Study On Optimal Damping Semi-Active Control Of Double Layer Vibration Isolation Nonlinear System

Double-layer vibration isolation system is a kind of vibration isolation system aiming to implement vibration suppression step by step by means of double layer structures.The system dynamics model of a large number of engineering vibration isolation system is established which can make use of this system.The application range of the vibration reduction system is very wide,such as applied to submarine floating raft isolation system,used in automobile suspension damping system,etc.At the same time,this system can also be divided into vibration isolation of force and vibration isolation of displacement,etc.In the field of vibration control,vibration control is divided into three kinds of methods,such as,passive,active and semi-active control,according to the size of input energy from external on the vibration isolation device.Now the intermediate elements of double-layer vibration isolation nonlinear system are mainly composed of passive components with fixed damping characteristics.This will lead to limit the vibration isolation effect of total vibration isolation device to a certain extent,so that vibration isolation efficiency on one width of exciting frequency is good while efficiency on the other width is bad.The vibration isolation performance of isolation system must be improved through installing intelligent damper with developed variable damping characteristic in vibration system and designing control algorithms,adjusting the size of the controlled yield damping force of damper according to designed control strategy applied on isolation system to external signal excitation.The output damping force is adjusted by controlling the electric field intensity of electro-rheological device,thus it acts as a good medium of electrical and mechanical connection units in intelligent mechanical and electrical control system.Vibration isolation test bed and control system is the key equipment to realize the control method and testing electro-rheological device performance.In this paper,the electro-rheological intelligent damper is a nonlinear part in the double-layer vibration isolation system.Due to various components constituting of system are of limited maximum capacity,various components will appear the saturation phenomenon,the saturation nonlinear of the actuator is a typical characteristic of semi-active double-layer vibration isolation system.So the controller of bilinear systems is also constrained by the range of damping size.The search problem of the optimal solution of linear model was solved by predecessors in the semi-active damping control research,but they did not search for the optimal solution for the model of bilinear system.Therefore,the research prospect of the bilinear systems is inviting.This project research results have great application prospects and social and military value in submarines,other ships,automobiles,high-end machine tools,earthquake-resistant structure,etc.The main work of this paper is that designing different control strategies to control the nonlinear system of double layer vibration isolation,the vibration isolation performance of the bilinear system with intelligent damper is evaluated by simulation and experiment,the desired vibration isolation effect is achieved.The important innovations of this paper are given as following:Firstly,based on the fact that for the damping curve of the two-stage vibration isolation nonlinear system exists the defects that can't be solved,comprehensive utilization of the principle of generalized variational method,introducing the pulse function,using the steepest descent method is proposed to solve the variational derivative of the performance index functional of vibration attenuation,the optimal solution of the non-differentiable curve in the engineering practice is solved.Secondly,based on optimal control and semi-active control,the optimal damping semi-active combined control method is presented,this method is used to adjust the size of the controllable yield damping force of the intelligent damper,the vibration reduction effect of the vibration attenuation system within low frequency band are obviously improved.So the vibration isolation effect of the optimal damping semi-active control is investigated under the excitation of the(single frequency,dual-frequency,multiple frequency,high frequency)sine signal,random signal,impact signal,all kinds of hybrid signals in this article.It mainly aimed at five different control methods,including: the optimal damping semi-active control,skyhook damping semi-active control,optimal passive damping control,the maximum passive damping control and the minimum passive damping control.Simulation experiments show that vibration reduction effects of the optimal damping semi-active control for the shock signal is better than that of the random signal.The effects of the optimal damping semi-active control in the above five kinds of control methods is the best.Thirdly,based on the model of bilinear damping control system,the intelligent vibration attenuation control strategies are suggested to adapt to the changes of the external excitation frequency within different frequency band,the frequency band range of vibration reduction is enlarged.Lastly,the force isolation testing platform is combined with control system,on which the experiments using optimal damping semi-active control law to control the change of damping force of vibration isolator are brought out.The experimental results show that optimal damping semi-active control can improve the performance of the force vibration isolation system effectively.