TY - GEN A1 - Rueda-Escobedo, Juan G. A1 - Moreno, Jaime A. A1 - Schiffer, Johannes T1 - L2-Gain Tuning for the Gradient Descent Algorithm in the Presence of Disturbances T2 - 2022 European Control Conference (ECC) N2 - Due to its simplicity and inexpensive computation, the gradient descent algorithm is one of the most used tools in adaptive control and system identification. Although it has been studied for decades, little has been achieved in terms of tuning methods in the presence of disturbances. One of the main difficulties in its analysis is the time-varying nature of the algorithm. In this work, we contribute in such direction by providing LMI tools for tuning the gradient descent algorithm gain such that a guaranteed upper bound on the L2 -gain with respect to parameter variations and measurement noise is achieved. Two academic examples are provided to illustrate the efficient application of the method. KW - Upper bound KW - Gain measurement KW - Minimization KW - robustness KW - system identification KW - noise measurement Y1 - 2022 UR - https://ieeexplore.ieee.org/document/9838051 SN - 978-3-9071-4407-7 U6 - https://doi.org/10.23919/ECC55457.2022.9838051 SP - 1610 EP - 1616 PB - IEEE CY - Piscataway ER - TY - GEN A1 - Rueda-Escobedo, Juan G. A1 - Ushirobira, Rosane A1 - Efimov, Denis A1 - Moreno, Jaime A. T1 - Gramian-based uniform convergent observer for stable LTV systems with delayed measurements T2 - International Journal of Control Volume N2 - In this work, an observer for a linear time-varying system with delayed measurements is developed. The delay is assumed to be unknown, bounded, and it can be time-varying with no restriction on its rate of change. The observer uses auxiliary signals related to the constructibility Gramian of the system and it contains nonlinearities that provide a uniform fixed-time convergence to a bounded region in the estimation error coordinates. This means that the convergence time can be bounded by a positive constant which is independent from the initial conditions and the initial time. This property is new for the addressed class of systems. The ultimate bound of the estimation error depends on the maximum difference between the nominal output and the delayed one, and not directly on the delay size or its time derivative. These properties are illustrated in a numerical simulation. Y1 - 2020 U6 - https://doi.org/10.1080/00207179.2019.1569256 SN - 0020-7179 SN - 1366-5820 VL - 93 IS - 2 SP - 226 EP - 237 ER - TY - GEN A1 - Gustavo-Escobedo, Juan A1 - Moreno, Jaime A. A1 - Schiffer, Johannes T1 - Finite-Time Estimation of Time-Varying Frequency Signals in Low-Inertia Power Systems T2 - 8th European Control Conference (ECC) N2 - The ongoing and unprecedented transformation of power systems leads to a reduction in the number of conventional power plants, which are the classical actuators of the grid. In addition, this development results in a decreasing system inertia, which is expected to yield faster frequency dynamics. Therefore power-electronics-interfaced units have to take over system control tasks and, in particular, frequency control. For this purpose, accurate and fast estimation algorithms for time-varying frequency signals are needed. Motivated by this fact, we propose a time-varying parameter estimator and a tuning criterion, which for sufficiently small initial estimation errors allows to reconstruct the time-varying frequency signal of a symmetric three-phase waveform in finite time. The proposed estimator is derived by using a time-varying version of the super twisting algorithm and its performance is illustrated via numerical examples. KW - Power Systems, Frequency Signals, Finite-Time Estimation Y1 - 2019 U6 - https://doi.org/10.23919/ECC.2019.8795926 SP - 2108 EP - 2114 ER - TY - GEN A1 - Rueda-Escobedo, Juan G. A1 - Moreno, Jaime A. T1 - Strong Lyapunov Functions for Two Classical Problems in Adaptive Control T2 - Automatica N2 - Strong Lyapunov functions for two classical problems in adaptive control and parameter identification are presented. These Lyapunov functions incorporate in their structure the classical persistency of excitation conditions, allowing to show global uniform asymptotic stability of the associated adaptive systems under sufficient and necessary conditions. Y1 - 2021 U6 - https://doi.org/10.1016/j.automatica.2020.109250 VL - 124 ER - TY - GEN A1 - Rueda-Escobedo, Juan G. A1 - Moreno, Jaime A. A1 - Schiffer, Johannes T1 - Design and Tuning of the Super-Twisting-Based Synchronous Reference Frame Phase-Locked-Loop T2 - 2022 IEEE 61st Conference on Decision and Control (CDC) ; December 6-9, 2022, Cancun, Mexico N2 - The worldwide transition to climate-friendly energy systems entails the substitution of conventional energy generation based on synchronous generators by renewable energy sources based on power electronics. As a consequence, the overall inertia of the grid decreases, resulting in high volatility of the frequency and posing new challenges for the estimation of the latter quantity. To address this problematic, in the present paper a phase-locked-loop (PLL) based on the super-twisting algorithm is considered for the estimation of the phase angle and time-varying frequency of a symmetric three-phase signal. A rigorous proof of the algorithm’s exact convergence in the presence of a fast-varying frequency together with tuning rules for its gains are derived by means of Lyapunov theory. Additionally, an estimate of the region of attraction is provided. The effectiveness of the proposed tuning method is illustrated in numerical simulations, while comparing its performance against a standard synchronous reference frame PLL. Y1 - 2022 UR - https://css.paperplaza.net/conferences/conferences/CDC22/program/CDC22_ContentListWeb_3.html ER - TY - GEN A1 - Rueda-Escobedo, Juan G. A1 - Sbarciog, Mihaela A1 - Moreno, Jaime A. A1 - Van Impe, Jan A1 - Wouwer, Alain Vande T1 - Robust State and Input Estimation with Enhanced Convergence Rate for Monitoring Anaerobic Digestion T2 - Journal of Process Control N2 - In this study, an observer for estimating the state and unknown inputs is proposed for monitoring anaerobic digestion processes. This estimator is based on a dynamic model considering acidogenesis and methanogenesis, and consists of three sub-observers: (a) a gramian-based fixed-time convergent observer for the inlet chemical oxygen demand (COD) and the acidogenic bacteria population, (b) an asymptotic observer for the methanogenic bacteria population, and (c) a super-twisting observer for systems with time-varying parameters to estimate the inlet volatile fatty acid (VFA) concentration. These sub-observers can be designed independently, which greatly simplifies the tuning process. Proofs of convergence are developed and simulation tests show the performance of the estimation scheme as compared to classical extended Kalman filtering. Y1 - 2022 UR - https://www.sciencedirect.com/science/article/pii/S0959152422001421 U6 - https://doi.org/10.1016/j.jprocont.2022.07.014 SN - 0959-1524 VL - 117 IS - 4 SP - 169 EP - 180 ER -