GB1470000A - Vibration control system - Google Patents

Abstract

1470000 Automatic control TIME DATA CORP 14 June 1974 [19 Oct 1973] 26523/74 Heading G3N The actual spectrum of a frequency domain representation of a specimen being subjected to vibration is compared with a reference spectrum and a randomized control signal derived which is converted to a continuous signal for controlling a vibration-inducing system. As shown, a specimen 11 is vibrated by an apparatus 10 and the vibrations sensed by an accelerometer 12. The acceleration signals are fed through an A-to-D converter 14 to a processor 16 by which is derived, by use of Fourier transforms, a frequency domain representation of the signals which is converted to a power-spectraldensity PSD and presented as a frame, a finite sample of information, of a number of digital words, each word being formed of a plurality of bits. The actual PSD is compared with a reference PSD in a comparator 18 and stored in a comparator 20. The PSD comparison is multiplied in a device 22 with quadrature digital outputs of a random, or pseudo-random, angle generator and the resultant signals, through a frequency domain-to-time domain converter 26, presented as frames of control data to a randomization unit 28, which produces a plurality of frames of driving signal for the apparatus 10 from each frame of control data. A windowing means may be used to smooth the transition between frames. The comparator 22 and multiplier 22 may be embodied, separately or together, by a digital computer.