Recent progress in the design and fabrication of multifunctional structures based on metamaterials

Yuan, Xujin; Chen, Mingji; Yao, Yin; Guo, Xiaogang; Huang, Yixing; Peng, Zhilong; Jin, Xiaochao; Tao, Ran; Duan, Shenyu; Liao, Hua; Yao, Kai; Li, Ying; Lei, Hongshuai; Xu, Chen; Hong, Guangfu; Fang, Daining

doi:10.1016/j.cossms.2020.100883

Cited by 69 publications

(18 citation statements)

References 125 publications

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“…Calculate the force of the left hand and right hand in the 𝑅axis and 𝑅 -axis directions, the final combined forces 𝐹 and 𝐹 in the 𝑅 -axis and 𝑅 -axis directions can be calculated as formula (2):…”

Section: A Upper Limb Motion Analysismentioning

confidence: 99%

“…At present, there are two types of smart devices to solve the walking problem of the elderly and the disabled: electric wheelchairs and smart walkers. Electric wheelchairs can completely replace human legs to complete basic walking [2], while smart walkers can be used to assist with walking, and carry out related rehabilitation training, which is a key research direction in the field of medical devices [3]. Falling is a significant challenge for the elderly group that can reduce life expectancy.…”

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confidence: 99%

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Fall Detection System on Smart Walker Based on Multisensor Data Fusion and SPRT Method

et al. 2022

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Traditional walkers are commonly used for the elderly in social life, which solves the basic problem of walking, but it is difficult to ensure safety when a fall occurs, and the human-computer interaction is poor. The image recognition method or the IMU sensor method fixed on the user, such as a wearable watch, is used by most of the current fall detection methods. Wearable sensors require the user's wearing operation, which is a little troublesome, and the detection accuracy is related to the way of wearing. The image recognition method requires a high-priced camera and a fixed installation position, which is unable to adapt to outdoor activities. We investigated a low-cost method of mounting the sensor on the body of the walker. We propose in this paper an improved fall detection method, namely Precondition and Limit Threshold SPRT (PLT-SPRT), and a novel fall detection system on the smart walker based on PLT-SPRT. The signals of the upper and lower limb sensors are fused based on the Kalman filter algorithm, and the admittance control parameters are obtained through the system identification method. In this study, the improved sequential probability ratio test algorithm is used to set the null hypothesis and the alternative hypothesis, construct the likelihood ratio and optimize the decision function, which is used to judge whether falls occur. The system is simulated by Matlab software, the user intention after fusion is more accurate, and the optimized decision function is judged accurately. Verified by the embedded system based on STM32 of the smart walker equipment in the real world, it can accurately identify the fallen state, with low detection delay, and the fallen state is detected about 160ms earlier than the traditional threshold-based detection algorithm, at the same time, the accuracy is higher than 94.9%, which meets the high real-time requirements of fall detection and is the ideal solution for smart walkers.

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Section: A Upper Limb Motion Analysismentioning

confidence: 99%

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confidence: 99%

Fall Detection System on Smart Walker Based on Multisensor Data Fusion and SPRT Method

et al. 2022

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“…Pentamode metamaterials have five zero eigenvalues of modulus matrices, [ 224 ] and the shear modulus G is much smaller than the bulk modulus K , which brings unique elasticity. Pentamode metamaterials are also called shear modulus weakened metamaterials, the mechanical properties are similar to the 2D ideal fluid.…”

Section: Functions and Practical Applications Of Active Mechanical Metamaterialsmentioning

confidence: 99%

Recent Progress in Active Mechanical Metamaterials and Construction Principles

et al. 2021

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Active mechanical metamaterials (AMMs) (or smart mechanical metamaterials) that combine the configurations of mechanical metamaterials and the active control of stimuli-responsive materials have been widely investigated in recent decades. The elaborate artificial microstructures of mechanical metamaterials and the stimulus response characteristics of smart materials both contribute to AMMs, making them achieve excellent properties beyond the conventional metamaterials. The micro and macro structures of the AMMs are designed based on structural construction principles such as, phase transition, strain mismatch, and mechanical instability. Considering the controllability and efficiency of the stimuli-responsive materials, physical fields such as, the temperature, chemicals, light, electric current, magnetic field, and pressure have been adopted as the external stimuli in practice. In this paper, the frontier works and the latest progress in AMMs from the aspects of the mechanics and materials are reviewed. The functions and engineering applications of the AMMs are also discussed. Finally, existing issues and future perspectives in this field are briefly described. This review is expected to provide the basis and inspiration for the follow-up research on AMMs.

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“…However, structural‐level innovation can pave the way for functional integration and combining conflicting functions into a single structure. [ 29,30 ] In the past few years, numerous studies have shown that metamaterial structures have excellent controllability of electromagnetic waves. [ 18,31 ] Metasurface structures with selective permeability to EM waves can realize compatible stealth by taking advantage of the different wavelengths between radar waves and infrared waves, avoiding the defects of traditional compatible stealth materials.…”

Section: Introductionmentioning

confidence: 99%

Metasurface‐Based Hierarchical Structures: Excellent Electromagnetic Wave Absorbers with Low‐Infrared Emissivity Layer

et al. 2022

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Derived from the increasing demand for radar and infrared camouflage integration, a two‐layer hierarchical structure that combines coating and a square patch‐based metasurface is designed. Under deep subwavelength thickness, the infrared stealth layer (IRSL) can markedly reinforce microwave absorption layer (MAL) performance. More than 90% of the electromagnetic wave energy in the 3.7–5.1 GHz and 12.8–18 GHz bands can be absorbed. The hierarchical structure expands the effective absorption bandwidth of the exposed coatings from 0 to 6.6 GHz, and the maximum reflection loss increases from −8 to −40 dB. Moreover, the emissivity in the midinfrared range is maintained at an extremely low value of 0.281. The delay of magnetic resonance is found in the simulation model, indicating that strong magnetic resonance is formed in coatings after covering the IRSL. Meanwhile, the absorption peaks of the coatings are controlled by low‐pass filter metasurfaces. These two factors contribute to the enhancement effect of IRSL on MAL and break the boundary between radar and infrared stealth. Herein, an original solution for tuning multispectral electromagnetic (EM) waves is provided and it has broad application prospects in advanced compatible camouflage material.

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Recent progress in the design and fabrication of multifunctional structures based on metamaterials

Cited by 69 publications

References 125 publications

Fall Detection System on Smart Walker Based on Multisensor Data Fusion and SPRT Method

Fall Detection System on Smart Walker Based on Multisensor Data Fusion and SPRT Method

Recent Progress in Active Mechanical Metamaterials and Construction Principles

Metasurface‐Based Hierarchical Structures: Excellent Electromagnetic Wave Absorbers with Low‐Infrared Emissivity Layer

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