Hinfinity control design for multivariable mechanical systems - Application to RLV reentry

During primary phases of projects characteristics of systems evolve significantly requiring easy and ecient control design and analysis methods for high level specification satisfaction. Analysis and control design methods that can easily be updated when specifications or characteristics are modified could be very useful engineering tools. In the general case of mechanical systems, performance specifications often consist in desired pulsation, damping ratios and degrees-of-freedom (d.o.f) decoupling. To meet such specifications an H1 standard problem based on the acceleration sensitivity function is proposed as a basic scheme. This standard problem can be used to analyze or design control laws taking into account new dynamic elements (actuators dynamics, navigation filter, ...) or additional specifications (roll-o). This scheme is applied on Reusable Launch Vehicle (RLV) during atmospheric reentry to design control laws and to determine the worst-case along the reentry trajectory.