Accuracy Of Position Measurements Research Articles

Method for measuring non-stationary motion attitude based on MEMS-IMU array data fusion and adaptive filtering

The error characteristics of a typical commercial MEMS-IMU were analyzed. Using 15 ICM-42688 sensors, a 3*5 MEMS-IMU array was designed, and a weighted data fusion method based on Allan variance for the MEMS-IMU array was proposed. This effectively reduces the random measurement errors of the MEMS-IMU, providing a data foundation for the precise measurement of motion and attitude of robots, vehicles, aircraft, and other systems under low-cost conditions. The text describes a measurement method for non-stationary motion attitudes of sports vehicles based on adaptive Kalman-Mahony. Specifically, it first uses adaptive Kalman filter on array sensor data to calculate the measurement noise in real-time and adaptively adjust the filtering gain. Then, it determines the compensation coefficient of the accelerometer to the gyroscope angular velocity based on the motion state of the vehicle, and solves the attitude through complementary filtering to obtain the motion attitude quaternion. Finally, it converts it into the roll angle, pitch angle, and yaw angle of the sports vehicle. Experimental results show that the proposed MEMS-IMU array weighted data fusion method based on Allan variance has significant advantages over traditional single MEMS-IUM methods and traditional average weighting methods in reducing sensor angle random walk and zero drift instability. The proposed adaptive Kalman-Mahony attitude measurement method also shows a significant improvement in the accuracy of non-stationary motion attitude measurement compared to traditional methods.

Preliminary Analysis of Beam Position Monitor Accuracy

The beam position is the most important reference basis for the operation of synchrotron radiation light sources, particularly for commissioning the first-turn injection of fourth-generation light sources. To improve the accuracy of the beam position measurement, we analyzed methods for calculating the beam position, and a finite element calculation and the stretched wire calibration system were used to demonstrate the procedure. We proved the relationship between the coverage range, fitting order, scanning step size, and accuracy both theoretically and experimentally, which can provide a basis for selecting the appropriate fitting order for different operation stages of the accelerator. It was proved that the accuracy of beam position calculations using simplified polynomial coefficients is comparable to those without a simplified one, which can save resources for reading electronic processing. The testing results of a batch of beam position monitors (BPMs) were in good agreement with the finite element calculation results, and the small difference between the manufactured BPMs also proved that quality control was performed well, and it benefited from button sorting.

A confocal measurement method for surface profile variations and shell thickness uniformity of hemispherical shell resonator

Here we present a confocal measurement method for the precise measurements of variations in the inner and outer surface profiles (IOSPs) and shell thickness uniformity (STU) of the hemispherical shell resonator (HSR). In this method, the unilateral-shift-subtracting confocal technique is applied to determine the focus of the sensor on the IOSPs of the HSR. The normal tracking technique is employed for measuring the outer surface, while the normal direction of the outer surface serves as the reference for measuring the inner surface, thereby enhancing the accuracy of relative position measurements for the HSR. Furthermore, we applied a trajectory-prediction method to narrow down the scanning range of the confocal sensor, which significantly improved the measurement efficiency. The experimental results showed that the repeated accuracies of the proposed methods are better than 40 nm for IOSP variations measurement and better than 50 nm for HSR STU measurement.

VR interactive input system based on INS and binocular vision fusion

In virtual reality interactive input systems, real-time and accurate spatial position and pose measurement is key to achieving a natural user interface. This study explores the application of inertial measurement units and binocular vision fusion technology in virtual reality interactive input systems, with the aim of improving the tracking accuracy of the system through optimized pose models and visual algorithms. A virtual reality measurement technology that integrates inertial measurement units and binocular vision is proposed by using an improved Kalman filtering algorithm to process inertial measurement units data, and combining it with the SURF algorithm optimized binocular vision system. Experimental results showed that fusion technology could reduce sensor noise and bias, improve the accuracy of pose estimation, and promote stable and robust motion tracking in virtual reality systems. In the angle range of -90 ° to 90 °, the average absolute error of the fusion system compared to the simple inertial measurement units pose calculation decreased from 3.371 ° to 1.369 ° In the experiment of measuring distance with a binocular vision system, the average absolute error value decreased to 1.532 mm, and the error range of the marker within the distance range of 500 mm to 650 mm was controlled within -1.3 mm to 1.2 mm. This study provides an effective solution for achieving high-precision virtual reality interactive input systems and is meaningful for the advancement of virtual reality technology.

Design and implementation of a monitoring platform based on beidou high precision positioning technology

Traditional BDS positioning technology has limitations in accuracy, robustness, and availability in certain real-time monitoring applications. Therefore, this article designs and implements a monitoring platform based on Beidou high-precision positioning technology to solve the limitations of traditional BDS positioning technology and provide more accurate, reliable, and real-time positioning services. The research first analyzes and optimizes the positioning algorithms of the existing Beidou system to improve the accuracy of position measurement. Then apply the optimized algorithm to the system architecture of the monitoring platform to achieve high-precision positioning function. Finally, design a suitable user interface and data processing module so that users can easily obtain and analyze positioning data. Through experimental verification, this platform has achieved high accuracy and stability in position measurement. Users can obtain real-time location information through this platform and further analyze and process it.

Absolute attitude measurement based on multi-sensor fusion

In the field of positioning and navigation, the measurement and transmission of absolute attitude are often used in the initial calibration process of positioning and navigation equipment. This requires higher absolute attitude measurement accuracy and lower measurement complexity. In order to solve the problems of high complexity and time-consuming of traditional absolute attitude measurement, a multi-sensor fusion absolute attitude measurement method is proposed. This method uses an optical camera to calculate the angle offset, employs a biaxial inclination sensor to measure horizontal angles, and utilizes GNSS differential positioning to introduce true azimuth angle. The experimental results of the prototype show that under the condition of 60 m baseline length, the max uncertainty of yaw, pitch, and roll angle measurement is 14.13”, 4.41”, and 3.53” respectively, and the average single measurement time consumption is 2.73 minutes.

Real-time analysis of star sensor attitude accuracy

In the conventional methods of star sensor accuracy evaluation, neither the accuracy calculation formula nor the Monte Carlo method can comprehensively reflect the attitude measurement accuracy of star sensors in real-time. In this paper, a real-time analysis and calculation model for the attitude measurement accuracy of star sensors is proposed. Firstly, the basic attitude measurement model of the star sensor is established through the pinhole imaging model. Moreover, a moving frame of star sensor attitude measurement is established to avoid the defects of attitude representation by the Euler angle in the star sensor accuracy analysis. Then, combined with the error transfer of implicit overdetermined equations proposed in this paper, the error transfers of starspot extraction random error, star catalog random error, and intrinsic parameter system error are provided. Finally, simulation and field experiments are conducted to verify the accuracy of the proposed error analysis theory. The experimental results show that the attitude measurement accuracy of star sensors can be accurately estimated by using single-frame data of guide stars.

Research Review on Sensorless Measurement Technology of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor (PMSM) has the advantages of high torque/inertia ratio, high power factor, fast dynamic response speed and high reliability, and has been widely used in various high-precision AC drive systems. Incremental encoders are usually used to achieve high precision position feedback information for permanent magnet synchronous motors. The use of sensors leads to cost increase, volume increase and reliability reduction. Therefore, the sensorless measurement technology of permanent magnet synchronous motor is more and more concerned and applied by industry and research fields. In this paper, the related literature of sensorless measurement technology of permanent magnet synchronous motor is investigated, and the sensorless measurement technology is comprehensively reviewed. This paper introduces in detail the basic principle of various sensorless measuring techniques, the accuracy of position measurement and the application in the type of permanent magnet synchronous motor. In this paper, the concept of speed pole logarithm ratio is proposed to divide the speed region, and the initial rotor position, low speed and medium speed non-inductive measurement methods are described and compared. Finally, the non-inductive measurement accuracy of permanent magnet synchronous motor is summarized.

Real-time high-precision baseline measurement of satellite formation flying based on GNSS

With the establishment of the Chinese space station, a series of space science missions will be conducted in its vicinity. One of the extended tasks for the in-orbit service of space station is the formation flying of small satellites centered around the space station. Satellite formations can perform simultaneous three-dimensional observations of the space station, generating three-dimensional images and monitoring and assessing the status of critical components of the space station. The real-time and accurate relative position measurement is one of the key issues in formation flying. It is a fundamental prerequisite for maintaining and reconfiguring formation configurations, collision avoidance and safety assurance. GNSS-based relative positioning is a low-cost and high-precision measurement method, which is not constrained by light, weather, or relative attitude of satellites. This study introduces a novel approach to determine the relative position of satellites based on single-epoch Global Navigation Satellite System (GNSS) carrier phase difference measurements. Unlike traditional methods, the proposed technique eliminates the need for precise ephemeris and clock bias files and does not require historical observation data. The algorithm avoids the complexity associated with full cycle ambiguity jumps, facilitating real-time, high-precision calculations of relative position baseline vectors. Special attention is given to the influence of Geostationary Earth Orbit (GEO) satellites in the BeiDou Navigation Satellite System (BDS), and measures are taken to mitigate their impact on measurement accuracy by adjusting their observation weights. Our newly developed GNSS-based real-time measurement module, designed for high-quality GNSS signal reception and data communication, was tested on terrestrial and simulated low-orbit platforms. Remarkably, over baselines ranging from 10 m to 9.3 km, while traditional pseudorange differential measurements showed errors up to 1.5571 m, our proposed method consistently held errors under 5 cm and ensured computational speeds within 0.1 s per epoch. High-dynamic zero-baseline tests further validated its potential, with errors less than 1 cm. The innovations encapsulated in this work, resonating with the evolving trends of miniaturized and scalable satellites, present a cost-efficient and real-time solution for inter-satellite relative position measurement. This promises a new horizon in satellite formation technology, with future endeavors focusing on on-orbit experiments.

Present‐Day 3D Crustal Deformation of the Northeastern Tibetan Plateau From Space Geodesy

AbstractHigh‐resolution present‐day earth surface deformation maps from satellites provide important data constraints, which help us better understand tectonic processes and analyze seismic hazards. Here, we use Sentinel‐1 Radar images (2014–2020) and accurate positioning measurements (2009–2019) to get a high‐resolution three‐dimensional earth surface velocity map for the northeastern Tibetan Plateau, and we invert the slip rate and coupling ratio of major regional faults. We find ∼4 mm/yr uplift along an arc from the Qilianshan to Lajishan, relative to the neighboring low‐elevation area to the east, which indicates ongoing rapid orogeny. We find transient deformation along the Laohushan and 1920 M8.5 Haiyuan rupture segments of the Haiyuan fault, whereas the western Haiyuan, southern Liupanshan, central Lajishan and central‐western West Qinling faults are essentially locked above 15–20 km, suggesting a potentially high seismic hazard.

Spacecraft Attitude Measurement and Control Using VSMSCSG and Fractional-Order Zeroing Neural Network Adaptive Steering Law

In order to improve the accuracy and convergence speed of the steering law under the conditions of high dynamics, high bandwidth, and a small deflection angle, and in an effort to improve attitude measurement and control accuracy of the spacecraft, a spacecraft attitude measurement and control method based on variable speed magnetically suspended control sensitive gyroscopes (VSMSCSGs) and the fractional-order zeroing neural network (FO-ZNN) steering law is proposed. First, a VSMSCSG configuration is designed to realize attitude measurement and control integration in which the VSMSCSGs are employed as both actuators and attitude-rate sensors. Second, a novel adaptive steering law using FO-ZNN is designed. The matrix pseudoinverses are replaced by FO-ZNN outputs, which solves the problem of accuracy degradation in the traditional pseudoinverse steering laws due to the complexity of matrix pseudoinverse operations under high dynamics conditions. In addition, the convergence and robustness of the FO-ZNN are proven. The results show that the proposed FO-ZNN converges faster than the traditional zeroing neural network under external disturbances. Finally, a new weighting function containing rotor deflection angles is added to the steering law to ensure that the saturation of the rotor deflection angles can be avoided. Semi-physical simulation results demonstrate the correctness and superiority of the proposed method.

Measurement accuracy of the acetabular cup position using an inertial portable hip navigation system with patients in the lateral decubitus position

Accurate cup placement is critical to ensure satisfactory outcomes after total hip arthroplasty. Portable hip navigation systems are novel intraoperative guidance tools that achieve accurate cup placement in the supine position; however, accuracy in the lateral decubitus position is under debate. A new inertial portable navigation system has recently become available. The present study investigated the accuracy of measurements of the cup position in 54 patients in the lateral decubitus position using this system and compared it with that by a goniometer. After cup placement, cup abduction and anteversion were measured using the system and by the goniometer, and were then compared with postoperatively measured angles. Absolute measurement errors with the system were 2.8° ± 2.6° for cup abduction and 3.9° ± 2.9° for anteversion. The system achieved 98 and 96% measurement accuracies within 10° for cup abduction and anteversion, respectively. The system was more accurate than the goniometer for cup anteversion (p < 0.001), but not for abduction (p = 0.537). The system uses a new registration method of the pelvic reference plane and corrects intraoperative pelvic motion errors, which may affect measurement accuracy. In the present study, reliable and reproducible intraoperative measurements of the cup position were obtained using the inertial portable navigation system.

СИНТЕЗ АЛГОРИТМА ОЦЕНКИ ПАРАМЕТРОВ МНОГОПОЗИЦИОННОЙ СИСТЕМЫ НАБЛЮДЕНИЯ И ИССЛЕДОВАНИЕ ЭФФЕКТА РАСХОДИМОСТИ ПРОЦЕССА ФИЛЬТРАЦИИ

The accuracy of aircraft position measurements directly affects flight safety and is one of the most important tactical characteristics. The introduction of new advanced surveillance tools, such as multi-position surveillance systems (MLAT), can significantly increase the level of flight safety, as well as improve the efficiency of airspace use. The authors consider the task of improving the quality of MLAT functioning and increasing the accuracy of estimating the aircraft coordinates. The accuracy of position-fixing is determined by the error in measuring the time of signal arrival under the influence of noise and interference. Random disturbances must be taken into account to ensure high-quality MLAT operation. This is achieved by applying the methods of Kalman filtration theory. Therefore, to solve the problem of estimating the MLAT state variables, it is proposed to use a Kalman filter (KF). The effectiveness of using the Kalman filter depends on the adequacy of mathematical models and real processes. Model inaccuracies associated with the functioning of navigation systems lead to KF divergence. The paper presents the results of theoretical studies and simulating the MLAT functioning processes based on the implementation of the KF algorithm.

Accurate measurement of end position of inclined pipe with optimal projection plane of space

Accurate measurement of end position of inclined pipe with optimal projection plane of space

Method for Determining Attitude Measurement Accuracy of Photoelectric Theodolites for Positioning Unmanned Aerial Vehicles Based on RTK

Method for Determining Attitude Measurement Accuracy of Photoelectric Theodolites for Positioning Unmanned Aerial Vehicles Based on RTK

The miniSLR: a low-budget, high-performance satellite laser ranging ground station

Satellite Laser Ranging (SLR) is an established technique providing very accurate position measurements of satellites in Earth orbit. However, despite decades of development, it remains a complex and expensive technology, which impedes its further growth to new applications and users. The miniSLR implements a complete SLR system within a small, transportable enclosure. Through this design, costs of ownership can be reduced significantly, and the process of establishing a new SLR site is greatly simplified. A number of novel technical solutions have been implemented to achieve a good laser ranging performance despite the small size and simplified design. Data from the initial six months of test operation have been used to generate a first estimation of the system performance. The data include measurements to many of the important SLR satellites, such as Lageos, Etalon and most of the geodetic and Earth observation missions in LEO. It is shown that the miniSLR achieves sub-centimetre accuracy, comparable with conventional SLR systems. The miniSLR is an engineering station in the International Laser Ranging Service and supplies data to the community. Continuous efforts are undertaken to further improve the system operation and stability.

An Optical Attitude Measurement Method for Terminal Sensitive Projectile in Vertical Wind Tunnel Test

An optical attitude (scanning angle and spin rate) measurement method for terminal sensitive projectile in vertical wind tunnel test is proposed. The principles of measuring scanning angle and spin rate simultaneously depend only on one fixed camera are presented in detail. The measurement processes, which mainly includes preparation, image acquisition, segmentation of projectile, contour extraction, and estimation of attitude, are described accordingly, and the key techniques involved in each step are expanded exactly. Moreover, the measurement errors are analyzed thoroughly. The advantages of the novel method is analyzed as follow: first, the mathematical model for calculating scanning angle of a steady-state terminal sensitive projectile is derived for the first time in literature, which makes it possible to measure scanning angle from images recorded by only a fixed camera; second, the algorithms of estimating scanning angle and spin rate depend only on the line-segments of the perspective cylinders in images are designed, which significantly improve the attitude measurement accuracy. Experiment was also conducted in laboratory to verify the novel method.

An improvement to the infinite integration method Based on quadrant detector

In this study, we propose a new method to improve the position measurement accuracy of the traditional infinite integral method (IIM) based on a quadrant detector (QD). First, the error source of the IIM is analysed in depth. Then, the influence of the detector size and gap width was considered to obtain a modified integration area. Thus, a new analytical expression was obtained. We performed several sets of simulations to test the validity of our proposed method, and the root-mean-square errors under different radii were all less than 5×10-5mm. The experimental results show that when compared to IIM and the calibrated infinite integral method (CIIM), our novel method reduces error by 98.1% and 85.3%, respectively. One of the advantages of this technique is its simplicity; it requires fewer parameters and does not require pre-calibration compared with the fitting method. Therefore, this technique has the potential to be employed in space laser communication systems, optical tweezers, and precision measurements.

Position measurement technology of boom-type roadheader based on binocular vision

Positioning of underground mining equipment in coal mines is a primary challenge in the intelligent development of tunnel excavation. Accurate and reliable position measurement plays a crucial role in improving excavation efficiency. However, the stability and accuracy of traditional measurement methods are difficult to guarantee due to factors such as vibration, magnetic interference, and the absence of GPS signals in coal mine environments. To address the problem of unstable measurement of the boom-type roadheader‘s position, this paper proposes a binocular vision-based measurement technique that utilizes four light spots as characteristic points. By processing the target images captured by the binocular camera and combining the minimum bounding rectangle and ellipse fitting of the spot regions, the method successfully obtains the four light spot characteristics. Subsequently, precise matching and stereo distance measurement of the target in the left and right images enable the determination of the boom-type roadheader’s posi-tion information. A positioning platform based on binocular vision is built and experimentally evaluated. The results demonstrate that this method can achieve accurate spot extraction and stable measurement of the machine’s position, even in complex backgrounds such as mixed lighting and low illumination. The planar measurement errors within a distance range of 50 m are all within ±25 mm, which basically meets the required construction precision for tunnel excavation.

Comparative Analysis of the Effect of Cutting Piezoelectric Ceramics on Optically Oriented Compensation Capability

In a photoelectric tracking system, a deformable mirror can be used to adjust the transmission path of a light beam to achieve accurate measurement and tracking of the target position. The single-piezoelectric-sheet deformable mirror is a commonly used wavefront correction device with outstanding advantages, such as its simple structure, low cost, and easy preparation. However, it usually has a large cross-linking value and a weak ability to correct higher-order wavefront aberrations. To solve this problem, a novel single-piezoelectric-sheet deformable mirror driving structure is proposed in this paper, in which the coupling between the driving units is weakened by laser cutting the piezoelectric ceramics along the electrode gaps to reduce the cross-linking value of the deformable mirror. In order to verify the effectiveness of this driving structure, this paper takes the 85-unit single-piezoelectric-sheet deformable mirror as an example and simulates the influence function for different cutting depth conditions. The simulation results show that the cross-linking value between neighboring drive units decreases significantly as the piezoelectric-ceramic-laser cutting depth of the drive electrode gap increases. When the piezoelectric ceramic was laser cut to a depth of half of the overall thickness, the cross-linking value decreased by 6.8%.