(242d) Performance Assessment for Completely Unknown Siso and Mimo Systems Based on Gain and Phase Margins Using Modified Relay Feedback

A performance assessment procedure for single-input-single-output (SISO) and multi-input-multi-output (MIMO) systems based on modified relay feedback test is proposed in this paper. The well-known robustness measurements, gain and phase margins, are first used to assess the robust stability of the control systems. Furthermore, gain and phase margins are related to the control performance, in terms of integral of the absolute value of the error (IAE), for performance assessment. The proposed method can on-line estimate the gain and phase margins for systems with both unknown controller parameters and process dynamics by a modified relay feedback scheme. The estimated results can be used to indicate the appropriateness of the controller parameters. When the retuning of controller is found necessary, a similar procedure can be applied to tune the controller based on specifications of gain and phase margins. Performance assessment and controller design can be done simultaneously, which ensures a good performance of the control system. The proposed modified relay feedback scheme embeds an additional delay between the relay and controller, where the delay has to be adjusted to meet a criterion. An on-line algorithm is thus presented to make the delay converge to its target value efficiently. Several illustrative simulations are used to verify the effectiveness of the proposed method.