The Impact Of Noise On The Square Pyramid Grid Structure Of The Sensor Arrangement

In recent years, large span space structures have been developed rapidly in large span public buildings and civil facilities. It has many characteristics, such as light weight,reasonable structure, beautiful shape, good mechanical performance, etc.. However, with using time continue, the structural damages inevitably emerged and seriously these can lead to many accidents. To solve these problems, the structural health monitoring began.Now, the structural health monitoring often adopted dynamics testing, while sensors’ placement is an essential problem to obtain dynamics signals. Considering the restriction of the field condition and economic cost, it is impossible to setting so many sensors on the structure. At the same time, noise inevitably effect testing signals. Therefore, with noise,laying the limited number of sensors and obtaining the effective damage information are the key problems to realize dynamics testing. In this paper, the following aspects of the research were carried out, and the corresponding conclusions were drawn.1) Because of the inconsistencies between the modal observability and damage identification of the grid structure, the results on sensors’ placement are different.Considering the characteristics on sensors’ placement, a coordinated Fisher information matrix and the variance method(namely Modified variance method) are used in this method. In this method, the Fisher information matrix was established bases on the relationship between structural response and vibration mode and damage sensitivity. And the target optimization algorithm is based on the coordination of Fisher information matrix2- norm.Based on the structural dynamic response sensitivity and variance method, the local maximum value of the variance function is used as a measure of the optimal number of structure sensor. So the sensor placement is obtained by using the Fisher information matrix.2) To show the validity and advantage of these methods, three different methods(EI method, Variance method and modified variance method) were contrasted to detect damages on a square pyramid space grid structure.3) The effects of noises on the sensors’ placement were considered. Firstly some random white noise was obtained by Matlab tool. Next, three methods are used to study the sensors’ placement with noise. Comparison the sensors’ placement before and after adding noise, the results show that noise can influence the sensors’ placement and the modified variance method has good noise robustness.