Theoretical Research And Simulation On Raft Vibration-isolating Unit

Raft vibration-isolating unit is a device that can isolate the transmission of vibration and structure noise to the base effectively. Should it be designed perfectly, it can provide about 35~40dB vibration level difference.With theoretical, experiment and computation study, the factors influencing the effect of vibration-isolating are analyzed completely in this paper. Two layers vibration-isolating unit has been compared with single layer one, its delivering rate of force and a group of parameter curves have been obtained based on the characteristics of attenuation and stability.In point of isolated force and rigidity, two layers vibration-isolating unit is far more superior to single layer one. Because the ratio of the delivering rate of the former is in direct proportion to 1/w4 when frequencies are higher than second-harmonic vibrator but that of the latter is in direct proportion to 1/w2.Raft vibration-isolate simulation system of this paper can provide the functions as follows:1. It can calculate the natural frequencies, vibration modes, modular state and dynamic response of the unit according to the given structural parameters of the selected raft vibration-isolating unit, the number of vibration isolators and their installation positions. And also, the design effect of the selected scheme can be displayed vividly.2. It can intelligent evaluate the raft vibration-isolating unit design based on the abilities of nonlinear mapping and self-learning of the BP. The principle of the evaluation system is described in details, included: defining the layer numbers of hidden neurons, defining the processing unit numbers of hidden neurons, defining the train numbers and selecting original value; input and output parameters determination etc. The BP net can study and story a lot of mapping relationship of input-output model, and need not mathematics describing of mapping relationship in advance. It only need be trained with enough couples of input-output model (sample set). After training, the BP can capture the inherent nonlinear mappingrelationship held in sample set. While in operation, it can finish any nonlinear mapping from n-dim space of input to m-dim space of output. On the principle, the system has adaptive ability and can evaluate the raft vibration-isolating unit design according to the selected parameters of the different vibration isolators.3.By using the VR technology, the system gives a raft vibration-isolating unit assembling process to users for the first time.The simulation system having adaptive ability provides a simulation way, improves traditional design way. Besides, all of designing and analyzing processes in this system are lifelike by using VR and 3-dimensional simulating technology.