Method for measuring frequency response function of vibrating structure in large noise environment
The invention relates to a method for measuring frequency response function of a vibration structure in loud-noise environment, comprising the following steps: a linear swept-frequency signal is adopted as an excitation signal and acceleration response signals of the structure vibration is filtered in a fractional order Fourier domain by fractional order Fourier transformation, so that effect of noise in non-stationary process can be lessened, and measuring accuracy of the frequency response function is improved. Simultaneously, in the method, two groups of experiment signal data are expressed as one group of plural experiment signal data so as to avoid effect of superposition of two signal components, and only one-time filtering is needed to finish noise removal treatment of the two groups of the experiment signal data so as to improve noise removal effect and operating speed.
The purpose of this note is to document some work done as part of the effort directed at designing and simulating a bunch-by-bunch feedback system to control longitudinal coupled bunch instabilities in the B-factory. In particular, I discuss the ring model used in the simulation program developed to study this feedback system. Basically the simulation is a simple tracking program in which the rf drive voltage, the wakefields due to all the bunches, the synchrotron radiation losses, and the kicks applied to the bunches by the bunch-by-bunch feedback are all modelled as voltages applied at a single, discrete point in the ring. The computation of the bunch-by-bunch feedback voltages may of course be done by any desired algorithms. An example and discussion of the general behavior without bunch-by-bunch feedback is given at the end of this report.