Nonlinear Mem-inerter And Its Performance Effect For A Vehicle Suspension

The inerter instead of the mass element forms a new suspension structure system of Inerter-Spring-Damper,which can improve the vibration isolation performance of suspension and open up a new way for the development of passive suspension.The passive seriesparallel ISD suspension with simple structure can improve the dynamic performance of the vehicle suspension and ride comfort of the vehicle.However,ISD suspension using a linear inerter element cannot balance the ride comfort of vehicle with full load against with no load.In order to improve the load adaptability of series-parallel ISD suspension,a design scheme of replacing linear inerter element with nonlinear mem-inerter element is proposed in this paper.A nonlinear MISD(Mem-inerter-Spring-Damper)suspension system with inertance adapting to the variation of vehicle load is developed to further improve vehicle ride comfort under non-full loads.The nonlinear MISD suspension conforms to the development trend of basic elements of suspension from linearity to nonlinearity,and is a new development direction of ISD suspension technology.Firstly,based on the new mechanical-electrical analogies and the triangular periodic table of elementary mechanical elements,the concept of mem-inerter is introduced,the constitutive relationship of mem-inerter is deduced and the nonlinear and memory characteristic of it are expounded.A hydraulic mem-inerter device is designed and the mathematical models of mem-inerter and its parasitic damping are set up.The difference between nonlinear mem-inerter and inerter is discussed.Furthermore,the equivalent relationship between a given static equilibrium position of mem-inerter and a given inertance of inerter is established by analyzing the transmission characteristics of a single mass suspension system.Secondly,aiming at the problem that the linear inerter of series-parallel ISD suspension cannot adapt to the change of vehicle load,the design scheme of replacing the linear inerter element with the nonlinear mem-inerter element is put forward.A nonlinear MISD suspension system with inertance adapting to the variation of vehicle load is developed to improve vehicle ride comfort under non-full loads,especially under no load.Moreover,multi-objective genetic algorithm is used to optimize the parameters of MISD suspension.On this basis,the equivalent relationship between the static equilibrium position of meminerter and the inertance of inerter under different loads is verified by simulation.Thirdly,a quarter vehicle model of MISD suspension with parasitic damping is established.When the target vehicle is under no load,quarter load,half load and full load,the impulse response,sinusoidal input response and random input response of three suspension systems are simulated and analyzed with traditional passive suspension and series-parallel ISD suspension as comparison of performances.The results show that compared with traditional suspension,MISD suspension can improve vehicle ride comfort and tire grounding performance under these four loads;compared with series-parallel ISD suspension,the performance of MISD suspension at full load is equal to that of series-parallel ISD suspension,and it can effectively improve vehicle ride comfort under non-full loads,especially under no load.At the same time,it can also improve tire grounding performance of the vehicle under half load and quarter load.Finally,a prototype of hydraulic mem-inerter is developed,and the test verification of the device is carried out on INSTRON8800 test bench.The test results show that both the damping characteristic curves and the characteristic curves of mem-inerter contain the pinched hysteresis loop,which is the fingerprint of memory elements.It is proved that the device is a hydraulic mem-inerter,and its parasitic damping is a hydraulic mem-dashpot.