提高运载火箭模态频率预示精度的方法与模型修正策略

A Method for Improving the Accuracy of Modal Frequency Prediction of Launch Vehicles and Corresponding Model Updating Strategy

针对运载火箭质量变化后模态参数预示问题,提出火箭有限元模型修正以振型吻合为主的修正策略和提高模态频率预示精度的频率补偿算法。通过理论分析指出,运载火箭模型修正频率误差对飞行器质量变化的灵敏度主要取决于振型吻合程度,在有限元模型修正不能同时兼顾频率与振型时,可以适当放宽频率修正误差,确保振型的一致性,然后在利用修正模型预示质量变化后的火箭模态频率时进行误差补偿即可很大程度上消除修正误差,确保频率预示精度。通过算例研究表明:采用补偿算法可以不同程度地消除频率修正误差,而补偿效果与振型的吻合程度有直接关系,验证了提出模型的修正策略的正确性与频率补偿方法的有效性。

The modal parameters prediction of launch vehicles with reference counterparts that have different mass characters is investigated.A FE model updating strategy of mode shape priority and a method of modal frequency compensation to ensure modal frequency prediction accuracy is proposed.It is shown that,the sensitivity of relative frequency difference to the elements of mass matrix oppositely depends on the accuracy of mode shape of the updated FE model.Therefore,when one cannot get a FE model with dual satisfaction of modal frequencies and mode shapes during model updating,it is wise to weight the mode shapes more to achieve high mode shape matching accuracy firstly.Then by applying the proposed frequency compensation technique in modal parameters prediction of the new plant with different mass,one can obtain satisfied precision of modal frequencies.At the end,a simulation example is carried out to demonstrate the presented strategy and method.The simulation results indicated that,the frequency compensation method could eliminating the prediction error to varying degrees,the less discrepancies in mode shapes the better precision in frequency prediction.These results validate the correctness and effectiveness of proposed model updating strategy and modal frequency compensation method.