Proposal of NCbT guaranteeing closed-loop stability and stability margins

The Noniterative Correlation-based Tuning (NCbT) is known as one of the data-driven controller design methods. The NCbT guarantees closed-loop stability based on the small-gain theorem, which is a sufficient condition for closedloop stability. As the result, the designed control performance might be conservative. This paper proposes the new stability constraint based on the Nyquist stability criterion to improve conservativeness for control performance. By improvement of conservativeness, the control system could reduce the stability margins, gain margin and phase margin. In order not to achieve low stability margins, the constraint for stability margin is additionally proposed. Since the gain and the phase margins are still commonly used indices for stability margins in industries, the direct designation of the gain and the phase margins in data-driven approach is highly appreciated. The effectiveness of the proposed constraints for stability and stability margins are confirmed by numerical simulations. ©. 2019 The Institute of Electrical Engineers of Japan