Showing papers on "Inertial navigation system published in 1999"

The global positioning system and inertial navigation

Abstract: The Science of Navigation. Coordinate Frames and Transformations. Systems Concepts. Discrete Linear and Non-Linear Kalman Filtering Techniques. The Global Positioning System. Inertial Navigation. Navigation Examples and Case Studies. Appendices: A: Notation, Symbols, and Constants. B: Matrix Review.

A high integrity IMU/GPS navigation loop for autonomous land vehicle applications

Abstract: This paper describes the development and implementation of a high integrity navigation system, based on the combined use of the Global Positioning System (GPS) and an inertial measurement unit (IMU), for autonomous land vehicle applications. The paper focuses on the issue of achieving the integrity required of the navigation loop for use in autonomous systems. The paper highlights the detection of possible faults both before and during the fusion process in order to enhance the integrity of the navigation loop. The implementation of this fault detection methodology considers both low frequency faults in the IMU caused by bias in the sensor readings and the misalignment of the unit, and high frequency faults from the GPS receiver caused by multipath errors. The implementation, based on a low-cost, strapdown IMU, aided by either standard or carrier phase GPS technologies, is described. Results of the fusion process are presented.

Hybrid inertial and vision tracking for augmented reality registration

Abstract: The biggest single obstacle to building effective augmented reality (AR) systems is the lack of accurate wide-area sensors for trackers that report the locations and orientations of objects in an environment. Active (sensor-emitter) tracking technologies require powered-device installation. Limiting their use to prepared areas that are relatively free of natural or man-made interference sources. Vision-based systems can use passive landmarks, but they are more computationally demanding and often exhibit erroneous behavior due to occlusion or numerical instability. Inertial sensors are completely passive, requiring no external devices or targets, however, the drift rates in portable strapdown configurations are too great for practical use. In this paper, we present a hybrid approach to AR tracking that integrates inertial and vision-based technologies. We exploit the complementary nature of the two technologies to compensate for the weaknesses in each component. Analysis and experimental results demonstrate this system's effectiveness.

An experiment in autonomous navigation of an underground mining vehicle

Abstract: Describes the theoretical development and experimental evaluation of a navigation system for an autonomous load, haul, and dump truck based on the results obtained during extensive in-situ field trials. The particular contributions of the theoretical work are in designing the navigation system to be able to cope with vehicle slip in rough uneven terrain using information from inertial sensors, odometry, and a bearing only laser. Results are presented using data obtained during the field trials.

Initial calibration and alignment of low‐cost inertial navigation units for land vehicle applications

Abstract: This work presents an efficient initial calibration and alignment algorithm for a 6-degrees of freedom inertial measurement unit (IMU) to be used in land vehicle applications. Error models for the gyros and accelerometers are presented with a study of their perturbation in trajectory prediction. A full inertial 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 obtained with the algorithms presented. The results show that the proposed algorithms provide accurate position and velocity information for an extended period of time using nonaided IMU. ©1999 John Wiley & Sons, Inc.

Inertial navigation system aided by aircraft dynamics

Abstract: In this work the possibility of using the model of aircraft dynamics as a means for aiding an inertial navigation system is studied. The method is of particular interest for low-grade inertial navigating system (INS). The aiding formulation is introduced, its corresponding mathematical model is derived and used in the design of an appropriate extended Kalman filter. Sensitivity analysis of the errors caused by perturbations in the parameters of the aircraft dynamics demonstrates the robustness of the scheme. The importance of maneuvers for observability is also presented. Simulations show that the use of aircraft dynamics for aiding a low-grade inertial navigation system yields a navigation system whose performance is considerably better than that of the pure INS. This improvement is made possible by the fact that the errors in the aircraft dynamics model are observable when performing appropriate calibration maneuvers.

Horizontal directional drilling machine employing inertial navigation control system and method

Abstract: A system and method for controlling an underground boring tool involves the use of one or more of a gyroscope, accelerometer, and magnetometer sensor provided in or proximate the boring tool. The location of the boring tool is detected substantially in real-time. A controller produces a control signal substantially in real-time in response to the detected boring tool location and sensed parameters of a boring tool driving apparatus. The control signal is applied to the driving apparatus to control one or both of a rate and a direction of boring tool movement along the underground path. The gyroscope, accelerometer, and magnetometers may be of a conventional design, but are preferably of a solid-state design. Telemetry data is communicated electromagnetically, optically or capacitively between the navigation sensors at the boring tool and the controller via the drill string or an above-ground tracker unit. The tracker unit may further include a re-calibration unit which communicatively cooperates with the navigation sensors to reestablish a proper heading or orientation of the boring tool if needed. The controller determines a location of the boring tool in at least two of x-, y-, and z-plane coordinates and may also determine an orientation of the boring tool in at least two of yaw, pitch, and roll. A handheld remote unit may be used by an operator to control all or a sub-set of boring system functions.

Sensor fusion based on fuzzy Kalman filtering for autonomous robot vehicle

Abstract: Presents a method of sensor fusion based on adaptive fuzzy Kalman filtering. This method has been applied to fuse position signals from the Global Positioning System (GPS) and inertial navigation system (INS) for autonomous mobile vehicles. The presented method has been validated in a 3-D environment and is of particular importance for guidance, navigation, and control of flying vehicles. The extended Kalman filter (EKF) and the noise characteristic have been modified using a fuzzy logic adaptive system and compared with the performance of the regular EKF. It has been demonstrated that the fuzzy adaptive Kalman filter gives better results (more accurate) than the EKF.

Testing and evaluation of an integrated GPS/INS system for small AUV navigation

Abstract: A Small Autonomous Underwater Vehicle Navigation System (SANS) is being developed at the Naval Postgraduate School. The SANS is an integrated Global Positioning System/Inertial Navigation System (GPS/INS) navigation system composed of low-cost and small-size components. It is designed to demonstrate the feasibility of using a low-cost strap-down inertial measurement unit (IMU) to navigate between intermittent GPS fixes. The present hardware consists of a GPS/DGPS receiver, IMU, compass, water speed sensor, water depth sensor, and a data processing computer. The software is based on a 12-state complementary filter that combines measurement data from all sensors to derive a vehicle position/orientation estimate. This paper describes hardware and software design and testing results of the SANS. It is shown that results from tilt table testing and bench testing provide an effective means for tuning filter gains. Ground vehicle testing verifies the overall functioning of the SANS and exhibits an encouraging degree of accuracy.

Development of a nonlinear psi-angle model for large misalignment errors and its application in INS alignment and calibration

Abstract: This work presents a general nonlinear psi-angle approach that does not require coarse alignment. In this psi-angle model, the three misalignment angles are assumed all large. Three states are used to describe three psi-angles rather than the four used in previous works. The approach is identical to the standard small error methods when the process errors diminish to small angles. The position and velocity error models are also presented. Standard extended Kalman filter techniques are used to solve the nonlinear data fusion problem. Experimental results of in-flight inertial navigation systems (INS) alignment and calibration are presented considering total uncertainty in azimuth orientation using a low cost inertial measurement unit aided with a differential global positioning system.

Cyclops: miniature robotic reconnaissance system

Abstract: Miniature mobile robots are desirable for military applications because of their ability to function covertly in highly constrained environments. However, work on such tiny robotic systems has been hampered by the difficulty of packaging locomotion, sensing, computing and power subsystems into diminutive spaces. This paper presents the design and initial prototype of a miniature mobile robot designed to carry out surveillance and reconnaissance missions in an urban environment. This initial prototype is spherical in shape, with a diameter of 5.5 inches, and weighs only 4.5 pounds. A novel inertial steering system, along with the robot's robust control and communication systems, make it useful for covert video surveillance and reconnaissance in tightly constrained spaces.

Integrated Navigation and Guidance Systems

Abstract: Principles of Navigation and the Concept of an Integrated Navigation System Newton's Laws Applied to Navigation (Geodesics, Basic Reference Frames, Simplified Aerospace Vehicle Equation) Inertial Navigation Systems (INS) and Global Positioning System (GPS) Uncertainty in Navigation, INS Error Propagation, Probabilities, Autocorrelation and the Method of Least Squares Kalman Filters and Their Key Role in the Integration of Aircraft Avionics Systems GPS Theory and its Application to Navigation (Including System Accuracy) GPS Application to Precision Approach and Landing, Attitude Control and Air Traffic Control Flight Testing of Navigation Systems Computer Exercises.

Method and apparatus for borehole surveying

Abstract: The invention is, in its various aspects, a method and apparatus useful for strapdown inertial navigation and surveying in a borehole. The method comprises maneuvering a probe including three vibrating mass, Coriolis effect gyroscopes in a borehole and initializing the probe's attitude in the borehole within the probe's frame of reference. Three orthogonal, incremental rotation angles and three orthogonal, incremental velocities are determined for the probe within the probe's frame of reference. The incremental rotation angles are determined from the gyroscopes. The method then translates the three incremental velocities from the probe's frame of reference into the inertial frame of reference using the three incremental rotation angles. Next, a velocity vector in a local-vertical, wander-azimuth frame of reference is determined from the translated incremental velocities. A velocity error observation is then obtained. A system error is then estimated from the velocity vector and the velocity error observation. The system error is then fed back into the inertial navigation system for use in refining the method. In as second aspect, the invention is a strapdown, inertial measurement unit. The inertial measurement unit includes a housing, three accelerometers, and three vibrating mass, Coriolis effect gyroscopes. The three accelerometers are mounted within the housing. The three vibrating mass, Coriolis effect are rigidly mounted within the housing.

Positioning process and system thereof

Abstract: A positioning method and a system are disclosed for measuring a position of a vehicle on land, air, and space, using measurements from a global positioning system receiver and an inertial measurement unit. In the present invention, an integrated Kalman filter processes the all-available measurements of the global positioning system: pseudorange, delta range, carrier phase, and the solution of an inertial navigation system. The integrated Kalman filter is a multi-mode, robust kalman filter, in which optimal integrated mode is selected based on the measurement availability and filter stability. The high accurate solution of the inertial navigation system, which is corrected by the Kalman filter, is used to aid on-the-fly resolution of the carrier phase integer ambiguity of global positioning system in order to incorporate the carrier phase measurements into the Kalman filter, and to aid the carrier phase and code tracking loops of the receiver of the global positioning system to improve the receiver jamming and high dynamic resistance.

Direct exterior orientation of airborne imagery with gps/ins system: performance analysis.

Abstract: Integrating the Global Positioning System (GPS) with an Inertial Navigation System (INS) allows for direct image georeferencing, offering a possibility of relaxing the demand for aerial triangulation (AT) in airborne surveying/mapping. The performance of the prototype of the Airborne Integrated Mapping System (AIMS™), based on GPS/INS/CCD (charge-coupled device) integration, developed by The Ohio State University Center for Mapping, is investigated in this paper. A brief description of the essential features of the integrated system and its practical implementation is presented. The performance of AIMS™ is primarily assessed based on the photogrammetric processing of 1:6,000 large-scale aerial imagery considered as a truth reference. An accuracy analysis and discussion of the impact of direct orientation and the multi-sensor system calibration on the photogrammetric data extraction process are also addressed.

Inertially augmented GPS landing system

Abstract: An airplane precision approach guidance system and method. The airplane precision approach guidance system includes: (i) GPS landing system (GLS) components ( 12 ) for receiving and processing signals from GPS satellites ( 30 ) and a GPS ground station ( 32 ) and generating a first set of velocities; (ii) an inertial reference system (IRS)( 20 ) for generating a second set of velocities; and (iii) guidance software ( 24 ) for generating a cross-runway velocity and a lateral distance from runway centerline based on received runway centerline information and the generated first and second set of velocities. The airplane precision approach guidance system also includes flight instruments ( 26 ) and an autopilot system ( 28 ) for receiving and processing the information produced by the guidance software. The guidance software may be executed by a conventional airplane processor, such as the GLS processor, the IRS processor or the airplane's autopilot processor, or by a separate stand-alone processor. The runway centerline information may be stored at the ground station or in local memory. The ground station can also provide differential GPS information. In airplanes that include redundant systems, voting is used to determine which IRS supplies the second set of velocities.

Full fusion positioning method for vehicle

Abstract: A full fusion positioning method, which can be implemented in the existing hardware, but is more amenable to the emerging wafer-scale integration hardware, comprises the steps of injecting a global positioning system signal received by a global positioning system antenna and a predicted pseudorange and delta range from a data fusion, and converting and tracking said global positioning system signal to obtain pseudorange and delta range measurement and errors of said pseudorange and delta range measurement, which are passed to said data fusion; receiving a vehicle angular rate and an acceleration signal/data from an inertial measurement unit and solving inertial navigation equations for obtaining a referencing navigation solution, including position, velocity, and attitude, which are passed to a data fusion; and fusing said pseudorange and delta range measurement and said errors of said pseudorange and delta range measurement of said global positioning system and said referencing navigation solution to obtain predicted pseudorange and delta range, optimal estimates of said referencing navigation solution errors and inertial sensor errors, and optimal position information.

Inertial navigation for the urban warrior

Abstract: Individual soldier geolocation in situations such as urban warfare where loss of Global Positioning System (GPS) track can impact mission success has become a critical problem. Concepts such as RF 'time difference of arrival' and 'dead reckoning' techniques have not demonstrated their ability to support navigation reliably inside buildings on their own. Inertial navigation is the only technology that operates independence of external assets. The advent of micromechanical inertial sensor technology has resulting low-cost, very small, low-power navigation system capable of fitting in a soldier's boot. A miniature navigator consisting of three micromechanical gyroscope and accelerometer packages, including supporting application- specific integrated circuit chips, and capable of operating in support of such a mission has been developed. However, because of accelerometer and gyroscope drift, navigating inertially over long time periods using even the most precise and most expensive inertial senor available today remains close to impossible. Inertial augmentation techniques are therefore required, and the concept of personal inertial navigation systems aided by zero velocity updating of the accelerometers with each footfall has been examined and shown to be sufficient to determine the location of an individual soldier accurately within a large building complex after hours of operation. In addition to the accelerometer, updates of the gyro via zero attitude rate techniques is an additional means to further enhance the position accuracy, as well as to provide an attitude reference in support of soldier carried targeting sensors.

Agricultural Vehicle Navigation Using Multiple Guidance Sensors

Abstract: Agricultural vehicle navigation includes both on-road and on-field operations. The objective for on-road navigation is to guide the vehicle traveling on paved or prepared road according to a scheduled path plan, and for on-field guidance is to guide the vehicle following crop rows without overrun on crops. In this paper, the authors have presented an on-field navigation system with redundant sensors of a vision sensor, a fiber optic gyroscope (FOG), and RTK GPS. A steering controller has been developed to implement steering control based on guidance information obtained from guidance sensors. The navigation system has evaluated on an agricultural vehicle. A research platform has been developed based on a Case-IH Magnum 8920 2-wheel drive agricultural tractor. Results indicated that the multiple sensor based agricultural vehicle navigation system was capable of guiding the tractor traveling between crop rows accurately.

Method and system for estimation and correction of angle-of-attack and sideslip angle from acceleration measurements

Abstract: A method and system is disclosed for using inertial sensors in an Inertial Navigation System (INS) to obtain analytic estimates of angle-of-attack ( α ) and sideslip angle ( α ). The inertial sensors consist of one or more accelerometers which produce the estimated signals for angle-of-attack ( α ) and sideslip angle ( β ). Three methods are shown for obtaining α and β estimates from INS information and are programmed into a nonlinear simulation of a relaxed stability aircraft requiring a high level of artificial stability augmentation in its flight control system. Simulation results from the nonlinear simulation for each of the three methods were compared with the results obtained when conventional probes were used to obtain direct measurements of α and β . Based on these comparisons, a method for determining α and β analytically which estimates the turbulence level in each axis is combined with one of the three methods to provide derived inertial values for providing control system feedback to an aircraft.

Detection and Filtering of Short‐Term (1 /fγ) Noise in Inertial Sensors

Abstract: Systematic and random errors inherently present in all inertial sensors contribute to the long-term divergence of the navigation solution of an Inertial Navigation System (INS). To keep such long-term divergence under control while taking advantage of their excellent short-term performance, an INS is often combined with information from other navigation aids. However, the improvements due to external aiding are limited by the type, accuracy and update period of the information provided by the aid(s). In the case where an INS is aided by GPS, only the long-term inertial errors are suppressed while the short-term inertial errors essentially remain unaffected. A better navigation solution can therefore be expected if most of the short-term inertial sensor noise is reduced prior to data integration. This paper describes a method of inertial data pre-filtering over the frequency band of interest, i.e. between the measurement period of external aiding with GPS and the edge of the motion band. A model for the short-term inertial errors in this band is introduced as a combination of a broad band signal with noise possessing self-similarities over several decades of frequency. The model is defined in the frequency and wavelet domains. A technique for adaptive estimation of the model parameters is introduced. This method is based on an analysis of a short portion of data above the band of interest. Once the model parameters are estimated for a specific system and time-period, the noise distribution is predicted within the band of interest and the signals are de-noised. This filtering methodology is tested using different navigation-grade strapdown inertial systems and the results are presented. A 20% improvement in the attitude determination has been observed under the dynamic conditions with respect to an independent reference.

A comparison and analysis of airborne gravimetry results from two strapdown inertial/DGPS systems

Abstract: In September 1996 the University of Calgary tested a combination of strapdown inertial navigation systems and differential global positioning system (DGPS) receivers for their suitability to determine gravity at aircraft flying altitudes. The purpose of this test was to investigate the long-term accuracy and repeatability of the system, as well as its potential for geoid and vertical gradient of gravity determination. The test took place during a 3-day period in the Canadian Rocky Mountains over a single 100 × 100 km area which was flown with 10-km line spacing. Two flights were done at 4350 m in E–W and N–S profile directions, respectively, and one at 7300 m with E–W profiles. Two strapdown inertial systems, the Honeywell LASEREF III and the Litton-101 Flagship, were flown side by side. Comparison of the system estimates with an upward-continued reference showed root-mean-square (RMS) agreement at the level of 3.5 mGal for 90- and 120-s filter lengths. The LASEREF III, however, performed significantly better than the Litton 101 for shorter filtering periods of 30 and 60 s. A comparison between the two systems results in an RMS agreement of 2.8 and 2.3 mGal for the 90- and 120-s filters. The better agreement between the two systems is mainly due to the fact that the upward-continued reference has not been filtered identically to the system gravity disturbance estimates. Additional low-frequency differences seem to point to an error in the upward-continued reference. Finally, an analysis of crossover points between flight days for the LASEREF III shows a standard deviation of 1.6 mGal, which is near the noise level of the INS and GPS data. Further improvements to the system are possible, and some ideas for future work are briefly presented.

Results of airborne vector (3-d) gravimetry

Abstract: Gravity field modeling using airborne vertical component gravimetry has made significant strides over the last decade. We demonstrate the feasibility of extending this to three-dimensions using data from inertial navigation systems (INS) and the Global Positioning System (GPS). A significant advantage of measuring the horizontal gravity components is that the geoid can be determined in profiles by direct along-track integration, thus not only adding strength to conventional methods, but reducing the required area of survey support, especially along model boundaries. As such, the ultimate limitation of the method is in the quality of the INS and GPS sensors. In our test case, all three components of the gravity vector were determined over a profile in the Canadian Rocky Mountains. Differences between available truth data and the computed gravity components have standard deviations of 7–8 mGal (horizontal) and 3 mGal (vertical). These standard deviations include uncertainties in the truth data (<5 mGal, for horizontal; 1.3 mGal, for vertical). The resolution in the computed values is about 10 km. These analyses have demonstrated for the first time that the total gravity vector can be determined from airborne INS and GPS to reasonable accuracy and resolution, without any external orientation information, nor prior statistical hypothesis on the gravity signature, using medium-accuracy INS and geodetic quality GPS receivers.

Integrated vision/inertial navigation system design using nonlinear filtering

Abstract: Addresses the problem of navigation system design for autonomous aircraft landing. New nonlinear filter structures are introduced to estimate the position of an aircraft with respect to a possibly moving landing site, such as a naval vessel, based on measurements provided by airborne vision and inertial sensors. By exploring the geometry of the navigation problem, the navigation filter dynamics are cast in the framework of linear parametrically varying systems (LPVs). Using this set-up, filter performance and stability are studied in an H/sub /spl infin// setting by resorting to the theory of linear matrix inequalities (LMIs). The design of nonlinear, globally stable filters to meet adequate H/sub /spl infin// performance measures is thus converted into that of determining the feasibility of a related set of LMIs and finding a solution to them, if it exists. This is done by resorting to widely available numerical tools that borrow from convex optimization techniques. The paper develops the mathematical framework that is required for integrated vision/inertial navigation system design and details a design example for an air vehicle landing on an aircraft carrier.

Wake turbulence warning and caution system and method

Abstract: A wake turbulence warning and caution system and method for a protected aircraft tracks and stores a trajectory of a wake trailing behind a nearby aircraft and adjusts the wake position for the effect of local wind velocity, and then calculates a distance and time to closure between the protected aircraft and the wake. A caution is annunciated aurally and/or on a navigation map display and/or on a primary flight display if the distance or time to closure is less than a first predetermined threshold, and a warning is annunciated if the distance or time to closure is less than a second predetermined threshold. The wake trajectory is calculated based on range, bearing, and altitude information about the nearby aircraft supplied by a Traffic Collision Avoidance System (TCAS) aboard the protected aircraft, and based on inertial position and attitude of the protected aircraft supplied by an inertial reference system (IRS). Local wind velocity is calculated based on the aircraft inertial velocity from the IRS, true air speed from an air data computer (ADC), and angle of attack and sideslip angles provided by sensors aboard the aircraft. Wake tracking, wind velocity calculations, and caution and warning functions can be implemented in software within a TCAS computer and/or a flight management system aboard the protected aircraft.

Inertial-Aided Cycle-Slip Detection/Correction for Precise, Long-Baseline Kinematic GPS

Abstract: Recent techniques for long-range kinematic differential GPS positioning using the carrier phase make it possible to maintain sub-decimeter precision over many hours of trajectory determination, at a thousand kilometers from all reference receivers. An Inertial Navigation System (INS), combined with GPS, extends the usefulness of the long-range technique to find position at higher rates than with GPS alone, and helps fill in gaps in the GPS solution. Also, as shown in this paper, even a moderately accurate (and low-price) small, lightweight, and portable INS can substantially enhance the ability to detect and correct GPS phase measurement cycle slips. In the near future, inertial units are expected to become more precise and also less expensive than the one used for this test.

Sensors Used for Autonomous Navigation

Abstract: Navigation and guidance are defined as the processes of determining and controlling the position of a vehicle. An autonomous system will have to include these two basic procedures to perform any useful task. The information generally required for navigation is the direction, speed, and position of the vehicle. The basic navigation techniques were designed several years ago to navigate vessels across the ocean. In the past the position of ships was estimated with dead reckoning techniques using speed and heading observations. With this information the trajectory of the ship was predicted with errors that accumulated over time. The heading information was obtained with the position of the sun or other stars and the velocity was evaluated with a log compensating for the effect of local currents. Absolute information was also used to correct the position estimation. These fixes were done when well-known natural landmarks were recognised. The Mediterranean was the testing place of all these techniques. It was appropriate since the water currents are light in most places and many natural landmarks can be seen along most possible journeys.