1,720,976 research outputs found
Towards sensorless observers for sinusoidal electric machines with variable speed and no mechanical model: A promising approach for PMSMs
No full textOne of the major issues in developing sensorless observers for AC Sinusoidal Machines, and for all kinds of Electric Machines, is to deal with variable speed relying only on the electromagnetic model, without using any mechanical information. In this paper, the case of Permanent Magnet Synchronous Machines is considered as first benchmark. A novel and promising design strategy is presented to develop a simple sixth-order observer for estimating rotor speed/position and magnetic flux amplitude, in the context of non-zero variable speed, with unknown constant sign and bounded derivative. This framework does not cover yet any arbitrarily-varying mechanical speed, but it goes far beyond the typical simplifying assumption of “slowly-varying speed”, which is actually meant as “constant speed” in the common theoretical analysis. In the proposed method, the rotation dynamics of the machine back-electromotive force is represented by means of the Lie Groups formalism, and no open-loop integration of stator voltages and currents is adopted. Lyapunov-like and Singular Perturbations techniques are then exploited to achieve regional practical asymptotic stability, with a very wide region of attraction. The mild limitations on such stability domain are carefully analyzed and discussed. Numerical simulations are provided to show the effectiveness of the proposed observer, under heavily variable mechanical speed. Finally, taking cue from the features of the presented approach, future steps are outlined in order to further weaken the restrictions on the speed variations and to extend the results to other electric machines
Constrained-Inversion MRAC: An Approach Combining Hard Constraints and Adaptation in Uncertain Nonlinear Systems”
No full textIn this work, we propose a design strategy for adaptive control of a class of nonlinear systems with input and state constraints. The systems of interest are required to have relative degree 1 and a convergent zero-dynamics: these properties cover a significant number of applications, after suitable changes of coordinates and with a proper selection of the regulated output. Through a design based on Barrier Lyapunov Functions, inspired by Explicit Reference Governors, we propose a feasible closed-form right-inverse unit that can be effectively interconnected with a nominal adaptive stabilizer, this way enforcing constraint satisfaction, while rejecting the effects of parametric uncertainties at the same time. The stabil- ity and feasibility properties of the control scheme are formally proven, and verified in a detailed numerical simulation
Global Observability Analysis of Aided-INS for UAVs Equipped with Visual Odometry Systems
No full textIn this work, observability properties of Inertial Navigation Systems aided with Global Navigation Satellite Systems and Visual Odometry are investigated and applied to the case of UAVs. A global analysis is carried out exploiting the concept of indistinguishable trajectories, that are characterized by solutions of Differential Algebraic Equations. A hybrid formulation is presented to combine two different indistin- guishable dynamics, which arise depending on vehicle speed. For particular scenarios commonly encountered in practice, explicit conditions on the system inputs are obtained and appropriately cast as persistency of excitation requirements. With the presented tools, the benefits from Visual Odometry in enhancing observability can be appreciated, in particular w.r.t. attitude and bias estimation, and useful practical indication on the kind of maneuvers making the system observable can be drawn. Assessment of the theoretical results is provided by means of realistic numerical simulations, tailored to the considered UAV application
A Computational-Effective Field-Oriented Control Strategy for Accurate and Efficient Electric Propulsion of Unmanned Aerial Vehicles
Full text linkIn this work, we introduce an easy-to-implement sensorless controller specifically designed for the regulation of the propellers of Unmanned Aerial Vehicles (UAVs). As motivation, we present a comparison of the usual motor control architectures, i.e., Field-Oriented Control (FOC) and Brushless DC (BLDC) control, with special attention to the typical back-ElectroMotive Force (back-EMF) shapes found in this application. In particular, we show that the adoption of sensorless FOC provides several advantages, both from the efficiency and the signal quality viewpoints, provided that accurate rotor position reconstruction is available. Therefore, a recently proposed observer is integrated into a nested FOC architecture, with formal stability guarantees and low computational effort, making the resulting strategy suitable for implementation in embedded computing systems. The algorithm is then compared experimentally to a sensorless BLDC controller and a high-end commercial drive, thus validating the previous results and showing effective time-varying speed tracking, as required for precise aggressive maneuvering. These features of efficiency, accuracy, and simplicity might prove instrumental in bolstering the introduction of a novel class of high-performance, robust UAV sensorless controllers in the forthcoming years
Adaptive Hybrid Control for Robust Global Phase Synchronization of Kuramoto Oscillators
Full text linkA distributed controller is designed for the robust adaptive global phase synchronization of a network of uncertain second-order Kuramoto oscillators with a leader system, modeled as an autonomous nonlinear exosystem that communicates the reference signals only to a subset of the oscillators. We propose an adaptive strategy, only assuming knowledge of upper bounds on the unknown oscillators parameters, that exploits a hybrid hysteresis mechanism to obtain global synchronization despite the well-known topological obstructions with the phases (which evolve on the unit circle). A distributed observer of the leader exosystem is key to overcoming these topological obstructions combined with the generic graph topology we consider. Leveraging the results of hybrid systems theory, including reduction theorems, Lyapunov techniques, and properties of ω-limit sets, we prove global convergence of the phases to the leader reference and robust global asymptotic stability of the closed-loop dynamics, despite the presence of an adaptive control law
Multirotor UAV flight endurance and control: The drive perspective
No full textA novel approach is proposed to compare Brushless DC control and Field Oriented Control performance in driving Permanent Magnet Synchronous Machines for multirotor UAVs, a particular class of small-size electrically-powered UAVs. Both power efficiency and output torque quality are analyzed in depth to carry out causes and consequences of control issues in both cases. Power losses and torque ripple contributions, due to driving techniques and converter non idealities, are decoupled and then exploited to show how large the torque oscillations are in case of Brushless DC control, and to highlight the higher efficiency given by Field Oriented Control, which can be exploited for enhancing the flight endurance
Integrated Control of Motion and Contactless Power Transfer for Doubly-Fed Induction Machines in Complex Rotary Apparatuses
No full textA novel control solution for Doubly-Fed Induction Machines is proposed to enable new applications of such kind of machines. This strategy guarantees a fully decoupled motion control and contactless power transfer between stator and rotor, by using controlled inverters on both stator and rotor side. For large and complex rotary apparatus with relevant electric loads and actuators placed on-board the mobile part, the proposed solution allows to exploit direct-drive versions of Doubly-Fed Induction Machines for both moving and feeding independently the rotating part, where the rotor-side converter has to be hosted. Power transfer is attained through two different working principles in order to achieve decoupling from the torque references and to suitably deal with voltage saturations on power converters. Global asymptotic stability proof is provided for this control strategy. Simulation results are reported in order to validate the promising theoretical developments
BE-WoodEN: innovative low carbon solutions in wood construction through the NEB approach
No full textThe European Green Deal has emphasised the importance of circularity in building and construction, as a means to reduce waste, improve sustainable materials and reduce GHG emissions. The main objective of the project presented is to promote decarbonisation and improve circularity by proposing training and innovative solutions suitable for large building stocks, mainly social housing, overcoming the barriers in the use of wood (cultural, technical, economic and regulatory, which hinder promotion of the wood supply chain in several countries). The project is based on New European Bauhaus values, and its implementation follows the principles expressed by the NEB Compass, increasing knowledge and skills on the topic, and promoting a new way of design following a participatory approac
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