Design and performance assessment of a distributed vibration suppression system of a large flexible antenna during attitude manoeuvres

Abstract

One of the major needs of future Earth Observation satellites is to fulfil high demanding pointing requirements when using instrumentations supported by or mounted at the end of very large flexible truss structures. Those spacecraft often call for the capacity of performing fast and precise manoeuvres without exceeding deformation requirements related to their flexible parts. On-board mechanical disturbances can be generated by an attitude control equipment and pointing mechanisms. In this perspective, a network of smart actuators/sensors can be mounted on a passive structure to counteract undesired elastic vibrations. In this paper, the problem of micro-vibration control for a spacecraft equipped with a very large flexible antenna is addressed. The instrument is sustained by an active frame hosting an optimally distributed network of actuators and sensors dedicated to vibrations suppression. The fully coupled 3-D equations for a flexible spacecraft subjected to forces of the orbital environment are derived taking the presence of the smart materials into account. The 3-D flexible structure model is developed and validated via FEM formulation by using commercial codes. The model is then reduced to obtain a system to be easily handled by control systems algorithms. A placement strategy to identify the best location for vibration control devices is carried out by using Gramian-based techniques. Typical profiles of attitude manoeuvres are then simulated by applying a control torque while simultaneously suppressing unwanted vibrations. To achieve a high performance, feedback methods are implemented to coordinate the actuators and ensure that maximum tip displacement requirements are satisfied during operations.