Loopshaping for Robust Performance

Robust performance is said to be achieved if the performance specifications are met for all plants in a specified set. Classical loopshaping was developed decades ago to design for robust performance for single-loop systems with simple uncertainty and performance specifications. Specifications are often not so simple-multiple real parameter variations are not handled by classical loopshaping, for example. Also, it is important for multivariable systems that uncertainty may be present at different locations, for example, actuator uncertainty is located at the input of the plant whereas sensor uncertainty is located at the output of the plant. In this work classical loopshaping is extended to multiple parametric and unmodelled dynamic uncertainty descriptions, to multiple performance specifications, and to the design of decentralized controllers. The authors refer to this more general loopshaping technique as robust loopshaping . Robust loopshaping is applied to a coupled mass-spring problem studied by numerous researchers.