scholarly journals An Improved Method for Spot Position Detection of a Laser Tracking and Positioning System Based on a Four-Quadrant Detector

Sensors ◽  
2019 ◽  
Vol 19 (21) ◽  
pp. 4722 ◽  
Author(s):  
Zhang ◽  
Guo ◽  
Zhang ◽  
Zhao
Keyword(s):  
Least Squares ◽  
Detection Accuracy ◽  
Moving Target ◽  
Positioning System ◽  
Improved Method ◽  
Laser Tracking ◽  
Least Squares Fitting ◽  
Position Detection ◽  
Operation Speed ◽  
Four Quadrant

For the laser tracking and positioning system of a moving target using a four-quadrant detector, the accuracy of laser spot position detection has a serious impact on the tracking performance of the system. For moving target tracking, the traditional spot position detection method of a four-quadrant detector cannot give better consideration to both detection accuracy and operation speed. In view of this, an improved method based on piecewise low-order polynomial least squares fitting and a Kalman filter is proposed. Firstly, the tracking and positioning mathematical model of the system is created, and the experimental device is established. Then, the shortcomings of traditional methods are analyzed, and the improved method and the real-time tracking and positioning algorithm of the system are studied. Finally, through the experiment, the system operation effects are compared and analyzed before and after the improvement. The experimental results of system dynamic tracking show that, the least squares fitting of the experimental data using a 5-segment and quadratic polynomial can achieve better results. By using the improved method, the maximum tracking distance of a moving object is increased from 12 m to more than 30 m. At a distance of 7.5 m, the maximum tracking speed can reach 2.11 m/s, and the root mean square error (RMSE) of the position is less than 4.59 mm. At 15.5 m, the maximum tracking speed is 2.04 m/s and the RMSE is less than 5.42 mm. Additionally, at 23.5 m, it is 1.13 m/s and 5.71 mm.

Analysis to Data Processing Method in Differential Barometric Altimeter

2014 ◽  
Vol 614 ◽  
pp. 448-451
Author(s):  
Zheng Qun Hu
Keyword(s):  
Data Processing ◽  
Least Squares ◽  
Kalman Filtering ◽  
Good Accuracy ◽  
Processing Method ◽  
Positioning System ◽  
Application Performance ◽  
Least Squares Fitting ◽  
Data Processing Method ◽  
High Dynamic

Differential barometric altimeter is with good accuracy in positioning system. There is different elevation accuracy with one type sensor under different filtering models. We compare application performance between the variable weighted Kalman filter and the least-squares fitting of data processing in the differential barometric altimetry system. Experiments show that Kalman filtering is more suitable for measuring high dynamic model and least-squares fitting way is more suitable in a static altimeter model.

Study on Main Factors Affecting Position Detection Accuracy of Four-Quadrant Detector

2015 ◽  
Vol 42 (12) ◽  
pp. 1217002 ◽  
Author(s):  
张辉 Zhang Hui ◽  
陈云善 Chen Yunshan ◽  
耿天文 Geng Tianwen ◽  
吴佳彬 Wu Jiabin ◽  
陈涛 Chen Tao
Keyword(s):  
Detection Accuracy ◽  
Factors Affecting ◽  
Position Detection ◽  
Main Factors ◽  
Four Quadrant

Application of the Least Squares Fitting in Mine Optical Fiber Carbon Dioxide Monitoring System

2013 ◽  
Vol 278-280 ◽  
pp. 983-987 ◽  
Author(s):  
Ting Ting Zhang ◽  
Xin Wang ◽  
Yu Bin Wei ◽  
Chang Wang ◽  
Tong Yu Liu
Keyword(s):  
Carbon Dioxide ◽  
Optical Fiber ◽  
Least Squares ◽  
Monitoring System ◽  
Coal Mine ◽  
Tunable Diode Laser ◽  
Detection Accuracy ◽  
Minimum Detectable Concentration ◽  
Least Squares Fitting ◽  
Fitting Method

Carbon dioxide is one of the important signature gases in spontaneous combustion forecasting of coal goaf area. In the mine limited ventilation environment, concentration of CO2 directly affects the health of coal mines. So a new application of the least squares fitting method in Coal Mine gas monitoring was introduced. The optical fiber CO2 monitoring system which based on this method and tunable diode laser absorption spectroscopy (TDLAS) technology was used in Coal Mine beam tube system, and selected a near-infrared wavelength 1609.117nm fiber-coupled distributed feedback laser (DFB) as light source. Goaf area gas concentrations were directly calculated by the least squares fitting method which also simplified the calibration operation that used only one point to calibrate. Compared to electronic CO2 detector, this improved system has very high detection accuracy and stability. In the condition of 1.4m gas cell, the minimum detectable concentration is 0.05%, and the minimum detectable spectral absorption rate can up to , response time≤60s.

scholarly journals A Method for Improving the Detection Accuracy of the Spot Position of the Four-Quadrant Detector in a Free Space Optical Communication System

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7164
Author(s):  
Xuan Wang ◽  
Xiuqin Su ◽  
Guizhong Liu ◽  
Junfeng Han ◽  
Kaidi Wang ◽  
...  
Keyword(s):  
Optical Communication ◽  
Communication System ◽  
Detection Accuracy ◽  
Free Space Optical Communication ◽  
Free Space Optical ◽  
Optical Communication System ◽  
Detection Model ◽  
Position Detection ◽  
Space Optical Communication ◽  
Four Quadrant

In a free space optical communication system, the beacon light will lose most of its energy after long-distance transmission, and the background light from the universe will strongly interfere with it. The four-quadrant detector (4QD) has been widely used in optical communication systems as a high-precision spot position detection sensor. However, if the light signal falling on the 4QD is too weak, the electrical signal of the output position will be very weak, and it will easily be affected by or even submerged in noise. To solve this problem, we propose a method for improving the spot position detection accuracy. First, we analyzed the solution relationship between the actual position of the spot and the output signal of the 4QD, with a Gaussian spot as the incident light model. The output current signal of the detector was then transimpedance-amplified by an analog circuit and the output voltage signal with noise was digitally filtered. An error compensation factor and the gap size of the detector were introduced into the traditional spot position detection model. High-precision spot position information for the 4QD in a complex environment was then obtained using the improved spot position detection model. Experimental results show that the maximum spot position detection error for this method was only 0.0277 mm, and the root mean square error was 0.0065 mm, when the 4QD was in a high background noise environment. The spot position detection accuracy was significantly improved compared with traditional detection algorithms. Real-time detection can therefore be achieved in practical applications.

scholarly journals The nanofluidic confinement apparatus: studying confinement-dependent nanoparticle behavior and diffusion

2018 ◽  
Vol 9 ◽  
pp. 301-310 ◽  
Author(s):  
Stefan Fringes ◽  
Felix Holzner ◽  
Armin W Knoll
Keyword(s):  
Polymer Surface ◽  
Diffusion Constant ◽  
Numerical Aperture ◽  
Lateral Diffusion ◽  
Vertical Position ◽  
Detection Accuracy ◽  
Illumination Time ◽  
Electroviscous Effect ◽  
Position Detection ◽  
Hydrodynamic Effects

The behavior of nanoparticles under nanofluidic confinement depends strongly on their distance to the confining walls; however, a measurement in which the gap distance is varied is challenging. Here, we present a versatile setup for investigating the behavior of nanoparticles as a function of the gap distance, which is controlled to the nanometer. The setup is designed as an open system that operates with a small amount of dispersion of ≈20 μL, permits the use of coated and patterned samples and allows high-numerical-aperture microscopy access. Using the tool, we measure the vertical position (termed height) and the lateral diffusion of 60 nm, charged, Au nanospheres as a function of confinement between a glass surface and a polymer surface. Interferometric scattering detection provides an effective particle illumination time of less than 30 μs, which results in lateral and vertical position detection accuracy ≈10 nm for diffusing particles. We found the height of the particles to be consistently above that of the gap center, corresponding to a higher charge on the polymer substrate. In terms of diffusion, we found a strong monotonic decay of the diffusion constant with decreasing gap distance. This result cannot be explained by hydrodynamic effects, including the asymmetric vertical position of the particles in the gap. Instead we attribute it to an electroviscous effect. For strong confinement of less than 120 nm gap distance, we detect the onset of subdiffusion, which can be correlated to the motion of the particles along high-gap-distance paths.

scholarly journals An Error-Reduction Method for Temporal Phase Unwrapping Based on Double Three-Step Phase-Shifting and Least-Squares Fitting

2012 ◽  
Vol 6-7 ◽  
pp. 76-81
Author(s):  
Yong Liu ◽  
Ding Fa Huang ◽  
Yong Jiang
Keyword(s):  
Least Squares ◽  
Reduction Method ◽  
Intermediate Phase ◽  
Error Reduction ◽  
Phase Unwrapping ◽  
Phase Shifting ◽  
Surface Measurement ◽  
Acquisition Time ◽  
Least Squares Fitting ◽  
Temporal Phase

Phase-shifting interferometry on structured light projection is widely used in 3-D surface measurement. An investigation shows that least-squares fitting can significantly decrease random error by incorporating data from the intermediate phase values, but it cannot completely eliminate nonlinear error. This paper proposes an error-reduction method based on double three-step phase-shifting algorithm and least-squares fitting, and applies it on the temporal phase unwrapping algorithm using three-frequency heterodyne principle. Theoretical analyses and experiment results show that this method can greatly save data acquisition time and improve the precision.

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