Gyrocompass System Research Articles

Adaptive bias and attitude observer on the special orthogonal group for true-north gyrocompass systems: Theory and preliminary results

This article reports an adaptive sensor bias observer and attitude observer operating directly on for true-north gyrocompass systems that utilize six-degree-of-freedom inertial measurement units (IMUs) with three-axis accelerometers and three-axis angular rate gyroscopes (without magnetometers). Most present-day low-cost robotic vehicles employ attitude estimation systems that employ microelectromechanical system (MEMS) magnetometers, angular rate gyros, and accelerometers to estimate magnetic attitude (roll, pitch, and magnetic heading) with limited heading accuracy. Present-day MEMS gyros are not sensitive enough to dynamically detect the Earth’s rotation, and thus cannot be used to estimate true-north geodetic heading. Relying on magnetic compasses can be problematic for vehicles that operate in environments with magnetic anomalies and those requiring high-accuracy navigation as the limited accuracy ( error) of magnetic compasses is typically the largest error source in underwater vehicle navigation systems. Moreover, magnetic compasses need to undergo time-consuming recalibration for hard-iron and soft-iron errors every time a vehicle is reconfigured with a new instrument or other payload, as very frequently occurs on oceanographic marine vehicles. In contrast, the gyrocompass system reported herein utilizes fiber optic gyroscope (FOG) IMU angular rate gyro and MEMS accelerometer measurements (without magnetometers) to dynamically estimate the instrument’s time-varying true-north attitude (roll, pitch, and geodetic heading) in real-time while the instrument is subject to a priori unknown rotations. This gyrocompass system is immune to magnetic anomalies and does not require recalibration every time a new payload is added to or removed from the vehicle. Stability proofs for the reported bias and attitude observers, preliminary simulations, and a full-scale vehicle trial are reported that suggest the viability of the true-north gyrocompass system to provide dynamic real-time true-north heading, pitch, and roll utilizing a comparatively low-cost FOG IMU.

An Adaptive Damping Network Designed for Strapdown Fiber Optic Gyrocompass System for Ships.

The strapdown fiber optic gyrocompass (strapdown FOGC) system for ships primarily works on external horizontal damping and undamping statuses. When there are large sea condition changes, the system will switch frequently between the external horizontal damping status and the undamping status. This means that the system is always in an adjustment status and influences the dynamic accuracy of the system. Aiming at the limitations of the conventional damping method, a new design idea is proposed, where the adaptive control method is used to design the horizontal damping network of the strapdown FOGC system. According to the size of acceleration, the parameters of the damping network are changed to make the system error caused by the ship’s maneuvering to a minimum. Furthermore, the jump in damping coefficient was transformed into gradual change to make a smooth system status switch. The adaptive damping network was applied for strapdown FOGC under the static and dynamic condition, and its performance was compared with the conventional damping, and undamping means. Experimental results showed that the adaptive damping network was effective in improving the dynamic performance of the strapdown FOGC.

1-축 자이로센서를 이용한 진북 추종 알고리즘 특성에 관한 연구

The true north-finding equipment utilizing gyro sensor is used for INS(Inertial Navigation System) and has an increasing preference for gyro compass system due to compact size, lightening, low power and price. The purpose of this experiment is to research gyro compass system providing high performance in the field of manned or unmanned gyro compass system which proposes the accuracy of 1% utilizing experimented equipment at true north of the earth. Unlike the conventional system, the proposed gyro sensor system indicates to be applied in the various and specific equipment using multiple technique and method.

Reconfigurable control for ship steering

This paper is concerned with the application of a heuristic approach in the design of a fault-tolerant control system for ship steering. It proposes an advanced reconfigurable control system (RCS) for ship course changing/keeping and track keeping, robust to faults in actuator, gyrocompass and global positioning system (GPS) in the presence of disturbances (waves and currents). The proposed control scheme uses a reference model for compensation of signals from fault sensors and a compensator for reducing the loss of the control performance produced by a fault in the steering machine. In the case of the occurrence of the fault in one or more components, this control system minimizes loss in the control performance and gives enough time for operators to take appropriate action in order to reduce the risk of safety hazards and avoid severe consequences of the fault. The unavoidable penalty of degradation in control performance was found to be acceptable.

Development of Precision Fiber-Optic Gyro for Marine Gyrocompass System.

Progress in interferometoric fiber-optic gyroscope (I-FOG) for marine gyrocompass-system is reported. In the use of marine gyrocompass, I-FOG needs higher performance than for aircraft use. For marine gyrocompass and ships inertial navigation system (SINS) two classes of I-FOG are under development in the 0.005 °/h range and the superior one. For use in precision I-FOG, ASE (Amplified Spontaneous Emission) source of Er-doped fiber (EDF) has been developed.

Analysis of an Air Motion System on a Light Aircraft for Boundary Layer Research

Abstract A system has been developed for use on a light aircraft for the measurement of the turbulent wind vector components that does not rely on the use of either an inertial navigation system (INS) or Doppler radar. The system described here uses a five-hole probe to measure the wind vector relative to the aircraft. A GPS system, a vertical gyroscope for aircraft pitch and roll angles, a gyrocompass system, and a strap-down three-axis accelerometer system are used to obtain aircraft motion. Flight tests and results of an intercomparison with the United Kingdom Meteorological Office C-130 are presented. Under conditions of straight and level flight, the estimated rms errors are 0.3 m s−1 for the vertical wind component and 2 m s−1 for the horizontal components.

Development of high grade fiber-optic gyroscopes

Tokimec has been developing high grade interferometric fiber-optic gyroscopes (I-FOGs) for useful applications. The I-FOG consists of a sensing coil module, a light emitting module and an electronics circuits module. We achieved the bias stability of 0.003 deg/h and the angular random walk of 0.001 deg/√h and the scale factor error of 10 ppm (1σ). Then the azimuth error of the strapdown gyrocompass system with the high grade I-FOGs was less than ±0.05 s λ (deg) under the environmental temperature condition 23±5(°C).

A Reduced State Estimator for Orbital Heading Reference

It is practical to estimate only yaw, using a single gyro, rather than estimating bom roll and yaw with the more conventional two-gyro arrangement. In the development of observer theory, such a mechanization is termed a state estimator. A decoupled single-skewed-gyro gyrocompass is developed using estimation theory, and design curves are presented for parameter selection as a function of noise models for the gyro and horizon sensor. The modern development of mis gyrocompass system is compared with earlier analyses showing the advantage of the modern approach. Noise models are discussed for each instrument and related to performance through the mechanization parameters for use in design. Design parameter selection is based on a numerical optimization technique. It is concluded that the reduced state estimator can provide reliable and accurate yaw measurements on the ordej of 0.1° without the cost and complexity of a stellar reference system or of the two-gyro gyrocompassing mechanism.

The electrical engineering aspect of degaussing

The paper covers the development of degaussing of warships and merchant ships from the electrical engineering aspect. Early temporary D.G. installations consisting of cables clipped on deck are described, followed by detailed accounts tracing the evolution of the various permanent systems of degaussing, from the first external copper-strip coils energized from low-voltage motor-generators, to the latest high-voltage, resistance-regulated systems of internal multicore-cable coils, incorporating automatic course-correction equipment controlled by the ship's gyro-compass system. The type of cable for the coils and methods of jointing used on the different forms of D.G. installations are outlined. A description of the D.G. equipment on one of the latest battleships is also included.