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Instead of a conventional wireless transceiver system that requires batteries and complex circuits, the surface acoustic wave (SAW) sensor enables wireless passive measurement. A sensor consisting of an SAW device and external impedance sensing element is analysed. Since the reflection coefficient of the reflective grating on the SAW device depends on the load impedance, the echo characteristics are influenced by the change in the impedance of external sensing element. A resistance sensor or a capacitive sensor is selected as the external sensing element. The two different types of sensors are simulated using coupling-of-mode (COM) modelling, and the relationships between amplitude and phase with load impedance are analysed. On the basis of COM theory, a wireless impedance-loaded SAW sensor is fabricated by the lift-off process and tested by a network analyser to verify the simulation results. It is observed that the test results agree well with the simulation results. The phase change is more sensitive than the amplitude based on the results obtained. The sensitivity is 0.274°/Ω for the sensor with resistance and the sensitivity of the sensor with capacitance is 1.096°/pF. These results can guide the design of the high sensitivity impedance-loaded SAW sensors in the future. [ABSTRACT FROM AUTHOR]

Gesture recognition acts as a key enabler for user-friendly human-computer interfaces (HCI). To bridge the human-computer barrier, numerous efforts have been devoted to designing accurate fine-grained gesture recognition systems. Recent advances in wireless sensing hold promise for a ubiquitous, non-invasive and low-cost system with existing Wi-Fi infrastructures. In this paper, we propose DeepNum, which enables fine-grained finger gesture recognition with only a pair of commercial Wi-Fi devices. The key insight of DeepNum is to incorporate the quintessence of deep learning-based image processing so as to better depict the influence induced by subtle finger movements. In particular, we make multiple efforts to transfer sensitive Channel State Information (CSI) into depth radio images, including antenna selection, gesture segmentation and image construction, followed by noisy image purification using high-dimensional relations. To fulfill the restrictive size requirements of deep learning model, we propose a novel region-selection method to constrain the image size and select qualified regions with dominant color and texture features. Finally, a 7-layer Convolutional Neural Network (CNN) and SoftMax function are adopted to achieve automatic feature extraction and accurate gesture classification. Experimental results demonstrate the excellent performance of DeepNum, which recognizes 10 finger gestures with overall accuracy of 98% in three typical indoor scenarios. [ABSTRACT FROM AUTHOR]

Multi-agent consensus has been widely applied in engineering. A novel protocol that can achieve an average state consensus for multi-agent systems in finite time is presented in this paper. The proposed protocol contains a non-linear and a linear term. The state consensus is achieved in finite time by the non-linear term and convergence performance is improved by the linear term to some degree. The protocol can be applied to systems with a switching topology as long as the communication graph is always undirected and connected. The upper bound of convergence time is obtained. The relationship between convergence time and protocol parameter, communication topology and initial state is analysed. Lastly, simulations are conducted to verify the effectiveness of the results. [ABSTRACT FROM AUTHOR]

A novel quartz micromachined gyroscope is proposed in this paper. The novel gyroscope is realized by quartz anisotropic wet etching and 3-dimensional electrodes deposition. In the quartz wet etching process, the quality of Cr/Au mask films affecting the process are studied by experiment. An excellent mask film with 100 Å Cr and 2000 Å Au is achieved by optimization of experimental parameters. Crystal facets after etching seriously affect the following sidewall electrodes deposition process and the structure's mechanical behaviours. Removal of crystal facets is successfully implemented by increasing etching time based on etching rate ratios between facets and crystal planes. In the electrodes deposition process, an aperture mask evaporation method is employed to prepare electrodes on 3-dimensional surfaces of the gyroscope structure. The alignments among the aperture masks are realized by the ABM™ Mask Aligner System. Based on the processes described above, a z-axis quartz gyroscope is fabricated successfully. [ABSTRACT FROM AUTHOR]

Optimal sensor placement is a key issue in the structural health monitoring of large-scale structures. However, some aspects in existing approaches require improvement, such as the empirical and unreliable selection of mode and sensor numbers and time consuming computation. A novel improved particle swarm optimization (IPSO) algorithm is proposed to address these problems. The approach firstly employs the cumulative effective modal mass participation ratio to select mode number. Three strategies are then adopted to improve the PSO algorithm. Finally, the IPSO algorithm is utilized to determine the optimal sensors number and configurations. A case study of a latticed shell model is implemented to verify the feasibility of the proposed algorithm and four different PSO algorithms. The effective independence method is also taken as a contrast experiment. The comparison results show that the optimal placement schemes obtained by the PSO algorithms are valid, and the proposed IPSO algorithm has better enhancement in convergence speed and precision. [ABSTRACT FROM AUTHOR]

Optimal sensor placement is an important part in the structural health monitoring of bridge structures. However, some defects are present in the existing methods, such as the focus on a single optimal index, the selection of modal order and sensor number based on experience, and the long computation time. A hybrid optimization strategy named MSE-AGA is proposed in this study to address these problems. The approach firstly selects modal order using modal participation factor. Then, the modal strain energy method is adopted to conduct the initial sensor placement. Finally, the adaptive genetic algorithm (AGA) is utilized to determine the optimal number and locations of the sensors, which uses the root mean square of off-diagonal elements in the modal assurance criterion matrix as the fitness function. A case study of sensor placement on a numerically simulated bridge structure is provided to verify the effectiveness of the MSE-AGA strategy, and the AGA method without initial placement is used as a contrast experiment. A comparison of these strategies shows that the optimal results obtained by the MSE-AGA method have a high modal strain energy index, a short computation time, and small off-diagonal elements in the modal assurance criterion matrix. [ABSTRACT FROM AUTHOR]

This paper proposes a novel quartz micromachined gyroscope. The structure is designed by using shear stress detection method which can simplify the sidewall electrodes obviously. Furthermore, a tuning fork is introduced by the structure to obtain better differential vibrations. In order to increase the sensitivity of the sensor, the sense beam is designed to be a symmetric tapered beam. The device was fabricated using quartz anisotropic wet etching process. The drive mode frequency is 14.99 kHz, and the quality factor is 7600 in air. The sense mode frequency is 14.25 kHz, and the quality factor is 600 in air. Therefore, this gyroscope can operate at atmosphere pressure properly. The sensor is tested on a rate table through a specially designed readout circuitry. The sensitivity is 23.9 and the nonlinearity is 1.1% in range of . The noise floor is 0.1 . [ABSTRACT FROM PUBLISHER]

This paper is concerned with the problem of controller design for switched systems under asynchronous switching with exogenous disturbances. The attention is focused on designing the feedback controller that guarantees the finite-time bounded and L∞ finite-time stability of the dynamic system. Firstly when there exists asynchronous switching between the controller and the system, a sufficient condition for the existence of stabilizing switching law for the addressed switched system is derived. It is proved that the switched system is finite-time stabilizable under asynchronous switching satisfying the average dwell-time condition. Furthermore, the problem of L∞ control for switched systems under asynchronous switching is also investigated. Finally, a numerical example is given to illustrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]