Permanent magnet synchronous motors (PMSMs) have expectant low‐speed servo performance. However, complex nonlinear disturbances restrict the performance and lead to speed fluctuations, especially for ...small inertia PMSMs where the current‐loop cannot be used in special operating conditions. This paper divides complex disturbances into periodic determinable disturbances and other indeterminate disturbances according to their characteristics. A refined anti‐disturbance control (RADC) method is proposed to enable the inner loop to compensate for disturbances in targeted manners. Then ideal low‐speed servo can be achieved using a simple outer loop controller. The proposed RADC consists of two parts. One is a backpropagation neural network based periodic disturbances compensator that is trained using the data from an iterative learning controller. The other is an adaptive sliding‐mode‐assisted disturbance observer that rapidly observes and compensates the residual disturbances. The convergence of the overall algorithm is analyzed. The effectiveness of the proposal is also verified by experiments.
This paper focuses on the problem of disturbance suppression in low‐speed PMSM servo systems when using the current‐loop‐free control method. A new active hierarchical refined anti‐disturbance controller, the RADC, is proposed.
Complex multi‐source disturbances are classified into the periodic determinable disturbance and the indeterminate residual disturbance according to their characteristics. BPNN based on ILC is used to fit the periodic disturbance. ILC aims to provide more comprehensive input and output datasets for BPNN training, rather than as the final controller. The RADC controller is used in the inner loop of the control so that the BPNN‐based offline disturbance compensator and ASMADO can hierarchically compensate for the above two kinds of disturbances. The offline disturbance compensator obtained by fitting the BPNN is a continuous function of the angular position of the motor and the periodic disturbance, allowing accurate and fast compensation of periodic disturbance at any position of the motor. The ASMADO consists of a DOB and an ASMC. First, the DOB is constructed to observe disturbances in the low‐frequency domain. Then, the ASMC is then not used as a controller but is designed to assist the DOB in estimating and compensating for high‐frequency disturbances. Besides, the adaptive switching gain is automatically adjusted with the sliding mode state, which not only allows the system to converge quickly but also reduces the system jitter at a steady state with better robustness.
The experimental results demonstrate the effectiveness and superiority of the RADC. When the current‐ free‐loop control method is used, the speed fluctuation of PMSM is still effectively suppressed, and the low‐speed tracking performance is superior. Therefore, the proposed method is novel and necessary to improve the anti‐disturbance performance of the PMSM in engineering applications.
When the initial size of an atom cloud in a cold atom interferometer is negligible compared to its size after free expansion, the interferometer is approximated to a point-source interferometer and ...is sensitive to rotational movements by introducing an additional phase shear in the interference sequence. This sensitivity on rotation enables a vertical atom-fountain interferometer to measure angular velocity in addition to gravitational acceleration, which it is conventionally used to measure. The accuracy and precision of the angular velocity measurement depends on proper extraction of frequency and phase from spatial interference patterns detected via the imaging of the atom cloud, which is usually affected by various systematic biases and noise. To improve the measurement, a pre-fitting process based on principal component analysis is applied to the recorded raw images. The contrast of interference patterns are enhanced by 7-12 dB when the processing is present, which leads to an enhancement in the precision of angular velocity measurements from 6.3 μrad/s to 3.3 μrad/s. This technique is applicable in various instruments that involve precise extraction of frequency and phase from a spatial interference pattern.
Nowadays, Mn4+-activated fluoride phosphors because of the excellent luminescence properties have been widely used to improve the luminous efficiency of white LED. However, it is inevitable to use ...toxic HF as solvent in the preparation of such phosphors, which can cause a series of potential safety hazards. Hence, an effective green synthesis strategy should be adopted to prepare Mn4+-activated fluoride phosphors by simple cation exchange method at room temperature. In this work, the non-toxic reaction system (HNO3/CH3COOH + NH4F) can successfully replace HF as the reaction solution to synthesize a series of Na2SiF6:Mn4+ red phosphors with strong zero-phonon line emission. The crystal structure, morphology and elemental composition of as-prepared Na2SiF6:Mn4+ phosphors are systematically studied. Na2SiF6:Mn4+ phosphor shows bright red-light emission because of the spin-forbidden 2Eg → 4A2g transition of Mn4+ under the excitation of blue and UV light, and the correlated color temperature and the color purity of red fluorescence are calculated in detail. The crystal field strength (Dq) and the Racah parameters (B and C) are calculated to evaluate the crystal field environment of Mn4+ in Na2SiF6. The effect of synthesis conditions on the fluorescence properties of the as-prepared phosphors is also thoroughly discussed, including different sodium sources and acid amounts. The optimal Mn4+ doping concentration is 0.03, and the concentration quenching mechanism is determined to be a dipole-dipole interaction. Impressively, Na2SiF6:Mn4+ phosphor presents exceptional thermal quenching behavior. Within the test temperature range of 298–423 K, the thermal quenching activation energy, chromaticity shift and chromaticity coordinate variation are 0.76 eV, 14.14 × 10−3 and (−0.0055, 0.0055), respectively. Importantly, warm white LED is fabricated using Na2SiF6:Mn4+ and Y3Al5O12:Ce3+ under blue LED excitation, which exhibits excellent optical properties (CCT = 3987 K and Ra = 91.8). Moreover, it also shows good output stability at high drive current. Therefore, this work provides a new strategy to synthesize highly efficient Mn4+-activated fluoride red phosphors through a green synthesis route for the potential application in high-performance warm white LED.
•Na2SiF6:Mn4+ red phosphors were synthesized via an effective green synthesis strategy.•Na2SiF6:Mn4+ phosphor has strong zero-phonon line red emission.•Na2SiF6:Mn4+ phosphor has an excellent thermal quenching behavior.•Using Na2SiF6:Mn4+ phosphor, a high-performance warm white LED was obtained.
Currently, Mn4+ activated fluoride red phosphor has been widely studied to improve the optical performance of white light-emitting diode (WLED) in the field of high-efficiency lighting and wide color ...gamut backlight display. In this paper, a series of red-emitting K2NaScF6:Mn4+ phosphors are synthesized by a simple co-precipitation method with a non-equivalent substitution of Mn4+ for Sc3+ at room temperature. The crystal structure, morphology and elemental composition of K2NaScF6:Mn4+ phosphors prepared using different reaction conditions are systematically investigated. Interestingly, the K2NaScF6:Mn4+ phosphors exhibit narrowband red emission with low correlated color temperature (CCT), high color purity and short fluorescence lifetime. Compared to equivalent doping, the mechanism of short fluorescence lifetime caused by non-equivalent doping has also been systematically discussed. The optimal doping concentration is determined by setting a series of Mn4+ doping concentrations and the concentration quenching mechanism is analyzed. The crystal field strength (Dq), Racah parameters (B and C) and nephelauxetic ratio (β1) are calculated in detail to evaluate the crystal field environment of Mn4+ in K2NaScF6. The good water resistance of the as-prepared sample K2NaScF6:Mn4+ is verified by comparing with the commercially available phosphor K2SiF6:Mn4+. Moreover, the thermal stability is also analyzed by calculating the activation energy (Ea), chromaticity shift (ΔE) and chromaticity coordinate variation (CCV). Importantly, the as-packaged warm WLED (InGaN chip + YAG:Ce3+ + K2NaScF6:Mn4+) has excellent optical properties (CCT = 4082 K, color rendering index (CRI, Ra = 91.2) and luminous efficiency (LE) = 78.86 lm/W), and it exhibits good output stability at high drive currents. In summary, our work demonstrates that K2NaScF6:Mn4+ red phosphors possess a great potential application in warm WLED for the indoor lighting.
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•K2NaScF6:Mn4+ red phosphor was synthesized via an effective non-equivalent doping strategy.•K2NaScF6:Mn4+ phosphor has excellent optical properties.•K2NaScF6:Mn4+ phosphor has excellent water resistance and thermal stability.•Using K2NaScF6:Mn4+ phosphor, a high-performance warm WLED was obtained.
The cover image is based on the Original Research ASMADO‐based refined anti‐disturbance low‐speed control of PMSM by Huifan Wang et al., https://doi.org/10.1049/pel2.12501.
Red-emitting Mn4+-doped fluoride phosphors are promising fluorescent material for use in high-performance warm white light emitting diodes (WLEDs). However, low stability and non-green synthesis ...method limit the development and commercialization of such phosphor. Herein, a series of novel (Li/Na/Cs)0.4Ba0.8SiF6:Mn4+ phosphors with optimized fluorescence properties induced by alkaline metal ions replacement are successfully synthesized via a green and eco-friendly approach. Under the irradiation of 460 nm blue light, Cs0.4Ba0.8SiF6:Mn4+ red phosphor with narrow band emission peak has the best optical performance. The optimal doping concentration of Mn4+ in Cs0.4Ba0.8SiF6 host and the reason for concentration quenching are systematically analyzed. Furthermore, the moisture resistance and thermal stability of this phosphor are discussed. After being soaked in deionized water for 90 min, the PL intensity of Cs0.4Ba0.8SiF6:Mn4+ phosphor can maintain at 40% of that in air, which is 4 times higher than commercial K2SiF6:Mn4+. At the operating temperature of LED (423 K), Cs0.4Ba0.8SiF6:Mn4+ red phosphor can exhibit stable light output intensity and color. A warm WLED with low correlated color temperature of 4336 K, high color rendering index of 88.4 and high lumen efficiency of 105.96 lm/W is fabricated via using Cs0.4Ba0.8SiF6:Mn4+ phosphor as a component of red-light, and the warm WLED can maintain stable output even at high driving currents. Overall, the alkali metal ion replacement and green synthesis strategies have opened up a new perspective for the synthesis of efficient Mn4+-doped fluoride phosphors, which has dual benefits for optimizing the performance of WLED and environmental protection.
Novel Cs0.4Ba0.8SiF6:Mn4+ phosphor with efficient water and thermal stability is synthesized by combining alkali metal ion substitution method with green synthesis route for high-performance warm WLED. Display omitted
•An eco-friendly approach is adopted to synthetic Mn4+-activated fluoride phosphors.•Alkali metal ion replacement enhances the optical properties of Mn4+-doped phosphor.•Cs0.4Ba0.8SiF6:Mn4+ phosphor with excellent stability is obtained.•Warm WLED can be realized using Cs0.4Ba0.8SiF6:Mn4+ as the red light component.
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•Copper-based perovskite quantum dots are self-assembled during fiberized process.•Transition between Cs3Cu2I5 and CsCu2I3 dominates the luminescent color conversion.•Humidity is ...identified as a novel stimulus for luminescence regulation.•Polymer coating makes flexible fibers graphically displayable and chemically stable.•Water-responsive fluorescent fiber with unique incomplete reversibility is provided.
Halide perovskite presents great competitive advantages in the new generation of stimuli-responsive materials, while the tuning of fluorescence emission is still limited by irritative factors and external conditions. Herein, anti-solvent assisted crystallization and in-situ synthesis are innovatively combined to accomplish the fiberized self-assembly of copper-based perovskite quantum dots economically and environmentally, which makes humidity a novel stimulus for luminescence regulation. Under the excitation of medium-wave UV, the original Cs3Cu2I5-CsCu2I3@polyacrylonitrile (CCI@PAN) fibers exhibit a main emission peak of 460 nm with a shoulder at 550 nm, and the intensity of shoulder peak is gradually increased with the continuous addition of moisture. Switching from blue to yellow fluorescence is achieved in CCI@PAN fiber membrane by the introduction of water, which is attributed to the ultra-high solubility of CsI in water. Moreover, owing to the spatial limitation of the nanofibers, the unique incomplete reversibility exhibited by the nanofiber membrane during water removal predicts that the nanofiber membrane can be used as a permanent recording material. Overall, this work deeply explores the influence of humidity on the fluorescence and structure of perovskite quantum dots, providing a method to synthesize innovative perovskite nanofiber composites based on emission conversion, which has broad prospects in advanced anti-counterfeiting, biological protection display, information encryption and smart wearable devices.
Currently, Mn4+-doped fluoride phosphors have become a research hotspot, which can help compensate for the missing red component in cold white light-emitting diodes (WLEDs). However, significant ...synthesis defects limit the development of such fluorescent powders due to the use of highly toxic solvent HF. To improve this situation, a simple green synthesis method should be explored to synthesize Mn4+-activated fluoride phosphor. In this study, a series of red-emitting Mn4+-activated BaTiF6 phosphors are successfully synthesized via the non-toxic reaction system (HNO3/HCl + NH4F). Its crystal structure, morphology, optical characteristics and thermal stability are systematically evaluated. Under blue light excitation, BaTiF6:Mn4+ exhibits a bright narrow-band red emission with exceptional correlated color temperature (3909 K) and color purity (90%). Additionally, the critical concentration of Mn4+ is determined to be 0.03 and the concentration quenching mechanism is also systematically discussed. By calculating the crystal field strength (Dq), Racah parameters (B and C) and nephelauxetic effect ratio parameter β1, it is confirmed that BaTiF6 host can provide a strong crystal field environment for Mn4+. Moreover, these results are compared with other matrix materials. Intriguingly, the optimal sample exists satisfactory thermal stability, whose fluorescence intensity at 423 K retains 49% of that at 298 K and the activation energy reaches up to 0.925 eV. In addition, the chromaticity shift and chromaticity coordinate variation are calculated as 17 × 10−3 and (−0.0063, 0.0063), respectively. Meanwhile, the feasibility of the as-fabricated WLEDs for interior illumination is examined. A high-performance warm WLED with low correlated color temperature (CCT = 4470 K) and high color rendering index (Ra = 88.3) is achieved by using BaTiF6:Mn4+ as a red-emitting material, moreover, WLED exhibits strong output stability under high driving current. The findings of this work provide a comprehensive understanding for rational design of high-performance Mn4+-activated fluoride red phosphors through a simple green synthesis method.
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•BaTiF6:Mn4+ red phosphors were synthesized via an effective green synthesis strategy.•BaTiF6:Mn4+ phosphor has an excellent thermal quenching behavior.•Using BaTiF6:Mn4+ phosphor, a high-performance warm white LED was obtained.•Warm white LED exhibits strong output stability under high driving current.
In an atomic fountain, atoms in motion can be spatially separated into discrete Zeeman sub-states by magnetically induced Stern-Gerlach effect. With resonant light pulses acting as a shutter, ...specific states are selected for subsequent experiments. Such separation-selection process in atomic optics is the analogue of a spatial filter in physical optics which selects and purifies the modes of light. This technique is demonstrated by injecting a pulsed current in a circular coil around a vertical atomic fountain, separating the pre-cooled Rubidium atoms by a distance of centimeters in between, and filtering each single sub-state with block pulses. The filtered atoms after the process is highly purified in the desired sub-state. The apparatus of the atomic spatial filter is adaptable in atomic optics and can be integrated into the high-vacuum chamber of an atomic fountain.
