Azimuth determination using a low noise ring laser gyro inertial measurement unit

1981 ◽  
Author(s):  
J. MATTHEWS ◽  
M. GNESES ◽  
D. PASIK
Keyword(s):  
Ring Laser ◽  
Inertial Measurement Unit ◽  
Low Noise ◽  
Measurement Unit ◽  
Inertial Measurement ◽  
Laser Gyro

Isotropic Design Method of Suspension System of Dithered RLG Strapdown Inertial Measurement Unit

2014 ◽  
Vol 1044-1045 ◽  
pp. 788-797 ◽  
Author(s):  
Geng Li ◽  
Guo Wei ◽  
Yuan Pin Xie ◽  
Peng Fei Zhang ◽  
Xu Dong Yu ◽  
...  
Keyword(s):  
Ring Laser ◽  
Inertial Measurement Unit ◽  
Dynamic Range ◽  
Inertial Sensor ◽  
Design Method ◽  
Suspension System ◽  
Measurement Unit ◽  
Mass Center ◽  
Inertial Measurement ◽  
Laser Gyro

The dithered ring laser gyro (DRLG) strapdown inertial navigation system (SINS) is widely used in many applications, including military and commercial systems for the advantages such as high accuracy, wide dynamic range and bandwidth, outstanding scale factor stability over temperature, compactness and lower cost. However, the dither motion introduced to eliminate the lock-in error which is the inherent phenomena in the ring laser gyro also brought the adverse disturbance to the inertial measurement unit (IMU). Meanwhile, the installation environment of the SINS may also bring undesirable vibration and shock. For these reasons, a feasible and reliable suspension system is required to provide decoupling of the translational and rotational vibrations of the inertial sensor assembly (ISA) and attenuating the outside vibration and shock. Based on this, the isotropic design method of suspension system of DRLG strapdown IMU is proposed in this paper. The method consists four principles: 1) the input axes of sensors should be placed symmetrically along the ISA symmetric axes which are also the principle inertial axes; 2) the mass center of ISA is also the center of the geometric structure; 3) the elastic center of the suspension system is overlapped on the mass center by placing mounting isolators in the ISA structure corner in the isotropic manner and 4) the first mode frequency of ISA structure should be twice or more higher than the maxim mechanical dither frequency of DRLG triad. Following these principles, a design practice is implemented. The simulation and the experiment result show that the IMU using isotropic design method is proved to be feasible and reliable even in the extreme temperature ambiance.

scholarly journals Coupled Dynamic Analysis and Decoupling Optimization Method of the Laser Gyro Inertial Measurement Unit

Sensors ◽  
2019 ◽  
Vol 20 (1) ◽  
pp. 111
Author(s):  
Fang Fang ◽  
Wenhui Zeng ◽  
Zilong Li
Keyword(s):  
Frequency Response ◽  
Vibration Frequency ◽  
Inertial Measurement Unit ◽  
Design Method ◽  
Optimization Method ◽  
Measurement Unit ◽  
Coupled Vibration ◽  
Inertial Measurement ◽  
Laser Gyro ◽  
Optimal Design Method

The mechanical dithered ring laser gyro (RLG) effectively overcomes the lock-in effect and ensures the sensitive accuracy of the low angular rate for the gyro. However, in the inertial measurement unit (IMU) system, the dither excitation of three RLGs causes the coupled vibration of the IMU structure, which could seriously limit the measuring accuracy of RLGs. In this paper, the vibration frequency response characteristic of laser gyro IMU is taken as the focus point, and the method of multi-rigid body dynamics is used to establish the dynamic model of IMU suitable for vibration frequency response analysis. On the basis of the model, the multi-degree-of-freedom coupling vibration of IMU with the gyro dither excitation is clearly described. A new IMU dynamic decoupling optimization method is proposed to minimize the coupled vibration frequency response, and compared with the previous optimal design method. The prototype experimental test results show that the coupled vibration of IMU is restrained more effectively by the proposed new method than by the previous optimal design method. Finally, on the basis of this new method, the measuring accuracy of the RLGs in the IMU system is improved, which is quite useful for practical engineering application.

scholarly journals A Calibration Method for the Errors of Ring Laser Gyro in Rate-Biased Mode

Sensors ◽  
2019 ◽  
Vol 19 (21) ◽  
pp. 4754
Author(s):  
Zengjun Liu ◽  
Lei Wang ◽  
Kui Li ◽  
Jingxuan Ban ◽  
Meng Wang
Keyword(s):  
Ring Laser ◽  
Inertial Measurement Unit ◽  
Inertial Navigation System ◽  
Calibration Method ◽  
Scale Factor ◽  
Measurement Unit ◽  
Misalignment Angle ◽  
Laser Gyro ◽  
Constant Bias ◽  
The Difference

Ring laser gyro (RLG) can work in mechanically dithered mode or rate-biased mode according to the working state of the inertial navigation system (INS). It can change from one mode to the other by receiving outer instructions. To evaluate the performance of RLG in rate-biased mode, an inertial measurement unit (IMU) based on RLG is installed on a dual-axis turntable, the turntable offers a constant angular velocity to the RLGs, in that way RLG can work in the rate-biased mode. A calibration method is proposed to calibrate the scale factor error, misalignments and constant bias of RLG in rate-biased mode, experiment results show that the differences of scale factor of the three gyros in two modes are 9 ppm, 7 ppm and 3.5 ppm, the constant biases of the three RLGs in rate-biased mode are also different from that in mechanically dithered mode with the difference of 0.017°/h, 0.011°/h and 0.020°/h, the input axis misalignment angle of RLGs in different modes also changed. What is more, a calculation method of angle random walk (ARW) of RLG in rate-biased mode is also presented. Experimental results show that the ARW of the RLG in rate-biased mode is about one third of that in mechanically dithered.

scholarly journals Automatically evaluating balance using machine learning and data from a single inertial measurement unit

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Fahad Kamran ◽  
Kathryn Harrold ◽  
Jonathan Zwier ◽  
Wendy Carender ◽  
Tian Bao ◽  
...  
Keyword(s):  
Machine Learning ◽  
Inertial Measurement Unit ◽  
Physical Therapists ◽  
Physical Therapist ◽  
Model Performance ◽  
Machine Learning Techniques ◽  
Measurement Unit ◽  
Balance Performance ◽  
Inertial Measurement ◽  
Self Assessments

Abstract Background Recently, machine learning techniques have been applied to data collected from inertial measurement units to automatically assess balance, but rely on hand-engineered features. We explore the utility of machine learning to automatically extract important features from inertial measurement unit data for balance assessment. Findings Ten participants with balance concerns performed multiple balance exercises in a laboratory setting while wearing an inertial measurement unit on their lower back. Physical therapists watched video recordings of participants performing the exercises and rated balance on a 5-point scale. We trained machine learning models using different representations of the unprocessed inertial measurement unit data to estimate physical therapist ratings. On a held-out test set, we compared these learned models to one another, to participants’ self-assessments of balance, and to models trained using hand-engineered features. Utilizing the unprocessed kinematic data from the inertial measurement unit provided significant improvements over both self-assessments and models using hand-engineered features (AUROC of 0.806 vs. 0.768, 0.665). Conclusions Unprocessed data from an inertial measurement unit used as input to a machine learning model produced accurate estimates of balance performance. The ability to learn from unprocessed data presents a potentially generalizable approach for assessing balance without the need for labor-intensive feature engineering, while maintaining comparable model performance.

scholarly journals Inertial Measurement Unit Sensors in Assistive Technologies for Visually Impaired People, a Review

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4767
Author(s):  
Karla Miriam Reyes Leiva ◽  
Milagros Jaén-Vargas ◽  
Benito Codina ◽  
José Javier Serrano Olmedo
Keyword(s):  
Inertial Measurement Unit ◽  
Visually Impaired ◽  
Inertial Sensors ◽  
Assistive Technologies ◽  
Biomechanical Analysis ◽  
Measurement Unit ◽  
Inertial Measurement ◽  
Visually Impaired People ◽  
Impaired People ◽  
Application Fields

A diverse array of assistive technologies have been developed to help Visually Impaired People (VIP) face many basic daily autonomy challenges. Inertial measurement unit sensors, on the other hand, have been used for navigation, guidance, and localization but especially for full body motion tracking due to their low cost and miniaturization, which have allowed the estimation of kinematic parameters and biomechanical analysis for different field of applications. The aim of this work was to present a comprehensive approach of assistive technologies for VIP that include inertial sensors as input, producing results on the comprehension of technical characteristics of the inertial sensors, the methodologies applied, and their specific role in each developed system. The results show that there are just a few inertial sensor-based systems. However, these sensors provide essential information when combined with optical sensors and radio signals for navigation and special application fields. The discussion includes new avenues of research, missing elements, and usability analysis, since a limitation evidenced in the selected articles is the lack of user-centered designs. Finally, regarding application fields, it has been highlighted that a gap exists in the literature regarding aids for rehabilitation and biomechanical analysis of VIP. Most of the findings are focused on navigation and obstacle detection, and this should be considered for future applications.

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