A FEEDFORWARD CORRECTION METHOD FOR MULTI-SHAKER EXCITATION SYSTEM IN SINE TESTING

摘要

In experi ments ai med at structural d yna mics testing, it isrnoften required to precisel y contro l a multi-shake r s yste m inrnorde r to replicate the conditions a machine experiences duringrntypical operation mode. For that purpose one seek s to creat e arnspecifi c pattern of responses or forces motivated b y actualrnmeasured data. Another use of such tuning is f or diagn osticrnpurposes where certain forcing patterns a mplify hidden featuresrnof the dyna mic response. For lightl y-da mped structures that arernnor mally excited b y magnetic or electro- magnetic shakers, thisrntask appears to be di fficult, especiall y when high accurac y isrndesired. The excitation s yste m, under certain conditions,rncreates an inherent feedback bet ween the force and th e responsernand ofte n so me non-linearit y exist in the force path. In thisrnpape r, a s yste matic approach for auto matic tunin g the amplitudernand phase of a multi-shaker in an experi mental s yste m isrndeveloped . The method is particularl y use ful in the presence ofrnfeedback, mild non-linearit y and coupling bet ween the forcernand response. The usual approach is to use a linear mode l andrnto assu med that the non-linearit y is s mall, an approach tha t isrnvalid for identification of slightl y non-linear structures, butrnwhich fails when precise tuning of force s is based on thisrnidentified model. It is therefore suggested to use a generalrnlinearize d model , rathe r than a linear one, so that anyrnirregularities attributed to the non-linearit y can be handled.rnThroughou t the paper so me si mulated and experi mentalrnexa mples of tuning are sho wn. The interaction mechanismrnbet ween the shakers and the structure is discussed and modeledrnand an appropriate strateg y allo wing us to overco me thernde monstrated di fficulties, is presented.