An indirect mixed-sensitivity approach to microgravity vibration isolation: the exploitation of kinematic coupling in frequency-weighting design-filter selections

The isolation systems planned for use with the International Space Station have been appropriately modeled using relative position, velocity, and acceleration states. In theory, frequency-weighting design filters can be applied to these state-space models, in order to develop optimal H₂ or mixed-norm controllers with desired stability and performance characteristics. In practice, however, the kinematic coupling among the various states can lead through the associated frequency-weighting-filters, to conflicting demands on the Riccati design “machinery”. In addition, kinematic coupling can result in a redundancy in the demands imposed by the frequency weights. This paper suggests a rational approach to the assignment of frequency-weighting design filters, in the presence of the kinematic coupling among states that exists in the microgravity vibration isolation problem