While exact parameter estimation is desired in numerous applications, many adaptive controllers require the fulfillment of the persistency of excitation (PE) condition to achieve that objective. Relaxing the PE condit...
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ISBN:
(数字)9783907144107
ISBN:
(纸本)9798331540920
While exact parameter estimation is desired in numerous applications, many adaptive controllers require the fulfillment of the persistency of excitation (PE) condition to achieve that objective. Relaxing the PE condition poses a challenging theoretical problem and many research works have been devoted to addressing this issue. In this paper, we propose a novel adaptive robust nonlinear
$\mathcal{H}_{\infty}$
optimal controller for trajectory tracking of mechanical systems subjected to unknown parameters. The proposed method includes an extra term, based on the dynamic regressor extension and mixing (DREM) approach, into the adaptive law which enables exact parameter estimation even without fulfilling the PE condition. The effectiveness of the proposed adaptive controller is corroborated with numerical experiments involving a CRS-A465 robot manipulator and comparison analyses with a classic adaptive nonlinear
$\mathcal{H}_{\infty}$
controller.
The large industries that work with high power demand increasingly want to optimize their production lines. In this context, several studies and research about the multi-level power converts have been realized in last...
The large industries that work with high power demand increasingly want to optimize their production lines. In this context, several studies and research about the multi-level power converts have been realized in last years, as they have several advantages when compared to traditional two-level topologies: better harmonic performance, filters reduction, lower components voltage stress and higher power process capability. The present work proposes a Cuk DC-DC converter composed of multilevel flying capacitor asymmetric totem-pole switching cell. This structure is achieved by replacing one leg of switch/diode of the traditional two-level asymmetric totem-pole cell by a similar multilevel flying capacitor cell. This work presents a brief analysis of the operation of the proposed converter, as well as the control strategy to keep the output voltage at the desired value and contains simulation results to validate the theoretical approach.
Exceptional points(EPs)have been extensively explored in mechanical,acoustic,plasmonic,and photonic ***,little is known about the role of EPs in tailoring the dynamic tunability of optical devices.A specific type of E...
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Exceptional points(EPs)have been extensively explored in mechanical,acoustic,plasmonic,and photonic ***,little is known about the role of EPs in tailoring the dynamic tunability of optical devices.A specific type of EPs known as chiral EPs has recently attracted much attention for controlling the flow of light and for building sensors with better responsivity.A recently demonstrated route to chiral EPs via lithographically defined symmetric Mie scatterers on the rim of resonators has not only provided the much-needed mechanical stability for studying chiral EPs,but also helped reduce losses originating from nanofabrication imperfections,facilitating the in-situ study of chiral EPs and their contribution to the dynamics and tunability of ***,we use asymmetric Mie scatterers to break the rotational symmetry of a microresonator,to demonstrate deterministic thermal tuning across a chiral EP,and to demonstrate EP-mediated chiral optical nonlinear response and efficient electro-optic *** results indicate asymmetric electro-optic modulation with up to 17 dB contrast at GHz and CMOS-compatible voltage *** wafer-scale nano-manufacturing of chiral electro-optic modulators and the chiral EP-tailored tunning may facilitate new micro-resonator functionalities in quantum information processing,electromagnetic wave control,and optical interconnects.
A 16 u 16 array micro-LED display was fabricated by using Si micro-cup substrates. Emission patten exhibited apparent reduction of lateral spread of light in case of the micro-LEDs embedded in the Si micro-cup. The mi...
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Luminescent solar concentrators (LSC) absorb large-area solar radiation and guide down-converted emission to solar cells for electricity production. Quantum dots (QDs) have been widely engineered at device and quantum...
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Luminescent solar concentrators (LSC) absorb large-area solar radiation and guide down-converted emission to solar cells for electricity production. Quantum dots (QDs) have been widely engineered at device and quantum dot levels for LSCs. Here, we demonstrate cascaded energy transfer and exciton recycling at nanoassembly level for LSCs. The graded structure composed of different sized toxic-heavy-metal-free InP/ZnS core/shell QDs incorporated on copper doped InP QDs, facilitating exciton routing toward narrow band gap QDs at a high nonradiative energy transfer efficiency of 66%. At the final stage of non-radiative energy transfer, the photogenerated holes make ultrafast electronic transitions to copper-induced mid-gap states for radiative recombination in the near-infrared. The exciton recycling facilitates a photoluminescence quantum yield increase of 34% and 61% in comparison with semi-graded and ungraded energy profiles, respectively. Thanks to the suppressed reabsorption and enhanced photoluminescence quantum yield, the graded LSC achieved an optical quantum efficiency of 22.2%. Hence, engineering at nanoassembly level combined with nonradiative energy transfer and exciton funneling offer promise for efficient solar energy harvesting.
Multilevel power converters have been aim of research in the last years due to their advantages when compared to traditional two-level topologies: better harmonic performance, filters reduction, lower components volta...
Multilevel power converters have been aim of research in the last years due to their advantages when compared to traditional two-level topologies: better harmonic performance, filters reduction, lower components voltage stress and higher power process capability. Following this trend, the present work proposes two Zeta DC-DC converters composed of multilevel flying capacitor asymmetric totem-pole switching cells. These structures are achieved by replacing one leg of switch/diode of the traditional two-level asymmetric totem-pole switching cell by a similar multilevel flying capacitor switching cell. A generalized structure of the flying capacitor switching cell for $k$ switches is presented. An operation analysis of the proposed converter is presented as well as simulation results to validate the theoretical approach.
Extremely large-scale multiple-input multiple-output (XL-MIMO) is expected to play an important role in future sixth generation (6G) networks. Most existing works in this area focus on single-polarized XL-MIMO, where ...
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Recent studies have shown the potential of em-ploying the Terahertz (THz) band for 6G non-terrestrial communications including drones. This paper assesses the outage performance of the THz band Drone-to-Ground (D2G) v...
Recent studies have shown the potential of em-ploying the Terahertz (THz) band for 6G non-terrestrial communications including drones. This paper assesses the outage performance of the THz band Drone-to-Ground (D2G) vertical communications up to 100 m altitude at four practically feasible THz transmission windows (TWs): f 1 = 0.140 THz; [0.110-0.170] THz, f 2 = 0.300 THz; [0.275-0325] THz, f 3 = 0.850 THz; [0.790-0.910] THz, and f 4 = 0.935 THz; [0.930-03940] THz. We consider vertical D2G communication, where realistic THz-based absorption gains of the four THz TWs at the drone altitudes are obtained via the International Telecommunications Union (ITU) model using the Standard Weather Profile. Additionally, multipath (MP) fading and beam misalignment (BM) fading are incorporated into the overall channel gain for assessing the outage performance. Numerical results reveal that under severe BM fading and Rayleigh fading, THz band D2G communication employing 60 dBi total antenna gains at $f_{1},\ f_{2},\ f_{3}$, and f 4 can be reliably established up to the drone altitudes: 76.9 m, 59.2m, 34.4 m, and 43.2 m, and up to 85.1 m, 60.3m, 36.9m, 45.5m under the severe BM fading and the presence of a strong Line-of-Sight component, truly showcasing the achievable altitude and range limits for the THz band D2G communications among 6G non-terrestrial cognitive networks.
This paper proposes a three-phase three-level AC/DC converter with reduced number of controlled switches and high-frequency DC-bus based on NPC (Neutral Point Clamped) topology, for unidirectional power flow applicati...
This paper proposes a three-phase three-level AC/DC converter with reduced number of controlled switches and high-frequency DC-bus based on NPC (Neutral Point Clamped) topology, for unidirectional power flow applications. Galvanic isolation is reached by using a center tap transformer, which requires only a full-bridge at it primary side. No bulky electrolytic capacitors are needed on the DC-bus, in contrast to conventional multilevel topologies. A PWM strategy with carriers arranged in alternating phase opposition (PWM-APOD) is used to operate the proposed converter. The applied PWM technique is able to operate the converter stage on the AC side with only two switches commuting per switching period. The switches of the isolated pulsating DC/DC converter are commutated with half the switching frequency of the converter on the AC side. A dual-loop control strategy with PI voltage and PI resonant current controllers is adopted to ensure reference load voltage and almost sinusoidal grid currents. Simulation and experimental results are presented to validate the proposed converter operation.
This paper proposes a novel multi-view (MV) video coding technique that leverages a four-dimensional (4D) voxel-grid representation to enhance coding efficiency, particularly in novel view synthesis. Although the voxe...
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