[
    {
        "id": "authors:3b3tb-r2g71",
        "collection": "authors",
        "collection_id": "3b3tb-r2g71",
        "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220714-194256328",
        "type": "monograph",
        "title": "Stability and Safety through Event-Triggered Intermittent Control with Application to Spacecraft Orbit Stabilization",
        "author": [
            {
                "family_name": "Ong",
                "given_name": "Pio",
                "orcid": "0000-0002-9665-1320",
                "clpid": "Ong-Pio"
            },
            {
                "family_name": "Bahati",
                "given_name": "Gilbert",
                "clpid": "Bahati-Gilbert"
            },
            {
                "family_name": "Ames",
                "given_name": "Aaron D.",
                "orcid": "0000-0003-0848-3177",
                "clpid": "Ames-A-D"
            }
        ],
        "abstract": "In systems where the ability to actuate is a scarce resource, e.g., spacecrafts, it is desirable to only apply a given controller in an intermittent manner--with periods where the controller is on and periods where it is off. Motivated by the event-triggered control paradigm, where state-dependent triggers are utilized in a sample-and-hold context, we generalize this concept to include state triggers where the controller is off thereby creating a framework for intermittent control. Our approach utilizes certificates--either Lyapunov or barrier functions--to design intermittent trigger laws that guarantee stability or safety; the controller is turned on for the period for which is beneficial with regard to the certificate, and turned off until a performance threshold is reached. The main result of this paper is that the intermittent controller scheme guarantees (set) stability when Lyapunov functions are utilized, and safety (forward set invariance) in the setting of barrier functions. As a result, our trigger designs can leverage the intermittent nature of the actuator, and at the same time, achieve the task of stabilization or safety. We further demonstrate the application and benefits of intermittent control in the context of the spacecraft orbit stabilization problem.",
        "doi": "10.48550/arXiv.arXiv.2204.03110",
        "publisher": "arXiv",
        "publication_date": "2022-04-06"
    },
    {
        "id": "authors:jz2q3-n3386",
        "collection": "authors",
        "collection_id": "jz2q3-n3386",
        "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220714-194252464",
        "type": "monograph",
        "title": "Safe Backstepping with Control Barrier Functions",
        "author": [
            {
                "family_name": "Taylor",
                "given_name": "Andrew J.",
                "orcid": "0000-0002-5990-590X",
                "clpid": "Taylor-Andrew-J"
            },
            {
                "family_name": "Ong",
                "given_name": "Pio",
                "orcid": "0000-0002-9665-1320",
                "clpid": "Ong-Pio"
            },
            {
                "family_name": "Moln\u00e1r",
                "given_name": "Tam\u00e1s G.",
                "orcid": "0000-0002-9379-7121",
                "clpid": "Moln\u00e1r-Tam\u00e1s-G"
            },
            {
                "family_name": "Ames",
                "given_name": "Aaron D.",
                "orcid": "0000-0003-0848-3177",
                "clpid": "Ames-A-D"
            }
        ],
        "abstract": "Complex control systems are often described in a layered fashion, represented as higher-order systems where the inputs appear after a chain of integrators. While Control Barrier Functions (CBFs) have proven to be powerful tools for safety-critical controller design of nonlinear systems, their application to higher-order systems adds complexity to the controller synthesis process -- it necessitates dynamically extending the CBF to include higher order terms, which consequently modifies the safe set in complex ways. We propose an alternative approach for addressing safety of higher-order systems through Control Barrier Function Backstepping. Drawing inspiration from the method of Lyapunov backstepping, we provide a constructive framework for synthesizing safety-critical controllers and CBFs for higher-order systems from a top-level dynamics safety specification and controller design. Furthermore, we integrate the proposed method with Lyapunov backstepping, allowing the tasks of stability and safety to be expressed individually but achieved jointly. We demonstrate the efficacy of this approach in simulation.",
        "doi": "10.48550/arXiv.arXiv.2204.00653",
        "publisher": "arXiv",
        "publication_date": "2022-04-01"
    }
]