1,721,175 research outputs found
Estudio sobre el cáñamo, yute, formio, henequenágave, pita, sisal-ramio, palo borracho y caranday
No full textFil: Canciello, Antonio. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Buenos Aires, Argentina
Selective modal control for vibration reduction in flexible structures
No full textThe design of a controller for selective reduction of vibrations in flexible low-damped structures is presented. The objective of the active feedback control law is to increase damping of selected modes only, in frequency regions where a disturbance is likely to produce largest effect. Moreover, the stabilizing controller is required to be band-pass, in order to filter out high-frequency sensor noise and low-frequency accelerometer drift, and stable to increase robustness to uncertain parameters. The control design is based on the Inverse Optimal Design approach, through the solution of a matrix Stein equation, resulting in the solution of an optimal H∞ control problem. A grey-box identification approach of the authors is employed for obtaining the model from experimental data or from detailed Finite Element Model (FEM) simulators. The problem of optimal actuator/sensor location is also addressed. Detailed simulation results are provided to show the effectiveness of the strategy
H-infinity Strongly Stabilizing Bandpass Controllers for Selective Natural Modes Damping in Flexible Structures
No full textIn this paper by extending previous work of one of the authors the design of a MIMO H∞ feedback controller for flexible systems is proposed. The controller has some very desirable properties for applications related to noise and vibration reduction, since it has limited bandwidth, zero dc-gain and can selectively increase the damping of only some selected natural modes of the flexible structure. This characteristic turns out to be very useful when dealing with lightly damped structures forced by broadband disturbances. Since however the controller is not necessarily stable, by solving an LMI problem, a stable version of the controller is also obtained. The effectiveness of the proposed control strategies is shown on a detailed COMSOL FEM model
Supervised control of buck-boost converters for aeronautical applications
No full textRecent MEA (More Electric Aircraft) concepts require new approaches to design and management of the electric system onboard. Bidirectional Buck-Boost Converter Units (BBCU's) used like bridges between power buses with different voltage require intelligent supervisory control for autonomous selection of operating modes. In this paper at low-level, sliding manifold-based strategies are employed to track desired current references, or to recover from overload within a prescribed time. At a higher level, three working modes are defined, (Buck-, Boost- and Intermediate-Mode), and scheduled by a high-level supervisory strategy. Stability proofs of the overall strategy require estimates of the Region of Attraction (ROA) for each controller, that are discussed in the paper. A typical aeronautic scenario is presented, with standard operating conditions followed by two types of overloads (the second more severe than the first) and finally a return to standard condition. Detailed numerical simulations show the effectiveness of the proposed novel control strategy in terms of stability and performance of the smart converter
A Consensus-Based Current Sharing Algorithm for Energy Storage Systems: An Application to Aeronautic Microgrids
No full textMore Electric Aircraft (MEA) and All Electric Aircraft (AEA) require advanced autonomous electric Energy Management Systems (EMS) onboard the aircraft. The aircraft electric network can be considered as an islanded microgrid, and as such some approaches typical of the microgrid management can be used onboard the aircraft to design an effective EMS. In particular, distributed control with consensus techniques represents a promising approach due to the advantages in terms of reliability, computational simplicity and low-bandwidth requirement which are of great interest for implementation onboard. A consensus-based solution to the problem of coordinating and balancing several Energy Storage Systems (ESSs) coexisting in a generic aircraft architecture is proposed and analyzed. The proposed algorithm selects the current setpoints for each ESS according to their state of charge while ensuring safety of operations. Theoretical results and detailed simulations show the effectiveness of the proposed approach
Control of Energy Storage Systems for Aeronautic Applications
No full textFuture aircraft will make more and more use of automated electric power system management onboard. Different solutions are currently being explored, and in particular the use of a supercapacitor as an intelligent energy storage device is addressed in this paper. The main task of the supercapacitor is to protect the electric generator from abrupt power changes resulting from sudden insertion or disconnection of loads or from loads with regenerative power capabilities, like electromagnetic actuators. A controller based on high-gain concepts is designed to drive a DC/DC converter connecting the supercapacitor to the main electric bus. Formal stability proofs are given for the resulting nonlinear system, and strong robustness results from the use of high-gain and variable structure control implementation. Moreover, detailed simulations including switching devices and electrical parasitic elements are provided for different working scenarios, showing the effectiveness of the proposed solution
Robust Control of Aeronautical Electrical Generators for Energy Management Applications
No full textA new strategy for the control of aeronautical electrical generators via sliding manifold selection is proposed, with an associated innovative intelligent energy management strategy used for efficient power transfer between two sources providing energy to aeronautical loads, having different functionalities and priorities. Electric generators used for aeronautical application involve several machines, including a main generator and an exciter. Standard regulators (PI or PID-like) are normally used for the rectification of the generator voltage to be used to supply a high-voltage DC bus. The regulation is obtained by acting on a DC/DC converter that imposes the field voltage of the exciter. In this paper, the field voltage is fed to the generator windings by using a second-order sliding mode controller, resulting into a stable, robust (against disturbances) action and a fast convergence to the desired reference. By using this strategy, an energy management strategy is proposed that dynamically changes the voltage set point, in order to intelligently transfer power between two voltage busses. Detailed simulation results are provided in order to show the effectiveness of the proposed energy management strategy in different scenarios
Supervisory control of DC-DC bidirectional converter for advanced aeronautic applications
No full textIn this paper, a sliding manifold-based control strategy is used for controlling a bidirectional DC-DC converter for aeronautic applications. The proposed design follows a 2-level strategy, where low-level controllers are designed first, then a high-level supervisor is used for scheduling the low-level controllers. Different from previous approaches, each of the low-level controlled system is a globally exponentially stable closed-loop system, thus resulting into simpler conditions for the stability of the overall system. Moreover, stability of the supervisory strategy is rigorously proved by using a suitable Lyapunov function. Finally, a switching implementation is also considered. The effectiveness and robustness of the proposed strategy is shown by detailed simulations in Matlab/Stateflow/SymPowerSystem
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