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Showing papers on "Inertial measurement unit published in 1992"


Patent
28 Dec 1992
TL;DR: In this article, an on-board vehicle information detection equipment comprises an inertial measurement unit providing dynamic vehicle motion information to a position processor, depending on the amount and quality of apriori knowledge of the vehicle route.
Abstract: A railway traffic control system in which accurate vehicle information is effectively available in real-time to facilitate control of traffic flow. Unlike prior art methods of precisely monitoring train location, the current invention is dependant only on equipment on-board the vehicle and position updates provided by external benchmarks located along the track route. The system's dynamic motion capabilities can also be used to sense and store track rail signatures, as a function of rail distance, which can be routinely analyzed to assist in determining rail and road-bed conditions for preventative maintenance purposes. In presently preferred embodiments, the on-board vehicle information detection equipment comprises an inertial measurement unit providing dynamic vehicle motion information to a position processor. Depending on the amount and quality of apriori knowledge of the vehicle route, the inertial measurement unit may have as many as three gyroscopes and three accelerometers or as little as a single accelerometer. To minimize error between benchmarks, the processor preferably includes a recursire estimation filter to combine the apriori route information with movement attributes derived from the inertial measurement unit.

130 citations


Patent
12 Feb 1992
TL;DR: In this paper, a Fault-Tolerant Inertial Navigation System (FTNS) consisting of at least two inertial navigation units is presented. But the two units are fully capable of performing navigational functions, and each of the units produces a set of independent navigational solutions at each of their respective outputs.
Abstract: Disclosed herein is a Fault-Tolerant Inertial Navigation System comprising, in a preferred embodiment, a Redundant Set of at least two Inertial Navigation Systems, from which one may identify and isolate at least one instrument within an Inertial Navigation Unit which shows substantial performance degradation. The two inertial navigation units are fully capable of performing navigational functions. Each of these inertial navigation units has a plurality of navigational instruments, including at least three linear sensors (such as accelerometers) and three angular change sensors (such as gyroscopes or ring laser gyroscopes). No two linear sensors nor any two angular change sensors of either unit are aligned colinearly. Each of the inertial navigation units produces a set of independent navigational solutions at each of their respective outputs. The independent navigational solutions of each of the navigation units are compared and any significantly degraded performance of any one linear sensor or any one angular change sensor is detected.

57 citations



Journal ArticleDOI
TL;DR: An elaborate covariance study suggests that estimation of all three components of balloon-borne gravity vectors to an accuracy of 5 mGal (1 mGal = 10−5 m/s2) is feasible using “within reach” electronic and engineering capabilities.
Abstract: The Air Force is planning to launch a helium-filled balloon possessing a payload of an inertial ring laser gyro strapdown system and a 3-antenna, minimum 12-channel, dual-frequency GPS receiver. A ground-fixed, single-antenna GPS receiver will be centrally placed beneath the balloon’s trajectory, allowing for differential mode GPS tracking. The inertial measurement unit’s (IMU’s) accelerometers will measure the total kinematic accelerations in the body frame. These will be transformed to local (n,e,d) navigation frame components using the integrated attitude of the balloon obtained from the IMU’s gyroscopes. GPS-determined accelerations will reflect total inertial accelerations, which can easily be expressed in the navigation frame. Differencing the two sets will thus yield the desired gravitational accelerations. An elaborate covariance study was conducted involving a 36-state, 43-noise-process open-loop Kalman filter. Using conservative initial IMU and GPS error source values, the covariance study suggests that estimation of all three components of balloon-borne gravity vectors to an accuracy of 5 mGa1 (1 mGa1 = 10~5 m/s2) is feasible using “within reach” electronic and engineering capabilities. Leveling uncertainties are the main contributors to the overall gravity vector estimation error budget.

12 citations


Journal ArticleDOI
TL;DR: A comparison of this system in space and on an airborne platform shows the relative importance of each system element in these two different acceleration environments.
Abstract: The Global Positioning System (GPS) is considered in conjunction with a strapdown Inertial Measurement Unit (IMU) for measuring the gravity vector. A comparison of this system in space and on an airborne platform shows the relative importance of each system element in these two different acceleration environments. With currently available instrumentation, the acceleration measurement accuracy is the deciding factor in space, while on an Earth-bound (including airborne) platform, the attitude error of the IMU is most critical. A simulation shows that GPS-derived accelerations in space can be accurate to better than 0.1mgal for a 30s integration time, leading to estimates of 1° mean gravity anomalies on the Earth's surface with an accuracy of 4–5 mgal. On an airborne platform, the horizontal gravity estimation error is tightly coupled to the attitude error of the platform, which can only be bounded by external attitude updates. Horizontal gravity errors of 5mgal are achievable if the attitude is maintained to an accuracy of 1arcsec.

9 citations


Proceedings ArticleDOI
23 Mar 1992
TL;DR: In this article, the authors explored the use of an inexpensive inertial measuring unit (IMU) with the GPS (Global Positioning System) for providing continuous navigation during a GPS blockage due to buildings, wing blockage during a maneuver, etc.
Abstract: A concept being explored is the use of an inexpensive IMU (inertial measuring unit) with the GPS (Global Positioning System). An inexpensive IMU can meet many of the same functional requirements as the high-accuracy system, with the exception of long-term position. For example, some applications for instrumenting a reference frame are antenna stability, satellite acquisition (including GPS), platform stability, flight stabilization, and heading information. The acceleration data could still be integrated to find velocity and position; however, this position information would only be used for a period of minutes. For example, to provide continuous navigation during a GPS blockage due to buildings, wing blockage during a maneuver, etc. The author presents the capabilities of a unit of this type which was developed for the US Army. >

7 citations


Journal ArticleDOI
TL;DR: In this paper, a detection, localization and correction of failure in a launch vehicle guidance and control system is proposed based on monitoring an abrupt change in the error signal in each of the feedback loops, namely, the actuator, digital autopilot, navigation and guidance as well as control loops of inertial sensors such as gyroscopes, inertial platform servos and accelero-meters.
Abstract: A detection, localization and correction of failure in launch vehicle guidance and control system is proposed. The detection and localization of faults is based on monitoring an abrupt change in the error signal in each of the feedback loops, namely, the actuator, digital autopilot, navigation and guidance as well as control loops of inertial sensors such as gyroscopes, inertial platform servos and accelero-meters. Correction schemes are proposed for errors located in each of the loops. A scheme based on reshuffling of control functions to healthy actuators, in the case of a single failure in an actuator loop, is described. Failures in inertia sensors are overcome by software signal reconstruction from healthy sensors. Failures in a guidance loop cause a switchover to an open loop mode that provides vehicle turning rates that are optimal at the last valid loop instant. Retargetting is provided to account for widespread dispersions in vehicle thrust performance.

5 citations



Proceedings ArticleDOI
23 Mar 1992
TL;DR: In this article, the TRIAD (three-axis attitude development) algorithm is reformulated to use two pairs of gravitational measurements instead of star observations to achieve threeaxis attitude determination, which eliminates time to complete alignment transfer from the major contributors of the alignment error.
Abstract: The authors present a novel alignment transfer method which uses only accelerometer measurements in the gravitational field. The TRIAD (three-axis attitude development) algorithm is reformulated to use two pairs of gravitational measurements instead of star observations to achieve three-axis attitude determination. A major benefit of the ABAT method is the freedom to choose missile inertial measurement unit gyroscopes based solely on in-flight considerations. An additional benefit is the ability to update the alignment transfer by simply making new measurements of gravity and reprocessing the measurements taken before erection. The proposed alignment transfer method eliminates time to complete alignment transfer from the major contributors of the alignment error. Algorithm development, error analysis, and laboratory results are provided. >

4 citations


01 Jul 1992
TL;DR: The Air Force Phillips Laboratory's Technology for Autonomous Operational Survivability (TAOS) space experiment is scheduled for launch on an Air Force653STEP spacecraft in early 1993.
Abstract: The Air Force Phillips Laboratory’s Technology for Autonomous Operational Survivability (TAOS) space experiment is scheduled for launch on an Air Force Space Test Program Space Test Experiment Platform (STEP) spacecraft in early 1993. The mission will test and evaluate two navigation systems that support autonomous satellite navigation. They are the Microcosm Autonomous Navigation System (MANS) and the Rockwell Autonetics Six-Channel Global Positioning System (GPS) Receiver. MANS is a true autonomous system that uses horizon scanners, modified for Sun and Moon detection, as primary measurement devices to determine position, velocity, and attitude and estimate position and velocity using a Kalman filter. MANS supplemental sensors include GPS and an inertial measurement unit (IMU). The Rockwell miniature GPS receiver is a semi-autonomous system which accesses the GPS network to determine spacecraft position, velocity, and time. Position and velocity reference data will be generated using direct measurements from Air Force Satellite Control Network (AFSCN) remote tracking stations (RTS), orbit reconstruction based on on-board beaconry, and post-processed GPS data and solutions. The attitude reference will be provided by an on-board strapdown IMU.

3 citations


Journal ArticleDOI
TL;DR: In this paper, an inertial measurement unit based on three dry-tuned gyroscopes, two of which are unbalanced, is described. And the design of the controller/estimator is illustrated with test data.
Abstract: This paper describes an inertial measurement unit based on three dry tuned gyroscopes, two of which are unbalanced. This configuration, without the three usual accelerometers, leads to savings in space, weight, and cost that are necessary in guidance systems for agile missiles. Design objectives are wideband estimation of angular rate and linear acceleration applied to the inertial measurement unit together with high stiffness of caging loops. The contribution of this paper is to show how to address the coupled high-frequency dynamics of the six measurement outputs of the system, by applying the so-called linear quadratic Gaussian technique. First the linearized model of the rotor motion of each dry-tuned gyroscope is derived from a mechanical analysis. Then the design of the controller/estimator is described. Performances are illustrated with test data.

Proceedings ArticleDOI
23 Mar 1992
TL;DR: In this article, the authors used the ADKEM (advanced kinetic energy missile) IMU (inertial measurement unit) performance requirements as a platform to discuss various error sources and their contribution to the system performance and to indicate possible applications of this technology for the future.
Abstract: The author uses the ADKEM (advanced kinetic energy missile) IMU (inertial measurement unit) performance requirements as a platform to discuss various error sources and their contribution to the ADKEM system performance and to indicate possible applications of this technology for the future. Particular attention is given to the ADKEM IMU error budget. >

Proceedings ArticleDOI
23 Mar 1992
TL;DR: The author considers the use of a massively parallel signal processing architecture in GPS (Global Positioning System)/inertial sensors to acquire satellite signals in fractions of a second, as well as the current application of Kalman filtering to estimating and eliminating continuous-wave jammer.
Abstract: Summary form only given. The author considers the use of a massively parallel signal processing architecture in GPS (Global Positioning System)/inertial sensors to acquire satellite signals in fractions of a second (vs. tens of seconds today), as well as the GPS-inertial synchronization and mechanization required to extend the current application of Kalman filtering to estimating and eliminating continuous-wave jammer has also been explored. Satellite signal acquisition results based on analyses, verified by simulation and live data, have been obtained for both C/A and P-code acquisition in the presence of jammer. Similar data have been obtained for tracking in a high jamming environment. All results are with the Honeywell GG1308 RLG-based IRU and an IEC GPS sensor. >

Book ChapterDOI
01 Jan 1992
TL;DR: In this article, a comparison of using the Global Positioning System (GPS) in conjunction with a strapdown Inertial Measurement Unit (IMU) to measure the gravity vector in space and on a balloon shows the relative importance of each system element in these two different acceleration environments.
Abstract: A comparison of using the Global Positioning System (GPS) in conjunction with a strapdown Inertial Measurement Unit (IMU) to measure the gravity vector in space and on a balloon shows the relative importance of each system element in these two different acceleration environments. With currently available instrumentation, the acceleration measurement accuracy is the deciding factor in space, while on the balloon (or other aircraft), the orientation error of the IMU platform is most critical. A simulation shows that GPS-derived accelerations in space are accurate to better than 0.1 mgal for a 30 s integration time, leading to estimates of 1° mean gravity anomalies on the Earth’s surface with an accuracy of 4–5 mgal. On a balloon, the horizontal gravity estimation error is tightly coupled to the orientation error of the platform, which can only be bounded by external attitude updates. Horizontal gravity errors of 5 mgal are achievable if the attitude is maintained to an accuracy of 1 arcsec.

Proceedings ArticleDOI
TL;DR: Capabilities that future GPS receivers will need to meet envisioned US Army missile system requirements are outlined.
Abstract: It is pointed out that at any given time there are several different missile systems under development. Each of these systems requires some form of guidance or navigation system. In the past, this requirement has been met through the use of inertial sensors. To meet future system requirements, it is envisioned that it will be necessary to incorporate GPS (Global Positioning System) receivers on the launchers and into the missiles. The size, weight, power, performance, number of channels, and cost of these GPS receivers are critical. The authors outline capabilities future GPS receivers will need to meet envisioned US Army missile system requirements. >

Proceedings ArticleDOI
23 Mar 1992
TL;DR: The authors describe the Texas Instruments/Honeywell Phase 1 Global Positioning System (GPS) Guidance Package (GGP) architecture and performance characteristics.
Abstract: The authors describe the Texas Instruments/Honeywell Phase 1 Global Positioning System (GPS) Guidance Package (GGP) architecture and performance characteristics. The GGP is a tightly coupled, integrated miniature GPS receiver (MGR) and miniature inertial measurement unit (MIMU) capable of performing precision navigation, time coordination, mission management, and flight control for a broad class of Department of Defense platforms. These include strike weapons, unmanned airborne vehicles, and avionics platforms. The MGR architecture contains a highly integrated six-channel (expandable to eight channels) L1/L2 P(Y) code precise positioning service receiver/processor packaged on a single wiring board. The MGR design features a low-power GaAs integrated front end. The MIMU contains three interferometric fiber-optic gyros and three solid-state accelerometers in an inertial sensor assembly plus associated electronics and a microprocessor. The remaining GGP architecture consists of a data processor/data bus unit (DP/DBU) and an adaptable interface unit (AIU). The DP/DBU performs the tightly coupled, integrated navigation function. It has reserve memory and throughput cavity to perform mission management and flight control functions. The AIU supports numerous standard interfaces. >

01 Jan 1992
TL;DR: The paper describes the method of dead reckoning in vehicle navigation applications and explains the principles of common types of odometers and differential odometers as well as the physical phenomena, structures, and examples of odometer realizations made with different techniques.
Abstract: Several types of navigation systems have been considered for automotive navigation. Almost all the vehicular navigation systems have one common feature: basic in-car navigation is based in these systems on dead reckoning, which is enhanced with other methods like map matching, proximity beacons, or satellite navigation systems. The paper describes the method of dead reckoning in vehicle navigation applications. Terminology used in the area is explained. The basic theory of dead reckoning is given. The principles of common types of odometers and differential odometers are described as well as the physical phenomena, structures, and examples of odometer realizations made with different techniques. Other distance measurement devices are also described. The other component of dead reckoning calculations, heading, can be measured with magnetic compasses, gyroscopes, optical gyros, and other means. These methods are explained and component realizations are shown. Inertial navigation systems are described briefly in order to give the reader some basic information for comparison between dead reckoning and inertial navigation methods.

29 Jan 1992
TL;DR: In this paper, the feasibility of using a miniature GPSreceiver to navigate a naval gun-launched projectile to a target is investigated. But the main concerns of the study are the GPS aspects of the guided projectile.
Abstract: This paper presents the results of a study investi- gating the feasibility of using a miniature GPS receiver to navigate a naval gun-launched projectile to a target. The main concerns of the study are the GPS aspects of the guided projectile. Risk factors such as the impact of shock and vibration on electronic components, the timely acquisition of the satellite signal, jamming, projectile rotation, and cost are addressed. In addition, the performance enhancements obtained by integrating the receiver with an inertial measurement unit (IMU) are discussed. Recommendations are given based on results of the study.

29 Jan 1992
TL;DR: The Zero-lock Laser GyroTM (ZLG) as mentioned in this paper is a four-mode multioscillator ring laser gyro for stellar-inertial navigation systems.
Abstract: The four-mode multioscillator ring laser gyro, designated as the Zero-lock Laser GyroTM (ZLG) by Litton, enables new and innovative approaches to mechanizing high accuracy stellar-inertial navigation systems. Absent any requirement for dithering or rate biasing to circumvent the lock-in phe- nomenon inherent in conventional two-mode ring laser gy- ros (RLG), the ZLG offers many advantages for stellar- inertial systems. The ZLG does not impose any disturbing dynamic motion on the stellar sensor, facilitating high accu- racy star tracking. In addition, the extremely precise scale factor of the ZLG allows comounting of the stellar sensor with the inertial sensors on a common instrument cluster and sequentially pointing the whole stellar-inertial sensor clus- ter at multiple target stars to measure the inertial system errors. This eliminates the need for the highly accurate angle encoders used in currently operational stellar-inertial sys- tems to transform stellar observations to their inertial refer- ence axes. Factory production of medium-accuracy ZLG inertial navi- gation systems (INS) was initiated in early 1991 for several military andcommercial contractual programs. Since stellar updates can correct for gyro drift errors, the same medium- accuracy ZLG is being utilized in Litton developmental pro- grams for high accuracy stellar-inertial systems. This paper describes the significant differences between four- and two-mode RLGs, the tradeoffs in mechanizing RLG/ZLG-based stellar-inertial systems, the specific applications of ZLG technology to stellar-inertial programs, and the resultant benefits.

Proceedings ArticleDOI
23 Mar 1992
TL;DR: The objective of the tests was to demonstrate that the HAINS can replace the KT-70 IMU in the Space Shuttle Orbiter, both singularly and totally.
Abstract: The authors present a description, results, and interpretation of comparison testing between the high accuracy inertial navigation system (HAINS) and the KT-70 inertial measurement unit (IMU). The objective of the tests was to demonstrate that the HAINS can replace the KT-70 IMU in the Space Shuttle Orbiter, both singularly and totally. The most significant improvement of performance came in the tuned inertial/extended launch hold tests. The HAINS exceeded the 4-hour specification requirement. The performance of the HAINS demonstrated the transparency of operation with respect to the KT-70 IMU. In addition, an internally compensated INS is compatible with the Orbiter avionics and flight software. >