Showing papers on "Inertial navigation system published in 1997"

Strapdown inertial navigation technology

Abstract: Inertial navigation is widely used for the guidance of aircraft, missiles ships and land vehicles, as well as in a number of novel applications such as surveying underground pipelines in drilling operations. This book discusses the physical principles of inertial navigation, the associated growth of errors and their compensation. It draws current technological developments, provides an indication of potential future trends and covers a broad range of applications. New chapters on MEMS (microelectromechanical systems) technology and inertial system applications are included.

Mobile Robot Positioning - Sensors and Techniques

Abstract: : Exact knowledge of the position of a vehicle is a fundamental problem in mobile robot applications. In the search for a solution, researchers and engineers have developed a variety of systems, sensors, and techniques for mobile robot positioning. This paper provides a review of relevant mobile robot positioning technologies. The paper defines seven categories for positioning systems: (1) Odometry, (2) Inertial Navigation, (3) Magnetic Compasses, (4) Active Beacons, (5) Global Positioning Systems, (6) Landmark Navigation, and (7) Model Matching. The characteristics of each category are discussed and examples of existing technologies are given for each category. The field of mobile robot navigation is active and vibrant, with more great systems and ideas being developed continuously. For this reason the examples presented in this paper serve only to represent their respective categories; they do not represent a judgment by the authors. Many ingenious approaches can be found in the literature, although, for reasons of brevity, not all could be cited in this paper. The appendix contains a tabular comparison of the positioning systems discussed in this review that includes system and description, features, accuracy (position), accuracy (orientation), effective range, and source of information. (47 refs.)

Fundamentals of high accuracy inertial navigation

Abstract: Part 1 Inertial Navigation: Notation, Coordinate Systems and Units Equations of Motion in a Central Force Gravity Field Inertial Instrumentation Calibration Initial Alignment and Attitude Computation Geodetic Variables and Constants Equations of Motion with General Gravity Model. Part 2 Inertial Navigation with Aids: Inertial Navigation with External Measurements Error Equations for the Kalman Filter State Variable Error Models. Part 3 Accuracy Analysis: Accuracy Criteria and Analysis Techniques Error Equations for Calibration, Alignment and Initialization Evaluation of Gravity Model Error Effects. Appendices: Matrix Inverse Formulas LaPlace Transforms Quaternions Associated Legendre Functions Associated Legendre Function Derivatives Procedure for Generating Gravity Disturbance Realizations Procedure for Generating Specific Force Profile.

A navigation/guidance system for a land-based vehicle

Abstract: A navigation/guidance system (10) uses a dead reckoning navigator with periodic GPS fixes to correct the drift of the inertial system. The navigation system (10) primarily uses speed sensed by Doppler radar (30) and attitude and heading sensed by a set of gyros (24). The navigation system (10) uses various processes to compensate for any sensor errors. The system uses attitude data to compensate for GPS leverarm errors. The system can be used on a land-based vehicle (60) to economically and accurately provide navigation data.

Optimal nonlinear filtering in GPS/INS integration

Abstract: The application of optimal nonlinear/non-Gaussian filtering to the problem of INS/GPS integration in critical situations is described. This approach is made possible by a new technique called particle filtering, and exhibits superior performance when compared with classical suboptimal techniques such as extended Kalman filtering. Particle filtering theory is introduced and GPS/INS integration simulation results are discussed.

Nonlinear filtering methods application in INS alignment

Abstract: The problem of course alignment of inertial navigation systems is considered. Error equations of nonlinear character have been obtained at a considerable level of a priori course uncertainty. The algorithm for solving the problem of optimal estimation of the state vector described by nonlinear equations from linear measurements has been developed for the analysis of a potential alignment accuracy with the piecewise-Gaussian approximation of a posteriori density used. The results of the study of efficiency of various suboptimal alignment algorithms obtained by the use of the software developed are presented and discussed.

Stand alone terrain conflict detector and operating methods therefor

Abstract: A stand alone terrain conflict detector of an aircraft includes a global positioning system (GPS) receiver, an inertial navigation system, navigational and topographical databases, a control panel, a central processing unit (CPU), which CPU generates position data, a current flight path vector and control signals, an obstacle detector which receives the position data and the current flight path vector and which generates a flight path signal, an alert signal identifying a terrain threat to the aircraft and a projected flight path vector, a video generator coupled to the obstacle detector and the CPU, and a display connected to the video generator. The display outputs one of a 2D image, a first 3D image and a second 3D image and the terrain threat generated by video generator. Advantageously, the video generator generates the 2D image responsive to the flight path signal and navigational data during the first mode of operation, generates the first 3D image including the projected flight path vector responsive to the flight path vector and one of navigational data and topographical data during the second mode of operation, and automatically generates, whenever the alert signal is generated, the second 3D image, including an escape vector, having a scale different than that of the first 3D image, responsive to the projected flight path vector and one of the navigational data and the topographical data during the third mode of operation. A method for operating the stand alone terrain conflict detector is also described.

Experiments in autonomous underground guidance

Abstract: This paper presents the results of an experimental program for evaluating sensors and sensing technologies in an underground mining applications. The objective of the experiments is to infer what combinations of sensors will provide reliable navigation systems for autonomous vehicles operating in a harsh underground environment. Results from a wide range of sensors are presented and analysed. A conclusion as to the best combination of sensors is drawn.

Method for monitoring integrity of an integrated GPS and INU system

Abstract: A method for monitoring the integrity of an integrated positioning system located on a mobile machine is provided. The integrated positioning system includes a GPS receiver and an inertial navigation unit (INU). The INU includes an odometer, a Doppler radar, a gyroscope, and a sensor for measuring the steering angle of the mobile machine. The method includes the steps of receiving a GPS position estimate from a GPS receiver, receiving an INU position estimate from an inertial navigation unit, and comparing the GPS position estimate and the INU position estimate. If the two position estimates are the same, then the system is VALID. Otherwise, the velocity of the mobile machine as determined by the odometer and velocity as determined by the Doppler radar are compared. If the difference is greater than a first predetermined threshold, then the INU is determined to be INVALID. Otherwise a heading rate from gyroscope is compared with a calculated heading rate based on measured steering angle and velocity. If the difference is greater than a second predetermined threshold, then the INU is INVALID, otherwise the GPS is INVALID.

Attitude determination method and system

Abstract: A method for use in vehicle attitude determination includes generating GPS attitude solutions for a vehicle using three or more antennas receiving GPS signals from two or more space vehicles. An inertial navigation system is initialized by setting the attitude of the inertial navigation system to a GPS attitude solution generated for the vehicle and/or the attitude of the inertial navigation system is updated using the GPS attitude solutions generated for the vehicle or GPS estimated attitude error generated for the vehicle. A system for use in vehicle navigation is also provided. The system generally includes three or more GPS antenna/receiver sets associated with a vehicle, an inertial measurement unit that provides inertial measurements for the vehicle, a processing unit of the system having the capability for generating GPS attitude computations for the vehicle using the three or more GPS antenna/receiver sets and signals from two or more space vehicles; the GPS attitude computations include at least one of absolute attitudes and estimated attitude errors. The processing unit of the system also includes a filter for generating estimates of attitude for the vehicle using the inertial measurements from the inertial measurement unit and the attitude computations.

Slip modelling and aided inertial navigation of an LHD

Abstract: This paper describes the theoretical development and experimental evaluation of a guidance system for an autonomous load, haul and dump truck (LHD) for use in underground mining. The particular contributions of this paper are in designing the navigation system to be able to cope with vehicle slip in rough uneven terrain using information from an inertial navigation system (INS) and a bearing only laser. Results are presented using data obtained during field trials.

The Theseus autonomous underwater vehicle. A Canadian success story

Abstract: International submarine Engineering Research and the Esquimalt Defence Research Detachment of the Defence Research Establishment Atlantic have worked together to develop a large autonomous underwater vehicle, named Theseus, for laying optical fiber cables in ice-covered waters. It was able to lay a fiber optic cable in a completely autonomous mode for a distance of 200 km under Arctic sea-fee and then return to the launch station for recovery. It operates in either depth-keeping mode or bottom-following mode, was designed to operate at a maximum depth of 1000 m, and has operated at a depth of 425 m. The vehicle is equipped with an inertial navigation unit and Doppler sonar speed sensor for autonomous navigation, a forward-looking obstacle avoidance sonar, an acoustic homing system, and acoustic transponders for use with surface tracking stations. An acoustic telemetry system enables communication with Theseus from surface stations, and an optical telemetry system is used for system monitoring while Theseus is laying optical fiber cable. All sub-systems are controlled by an MC68030 based sensor integration and control computer. Theseus' qualities of covertness, long endurance and precise navigation make possible such tasks as long base-line oceanographic data collection, remote route surveys, remote mine hunting, the rapid deployment of acoustic and non-acoustic surveillance systems, and even the towing of mobile sensor arrays. The paper describes the vehicle and presents the results of the evaluation trials and its first cable laying mission.

A relative navigation system for formation flight

Abstract: A relative navigation system based on both the Inertial Navigation System (INS) and the Global Positioning System (GPS) is developed to support situational awareness during formation flight. The architecture of the system requires an INS/GPS integration across two aircraft via a data link. A fault-tolerant federated filter is used to estimate the relative INS errors based on relative GPS measurements and a range measurement obtained from the data link. The filter is constructed based on a reduced-order model of the relative INS error process. A method for analyzing the filter performance is presented. A case involving two helicopters in formation flight is studied under three different night trajectories to account for the effect of vehicle motion on the INS state transition matrix. The results of the covariance analysis are compared with actual night results over an instrumented test range.

Aircraft piloting aid system using a head-up display

Abstract: An aircraft piloting aid system mainly used during take-off and landing under adverse visibility conditions is disclosed. To make use of head-up displays which display artificial horizon line, aircraft pitch attitude and ground speed vector symbols without using an inertial reference system (IRS) to provide heading and attitude data, a non-inertial attitude heading reference system (AHRS) combined with a compass is used and data therefrom is periodically corrected in order to display attitude symbols by means of corrected data rather than raw data from the AHRS. Correction is provided by two GPS receivers (GPS1, GPS2) connected to antennas (A1, A2) on top of the aircraft, and an interferometric RF carrier phase measurement is performed to determine an aircraft direction vector. The system is useful for modernising aircraft fitted with non-inertial AHRSs to enable take-off and landing under all conditions, including conditions of very poor visibility.

Inertial navigation aided with GPS information

Abstract: This paper presents a dynamic alignment algorithm for a six-degree of freedom inertial unit. A differential GPS is used as external sensor. It provides decorrelated range position and Doppler velocity information. A simplified error model valid for a local area is also presented. An indirect Kalman filter approach is used to fuse high frequency inertial information with low frequency GPS data. Experimental results are presented showing that the filter is able to predict high frequency manoeuvres as well as detect multipath errors in the GPS information.

Accelerometer based gyro-free multi-sensor generic inertial device for automotive applications

Abstract: The importance of developing a unified inexpensive generic inertial device is substantiated in this paper based on the current situation in the automotive market. A gyro-free architecture of the generic inertial device is proposed as a solution. Exclusion of gyroscopes from the inertial system allows one to achieve an essential decrease in price, while the inertial system based on multiple accelerometers distributed inside the vehicle can still deliver data at sufficient accuracy for automotive inertially-aided systems. The paper also focuses on the choice of mathematical models as a Harwich of models evolving from the basic six sensor gyro free model, and shows the importance of optimization of parts of the design that permit formalization but involve tedious work. The original approach to the choice of optimal sequence of elementary operations is then described.

Imu in-motion alignment without benefit of attitude initialization

Abstract: Establishment of local-level wander azimuth navigation and body reference frames for an inertial navigation system (INS) based on outputs of an inertial measurement unit (IMU) without the use of initial attitude information is addressed These frames are established using a Kalman filter algorithm implemented with an INS system error model formulated for large heading errors and using position measurement updates Only position and velocity in a geographic reference frame are used for initialization of the INS navigation equations This data is available from GPS receivers; however, in this paper, an aircraft navigation system's data is used instead to demonstrate the alignment performance using data from actual flight tests

Synthesized attitude and heading inertial reference

Abstract: An inertial reference system for determining the attitude and rate of change of attitude of a vehicle such as an aircraft is disclosed. Redundancy of the inertial reference system may be accomplished by replacement of one of the fiber optic gyroscopes of an otherwise dual fiber optic gyros installation with a low-cost reference IMU. Failure detection and isolation of a fiber optic gyroscope system may be accomplished with a low-cost reference IMU rather than with an additional fiber optic gyroscope. The information provided by the eliminated fiber optic gyroscope is synthesized from the output of the remaining fiber optic gyroscope and the output of the low-cost reference IMU.

Dead reckoning navigation for an autonomous mobile robot using a differential encoder and a gyroscope

Abstract: Dead reckoning navigation algorithm using a differential encoder and a gyroscope is proposed for an autonomous mobile robot (AMR). The indirect Kalman filter which feeds back the error estimates to the main navigation algorithm mutually compensates the differential encoder errors and the gyroscope errors. The experimental results show that the proposed AMR navigation algorithm provides the reliable position and heading of the AMR without any external positioning system.

Commercial vision of silicon based inertial sensors

Abstract: This paper reviews recent R&D and commercial status of inertial sensors using silicon micromachining technologies and discusses the requirements for commercialization of the research results Successful commercial implantation requires involvement at the design, process, manufacturing, applications so that low cost, reliability, and better performance can be achieved It is also necessary to have a clear understanding of the market and IC mentality The paper forecasts the potential applications and future market of the silicon based inertial sensors

The navigation system of an autonomous underwater vehicle for Antarctic exploration

Abstract: In the context of the Italian Scientific Program for Antarctica an underwater vehicle is being developed that will be capable of operating autonomously for many hours under the Antarctic shelf or in sea areas covered by floating ice blocks. The vehicle must therefore carry a navigation system satisfying severe constraints on accuracy, size, and power consumption. During navigation the vehicle cannot use low-cost systems such as magnetic compasses (ineffective near the Earth poles), GPSs (which cannot be used underwater), or acoustic transponders (because of the long range of the missions). To estimate its own heading and position, the vehicle can only exploit measurements of acceleration, rotation rate, and velocity. The optimal integration of inertial and velocity measurements is accomplished by using a Kalman filter for correcting the effect of the biases of the inertial sensors (which would cause relevant long-term position errors) by exploiting a velocity measurement. Conceptually, the filter blends the high-frequency components of the inertial estimation with the low-frequency components of the velocity measurement, giving a long-term position estimation that is much more accurate than that obtainable using only accelerometers. A Doppler-dumped inertial navigation system has been developed using the recently available subsystems and implementing innovative signal processing techniques, obtaining a satisfactory trade-off between reliability, cost, accuracy, size, and power requirements. The inertial sensors (three accelerometers and three ring laser gyroscopes) are packaged in a small-size and relatively low cost, strap-down inertial unit. The velocimeter is a compact low-power Doppler sonar specifically designed for underwater vehicles. Signal processing is implemented on a general purpose computer having small space and power requirements. The performance of the Kalman filter was optimized by using the "indexing" technique, which consists of periodically rotating the inertial unit to increase the observability of the Kalman filter states and thus improve the correction of the biases of the inertial measurements. In the paper, the navigation system is described and its performance analyzed, showing the effectiveness of the indexing technique in improving the Kalman filter performance both in convergence speed and in estimation accuracy.

Micromachined inertial sensors for vehicles

Abstract: Micromachined silicon sensors offer tremendous cost, size, and reliability improvements for guidance, navigation, and control (GNC however, it will ultimately be driven by high-volume commercial markets with target prices below $25 per instrument. The paper describes advances in micromechanical gyro and accelerometer design and packaging. Performance of a prototype automotive traction control module, in pilot production, and a planned automobile suspension control module are described. The concept of a 3-cubic-inch, multi-purpose MEMS inertial system, based on a three-gyro, three-accelerometer system under development for a guided artillery shell, is discussed for automotive applications. Plans for future cost and size reduction are presented.

TIER II Plus airborne EO sensor LOS control and image geolocation

Abstract: TIER II Plus is a high altitude unmanned reconnaissance aircraft carrying a synthetic aperture radar (SAR) and electro-optical/infrared (EOIR) sensor that will provide all-weather, day and night, high resolution imagery of ground targets for joint armed forces users. Its high area coverage rate is achieved in near real-time by transmitting the collected imagery while the vehicle is airborne and relaying that imagery via satellite to ground stations for processing and dissemination. The electro-optical sensor assembly consists of a mid-wave infra-red (MWIR) staring array built by Hughes Aircraft Company and a CCD visible staring array from Kodak that share common reflective optics. The telescope/sensor subassembly is mounted on the inner gimbal of a two axis gimbal set that directs the sensor line-of-sight (LOS) to designated earth-fixed locations. An on-gimbal inertial rate sensor provides the 2-degree-of-freedom (2DOF) inertial reference to stabilize the sensor LOS. An off-gimbal GPS-aided inertial navigation system (INS) provides aircraft navigation data to the control system for inertial position stabilization and for determining the target image geolocation. Fine stabilization and step/stare requirement is jointly achieved with two-axis image motion compensation (IMC) mirror mechanisms mounted internally in the telescope optical train. This paper describes the salient features of the TIER II Plus control system design with emphasis on the algorithms used for LOS control, command generation, and target image geolocation. Computer simulation results will be presented to support the design.

Low cost navigation using micro-machined technology

Abstract: Describes the GPS/inertial navigation system (GPSI) integration potential of a low cost inertial measurement unit (IMU) consisting of micro-machined sensors and on board calibration. Two simulated case studies demonstrate the IMU's performance in both flight and automotive navigation. Both studies show that the IMU can be successfully integrated with Kalman filtering into a GPSI system. With complete loss of GPS signals, position accuracy is shown to be less than 10 meters, 2 distance root mean square (drms), after 30 seconds.

Initial calibration and alignment of an inertial navigation

Abstract: This work presents an efficient initial calibration and alignment algorithm for a six-degree of freedom inertial navigation unit. The individual error models for the gyros and accelerometers are presented with a study of its effects in trajectory prediction. A full error model is also presented to determine the sensors needed for full observability of the different perturbation parameters. Finally, dead reckoning experimental results are presented based on the initial alignment and calibration parameters. The results show that the algorithm proposed is able to obtain accurate position and velocity information for a significant period of time using an inertial measurement unit as the only sensor.

Precision guided airdrop system flight test results

Abstract: Airdrop technology is a vital Department of Defense (DoD) capability that supports rapid deployment of war fighters and supplies. Consequently, the Army has sponsored development of gliding, steerable airdrop systems that can be deployed from high altitudes, with large offset, carrying small through large pay loads. The goal was to enable payload delivery within 100 meters of the target. Under this effort, Draper Laboratory developed modular guidance, navigation, and control (GN&C) software to precision guide ram-air parafoils using a combination of Global Positioning System (GPS) and inertial navigation system (INS) data. A high fidelity simulator was constructed to evaluate the expected performance of the Draper software. Also, in conjunction with NASA, flight tests with an 88 sq. ft. parafoil and a 170 pound payload were performed to evaluate the GN&C system performance under real flight conditions. A number of GN&C system design refinements were formulated after review of initial flight test results that ultimately enabled a payload delivery accuracy of about 50 meters. This paper summarizes the motivation for precision guided airdrop systems, reviews the Draper GPS/INS based GN&C for ram-air parafoils, and presents both simulation and flight test results.

Equivalent nonlinear error models of strapdown inertial navigation system

Abstract: The conventional linearized error models of strapdown inertial navigation system( SDINS ) are found not to be effective to represent the nonlinear characteristics of navigation error propagation in case of the system which causes the large navigation errors. To represent the large attitude error of the SDINS, the rotation vector error is introduced and the relationship between the rotation vector error and the quaternion error is derived. Using this relationship the nonlinear error models of the SDINS are presented with the rotation vector error and the quaternion error, respectively. And it is shown that the nonlinear SDINS error models presented here are equivalent to each other. In addition it is shown that in the case of the system with the small enough attitude error, the nonlinear error models can be reduced to the conventional linearized error models.

An application of the extended Kalman filter for integrated navigation in mobile robotics

Abstract: In this paper the problem of integrated navigation for mobile robotics is addressed. The dynamics of ground robots are nonlinear, as well as the measurement devices. For the purposes of position estimation, a dead reckoning problem with a wheeled mobile robot is considered using a gyro and two wheel encoders. The extended Kalman filter (EKF) is used to provide an estimate of vehicle state, gyro error dynamics and variables describing the slip effects. The parameters of the error dynamics have been identified and validated off-line by real data. Simulations results have confirmed the efficacy of the proposed approach, by comparing the performances of the EKF with and without a wheel slip model.

Initial attitude determination and correction of gyro-free INS angular orientation on the basis of GPS linear navigation parameters

Abstract: The exclusion of gyroscopes from navigation system architecture achieves an essential reduction in systems cost. However, the absence of gyroscopes leads to the growth of errors in the determination of navigation system angular orientation. This, in its turn, leads to the growth of errors in the determination of vehicle coordinates. Therefore, one of the main problems in the construction of an integrated navigation system, which is based on a gyro-free inertial navigation system (INS) and a single antenna Global Positioning System (GPS), is the determination of the initial angular orientation and correction of gyro-free INS angular characteristics on the basis of linear navigation parameters (coordinates and velocity) that are obtained from GPS. This paper is devoted to the description of the proposed solution method for this problem.

The effect of earth's gravity on precise, short-term, 3-d free-inertial navigation

Abstract: From the standpoint of physical principles, an inertial navigation system (INS) navigates without sensing the earth's gravitational field, yet this field affects a vehicle's total trajectory, which can be tracked by GPS. Thus, the integration of GPS and INS represents a fusion of dissimilar positioning data. Since the integration is motivated by the aiding capacity of INS during interruptions in GPS positioning, the INS data may require gravitational corrections. In this paper, statistical analyses of 3-D free-inertial navigation show that when decimeter-level accuracy is demanded from the INS over periods as short as 100 s, the gravity field should not be neglected. This conclusion is supported by simulated trajectories at low altitude (< 1000 m above ground) using actual gravity signatures that accumulate decimeter- to meter-level errors in position within 100 s, and several centimeters-per-second velocity error, depending on the strength of the gravity signature.