Stable controller reduction for sampled-data systems

Two problems of stable controller reduction for sampled-data systems with consideration of the inter-sample behaviors, namely digital controller reduction and direct reduced order discretization are investigated. Both problems can be reduced to problems of open-loop sampled-data model reduction with hybrid weights. Hankel-norm approximation and balanced truncation for sampled-data systems are used to solve the problem of digital controller reduction and their relation to the L₂ induced norm equivalent discrete-time system is investigated. The problem of direct reduced order discretization can be solved by dealing with an equivalent discrete-time system with special weights