Showing papers on "Inertial measurement unit published in 2000"

Inertial navigation systems with geodetic applications

Abstract: Coordinate frames and transformations ordinary differential equations inertial measurement unit inertial navigation system system error dynamics stochastic processes and error models linear estimation INS initialization and alignment the global positioning system (GPS) geodetic application.

Method and apparatus for inertial guidance for an automobile navigation system

Abstract: The present invention discloses an improved vehicular inertial guidance navigation system, a.k.a. a dead reckoning system for navigation of a vehicle. The inertial guidance navigation system which may be used alone or in combination with other position determination means, such as GPS and map databases, to determine the location of a vehicle. The dead reckoning system has several advantages over existing systems. First, it can be easily mounted to the chassis of any vehicle. Second, it does not require any interface with existing sensors on the vehicle. Third, the system contains logic for removing errors in the position and heading determinations, brought about by angulation/rotation of the chassis and inertial guidance sensors, brought about by inclination or tilt of the chassis, with respect to an inertial/quasi-inertial frame of reference, such as the earth. The inertial guidance system includes: an inertial guidance sensor, a translation unit, and a logic unit. The inertial guidance sensor is suitable for coupling to the vehicle. The inertial guidance sensor senses motion of the vehicle in a non-inertial frame of reference and forming a sensor signal corresponding thereto. The translation unit is coupled to receive the sensor signal formed by the inertial guidance sensor. The translation unit translates the sensor signal into a quasi-inertial frame of reference and forms a translated signal corresponding thereto. The logic unit receives the translated signal formed by the translation unit and converts converting the translated signal into an estimated position and heading of the vehicle.

Inertial and Magnetic Tracking of Limb Segment Orientation for Inserting Humans into Synthetic Environments

Abstract: : Current motion tracking technologies fail to provide accurate wide area tracking of multiple users without interference and occlusion problems. This research proposes to overcome current limitations using nine-axis magnetic/angular/rate/gravity (MARG) sensors combined with a quaternion-based complementary filter algorithm capable of continuously correcting for drift and following angular motion through all orientations without singularities. Primarily, this research involves the development of a prototype tracking system to demonstrate the feasibility of MARG sensor body motion tracking Mathematical analysis and computer simulation are used to validate the correctness of the complementary filter algorithm The implemented human body model utilizes the world-coordinate reference frame orientation data provided in quaternion form by the complementary filter and orients each limb segment independently. Calibration of the model and the inertial sensors is accomplished using simple but effective algorithms. Physical experiments demonstrate the utility of the proposed system by tracking of human limbs in real-time using multiple MARG sensors. The system is "sourceless" and does not suffer from range restrictions and interference problems. This new technology overcomes the limitations of motion tracking technologies currently in use. It has the potential to provide wide area tracking of multiple users in virtual environment and augmented reality applications.

Interruption-free hand-held positioning method and system thereof

Abstract: An interruption-free hand-held positioning method and system, carried by a person, includes an inertial measurement unit, a north finder, a velocity producer, a positioning assistant, a navigation processor, a wireless communication device, and a display device and map database. Output signals of the inertial measurement unit, the velocity producer, the positioning assistant, and the north finder are processed to obtain highly accurate position measurements of the person. The user's position information can be exchanged with other users through the wireless communication device, and the location and surrounding information can be displayed on the display device by accessing a map database with the person position information.

Vehicle positioning method and system thereof

Abstract: An improved fully-coupled vehicle positioning process and system thereof can substantially solve the problems encountered in global positioning system-only and inertial navigation system-only, such as loss of global positioning satellite signal, sensibility to jamming and spoofing, and inertial solution's drift over time, in which the velocity and acceleration from an inertial navigation processor are used to aid the code and carrier phase tracking of the global positioning system satellite signals, so as to enhance the performance of the global positioning and inertial integration system, even in heavy jamming and high dynamic environments. The improved fully-coupled GPS/IMU vehicle positioning system includes an IMU (inertial measurement unit) and a GPS processor which are connected to a central navigation processor to produce navigation solution that is output to an I/O (input/output) interface.

Automated guided apparatus suitable for toping applications

Abstract: An automated guided apparatus capable of accurately determining its position within a walled environment such as a mine or building. A mobile unit incorporating an inertial measurement unit and a gray scale vision system processor/camera and/or a laser pointer is able to initialize its location and then update its location within the environment. The apparatus is especially adapted for producing tunnel plan views (“TOPES”) and also for guiding equipment through such environments.

A Low-Cost, Redundant Inertial Measurement Unit for Unmanned Air Vehicles:

Abstract: This paper discusses the development of a low-cost, redundant, strapdown inertial measurement unit (IMU). The unit comprises four ceramic vibrating structure gyroscopes and four QLC 400 acceleromet...

Head tracking relative to a moving vehicle or simulator platform using differential inertial sensors

Abstract: Inertial trackers have been successfully applied to a wide range of HMD applications including virtual environment training, VR gaining and even fixed-base vehicle simulation, in which they have gained widespread acceptance due to their superior resolution and low latency. Until now, it has been impossible to use inertial trackers in applications which require tracking motion relative to a moving platform, such as motion-base simulators, virtual environment trainers deployed on board ships, and live vehicular applications including helmet-mounted cueing systems and enhanced vision or situational awareness displays. This paper describes a new technique which makes it possible to use inertial head- tracking systems on-board moving platforms by computing the motion of a `tracking' Inertial Measurement Unit (IMU) mounted on the HMD relative to a `reference' IMU rigidly attached to the moving platform. Detailed kinematic equations are derived, and simulation results are provided for the particular case of an inertial tracker with drift correction by means of ultrasonic ranging sensors, but the conclusions can be applied to hybrid inertial trackers involving optical, magnetic, or RF drift correction as well.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Self-contained/interruption-free positioning method and system thereof

Abstract: A self-contained/interruption-free earth's surface positioning method and system, carried by a user on the earth's surface, includes an inertial measurement unit, a north finder, a velocity producer, an altitude measurement device, a GPS (Global Positioning System) receiver, a data link, a navigation processor, a wireless communication device, and a display device and map database Output signals of the inertial measurement unit, the velocity producer, altitude measurement device, the GPS receiver, the data link, and the north finder are processed to obtain highly accurate position measurements of the user The user's position information can be exchanged with other users through the wireless communication device, and the location and surrounding information can be displayed on the display device by accessing a map database with the user position information

Self-contained positioning method and system thereof for water and land vehicles

Abstract: A positioning method and system for water and land vehicles is disclosed for highly accurate and self-contained operation. In which, an inertial navigation system (INS) is built on the micro MEMS (MicroElectroMechanicalSystem) IMU that is the core of the position determination system. To compensate the error of the INS, multiple navigation sensors are integrated into the system. The magnetic sensor is used as a magnetic field sensor to measure the heading of the vehicle. The odometer is used to measure the distance when the vehicle is on land. An automated Zero velocity updating method is used to calibrate the ever increasing INS errors. When the vehicle is in the water, a velocimeter is used to measure water speed for the INS aiding.

An Active Hand-Held Instrument for Enhanced Microsurgical Accuracy

Abstract: This paper presents the first prototype of an active hand-held instrument to sense and compensate physiological tremor and other unwanted movement during vitreoretinal microsurgery. The instrument incorporates six inertial sensors (three accelerometers and three rate gyros) to detect motion of the handle. The movement of the instrument tip in three dimensions is then obtained using appropriate kinematic calculations. The motion captured is processed to discriminate between desired and undesired components of motion. Tremor canceling will be implemented via the weighted-frequency Fourier linear combiner (WFLC) algorithm, and compensation of non-tremorous erroneous motion via an experimental neural-network technique. The instrument tip is attached to a three-degree-of-freedom parallel manipulator, actuated by three piezoelectric stacks. The actuators move the tool tip in opposition to the motion of the tremor or other erroneous motion, thereby suppressing the error. Experimental results show that the prototype is able to follow one-dimensional and three-dimensional trajectories with rms error of 2.5 μm and 11.2 μm respectively.

Micromachined Inertial Sensors: The State-of-the-Art and a Look into the Future:

Abstract: In the paper a review is given of the current state of the art of micromachined inertial sensors accelerometers and gyroscopes. These sensors can be used in a wide range of applications and micromachined devices have a number of significant advantages over their conventional counterparts such as lower cost, smaller form factor and lower power consumption. An overview will be given over the diverse technical implementations which can be classified by the manufacturing process, the type of transduction mechanism, and the type of control system. While micromachined accelerometers are already commercially available from a range of companies, gyroscopes are subject to intensive research worldwide and a series of problems remains to be resolved. A novel approach to inertial sensing, currently under investigation at Southampton University, is introduced which relies on electrostatic levitation and has the potential to overcome some inherent drawbacks of prevailing concepts.

Real-time integrated vehicle positioning method and system with differential GPS

Abstract: A real-time integrated vehicle positioning method and system with differential GPS can substantially solve the problems encountered in either the global positioning system-only or the inertial navigation system-only, such as loss of global positioning satellite signal, sensitivity to jamming and spoofing, and an inertial solution's drift over time. In the present invention, the velocity and acceleration from an inertial navigation processor of the integrated GPS/INS system are used to aid the code and carrier phase tracking of the global positioning system satellite signals, so as to enhance the performance of the global positioning and inertial integration system, even in heavy jamming and high dynamic environments. To improve the accuracy of the integrated GPS/INS navigation system, phase measurements are used and the idea of the differential GPS is employed. However, integer ambiguities have to be resolved for high accuracy positioning. Therefore, in the present invention a new on-the-fly ambiguity resolution technique is disclosed to resolve double difference integer ambiguities. The real-time fully-coupled GPS/IMU vehicle positioning system includes an IMU (inertial measurement unit), a GPS processor, and a data link which are connected to a central navigation processor to produce a navigation solution that is output to an I/O (input/output) interface.

Integrated sensor orientation - an oeepe test

Abstract: The topic of image orientation by combined aerial triangulation with GPS/IMU, also called integrated sensor orientation, has received much attention lately. One of the main questions of fundamental relevance is, if and under which conditions the direct determination of the parameters of exterior orientation via GPS and IMU can be a complete substitute for aerial triangulation. A more practical question deals with the possibilities of an optimum combination of the different methods using a minimum of ground control points. The European Organisation for Experimental Photogrammetric Research (OEEPE) has embarked on a test investigating these issues. The main focus of the test is on the obtainable accuracy of integrated sensor orientation for large scale topographic mapping as determined at exterior orientation elements and at independent points on the ground. In this paper we describe details of the test which, when presented at the ISPRS Congress in Amsterdam, is still open for interested participants to join.

Process and system of coupled real-time GPS/IMU simulation with differential GPS

Abstract: A coupled real-time GPS/IMU simulation method with differential GPS includes the steps of receiving real-time trajectory data from a 6DOF trajectory generator and generating GPS simulated measurements (rover and reference) and inertial measurement unit simulated electronic signals based on the real GPS models and IMU models, respectively, and injecting those simulated data into an on-board integrated GPS/INS (global positioning system/inertial navigation system). Therefore, the coupled real-time GPS/IMU simulation method with differential GPS can be applied to evaluate the performance of the integrated GPS/INS in the area of high accuracy positioning in addition to the regular evaluation (one receiver mode).

Direct Geocoding - is Aerial Triangulation Obsolete?

Abstract: By direct geocoding or direct georeferencing, i.e. the direct measurement of the exterior orientation of an imaging sensor using an integrated system consisting of receivers of the Global Positioning System (GPS) and a strap-down Inertial Measurement Unit (IMU), required ground control and tie point information could be reduced or eliminated significantly. Using integrated GPS/inertial systems many applications can be realized more efficiently and economically. In principle, aerial triangulation will become obsolete if the exterior orientations are obtained directly with sufficient accuracy and if there are no errors in the calibration of the multi-sensor system (GPS, IMU and imaging sensor). This article describes a well controlled airborne test to investigate the potential and accuracy of a commercially available integrated GPS/inertial system (POS/DG310 from Applanix, Canada). Within this test standard aerial triangulation is used as reference for direct georeferencing. The empirical accuracy of direct georeferencing obtained from this test might help to answer the question, whether aerial triangulation will become obsolete in future or not.

Tuned support structure for structure-borne noise reduction of inertial navigator with dithered ring laser gyros (RLG)

Abstract: Litton Marine Systems is manufacturing the third generation of the marine inertial navigators at the Sperry Marine Division using a new generation of dithered ring laser gyros (RLG) by Honeywell To satisfy the US and foreign navies, stringent military requirements for shock (MIL-STD-901D), vibration (MIL-STD-167) and structure-borne noise (MIL-STD-740) demanded that a new approach in vibration control be employed A combined structure supporting the inertial sensor assembly (ISA) is designed with nominal vibration frequencies outside the dithered ring laser gyro's forcing frequencies The ISA can then be rigidly supported without causing transmission of structure-borne noise Structure-borne noise levels are then attenuated while easily maintaining alignment of the sensor axes This paper addresses a passive vibration control solution implemented on the inertial measurement unit (IMU) of the MK39 Mod3A inertial navigator to meet the structure-borne noise levels of MIL-STD-740-2 By using a compact auxiliary mass, a tuned support structure housing a Honeywell DIG-20 ISA is achieved The robustness of this tuned support structure is demonstrated as Litton Marine Systems expands the product line with the enhanced system performance and high shock single axis indexed MK39 Mod3C inertial navigator system (INS) Presented analytical and experimental results demonstrate the effectiveness of the MK39 Mod3A auxiliary mass basic design This design required no further tuning for the MK39 Mod3C application The shock and vibration advantage of using this approach on an inertial navigator is highlighted The impact of the indexer assembly on system performance and wobble for the shock-isolated system is discussed

Observability Analysis of GPS Aided INS

Abstract: This paper investigates observability properties of strapdown inertial navigation system (INS) aided by the Global Positioning System (GPS). Observability analysis is made on a linear error dynamics model of navigation equations in the Earth-centered Earth-fixed (ECEF) frame for both loosely-coupled and tightly-coupled integrations. Position and velocity measurements are given from multiple GPS antennas mounted on the vehicle. The motivation to consider multiple GPS antennas is that the lever-arms of them play an important role in observing vehicle attitude and biases of inertial motion unit (IMU) during navigation. Biases of IMU are assumed to be constant. Necessary and sufficient conditions for the instantaneous observability on the GPS/INS integrations are given. A numerical simulation is given to show the effectiveness of multiple GPS antennas in estimating vehicle attitude and biases of IMU when IMU has considerable magnitude of biases.

Photogrammetric solftware for the LH Systems ADS40 Airborne Digital Sensors

Abstract: Airborne linear array sensors present new challenges for photogrammetric software. The push-broom nature of these sensor systems has the potential for very high quality images, but these are heavily influenced by the dynamics of the aircraft during acquisition. Fortunately, highly precise position and attitude measurements have become possible, using today's inertial measuring units (IMUs). This allows image restoration to the sub-pixel level. The sensor discussed in detail here is a "three-line camera" with additional multispectral lines. The three lines are one looking forward, one in the nadir position and one looking backward with respect to the flight path. Extensive software processes are necessary to produce traditional photogrammetric products from a push-broom airborne sensor. The first steps of the ground processing flow are off-loading imagery and supporting data from the mass memory system of the sensor, post-processing of GPS/IMU data and image rectification into stereo-viewable and matchable form. After this processing, the images can be used similarly to classical aerial photography. This includes semi-automated triangulation with and without ground control, DTM production from multiple stereo views, vector extraction in mono and stereo, and orthophoto and mosaic production. The paper analyses the differences to classical photogrammetric processing for all processing steps and closes with a discussion of the advantages and disadvantages of this new type of photogrammetric imagery.

Positioning refinement algorithm

Abstract: A method is provided for correcting errors in position derived from an inertial measurement unit (IMU), by performing a first zero velocity update at a time when the IMU is at rest, recording the time and position of the IMU at a subsequent start of a period of interest after the first zero velocity update, recording the time and position of the IMU at the end of the period of interest, performing a second zero velocity update at the end of the period of interest with the IMU at rest, and then recording a velocity indicated from the IMU, and deriving an accumulated error in position from the recorded data, by approximating errors in velocity by a function of time with a parameter determined from the recorded indicated velocity, and integrating the function over the period of interest to determine the accumulated error in position during the period of interest.

3-D Motion and Structure Estimation Using Inertial Sensors and Computer Vision for Augmented Reality

Abstract: A new method for registration in augmented reality (AR) was developed that simultaneously tracks the position, orientation, and motion of the user’s head, as well as estimating the three-dimensional (3-D) structure of the scene. The method fuses data from headmounted cameras and head-mounted inertial sensors. Two Extended Kalman Filters (EKF) are used; one of which estimates the motion of the user’s head and the other that estimates the 3-D locations of points in the scene. A recursive loop is used between the two EKFs. The algorithm was tested using a combination of synthetic and real data, and in general was found to perform well. A further test showed that a system using two cameras performed much better than a system using a single camera, although improving the accuracy of the inertial sensors can partially compensate for the loss of one camera. The method is suitable for use in completely unstructured and unprepared environments. Unlike previous work in this area, this method requires no a priori knowledge about the scene, and can work in environments where the objects of interest are close to the user. Index terms : Augmented reality, pose estimation, registration, Kalman filter, structure from motion, computer vision, inertial sensors Draft of a paper submitted to Presence: Teleoperators and Virtual Environments, November 2000

The method of and apparatus for determining the path of a well bore under drilling conditions

Abstract: Apparatus for determining the path of a well bore during drilling, comprises an inertial measurement unit (12) for providing data from which position, velocity and attitude can be derived, the measurement unit comprising a plurality of inertial sensors mounted on a platform assembly which is, in use, disposed within a drill string (6), and a drive unit (5) for rotating the platform assembly so as to control the rate of angular displacement of the platform assembly with respect to an Earth fixed reference frame.

Inertial measurement unit with magnetometer for detecting stationarity

Abstract: A device for measuring a velocity and/or position of a body includes a magnetometer and a measurement unit. The magnetometer is configured to sense a magnetic flux to which the body is exposed. The measurement unit includes a sensor sensing one of an acceleration and a velocity of the body. The measurement unit also includes a processor coupled to the magnetometer and to the measurement unit and configured to determine one on a velocity value and a position value for the body based on the sensed magnetic flux and based or one of the sensed acceleration and the sensed velocity of the body.

The projectile GRAM SAASM for ERGM and Excalibur

Abstract: The Army and the Navy are each developing a GPS guided projectile. The Navy is developing the Extended Range Guided Munition (ERGM), a projectile for a 5" deck-gun. The Army is developing the XM982, now renamed the Excalibur, a projectile for 155-mm platforms such as Crusader and Palladin. These projectiles are to be guided in-flight by a GPS aligned inertial measurement unit (IMU). The distinction between a "guided projectile" and other guided munitions is that a projectile receives most or all of its motive force from a powder charge in a gun barrel. This places the first of a series of severe requirements on the projectile GPS receiver. It must be gun-hardened to survive the shock of gunfire. The range of a projectile, compared to a motor-driven munition, is limited. This means short flight times and requires very fast initial acquisition. High jamming conditions are expected since these are tactical weapons used in a battlefield environment. Collectively, the projectile GPS receiver must have very fast direct-Y acquisition capability that can operate in a high jamming environment. It must also be tightly coupled with the guidance IMU to enhance jammer tolerance during track. The projectile GPS Receiver Application Module (GRAM) must be equipped with a Selective Availability/Anti-Spoof Module (SAASM) for battlefield security. It must draw minimal power to conserve limited on-board battery capacity. Finally and foremost, these guided projectiles must be manufactured in high quantities. The recurring cost of the GPS guidance is a major consideration. This paper describes IEC's latest GPS receiver offering that is designed specifically to satisfy these projectile application requirements. The direct-Y acquisition issues, including acquisition correlator and reference oscillator considerations are discussed. The jammer tolerance features and how they interact with acquisition and track are described. The SAASM design is described and the complete GRAM SAASM is described and illustrated.

Low cost guidance for the Multiple Launch Rocket System (MLRS) artillery rocket

Abstract: The US Army Aviation and Missile Command has demonstrated the application of advanced technology to significantly improve the accuracy and range of the US Army's Multiple Launch Rocket System (MLRS) through the Guided MLRS Advanced Technology Demonstration (ATD). The addition of a cost-effective guidance and control package to the rocket results in a weapon system that can defeat the target at ranges up to 70 km with significantly fewer rounds. This not only increases the destructive capability of the system but also reduces the cost of the expended ammunition, the cost to transport the ammunition to the combat zone, and the number of launchers required to execute the mission. The guidance kit is housed in the nose of the MLRS and consists of an inertial measurement unit (IMU), four independent electro-mechanically actuated canards, a Global Position System (GPS) receiver, GPS antennas, a thermal battery, a guidance computer, and power supply electronics. Roll decoupling of the warhead and motor section was required to allow roll control of the guidance section to enable accurate inertial navigation and was accomplished by joining the two sections with a roll bearing. Five flight missiles were built and tested during the ATD. Two IMU vendors were selected to provide flight units (3 flights used vendor A and 2 flights used vendor B). A tightly coupled 8 channel GPS receiver was flown on all flights. This paper discusses the ATD development effort and presents flight test results.

Case study: Inertial measurement unit calibration platform

Abstract: The Department of Mechanical Engineering and the Avionics Engineering Center at Ohio University are developing an electromechanical system for the calibration of an inertial measurement unit (IMU) using global positioning system (GPS) antennas. The GPS antennas and IMU are mounted to a common platform to be oriented in the angular roll, pitch, and yaw motions. Vertical motion is also included to test the systems in a vibrational manner. A 4-DOF system based on the parallel carpal wrist is under development for this task. High-accuracy positioning is not required from the platform since the GPS technology provides absolute positioning for the IMU calibration process. © 2000 John Wiley & Sons, Inc.

GPS guidance system increases projectile accuracy

Abstract: To meet the size/performance and cost-driven goals required for more advanced projectile and mortar applications, IEC focused its efforts on function consolidation, electronic signal protection, ultra-deep sensor integration, and processing stability. IEC's development has been in the utilization of silicon-based micro-machine technology for the inertial sensor, high levels of processor integration, and hardware function consolidation, making the guidance package inherently immune to the vibration and high G shock effects of the launch. In addition, the size and power are sufficiently reduced to fit the constraints of the fuse well. While a GPS "only"-based guidance system seemed an ideal solution for the lowest cost implementation of smart weapon guidance, the potential for signal jamming meant that a GPS "only" solution would not be able to guide the projectile to the target. To resolve this limitation, an anti-jam (AJ) capability had to be incorporated into the GPS receiver, and a miniature on-board inertial measurement unit (IMU) had to be part of the system. Initial laboratory tests have proven that the GPS/inertial guidance system, enhanced with a robust, low-cost AJ subsystem, performs consistently well under simulated battlefield conditions.

Inertial Measurement Technology in the Satellite Navigation Environment

Abstract: Inertial measurement technology can make a valuable contribution to the development of autonomous, sole-means Satellite Navigation Systems. The integration of inertial measurement technology and GPS can enable a significant performance improvement to the various configurations of GPS, WAAS and LAAS. This paper provides a conceptual discussion of the safety and performance benefits that inertial measurement and integration technology can bring to the satellite navigation environment.