Design for robustness using the μμ-synthesis applied to launcher attitude and vibration control

The M-V launch vehicle of Japan Aerospace Exploration Agency (JAXA) has successfully injected Japan's fifth X-ray space telescope “SUZAKU” into its low earth orbit in this past July. The attitude and vibration control algorithm of the M-V rocket used to be highlighted by its H∞H∞ robust stability since its first flight conducted in 1997. Beyond this, its robustness character has been further enhanced using the μμ-synthesis approach to get better robust characteristics not only in stability but in tracking performance under uncertainty of the system dynamics. The performance has been validated by the latest back-to-back successful flights of the vehicle: in May 2003 to directly inject Japan's first asteroid sample return spaceship “HAYABUSA” into the planned inter-planetary trajectory and in this past July to launch the telescope. The μμ-synthesis has been applied for the first time ever for Japan's launcher control beyond the reliable H∞H∞ design. The plant dynamics has an extremely high-order and unstable characteristics, thus the standard μμ-synthesis format cannot be directly applied. The paper gives a unique methodology to apply the theory to such a real high-order complicated system.