Showing papers on "Inertial measurement unit published in 1994"

Gyroscope Free Strapdown Inertial Measurement Unit by Six Linear Accelerometers

Abstract: A six-accelerome ter configuration is presented to compute the rotationa^ and translational acceleration of a rigid body. This theoretical minimum accelerometer configuration has as stable a mechanization equation as that of recent results of nine-accelero meter schemes. Associated equations/that can be used to work with the accelerometer location and orientation errors are also derived. For navigation application, the novel design can be integrated with other sensors of complementary characteristics to enhance the performance.

Modern Inertial and Satellite Navigation Systems

Abstract: : Every mobile robot needs to know where it is so everyone who does mobile robotics wants to know how inertial and satellite navigation works. These two technologies are the most sophisticated forms of navigation systems available and they complement each other very well. Applications requiring indications of highly dynamic 3D motion, excellent relative accuracy and high update rates benefit from inertial systems. Applications requiring bounded absolute accuracy for extended excursions or position estimates relative to the earth itself benefit from satellite navigation. This decade has seen the development of inexpensive handheld global positioning systems based on reception of the GPS satellite signals, and advances in optical gyroscopes and integrated circuit accelerometers which promise to put an inertial navigation system in every automobile before the end of the next. This report is a detailed tutorial which explains the principles, practice, and issues of using these new technologies.

High accuracy navigation and landing system using GPS/IMU system integration

Abstract: In this paper, the accuracy, integrity and continuity of function requirements for automatic landing systems using satellite navigation systems are discussed. Such a landing system is the integrated navigation and landing system (INLS) developed by Deutsche Aerospace (DASA/Ulm, Germany). The system concepts of the INLS are presented. It is shown how an INLS, based on system integration of a satellite navigation system (e.g., GPS) in realtime differential mode with an inertial measurement unit (IMU) in the accuracy class of an attitude and heading reference system (AHRS), can meet the requirements: the results given are mainly devoted to the accuracy issues. Using Kalman filter techniques, an in-flight calibration of the IMU is performed. The advantage of system integration, especially in dynamic flight conditions and during phases of flight with satellite masking, is explained. The accuracy, integrity and continuity of function of the INLS were proven by means of flight tests in a commuter aircraft using a laser tracker as a reference. These flight tests have shown that the short-term accuracy ( >

Aided Inertial LAnd NAvigation system (ILANA) with a minimum set of inertial sensors

Abstract: This article summarises the activities of Honeywell Sondertechnik in Maintal Germany in the development and prototyping of a new low cost land navigation system (ILANA) with a minimum amount of inertial sensors. The system utilises one GG1308 ring-laser-gyro, two vibrating beam accelerometers RBA500 and a hodometer. To aid the system, a Global Positioning System (GPS) receiver and the possibility for manual position fixes have been incorporated. System evaluation featured the Standard-Positioning-Service (SPS) and the Precise-Positioning-Service (PPS) of GPS. This effort has been conducted by Honeywell Sondertechnik in the time span 1992-1993. It highlights the important technical aspects and presents major test results. >

A cost-effective inertial motion sensor for short-duration autonomous navigation

Abstract: The need for systems, capable of continuously monitoring the inertial position and orientation of vehicles, has motivated the fields of inertial guidance and autonomous navigation. These systems typically employ suites of sophisticated motion sensors for obtaining measurements of motion occurring in all six axes of the Cartesian coordinate system. Through appropriate arithmetic manipulation of sensor output signals, the position and orientation of aircraft, satellites, submarines, and a host of other vehicles can be derived with respect to inertial space. While a wide variety of inertial sensor technologies have been demonstrated in these applications, there are still advances to be made. For example, gyroscopes are typically used to generate measurements of inertial angular position and inertial angular velocity. Requirements imposed on gyroscope drift rates drive up the cost of these instruments and force them to be fragile and complicated. Although there are applications in which gyroscopes remain the only proven solution, there are a growing number of applications in which conventional gyroscopes do not meet technical or cost requirements. This paper addresses the use of magnetohydrodynamic angular rate sensors (MHD ARS) as an alternative to gyroscopes in applications in which measurements are takers over short time durations. In such applications, drift rates, which exceed those exhibited by typical gyroscopes, can be tolerated in exchange for drastic reductions in sensor costs. The drift performance of the MHD ARS can be predicted based on the spectral description of the noise in the measurements provided by the instrument. A complete discussion of this analysis is presented in this paper. >

Advances in the state of the art for AUV inertial sensors and navigation systems

Abstract: Inertial navigation reference units are often thought of as simply a navigation device which must be augmented by another device to damp the Schuler oscillation and characteristic long-term drift. Emerging applications of AUVs, however, demonstrate a need for increasingly sophisticated inertial sensors. These inertial sensors are used not only for navigation, but as importantly, they provide data for sensor stabilization. Inertial systems have also traditionally represented a significant hotel load, been heavy, bulky and a source of acoustic and structure-borne noise. This paper presents an overview of two new inertial systems that are now in production at the Guidance and Control Systems Division of Litton Systems, Inc. These units are small, lightweight, require little power, and are silent. Data are presented that show long-term performance as well as short-term attitude, attitude rate, position, and velocity reference data for the two systems. Attitude, velocity and body axis rate data are required for stabilization of such devices as laser line scanners and long baseline side-scan sonars. The relationship between the characteristics of these sensors and inertial type errors is explored. This analysis shows that it is not sufficient to specify the inertial system only in terms of its navigation CEP. The specification of the inertial unit must also be based on the needs of the sensor payload and include such considerations as the noise content, phase, and bandwidth of the stabilization reference.

Air-borne gravity and differential gravity surveying system

Abstract: A system for conducting an air-borne gravity survey of earth formations along the flight path of a helicopter or any other aircraft comprises an acceleration/gravity sensor assembly (AGSA) which includes at least one inertial measurement unit (IMU) containing accelerometers and gyroscopes capable of acquiring all three components of total linear as well as angular accelerations and a differential global positioning system (ΔGPS) to provide location of the aircraft for derivation of all three linear motion acceleration components which after subtraction from the total linear inertial acceleration components will yield gravity acceleration components.

Use of the Global Positioning System for evaluating inertial measurement unit errors

Abstract: A trajectory reference system based on the Global Positioning System (GPS) can be used instead of conventional radars during missile flight tests. The high quality of the GPS-based trajectory reference makes it useful for evaluating the performance of the missiles' inertial measurement units. Such a system was installed and flight tested on two recently launched ballistic missiles. The GPS hardware configuration used on these flights is described. A Kalman filter approach is used to estimate individual inertial measurement unit errors based on the GPS range and delta range data. The ability of the GPS-based system to identify inertial measurement unit errors is compared to that of radar; the GPS is found to provide superior estimates.

Differential Inertial Filter for Dynamic Sensor Alignment

Abstract: The Differential Inertial Filter (DIF) estimates the in-flight alignment of mission sensors and weapons mounted on modern aircraft with dynamically flexing structures. Sensor/weapon attitude is defined by the instrument frame of a local inertial measurement unit (IMU). Misalignments are defined relative to the instrument frame of the reference inertial navigation system (INS). Differences between the IMU and INS acceler- ometer and gyro outputs provide a measure of the IMU/INS angular misalignment. The DIF is a Kalman filter that em- ploys accelerometer and gyro difference measurements to estimate the local misalignment angle components. Linear and angular vibration at the IMU location comprise the dominant sources of measurement noise. IMU and INS errors comprise smaller but important error sources. The DIF filter design for this challenging estimation problem is described, and simulated performance results are presented. DIF estimation accuracy capabilities are summarized for three repesentative locations on an advanced tactical aircraft.

Low cost quartz rate sensors applied to tactical guidance IMUs

Abstract: The military has shifted its emphasis from strategic weapons to tactical weapons. The challenge in meeting the needs of this shift is to develop a small, low-cost inertial measurement unit (IMU) with sufficient accuracy to meet the needs of modern precision tactical weapons. New instruments, new digital signal processing techniques and the Global Positioning System (GPS) have redefined the cost and performance capability achievable with tactical IMUs. Rockwell International is developing a Digital Quartz IMU (DQI) to meet the needs of this new generation of IMU requirements. The DQI is being designed around an inertial sensor assembly (ISA) being jointly developed by Rockwell International and the Systron Donner Inertial Division of BEI. The ISA utilizes small, batch-fabricated quartz inertial sensors to achieve low cost and small volume. Traditional analog processing of the output of this class of sensor has been replaced with digital processing based on sigma delta analog-to-digital converters to achieve improved performance. This combination of low-cost batch processed sensors with the stability of high-speed digital signal processing produces an IMU that meets the needs of a wide variety of tactical weapons with attractive performance/cost ratios. Prototypes of the DQI design will be completed and evaluated in early 1994. The paper provides an overview of the DQI design and status. A description of the performance objectives and design approach used for the inertial sensor assembly, digital signal processing and mechanical packaging of the DQI are presented. >

On range and attitude estimation

Abstract: Two algorithms to support an airborne, gimballed, electro-optical sensor are described. They have been designed for "Litening", a new targeting and navigation pod, which has been developed by Rafael. A full inertial measurement unit (IMU), capable of measuring linear acceleration and angular velocity, in three orthogonal axes, is mounted in the inner-most gimbal. The first algorithm estimates the attitude of the sensor line of sight (LOS). This estimation, accompanied by on-line sensor calibration, is carried out by a multi-state, multi-measurement Kalman filter, which is integrated within a strapdown navigation system. The second algorithm deals with the range (from a ground target) estimation. A new, linear (!), range estimation problem is formulated. Due to available data, range dynamics is presented as a linear, time varying system. A linear measurement equation, based on an appropriate error model, is obtained as well. >

Assessing the Feasibility of Accelerometer-Only Inertial Measurement Units for Artillery Projectiles

Abstract: : Inertial navigation systems estimate velocity and position information from measurements made with inertial instruments. Most often such systems have included accelerometers and gyroscopes. It has been shown analytically that it is possible to obtain the information necessary to determine both linear accelerations and angular motions using only measurements from linear accelerometers. An accelerometer-only inertial measurement unit would be an attractive candidate for use on artillery projectiles due to the availability of high-g miniature accelerometers. After including coding to compute acceleration forces at arbitrary locations on the projectile, a computerized trajectory model was used to evaluate the abilities of various configurations of linear accelerometers and processing algorithms to accurately estimate the components of the projectiles' linear and angular motion. Projectile guidance, Inertial measurement units, Accelerometers.

Dual Use of Military Anti- Jam GPS Receiver Design Techniques for Commercial Aviation RF Interference Integrity Monitoring

Abstract: There have been numerous papers published on GPS integrity monitoring from the perspective of detect- ing and reporting space segment failures. Another im- portant aspect of GPS integrity monitoring that has received less attention is the monitoring of radio fre- quency (RF) interference which can result in degraded accuracy performance or complete loss of receiver tracking. The RF interference source can be friendly or intentional and may be predictable or unpredictable. For military applications, intentional jamming is expected. Therefore, military GPS receivers are usually designed to be robust under severe jamming threats. Commercial GPS receivers seldom have built-in design provisions to either monitor or minimize the effects of RF interference, but this may become an important requirement for com- mercial aviation. The effect of RF interference is reduced carrier to noise power density ratio, C/No. When C/No is reduced below the tracking threshold of a receiver, the GPS measurements are corrupted and the navigation func- tion can no longer operate reliably unless the system is augmented by an inertial measurement unit (which is immune to RF interference). P(Y) code is more robust than C/A code to RF interference. In addition, C/A code is vulnerable to continuous wave (CW) RF interference due to a leak- through phenomena that is described in the paper. This C/Acodevulnerability may become an additional source of RF interference problems for commercial aviation GPS receivers since Standard Positioning Service (SPS) GPS users will be denied access to P(Y) code when antispoofing is activated. This paper describes RF interference measurement techniques for the purpose of GPS integrity monitoring. It also describes several GPS receiver and antenna design techniques which can add tracking robustness when C/No is reduced by RF interference. These dual- use techniques should be considered if RF interference becomes a source of GPS signal integrity problems for commercial avionics applications.

Signal processing for fiber optic gyroscope (FOG)

Abstract: A fiber-optic gyroscope (FOG) is expected to be the next generation gyroscope for guidance and control, because of various advantages. We have been developing the FOG-Inertial Navigation and Guidance (ING) for M-V satellite launching rocket of the Institute of Space and Astronautical Science (ISAS) since 1990. The FOG-ING consists of an Inertial Measurement Unit (IMU) and an Central Processing Unit Assembly. At current status, the proto-flight model FOG-IMU is being actively developed. And the flight test of the FOG-ING was performed on February 20, 1993, aboard M-3SII-7 satellite launching rocket at the ISAS test facilities in Uchinoura, Japan. This paper presents the signal processing technologies of our FOG which are used for the above FOG-ING.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Fiber optic gyro inertial measurement unit for fly-by-light advanced systems hardware

Abstract: Smiths Industries (SI) is preparing a Fiber Optic Gyroscope (FOG) Inertial Measurement Unit (IMU) for incorporation into the Advanced Research Projects Agency Technology Reinvestment Project Fly-by-Light Advanced Systems Hardware (FLASH) laboratory demonstration. The IMU provides inertial data to the flight control system through the FLASH optical data bus and consists of three FOGs, three quasi-solid state accelerometers, sensor control electronics, a digital signal processor, and the optical data bus interface. Reliable, low cost solid state sensors are used to satisfy the performance requirements of the system. Specifically, the FOGs use state-of-the-art optical technology to measure aircraft rotations. FOGs have no moving parts and are therefore more reliable and durable than spinning wheel gyroscopes. Many FOG designs are based on a multitude of individual optical components and sensing coils fabricated from expensive polarization preserving fiber. Smiths Industries has developed a FOG design which uses low cost, commercially available single mode fiber in the rate sensing coils and makes maximum use of integrated optics to reduce cost and complexity. This sensor has demonstrated excellent tactical grade performance in a wide range of strenuous test environments. The SI FOG IMU is an important contributor to the performance, reliability, cost, and capability advantages of the FLASH system.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Estimation of unstabilized components in vehicular motion

Abstract: This paper presents a kinetic-model based algorithm for estimating some unstabilized components in vehicular motion. In addition to smooth motion, there are unstabilized components such as bounce, pitch and roll in vehicular motion. A two-wheel vehicle model available in the literature is used to take into account the bouncing and pitching components. The dynamics of these unstabilized components are formulated using standard equations of motion. Assuming that depth information is known for some landmarks in the scene (e.g. obtained from a laser range finder) and inertial sensors such as accelerometers are available, a feature-based approach is proposed do estimate these unstabilized components. Simulation results for a stochastic terrain profile is presented.

Estimation of unstabilized components in vehicular motion

Abstract: This paper presents a kinetic-model based algorithm for estimating some unstabilized components in vehicular motion. In addition to smooth motion, there are unstabilized components such as bounce, pitch and roll in vehicular motion. A two-wheel vehicle model available in the literature is used to take into account the bouncing and pitching components. The dynamics of these unstabilized components are formulated using standard equations of motion. Assuming that depth information is known for some landmarks in the scene (e.g. obtained from a laser range finder) and inertial sensors such as accelerometers are available, a feature-based approach is proposed do estimate these unstabilized components. Simulation results for a stochastic terrain profile is presented.

IMU noise evaluation for attitude determination and stabilization in ground and airborne applications

Abstract: This paper reports on particular noise characteristics of selected ring laser gyro and dry tuned gyro inertial measurement units for use in ground and airborne system applications such as vehicle sensor stabilization, short term vehicle attitude measurements, vehicle camera stabilization, and synthetic aperture radar motion compensation. >

Inertial measurement unit and method for improving its measurement accuracy

Abstract: An inertial measurement unit is provided which includes a core inertial measurement unit (13) having accelerometers (19, 21, 23) and gyroscopes (25, 27, 29) aligned along x, y and z axes to provide signals to an onboard computer (39) to determine position of the vehicle upon which they are mounted while in movement. A fourth accelerometer (35) is pivoted perpendicular to the direction of the gravitational field for measuring the gravitational field about the axis upon which it is mounted to provide a reference set of data to an onboard computer prior to movement of the vehicle upon which the system is mounted.

with a Minimum Set of Inertial Sensors

Abstract: This article summarises the activities of Honeywell Sondertechnik in Maintal Germany in the development and prototyping of a new low cost land navigation system (ILANA) with a minimum amount of inertial sensors. The system utilises one (331308 Ring-Laser-Gyro, two vibrating beam accelerometers REiA5OO and a hodometer. To aid the system, a Global Positioning System (GPS) receiver and the possibility for manual position fixes have been incorporated. System evaluation featured the Standard-Positioning-Service (SPS) and the PrecisePositioning-Sexvice (PPS) of GPS. "his effort has been conducted by Honeywell Sondertechnik in the time span 1992-1993. The article is highlighting important technical aspects and presents major test results.

Control procedure for missile fired at fast-moving target - using single calculator linked to thrusters, inertial sensors and memory circuit

Abstract: The procedure involves providing commands for the missile's thrusters directly from information relating to the relative kinematics of the missile and target, the actual movement of the missile, and the aerodynamic model of the missile. The relative kinematics of the missile and target are determined from inertial measurements, and measurements of the distances between the missile and target in the automatic guidance mode. The system uses a single calculator (7) with its different inputs connected to the inertial sensors (4), kinematic sensors (6) for the movement of the missile and target, and an aerodynamic model memory circuit (8) for the missile. The calculator's outputs are connected to the missile's thrusters. ADVANTAGE - Makes best use of thrusters to minimise distance between missile and target, without substantial increase in cost.

Research on Performance of Inertial Velocity Aiding GPS/SINS Integration System

Abstract: GPS/INS integration systems are widely used in different fields Since GPS receiver carrier loop has lost lock during maneuver,the velocity aiding signal of code loop is derived from the inertial navigation system Because of the correlation between the pseudorange measurement error and the inertial velocity etror,it will make the integration system operation instable On the basis of GPS receiver code loop operation characteristics, the code loop tracking error is considered in the Kalman filterOptimal navigation satellites are selected in real time by a GPS simulator The navigation performance of a GPS/SINS integration system is analyzed during the airplane maneuverThe simulation results show that the code loop operates in the tracking state,the integration system operates normally and stably,and the navigation accuracy of the system is evidently improved when the correlanon between the pseudo-range measurement error and the inertial velocity error is eliminated

Flight test results of the Rockwell MIGITS

Abstract: A new standard of lightweight, low cost, integrated GPS/INS products has been created with the introduction of Rockwell's family of MIGITS (Miniature integrated GPS/INS Tactical System) products. This family takes full advantage of the precision pseudorange and pseudorange rate information available only from an embedded GPS receiver. This information is integrated with inertial data in a single Kalman filter in a synergistic manner which results in superior operation in high dynamic, antenna shading, and jamming environments. The Rockwell MIGITS has successfully demonstrated ability to tightly couple a tactical grade IMU with GPS to provide precise navigation operation in a dynamic environment. The integrated systems described in this paper build upon the lessons learned and the continued evolution of GPS. Continual refinements in research and development programs at Rockwell have led to this family of small integrated systems, resulting in what is believed to be the world's smallest, integrated GPS/INS systems available today, the MIGITS. The MIGITS products are intended to satisfy the navigation requirements of a variety of applications including missiles, both fixed and rotary wing aircraft, UAV's, munitions, targets and drones. This paper provides an introduction to the various MIGITS systems, followed by a description of the system testing performed thus far. >

GPS Receiver Using In-Vehicle Diversity Antenna

Abstract: This paper describes an enhanced in-vehicle Global Positioning System (GPS) receiving system. The system relies on inertial dead reckoning to back up the GPS equipment during periods with satellite blockage.

A common open avionics architecture

Abstract: Discusses an avionics architecture for unmanned air vehicles (UAV) that is common to several different classes of UAV and that is open in that it can accommodate components from several different vendors. A prototypical implementation of this architecture is also discussed. >

High precision navigation for vehicles

Abstract: Differential satellite navigation (DSNS) has the potential for precise navigation of air and surface vehicles if the severe integrity problems can be solved. A complementary combination of DSNS and inertial sensors will improve the dynamic response significantly as well as the integrity. Simulations and flight tests have demonstrated that position accuracies in the decimeter range can be reliably realized for horizontal and vertical position components. Some applications, e.g. laserprofiling, flight inspection and automatic landings, demonstrate the high potential of DSNS. >