A MODELING TECHNIQUE FOR ACTIVE CONTROL DESIGN STUDIES WITH APPLICATION TO SPACECRAFT MICROVIBRATIONS

Microvibrations, at frequencies between 1 and 1000 Hz, generated by on board equipment, can propagate throughout a spacecraft structure and affect the performance of sensitive payloads. To investigate strategie s to reduce these dynamic disturbances by means of active control syst ems, realistic yet simple structural models are necessary to represent the dynamics of the electromechanical system. In this paper a modelin g technique which meets this requirement is presented, and the resulti ng mathematical model is used to develop some initial results on activ e control strategies. Attention is focused on a mass loaded panel subj ected to point excitation sources, the objective being to minimize the displacement at an arbitrary output location. Piezoelectric patches a cting as sensors and actuators are employed. The equations of motion a re derived by using Lagrange's equation with vibration mode shapes as the Ritz functions. The number of sensors/actuators and their location is variable. The set of equations obtained is then transformed into s tate variables and some initial controller design studies are undertak en. These are based on standard linear systems optimal control theory where the resulting controller is implemented by a state observer. It is demonstrated that the proposed modeling technique is a feasible rea listic basis for in-depth controller design/evaluation studies. (C) 19 97 Acoustical Society of America. [S0001-4966(97)02510-1] PACS numbers : 43.40.Dx, 43.40.Vn [CBB].