1,721,000 research outputs found
A UGAS Sensorless Observer for Permanent Magnets Synchronous Machines including Estimation and Compensation of Dead-Times Effects
No full textIn this work, a novel sensorless observer is proposed for Permanent Magnet Synchronous Machines, formally dealing with stator voltage actuation non-idealities. Rotor speed, position and stator fluxes, as well as the unknown parameters of the voltage perturbations are reconstructed considering a fixed reference frame for both the machine and the voltage actuator non-linear effects. Stator currents and commands for the voltage actuator are assumed to be the only known signals. The estimation scheme is proven to be Uniformly Globally Asymptotically Stable by means of rigorous results from adaptive systems theory. The effectiveness of this solution is validated by realistic simulation tests, including a detailed model of the power converter. Discretization of the presented solution is addressed accurately. A comparison is provided to show the advantages of the proposed observer against a solution which does not adopt any mechanism to compensate for the mismatch between ideal and actuated stator voltages
A Hybrid Sensorless Observer for the Robust Global Asymptotic Flux Reconstruction of Permanent Magnet Synchronous Machines
Full text linkWe propose a hybrid sensorless observer for permanent magnet synchronous machines with global asymptotic stability guarantees. Exploiting the constraint of the rotor flux on a circle of unknown radius, we design an integrator system with periodic jumps triggered by a clock to generate a linear regression containing the flux estimation error. Then, a normalized projected gradient descent identifier provides the observer estimates. For the closed-loop system, it is shown that there exists a robustly globally asymptotically stable compact attractor, which, additionally, ensures zero estimation error if appropriate Persistency of Excitation (PE) conditions are satisfied. In this respect, sufficient conditions ensuring PE are provided for the angular speed and the clock period
Paul Bosso, A., Munus e potestas del parroco. Roma 2022, 290 pp.
No full textRecensión de la monografía: Paul Bosso, A., Munus e potestas del parroco, Roma 2022, 290 pp
Global Frequency Synchronization over Networks of Uncertain Second-Order Kuramoto Oscillators via Distributed Adaptive Tracking
No full textIn this work, we consider the problem of global frequency synchronization of a network of second-order Kuramoto oscillators, cast as a distributed tracking problem, in the sense that the reference synchronization frequency for the network is generated by an autonomous leader. The main contribution of this paper is to develop a novel control strategy for the problem of leader-follower frequency synchronization, by exploiting the adaptive control framework to cope with parametric uncertainties in the oscillators. These adaptive controllers (one for each system) are interconnected with a distributed observer, used to reconstruct the reference signal for the systems not directly connected to the leader. Adopting the Lie Groups formalism for the unit circle to globally characterize the phase dynamics, we show that synchronization is not hindered if the physical couplings are in part preserved. Stability of the closed-loop interconnection is analyzed with Lyapunov-like arguments and verified in a numerical simulation
Low-input accurate periodic motion of an underactuated mechanism: Mass distribution and nonlinear spring shaping
No full textThis work presents a control-oriented structural design approach for a 2-DOF underactuated mechanical system, with the purpose of generating an optimal oscillatory behavior of the end-effector. To achieve the desired periodic motion, we propose to adjust the dynamic response of the mechanism by selecting its mass distribution and the characteristic of a nonlinear spring. In particular, we introduce a two-step optimization strategy to shape the system's zero dynamics, obtained via input-output linearization. The first part of the procedure aims to minimize the root-mean-square value of the input torque by optimizing the mechanism's mass distribution. In this context, we show that a perfect matching with the desired trajectory can be reached by assuming the ability to design an arbitrary shape of the system's elastic properties. Then, in order to favor a simpler physical implementation of the structure, we dedicate the second optimization step to the piecewise linear approximation of the previously defined stiffness characteristic. The proposed procedure is finally tested in detailed numerical simulations, confirming its effectiveness in generating a complex and efficient periodic motion
La criomacerazione con neve carbonica abbinata alla tecnica dell'estrazione differita degli antociani
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Periodic motion optimization for an underactuated mechanical system through synergistic structure-control design
No full textIn this work, we present the integrated structure-control design of a 2-DOF underactuated mechanical system, aiming to achieve a periodic motion of the end-effector. The desired behavior is generated via input-output feedback linearization, followed by structural optimization of the zero dynamics. Inspired by recent works on the control-oriented design of multibody systems, we define a simulation-based optimization problem where the response of the mechanism is shaped through relevant structural parameters. In particular, adjusting the stiffness and the mass distribution of the system, we match the periodic reference with a specific orbit of the zero dynamics, while also penalizing the linearizing input. With the adoption of the proposed strategy, we show that it is possible to reach a desirable trade-off between input energy reduction and periodic motion accuracy. Once an optimal trajectory of the zero dynamics is found, the control design is completed with established orbital stabilization techniques, ensuring a robust oscillatory behavior
Robust Global Asymptotic Stabilization of Linear Cascaded Systems With Hysteretic Interconnection
Full text linkWe address the problem of setpoint regulation for cascaded minimum-phase linear systems interconnected through a scalar hysteresis, modeled as a Prandtl-Ishlinskii operator. Employing well-posed constrained differential inclusions to represent the hysteretic dynamics, we formulate the control problem in terms of stabilization of a compact set of equilibria depending on the hysteresis states. For our design, we firstly consider a proportional-integral controller for linear systems with hysteretic input, and provide model-free sufficient conditions based on high-gain arguments for closed-loop stability. Then, the controller is dynamically extended to obtain an inversion-free stabilizer of the overall cascade. For the presented schemes, we prove robust global asymptotic stability of a compact set that ensures setpoint regulation, regardless of the hysteresis states
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