The other is to stimulate the cantilever at itsfixed end with the signal measured from the tip-sample interaction change, inorder to eliminate the distance change caused by external vibration, so as torealize online vibration compensation.
It is proved by experiments that scanning rate (frequency) and numberof sampling points of SPM will directly influence the direction and distribution ofthe fringes (spatial periodical wave), generated by certain frequency externalvibration, on SPM image, which is the main form of SPM image distortion causedby external vibration.
Based on the principle of SAW linear superposition and signal orthogonalization,SAW information sensing model using SAW oscillator is founded in this paper with the mapping relation of environmental influence(ΔI) → variation of SAW velocity(Δν) → phase variation of SAW delay line phase variation(Δφ) → frequency variation of the oscillator(Δω).
It has a good ability to resist the disturbance from vibration outside the apparatus. It has simple constructure and high measuring sensitivity. The longitudinal resolution is 0. 4nm and lateral resolution is 1.72 μm.
The structural damage alarming method based on wavelet packet energy spectrum (WPES) for long-span cable-stayed bridges is presented through combination of ambient vibration test and wavelet packet analysis.
Damage localization under ambient vibration using changes in flexibility
Therefore, SHM methods based on ambient vibration have become important in civil engineering.
In this paper, an approach is proposed based on the Damage Location Vector (DLV) method to handle the ambient vibration case.
Recently, ambient vibration test (AVT) is widely used to estimate dynamic characteristics of large civil structures.
This paper puts foward a proposal for auto-orientation of a KDP crystal array and describes a microprocessor auto-orientation system which can auto-regulate the single piece of KDP crystal to its optimal matching direction. The control accuracy of the system E= +16.3. s. The system is able to track the change of the matching angle in real-time. It is able to compensate the influence of temperature drift and external vibration on the orientation.
In. this paper, an image plane holographic interferometer is presented. The reference beam and the object beam take a corumon path in the interferometer, the influence of external vibrations is eliminated and the coherent noise is reduced when the image plane hologram is reconstructed with white light.