Tuning of controller parameters by FCbT with stability constraints for non-minimum phase plants

We propose the controller tuning method considering closed-loop stability after tuning without the identified plant model. The methods are formulated as a model reference control problem in which the reference model is chosen by the user. In the case of non-minimum phase systems, the unstable zeros of the plant need to be included in the reference model to avoid unstable pole-zero cancellation. This paper proposes the model-free controller tuning for non-minimum phase plants estimating its unstable zeros by the flexible reference model in the process of parameter updates. The effectiveness of the proposed method is confirmed by simulation examples.