Mechanical vibration system and control method with limited displacement

A vibration system for producing randomized mechanical oscillations with limited displacement, comprising:

• a vibration generator driven by an analog drive signal;
• at least one vibration-sensing transducer for continuously producing an output signal representative of mechanical oscillations from the vibration generator;
• an analog-to-digital converter coupled to the sensing means to convert the output signal into a digital control signal;
• a computer data processor coupled to the analog-to-digital converter to receive the digital control signal and programmed with stored routines so as to operate upon the control signal to generate a digital drive output computed to produce randomized mechanical oscillations from the vibration generator such that the randomized mechanical oscillations are characterized by having a specified frequency spectrum and an amplitude distribution, the computing of the digital drive output carried out by the computer data processor including steps of;
• (a) transforming both the digital control signal and a digital drive signal into frequency domain to obtain frequency spectra of the respective control and drive signals,
• (b) calculating an inverse frequency response function from the frequency spectra of both the vibration and drive signals,
• (c) adjusting the inverse frequency response function with a target profile that represents a desired spectral content of the vibration from the device so as to obtain a preliminary drive spectrum,
• (d) independently modifying higher frequency and lower frequency components of the preliminary drive spectrum, including combining the higher frequency components with components of a randomized phase and converting the randomized signal back into time domain to obtain a higher-frequency time waveform, and modifying the lower frequency components by applying the lower frequency components to a narrowband time waveform having a low frequency range that is swept in time over the lower frequency components then converting the modified lower frequency components into time domain to obtain a lower frequency time waveform, and
• (e) combining both the higher-frequency and lower-frequency time waveforms together to obtain the digital drive signal;
• and
• a digital-to-analog converter coupled to the computer data processor to convert the digital drive signal into the analog drive signal that drives the vibration generator.