Showing papers on "Inertial measurement unit published in 1993"

Modern Inertial Technology: Navigation, Guidance, and Control

Abstract: This book describes the modern inertial technology used for guidance and control in navigation. Sensors, gyroscopes, chronometers, and accelerometers are specifically addressed in detail and their principles, operation, design, advantages and disadvantages are discussed. An engineer with a vast practical experience in the field, the author elucidates themost recent developments in inertial guidance in the US, Europe, and Japan. Among these are fiber-optic gyroscopes, the satellite-based global positioning system, inertial navigation systems, and solid-state accelerometers. The book should thus be of great interest to researchers and graduate students as well as to system engineers and specialists involved in aeronautics and space research.

Aerospace Avionics Systems: A Modern Synthesis

Abstract: Introduction, Coordinate Systems and Transformations Inertial Sensors Kinematic Compensations Equations Error Analysis Externally Aided Inertial Navigation Systems Steering, Speical Navigation Systems, And Modern Avionics Systems Appenices: System Performance Criteria The World Geodetic System Subject Index References

Mobile robot attitude estimation by fusion of inertial data

Abstract: An attitude estimation system based on inertial measurements for a mobile robot is described. Five low-cost inertial sensors are used: two accelerometers and three gyros. The robot's attitude, represented by its roll and pitch angles, can be obtained using two different methods. The first method is based on accelerometric measurements of gravity. The second one proceeds by integration of the differential equation relating the robot's attitude and its instantaneous angular velocity which is measured by the gyrometers. The results of these two methods are fused, using an extended Kalman filter. Experimental results show that the resulting system is very sensitive and accurate. >

An inertial navigation system for a mobile robot

Abstract: A low-cost, solid-state inertial navigation system for robotics applications is described. Error models for the inertial sensors are generated and included in an extended Kalman filter (EKF) for estimating the position and orientation of a moving robot vehicle. A solid-state gyroscope and an accelerometer have been evaluated. Without error compensation, the error in orientation is between 5-15/spl deg//min but can be improved at least by a factor of five if an adequate error model is supplied. Similar error models have been developed for each axis of a solid-state triaxial accelerometer. Linear position estimation with accelerometers and tilt sensors is more susceptible to errors due to the double integration process involved in estimating position. WIth the system described here, the position drift rate is 1-8 cm/s, depending on the frequency of acceleration changes. The results show that with careful and detailed modeling of error sources, low cost inertial sensing systems can provide valuable position information.

Apparatus and method for autonomous satellite attitude sensing

Abstract: An attitude sensing system utilizing simplified techniques and apparatus includes a Kalman filter which receives signals from an inertial measurement unit, a GPS receiver, and an integrated optical assembly. The output vector of the filter includes estimates of attitude misalignments and estimates of gyro drifts corresponding to the axes of the inertial measurement unit. The optical assembly includes a sensor array providing signals to the filter representing detection of the Earth's horizon or the center of the Sun. More particularly, a local vertical vector, computed from fore and aft detections of the Earth's horizon, is used in combination with GPS received signals to initially determine attitude by means of gyrocompassing. This attitude information is thereafter maintained by the inertial measurement unit and azimuth error resulting from drift of the inertial measurement unit and the initial gyrocompassing error is corrected by detections of the Earth's horizon and the Sun. The integrated optical assembly, used to detect the locations of both the Sun and Earth relative to the satellite, eliminates a need for separate apparatus dedicated to each sensing function. Moreover, the GPS receiver eliminates the need for ground tracking apparatus by providing the satellite ephemerides (including orbital pitch rate used in gyrocompassing) for use by the filter, rendering the attitude sensing system substantially autonomous. Additionally, the GPS receiver, in combination with the Sun and Earth detections, eliminates the need for a complex star tracker by providing an accurate inertial frame of reference.

Inertial measurement unit providing linear and angular outputs using only fixed linear accelerometer sensors

Abstract: An inertial measurement unit is provided in which an arrangement of linear accelerometers in fixed positions measure angular acceleration and other inertial characteristics. Only linear acceleration readings are required for measurement of angular acceleration, and both expensive angular sensors and cyclically driven linear accelerometers are eliminated. A processor receives the linear accelerometer signals and calculates output values related to both the angular and linear motion of the body. In the preferred embodiment, the inertial measurement unit includes at least nine linear accelerometers, three disposed with their respective sensitive axes in substantially mutually orthogonal relationship defining first, second and third axes intersecting at a single origin point, and a pair of linear accelerometers disposed along each axis spaced at fixed distances from the origin point with their sensitive axes in substantially orthogonal relationship with each other and the axis. The present invention also includes a control system using the inertial measurement unit of the present invention to control the operation of a first component in response to angular motion of a second component connected thereto, and a method for inertial measurement of angular acceleration.

Strapdown Stabilization for Imaging Seekers

Abstract: : In space constrained applications such as tactical missiles, locating the inertial sensors off the platform simplifies packaging and may allow existing missile autopilot gyros to be used for platform stabilization. In strapdown stabilization, inertial sensors are fixed to the base of the inertial platform rather than directly on the platform itself. Gimbal position sensor information is combined with body-fixed inertial rate sensor information to estimate the inertial rate of the platform. This estimate of platform rate is a key factor that determines the stabilization performance of the system. An initial assessment of the feasibility of strapdown stabilization for high-resolution imaging seekers was conducted. A linear state space model and a detailed nonlinear planar simulation were developed of a tactical high-resolution platform system. The simulation includes gimbal inertia, inertial sensors, position sensors, friction, mechanical alignment, compliances, and control loop compensation. The simulation was used to predict the platform stabilization performance. In addition, effects of stabilization performance on target signal strength for an imaging seeker were estimated.

Rapid and Robust Transfer Alignment

Abstract: The design of a rapid and robust transfer alignment system for advanced kinetic energy missiles (ADKEMs) is presented in this paper. Owing to the high acceleration level and reduced engagement time of the ADKEM, the transfer alignment which aligns the salve (missile) inertial measurement unit (IMU) with the master (ground launch vehicle) IMU must be accomplished in a short time with high accuracy. The scope of transfer alignment system design presented in this paper encompasses the assessment of inertial guidance accuracy, transfer alignment formulation, maneuver scenario design, and sensitivity analysis.

A better way to navigate on deep sea floors

Abstract: IFREMER-French Institute for Sea Exploration and Exploitation-is currently operating manned submersibles, towed sonars and ROVs down to 6000 m. IFREMER are replacing their positioning system resting on long base line (LBL) by a new positioning system called POSIDONIA which is under development at the company group Thomson Sintra ASM and Mors Environment. This replacement aims to reduce operators time and overall costs by improving accuracy, reliability and flexibility in comparison with the existing systems. To achieve these characteristics, the POSIDONIA positioning system is of a new breed which combines a short base line (SBL) and an ultra short base line (USBL). It has been designed to operate in noisy environments and get rid of multipath effects, to compensate for the lack of precise radio navigation, and generally to comply with the various task requirements. Therefore, not only has the acoustic signal processing been optimized, but also the beacon functionalities to give full versatility. In addition, the need of a high precision vertical and heading reference unit (VHRU), to make up for the vessel attitude, has induced the definition of a hybrid VHRU based on both GPS and inertial sensors. >

Gyroscopic system for boresighting equipment by optically acquiring and transferring parallel and non-parallel lines

Abstract: A gyroscopic system and method is provided for translating parallel and non-parallel lines between a reference line and a device to be aligned with respect to the reference line A first inertial sensor (60) is provided that is configured to be substantially stationary This inertial sensor is boresighted with respect to the reference line and includes at least two gyroscopes and a mirror (61) having first and second nonplanar surfaces A second, portable inertial sensor (62) is provided that includes a gimbal, a gimbal drive system, an electronic energy beam generator, a collimator, and at least two gyroscopes One or more of the electronic beam generator, collimator, and gyroscopes can be optionally mounted on a platform that is mounted on the gimbal and adapted to move in accordance with signals from the gimbal drive system A control circuit (68) is provided that is operable to measure output signals generated by the first and second inertial sensor gyroscopes and to determine relative orientations of the inertial sensors

From the Luminiferous Ether to the Boeing 757: A History of the Laser Gyroscope

Abstract: Inertial navigation systems are central to modern navigation. They permit wholly self-contained navigation of remarkable accuracy. They are now standard in long-range civil aircraft and most modern military aircraft, as well as in ballistic missiles, cruise missiles, space boosters, and submarines. They are increasingly to be found in shorter-range tactical missiles, land vehicles such as tanks or selfpropelled artillery, and some surveying applications. At the heart of inertial navigation are the inertial sensors themselves: gyroscopes, which sense rotation, and accelerometers, which measure acceleration. During the last twenty years, the former have undergone what those involved see as a technological revolution. Since the beginnings of inertial navigation in the 1930s, the gyroscopes used had remained analogs-however sophisticated--of the child's spinning toy, reliant in their detection of rotation on the mechanics of a rapidly revolving rotor. But they have now been challenged by inertial sensors in which the detection of rotation is achieved by optical, rather than mechanical, means: laser gyroscopes. All the major corporate suppliers of inertial technology, bar one, are heavily committed to laser gyroscope technology. A basic shift has thus taken place in this key modern technology. This article begins with the conceptual origins of the laser gyroscope, which are remote from the "high-tech" world of the modern

Transfer alignment design and evaluation

Abstract: The design of a rapid and robust transfer alignment system for advanced kinetic energy missiles (ADKEMs) is presented in this paper. Owing to the high acceleration level and the reduced engagement time of ADKEMs, the transfer alignment which aligns the salve (missile) inertial measurement unit (IMU) with the master (ground launch vehicle) IMU must be accomplished in a short time with high accuracy. The scope of transfer alignment system design presented in this paper includes the assessment of inertial guidance accuracy, transfer alignment formulation, simulation environment development, maneuver scenario evaluation, system error analysis, tradeoff study, and filter robustness and sensitivity analysis.

Integrated guidance system and method for providing guidance to a projectile on a trajectory

Abstract: An inertial measurement unit is provided which includes a core inertial measurement unit having accelerometers and gyroscopes aligned along x, y and z axes to provide signals to an onboard computer to determine position of the vehicle upon which they are mounted while in movement. A fourth accelerometer 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.

Design of global positioning system receivers for integrated inertial navigation systems

Abstract: There is much interest in integrated navigation using the global positioning system and inertial measurement units (accelerometers and gyroscopes). The results reported in this paper quantify integrated navigation performance as a function of GPS receiver design parameters. The specific application considered is missile navigation. >

The use of GPS 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 (IMUs). 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 IMU errors based on the GPS range and delta range data. The ability of the GPS-based system to identify IMU errors is compared to that of radar; GPS is found to provide superior estimates of the IMU errors.

Application of GPS for Missile Post Flight Guidance Accuracy Analysis

Abstract: The high quality of a GPS-based trajectory reference makes it useful for evaluating the performance of a missile's Inertial Navigation System (INS) during a missile flight test. The complexity of the design of the GPS user segment depends on flight test objectives and factors such as the expected satellite/vehicle geometry. Design curves are developed which illustrate the relationship between flight test objectives, the GPS user segment design, and such factors as antenna performance.

An investigation of airborne GPS/INS for high accuracy position and velocity determination

Abstract: An airborne test using a differential GPS-INS system in a Twin Otter was conducted by Sandia National Laboratories to assess the feasibility of using the integrated system for cm-level position and cm/s velocity. The INS is a miniaturized ring-laser gyro IMU jointly developed by Sandia and Honeywell while the GPS system consists of the NovAtel GPSCard{trademark}. INS position, velocity and attitude data were computed using Sandia`s SANDAC flight computer system and logged at 4 Hz and GPS data was acquired at a 1 Hz rate. The mission was approximately 2.5 hours in duration and the aircraft reached separations of up to 19 km from the base station. The data was post-processed using a centralized Kalman filter approach in which the double differenced carrier phase measurements are used to update the INS data. The INS position is in turn used to detect and correct GPS carrier phase cycle slips and also to bridge GPS outages. Results are presented for the GPS-only case and also for integrated GPS/INS.

Aircraft Autonomous Integrity Monitoring for an Integrated Satellite/Inertial Navigation System

Abstract: By turning to an operational status in near future Global Navigation Satellite Systems (GNSS) like the U.S. GPS and its Russian pendant GLONASS provide highest accuracy navigation capabilities when using differential techniques. In principle the po- sition accuracy can comply with ICAO-limits for precision approaches and taxi guidance (submeter respectively meter range), if the initial ambiguities and cycle slips in the phase measurement are detec- ted and adapted. For aviation applications under real environment se- veral effects onboard the aircraft like satellite mas- king, multipath, cycle slips, dynamic influences on the receiver, electromagnetic disturbance etc. de- grades GNSS integrity to an unacceptable level, so that even with sufficient satellites, GNSS would not be capable for sole mean navigation. Concerning system integrity checks of satellite na- vigation, two different approaches, Receiver Auto- nomous Integrity Monitoring (RAM) and ground based overlay techniques (e.g RGIC) with different advantages and shortcomings are in discussion so far, but none is able to compensate insufficiencies of the satellite systems concerning dynamic envi- ronment and reliability. Therefore inertial sensors are an ideal complement to GNSS, due to their good dynamic behaviour, alt- hough they are characterized by longterm drift as a result of misalignment, accelerometer and gyro errors. Their budget varies with dynamic manoeu- vres so that a preflight error determination and sy- stem calibration is impossible. Combining both, satellite and inertial system, via Kalman-filter techniques there is the ability to esti- mate and compensate separated sensor errors of the inertial as well as the satellite systems within a hy- brid, complementary navigation system. In result the demands in quality (i.e. accuracy as well as reliability) can be satisfied. Starting in 1989 the In- stitute of Flight Guidance and Controlpublically de- monstrated the feasibility concerning the accuracy aspect several times by means of automatic flight tests. In addition to the limitations of usual integrity mo- nitoring concepts for satellite navigation systems this paper shows an approach for reduction of these problems with the help of a hybrid GNSS-/Inertial- Navigation System. In this concept Aircrafl Auto- nomous Integrity Monitoring can be utilizied even under worse conditions (e.g. bad satellite geometry, non-redundancy of satellite information) when for example RAIM algorithms do not fit any more.

An inertial navigation system for robot measurement and control

Abstract: The present paper deals with application of inertial sensors in the field of robotics. Quite in contrast to conventional applications, short integration times and higher acceleration values are considered. Furthermore, when used as an dynamic augmentation of robot measurement and control, the static sensor offsets can be handled with much more ease. The author presents a gyroless inertial sensor head for the sensing of motion induced acceleration on robotic mechanisms. The sensor signals are used for real-time calculation of position and orientation changes of the mechanism. A discussion of error sources is included, and a simulation of a two dimensional sensor arrangement demonstrates the influence of sensor and mounting errors. Further more, the utilization of the system as a redundant signal source for measurement and control, as well as the possibility of robot vibration damping is analyzed. >

Transferring the Bearing Using a Strapdown Inertial Measurement Unit

Abstract: Of all the various possibilities of using an inertial measurement unit (IMU) in surveying engineering only the determination of a reference bearing and its transfer is focussed upon in this paper. Strapdown-systems differ from the conventional gimballed platform-configuration by the use of the sensors which are sensitive to a rotation of the IMU. The gyroscopes, usually three Ringlasergyros or two Dynamical Tuned Gyros are, in addition to the accelerometer triad, fixed to the carrier. Thus the gyros serve as rate sensors and not as stabilizing elements as in the case of gimballed platform-systems. The advantage of fewer hardware components and thus lower hardware purchase and maintenance costs is opposed by the exposition of the sensors to the whole dynamical environment of the carrier. After an initial alignment with respect to the local horizontal frame the determined alignment-angles can be transferred to another control point by a proper evaluation of the sensor output without the necessity of a direct line of sight between the two points. In this paper the potential of the determination of the alignment and its transfer is discussed. In addition some simulation results of corresponding scenarios are presented.

GPS Navigation Requirements for Future Mobile Ground-Based Missile Systems

Abstract: At any given time there are several different missile systems under development. Each of these systems requires a guidance/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 receivers on the launchers and into the missiles. The size, weight, power, performance, number of channels, and cost of these GPS receivers are critical. This paper will outline capabilities needed in future GPS receivers in order to meet envisioned US Army missile system requirements.

The Integration of Differential GPS and Inertial Sensors for Positioning Australian Railways

Abstract: In a joint development project between Melbourne University and Sagem Australasia Pty Ltd, a system has been designed that combines differential GPS and inertial sensors to provide relative 3 dimensional position accuracies at the decimetric level. Originally developed to provide track data for the computerised driver training simulator being developed by the Public Transport Corporation of Victoria, Australia, the Rapid Rail Mapping System is now being applied to other projects within the rail industry and to systems for highway management. This paper discusses the special data collection and post-processing methods developed.The system currently uses only C/A code pseudorange data and inexpensive inertial sensors. This is in part due to the extensive preprocessiug of the sensor data before its subsequent modelling in the least squares solution. The result is a massive productivity improvement over existing survey methods, covering up to 200 kms of track per day. Future developments are planned to provide improvements in the GPS and inertial processing to increase the accuracies to the centimetric level.

Performance Needs for Advanced Kinetic Energy Missiles' Inertial Measurement Units

Abstract: A large number of commercial and military applications call for the use of inertial measurement units (IMUS). These applications vary vastly, however a new era is dawning where the need for and utilization of IMUS which can navigate through steady-state high acceleration environments are growing. These instruments will have to be very near or completely solid state because of the high acceleration loading. The performance of these instruments will be characterized by broader dynamic range, minimal nonlinear effects, higher noise rejection capability, but not necessarily low drift rate performance. These performance characteristics are driven by flight times on the order of a few seconds. These instruments must also exhibit small volume, low power, and low cost. An example of this type of IMU is the one needed for the Advanced Kinetic Energy Missile (ADKEM). ADKEM is a hypervelocity multi-role tactical missile which requires inertial grade navigation performance through a 1000-g environment.

Adaptive Treatment to CG Control Problem

Abstract: Direct adaptive controller is developed and incorporated into a missile's attitude control system (ACS) architecture to enhance its performance in the presence of system uncertainties The adaptive control algorithm is developed based on the simplified version of model reference adaptive control concept It possesses two practical performance features: (1) providing robust performance for the ACS system without the need of a parameter estimator, and (2) ease of implementation which is practically attractive to the enhancement of the ACS performance Its development and implementation are intended to primarily provide a better solution to the center of gravity (CG) control problem when firing a divert thruster with the line of force offset from its center of mass Robustness of the adaptive controller subject to Inertial Measurement Unit (IMU) uncertainties is also tested in this paper as the secondary objective

Micromachined Quartz Sensors for Tactical Missions

Abstract: Rockwell International is developing a small, low-cost iner- tial measurement unit (Ih4U) that would be suitable for tac- tical applications. The Digital Quartz IMU (DQI) is designed around an inertial sensor assembly (ISA) that is being jointly developed by Rockwell International and the Systron Donner Inertial Division of BEI. The ISA makes use of the advances in quartz micromachining for the fabrication of batch- processed inertial instruments: both gyros and accelerometers. The IMU also makes use of new digital signal processing techniques and has the capability to be integrated with GPS. This paper describes some of the current development and shows performance of both the quartz rate sensor (QRS) and the vibrating quartz accelerometer (VQA). Principles of operation are described and some design features of each sen- sor are discussed. Test data supporting the design goal of 1 deghr in the QRS and 1 mg in the VQA is presented.