An efficient algorithm for vibration suppression to meet pointing requirements of optical payloads

Abstract

For several future imaging spacecraft, vibration isolation and suppression of its optical payloads have become a challenging problem. These spacecraft have increased performance requirements for the payload, resulting in increased fine steering and vibration isolation requirements. The vibration sources on the spacecraft, however, are increased due to the new large flexible structures and addition of rotating devices. One promising way to address both issues is through the Stewart platform. By using a hexapod with six actuated struts, it is possible to achieve both fine pointing and vibration control. Traditional vibration control algorithms rely on the knowledge of the plant and are usually computationally intensive. This paper applies a computationally efficient vibration control to the Stewart hexapod problem. This algorithm does not rely on the knowledge of the plant other than to find the adaptation rate coefficient and performs well on highly non-linear plants. A convergence analysis is presented. Results are shown for a voice-coil actuated hexapod.

Development of a Hexapod Laser-based Metrology System for Finer Optical Beam Pointing Control

“…It makes use of a set of three Eddy current sensors to determine the tip and tilt angle for pointing, whereas the other motion variables, including the rotation about the vertical axis of symmetry, are assumed to be zero. Pointing experiments using this measurement system has been done with reasonable results 2,3,4 . However, it is observed that the sensors can easily be influenced by environment magnetic noise and the Plexiglas posts of the setup are not rigid enough to keep away from the influence of vibrating disturbances.…”

Multiple-degree-of-freedom sinusoidal vibration generation based on a hexapod platform

“…The ADC method 24 was specially developed for sine vibration control of SISO system, as shown in Figure 4. Since the expected output signal d ( t ) can be constructed with reference sine and cosine signal…”

“…where w 1 , w 2 are tunable parameters, and the iteration equation based on LMS algorithm for w 1 , w 2 is 24…”

An active hybrid control approach with the Fx-RLS adaptive algorithm for active-passive isolation structures

“…The precision of the optical equipment on spacecraft is continuing to increase, which has led to improvements in the performance of vibration isolation devices. Additionally, due to the introduction of a new flexible structure and rotating device, vibration sources have become increasingly prominent [1]. Although a passive isolation system offers a simple and reliable means of protecting precision equipment from a vibration environment, active vibration isolation has significantly improved the performance of such systems.…”