Performance analysis of periodic sampled-data H2 and mixed H2/H∞ control

This paper uses a time domain approach for the analysis of H 2 performance of periodically time varying sampled-data controllers for the rejection of H 2 disturbances. For the purpose of the analysis, linear time invariant (LTI) controllers are distinguished from linear periodically time varying (LPTV) controllers. For control of an LTI plant, it is shown that the time varying dynamics of the LPTV controller deteriorates the closed loop system H 2 performance and an LTI controller can be found to provide strictly better H 2 control of the system. For H 2 /H ∞ control, it is shown that if a given LPTV controller meets an H ∞ constraint, the LTI controller will also meet the H ∞ constraint while giving superior H 2 performance.