Showing papers on "Inertial reference unit published in 2009"

Calibration of a Novel MEMS Inertial Reference Unit

Abstract: This paper describes a novel low-cost inertial reference unit (IRU) developed for spin-stabilized sounding rockets, as well as a method to calibrate the IRU using a one-axis rate table. The IRU contains three orthogonally mounted microelectromechanical system (MEMS) gyros and is intended for use in a low-cost system for attitude determination of sounding rockets. The high spin velocity of the rockets (4-6 r/s) causes sensor misalignments and scale factor errors to have a large effect on the gyro outputs. The performance of the IRU is considerably improved by detailed calibration, including temperature compensation. For sounding rocket applications, the total rate error is typically reduced by more than one order of magnitude. The calibration procedure uses a ramp profile calibration maneuver input at all three sensor axes and a Kalman filter to estimate the 12 error parameters.

LEO-based positioning system for indoor and stand-alone navigation

Abstract: A method for estimating a precise position of a user device from signals from a low earth orbit (LEO) satellite includes receiving at least one carrier signal at a user device, each carrier signal being transmitted a distinct LEO satellite. The user device processes the carrier signals to obtain a first carrier phase information. The user device recalls an inertial position fix derived at an inertial reference unit. The user device derives a position of the user device based on the inertial position fix and the first carrier phase information.

Fast Relative Pose Calibration for Visual and Inertial Sensors

Abstract: Accurate vision-aided inertial navigation depends on proper calibration of the relative pose of the camera and the inertial measurement unit (IMU). Calibration errors introduce bias in the overall motion estimate, degrading navigation performance - sometimes dramatically. However, existing camera-IMU calibration techniques are difficult, time-consuming and often require additional complex apparatus. In this paper, we formulate the camera-IMU relative pose calibration problem in a filtering framework, and propose a calibration algorithm which requires only a planar camera calibration target. The algorithm uses an unscented Kalman filter to estimate the pose of the IMU in a global reference frame and the 6-DoF transform between the camera and the IMU. Results from simulations and experiments with a low-cost solid-state IMU demonstrate the accuracy of the approach.

Autonomous Inertial Relative Navigation with Sight-Line-Stabilized Sensors for Spacecraft Rendezvous

Abstract: consists of the inertial position and velocity of the client satellite governed by a high-fidelity nonlinear orbital dynamics model. The error covariance matrix is formulated in terms of the estimation error in the relative position and velocity of the client satellite, consistent with the sensor measurements. Inertial attitude pointing and rate commands for tracking the client satellite are determined using the estimates of the client’s inertial relative position and velocity. To estimate the inertial attitude of the chaser satellite outside the space-integrated Global Positioning System/inertialnavigationsystem,anewthree-axissteady-stateanalyticalattitudeestimatorisdevelopedthatblends thegyro-andthestar-tracker-measuredattitudes.Thesimulationresultsofamidrangespacecraftrendezvoususing glideslope guidance validate this new six-state autonomous inertial relative navigation technique. The simulation resultsshowthattheimagingsensor’ssightlinecanbestabilizedattheclientsatelliteinmidrangeaccuratelyenough to enable the laser range finder to measure the range occasionally, but these measurements are not necessary for the midrangerendezvousphase,becausetheextendedKalman filtercanestimatetherangewiththeanglemeasurements of the imaging sensor.

Method and system for estimation of inertial sensor errors in remote inertial measurement unit

Abstract: A method and system for estimation of inertial sensor errors is provided. The method includes receiving first inertial output data from a master inertial measurement unit (IMU) mounted on a host platform, with the first inertial output data comprising a change in velocity (delta V) and a change in angle (delta theta), and receiving second inertial output data from a remote IMU mounted on the host platform at a predetermined fixed distance from the master IMU, with the second inertial output data comprising a delta V and a delta theta. The first inertial output data is compared with the second inertial output data to determine a difference between the delta V of the first inertial output data and the delta V of the second inertial output data, and to determine a difference between the delta theta of the first inertial output data and the delta theta of the second inertial output data. The determined differences are applied to estimate inertial sensor errors in the remote IMU.

Enhanced mobile robot outdoor localization using INS/GPS integration

Abstract: An unprecedented surge of developments in mobile robot outdoor navigation was witnessed after the US government removed selective availability of the global positioning system (GPS). However, in certain situations GPS becomes unreliable or unavailable due to obstructions such as buildings and trees. During GPS outages, a positioning solution with a minimum cost is preferred for small wheeled robots. A low-cost inertial measurement unit (IMU) is a good choice to provide such a solution; however, low-cost MEMS-based inertial sensors suffer from several errors that are stochastic in nature. These errors accumulate and cause a rapid deterioration in the quality of position estimate. The purpose of this paper is to describe an enhanced low-cost 3-D navigation system using a Kalman filter (KF) that integrates odometry from wheel encoders, low cost MEMS-based inertial sensors, and GPS. The proposed technique uses reduced inertial sensor system (RISS). The RISS used here includes three accelerometers and one gyroscope aligned with the vertical axis of the body frame of the robot. The benefits of eliminating the two other gyroscopes normally used are decreasing the cost further, and improving the performance by having less inertial sensors and thus less contribution of these sensors errors towards positional errors. These two eliminated gyroscopes were used to calculate pitch and roll which are now calculated using the two horizontal accelerometers. The experimental results show that, during GPS outages, this KF with velocity update derived from the forward speed from wheel encoders is a good technique for greatly reducing localization errors. Real localization data from one trajectory is presented. This data is post-processed and some simulated GPS outages are introduced to assess the effectiveness of the proposed technique.

Microelectromechnical Systems Inertial Measurement Unit Error Modelling and Error Analysis for Low-cost Strapdown Inertial Navigation System

Abstract: This paper presents error modelling and error analysis of microelectromechnical systems (MEMS) inertial measurement unit (IMU) for a low-cost strapdown inertial navigation system (INS). The INS consists of IMU and navigation processor. The IMU provides acceleration and angular rate of the vehicle in all the three axes. In this paper, errors that affect the MEMS IMU, which is of low cost and less volume, are stochastically modelled and analysed using Allan variance. Wavelet decomposition has been introduced to remove the high frequency noise that affects the sensors to obtain the original values of angular rates and accelerations with less noise. This increases the accuracy of the strapdown INS. The results show the effect of errors in the output of sensors, easy interpretation of random errors by Allan variance, the increase in the accuracy when wavelet decomposition is used for denoising inertial sensor raw data. Defence Science Journal, 2009, 59(6), pp.650-658 , DOI:http://dx.doi.org/10.14429/dsj.59.1571

Integrity monitoring of inertial reference unit

Abstract: Systems, methods, and machine-executable programming products adapted for the control of aircraft or other vehicles by receiving from at least one Inertial Reference System (IRS), including a plurality of Inertial Reference Units (IRUs), signals representing vehicle state data; receiving from at least one Augmented Direct Mode Sensor (ADMS) signals representing independently-acquired vehicle state data corresponding to at least a subset of the signals received from the IRS; performing signal selection and fault detection processes on the signals received from the at least one IRS and on the corresponding signals received from the ADMS; based at least partly on the signal and fault detection processes, determining whether at least one component of at least one of the IRS and ADMS is in a fault condition; and based on the fault condition, providing to at least one vehicle control system device one or more vehicle control command signals.

Study of inertial measurement unit sensor

Abstract: This paper contains the study about the inertial measurement unit (IMU) sensor. The study is about the types available in markets and also some research on IMU. In this paper also included the uncertainty of some IMU been used and comparison between some IMU manufacturers. Then the combination of IMU with GPS can provide more effective result for navigation, guidance and controlling system for aircraft such as UAV (unmanned aerial vehicle).

Capacitive position measurement for high-precision space inertial sensor

Abstract: Low noise position measurement is fundamental for space inertial sensors, and at present the capacitive position sensor is widely employed for space inertial sensors. The design for the possible suppression of the front-end electric noises for a capacitive sensor is presented. A prototype capacitive sensor with 2×10−6pF/Hz1/2 at frequency above 0.04 Hz is achieved and further improvements are discussed.

Robust Design of Inertial Measurement Units Based on Accelerometers

Abstract: This paper presents a robust design scheme for an inertial measurement unit (IMU) composed only of accelerometers. From acceleration data measured by a redundant set of accelerometers, the IMU proposed in this paper can estimate the linear acceleration, angular velocity, and angular acceleration of the rigid-body to which it is attached. The robustness of our method to the uncertainty of the locations of the sensors and the measurement noise is obtained through redundancy and optimal configuration of the onboard sensors. In addition, the fail-diagnostics and fail-safe issues are also addressed for reliable operation.

Technique to improve navigation performance through carouselling

Abstract: A method to improve estimation and stabilization of heading in an inertial navigation system is provided. The method includes operating an inertial measurement unit oriented in a first orientation, forward-rotating the operational inertial measurement unit by a selected-rotation angle about a Z-body axis of the inertial navigation system, wherein the inertial measurement unit is oriented in a second orientation, operating the inertial measurement unit oriented in the second orientation, reverse-rotating the operational inertial measurement unit by the selected-rotation angle about the Z-body axis, wherein the inertial measurement unit is oriented in the first orientation, continuously receiving information indicative of an orientation of the inertial measurement unit at a rotational compensator, and continuously-rotationally compensating navigation module output at the rotational compensator, wherein output of the rotational compensator is independent of the rotating.

Research on the technology of rotational motion for FOG strapdown inertial navigation system

Abstract: In order to improve the accuracy of strapdown inertial navigation system, the constant drift of gyro and the bias of accelerometer in inertial measurement unit (IMU) will be translated into periodic signal by the rotation of IMU, and the undesirable effects of constant drifts of inertial components can be eliminated by integral operations. The uniaxial unidirectional and reciprocating rotary compensation methods are listed in this paper, and the uniaxial rotary compensation principle is also derived. According to the scale error and the installation error of inertial components, the error characteristics of two rotation modes are analysed and simulated. Simulation results show that, the unidirectional rotation mode of IMU will lead to navigational errors due to the existence of scale factor, whereas such errors can be avoided in IMU reciprocating rotation mode.

A New Scheme of Gyroscope Free Inertial navigation System Using 9 Accelerometers

Abstract: In order to improve the convenience of installation and calibration of accelerometers, and to avoid the limitation of angular rate calculation in gyroscope free strapdown inertial navigation system (GFINS),a new scheme of gyroscope free inertial navigation system using 9 accelerometers is proposed. All 9 accelerometers are installed on three orthogonal axes, with orientations parallel to the three orthogonal axes respectively. Navigation principle and calculation procedure of the 9-accelerometer based GFINS is presented. Numerical simulations are carried out. Simulation results show that the design of scheme of GFINS is feasible and effective.

Computational Elements for Strapdown Systems

Abstract: This paper provides an overview of the primary strapdown inertial system computational elements and their interrelationship. Using an aircraft type strapdown inertial navigation system as a representative example, the paper provides differential equations for attitude, velocity, position determination, associated integral solution functions, and representative algorithms for system computer implementation. For the inertial sensor errors, angular rate sensor and accelerometer analytical models are presented including associated compensation algorithms for correction in the system computer. Sensor compensation techniques are discussed for coning, sculling, scrolling computation algorithms and for accelerometer output adjustment for physical size effect separation and anisoinertia error. Navigation error parameters are described and related to errors in the system computed attitude, velocity, position solutions. Differential equations for the navigation error parameters are presented showing error parameter propagation in response to residual inertial sensor errors (following sensor compensation) and to errors in the gravity model used in the system computer. COORDINATE FRAMES As used in this paper, a coordinate frame is an analytical abstraction defined by three mutually perpendicular unit vectors. A coordinate frame can be visualized as a set of three perpendicular lines (axes) passing through a common point (origin) with the unit vectors emanating from the origin along the axes. In this paper, the physical position of each coordinate frame’s origin is arbitrary. The principal coordinate frames utilized are the following: B Frame = "Body" coordinate frame parallel to strapdown inertial sensor axes. N Frame = "Navigation" coordinate frame having Z axis parallel to the upward vertical at the local position location. A "wander azimuth" N Frame has the horizontal X, Y axes rotating relative to non-rotating inertial space at the local vertical component of earth's rate about the Z axis. A "free azimuth" N Frame would have zero inertial rotation rate of the X, Y axes around the Z axis. A "geographic" N Frame would have the X, Y axes rotated around Z to maintain the Y axis parallel to local true north. E Frame = "Earth" referenced coordinate frame with fixed angular geometry relative to the rotating earth. I Frame = "Inertial" non-rotating coordinate frame.

Runway slope compensation for an automatic landing system

Abstract: An automatic landing system (ALS) includes an automatic landing module. The automatic landing module receives a radio altitude from a radio altimeter and any other sensor inputs for use by the automatic landing module and generates an ALS elevator command. The ALS also includes a runway slope compensation (RSC) module. The runway slope compensation module receives the ALS elevator command, the radio altitude and an inertial vertical speed from an inertial reference unit and generates an aircraft elevator command and at least one symmetric wing surface command. The aircraft elevator command and the at least one symmetric wing surface command are useable by an aircraft for runway slope compensation.

Gyroscope Free Strapdown Inertial Navigation System Using rotation modulation

Abstract: In order to improve precision of Gyroscope FreeStrapdown Inertial Navigation System (GFINS), the idea of rotation modulation is adopted. And a new scheme of GFINS using 10 accelerometers is proposed, which is convenient for modulation all of the accelerometers. Through rotating around three orthogonal axes respectively, biases of all 10 accelerometers in the GFINS can be modulated by sinusoid and cosine functions. Procedures of both navigation calculation and rotation modulation in the 10-accelerometer based GFINS are derived. The scheme of GFINS and the rotation modulation method are simulated and verified. Simulation results show that precision of GFINS has been improved by more than 50% after rotation modulation.

System and Method for Providing High-Range Capability with Closed-Loop Inertial Sensors

Abstract: An inertial sensing system including an inertial sensor having a proof mass providing a deflection signal in response to application of an inertial force, wherein the proof mass has a physical deflection limit and a selected saturation limit set below the deflection limit, elements for providing a closed-loop output in response to the deflection signal from the inertial sensor, wherein the closed-loop output is proportional to the inertial force until the saturation limit of the inertial sensor is reached, elements for providing an open-loop output in response to the deflection signal from the inertial sensor once the saturation limit is reached, and elements for summing the closed-loop output with the open-loop output when the saturation limit of the inertial sensor is reached, to provide a high-range output response for the system.

Method for Correction of Dynamic Output Signals of Inertial Sensors Having Mounting Offsets

Abstract: A method for compensating inertial sensor measurement outputs for mounting locations that are not coincident, nor orthogonal, with the vehicle center of gravity The method further utilizes vehicle angular rate measurements, data, or estimates to determine the discrete acceleration components of the composite inertial sensor measurement output

Initial alignment for strapdown inertial navigation system based on inertial frame

Abstract: A initial alignment algorithm in the inertial frame based on the alignment application of Kalman filter was presented. State and observation equations of strapdown inertial navigation system (SINS) are established using Kalman filter by the gravity vector projected in the inertial frame, and the initial alignment of the SINS based on the inertial frame on stationary base was compared with the alignment based on the geographic coordinate frame. The analysis shows that the heading misalignment's precision was improved, and this method was proved by simulation.

Astronavigation System as an Autonomous Enhancement Suite for a Strapdown Inertial Navigation System: An Evaluation

Abstract: reliability The foremost requirement for the solution of this problem is a strapdown inertial navigation system (SINS), which is autonomous, reliable and jamming resistant, but at the same time, errors in SINS increase with time Therefore, for the SINS error correction, astronavigation system (ANS) is used as an additional navaid This paper considers the ANS as an enhancement source for the SINS and presents its theoretical and practical aspects The typical ANS makes use of star-trackers which are expensive, complicated in their structure and demand a-priori definition and vigilant preparation of each onboard attitude fix To make this system cost effective and simple, an advanced configuration employs a charge coupled device (CCD) based star sensor rigidly mounted on a strapdown inertial measurement unit (SIMU) Consequently, in this evaluation, the ANS makes use of CCD based star sensors Simulation results are presented to demonstrate the validity of the method for improving the navigation reliability and performance

System and method of auto-calibration of inertial sensors

Abstract: A system comprises at least one inertial sensor (102) operable to provide inertial sensor data during a trip; a processing unit (104) coupled to the at least one inertial sensor (102), the processing unit operable to calculate navigation data based on the inertial sensor data and to estimate error in the inertial sensor data, wherein the processing unit (104) is further operable to adjust subsequent inertial sensor data received during the trip from the at least one inertial sensor (102) in order to compensate for the estimated error; and a memory (110) coupled to the navigation unit and operable to store data between power cycles; wherein the processing unit (104) is further operable to calculate a current trip error estimate from a plurality of error estimates during the trip and to estimate a repeatability error component based on the current trip error estimate and previous trip error estimates stored in the memory (110); wherein the repeatability error component is stored in the memory, the processing unit (104) being further operable to update inertial sensor data during a subsequent trip based on the repeatability error component.

The pedestrian navigation system using vision and inertial sensors

Abstract: Is this paper pedestrian inertial navigation system with vision is proposed. The navigation system using inertial sensors has problems that it is difficult to determine the initial position and the position error increases over time. To solve these problems, a vision system in addition to an inertial navigation system is used, where a camera is attached to a pedestrian. Landmarks are installed to known positions so that the position and orientation of a camera can be computed once a camera views the landmark. Using this position information, estimation errors in the inertial navigation system is compensated.

Method and system for stablishing the line of flight of an airplane

Abstract: A method is provided for establishing a physical reference inside an airplane representing the airplane's optimized line of flight based on the as-built orientation of aerodynamically significant features of the airplane. Values generated for aerodynamic pitch, roll and yaw representing the optimized line of flight are used to orient a tool reference surface outside the airplane. The orientation of the tool reference surface is recorded using an inertial reference unit placed on the tool reference surface. The tool reference surface and inertial reference unit are moved into the airplane where they are used to establish the physical reference on the airframe.

Method of determining a heading in the geographical north direction by means of an inertial unit

Abstract: A method of determining a heading in the geographical North direction by means of an inertial sensor module having three rate gyro measurement axes and three accelerometer measurement axes, the method comprising the steps of: using data from the inertial sensor module in a North-seeking mode to obtain a first heading value; using data from the inertial sensor module in a gyro-compass mode to obtain a second heading value; and determining the heading in the North direction by using the first heading value and the second heading value.

Bench calibration problem for a strapdown inertial navigation system

Abstract: We solve the bench calibration problem for a strapdown inertial navigation system. A distinguishing characteristic of the calibration algorithm under study is that the information conveyed by the bench transducers is not used directly. We study how the calibration accuracy depends on the program rotations performed by the bench platform control.

Measuring arrangement for examining movement of e.g. patient, has inertial sensor component and analysis component with functional units that are connected with position and/or angle sensors and inertial sensor in wireless manner

Abstract: The arrangement has an anatomy sensor component with a position sensor (19) and/or angle sensor for detecting relative position of a body section of an examining object e.g. human (M). An inertial sensor component has an inertial sensor (21) that is connected with a fastening unit for detachable fitting at the object such that movement of the object is not affected. Functional units of the inertial sensor component and an analysis component (31) are stationarily formed and connected with the position and/or angle sensors and the inertial sensor in a wireless and grid bound manner. An independent claim is also included for a method for providing biometric data for examining movement of a to-be-examined object such as human or vertebrate.