnected Air Suspension And Its Interconnected State Control Method

Air suspension has the characteristics of variable spring stiffness and adjustable body height.In order to further improve the performance of air suspension,a number of derivative structures emerge as the times require,four-corner interconnected air suspension is one of them.As a form of air suspension interconnection,four-corner interconnection connects every two adjacent air springs of vehicle air suspension with pipes,and installs solenoid valves in pipes to control the interconnection state of air suspension.The structure of the four-corner interconnected air suspension determines that it has the characteristics of both lateral and longitudinal interconnection of the air suspension,which can effectively reduce the body roll or pitch caused by road excitation,and has good vibration isolation performance.However,interconnection opening can significantly reduce the roll stiffness and pitch stiffness of suspension,and increase the roll or pitch of vehicle body when turning or decelerating at high speed.In view of the above problems,based on the existing research,an interconnected state control method of four-corner interconnected air suspension is proposed,which provides a reference for improving the practicability of four-corner interconnected air suspension.Firstly,the working principle and characteristics of four-corner interconnected air suspension are analyzed.Based on the theories of hydrodynamics,engineering thermodynamics and vehicle dynamics,the parameters needed for modeling are obtained and the vehicle dynamics model of four-corner interconnected air suspension is established,the 7-DOF vehicle model considers the roll,pitch,vertical motion of the body and the vertical motion of four unsprung masses.In order to research the effect of axle load transfer on vehicle body pitch during vehicle acceleration and deceleration,a vehicle acceleration and deceleration model was established.The pavement excitation model is established based on white noise method,the coherence of left and right pavement and the hysteresis of rear wheel excitation relative to front wheel are considered.Secondly,the air suspension of the test vehicle was modified with interconnected pipelines,and the feasibility of the four-corner interconnected air suspension has been verified by loading concentrated loads at different positions of the vehicle body.The static characteristics of the front and rear axle air springs are tested,the variation of load and effective area of air spring with working height is obtained.In order to verify the accuracy of the model,vehicle uniform speed through deceleration belt test,steering wheel angle step test and deceleration braking test were carried out.The test results show that the parameters of the vehicle model,such as the sprung and unsprung mass acceleration of the front left spring,the roll velocity and the pitch velocity,are in good agreement with the test data.The model can reasonably reflect the vibration isolation,roll and pitch performance of the vehicle.The accuracy of the model is high,which lays a foundation for the simulation analysis.Finally,aiming at the existing problems of four-corner interconnected air suspension,according to the working characteristics of four-corner interconnected air suspension,an interconnection state control method of four-corner interconnected air suspension is proposed.The simulation results show that the control method has better performance in the body roll angle,pitch angle and mass acceleration on the front left spring under several typical working conditions compared with other interconnection methods.Random road simulation results show that the vehicle roll angle,pitch angle and the root mean square value of mass acceleration on the front left spring under the interconnection control method are also the smallest compared with other interconnection methods.