Open-loop Detection Research Articles

A Novel Pre-Synchronization Control Method Based on Open-Loop Phase Detection for the Maritime VSC-HVDC System

Maritime island grids based on renewable energy are being rapidly developed, which poses a new challenge to the traditional pre-synchronization process of grid connection. Aiming at the problems of impulse current out of limit and long steady-state regulation time, a novel pre-synchronization control method is provided based on open-loop phase detection, which is realized by replacing the frequency detection method of the difference judgment part. The open-loop detection model of voltage phase and amplitude based on the synchronous rotating coordinate system is established first. Then the voltage phase is linearized to control the output frequency and finally reduces the voltage deviation through the compensation of virtual power to achieve the effect of a smooth grid connection. The novel pre-synchronization method has a fast response speed and no regulator effect, which can synchronize the actual values of output voltage amplitude, phase, and frequency. Simulation results verify the excellent performance of the proposed method in island stable operation and grid connection under disturbance.

In-Run Scale Factor Compensation for MEMS Gyroscope Without Calibration and Fitting

This paper presents an in-run scale factor error compensation for the micro-electro-mechanical system (MEMS) gyroscope without system calibration and data fitting. The causes of three scale factor errors (instability, nonlinearity, and asymmetry) are analyzed. Next, the instability and nonlinearity by open-loop detection (Mode I), and closed-loop detection (Mode II) are discussed according to the specific comb capacitance and the front-end detection circuit. The closed-loop detection transfer function is studied, and a series of equivalent conversions are performed to obtain a method (Mode III) for improving the temperature stability of scale factor. The results of the experiment indicated that the nonlinearity and asymmetry of the Mode II and Mode III are increased by 1.8 times and 3.5 times than that of Mode I. Furthermore, the instability of Mode II and Mode III is reduced by 10 times and 19 times over -20°C to 40°C. Besides, the mode III does not affect the static and dynamic performance of gyroscope according to the test results of bias and bandwidth.

Optimization of a synthetic jet based piezoelectric air pump and its application in electronic cooling

In this paper, the optimization is carried out for a synthetic jet based piezoelectric air pump. The structural parameters which affect the output flowrate are determined and orthogonal test method is used to find out the optimal values of these parameters. Driven by a 150 Vpp, 3.15 kHz sinusoidal voltage signal, the optimized pump reaches its maximum output flowrate of 2.79 L/min, which is 32.9% higher than that before optimization. Using the synthetic jet based piezoelectric air pump as gas source, an open-loop detection and closed-loop control system is built for electronic cooling. The open-loop experiments show that the heater’s surface temperature can be maintained at around 97.9 °C when the cooling distance is 60 mm, which is 32.5% lower than the initial value. The closed-loop control system can limit the temperature within the set interval. Both the open and closed-loop system show that the synthetic jet based piezoelectric air pump has application prospects in the field of electronic cooling.

Automatic Frequency Tuning Technology for Dual-Mass MEMS Gyroscope Based on a Quadrature Modulation Signal.

In order to eliminate the frequency mismatch of MEMS (Microelectromechanical Systems) gyroscopes, this paper proposes a frequency tuning technology based on a quadrature modulation signal. A sinusoidal signal having a frequency greater the gyroscope operating bandwidth is applied to the quadrature stiffness correction combs, and the modulation signal containing the frequency split information is then excited at the gyroscope output. The effects of quadrature correction combs and frequency tuning combs on the resonant frequency of gyroscope are analyzed. The tuning principle based on low frequency input excitation is analyzed, and the tuning system adopting this principle is designed and simulated. The experiments are arranged to verify the theoretical analysis. The wide temperature range test (-20–60) demonstrates the reliability of the tuning system with a maximum mismatch frequency of less than 0.3 Hz. The scale factor test and static test were carried out at three temperature conditions (−20 C, room temperature, 60 C), and the scale factor, zero-bias instability, and angle random walk are improved. Moreover, the closed-loop detection method is adopted, which improves the scale factor nonlinearity and bandwidth under the premise of maintaining the same static performances compared with the open-loop detection by tuning.

Demodulation phase angle compensation for quadrature error in decoupled dual-mass MEMS gyroscope

This paper proposes a demodulation phase angle compensation (DPAC) for dual-mass MEMS gyroscopes with small frequency split (Δω) and low-quality factor (Q value), to reduce the quadrature interference on Coriolis signal output. The harmful contribution of quadrature error and demodulation phase angle drift to the gyroscope performances is analyzed and quantified. The quadrature stiffness correction (QSC) system based on DPAC is redesigned, and it was analyzed that the QSC would reduce the Δω and then affect the performances of the gyroscope. Wherein, the DPAC algorithm is implemented by a back propagation neural network. Finally, the experiments are arranged to verify the theoretical analysis. DPAC experiments were performed for both open-loop detection method and QSC method, respectively, for open-loop detection without DPAC (test 1), open-loop detection with DPAC (test 2), QSC without DPAC (test 3), and QSC with DPAC (test 4). The scale factor results based on these four tests are 15.384, 15.441, 16.652, and 16.731 mV / deg / s, respectively. When tests 2, 3, and 4 are compared to test 1, the bias stability results improved by 88%, 84%, and 97%, and the angle random walk improved by 28%, 23%, and 34%, respectively. Test 4 is proved to be the best type for bias performances, as is the case with a temperature range experiment from 60°C to −40 ° C, but the performances of its scale factor deteriorated. Moreover, the bandwidth is reduced by 4 Hz because of the QSC.

Comparison of Three Automatic Mode-Matching Methods for Silicon Micro-Gyroscopes Based on Phase Characteristic

In this paper, we investigated the method of automatic matching of the resonant frequencies for the decoupled dual-mass $z$ -axis silicon micro-gyroscopes. The structure of the studied gyroscope is first presented, which features the tuning combs for adjusting the resonant frequency, suppressing the quadrature error, and applying the feedback force. According to the phase characteristic of oscillators, different automatic frequency tuning loops are then designed to match the resonant frequencies of the drive and detection modes. Theoretical analysis is made to display the operation principles. In addition, they are verified and optimized by numeric simulations using the Simulink tool in MATLAB. Finally, by means of Labview Field Programmable Gate Array (FPGA), a digital hardware tool, these loops are tested on a fabricated and packaged gyroscope prototype. By comparison, it is found that when the automatic matching method under the external force is combined with the quadrature nulling method and the Coriolis closed-loop detection, the gyroscope is able to operate under real-time mode matching with a stable and small frequency split below 1 Hz. The performance of the prototype using this tuning method is: 1) the scale factor is 10.91 mV/°/s; 2) the input range is ±120°/s with nonlinearity of 0.1%; and 3) the bandwidth is 32 Hz. The frequency split varies by about 0.15 Hz under the open-loop detection and about 0.26 Hz under the closed-loop detection when the environment temperature changes by 80 °C.

Improvement of bias stability for a micromachined gyroscope based on dynamic electrical balancing of coupling stiffness

We present a dynamic electrical balancing of coupling stiffness for improving the bias stability of micromachined gyroscopes, which embeds the coupling stiffness in a closed-loop system to make the micromachined gyroscope possess more robust bias stability by suppressing the variation of coupling stiffness. The effect of the dynamic electrical balancing control is theoretically analyzed and implemented using a silicon micromachined gyroscope as an example case. It has been experimentally shown that, comparing with open loop detection, the proposed method increased the stability of the amplitude of the mechanical quadrature signal by 38 times, and therefore improved the bias stability by 5.2 times from 89 to 17 deg/h , and the temperature stability of scale factor by 2.7 times from 622 to 231 ppm/°C . Experimental results effectively indicated the theoretical model of dynamic electrical balancing of coupling stiffness.

Digitalization optical open loop test system for fiber optic gyroscope

In order to receive and process the open loop signal from fiber optic gyroscopes speedily, stably and expediently, and to realize the amity interface between human and machine, a digital system that can convert GPIB (general purpose interface bus) parallel bus into Universal Serial Bus is developed. All the interface functions of GPIB and the hardware system are realized through FPGA. With a digital sampling and processing system designed with VC++ in Windows platform, the real-time controlling procedure, high-speed receiving and sending data can be carried out, and the results can be displayed too. So the design of the system is flexible, the reliability and the stability are improved, error rate is no more than 10−11, the highest bit rate is 8 MB/s and the open loop detection system for optic fiber gyros achieves standardization and complete digitalization simultaneously.

Theory of light detection in the presence of feedback

The usual open-loop quantum and semiclassical theories of light detection are extended to include closed-loop operation in which there is feedback from the detector to the source. It is shown that the unmistakable signatures of nonclassical light associated with open-loop detection, such as sub-shot-noise spectra and sub-Poisson photo-counts, do not carry over to closed-loopsystems. This behavior is illustrated through quantitatively indistinguishable quantum and semiclassical analyses of two recent closed-loop experiments in which sub-Poisson photocount statistics were produced. It turns out that if the open-loop illumination does not require the use of quantum photodetection theory, then neither does the closed-loop illumination. Conversely, if the open-loop illumination is nonclassical, then the closed-loop behavior must be analyzed quantum mechanically. The use of nonclassical field correlations to obtain light beams that give sub-Poisson open-loop photocounts from these closed-loop arrangements is discussed and generalized into a synthesis procedure for producing light beams with arbitrary open-loop photocount statistics.