Orthogonal Accelerometers Research Articles

Multiple and Gyro-Free Inertial Datasets

An inertial navigation system (INS) utilizes three orthogonal accelerometers and gyroscopes to determine platform position, velocity, and orientation. There are countless applications for INS, including robotics, autonomous platforms, and the internet of things. Recent research explores the integration of data-driven methods with INS, highlighting significant innovations, improving accuracy and efficiency. Despite the growing interest in this field and the availability of INS datasets, no datasets are available for gyro-free INS (GFINS) and multiple inertial measurement unit (MIMU) architectures. To fill this gap and to stimulate further research in this field, we designed and recorded GFINS and MIMU datasets using 54 inertial sensors grouped in nine inertial measurement units. These sensors can be used to define and evaluate different types of MIMU and GFINS architectures. The inertial sensors were arranged in three different sensor configurations and mounted on a mobile robot, a passenger car and a turntable. In total, the dataset contains 45 hours of inertial data and corresponding ground truth trajectories. The data is freely accessible through our figshare repository.

A ubiquitous architecture for wheelchair fall anomaly detection using low-cost embedded sensors and isolation forest algorithm

Falls represent one of the major health risk issues world-wide. In this paper, a wheelchair fall anomaly detection framework based on the hybrid Isolation Forest (IF) and threshold based method (TBM) is proposed. The sensor data was obtained from tri-axial orthogonal accelerometer and gyroscope MPU-6050 sensor. In order to handle the uncertainties due to the sensor noise factor, a method based on Zero Angular Rate Update (ZART) and Complementary Filter (CF) was utilized. The concept of sensor fusion was applied to create multi-dimensional training data from the best features selected using the ReliefF algorithm. The IF detector was trained on the best eight-dimensional features selected from 48 features for the detection of the fall events in contrast to 38 features defined in our previous publication in Sheikh and Jilani. Further, the design of a ubiquitous architecture incorporating the proposed fall detection scheme was proposed. The g-mean score accuracy was achieved up-to ∼97.1% with the proposed IF +threshold hybrid strategy. While using only the IF method, an F1-score of 96.2%, an AUC-ROC score of 95.3% and a g-mean score of 92.9 % was obtained.

The use of deep learning algorithms to predict mechanical strain from linear acceleration and angular rates of motion recorded from a horse hoof during exercise

Mobility solutions offered by living creatures have inspired engineers to capture their locomotion patterns and then develop novel animal-like robots that use legs for locomotion. Exploring relationships amongst mechanical responses and kinematic parameters is essential for both inventing these robots and enhancing computational techniques. Establishment of accurate physical models to quantify mechanical responses of biological systems is challenging because the corresponding variables are multidimensional, dynamic and highly nonlinear. This encourages the advent of data-driven models in mechanical sciences. This paper delves into the use of feedforward and time-series (dynamic) artificial neural networks (ANN) to analyse experimental data recorded from a racing horse exercised up to 60 km/h to then relate hoof mechanical strain to kinematic parameters recorded experimentally. An inertial measurement unit that was comprised of a sensor and data acquisition system package was designed and mounted on the horse's hoof to measure linear accelerations and angular rates of motion. In addition, an instrumented Aluminium horseshoe that was designed and manufactured and contained: (1) inertial sensors including three orthogonal accelerometers and three orthogonal rate gyroscopes; and, (2) a strain gauge located at the middle of the shoe. The horse was warmed up in a steady gallop at around 35 km/h for 1 km then turned around and galloped at increasing speed to 68 km/h back to the finishing line. Nine kinematic parameters, measured during horse exercise, formed the ANNs input variables: hoof linear accelerations along three orthogonal directions (axe,ay,az), hoof angular rates of motion along three orthogonal directions (Gx, Gy, Gz), shoe linear accelerations along three orthogonal directions (axs, ays, azs), and time. Feedforward and time-series ANNs trained using 1,000,000 experimental instances offered excellent reliability for the prediction of mechanical strain from kinematic measurements, i.e. R ≥ 0.97.

A motion capture algorithm based on inertia-Kinect sensors for lower body elements and step length estimation

Motion capture is a process that movements of living organisms like human or objects are captured and the results are processed for the desired applications. These applications are in rehabilitation, sports, film industry and etc. There are many techniques and instruments for motion capture that optical camera systems are the most accurate ones. But these cameras are high cost and limited to labs. Some sensors like Inertial Measurement Units (IMU) and recently, Kinect cameras have been considered by many researchers because these are low cost and easy to use. But problems like bias, accumulated error and occlusion make them look for improvements. Fusion algorithms are one of the best methods that help to use from each sensor’s strengths. The purpose of this work is design and implementation of an efficient algorithm for estimation of lower limbs joints 3D positions and step length. Orientation quaternions are considered as estimation states. An algorithm was developed with gradient descent and unscented Kalman filter approach based on IMUs and Kinect’s measurements. The IMUs’ data consist of three mutually orthogonal gyroscopes, three mutually orthogonal accelerometers, and a three-axis magnetometer. In this algorithm bias and magnetic distortions have been compensated in parallel structure. The resulted errors have been reported with respect to VICON optical camera system. The results obtained from an experimental test, show up to 60 percent improvement on Kinect in joints 3D positions estimation and the algorithm improves step length estimation error of Kinect from 7.8 cm to 0.03 cm.

Study on Misalignment Angle Compensation during Scale Factor Matching for Two Pairs of Accelerometers in a Gravity Gradient Instrument.

A method for automatic compensation of misalignment angles during matching the scale factors of two pairs of the accelerometers in developing the rotating accelerometer gravity gradient instrument (GGI) is proposed and demonstrated in this paper. The purpose of automatic scale factor matching of the four accelerometers in GGI is to suppress the common mode acceleration of the moving-based platforms. However, taking the full model equation of the accelerometer into consideration, the other two orthogonal axes which is the pendulous axis and the output axis, will also sense the common mode acceleration and reduce the suppression performance. The coefficients from the two axes to the output are δO and δP respectively, called the misalignment angles. The angle δO, coupling with the acceleration along the pendulous axis perpendicular to the rotational plane, will not be modulated by the rotation and gives little contribution to the scale factors matching. On the other hand, because of coupling with the acceleration along the centripetal direction in the rotating plane, the angle δP would produce a component with 90 degrees phase delay relative to the scale factor component. Hence, the δP component coincides exactly with the sensitive direction of the orthogonal accelerometers. To improve the common mode acceleration rejection, the misalignment angle δP is compensated by injecting a trimming current, which is proportional to the output of an orthogonal accelerometer, into the torque coil of the accelerometer during the scale factor matching. The experimental results show that the common linear acceleration suppression achieved three orders after the scale factors balance and five orders after the misalignment angles compensation, which is almost down to the noise level of the used accelerometers of 1~2 × 10−7 g/√Hz (1 g ≈ 9.8 m/s2).

A Low-Cost Calibration Strategy for Measurement-While-Drilling System

The measurement-while-drilling (MWD) system is mainly used to draw borehole trajectory in a coal mine. However, its measurement error directly demonstrates a deviation between the drawing locus and the actual path. Thus, it is imperative to effectively compensate the error in advance. In this study, the traditional-integrated error model is adopted and a low-cost calibration strategy, namely an incomplete calibration strategy, is proposed. In this strategy, the ellipsoid-fitting method is quoted to determine the combined bias and orthogonalize the coordinate frame of the triaxial accelerometer, and a new plane-fitting method is exploited to align the orthogonal accelerometer coordinate frame with the body coordinate frame of the MWD system; meanwhile, the theoretical basis is also stated with the simulation verification of MATLAB. Besides this, the scalar product constant method is finally employed to acquire the error model of the triaxial magnetometer on the condition of the previously calibrated accelerometer coordinate system. In the end, the newly designed calibration strategy was experimentally tested with the MWD prototype developed by ourselves. The results reveal that the strategy can not only be implemented without the help of other expensive auxiliary equipment but also has good performance in attitude reconstruction

Fault diagnostics in rotary machines through spectral vibration analysis using low-cost MEMS devices

The present work shows a low-cost instrument, based on a microelectromechanical systems (MEMS) accelerometer which costs less than US$ 1.20/unit and is designed to analyze unbalance in rotating machines. The acceleration signals were acquired using two perpendicular axes on a free wheel shaft, which were used to analyze the shaft vibration in the frequency domain by its Fast Fourier Transform (FFT). These signals from orthogonal accelerometers were also used to calculate the shaft unbalance. The instrument prototype was mounted on the shaft of an electrical bicycle motor wheel, rotating in a range of 60 to 270 rpm. Composing the characterization apparatus, some weights were introduced at the ends of rim spokes to simulate a mechanical wheel unbalance. The experimental results showed that both vibration and unbalance can be measured successfully and that this instrument is a suitable low-cost solution to measure vibration and unbalance in rotating machines.

Análisis del patrón locomotor mediante acelerometría triaxial en caballos sedados con acepromacina

Objective: quantify by accelerometry the locomotor pattern in horses sedated with acepromazineMethodology: seven horses were used and administered 2 treatments: saline solution and acepromazine (0.04 mg / kg). Is used an orthogonal accelerometer measuring acceleration along three axes. Accelerometric records were obtained after treatment, repeated every five minutes during the first 20 minutes and then every 10 minutes for 3 hours. Parameters sedation was also measured.Results: acepromazine decreased some of the variables. Speed, stride frequency and stride length were significantly reduced post-treatment. For the coordination parameters no significant differences were observed. Energy variables suffered only minor reductions while the ground-lip distance values decreased.Clinical significance: acepromazine produce significant changes in the pattern but does not affect the variables of coordination in horses and may be the tranquilizer of choice for evaluating lameness.

Inertial Pocket Navigation System: Unaided 3D Positioning.

Inertial navigation systems use dead-reckoning to estimate the pedestrian's position. There are two types of pedestrian dead-reckoning, the strapdown algorithm and the step-and-heading approach. Unlike the strapdown algorithm, which consists of the double integration of the three orthogonal accelerometer readings, the step-and-heading approach lacks the vertical displacement estimation. We propose the first step-and-heading approach based on unaided inertial data solving 3D positioning. We present a step detector for steps up and down and a novel vertical displacement estimator. Our navigation system uses the sensor introduced in the front pocket of the trousers, a likely location of a smartphone. The proposed algorithms are based on the opening angle of the leg or pitch angle. We analyzed our step detector and compared it with the state-of-the-art, as well as our already proposed step length estimator. Lastly, we assessed our vertical displacement estimator in a real-world scenario. We found that our algorithms outperform the literature step and heading algorithms and solve 3D positioning using unaided inertial data. Additionally, we found that with the pitch angle, five activities are distinguishable: standing, sitting, walking, walking up stairs and walking down stairs. This information complements the pedestrian location and is of interest for applications, such as elderly care.

The use of low doses of acepromazine as an aid for lameness diagnosis in horses: An accelerometric evaluation.

The aim of the present study was to quantify by accelerometry the trotting pattern of adult horses sedated with two different doses of acepromazine, in order to assess the use of this drug in equine lameness evaluations. Seven mature horses were used and three treatments were administered to each horse: saline solution, acepromazine (0.01 mg/kg), and acepromazine (0.02 mg/kg). The portable gait analyzer used consisted of three orthogonal accelerometers that measure accelerations along the dorsoventral, longitudinal, and lateral axes. Baseline values were obtained and after treatment, accelerometric recordings were repeated every five minutes during the first 20 minutes after the injection and then every 10 minutes thereafter for two hours. Ground-to-lip distance was also measured. Administration of acepromazine decreased some of the variables investigated and differences between doses were observed. Speed, stride frequency, and stride length were significantly reduced following treatments. For coordination parameters, no significant differences among values were observed. Energetic variables suffered only weak reductions whereas ground-to-lip distance values were significantly decreased up to 120 minutes after treatment. Acepromazine produces significant alterations in the gait pattern with differences between doses, but it does not affect coordination variables in normal unexcited horses, and at a dose of 0.01 mg/kg may be the tranquilizer of choice for evaluating lameness in this setting.

Side Impact PMHS Thoracic Response With Large-Volume Air Bag

Objective: The objective of this study is to assess the response of postmortem human subjects (PMHS) to a large-volume side air bag in a fully instrumented and well-controlled side impact test condition. Methods: Three adult male PMHS were subjected to right-side pure lateral impacts. Each stationary seated subject was struck at 4.3 ± 0.1 m/s by a rigid wall installed on a 1700-kg rail-mounted sled. Each subject was held stationary by a system of tethers until immediately prior to being impacted by the moving wall. A large side air bag was mounted to the wall and deployed so that it was fully inflated at the time it contacted the subject's right side. The load wall consisted of an adjustable matrix of 15 individual plates, each supported by a 5-axis load cell that recorded the interaction between the subject and impacting wall. Two-dimensional (external) torso deformation was provided by a chest band that encircled the torso at the level of the sixth rib laterally. Triaxial acceleration was measured at the head, spine, and sacrum via 3 orthogonal accelerometers mounted to the same bone-mounted hardware that held the marker clusters used for kinematic analysis. Results: Peak pelvic load normal to the wall averaged 6.8 kN, which was over 5 times that recorded for the shoulder (1.3 kN) and the thorax (1.2 kN). Lateral chest deflection ranged from 9 to 21 mm. Two of the 3 subjects sustained 2 and 9 fractures, respectively. Conclusions: Two of the 3 PMHS sustained rib fractures despite low levels of thorax deflection. We attribute this finding to individual variability in subject injury tolerance. Other response parameters exhibited lower levels of variability and characterize PMHS response to a potentially beneficial side impact countermeasure. Supplemental materials are available for this article. Go to the publisher's online edition of Traffic Injury Prevention to view the supplemental file.

가속도계와 자이로스코프를 이용한 평면의 경사각 추정

Measurement or estimation of tilt angle is necessary for balancing robot such as Segway which is considered as a next generation transportation vehicle. However, it requires high-cost accurate sensors to hold balancing during stationary and moving situations. In this paper, a tilt angle estimation of a plane rotating in a vertical plane using low-cost sensors. Estimation using a set of 2-axis orthogonal accelerometers along with an inaccurate rate gyro has been considered. Feasibility and performance of the proposed technique has been verified through some experimental results.

Vision and IMU Data Fusion: Closed-Form Solutions for Attitude, Speed, Absolute Scale, and Bias Determination

This paper investigates the problem of vision and inertial data fusion. A sensor assembling that is constituted by one monocular camera, three orthogonal accelerometers, and three orthogonal gyroscopes is considered. The first paper contribution is the analytical derivation of all the observable modes, i.e., all the physical quantities that can be determined by only using the information in the sensor data that are acquired during a short time interval. Specifically, the observable modes are the speed and attitude (roll and pitch angles), the absolute scale, and the biases that affect the inertial measurements. This holds even in the case when the camera only observes a single point feature. The analytical derivation of the aforementioned observable modes is based on a nonstandard observability analysis, which fully accounts for the system nonlinearities. The second contribution is the analytical derivation of closed-form solutions, which analytically express all the aforementioned observable modes in terms of the visual and inertial measurements that are collected during a very short time interval. This allows the introduction of a very simple and powerful new method that is able to simultaneously estimate all the observable modes with no need for any initialization or a priori knowledge. Both the observability analysis and the derivation of the closed-form solutions are carried out in several different contexts, including the case of biased and unbiased inertial measurements, the case of a single and multiple features, and in the presence and absence of gravity. In addition, in all these contexts, the minimum number of camera images that are necessary for the observability is derived. The performance of the proposed approach is evaluated via extensive Monte Carlo simulations and real experiments.

A comparison between timed and IMU captured Nordic ski glide tests

An inertial measurement unit (IMU) with six degrees of freedom (three orthogonal accelerometers and three orthogonal rate gyroscopes) was used to calculate the acceleration loss as a function of position down the test slope. A traditional timed glide test was performed at the same time. The results from both test methods were compared. To increase the accuracy of the sensor system, two speed sensors were installed at known positions. The gradient of the track was measured and utilized by the sensor system to correct measurement errors. A mathematical model, developed by Apertus AS (Asker, Norway) was used to estimate the snow friction coefficient based on the acceleration loss. The results from the IMU sensor provided more information, including peak acceleration, maximum speed, time required to reach maximum speed, and speed loss, which can easily be seen. The use of IMU sensors in gliding tests may prove useful to differ between skis (Δμ ∼ 0.01). We conclude that in order to detect the minute differences distinguishing the best skis (Δμ ∼ 0.001), sensors with an even higher degree of sensitivity than those tested in this experiment should be used.

Use of a reduced IMU to aid a GPS receiver with adaptive tracking loops for land vehicle navigation

A reduced inertial measurement unit (IMU) consisting of only one vertical gyro and two horizontal accelerometers or three orthogonal accelerometers can be used in land vehicle navigation systems to reduce volume and cost. In this paper, a reduced IMU is integrated with a Global Positioning System (GPS) receiver whose phase lock loops (PLLs) are aided with the Doppler shift from the integrated system. This approach is called tight integration with loop aiding (TLA). With Doppler aiding, the noise bandwidth of the PLL loop filters can be narrowed more than in the GPS-only case, which results in improved noise suppression within the receiver. In this paper, first the formulae to calculate the PLL noise bandwidth in a TLA GPS/reduced IMU are derived and used to design an adaptive PLL loop filter. Using a series of vehicle tests, results show that the noise bandwidth calculation formulae are valid and the adaptive loop filter can improve the performance of the TLA GPS/reduced IMU in both navigation performance and PLL tracking ability.

Orientierung endoskopischer Bilder: Rektifizierung durch Schwerkraft / Orientation of endoscopic images: rectification by gravity

A known problem in endoscopic surgery (especially with flexible video endoscopes) is the absence of a stable horizon in endoscopic images displayed on a monitor. With our "ENDOrientation" approach, image rectification, even in non-rigid endoscopic surgery (particularly NOTES), can be realized with a tiny MEMS tri-axial inertial sensor placed on the tip of an endoscope. This sensor measures the impact of gravity on each of the three orthogonal accelerometer axes in real time. After an initial calibration and temporal filtering of these three data steams, the rotation angle of an endoscope can be estimated directly. The achievable sampling rate of the inertial sensor is above the usual endoscopic video frame rate of 25 Hz; the rotation accuracy is approximately one degree. The image rectification can be performed in real time by digitally rotating the endoscopic video signal. Improvements and benefits have been evaluated in animal studies: coordination and movement of different instruments was rated to be much more intuitive with a stable horizon on endoscopic images. The recorded time stamps and position tracks clearly support this observation.

P2.134 Differential response of bradykinesia and hypokinesia to levodopa in Parkinson's disease

Eighty-five PD patients (Table 1) performed UPDRS-directed finger tapping, hand grasping, and pronation/supination tasks in the OFF (12-15 hours after dopaminergic drug withdrawal) and ON states while wearing wireless six-degree-of-freedom motion sensors (KinetiSenseTM, CleveMed) on the index finger and thumb (Figure 1). Each motion sensor contains three orthogonal accelerometers for measuring linear acceleration and three orthogonal gyroscopes for measuring angular velocity. A Modified Bradykinesia Rating Scale (MBRS) was used to assess separately speed and amplitude during the tasks on a 0 – 4 scale (Table 2). Quantitative variables representing speed (root-mean-square [RMS] angular velocity) and amplitude (RMS excursion angle) were extracted from kinematic data, correlated with clinical MBRS scores, and used to classify patients as hypokinetic, bradykinetic, both, or neither. Although slowness (bradykinesia) and decreased amplitude (hypokinesia) of movements may be associated with differential impairment and disability in Parkinson’s disease (PD), clinicians are asked to rate rapid alternating movements into a combined 0 – 4 severity scale through the Unified Parkinson’s Disease Rating Scale motor subscale (UPDRS-III). Clinical raters consider multiple aspects of movement including speed, amplitude, hesitations, fatiguing, and arrests in movement. Previous research has shown that individual clinicians weigh individual components of bradykinesia differently, thus creating a considerable degree of variability across clinicians. The objective of this study is to evaluate the motor function and response to dopaminergic drugs in patients with PD with various impairments in speed and amplitude of movement. Speed and amplitude are evaluated separately to determine if bradykinesia and hypokinesia should deserve separate clinical assessment.

Gait Analysis Using a Shoe-Integrated Wireless Sensor System

We describe a wireless wearable system that was developed to provide quantitative gait analysis outside the confines of the traditional motion laboratory. The sensor suite includes three orthogonal accelerometers, three orthogonal gyroscopes, four force sensors, two bidirectional bend sensors, two dynamic pressure sensors, as well as electric field height sensors. The "GaitShoe" was built to be worn in any shoe, without interfering with gait and was designed to collect data unobtrusively, in any environment, and over long periods. The calibrated sensor outputs were analyzed and validated with results obtained simultaneously from the Massachusetts General Hospital, Biomotion Laboratory. The GaitShoe proved highly capable of detecting heel-strike and toe-off, as well as estimating foot orientation and position, inter alia.

A Bit-Based Data-Acquisition System for Hard-Rock PDC Bits

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 105017, "Development and Utilization of a Bit-Based Data- Acquisition System in Hard-Rock PDC Applications," by Paul Pastusek, SPE, Eric Sullivan, and Tommy Harris, SPE, Hughes Christensen Co., prepared for the 2007 SPE/IADC Drilling Conference, Amsterdam, 20–22 February. The full-length paper describes the development and use of a bit-based module designed to monitor accelerometer and magnetometer sensors and to record selected data. The authors also describe the effort to infer dynamic dysfunctions from the data in the fast-growing hard-rock polycrystalline-diamond-compact (PDC) -bit application and to mitigate them by modifications to drilling parameters and bit designs. Introduction Drill bits are developed iteratively for specific applications to meet performance objectives such as aggressiveness, durability, stability, and steerability. The transition from one iteration to the next occurs when dull bits are examined, run data are analyzed, and the inferences are implemented as revisions to the bit design and/or the operating parameters. Experience has shown that the efficiency of the process depends strongly upon the appropriateness and significance of the data collected. If, for example, a dominant cutter-failure mechanism is characterized incorrectly as abrasive wear and is, in fact, impact wear, then both the proposed solution and the development time will be affected significantly. One method for improving the significance of the data collected is to implement a special-purpose data-acquisition system within the bit. Such a device has at least three significant advantages over available subassembly-based data-acquisition systems:Its bit-based sensors will detect bit-based events more accurately,it can be deployed economically over many bits, andit is relatively transparent to the user. Objective The objective of the project was to develop an inexpensive battery-powered programmable data-acquisition system sized to fit within a bit and sufficiently robust to function under typical downhole-service conditions to monitor and record data for post-well analysis. The device is intended to support bit design, drilling-parameter development, and validation of laboratory simulation software and tests. A device has been designed, manufactured, and tested that is an integrated battery-powered dynamic-behavior sensor and data-acquisition module. The module typically is implanted within the pin portion of a downhole tool, (e.g., within the shank portion of a bit). Modules are being run currently in bits in selected applications. Form. The sensor/data-acquisition module is sized and constructed so that it can be implanted within an annular recess machined between the inside diameter (ID) and outside diameter of the end of a rock-bit shank. The electronics are implemented with rigid/flex circuit boards to minimize the number of failure-prone wire interconnects. The board, a temperature-measuring device, three orthogonal (x, y, z) accelerometers, three orthogonal (x, y, z) magnetometers, and the batteries are attached to a rigid "backbone" to form the integrated (standalone) module. An end cap with O-ring seals and backup rings forms the ID and bottom of the sealed-module cavity when installed and protects the device from moisture and hydrostatic pressures.

IMPROVING WELLBORE SURVEYING ACCURACY OF HORIZONTAL WELLS BY UTILIZING A DUAL-AXIS OPTICAL GYRO SYSTEM

Measurement-while-drilling (MWD) surveying systems utilizing fiber optic gyroscopes (FOGs) have been suggested as a replacement for the present magnetic surveying techniques in order to avoid the imperfections associated with magnetic monitoring devices. A gyroscopic surveying methodology incorporating a single FOG with its sensitive axis along the central axis of the drill pipe and three mutually orthogonal single-axis accelerometers was suggested to survey horizontal wells. This method suffered from some limitations and an increase in the surveying errors at certain orientations. This article aims at overcoming these limitations by suggesting a dual FOG system using an additional FOG with its sensitive axis normal to the central axis of the drill pipe. The proposed dual FOG system has been tested using a custom designed experimental setup that can simulate several orientations similar to those experienced by the bottom hole assembly downhole. The results showed significant improvement in the accuracy of the surveying parameters with no specific limitations. This study suggests that gyroscopic surveying utilizing a dual FOG system can be a reliable solution for MWD surveying of horizontal wells.