Research On Control Strategy Of Magnetorheological Torsional Damper For Engine Crankshaft System

With the development of automobile to the direction of high power and intelligence,the torsional vibration of automobile engine crankshaft system becomes more and more prominent,which not only seriously affects the driving performance of automobile but also damages the riding comfort of people.Therefore,it is of great practical significance to solve the torsional vibration problem of crankshaft system,which has attracted many scholars to carry out research on this aspect.At present,torsional vibration reduction of crankshaft system is mostly achieved by improving the design structure of crankshaft and adopting passive control.However,the effect of such vibration reduction method is relatively limited,and it is difficult to suppress the vibration of vehicle engine crankshaft system in various working conditions.The appearance of semi-active control method brings a better solution to the complicated situation of torsional vibration.It can realize the effective suppression of torsional vibration of crankshaft under broadband excitation.Magnetorheological(MR)material is a new kind of intelligent material with variable stress.The MR damping device developed by MR material has the advantages of simple structure,adjustable damping,low energy consumption and fast response.At present,MR materials are mainly used in some engineering equipment and vehicle suspension and other fields,among which the research on linear MR damper has been relatively mature,but the relevant research and application on MR torsional vibration control at home and abroad are relatively few,especially the research on crankshaft torsional vibration is mainly based on the structure design of MR damper.In order to solve the problem that traditional rubber and silicone oil torsional shock absorbers with unadjustable damping cannot effectively control torsional vibration at different resonant frequencies,a new type of crankshaft torsional shock absorbers is designed by taking advantage of the variable damping characteristics of MR materials,and a semi-active ceiling control and a fuzzy control method based on neural network are proposed.The simulation results show that it can effectively suppress the torsional vibration of crankshaft under multi-harmonic torsional resonance.The main work of this thesis is as follows:(1)Two degrees of freedom equivalent models of simplified torsional damper and crankshaft system are established.The design theory of torsional damper and the main influencing factors on system vibration are discussed.The influence of design parameters of torsion damper on crankshaft vibration system is analyzed and the feasibility of variable damping is presented.The basic working mode of MR damper is summarized,and the structure of MR damper is designed and the equivalent analysis of the model under different current is carried out,and the method to achieve crankshaft vibration reduction by changing the damping is put forward.(2)In order to obtain the mechanical properties of the crankshaft MR torsional damper,the test platform of the MR torsional damper experiment system was built and the related equipment was selected.According to the designed experimental scheme,different excitation is applied,and the mechanical relationship of the MR crankshaft torsional damper is tested on the torsional vibration test bench.According to the experimental results,the hyperbolic tangent control model of torsional damper was established by parameter identification and fitting,which laid a foundation for the control strategy design of MR torsional damper.(3)A simplified discrete model of crankshaft system of an automobile engine is built,and the natural frequency and mode of crankshaft system are obtained by free vibration analysis and calculation with MATLAB.The working model of crankshaft is established by AMESIM software,and the driving torque of engine is calculated to simulate and analyze the forced vibration of crankshaft.Through the analysis of free end torsional vibration of the crankshaft system at acceleration and uniform speed,the influence of different damping on the torsional vibration of the crankshaft is explored,and the frequency shift effect of different damping on the resonance frequency of the crankshaft is verified.(4)According to the torsional vibration analysis of crankshaft and the mathematical model of MR damper established,the canopy semi-active control strategy based on torsional vibration of crankshaft and the fuzzy control strategy based on neural network inverse model are designed.Through the co-simulation of AMESIM and MATLAB,the attenuating effect of the two control strategies on the crankshaft torsional vibration under the condition of acceleration and uniform speed is obtained,and the control effect of the two control algorithms is compared,which shows that the fuzzy control strategy based on neural network has better vibration reduction effect than the ceiling control and passive control.