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In this paper, we propose a new robustness notion that is applicable for certifying systems' safety with respect to external disturbance signals. The proposed input-to-state safety (ISSf) notion allows us to certify systems' safety in the presence of the disturbances which is analogous to the notion of input-to-state stability (ISS) for analyzing systems' stability., 9 pages, pre-print submitted to Automatica

In this paper, we study robustness analysis of systems' safety with respect to external input (or disturbance) signals. To this end, we introduce a new notion of input-to-state safety (ISSf) which allows us to quantify the systems' safety robustness, in the same way as the application of input-to-state stability (ISS) notion for analyzing robustness of systems' stability. In particular, ISSf prescribes the relationship between the evolution of state distance to the unsafe set with the initial conditions and the bounded external input signals. Finally, we discuss how to combine this notion with ISS for analyzing the robustness of both systems' stability and safety.

We propose a novel nonlinear control method for solving the problem of stabilization with guaranteed safety for nonlinear systems. The design is based on the merging of the well-known Control Lyapunov Function (CLF) and the recent concept of Control Barrier Function (CBF). The proposed control method allows us to combine the design of a stabilizing feedback law based on CLF and the design of safety control based on CBF(s); both of which can be designed independently. Our proposed approach can also accommodate the case of multiple CBFs which correspond to multiple different sets of unsafe states. Lastly, the efficacy of the proposed approach is demonstrated in the simulation results on the stabilization of a nonlinear mechanical system and on the navigation of a mobile robot.

In this paper, we present a novel notion of input- to-state safety (ISSf) for general nonlinear systems which can be useful for certifying system’s safety under the influence of external bounded input (or disturbance) signals. We provide sufficient conditions for ISSf using barrier function/certificate which are analogous to the input-to-state stability Lyapunov function.