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23 pages, 8408 KiB

Open AccessArticle

An Improved Adaptive Compensation H∞ Filtering Method for the SINS’ Transfer Alignment Under a Complex Dynamic Environment

by Weiwei Lyu, Xianghong Cheng and Jinling Wang

Sensors 2019, 19(2), 401; https://doi.org/10.3390/s19020401 - 19 Jan 2019

Cited by 7 | Viewed by 3227

Abstract

Transfer alignment on a moving base under a complex dynamic environment is one of the toughest challenges in a strapdown inertial navigation system (SINS). With the aim of improving rapidity and accuracy, velocity plus attitude matching is applied in the transfer alignment model. [...] Read more.

Transfer alignment on a moving base under a complex dynamic environment is one of the toughest challenges in a strapdown inertial navigation system (SINS). With the aim of improving rapidity and accuracy, velocity plus attitude matching is applied in the transfer alignment model. Meanwhile, the error compensation model is established to calibrate and compensate the errors of inertial sensors online. To suppress the filtering divergence during the process of transfer alignment, this paper proposes an improved adaptive compensation H∞ filtering method. The cause of filtering divergence has been analyzed carefully and the corresponding adjustment and optimization have been made in the proposed adaptive compensation H∞ filter. In order to balance accuracy and robustness of the transfer alignment system, the robustness factor of the adaptive compensation H∞ filter can be dynamically adjusted according to the complex external environment. The aerial transfer alignment experiments illustrate that the adaptive compensation H∞ filter can effectively improve the transfer alignment accuracy and the pure inertial navigation accuracy under a complex dynamic environment, which verifies the advantage of the proposed method. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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19 pages, 2466 KiB

Open AccessArticle

A Novel Monitoring Navigation Method for Cold Atom Interference Gyroscope

by Lin Zhang, Wei Gao, Qian Li, Runbing Li, Zhanwei Yao and Sibin Lu

Sensors 2019, 19(2), 222; https://doi.org/10.3390/s19020222 - 9 Jan 2019

Cited by 18 | Viewed by 5456

Abstract

The implementation principle of a typical three-pulse cold atom interference gyroscope is introduced in this paper. Based on its configuration and current research status, the problems of cold atom interference gyro are pointed out. The data-rate is insufficient, and it is difficult to [...] Read more.

The implementation principle of a typical three-pulse cold atom interference gyroscope is introduced in this paper. Based on its configuration and current research status, the problems of cold atom interference gyro are pointed out. The data-rate is insufficient, and it is difficult to achieve high dynamic measurement. Then, based on these two limitations, a novel design of the monitoring navigation system of the cold atom interference gyroscope (CAIG) and an intermediate-grade inertial measurement unit (IMU) was proposed to obtain the long-term position result without GPS signals, such as the Inertial Navigation System (INS) in underwater vehicles. While the CAIG was used as the external gyro, the bias of IMU and the misalignment angle between the CAIG-frame and the IMU-frame are obtained through filtering technique. The simulation test and field test demonstrated the improvements of the long-term positioning accuracy of the INS. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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12 pages, 5549 KiB

Open AccessArticle

The Elastic Contact and Stability Analysis of an Inertial Micro-Switch with a Spring Stationary Electrode

by Wenguo Chen, Huiying Wang, Dejian Kong and Shulei Sun

Sensors 2018, 18(12), 4238; https://doi.org/10.3390/s18124238 - 3 Dec 2018

Cited by 1 | Viewed by 3014

Abstract

A mechanical trigger inertial micro-switch with spring stationary electrode is proposed and fabricated by surface micromachining. The elastic contact process and stability performance are evaluated through experimental tests performed using a drop hammer. The test results show that the contact time is about [...] Read more.

A mechanical trigger inertial micro-switch with spring stationary electrode is proposed and fabricated by surface micromachining. The elastic contact process and stability performance are evaluated through experimental tests performed using a drop hammer. The test results show that the contact time is about 110 μs and 100 μs when the threshold acceleration is 480 g and the overload acceleration is 602 g, respectively. The vibration process of the electrodes is explained through an established physical mode. The elastic contact process is analyzed and discussed by Finite Element Analysis (FEA) simulations, which indicated that the contact time is about 65 μs when the threshold acceleration is 600 g. At the same time, this result also proved that the contact time could be extended effectively by the designed spring stationary electrode. The overload acceleration (800 g) has been applied to the Finite-Element model in ANSYS, the contact process indicated that the proof mass contacted with stationary electrode three times, and there was no bounce phenomenon during contact process, which fully proved that the stable contact process can be realized at high acceleration owing to the designed elastic stationary electrode. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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18 pages, 2840 KiB

Open AccessArticle

Economical High–Low Temperature and Heading Rotation Test Method for the Evaluation and Optimization of the Temperature Control System for High-Precision Platform Inertial Navigation Systems

by Qiang Yang, Rong Zhang and Haixia Li

Sensors 2018, 18(11), 3967; https://doi.org/10.3390/s18113967 - 15 Nov 2018

Cited by 7 | Viewed by 4109

Abstract

Inertial navigation systems (INSs) use the temperature control system to ensure the stability of the temperature of the inertial sensors for improving the navigation accuracy of the INSs. That is, the temperature control accuracy affects the performance of the INSs. Thus, the performance [...] Read more.

Inertial navigation systems (INSs) use the temperature control system to ensure the stability of the temperature of the inertial sensors for improving the navigation accuracy of the INSs. That is, the temperature control accuracy affects the performance of the INSs. Thus, the performance of temperature control systems must be evaluated before their application. However, nearly all high-precision INSs are large and heavy and require long-term testing under many different experimental conditions. As a result, conducting an outdoor navigation experiment, which involves high–low temperature and heading rotation tests, is time consuming, laborious, and costly for researchers. To address this issue, an economical high–low temperature and heading rotation test method for high-precision platform INSs is proposed, and an evaluation system based on this method is developed to evaluate the performance of the temperature control systems for high-precision platform INSs indoors. The evaluation system uses an acrylic chamber, exhaust fans, temperature sensors, and an air conditioner to simulate the environment temperature change. The outer gimbals of the platform INSs are utilized to simulate the heading rotation. The temperature control system of a high-precision platform INS is evaluated using the proposed evaluation method. The temperature difference of the gyros is obtained in the high–low temperature test, and the temperature fluctuation of the temperature control system is observed in the rotation test. These tests verify the effectiveness of the proposed evaluation method. Then, the corresponding optimization method for the temperature control system of this high-precision platform INS is put forward on the basis of the test results of the evaluation system. Experimental results show that the maximum temperature differences of the two gyros between high- and low-temperature tests are decreased from 1.51 °C to 0.50 °C, and the maximum temperature fluctuation value of the temperature control system is decreased from 0.81 °C to 0.27 °C after the proposed evaluation and optimization processes. Therefore, the proposed methods are cost effective and useful for evaluating and optimization of the temperature control system for INSs. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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16 pages, 3089 KiB

Open AccessArticle

A Three-Stage Accelerometer Self-Calibration Technique for Space-Stable Inertial Navigation Systems

by Qiuping Wu, Ruonan Wu, Fengtian Han and Rong Zhang

Sensors 2018, 18(9), 2888; https://doi.org/10.3390/s18092888 - 31 Aug 2018

Cited by 14 | Viewed by 4006

Abstract

As a specific force sensor, the tri-axis accelerometer is one of the core instruments in an inertial navigation system (INS). During navigation, its measurement error directly induces constant or alternating navigation errors of the same order of magnitude. Moreover, it also affects the [...] Read more.

As a specific force sensor, the tri-axis accelerometer is one of the core instruments in an inertial navigation system (INS). During navigation, its measurement error directly induces constant or alternating navigation errors of the same order of magnitude. Moreover, it also affects the estimation accuracy of gyro drift coefficients during the initial alignment and calibration, which will indirectly result in navigation errors accumulating over time. Calibration can effectively improve measurement accuracy of the accelerometer. Device-level calibration can identify all of the parameters in the error model, and the system-level calibration can accurately estimate part of these parameters. Combining the advantages of both the methods and making full use of the precise angulation of the space-stabilized platform, this paper proposes a three-stage accelerometer self-calibration technique that can be implemented directly in the space-stable INS. The device-level calibration is divided into two steps considering the large amount of parameters. The first step is coarse calibration, which identifies parameters except for the nonlinear terms, and the second step is fine calibration, which not only identifies the nonlinear parameters, but also improves the accuracy of the parameters identified in the first step. The follow-on system-level calibration is carried out on part of the parameters using specific force error and attitude error to further improve the calibration accuracy. Simulation result shows that by using the proposed three-stage calibration technique in the space-stable INS, the estimation accuracy of accelerometer error can reach

{1 \times 10}^{- 6} g

order of magnitude. Experiment results show that after the three-stage calibration, the accuracy of latitude, longitude, and attitude angles has increased by over 45% and the accuracy of velocity has increased by over 22% during navigation. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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14 pages, 6338 KiB

Open AccessArticle

Oscillation Suppression in the Sense Mode of a High-Q MEMS Gyroscope Using a Simplified Closed-Loop Control Method

by Qiang Shen, Xinpeng Wang, Yixuan Wu and Jianbing Xie

Sensors 2018, 18(8), 2443; https://doi.org/10.3390/s18082443 - 27 Jul 2018

Cited by 6 | Viewed by 3917

Abstract

The oscillation of the sense mode of the micro-machined Coriolis vibratory gyroscope (MCVG) with high quality factor (Q) is analyzed in this study and the corresponding force feedback control scheme is presented to suppress this oscillation. The controller consists of integrator [...] Read more.

The oscillation of the sense mode of the micro-machined Coriolis vibratory gyroscope (MCVG) with high quality factor (Q) is analyzed in this study and the corresponding force feedback control scheme is presented to suppress this oscillation. The controller consists of integrator and some filters, instead of the common but complicated demodulation and remodulation modules. Compared with using no oscillation suppression scheme, the proposed simplified oscillation suppression control scheme can achieve an improvement of the sense mode of the MCVG. The inband spectrum ripple of the angular rate output are improved from 51.4 dB to 4.23 × 10⁻⁴ dB. Correspondingly, these two performance parameters are improved by 370.4 and 186.2 times, which are higher than two orders of magnitude, respectively. Bias stability is improved from 9.72 deg/h to 2.5 deg/h. Test results prove that the proposed control scheme is effective in suppressing the oscillation. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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14 pages, 2243 KiB

Open AccessArticle

A Parameter Self-Calibration Method for GNSS/INS Deeply Coupled Navigation Systems in Highly Dynamic Environments

by Zang Chen, Jizhou Lai, Jianye Liu, Rongbing Li and Guotian Ji

Sensors 2018, 18(7), 2341; https://doi.org/10.3390/s18072341 - 18 Jul 2018

Cited by 3 | Viewed by 3394

Abstract

The GNSS/INS (Global Navigation Satellite System/Inertial Navigation System) navigation system has been widely discussed in recent years. Because of the unique INS-aided loop structure, the deeply coupled system performs very well in highly dynamic environments. In practice, vehicle maneuvering has a big influence [...] Read more.

The GNSS/INS (Global Navigation Satellite System/Inertial Navigation System) navigation system has been widely discussed in recent years. Because of the unique INS-aided loop structure, the deeply coupled system performs very well in highly dynamic environments. In practice, vehicle maneuvering has a big influence on the performance of IMUs (Inertial Measurement Unit), and determining whether the selected IMUs and receiver parameters satisfy the loop dynamic requirement is still a critical problem for deeply coupled systems. Aiming at this, a new parameter self-calibration method based on the norm principle is proposed which explains the relationship between IMU precision and the velocity error of the system; the method will also provide a detailed solution to calculate the loop steady-state tracking error, so it will eventually make a judgment about the stability of the tracking loop under present system parameter settings. Lastly, a full digital simulation platform is set up, and the results of simulations show good agreement with the proposed method. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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17 pages, 4560 KiB

Open AccessArticle

Multiple Fusion Based on the CCD and MEMS Accelerometer for the Low-Cost Multi-Loop Optoelectronic System Control

by Yong Luo, Yao Mao, Wei Ren, Yongmei Huang, Chao Deng and Xi Zhou

Sensors 2018, 18(7), 2153; https://doi.org/10.3390/s18072153 - 4 Jul 2018

Cited by 12 | Viewed by 3670

Abstract

In the charge-coupled device (CCD) and micro-electro-mechanical system (MEMS) accelerometer based low-cost multi-loop optoelectronic control system (OCS), due to accelerometers’ drift and noise in low frequency, the disturbance suppression (DS) is insufficient. Previously, based on the acceleration and position dual-loop control (ADLC), researchers [...] Read more.

In the charge-coupled device (CCD) and micro-electro-mechanical system (MEMS) accelerometer based low-cost multi-loop optoelectronic control system (OCS), due to accelerometers’ drift and noise in low frequency, the disturbance suppression (DS) is insufficient. Previously, based on the acceleration and position dual-loop control (ADLC), researchers combined a disturbance observer (DOB) with a virtual velocity loop to make some medium-frequency DS exchange for low-frequency performance. However, it is not optimal because the classic DOB based on accelerometers’ inaccurate signals cannot observe accurate disturbance in low frequency and the velocity based on a CCD and accelerometer time-domain fusion carried the CCD’s delay, resulting in the drop of medium-frequency DS. In this paper, considering the CCD’s advantage in low frequency and the accelerometer’s strength in high frequency, we propose to fuse their signals twice with a modified complementary filter method to respectively acquire an acceleration and velocity. The new acceleration with no drift and less noise but lower bandwidth creates a new acceleration model and is only used in fusion DOB (FDOB), while the velocity with little delay is to build an additional velocity loop. Compared with the traditional DOB enhanced by the time-domain fusion velocity loop, experiments verify that the proposed multiple fusion would apparently enhance the system’s DS, especially in low and medium frequency. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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19 pages, 3421 KiB

Open AccessArticle

An Optimization-Based Initial Alignment and Calibration Algorithm of Land-Vehicle SINS In-Motion

by Kang Gao, Shunqing Ren, Xijun Chen and Zhenhuan Wang

Sensors 2018, 18(7), 2081; https://doi.org/10.3390/s18072081 - 28 Jun 2018

Cited by 9 | Viewed by 3666

Abstract

For a running freely land-vehicle strapdown inertial navigation system (SINS), the problems of self-calibration and attitude alignment need to be solved simultaneously. This paper proposes a complete alignment algorithm for the land vehicle navigation using Inertial Measurement Units (IMUs) and an odometer. A [...] Read more.

For a running freely land-vehicle strapdown inertial navigation system (SINS), the problems of self-calibration and attitude alignment need to be solved simultaneously. This paper proposes a complete alignment algorithm for the land vehicle navigation using Inertial Measurement Units (IMUs) and an odometer. A self-calibration algorithm is proposed based on the global observability analysis to calibrate the odometer scale factor and IMU misalignment angle, and the initial alignment and calibration method based on optimal algorithm is established to estimate the attitude and other system parameters. This new algorithm has the capability of self-initialization and calibration without any prior attitude and sensor noise information. Computer simulation results show that the performance of the proposed algorithm is superior to the extended Kalman filter (EKF) method during the oscillating attitude motions, and the vehicle test validates its advantages. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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18 pages, 4314 KiB

Open AccessArticle

Error Analysis of Magnetohydrodynamic Angular Rate Sensor Combing with Coriolis Effect at Low Frequency

by Yue Ji, Mengjie Xu, Xingfei Li, Tengfei Wu, Weixiao Tuo, Jun Wu and Jiuzhi Dong

Sensors 2018, 18(6), 1921; https://doi.org/10.3390/s18061921 - 13 Jun 2018

Cited by 14 | Viewed by 4418

Abstract

The magnetohydrodynamic (MHD) angular rate sensor (ARS) with low noise level in ultra-wide bandwidth is developed in lasing and imaging applications, especially the line-of-sight (LOS) system. A modified MHD ARS combined with the Coriolis effect was studied in this paper to expand the [...] Read more.

The magnetohydrodynamic (MHD) angular rate sensor (ARS) with low noise level in ultra-wide bandwidth is developed in lasing and imaging applications, especially the line-of-sight (LOS) system. A modified MHD ARS combined with the Coriolis effect was studied in this paper to expand the sensor’s bandwidth at low frequency (<1 Hz), which is essential for precision LOS pointing and wide-bandwidth LOS jitter suppression. The model and the simulation method were constructed and a comprehensive solving method based on the magnetic and electric interaction methods was proposed. The numerical results on the Coriolis effect and the frequency response of the modified MHD ARS were detailed. In addition, according to the experimental results of the designed sensor consistent with the simulation results, an error analysis of model errors was discussed. Our study provides an error analysis method of MHD ARS combined with the Coriolis effect and offers a framework for future studies to minimize the error. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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17 pages, 7785 KiB

Open AccessArticle

Design of an Inertial-Sensor-Based Data Glove for Hand Function Evaluation

by Bor-Shing Lin, I-Jung Lee, Shu-Yu Yang, Yi-Chiang Lo, Junghsi Lee and Jean-Lon Chen

Sensors 2018, 18(5), 1545; https://doi.org/10.3390/s18051545 - 13 May 2018

Cited by 77 | Viewed by 7964

Abstract

Capturing hand motions for hand function evaluations is essential in the medical field. Various data gloves have been developed for rehabilitation and manual dexterity assessments. This study proposed a modular data glove with 9-axis inertial measurement units (IMUs) to obtain static and dynamic [...] Read more.

Capturing hand motions for hand function evaluations is essential in the medical field. Various data gloves have been developed for rehabilitation and manual dexterity assessments. This study proposed a modular data glove with 9-axis inertial measurement units (IMUs) to obtain static and dynamic parameters during hand function evaluation. A sensor fusion algorithm is used to calculate the range of motion of joints. The data glove is designed to have low cost, easy wearability, and high reliability. Owing to the modular design, the IMU board is independent and extensible and can be used with various microcontrollers to realize more medical applications. This design greatly enhances the stability and maintainability of the glove. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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18 pages, 4107 KiB

Open AccessArticle

Hybrid Transverse Polar Navigation for High-Precision and Long-Term INSs

by Ruonan Wu, Qiuping Wu, Fengtian Han, Rong Zhang, Peida Hu and Haixia Li

Sensors 2018, 18(5), 1538; https://doi.org/10.3390/s18051538 - 12 May 2018

Cited by 10 | Viewed by 4036

Abstract

Transverse navigation has been proposed to help inertial navigation systems (INSs) fill the gap of polar navigation ability. However, as the transverse system does not have the ability of navigate globally, a complicated switch between the transverse and the traditional algorithms is necessary [...] Read more.

Transverse navigation has been proposed to help inertial navigation systems (INSs) fill the gap of polar navigation ability. However, as the transverse system does not have the ability of navigate globally, a complicated switch between the transverse and the traditional algorithms is necessary when the system moves across the polar circles. To maintain the inner continuity and consistency of the core algorithm, a hybrid transverse polar navigation is proposed in this research based on a combination of Earth-fixed-frame mechanization and transverse-frame outputs. Furthermore, a thorough analysis of kinematic error characteristics, proper damping technology and corresponding long-term contributions of main error sources is conducted for the high-precision INSs. According to the analytical expressions of the long-term navigation errors in polar areas, the 24-h period symmetrical oscillation with a slowly divergent amplitude dominates the transverse horizontal position errors, and the first-order drift dominates the transverse azimuth error, which results from the

g^{0}

gyro drift coefficients that occur in corresponding directions. Simulations are conducted to validate the theoretical analysis and the deduced analytical expressions. The results show that the proposed hybrid transverse navigation can ensure the same accuracy and oscillation characteristics in polar areas as the traditional algorithm in low and mid latitude regions. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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19 pages, 4139 KiB

Open AccessArticle

An Innovative Strategy for Accurate Thermal Compensation of Gyro Bias in Inertial Units by Exploiting a Novel Augmented Kalman Filter

by Rita Fontanella, Domenico Accardo, Rosario Schiano Lo Moriello, Leopoldo Angrisani and Domenico De Simone

Sensors 2018, 18(5), 1457; https://doi.org/10.3390/s18051457 - 7 May 2018

Cited by 32 | Viewed by 5725

Abstract

This paper presents an innovative model for integrating thermal compensation of gyro bias error into an augmented state Kalman filter. The developed model is applied in the Zero Velocity Update filter for inertial units manufactured by exploiting Micro Electro-Mechanical System (MEMS) gyros. It [...] Read more.

This paper presents an innovative model for integrating thermal compensation of gyro bias error into an augmented state Kalman filter. The developed model is applied in the Zero Velocity Update filter for inertial units manufactured by exploiting Micro Electro-Mechanical System (MEMS) gyros. It is used to remove residual bias at startup. It is a more effective alternative to traditional approach that is realized by cascading bias thermal correction by calibration and traditional Kalman filtering for bias tracking. This function is very useful when adopted gyros are manufactured using MEMS technology. These systems have significant limitations in terms of sensitivity to environmental conditions. They are characterized by a strong correlation of the systematic error with temperature variations. The traditional process is divided into two separated algorithms, i.e., calibration and filtering, and this aspect reduces system accuracy, reliability, and maintainability. This paper proposes an innovative Zero Velocity Update filter that just requires raw uncalibrated gyro data as input. It unifies in a single algorithm the two steps from the traditional approach. Therefore, it saves time and economic resources, simplifying the management of thermal correction process. In the paper, traditional and innovative Zero Velocity Update filters are described in detail, as well as the experimental data set used to test both methods. The performance of the two filters is compared both in nominal conditions and in the typical case of a residual initial alignment bias. In this last condition, the innovative solution shows significant improvements with respect to the traditional approach. This is the typical case of an aircraft or a car in parking conditions under solar input. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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17 pages, 2556 KiB

Open AccessArticle

An Improved Fast Self-Calibration Method for Hybrid Inertial Navigation System under Stationary Condition

by Bingqi Liu, Shihui Wei, Guohua Su, Jiping Wang and Jiazhen Lu

Sensors 2018, 18(5), 1303; https://doi.org/10.3390/s18051303 - 24 Apr 2018

Cited by 23 | Viewed by 5145

Abstract

The navigation accuracy of the inertial navigation system (INS) can be greatly improved when the inertial measurement unit (IMU) is effectively calibrated and compensated, such as gyro drifts and accelerometer biases. To reduce the requirement for turntable precision in the classical calibration method, [...] Read more.

The navigation accuracy of the inertial navigation system (INS) can be greatly improved when the inertial measurement unit (IMU) is effectively calibrated and compensated, such as gyro drifts and accelerometer biases. To reduce the requirement for turntable precision in the classical calibration method, a continuous dynamic self-calibration method based on a three-axis rotating frame for the hybrid inertial navigation system is presented. First, by selecting a suitable IMU frame, the error models of accelerometers and gyros are established. Then, by taking the navigation errors during rolling as the observations, the overall twenty-one error parameters of hybrid inertial navigation system (HINS) are identified based on the calculation of the intermediate parameter. The actual experiment verifies that the method can identify all error parameters of HINS and this method has equivalent accuracy to the classical calibration on a high-precision turntable. In addition, this method is rapid, simple and feasible. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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20 pages, 2136 KiB

Open AccessArticle

Enhanced Pedestrian Navigation Based on Course Angle Error Estimation Using Cascaded Kalman Filters

by Jin Woo Song and Chan Gook Park

Sensors 2018, 18(4), 1281; https://doi.org/10.3390/s18041281 - 21 Apr 2018

Cited by 26 | Viewed by 6641

Abstract

An enhanced pedestrian dead reckoning (PDR) based navigation algorithm, which uses two cascaded Kalman filters (TCKF) for the estimation of course angle and navigation errors, is proposed. The proposed algorithm uses a foot-mounted inertial measurement unit (IMU), waist-mounted magnetic sensors, and a zero [...] Read more.

An enhanced pedestrian dead reckoning (PDR) based navigation algorithm, which uses two cascaded Kalman filters (TCKF) for the estimation of course angle and navigation errors, is proposed. The proposed algorithm uses a foot-mounted inertial measurement unit (IMU), waist-mounted magnetic sensors, and a zero velocity update (ZUPT) based inertial navigation technique with TCKF. The first stage filter estimates the course angle error of a human, which is closely related to the heading error of the IMU. In order to obtain the course measurements, the filter uses magnetic sensors and a position-trace based course angle. For preventing magnetic disturbance from contaminating the estimation, the magnetic sensors are attached to the waistband. Because the course angle error is mainly due to the heading error of the IMU, and the characteristic error of the heading angle is highly dependent on that of the course angle, the estimated course angle error is used as a measurement for estimating the heading error in the second stage filter. At the second stage, an inertial navigation system-extended Kalman filter-ZUPT (INS-EKF-ZUPT) method is adopted. As the heading error is estimated directly by using course-angle error measurements, the estimation accuracy for the heading and yaw gyro bias can be enhanced, compared with the ZUPT-only case, which eventually enhances the position accuracy more efficiently. The performance enhancements are verified via experiments, and the way-point position error for the proposed method is compared with those for the ZUPT-only case and with other cases that use ZUPT and various types of magnetic heading measurements. The results show that the position errors are reduced by a maximum of 90% compared with the conventional ZUPT based PDR algorithms. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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19 pages, 27629 KiB

Open AccessArticle

Robust Sliding Mode Control of PMSM Based on Rapid Nonlinear Tracking Differentiator and Disturbance Observer

by Zhanmin Zhou, Bao Zhang and Dapeng Mao

Sensors 2018, 18(4), 1031; https://doi.org/10.3390/s18041031 - 29 Mar 2018

Cited by 42 | Viewed by 6215

Abstract

Torque ripples caused by cogging torque, flux harmonics, and current measurement error seriously restrict the application of a permanent magnet synchronous motor (PMSM), which has been paid more and more attention for the use in inertial stabilized platforms. Sliding mode control (SMC), in [...] Read more.

Torque ripples caused by cogging torque, flux harmonics, and current measurement error seriously restrict the application of a permanent magnet synchronous motor (PMSM), which has been paid more and more attention for the use in inertial stabilized platforms. Sliding mode control (SMC), in parallel with the classical proportional integral (PI) controller, has a high advantage to suppress the torque ripples as its invariance to disturbances. However, since the high switching gain tends to cause chattering and it requires derivative of signals which is not readily obtainable without an acceleration signal sensor. Therefore, this paper proposes a robust SMC scheme based on a rapid nonlinear tracking differentiator (NTD) and a disturbance observer (DOB) to further improve the performance of the SMC. The NTD is employed to providing the derivative of the signal, and the DOB is utilized to estimate the system lumped disturbances, including parameter variations and external disturbances. On the one hand, DOB can compensate the robust SMC speed controller, it can reduce the chattering of SMC on the other hand. Experiments were carried out on an ARM and DSP-based platform. The obtained experimental results demonstrate that the robust SMC scheme has an improved performance with inertia stability and it exhibits a satisfactory anti-disturbance performance compared to the traditional methods. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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10 pages, 1010 KiB

Open AccessArticle

Height Error Correction for Shoe-Mounted Inertial Sensors Exploiting Foot Dynamics

by Estefania Munoz Diaz, Susanna Kaiser and Dina Bousdar Ahmed

Sensors 2018, 18(3), 888; https://doi.org/10.3390/s18030888 - 16 Mar 2018

Cited by 16 | Viewed by 4327

Abstract

Shoe-mounted inertial sensors are widespread deployed in satellite-denied scenarios because of the possibility to re-calibrate stepwise the estimated position. These re-calibrations, known as zero-velocity corrections, prevent an accumulated positioning error growth over time caused by the noise of current medium- and low-cost sensors. [...] Read more.

Shoe-mounted inertial sensors are widespread deployed in satellite-denied scenarios because of the possibility to re-calibrate stepwise the estimated position. These re-calibrations, known as zero-velocity corrections, prevent an accumulated positioning error growth over time caused by the noise of current medium- and low-cost sensors. However, the error accumulated over time in the height estimation is still an issue under study. The objective of this article is to propose a height correction that is based on the dynamics of the foot. The presented algorithm analyzes the movement of the foot, which is different when walking on horizontal surfaces and stairs. The identification of horizontal surfaces and stairs is detailed in this article. For the assessment of the performance of the proposed height correction, a dataset of approximately 5 h recorded with 10 volunteers walking in a five-story building is employed. The error is evaluated using pre-defined ground truth points. We compare the height error estimated with and without applying the proposed correction and show that the height correction improves the vertical positioning accuracy up to 85. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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26 pages, 4250 KiB

Open AccessArticle

A Model of Gravity Vector Measurement Noise for Estimating Accelerometer Bias in Gravity Disturbance Compensation

by Junbo Tie, Juliang Cao, Lubing Chang, Shaokun Cai, Meiping Wu and Junxiang Lian

Sensors 2018, 18(3), 883; https://doi.org/10.3390/s18030883 - 16 Mar 2018

Cited by 15 | Viewed by 6515

Abstract

Compensation of gravity disturbance can improve the precision of inertial navigation, but the effect of compensation will decrease due to the accelerometer bias, and estimation of the accelerometer bias is a crucial issue in gravity disturbance compensation. This paper first investigates the effect [...] Read more.

Compensation of gravity disturbance can improve the precision of inertial navigation, but the effect of compensation will decrease due to the accelerometer bias, and estimation of the accelerometer bias is a crucial issue in gravity disturbance compensation. This paper first investigates the effect of accelerometer bias on gravity disturbance compensation, and the situation in which the accelerometer bias should be estimated is established. The accelerometer bias is estimated from the gravity vector measurement, and a model of measurement noise in gravity vector measurement is built. Based on this model, accelerometer bias is separated from the gravity vector measurement error by the method of least squares. Horizontal gravity disturbances are calculated through EGM2008 spherical harmonic model to build the simulation scene, and the simulation results indicate that precise estimations of the accelerometer bias can be obtained with the proposed method. Full article

(This article belongs to the Special Issue Inertial Sensors and Systems 2018)

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