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Inertial reference unit

About: Inertial reference unit is a research topic. Over the lifetime, 1306 publications have been published within this topic receiving 22068 citations. The topic is also known as: IRU.


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01 Jan 2003
TL;DR: In this article, a technique for modeling and calibrating a camera with integrated low-cost iner- tial sensors, three gyros and three accelerometers for full 3D sensing is presented.
Abstract: This article presents a technique for modeling and calibrating a camera with integrated low-cost iner- tial sensors, three gyros and three accelerometers for full 3D sensing. Inertial sensors attached to a camera can provide valuable data about camera pose and movement. In biological vision systems, inertial cues provided by the vestibular system, are fused with vision at an early processing stage. Vision systems in autonomous vehi- cles can also benefit by taking inertial cues into account. Camera calibration has been extensively studied, and standard techniques established. Inertial navigation systems, relying on high-end sensors, also have established techniques. Nevertheless, in order to use off-the-shelf inertial sensors attached to a camera, appropriate modeling and calibration techniques are required. For inertial sensor alignment, a pendulum instrumented with an encoded shaft is used to estimate the bias and scale factor of inertial measurements. For camera calibration, a standard and reliable camera calibration technique is used, based on images of a planar grid. Having both the camera and the inertial sensors calibrated and observing the vertical direction at different poses, the rigid rotation between the two frames of reference is estimated, using a mathematical model based on unit quaternions. The technique for this alignment and consequent results with simulated and real data are presented at the end of this article.

38 citations

Journal ArticleDOI
TL;DR: In this paper, an easy-to-install joint-angle estimation method is proposed, which can work independently from the primary encoder-based sensor, for the creation of a fault-detection system.
Abstract: This paper focuses on the use of low-cost inertial sensors in industrial manipulators. In particular, an easy-to-install joint-angle estimation method is proposed. This scheme can work independently from the primary encoder-based sensor, for the creation of a fault-detection system. It can also be the primary joint-angle sensor in low-cost robotic manipulators. A robot with six degrees of freedom has been used, with three inertial measurement units set on its arms; one for each pair of joints. Three cascaded extended Kalman filters have been used to estimate the joint angles by the fusion of the outputs of triaxial gyroscopes and accelerometers. The results of three experimental tests are reported in order to show the performance and limitations of this approach, in comparison with the simple gyroscope measurements integration.

38 citations

Journal ArticleDOI
TL;DR: Optical angle encoder calibration methods using accelerometers are proposed, on the basis of navigation error and accuracy requirement analyses for a single-axis RINS, and the test results show that the accuracy of calibration methods proposed is higher than 4 arcsec (1σ).
Abstract: By rotating a strapdown inertial navigation system (INS) over one or more axes, a number of error sources originating from the employed sensors cancel out during the integration process. Rotary angle accuracy has an effect on the performance of rotational INS (RINS). The application of existing calibration methods based on gyroscope measurements is restricted by the structure of the inertial measurement unit (IMU) and scale factor stability of the gyroscope. The multireadhead method has problems in miniaturization and cost. Hence, optical angle encoder calibration methods using accelerometers are proposed, on the basis of navigation error and accuracy requirement analyses for a single-axis RINS. The test results show that the accuracy of calibration methods proposed is higher than 4 arcsec (1σ).

38 citations

Journal ArticleDOI
TL;DR: A versatile, wearable device based on a 9-degrees-of-freedom inertial measurement unit conceived for providing objective measurements of trunk or limb movements for the assessment of motor and balance control abilities is presented.
Abstract: Measuring human movement has many useful applications ranging from fall risk assessment, quantifying sports exercise, studying people habits, and monitoring the elderly. Here, we present a versatile, wearable device based on a 9-degrees-of-freedom inertial measurement unit conceived for providing objective measurements of trunk or limb movements for the assessment of motor and balance control abilities. The proposed device measures linear accelerations, angular velocities, and heading and can be configured to either wirelessly transmit the raw or preprocessed data to a computer for online use, e.g., visualization or further processing, or to store the acquired data locally for long-term monitoring during free movement. Furthermore, the device can work in either single sensor or multiple sensors configuration, to simultaneously record several body parts for monitoring full body kinematics. Here, we compare body sway and trunk kinematic data computed based on our sensor with those based on the data from a force platform and a marker-based motion tracker, respectively, during the evaluation of both static and dynamic exercises drawn from clinical balance scales. Results from these experiments on two populations of healthy subjects are encouraging and suggest that the proposed device can effectively be used for measuring limb movements and to assess balance control abilities.

37 citations

Patent
11 Sep 1991
TL;DR: In this paper, a three-axis gyro measurement package comprising a computer and the possibility of feeding or automaticly reading-in of reference data characterizing the reference directions is presented.
Abstract: The calibration of time-depending measurement uncertainties of gyros and inertial systems by the differences of angular and/or velocity and/or positional measurements which are carried out and repetitiously executed with a view to undetermined reference directions and/or fixed locations varying with time. The differentiation allows to forego precise reference data. Measurement uncertainties can be corrected through calibration subsequently to the measurement process. For the measurement of spatial angles a three-axis gyro measurement package comprising a computer and the possibility of feeding or automaticly reading-in of reference data characterizing the reference directions. The reference data can be a number, a marker of the measurement point or in the case of positional measurements a terrestrial aiming point. When measuring angular characteristics, i.e. the interdependence of angles and external forces or moments, the latter are considered as references. For the measurement of contours the distance has to be fed in or read in, or computed by accelerometers within an integrated inertial system, respectively. By such a system and through the application of the invention the measurement accuracy of movements and gravity anomalies can be increased while refraining from external references otherwise necessary under the present state of the art.

37 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202314
202221
20211
20202
20193
20189