Research On Vibration Isolation Of An Engine Via Magnetorheological Fluid Mounts

As a power plant, engine has widely adopted in vehicles, ships, aircraft carriers. Bytechnical conditions, it does not exist another power plant can replace the engine whichprovide a reliable and lasting power to launch vehicle. However, due to the combustionof the fuel in the cylinder inertial force caused by the impact caused and reciprocatingmember, the engine will inevitably generates a plurality of different local oscillatordifferent vibration type complex vibration, the vibration of the mixed superimposedwith broadband, multiple vibration sources andmulti-frequency characteristics, whichmakes the engine become the car on the main vibration source, Therefore, the enginevibration isolation problems are the concern of a large number of researchers, mainlythe rubber suspension or hydraulic suspension to vibration isolation. Traditional therubber suspension or hydraulic suspension which can only be obtained in the lowerfrequency range isolation effect is difficult to meet the requirements of broadbandvibration isolation. Magnetorheological fluid suspension emerged in recent years, withdamping adjustable, fast response, wide dynamic range, low power consumption,simple structure, is an important development direction of one of the engine activevibration isolation. At present, the domestic and foreign magnetorheological suspensionresearch is still in its infancy, yet accurate mechanical model of a recognized model forthe dynamics of such suspension, engine vibration source has a pulse, wide workfrequency domain, the entire vibration isolation system is a nonlinear, time-varyingsystem, which makes the isolation method of design and experimental full difficulty.contrary to4-cylinder4stroke engine magnetorheological control isolation platformwhich bulit in ChongQing JiaoTong universtiy, this paper subsidied by the Foundationof Natural Science to reseach the theoretical analysis,numerical simulations,andexperiments are applied to study the dynamic characteristics of an engine vibrationisolation system,the engine parameter identification methodologies,the test andmodeling methodologies of an MRF mount,the isolation control methodologies,thesimulation of engine isolation system,as well as the design of the multifunctionlaboratory platform and the realization of the engine isolation system.The maincontributions of the dissertation include the following:①The significance of the engine vibration isolation via MRF mount system isexplained.The engine mounts,engine vibration isolation dynamic models,engine parameters identification,and isolation control methodologies are reviewed.Moreover,the main research works aimed at the problems in engine vibration isolation via MRFmounts are addressed.②The strucure and mechanical model of the MRF suspension bass on squeezemode and the The formula of the MRF mounts react force s analysied in this paper. Asuspension dynamic characteristics test method which is verifid By numericalsimulation has been founded. By use this method to field trials, the suspension dynamiccharacteristics parameters fitting equation is identified.③A dynamic model and a kinematics equation are built,which can reflect thendpitch vibration of the main vibration states of a four-cylinder engine after the analysis ofengine excitation resource. Moreover,a single-layer isolation principle is applied todiscuss engine isolation performance through engine excitation,mount damping,andstiffness.These provide the basis for the design of the vibration isolation controller.④Based on the damping controllability of the magneto-rheological damper andthe relativity between the unbalanced forces and rotate speed of the engine, a newmethod for identifying inertia parameters and unbalanced forces of the engine wasproposed by measuring engine mount accelerations and support reactions on differentdamper coefficients. Compared with traditional methods, this method has the merits oftargeted, repeated test without motor lifting, all parameters identified simultaneously.The effectiveness of this method was verified by a simulation modeling and the testingof a four-cylinder four-stroke powertrain. Results show that the recognition accuracy ofinertia parameters meets the engineering needs and the unbalance force identificationresults are more realistic compared to a simplified formula.⑤To obtain the better Isolation effect of MRC in Broad Frequency, it is necessaryto optimize the initial stiffness. For Motor unbalanced force and isolation systemdumping were not considered in The Traditional Optimization method, the feature ofsemi-automatic can not be reflected. Adopt a four-cylinder four-cycle in-line dieselengine, use Genetic Algorithm to Found a new method which is suitable for Stiffnessoptimization on vehicle engine isolation via MRC mounts. The new method Applyisolation system possess smaller absolute force transmissibility in abroad frequencyrange and Standards compliant of Vibration intensity when suffering Impact load.⑥Found a method which feedback system velocity、acceleration and engine speedby improve instantaneous-optima-algorithm. The simulation results show this controlmethod is more effective in different work condition than traditional instantaneous-optima-control. Bass on the relation ship between react force, rote speedand accelerate which can be goted by simulation result, a new fuzzy control method isfounded.