Real-Time Estimation and Calibration of GLONASS Inter-Frequency Phase and Code Bias

2019 ◽  
Vol 73 (3) ◽  
pp. 746-762 ◽  
Author(s):  
Zhixin Yang ◽  
Hui Liu ◽  
Yidong Lou ◽  
Bao Shu ◽  
Longwei Xu ◽  
...  
Keyword(s):  
Real Time ◽  
Elevation Angle ◽  
Vertical Direction ◽  
Time Estimation ◽  
Calibration Method ◽  
Mean Value ◽  
Time Calibration ◽  
Calibration Methods ◽  
Code Bias ◽  
Frequency Phase

The frequency division multiple access (FDMA) strategy used in GLONASS causes inter-frequency phase bias (IFPB) and inter-frequency code bias (IFCB) between receivers from different manufacturers. The existence of IFPB and IFCB significantly increases the difficulties of fixing GLONASS ambiguity and limits the accuracy and reliability of GLONASS positioning. Moreover, the initial value of IFPB and IFCB may be unavailable or unreliable with the increasing number of receivers from different manufacturers in recent years. In this study, a real-time and reliable calibration algorithm of IFPB and IFCB based on multi-GNSS assistance is proposed by providing a fixed solution. Real-time IFPB rate and IFCB can be obtained using this algorithm without the initial IFPB and IFCB. The IFPB rate for all GLONASS satellites and IFCB for each GLONASS satellite are estimated due to different characteristics of IFPB and IFCB. IFPB calibration can be divided into constant and real-time IFPB calibrations to meet the different positioning requirements. Results show that constant IFPB rate has only 2 mm difference from the mean value of real-time IFPB rate. The IFPB rate and IFCB estimated by this algorithm have excellent stability, and the change in reference satellite cannot affect the results of IFPB rate and the stability of IFCB. The centimetre-level positioning results can be obtained using two calibration methods, and the positioning results with real-time calibration method are 10%–20% better than those with the constant calibration method. Under satellite-deprived environments, the improvements of multi-GNSS positioning accuracy with constant inter-frequency bias calibration gradually increase as the satellite cut-off elevation angle increases compared with GPS/BDS, which can reach up to 0·9 cm in the vertical direction.

A real-time calibration method for the systematic errors of a star sensor and gyroscope units based on the payload multiplexed

Optik ◽  
2021 ◽  
Vol 225 ◽  
pp. 165731
Author(s):  
Zhongguang Yang ◽  
Xiaocheng Zhu ◽  
Zhiming Cai ◽  
Wen Chen ◽  
Jinpei Yu
Keyword(s):  
Real Time ◽  
Calibration Method ◽  
Systematic Errors ◽  
Star Sensor ◽  
Time Calibration

A New Linearly Polarized Microwave Radiometer Calibration Source

2012 ◽  
Vol 500 ◽  
pp. 341-347
Author(s):  
Xin Biao Wang ◽  
Chang Zeng ◽  
Jing Li ◽  
Jing Shan Jiang
Keyword(s):  
Real Time ◽  
Microwave Radiometer ◽  
Noise Temperature ◽  
Calibration Method ◽  
Calibration Source ◽  
Radiometer Calibration ◽  
Time Calibration ◽  
Linearly Polarized ◽  
Calibration Device

This paper introduces a calibration device for microwave (millimeter and submillimeter) radiometer. The device can provide the microwave radiometer continuously variable linearly polarized noise temperature. The paper also introduces a real-time calibration method to achieve the microwave radiometer calibration, and the test of microwave radiometer sensitivity and linearity.

scholarly journals An Online Calibration Method for a Galvanometric System Based on Wavelet Kernel ELM

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1353 ◽  
Author(s):  
Wugang Zhang ◽  
Wei Guo ◽  
Chuanwei Zhang ◽  
Shuanfeng Zhao
Keyword(s):  
Real Time ◽  
Calibration Method ◽  
System Structure ◽  
Data Sets ◽  
Position Measurement ◽  
Online Calibration ◽  
Time Performance ◽  
Calibration Methods ◽  
Testing Data ◽  
Mean Square Errors

The online calibration method of a two-dimensional (2D) galvanometer requires both high precision and better real-time performance to meet the needs of moving target position measurement, which presents some challenges for traditional calibration methods. In this paper, a new online calibration method is proposed using the wavelet kernel extreme learning machine (KELM). Firstly, a system structure is created and its experiment setup is established. The online calibration method is then analyzed based on a wavelet KELM algorithm. Finally, the acquisition methods of the training data are set, two groups of testing data sets are presented, and the verification method is described. The calibration effects of the existing methods and wavelet KELM methods are compared in terms of both accuracy and speed. The results show that, for the two testing data sets, the root mean square errors (RMSE) of the Mexican Hat wavelet KELM are reduced by 16.4% and 38.6%, respectively, which are smaller than that of the original ELM, and the standard deviations (Sd) are reduced by 19.2% and 36.6%, respectively, indicating the proposed method has better generalization and noise suppression performance for the nonlinear samples of the 2D galvanometer. Although the online operation time of KELM is longer than ELM, due to the complexity of the wavelet kernel, it still has better real-time performance.

Dynamic Real-Time Calibration Method for Fiber Bragg Grating Wavelength Demodulation System Based on Tunable Fabry-Perot Filter

2015 ◽  
Vol 35 (8) ◽  
pp. 0806006 ◽  
Author(s):  
王鹏 Wang Peng ◽  
赵洪 Zhao Hong ◽  
刘杰 Liu Jie ◽  
陈俊岐 Chen Junqi ◽  
韩旭 Han Xu
Keyword(s):  
Fiber Bragg Grating ◽  
Real Time ◽  
Calibration Method ◽  
Bragg Grating ◽  
Time Calibration ◽  
Fabry Perot

Real Time Automatic Calibration of Flow Meters for Real-Time Hydraulic Modelling

2014 ◽  
Author(s):  
Norense Okungbowa ◽  
Noorallah Rostamy
Keyword(s):  
Real Time ◽  
Calibration Method ◽  
Operating Conditions ◽  
Time Averaging ◽  
Flow Ratio ◽  
Flow Meter ◽  
Flow Meters ◽  
Detection Techniques ◽  
Time Calibration ◽  
Dependent Flow

Performance of flow meters is often a function of flow rate as well as properties (density and viscosity) of the fluid measured by the meters. Since comparison of flow meter readings is a key parameter in leak detection techniques, it is desirable that the readings from the flow meters are accurate and comparable. The idea behind real-time calibration of flow meters is to calibrate a flow meter (called the dependent flow meter) against another flow meter (called the independent flow meter) that is assumed to read correctly. The real-time calibration method is useful under two main conditions: i) when the reference flow meter has been calibrated to a high degree of accuracy and the flow readings from the meter are accurate; ii) when the pipeline operating conditions support the fact that the meter-in flow at one station equals the meter-out flow at the other station. By determining the deviation of the dependent flow meter reading from the independent flow meter reading, a time-averaged flow ratio is calculated. However, the flow ratio calculation and time averaging is only updated at prescribed conditions. The proper correction factor is ascertained and then applied to the dependent flow meter reading. The main advantage of using this technique is that the flow meter repeatability is reduced over time below the nominal accuracy of the dependent meter. Note that the term “calibration” in this context does not refer to the standard method of calibrating flow meter with a ‘prover’ but a technique to calculate correction multiplier for flow meter in other to improve the performance of hydraulic models.

Decentralized Feedback Control of Pumping Losses and NOx Emissions in Diesel Engines

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Rasoul Salehi ◽  
Jason Martz ◽  
Anna Stefanopoulou ◽  
Bruce Vernham ◽  
Lakshmidhar Uppalapati ◽  
...  
Keyword(s):  
Real Time ◽  
Diesel Engines ◽  
Test Procedure ◽  
Time Derivative ◽  
Time Estimation ◽  
Mean Value ◽  
Boost Pressure ◽  
Nox Emissions ◽  
Control Loops ◽  
Engine Model

A novel decentralized control architecture is developed based on a feedback from the pressure difference across the engine which is responsible for the pumping losses and the exhaust gas recirculation (EGR) flow in diesel engines. The controller is supplemented with another feedback loop based on NOx emissions measurement. Aiming for simple design and tuning, the two control loops are designed and discussed: one manipulates the variable geometry turbine (VGT) actuator and the other manipulates the EGR valve. An experimentally validated mean-value diesel engine model is used to analyze the best pairing of actuators and set points. Emphasis is given to the robustness of this pairing based on gain changes across the entire operating region, since swapping the pairing needs to be avoided. The VGT loop is designed to achieve fast cylinder air charge increase in response to a rapid pedal tip-in by a feedforward term based on the real-time derivative of the desired boost pressure. The EGR loop relies on a feedback measurement from a NOx sensor and a real-time estimation of cylinder oxygen ratio, χcyl. The engine model is used for evaluating the designed controllers over the federal test procedure (FTP) for heavy duty (HD) vehicles. Results indicate that the control system meets all targets, namely fast air charge and χcyl control during torque transients, robust NOx control during steady-state operation, and controlled pumping losses in all conditions.

scholarly journals Continuous Monitoring of Differential Reflectivity Bias for C-Band Polarimetric Radar Using Online Solar Echoes in Volume Scans

2019 ◽  
Vol 11 (22) ◽  
pp. 2714
Author(s):  
Chu ◽  
Liu ◽  
Zhang ◽  
Kou ◽  
Li
Keyword(s):  
High Frequency ◽  
Continuous Monitoring ◽  
Information Science ◽  
Elevation Angle ◽  
Gaussian Model ◽  
Likelihood Estimation ◽  
Polarimetric Radar ◽  
Time Calibration ◽  
Calibration Methods ◽  
Differential Reflectivity

The measurement error of differential reflectivity (ZDR), especially systematic ZDR bias, is a fundamental issue for the application of polarimetric radar data. Several calibration methods have been proposed and applied to correct ZDR bias. However, recent studies have shown that ZDR bias is time-dependent and can be significantly different on two adjacent days. This means that the frequent monitoring of ZDR bias is necessary, which is difficult to achieve with existing methods. As radar sensitivity has gradually been enhanced, large amounts of online solar echoes have begun to be observed in volume-scan data. Online solar echoes have a high frequency, and a known theoretical value of ZDR (0 dB) could thus allow the continuous monitoring of ZDR bias. However, online solar echoes are also affected by low signal-to-noise ratio and precipitation attenuation for short-wavelength radar. In order to understand the variation of ZDR bias in a C-band polarimetric radar at the Nanjing University of Information Science and Technology (NUIST-CDP), we analyzed the characteristics of online solar echoes from this radar, including the daily frequency of occurrence, the distribution along the radial direction, precipitation attenuation, and fluctuation caused by noise. Then, an automatic method based on online solar echoes was proposed to monitor the daily ZDR bias of the NUIST-CDP. In the proposed method, a one-way differential attenuation correction for solar echoes and a maximum likelihood estimation using a Gaussian model were designed to estimate the optimal daily ZDR bias. The analysis of three months of data from the NUIST-CDP showed the following: (1) Online solar echoes occurred very frequently regardless of precipitation. Under the volume-scan mode, the average number of occurrences was 15 per day and the minimum number was seven. This high frequency could meet the requirements of continuous monitoring of the daily ZDR bias under precipitation and no-rain conditions. (2) The result from the proposed online solar method was significantly linearly correlated with that from the vertical pointing method (observation at an elevation angle of 90°), with a correlation coefficient of 0.61, suggesting that the proposed method is feasible. (3) The day-to-day variation in the ZDR bias was relatively large, and 32% of such variations exceeded 0.2 dB, meaning that a one-time calibration was not representative in time. Accordingly, continuous calibration will be necessary. (4) The ZDR bias was found to be largely influenced by the ambient temperature, with a large negative correlation between the ZDR bias and the temperature.

scholarly journals A New Calibration Method for the Real-Time Calculation of Dynamic Safety Following Distance under Railway Moving Block System

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Deng Pan ◽  
Qing Luo ◽  
Liting Zhao ◽  
Chuansheng Zhang ◽  
Zejun Chen
Keyword(s):  
Real Time ◽  
High Speed ◽  
Calibration Method ◽  
Hyperbolic Function ◽  
High Speed Train ◽  
The Real ◽  
Relative Safety ◽  
Time Calibration ◽  
Study Results ◽  
Time Calculation

Only the actual following distance that is a little greater than the optimum safety following distance at any time can make the following train move in safety and efficiency. For this purpose, a new calibration method is studied for the real-time calculation of the dynamically optimum safety following distance. To cope with the complex situations of train following operation, the mathematic model of train deceleration operation based on the hyperbolic function with a variable acceleration control strategy is established to simulate the speed-changing behavior of high-speed train steered by the well-experienced driver. Using the evaluation of train behavior adjustment quality and the numerical analysis theory, we build the fitting function of the optimum absolute safety following distance changing with the following train’s velocity for the real-time calibration of safe following distance under absolute braking mode. And then, we discussed the real-time calculation of the optimum safety following distance under relative braking mode (i.e., the relative safety following distance). The study results will help a high-speed train to evaluate and optimize its own following behavior according to the current operation states of train following system, the actual following distance, and the absolute or relative safety following distance. The actual following distance is rationally controlled by the scientific adjustment of the following train’s behavior so that train following movement can be always safe, efficient, and smooth (comfortable).

scholarly journals A Real-Time Calibration Method of Kinect Recognition Range Extension for Media Art

2018 ◽  
Author(s):  
Sunghyun Kim ◽  
Won-hyung Lee
Keyword(s):  
Coordinate System ◽  
Real Time ◽  
Digital Media ◽  
Recognition Rate ◽  
Measurement Data ◽  
Calibration Method ◽  
Depth Image ◽  
Media Art ◽  
Fast Recognition ◽  
Time Calibration

Kinect is a device that has been widely used in many areas since it was released in 2010. Kinect SDK was announced in 2011 and used in many other areas than its original purpose, which was a controller for gaming. In particular, it has been used by a number of artists in digital media art since it is inexpensive and has a fast recognition rate. However, there is a problem. Kinect create 3D coordinates with a single 2D RGB image for x, y value - single depth image for z value. And this creates a significant limitation on the installation for interactivity of media art. Because the Cartesian XY coordinate and the spherical Z coordinate system are used in combination, depth error depending on the distance is generated, which makes real-time rotation recognition and coordinate correction difficult above coordinate system. This paper proposes a real-time calibration method of Kinect recognition range expansion for useful application in the digital media art area. The proposed method can recognize the viewer accurately by calibrating a coordinate in any direction in front of the viewer. 3,400 datasets witch acquire from experiment were measured as five stances: the 1m attention stance, 1m hands-up stance, 2m attention stance, 2m hands-up stance, and 2m hands-half-up stance, which were taken and recorded every 0.5 sec. The experimental results showed that the accuracy rate was improved about 11.5% compared with front measurement data according to Kinect reference installation method.

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