The Design Of Magneto-rheological Damper And The Simulation Of Control System

According to the basic theories of the magneto-rheological effect andmagnetic circuit Ohm's law the article has confirmed the design principle of thestructure and magnetic circuit of the magneto-rheological damper. Combining thedesign principle of the ordinary damper, work out a magneto-rheological damperwhich is monocular and single pole. On the basis of optimal control theory, theone-quarter-vehicle dynamic model and optimal controller is built up in MatlabSimulink, and then the dynamic simulation is running.1. IntroductionSummarizing the development and application tendency of Magneto-reologicalfluid and Magneto-rheological dampers, and combining the present jobs andexisting question at present on the subject, the paper has proposed the main contentand significance.2. Magneto-rheological fluid and magneto-rheological damperMagneto-rheological fluid consists of a carrier fluid, micron-sized ferrousparticles coating a colloidal dispersion suspended in it. When there is no appliedmagnetic field, the fluid flows freely just as the carrier fluid normally would. Thefluid is a Newtonian fluid. When a strong magnetic field is applied, the ferrousparticles in the fluid align themselves with the magnetic flux lines, significantlyincreasing the fluid's resistance to flow. The fluid does not flow until the shearstress applied reaches a threshold value, which is the yield stress of the fluid, afterwhich point the fluid flows freely.There are four performance modes of, and they are the flow mode, the shearmode, the squeeze mode and the shear-flow mode. In accordance with hydrome-chanics and hydraulic transmission theory, the damper forces' expressions of theflow mode, the shear mode and the shear-flow mode are work out and supply thetheory reference for the design of the magneto-rheological damper in the nextchapter. And this chapter introduces Bingham model, Bouc-Wen model Spencemodel and modificatory Bouc-Wen model and so on.3.The design of magneto-rheological damperOn the basis of magnetic circuit Ohm's law and the damping force formula ofthe magneto-rheological damper, the design principle of the structure and magneticcircuit has been confirmed (1)The smaller the piston clearance is, the stronger thedamping force is, however, in company with clearance being short, the rangeabilityof force decreases. In consideration of both of those, the size of the clearance isbetween 1 and 2 mm in general. (2)With the piston effective length increasing theforce enhances.Because the increase of the length will impact the damper's volume,the length is increased in the allowed extent.(3)The larger the effective area is, thestronger the force is, but the smaller the rangeability is, the relation between theforce and the rangeability should be considered during designing.(4)The stuff ofcylinder tube, piston and rob is both part of magnetic circuit and major support andload-bearing member, so they are choosed soft magnetic material which is highsaturation induction density, low coercive force, low remanence and certainintensity and toughness.(5) Field coil resistance is proportional to wire length andinversely proportional to sectional area, but wire diameter is so big that coil turnwill decrease, which will influence magnetic field intensity.Combining the design principle of the ordinary damper, the design parametersare designed, which include cylinder diameter, piston rod diameter, piston travel,clearance, effective length and coil turn.4.Performance tests and simulation-based analysisSeparately performance tests were made on ordinary damper and magneto-rheological damper, by comparing the test consequences there are some problemsin the sample piece of magneto-rheological damper, for example,undercompensation, there is impurity in the oil and the force decreases.The dynamic model is built up in Matlab/Simulink in accordance with bothdampers' mathematic formulas.It is proved that mathematic formula of ordinarydamper is correct because simulation curve is consistent with trial curve. Howeverthe simulation curve of magneto-rheological damper shows when the electriccurrent is constant, the damping force is proportional to vibration frequency;whilethe input frequency is constant, the damping is proportional to electric current.5.Control system and simulation analysis of one-quarter-suspensionIn order to validate the damping effort of the magneto-rheological damper, weapplied the optimal control arithmetic to realize the semi-control. According tomodel, and the structural parameters are obtained from a certain light truck. Thedynamic model is built up in Matlab/Simulink. Take the sprung body mass'sacceleration RMS the tire's dynamic loads as control object, and the suspensionstroke as a restriction, and then set up the optimal control system which takeselectric current as controlled variable. The paper chooses the stochastic signal asthe input of model. Finally, by comparing the acceleration RMSs and the tire'sdynamic loads of the three kind of suspension, the paper scales the controller'svalidity.6.ConclusionFirst design the structure of magneto-rheological damper, and carry on theperformance test and simulation analysis. The optimal control system is built up inMatlab/Simulink which take electric current as controlled variable, and thensimuliation analyse. The outcome proved it can improve ride comfort and handlingstability.The deficiency of the article is that we failed to finish the experiment of thedamper's control performance due to some reasons, and just had the simulationconsequence. While it is the work in the future that further research aspects whichthe manufacture of magneto-rheological fluid, structural optimization of magneto-rheological damper and control system design.