Showing papers on "Inertial reference unit published in 2000"

Inertial navigation systems with geodetic applications

Abstract: Coordinate frames and transformations ordinary differential equations inertial measurement unit inertial navigation system system error dynamics stochastic processes and error models linear estimation INS initialization and alignment the global positioning system (GPS) geodetic application.

Method and apparatus for inertial guidance for an automobile navigation system

Abstract: The present invention discloses an improved vehicular inertial guidance navigation system, a.k.a. a dead reckoning system for navigation of a vehicle. The inertial guidance navigation system which may be used alone or in combination with other position determination means, such as GPS and map databases, to determine the location of a vehicle. The dead reckoning system has several advantages over existing systems. First, it can be easily mounted to the chassis of any vehicle. Second, it does not require any interface with existing sensors on the vehicle. Third, the system contains logic for removing errors in the position and heading determinations, brought about by angulation/rotation of the chassis and inertial guidance sensors, brought about by inclination or tilt of the chassis, with respect to an inertial/quasi-inertial frame of reference, such as the earth. The inertial guidance system includes: an inertial guidance sensor, a translation unit, and a logic unit. The inertial guidance sensor is suitable for coupling to the vehicle. The inertial guidance sensor senses motion of the vehicle in a non-inertial frame of reference and forming a sensor signal corresponding thereto. The translation unit is coupled to receive the sensor signal formed by the inertial guidance sensor. The translation unit translates the sensor signal into a quasi-inertial frame of reference and forms a translated signal corresponding thereto. The logic unit receives the translated signal formed by the translation unit and converts converting the translated signal into an estimated position and heading of the vehicle.

Vehicle positioning method and system thereof

Abstract: An improved fully-coupled vehicle positioning process and system thereof can substantially solve the problems encountered in global positioning system-only and inertial navigation system-only, such as loss of global positioning satellite signal, sensibility to jamming and spoofing, and inertial solution's drift over time, in which the velocity and acceleration from an inertial navigation processor are used to aid the code and carrier phase tracking of the global positioning system satellite signals, so as to enhance the performance of the global positioning and inertial integration system, even in heavy jamming and high dynamic environments. The improved fully-coupled GPS/IMU vehicle positioning system includes an IMU (inertial measurement unit) and a GPS processor which are connected to a central navigation processor to produce navigation solution that is output to an I/O (input/output) interface.

Head tracking relative to a moving vehicle or simulator platform using differential inertial sensors

Abstract: Inertial trackers have been successfully applied to a wide range of HMD applications including virtual environment training, VR gaining and even fixed-base vehicle simulation, in which they have gained widespread acceptance due to their superior resolution and low latency. Until now, it has been impossible to use inertial trackers in applications which require tracking motion relative to a moving platform, such as motion-base simulators, virtual environment trainers deployed on board ships, and live vehicular applications including helmet-mounted cueing systems and enhanced vision or situational awareness displays. This paper describes a new technique which makes it possible to use inertial head- tracking systems on-board moving platforms by computing the motion of a `tracking' Inertial Measurement Unit (IMU) mounted on the HMD relative to a `reference' IMU rigidly attached to the moving platform. Detailed kinematic equations are derived, and simulation results are provided for the particular case of an inertial tracker with drift correction by means of ultrasonic ranging sensors, but the conclusions can be applied to hybrid inertial trackers involving optical, magnetic, or RF drift correction as well.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Tuned support structure for structure-borne noise reduction of inertial navigator with dithered ring laser gyros (RLG)

Abstract: Litton Marine Systems is manufacturing the third generation of the marine inertial navigators at the Sperry Marine Division using a new generation of dithered ring laser gyros (RLG) by Honeywell To satisfy the US and foreign navies, stringent military requirements for shock (MIL-STD-901D), vibration (MIL-STD-167) and structure-borne noise (MIL-STD-740) demanded that a new approach in vibration control be employed A combined structure supporting the inertial sensor assembly (ISA) is designed with nominal vibration frequencies outside the dithered ring laser gyro's forcing frequencies The ISA can then be rigidly supported without causing transmission of structure-borne noise Structure-borne noise levels are then attenuated while easily maintaining alignment of the sensor axes This paper addresses a passive vibration control solution implemented on the inertial measurement unit (IMU) of the MK39 Mod3A inertial navigator to meet the structure-borne noise levels of MIL-STD-740-2 By using a compact auxiliary mass, a tuned support structure housing a Honeywell DIG-20 ISA is achieved The robustness of this tuned support structure is demonstrated as Litton Marine Systems expands the product line with the enhanced system performance and high shock single axis indexed MK39 Mod3C inertial navigator system (INS) Presented analytical and experimental results demonstrate the effectiveness of the MK39 Mod3A auxiliary mass basic design This design required no further tuning for the MK39 Mod3C application The shock and vibration advantage of using this approach on an inertial navigator is highlighted The impact of the indexer assembly on system performance and wobble for the shock-isolated system is discussed

Case study: Inertial measurement unit calibration platform

Abstract: The Department of Mechanical Engineering and the Avionics Engineering Center at Ohio University are developing an electromechanical system for the calibration of an inertial measurement unit (IMU) using global positioning system (GPS) antennas. The GPS antennas and IMU are mounted to a common platform to be oriented in the angular roll, pitch, and yaw motions. Vertical motion is also included to test the systems in a vibrational manner. A 4-DOF system based on the parallel carpal wrist is under development for this task. High-accuracy positioning is not required from the platform since the GPS technology provides absolute positioning for the IMU calibration process. © 2000 John Wiley & Sons, Inc.

On-Orbit Calibration of Satellite Gyroscopes

Abstract: In order to maneuver satellites accurately from one attitude to another, onboard rate sensing gyroscopes usually must be calibrated after launch Several algorithms have been used to determine gyro biases, misalignments, and scale factors This paper describes algorithms that have been used in the past, discusses their advantages and limitations, and describes a new algorithm and the gyro calibration results obtained using this new algorithm The new algorithm has significant operational advantages in addition to being at least as accurate as other algorithms

Train positioning via integration and fusion of GPS and inertial sensors

Abstract: As new automatic train control and block systems advance, the accuracy of train position is required increasingly. Train position is updating rapidly, especially for high-speed railways. One sensor source is not reliable; multisensors are required to realize reliable and real-time positioning for critical train control. In order to verify the feasibility of the proposed method, test sensors used the global positioning system (GPS--for absolute positioning) and inertial sensors (for relative positioning). For inertial sensors, gyroscopes and accelerometers were used to measure travel direction and distance, respectively. GPS has good low-frequency behavior, but poor high-frequency behavior. Inertial sensors (and dead-reckoning) have the opposite characteristics. By using their complementary characteristics advantageously, accurate train positioning can be implemented. To integrate the multisensors effectively, researchers developed the error compensation model for inertial sensors and used and extended Kalman filter to get the optimal train position estimation. The paper presents the prospective results provided by the preliminary tests.

Magnetohydrodynamic inertial reference system

Abstract: Optical platforms increasingly require attitude knowledge and optical instrument pointing at sub-microradian accuracy. No low-cost commercial system exists to provide this level of accuracy for guidance, navigation, and control. The need for small, inexpensive inertial sensors, which may be employed in pointing control systems that are required to satisfy angular line-of-sight stabilization jitter error budgets to levels of 1-3 microradian rms and less, has existed for at least two decades. Innovations and evolutions in small, low-noise inertial angular motion sensor technology and advances in the applications of the global positioning system have converged to allow improvement in acquisition, tracking and pointing solutions for a wide variety of payloads. We are developing a small, inexpensive, and high-performance inertial attitude reference system that uses our innovative magnetohydrodynamic angular rate sensor technology.

Application of Roll-Isolated Inertial Measurement Units to the Instrumentation of Spinning Vehicles

Abstract: Roll-isolated inertial measurement units are developed at Sandia for use in the instrumentation, guidance, and control of rapidly spinning vehicles. Roll-isolation is accomplished by supporting the inertial instrument cluster (gyros and accelerometers) on a single gimbal, the axis of which is parallel to the vehicle's spin axis. A rotary motor on the gimbal is driven by a servo loop to null the roll gyro output, thus inertially stabilizing the gimbal and instrument cluster while the vehicle spins around it. Roll-isolation prevents saturation of the roll gyro by the high vehicle spin rate, and vastly reduces measurement errors arising from gyro scale factor and alignment uncertainties. Nine versions of Sandia-developed roll-isolated inertial measurement units have been flown on a total of 27 flight tests since 1972.

The application of microminiature inertial measurement unit to the measurement of ejection movement parameters

Abstract: The microminiature inertial measurement unit (MIMU), a new style of the inertial measurement system, has many advantages compared with the traditional IMU, such as small size, light weight, low cost, little power consumption, high bearing capacity and long life. Undoubtedly, it will have wider applications in military and commercial fields. However, it is a pity that current micro inertial sensors do not have enough accuracy. Therefore, the applications of the MIMU were limited to some extent. This paper describes a MIMU and its system composition, operating theory and error control technique. In addition, its application to the measurement of ejection movement parameters (missile launch from an aircraft) is introduced. Finally, its performance and further applications are evaluated.

Atom interferometer inertial force sensors

Abstract: We report on the progress in the development of high sensitivity and accuracy inertial force sensors which are based on atom interference techniques.

Calibration of Inertial Sensors

Abstract: : The calibration of accelerometers, angular rate sensors, and inertial measurement units (IMU) increases the accuracy of their measurements. For artillery rounds and most rockets, measurements are acquired while the body is spinning. By the comparison of the sensor output to known input, calibration is accomplished. Calibration requires a model of the sensor. The model represents the measurement process. Model selection, calibration equipment, and data selection affect the usefulness of a calibration for a given mission. Calibration is model fitting for a specific mission or class of missions.

Adaptive robust damping of divergent oscillations in updatable inertial systems

Abstract: The functioning of an inertial navigation system (MS) is based on the modeling of the Schuler pendulum (1923) by a "gyro-accelerometer" (G-A) system. For such a system, a simplified structure of one channel is shown. This structure ensures the invariance of the modeled vertical with respect to the motion of the accelerometer base. If, however, the initial errors are unknown, the system will oscillate about the true local vertical; such oscillations are described by a differential equation.

Inertial guide apparatus and method for navigation system for car

Abstract: PROBLEM TO BE SOLVED: To provide a small-sized navigation system for a vehicle, having flexibility at determination of the present position from the pervious position, which is high in accuracy and efficiency and advantageous in term of cost. SOLUTION: Inertial guid sensors 212-216 detect the movement of a vehicle by a non-inertial coordinates system to from the sensor signals corresponding thereto. A deformation unit 304 is connected, in order to receive the sensor signals formed by the inertial guide sensors and deforms the sensor signals to a dummy inertial coordinates system to form the first signal corresponding thereto. A logic unit 308 receives the first signal formed by the deformation unit 304, to convert the same to the estimate value of the position and azimuth of the vehicle. COPYRIGHT: (C)2001,JPO

Application of the digital nautical chart (DNC) database to help identify areas of vertical deflection in the ring laser gyro inertial navigator (AN/WSN-7)

Abstract: Vertical deflection (VDEF) is a change in the local gravity vector that is sensed by the inertial navigation system (INS) accelerometers. Areas of VDEF are interpreted as erroneous ship acceleration, which result in the propagation of system velocity and position errors. Several manual techniques are identified to assist in minimizing these errors. The primary focus of these techniques centers on changing the ring laser gyro (AN/WSN-7) damping mode at the appropriate time as solely determined by the system operator. By utilizing the vector digital nautical chart (DNC) database, the AN/WSN-7 control display unit (CDU) can provide operator indications when areas of possible deflection are approaching. By automating aspects of determining areas of VDEF, a useful tool is provided to assist the operator in making more informed decisions about changing the damping mode of the AN/WSN-7. The heuristic techniques employed in the AN/WSN-7 navigation operating procedures (NOP) for VDEF operation were encapsulated into an object-oriented paradigm. The VDEF objects and methods are utilized with the geospatial information contained within the DNC database to provide enhanced situational awareness for the AN/WSN-7 operator. The methods of indicating VDEF regions in a semi-automated fashion utilizing the DNC are explained.

Inertial-magnetic systems of attitude definition

Abstract: A possibilities of inertial and magnetic methods, a path of a design inertial-magnetic systems used to define a translation and angular orientation are considered. The singularities of a strapdown inertial navigation systems (SINS) application in a complex with three-component flux gate magnetometer, the methods of processing of a measurement information will be discussed.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Improving the accuracy of an inertial measurement unit

Abstract: A missile guidance system employs a strap down inertial measurement unit with a separate accelerometer and star sensor that are moved for preflight accelerometer initialization. During flight, light is directed on the accelerometer and inertial measurement unit to produce on the star sensor images of the light source, the accelerometer and inertial measurement unit. The location of these images, which manifest the acceleration and position of the inertial measurement unit relative to the vehicle, are used to improve the accuracy of the inertial measurement unit data for vehicle guidance.