The integration of advanced active and passive structural noise control methods

This paper reports on an investigation into the feasibility of using active and passive means of vibration control in aerospace structures. In particular, attention is focused on controlling vibration transmission through light weight satellite structures at medium frequencies. The initial structure under test here is a 4.5-meter long satellite boom consisting of 10 identical bays with equilateral triangular cross sections. This structure is typical of those that might be used in space telescopes, space stations or synthetic aperture radar systems. Such a structure is typically used to support sensitive instruments in precise alignments spaced tens of metres apart. While a great deal of work has been done on this problem at low frequencies, relatively little has been achieved to date at medium frequencies (here taken to be between 150 Hz and 250 Hz). Nonetheless, this is of importance to new space missions. Using the techniques described here, an overall reduction in vibration transmission of 31.0 dB is achieved in an essentially undamped structure using passive means alone. The amounts of attenuation achievable for active control with one, two and three actuators are found to be 15.1 dB, 26.1 dB and 33.5 dB, respectively. With the combined passive control (using 10% geometric deviations) and active control (using three actuators) an overall reduction of 49.5 dB is achievable in practice.