Search Results (20)

Processing errors can result in an asymmetric stiffness distribution within a microelectromechanical system (MEMS) disk resonator gyroscope (DRG) and thereby cause a mode mismatch and reduce the mechanical sensitivity and closed-loop scale factor stability. This paper proposes an automatic mode-matching method that utilizes mode reversal to obtain the true resonant frequency of the operating state of a gyroscope for high-precision matching. This method constructs a gyroscope control system that contains a drive closed loop, sense force-to-rebalance (FTR) closed loop, and quadrature error correction closed loop. After the gyroscope was powered on and started up, the x- and y-axes were quickly switched to obtain the resonant frequencies of the two axes through a phase-locked loop (PLL), and the x-axis tuning voltage was automatically adjusted to match the two-axis frequency. The experimental results show that the method takes only 5 s to execute, the frequency matching accuracy reaches 0.01 Hz, the matching state can be maintained in the temperature range of −20 to 60 °C, and the fluctuation of the frequency split does not exceed 0.005 Hz. Full article

Detection gain asymmetry error is one of the primary errors of the hemispherical resonator gyroscope (HRG) in whole-angle (WA) mode. This paper analyzes the influence of detection gain asymmetry error and its coupling error with damping and stiffness asymmetry on the performance of HRG and proposes a novel compensation method for detection gain asymmetry error. Firstly, the nonlinear error model of HRG considering the detection gain asymmetry error and its coupling error is established by using the average method. The influence of the angle-dependent scale factor error (ADS) and angle-dependent bias error (ADB) caused by the detection gain asymmetry error is analyzed by numerical simulation. Secondly, a parameter estimation algorithm based on force-to-rebalance (FTR) mode is proposed to decouple and identify the detection gain asymmetry error and damping asymmetry error. The identified parameters are used for the calibration of the HRG. Finally, the method is applied to the HRG operating in WA mode. The effectiveness of the proposed method is verified by experiments. After compensation, the bias instability is reduced from 3.6°/h to 0.6°/h, the scale factor nonlinearity is reduced from 646.57 ppm to 207.43 ppm, and the maximum pattern angle deviation is reduced from 0.6° to 0.05°. Full article

This article proposes a force rebalance control scheme based on a mode-localized resonant accelerometer (ML-RXL), which is applied to address the limited measurement range problem of the ML-RXL. For the first time, an empirical response model of the weakly coupling resonators for the amplitude ratio output is established. Based on this, this paper builds an overall model of the force rebalance control system to analyze the sensitivity characteristics by simulations, which demonstrates that the scheme can effectively broaden the linear measurement range. It is demonstrated that the sensor exhibits a highly linear output within a measurement range of ±1 g, with a sensitivity of the feedback-control voltage output measured at 2.94 V/g. The measurement range is expanded by at least 6.7 times. Moreover, the results show that the minimum input-referred acceleration noise density of the sensor for the force rebalance control scheme is 3.29 μg/rtHz, and that the best bias instability is optimized to 5.34 μg with an integral time of 0.64 s. Full article

Properties such as lower melting temperature, good tensile strength, good reliability, and well creep resistance, together with low production cost, make the system Bi-Sn an ideal candidate for fine soldering in applications such as reballing or reflow. The first objective of the work was to determine the thermodynamic quantities of Bi and Sn using the electromotive force measurement method in an electrolytic cell (Gibbs’ enthalpies of the mixture, integral molar entropies, and the integral molar excess entropies were determined) at temperatures of 600 K and 903 K. The second objective addressed is the comprehensive characterization of three alloy compositions that were selected and elaborated, namely Bi25Sn75, Bi50Sn50, and Bi75Sn25, and morphological and structural investigations were carried out on them. Optical microscopy and SEM-EDS characterization revealed significant changes in the structure of the elaborated alloys, with all phases being uniformly distributed in the Bi50Sn50 and Bi75Sn25 alloys. These observations were confirmed by XRD and EDP-XRFS analyses. Diffractometric analysis reveals the prevalence of metallic Bi and traces of Sn, the formation of the Sn_0.3Bi_0.7, Sn_0.95Bi_0.05 compounds, and SnO and SnO₂ phases. Full article

The Prebiotic Task Force of the International Life Sciences Institute (ILSI) Europe advances the science and understanding of prebiotics and their health benefits. The Task Force, comprising academic advisors and numerous industry scientists, aims to provide scientific evidence to support the development of prebiotic-containing foods and dietary supplements that can improve gut health and overall wellbeing. Last year, the Task Force published several (peer-reviewed) scientific papers: (1) a concise monograph, translated into seven languages, providing a user-friendly introduction to the abundant scientific knowledge on prebiotics, probiotics and the gut microbiota and their impact on human health; (2) a narrative review, providing an overview of the role of non-digestible carbohydrates in the human diet, their impact on the gut microbiota, and their potential as prebiotics, with a particular emphasis on structure-related activities and in vitro models; (3) a perspective review, describing state-of-the-art tools for harnessing the microbiome for precision health, such as pro- and prebiotic dietary solutions amongst others, and a corresponding future vision of healthcare; and (4) perspectives on what we know, what we need to investigate, and how to put knowledge into practice in the microbiota-gut-brain axis. Currently, the role of prebiotics in bacterial and viral infections and vaccination efficiency is being systematically reviewed. The review will give the current status for prebiotics impact on infections, both prevention or recovery, and in supporting vaccination efficacy, for academics and industry scientists in this field. The Task Force will also commence activity on highlighting the need to perform studies in healthy participants that test the potential “rescuing” effects of prebiotics under conditions where cognition may be transiently compromised. In addition, a multi-stakeholder workshop to discuss evidence for microbiome modulation and physiological pathways for improved health and reduced disease risk, that may support a roadmap for future health claim substantiation, is being initiated this year. Full article

This paper proposes a low-noise interface application-specific integrated circuit (ASIC) for a microelectromechanical systems (MEMS) disk resonator gyroscope (DRG) which operates in force-to-rebalance (FTR) mode. The ASIC employs an analog closed-loop control scheme which incorporates a self-excited drive loop, a rate loop and a quadrature loop. A ΣΔ modulator and a digital filter are also contained in the design to digitize the analog output besides the control loops. The clocks for the modulator and digital circuits are both generated by the self-clocking circuit, which avoids the requirement of additional quartz crystal. A system-level noise model is established to determine the contribution of each noise source in order to reduce the noise at the output. A noise optimization solution suitable for chip integration is proposed based on system-level analysis, which can effectively avoid the effects of the 1/f noise of the PI amplifier and the white noise of the feedback element. A performance of 0.0075°/√h angle random walk (ARW) and 0.038°/h bias instability (BI) is achieved using the proposed noise optimization method. The ASIC is fabricated in a 0.35 μm process with a die area of 4.4 mm × 4.5 mm and power consumption of 50 mW. Full article

Axisymmetric resonators are key elements of Coriolis vibratory gyroscopes (CVGs). The performance of a CVG is closely related to the stiffness and damping symmetry of its resonator. The stiffness symmetry of a resonator can be effectively improved by electrostatic tuning or mechanical trimming, both of which need an accurate knowledge of the azimuth angles of the two stiffness axes of the resonator. Considering that the motion of a non-ideal axisymmetric resonator can be decomposed as two principal oscillations with two different natural frequencies along two orthogonal stiffness axes, this paper introduces a novel high-precision method of stiffness axes identification. The method is based on measurements of the phase difference between the signals detected at two orthogonal sensing electrodes when an axisymmetric resonator is released from all the control forces of the force-to-rebalance mode and from different initial pattern angles. Except for simplicity, our method works with the eight-electrodes configuration, in no need of additional electrodes or detectors. Furthermore, the method is insensitive to the variation of natural frequencies and operates properly in the cases of either large or small frequency splits. The introduced method is tested on a resonator gyroscope, and two stiffness axes azimuth angles are obtained with a resolution better than 0.1°. A comparison of the experimental results and theoretical model simulations confirmed the validity of our method. Full article

In this paper, an online compensation method of phase delay error based on a Phase-Frequency (P-F) characteristic has been proposed for MEMS Coriolis Vibratory Gyroscopes (CVGs). At first, the influences of phase delay were investigated in the drive and sense mode. The frequency response was acquired in the digital control system by collecting the demodulation value of drive displacement, which verified the existence and influence of the phase delay. In addition, based on the P-F characteristic, that is, when the phase shift of the nonresonant drive force through the resonator is almost 0° or 180°, the phase delay of the gyroscope is measured online by injecting a nonresonant reference signal into the drive-mode dynamics. After that, the phase delay is self-corrected by adjusting the demodulation phase angle without affecting the normal operation of the gyroscopes. The approach was validated with an MEMS dual-mass vibratory gyroscope under double-loop force-to-rebalance (in-phase FTR and quadrature FTR) closed-loop detection mode and implemented with FPGA. The measurement results showed that this scheme can detect and compensate phase delay to effectively eliminate the effect of the quadrature error. This technique reduces the zero rate output (ZRO) from −0.71°/s to −0.21°/s and bias stability (BS) from 23.30°/h to 4.49°/h, respectively. The temperature sensitivity of bias output from −20 °C to 40 °C has reached 0.003 °/s/°C. Full article

The quadrature coupling error is an important factor that affects the detection output of microelectromechanical system (MEMS) gyroscopes. In this study, two quadrature error control methods, quadrature force-to-rebalance control (Mode I) and quadrature stiffness control (Mode II) were analyzed. We obtained the main factors affecting the zero-rate output (ZRO) under force-to-rebalance (FTR) closed-loop detection. The analysis results showed that the circuit phase delay in Mode I caused the quadrature channel to leak into the in-phase channel. However, in Mode II, the quadrature coupling stiffness was corrected in real time, which effectively improved the stability of the ZRO. The changes in the vibration displacement and Q-factor were the main factors for the ZRO drift in Mode II. Therefore, we propose an online compensation method for ZRO drift based on multiparameter fusion. The experimental results on a cobweb-like disk resonator gyroscope (CDRG) with a 340 k Q-factor showed that the bias instability (BI) of Mode II was significantly better than that of Mode I. After online compensation, the BI reached 0.23°/h, and the bias repeatability reached 3.15°/h at room temperature. Full article

With the development of the designing and manufacturing level for micro-electromechanical system (MEMS) gyroscopes, the control circuit system has become a key point to determine their internal performance. Nevertheless, the phase delay of electronic components may result in some serious hazards. This study described a real-time circuit phase delay correction system for MEMS vibratory gyroscopes. A detailed theoretical analysis was provided to clarify the influence of circuit phase delay on the in-phase and quadrature (IQ) coupling characteristics and the zero-rate output (ZRO) utilizing a force-to-rebalance (FTR) closed-loop detection and quadrature correction system. By deducing the relationship between the amplitude-frequency, the phase-frequency of the MEMS gyroscope, and the phase relationship of the whole control loop, a real-time correction system was proposed to automatically adjust the phase reference value of the phase-locked loop (PLL) and thus compensate for the real-time circuit phase delay. The experimental results showed that the correction system can accurately measure and compensate the circuit phase delay in real time. Furthermore, the unwanted IQ coupling can be eliminated and the ZRO was decreased by 755% to 0.095°/s. This correction system realized a small angle random walk of 0.978°/√h and a low bias instability of 9.458°/h together with a scale factor nonlinearity of 255 ppm at room temperature. The thermal drift of the ZRO was reduced to 0.0034°/s/°C at a temperature range from −20 to 70 °C. Full article

This article examines the extent to which the inclusion of the European Union (EU) Charter of Fundamental Rights in the Treaty of Lisbon, which gives legal force to socio-economic rights as well as civil and political rights, will succeed in helping EU member states meet international treaty obligations to implement socio-economic rights. Will the EU’s renewed commitment to developing the social sphere, post-Brexit, be more successful and will British citizens lose out on so-cio-economic rights in the long term if the EU succeeds in creating a better social or public dimension? Member states of the EU that have ratified the International Covenant on Economic, Social and Cultural Rights (ICESCR) have obligations to progressively realise economic, social and cultural (ESC) rights. Progress on this has been slow and potentially made more difficult by the economic direction adopted by the EU since the 1980s. Although the EU, from the beginning, saw itself as a “social market” it struggled to embed the “social” to the same extent that it embedded the “market”. Critics argue that the economic policies of the EU and key judgements of the European Court of Justice (ECJ) successfully dis-embedded the market from its social context. Additionally, the regulatory regime of the EU developed in a direction that limited the capacity of nation states to ameliorate the consequences of market-led policies for the least advantaged. However, the Charter of Rights, which places socio-economic rights on an equal footing with civil and political rights, is a novel and bold initiative. It has stimulated debate on whether the Charter could rebalance the EU’s economic agenda by paying attention to the social consequences of predominantly market-led policies. This paper examines the potential impact of the EU Charter, in the context of member states international human rights obligations, to create an environment where member states of the EU have fewer obstacles to the “progressive realization” of ESC rights. Full article

In this paper, the characterization and analysis of a silicon micromachined Quad Mass Gyroscope (QMG) in the rate mode of operation are presented. We report on trade-offs between full-scale, linearity, and noise characteristics of QMGs with different Q-factors. Allan Deviation (ADEV) and Power Spectral Density (PSD) analysis methods were used to evaluate the performance results. The devices in this study were instrumented for the rate mode of operation, with the Open-Loop (OL) and Force-to-Rebalance (FRB) configurations of the sense mode. For each method of instrumentation, we presented constraints on selection of control parameters with respect to the Q-factor of the devices. For the high Q-factor device of over 2 million, and uncompensated frequency asymmetry of 60 $\mathrm{m}$$\mathrm{Hz}$, we demonstrated bias instability of $0.095$${}^{\circ }$/$\mathrm{h}$r and Angle Random Walk (ARW) of $0.0107$${}^{\circ }$/$\sqrt{\mathrm{hr}}$ in the OL mode of operation and bias instability of $0.065$${}^{\circ }$/$\mathrm{h}$r and ARW of $0.0058$${}^{\circ }$/$\sqrt{\mathrm{hr}}$ in the FRB mode of operation. We concluded that in a realistic MEMS gyroscope with imperfections (nearly matched, but non-zero frequency asymmetry), a higher Q-factor would increase the frequency stability of the drive axis resulting in an improved noise performance, but has challenges in implementation of digital control loops. Full article

The prevalence of neurodegenerative diseases (NDD) has grown rapidly in recent years and NDD screening receives much attention. NDD could cause gait abnormalities so that to screen NDD using gait signal is feasible. The research aim of this study is to develop an NDD classification algorithm via gait force (GF) using multiscale sample entropy (MSE) and machine learning models. The Physionet NDD gait database is utilized to validate the proposed algorithm. In the preprocessing stage of the proposed algorithm, new signals were generated by taking one and two times of differential on GF and are divided into various time windows (10/20/30/60-sec). In feature extraction, the GF signal is used to calculate statistical and MSE values. Owing to the imbalanced nature of the Physionet NDD gait database, the synthetic minority oversampling technique (SMOTE) was used to rebalance data of each class. Support vector machine (SVM) and k-nearest neighbors (KNN) were used as the classifiers. The best classification accuracies for the healthy controls (HC) vs. Parkinson’s disease (PD), HC vs. Huntington’s disease (HD), HC vs. amyotrophic lateral sclerosis (ALS), PD vs. HD, PD vs. ALS, HD vs. ALS, HC vs. PD vs. HD vs. ALS, were 99.90%, 99.80%, 100%, 99.75%, 99.90%, 99.55%, and 99.68% under 10-sec time window with KNN. This study successfully developed an NDD gait classification based on MSE and machine learning classifiers. Full article

In this study, for energy compensation in the whole-angle control of Hemispherical Resonator Gyro (HRG), the dynamical equation of the resonator, which is excited by parametric excitation of the discrete electrode, is established, the stability conditions are analyzed, and the method of the double-frequency parametric excitation by the discrete electrode is derived. To obtain the optimal parametric excitation of the resonator, the total energy stability of the resonator is simulated for the evolution of the resonator vibration with different excitation parameters and the free precession of the standing wave by the parametric excitation. In addition, the whole-angle control of the HRG is designed, and the energy compensation of parametric excitation is proven by the experiments. The results of the experiments show that the energy compensation of the HRG in the whole-angle control can be realized using discrete electrodes with double-frequency parametric excitation, which significantly improves the dynamic performance of the whole-angle control compared to the force-to-rebalance. Full article

A digital closed-loop system design of a microelectromechanical systems (MEMS) disk resonator gyroscope (DRG) is proposed in this paper. Vibration models with non-ideal factors are provided based on the structure characteristics and operation mode of the sensing element. The DRG operates in force balance mode with four control loops. A closed self-excited loop realizes stable vibration amplitude on the basis of peak detection technology and phase control loop. Force-to-rebalance technology is employed for the closed sense loop. A high-frequency carrier loaded on an anchor weakens the effect of parasitic capacitances coupling. The signal detected by the charge amplifier is demodulated and converted into a digital output for subsequent processing. Considering compatibility with digital circuits and output precision demands, a low passband sigma-delta (ΣΔ) analog-to-digital converter (ADC) is implemented with a 111.8dB signal-to-noise ratio (SNR). The analog front-end and digital closed self-excited loop is manufactured with a standard 0.35 µm complementary metal-oxide-semiconductor (CMOS) technology. The experimental results show a bias instability of 2.1 °/h and a nonlinearity of 0.035% over the ± 400° full-scale range. Full article