In this note, robust stabilization and tracking performance of operator based nonlinear feedback control systems are studied by using robust right coprime factorization. Specifically, a new condition of robust right coprime factorization of nonlinear systems with unknown bounded perturbations is derived. Using the new condition, a broader class of nonlinear plants can be controlled robustly. When the spaces of the nonlinear plant output and the reference input are different, a space change filter is designed, and in this case this note considers tracking controller design using the exponential iteration theorem.

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In this brief, an adaptive nonlinear sensorless control for an uncertain miniature pneumatic curling rubber actuator is considered using passivity and the robust right coprime factorization approach. Specially, based on the robust right coprime factorization approach, robust stability is guaranteed and passivity is realized simultaneously. Then, the adaptive control system is designed for tracking performance. Support vector regression is proposed to estimate the output for avoiding the use of a sensor. Finally, the experimental setup is shown and the experimental results are provided to show the effectiveness of the proposed scheme.

In this paper, operator-based robust control for nonlinear uncertain system is considered by using robust right coprime factorization approach. In details, the effects from uncertainties for nonlinear uncertain systems are analyzed through internally stable control design. For the stabilizing system, an internal model control (IMC) like operator-based control design is proposed. Based on the proposed design scheme, the effect from uncertainties is eliminated. By using operator theory-based approach, the system is robustly stable and the desired tracking performance can be realized. Finally, the effectiveness of the proposed design scheme is demonstrated by a simulation example. Note to Practitioners-Robust stability and tracking problems are two well-known topics in the field of control, which play an important role in real application and attract the researchers' attention all the time. Especially, these issues on nonlinear systems still remain challenging owing to complexity and the nonlinear characteristic property. Another challenging issue in nonlinear control is the effects from uncertainties. Motivated by these issues, robust control design by using operator theoretic-based approach has caused for concern owing to its effectiveness in dealing with nonlinearity and uncertainties. This paper provides a survey of the research in the above issues that would help practitioners in controlling nonlinear uncertain systems and in understanding the advantages of operator-based approach.