Showing papers on "Inertial measurement unit 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.

Electronics for micromachined inertial sensors

Abstract: Capacitive interface circuits for micromachined sensors are described The focus is on the position sense electronics for accelerometers and gyroscopes Special attention is given to the characteristics of the interface between the sensor and electronic circuits, and on practical and fundamental noise mechanisms that limit the achievable resolution

Attitude determination utilizing an inertial measurement unit and a plurality of satellite transmitters

Abstract: The invention is a method for obtaining observables for input to a Kalman filter process which determines the attitude (roll, pitch, and heading) of a platform. The invention utilizes an inertial measurement unit (IMU) attached to the platform and an associated processor, a plurality of signal receiving antennas attached to the platform, and a plurality of satellite transmitters. The heading of the platform as determined by the IMU and its associated processor by themselves can be significantly in error. A comparison of the values of an attitude-sensitive function of the ranges from the platform antennas to different groupings of satellite transmitters obtained first by using IMU data and second by using the measured phases of the satellite-transmitter signals received at the platform antennas, a very accurate value for the range function is obtained. This accurate value of the range function is used in a Kalman filter process to obtain very accurate values for platform attitude.

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.

Investigation of a Low-Cost and High-Accuracy GPS/IMU System

Abstract: A low-cost, high-accuracy integrated Global Positioning System (GPS)/inertial measurement unit (IMU) system is investigated. Several issues for the design and implementation of this cm-level GPS/IMU system are discussed, including the algorithms of inertial position and attitude computation, the mathematical model of the Kalman filter, the method of IMU feedback error calibration, and the technique of the GPS On-The-Fly ambiguity resolution. The performance of the integrated GP!YIMU system is evaluated using data collected during the field tests.

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.

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.

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.

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.

Gps-aided navigation system requirements for smart munitions and guided missiles

Abstract: The Global Positioning System (GPS) is finding increasing use as an effective means of improving accuracy of Inertial Navigation Systems (INS) carried on board guided projectile and missile systems. Two warfare areas that have provided strong motivation for using integrated GPS/INS are Naval Surface Fire Support (NSFS) and Tactical Ballistic Missile Defense (TBMD). This paper presents an overview of various techniques for the integration of the GPS and the INS in a guided weapon system. Then the development of a multi-purpose GPS/INS simulation and analysis tool is described. The model was developed with the flexibility to support a variety of possible technology demonstration and full scale development programs involving GPS-aided guided weapons. The simulation includes detailed models of the GPS satellites and receiver, jamming environment, navigation Kalman filter, inertial navigation system with strapdown inertial measurement unit, six degree-of-freedom airframe and guidance and control components. To illustrate navigation capability, the performance of a GPS-aided smart munition is analyzed in detail. A review of some emerging technology trends and potential future applications for GPS/INS is also provided.

Integration of inertial information with vision towards robot autonomy

Abstract: Reconstructing 3D data from images becomes harder if the goal is to recover the dynamics of the 3D world from the image flow However, it is known that humans integrate and combine the information from different sensorial systems to perceive the world For example, the human vision system has close links with the vestibular system to perform everyday tasks A computational approach for sensorial data integration, inertial and vision, is presented for a mobile robot equipped with an active vision system and inertial sensors The inertial information is a different sensorial modality and, in this article, we explain our initial steps to combine this information with other sensorial systems, namely vision Some of the benefits of using inertial information for navigation and dynamic visual processing are described in the article During the development of these studies a low-cost inertial system prototype was developed A brief description of low-cost inertial sensors and their integration in an inertial system prototype is also described The set of sensors used in the prototype include three piezoelectric vibrating gyroscopes, a tri-axial capacitive accelerometer and a dual axis clinometer As a first approach the clinometer is used to track the camera's pan and tilt, relative to a plane normal to the gravity vector and parallel to the ground floor This provides the orientation data that, combined with a process of visual fixation, enables the identification of the ground plane or others parallel to it An algorithm that segments the image, identifying the floor along which the vehicle can move is thus obtained

GPS/INS Technology Trends for Military Systems

Abstract: This paper will focus on the technology trends for inertial sensors, GPS accuracies, and integrated GPS/INS systems, including considerations of jamming, for military platforms and weapons, that will lead to one meter accuracy, global, navigation systems of the future. For inertial sensors, trend-setting sensor technologies applicable to military systems will be described. They are: fiber-optic gyros, silicon micromechanical gyros, resonating beam accelerometers, and silicon micromechanical accelerometers. A vision of the inertial sensor instrument field, and inertial systems for military applications for the next few decades will be given. GPS specified and observed current accuracies will be described, as well as, planned accuracy improvements due to various stages of the WAGE implementation, intersatellite ranging, and "all-in-view" tracking. Uses of relative and differential GPS will be discussed. The trend towards tightlycoupled GPS/INS, where both code and carrier tracking loops are aided with inertial sensor information, will be described and the synergistic benefits explored. Some examples of the effects of jamming will be described and expected technology trends to improve system antijam capability will be presented.

Three-axis inertial attitude determination for spinning spacecraft

Abstract: A system and method for determining the attitude in an inertial frame of a spacecraft spinning about an axis in a body frame including determining momentum vector direction in the inertial frame; determining momentum vector direction in the body frame; acquiring information from an at least single-axis sensor; obtaining reference information on the at least single-axis sensor; updating the attitude in the inertial reference frame using the momentum vector direction in the inertial frame, the momentum vector direction in the body frame, the output of the at least single-axis sensor, and the reference information on the at least single-axis sensor; and propagating the attitude using data from one or more inertial sensors.

Airborne imaging system

Abstract: A remote data collection system, which may be used in a vehicle such as an aircraft or a ground vehicle, includes a directional sensor, such as one or more cameras, for sensing a characteristic of interest and providing sensor data. The system further includes a global positioning system (GPS) receiver for providing GPS data representative of the position of the sensor, an inertial measurement unit (IMU) for providing IMU data representative of the attitude of the sensor, a processing unit and a storage unit. The processing unit determines geographic data referenced to the sensor data in response to the GPS data and the IMU data. The processing unit may utilize an error model to determine IMU errors which may be used in determining the geographic data with high accuracy. The sensor data and the geographic data are stored in the data storage unit for subsequent use. The system may include a stabilized platform on which the sensor and the IMU are mounted. The stabilized platform is rotated about at least one axis of rotation to control the sensing direction of the sensor as the vehicle moves.

Inertial navigation-past, present, and future

Abstract: The author describes the principles of inertial navigation (IN) at a level needed to understand the significance of the current and future trends. IN is simply a form of `dead reckoning'. A `gimballed platform' which can measure an aircraft's position, velocity, acceleration, attitude, and heading is examined. (9 pages)

A GPS Carrier Phase Processor for Real-Time High Dynamics Tracking

Abstract: error budgets on navigation. Validation is both challenging and expensive. While existing carrier phase RTK truth systems are capable of decimeter performance, they fail in realistic high dynamics maneuvers with blockages. In order to achieve robust carrier phase tracking aboard range test pods and other vehicles, a powerful adaptive filter structure was developed for enhancing phase tracking functions of existing and future receivers. The technique optimally processes raw correlator data obtained prior to receiver tracking loops. Test pod blockage and dynamics models were developed and used to analyze reception profiles recorded in actual aircraft flight tests. These profiles were used to drive a 200 Hz model of the GPS receiver’s correlator bank and IMU, permitting closed loop simulation of the enhanced tracking functions. Phase navigation simulations were carried out with single and multiple antennas, with and without IMU, in figure-8 dive, and aileron roll maneuvers, to 18 g’s. The optimal combining of dual antennas mitigated satellite block- ages. Stability of the tightly coupled GPS/IMU integration was demonstrated.

System Identification of an Autonomous Aircraft using GPS

Abstract: Stanford University’s GPS Laboratory has developed and demonstrated a fully autonomous, small, unmanned airplane. Recent flight tests of the airplane have been extended to collect appropriate open-loop data to perform system identification. In previous research in the GPS Lab, the autonomous airplane, utilizing Carrier-Phase Differential GPS (CDGPS), has flown several flights of a predetermined trajectory from take-off to landing. GPS, providing position, velocity, attitude, and attitude rate, was the primary sensor for the automatic controller. No inertial sensors were used during the autonomous flights. The only additional sensors for these previous flights were indicators for wind speed and direction. Carrier Phase Differential GPS was the enabling technology for the autonomous control. In earlier flight tests, the low noise, high bandwidth, precise positioning allowed the controller to function well with full sensor feedback. In fact, sensor performance was accurate enough to allow the controller to perform well even without an elaborate mathematical system model of the aircraft. Previous flight tests demonstrated a total system error of typically less than 0.5 m. The same low noise, high bandwidth qualities of the GPS position and attitude system make it ideal for system identification. The multiple vehicle state information is collected and used to generate a mathematical model of the airplane. During the recent flight tests, the control surfaces are systematically disturbed to observe the aircraft modes. Several different modeling techniques are applied to the same data and results are compared. Standard aircraft modeling techniques using parameter identification and a priori knowledge of linearized dynamics are compared to techniques assuming no a priori information.

GPS attitude system integrated with an inertial system for space applications

Abstract: The integration of a GPS attitude determination system with an inertial navigation system is discussed. A demonstration was performed showing the benefits of GPS attitude aiding of an inertial system. This demonstration was done in part to support the NASA study investigating a common GPS/INS concept for space applications. The study led to a full development program of this common architecture for Space Shuttle, Space Station and the Crew Return Vehicle.

Comparison of inertial navigation system error models in application to imu transfer alignment

Abstract: ,This paper compares IMU transfer alignment results from using different INS system error model forms for a local level wander azimuth system. Actual recorded test data is processed by Kalman filter implementations of three INS error dynamic models. These three INS error model forms are obtained by using velocity error representations referred to as either computer frame or perturbation forms. For the computer frame form, two variations of that form are obtained from either of the assumptions - the local vertical axis tilt error, $z, is zero, or the navigation frame vertical axis misalignment, 66z, is zero. The perturbation form assumes the local vertical axis tilt error, 2 = 0 , and perturbation model results are similar for estimating the body referenced misalignment between the IMU and the aircraft's reference navigation system; and 3) the computer frame model, with ddt = 0 , produces results that more accurately reflect navigation system errors during aircraft maneuvers.

C-MIGITS™ II Design and Performance

Abstract: Numerous applications can benefit from use of integrated INS/GPS technology. For several years, Boeing Autonetics has been developing a family of integrated Inertial Navigation System/Global Positioning System (INS/GPS) products, Miniature Integrated GPS/INS Tactical System (MIGITSa), for off-the-shelf employment by various applications that require good performance at a low cost. This paper describes the most recent, coarse/acquisition (C/A) code, MIGITSa product: C-MIGITSa II. First, the product architecture and overall design approach are presented. The C-MIGITSa II design is then discussed in more detail, along with key performance parameters. C-MIGITSa II was developed for applications that place a strong premium on small size and low cost, and can either tolerate C/A code accuracy or can employ differential corrections. It uses the Boeing solid state digital quartz inertial measurement unit (DQI IMU) in conjunction with a Rockwell 5-channel MicroTrackera low power (LP) commercial GPS engine. These are packaged in a small hermetic enclosure. The product features small size (54 cubic inches) and low weight (2.4 pounds). A tightly coupled navigation mechanization combines the raw IMU and GPS outputs in a single Kalman filter. C-MIGITSa II represents a low-cost, in-production, commercial off-the-shelf, nondevelopmental-item (COTS/NDI) product that can be beneficially employed in a variety of commercial and military applications.

Camera guide system

Abstract: The invention concerns a camera guide system using a GNSS (Global Navigation Satellite System) receiver, an inertial measurement unit, and other sensors for determining the position and the layout of the objects and in particular of the targets to be filmed.

Inertial navigation system of marine vessel

Abstract: PROBLEM TO BE SOLVED: To avoid unnecessary error correction and magnification of error due to measuring noise or the like by forbidding error correction of an accelerometer and a gyro, concerning a movement pattern of a hull. SOLUTION: When a hull moves, the movement pattern has different influence upon the errors of a gyro and an accelometer of an IMU part 11 which are fixed to the reference axis of the hull. An IMU performance improvement judging part 43 estimates the movement pattern of the hull, according to acceleration outputted from an acceleration coordinate conversion calculating part 23 and velocity and position outputted from a velocity position calculating part 26, and operates the degree of influence upon errors of the accelerometer and the gyro. When the degree is at least a specified value, an IMU error estimation operating part 32 corrects the gyro error and the accelerometer error. On the contrary, when the degree of influence of the movement pattern is at least a specified value, the correction of the gyro error and the accelerometer error is forbidden. Thereby error magnification after correction which is to be caused by measuring noise or the like can be avoided.

Digital Quartz IMU - Navigation Processor (DQI-NP) Design and Performance

Abstract: BIOGRAPHY Mike Martin is Inertial Navigation System/Global Positioning System (INS/GPS) project manager for Boeing Guidance, Navigation, and Sensors. Previously, he was technical director for the Joint Product Development Team, which developed the MIGITS™ family of INS/GPS products. In his thirteen years with this organization, he has held a number of engineering management positions, primarily in the areas of advanced systems engineering and analysis. Prior to joining Boeing, he was a project engineer at The Aerospace Corporation and a product planner at Ford Motor Company. He is a graduate of the Massachusetts Institute of Technology, where he received B. Bruce Detterich holds BS and MS degrees in engineering from Loyola University in Los Angeles. He has worked at Autonetics, now known as Boeing Guidance, Navigation, and Sensors, for 32 years. His first experience with GPS was in the late 1970's in an experiment which flew a Texas Instruments receiver in a Minuteman Missile. That project successfully acquired and tracked the only SVs available at the time from in-silo launch through reentry vehicle deployment. Since then he has held positions as a lead or chief system engineer on the Peacekeeper (MX) and Small ICBM Guidance and Control development programs. He has been involved in all phases of a system's life cycle, from experimental component development through operational deployment and support. He is presently involved in a variety of programs as a Principal Engineering Specialist, but primarily participates in the development and application of Autonetics' Miniature Integrated GPS/INS Tactical System (MIGITS™), and low-cost IMUs. He is a member of the IEEE and belongs to the Communications, Signal Processing, and Antennas and Propagation Societies. ABSTRACT A wide variety of applications can benefit from integrated Inertial Navigation System/Global Positioning System (INS/GPS) technology. However, in many situations the end user has a preference for a specific GPS receiver. Additionally, in most cases, the user does not desire to expend the time and money necessary to perform a custom INS/GPS integration, but instead wants a low cost off-the-shelf solution. To address these applications, Boeing has developed the Digital Quartz IMU-Navigation Processor (DQI-NP) product as an extension of its Miniature Integrated GPS/INS Tactical System (MIGITS™) family of integrated INS/GPS products. This paper describes the DQI-NP product architecture, overall design approach, and development history. DQI-NP development is complete, and the product is currently in low rate production. The DQI-NP design is described in more detail, along with key performance …

Rotational Motion Measurement by Integrating Gyroscopes and Accelerometers

Abstract: In recent years, the researches for conducting the human motion capture and recognition are prosperously carried out in the field of man-machine interface, sign-language recognition, dancing behavior description and so force. Image processing techniques and magnetic sensing devices are widely used, but the former exhibits some disadvantages due to occlusion and the latter shows some problems in the spatial measurable range. Therefore, the authors are proposing the measurement and processing techniques for dynamically estimating the human behaviors, especially the behaviors of rotary joint type link structures of upper arm motion by performing the integrated type sensor fusion using the gyroscopes and accelerometers having such special features that are free from the occlusion and are not influenced by the external magnetic fields environment. This paper proposes a new measurement system which recognizes motion of human arms directly and precisely by the fusion of gyroscopic sensor and accelerometric sensor. That is, the objective of this system is the emphasis of the merits of both types of sensor and the removal of their demerits by unification of both sensors. Experimental results using 1-joint and 1-axis arm show that the performance of this sensing system is acceptable within the range of human being's general behaviors, and the effectiveness of this method in application for human motion capture has been verified through the simulation using 2-joint and 2-axis human arm model.

Draper Laboratory small autonomous aerial vehicle

Abstract: The Charles Stark Draper Laboratory, Inc. and students from Massachusetts Institute of Technology and Boston University have cooperated to develop an autonomous aerial vehicle that won the 1996 International Aerial Robotics Competition. This paper describes the approach, system architecture and subsystem designs for the entry. Thisentry represents a combination of many technology areas: navigation, guidance, control, vision processing, humanfactors, packaging, power, real-time software, and others. The aerial vehicle, an autonomous helicopter, performs navigation and control functions using multiple sensors: differential GPS, inertial measurement unit, sonar altimeter, and a flux compass. The aerial transmits video imagery to the ground. A ground based vision processor convertsthe image data into target position and classification estimates. The system was designed, built, and flown in lessthan one year and has provided many lessons about autonomous vehicle systems, several of which are discussed. Inan appendix, our current research in augmenting the navigation system with vision-based estimates is presented.Keywords: Autonomous helicopter, robot contest, vision-based navigation

Analysis, experimental evaluation, and software upgrade for attitude estimation by the Shallow-Water AUV Navigation System (SANS)

Abstract: : The main problem addressed by this research is the lack of a small, low-cost integrated navigation system to accurately determine the position of an Autonomous Underwater Vehicle (AUV) during all phases of an underwater search or mapping mission. The approach taken utilized an evolving prototype, called the Shallow-Water AUV Navigation System (SANS), combining Global Positioning System (GPS), Inertial Measurement Unit (IMU), water speed, and magnetic heading information using Kalman, low-pass, and complimentary filtering techniques. In previous work, addition of a math coprocessor improved system update rate from 7 to 18 Hz, but revealed input/output coordination weaknesses in the software. The central focus of this thesis is on testing and programming improvements which resulted in reliable integrated operations and an increased processing speed of 40 Hz. This now allows the filter to perform in real time. A standardized tilt table evaluation and calibration procedure for the navigation filter also was developed. The system was evaluated in dynamic tilt table experiments. Test results and qualitative error estimates using differential GPS suggest that submerged navigation with SANS for a period of several minutes will result in position estimation errors typically on the order of 10 meters rms, even in the presence of substantial ocean currents.