Ultrasound imaging technology plays an important role to assist doctors in diagnosing thyroid nodules. The tissue structure around the thyroid is very complex, which makes it difficult to segment and extract the ultrasound image of thyroid nodules accurately. For address this problem, this paper proposes a model algorithm for thyroid nodule ultrasound image segmentation using ASPP fusion features. First, spatial pyramid pooling and depthwise separable convolution are combined in order to solve the problem that the size of the mapping feature will change in the process of better capturing the context information. Besides, Atrous Spatial Pyramid Pooling (ASPP) is proposed to achieve the purpose of processing input image channel and spatial information separately. In order to appropriately reduce the dimension and size of feature images, a 1×1 convolution operation is performed before each convolution calculation, and the model size is optimized. In the decoding stage, decoder module appropriately adjusts the feature map with a relatively low resolution previously from decoder module, and sets the output channel number of two convolutions to the same value. All features have the same dimension by adjustment, and features can be fused by element-wise summation. Finally, Dice Similarity Coefficient (DSC), Prevent Match (PM) and Correspondence Patio (CR) are used as evaluation criteria to compare with other model algorithms. The experimental results show that the proposed model can significantly improve the segmentation effect of ultrasound images for thyroid nodules compared with traditional models.

Bias stability is an important performance indicator for MEMS gyroscopes. In this paper, a gyroscope zero rate output (ZRO) model under force-to-rebalance (FTR) closed-loop detection is presented, and the effect of circuit phase delay and various noises on the ZRO is analyzed. Based on the fact that the two feedback forces in the FTR system are insensitive to the phase delay of the sense mode, while they are sensitive to the phase delay of the drive mode, a method for quickly calculating the circuit phase delay is proposed, and an all-pass filter is used to realize one-time automatic compensation for the phase delay in the drive mode. The control system is implemented with an FPGA. The experimental results show that this method can be used to accurately calculate the circuit phase delay and that phase compensation can be used to effectively reduce the effect of quadrature error on ZRO. This technique provides bias instability and angle random walk performances of 0.338° h ⁻¹ and 0.061 ° (√h) ⁻¹ , respectively. In addition, the sensitivity of ZRO to temperature at 0 °C to 70 °C has reached 0.001°/s/°C.

The force-to-rebalance (FTR) closed-loop detection method is commonly used to expand the bandwidth (BW) for micro-electro-mechanical system (MEMS) gyroscopes with low-frequency split and high-quality factors. However, the relationship between the BW and output noise is often incompatible; thus, reducing the detection accuracy of the gyroscope. This paper presents an analysis of the BW and noise spectra under modulation-demodulation FTR gyroscopes. The expressions for the BW and the noise-equivalent rate (NER) spectrum are derived to explore the effects of the loop gain on the BW and NER. It is demonstrated that the gain of the amplifier circuit is maximally transferred to the vibration displacement signal conversion part, which can reduce the output noise without affecting the BW. The simulation and experimental results on the Cobweb-like disk resonator gyroscope show that the derived expressions of BW and NER are correct, and the noise optimization method is effective, which provides an idea for the realization of a high-precision MEMS gyroscope.

In order to solve the problem where existing mode-matching methods in microelectromechanical systems (MEMS) vibrating gyroscopes fail to meet real-time and reliability requirements, this paper presents a novel method to accomplish automatic and real-time mode-matching based on phase-shifted 45° additional force demodulation (45° AFD-RM). The phase-shifted 45° additional force signal has the same frequency as the quadrature force signal, but it is phase-shifted by 45° and applied to the sense mode. In addition, two-way phase-shifted 45° demodulations are used at the sense-mode detection output to obtain a phase metric that is independent of the Coriolis force and can reflect the mode-matching state. Then, this phase metric is used as a control variable to adaptively control the tuning voltage, so as to change the sense-mode frequency through the negative stiffness effect and ultimately achieve real-time mode-matching. Simulation and experimental results show that the proposed 45° AFD-RM method can achieve real-time matching. The mode frequency split is controlled within 0.1 Hz, and the gyroscope scale factor, zero-bias instability, and angle random walk are effectively improved.

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.

This study analyses the transfer path of electrical feed-through noise in the electromechanical amplitude modulation detection circuit of a micro-electro-mechanical system vibrating gyroscope. By considering the feed-through, circuit and mechanical thermal noises, a new noise model in the force-to-rebalance closed-loop detection is constructed, and the expression of the noise-equivalent rotation rate spectrum is given. In addition, the influences of factors such as circuit gain, feedback coefficient and frequency split on the contribution of noise are analysed. The analysis shows that the back-end injection noise is the main factor affecting angle random walk (ARW) for high Q-value gyroscopes. Through actual measurements, it was found that the feed-through noise at the carrier frequency of the feedback circuit was the main source of the back-end noise. After noise optimization, the ARW of the detection output decreased from 0.148 ° ​ ​ / hr to 0.017 ° ​ ​ / hr , which was an improvement of about 8.7 times.