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A detailed analysis, is presented in this paper, for the steady gyrostatic nanofluid flow past a permeable stretching/shrinking sheet with slip condition using the nanofluid model proposed by Buongiorno. The microorganisms are imposed into the nanofluid to stabilize the nanoparticles to suspend due to a phenomenon called bioconvection. Considering appropriate similarity transformations, the five partial differential equations of mass conservation, momentum, thermal energy and microorganisms are reduced to a set of four ordinary (similar) differential equations with coupled linear boundary conditions. These equations were both analytical and numerical solved using Runge-Kutta-Fehlberg technique. The influences of important physical parameters, such as, Prandtl number Pr, the Schmidt number Sc, the bioconvection Péclet number Pe, the Brownian motion parameter Nb, the thermophoresis parameter Nt and the stretching/shrinking parameter λon the skin friction coefficient Cf and the local Nusselt number Nux, as well as on the velocity, temperature and gyration profiles, are interpreted through graphs and tables. Further, multiple (dual, upper and lower branch solutions) are found for the governing similarity equations and the upper branch solution expanded with higher values of the suction parameter. It can be confirmed that the lower branch solution is unstable. It is found that the bioconvection parameters have strong influence towards the reduced skin friction coefficient, reduced heat transfer, velocity and density of motile microorganism's transport rates. [ABSTRACT FROM AUTHOR]

This article is concerned with the emergence of proto-cybernetic gadgets and specimen in Antarctica. The essay's starting point is that the Cold War was literalised at the South Pole, which also operates as a shadowy double of the overtly militarised Arctic. What happens in Antarctica is a secret assimilation of space into the American Cold War perimeter by way of weapons technology, most notably through the gyrocompass (which develops into the black box navigation systems for ballistic missiles) and the man–machine amalgamation. This assimilation and emergence are traced at hand of exploration narratives (Harold Ponting; Douglas Mawson; Richard Byrd) as well as science fiction stories (H. P. Lovecraft; John W. Campbell, Jr.) that precede the Cold War, but whose forging of a superman-specimen anticipate the conceptualisation of Antarctica as a Cold War space. The South Pole operates as zone of rehearsal for superpower merging: the explorers become prototype cyborgs whose expeditions point towards the containment culture, epitomised in the gyrocompass/black box technology, of the Cold War. [ABSTRACT FROM AUTHOR]

The rapidity and accuracy of the initial alignment influence the performance of the strapdown inertial navigation system (SINS), compass alignment is one of the most important methods for initial alignment. The selection of the parameters of the compass alignment loop directly affects the result of alignment. Nevertheless, the optimal parameters of the compass loop of different SINS are also different. Traditionally, the alignment parameters are determined by experience and trial-and-error, thus it cannot ensure that the parameters are optimal. In this paper, the Genetic Algorithm-Particle Swarm Optimization (GA-PSO) algorithm is proposed to optimize the compass alignment parameters so as to improve the performance of the initial alignment of strapdown gyrocompass. The experiment results showed that the GA-PSO algorithm can find out the optimal parameters of the compass alignment circuit quickly and accurately and proved the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Highlights • Spherical robot moves by changing the position of its center of mass and by changing gyrostatic momentum. • Stabilization of the spherical robot using only two control actions. • Tuning of controllers for stabilization of spherical robot of combined type. Abstract The paper is concerned with the problem of stabilizing a spherical robot of combined type during its motion. The focus is on the application of feedback for stabilization of the robot which is an example of an underactuated system. The robot is set in motion by an internal wheeled platform with a rotor placed inside the sphere. The results of experimental investigations for a prototype of the spherical robot are presented. [ABSTRACT FROM AUTHOR]

This article describes gyroscopes and their effects in various fields of everyday life. Gyroscopic effect is ability (tendency) of the rotating body to maintain a steady direction of its axis of rotation. The gyroscopes are rotating with respect to the axis of symmetry at high speed. Gyroscopic effect is related to all rotating mechanisms (wheels, gears, shafts, rotors, bicycles, motorcycles, children's toys...). In some cases, we want to enhance the gyroscopic effect (for stabilization, energy accumulation). Stabilization effect is mainly used for two-wheeled vehicles. It can be also used on ships and boats, where big wheel is rotating and preventing the boat to overturn. Gyroscopic effects can help with energy accumulation. The bigger rotating speed is achieved the bigger amount of energy is stored. When the gyroscope is well designed the efficiency can be much higher than in the batteries. In other cases we want to suppress or compensate it (in case of the direction change of the rotating device). This is mainly about the planes. When the pilot of the plane needs to change the heading then during the left turn the plane will go up and during the right turn it goes down. The use of gyroscopes is important in various modes of transportation. We describe different usage of gyroscopes in transport and logistics, especially gyrocompass (ships and planes - advantages: no influence by ferromagnetic materials, heading to the true North, disadvantages: errors caused by rapid changes in course, speed and latitude); attitude and heading indicators (plane); pendulous integrating gyroscopic accelerometer (rocketry); gyrostat - control moment gyroscope (space - stations, satellites and probes); MEMS gyroscope (automotive, entertainment, robots, etc.). [ABSTRACT FROM AUTHOR]

This paper proposes a simplified algorithm for reducing the computational load of the conventional underwater integrated navigation system. The system usually comprises a three-dimensional accelerometer, a three-dimensional gyroscope, a three-dimensional Doppler Velocity Log (DVL) and a data fusion algorithm, such as a Kalman Filter (KF). Since the expected variations of roll, pitch and depth are small, these quantities are assumed to be constant, and the proposed system is designed in a two-dimensional form. Due to the low speed of the vehicle, the nonlinear dynamic equation of the velocity can be simplified in a linear form. We also simplify the conventional KF in order to avoid matrix multiplications and matrix inversions. The performance of the designed system is evaluated in a sea trial by an Autonomous Underwater Vehicle (AUV). The results show that the proposed system can significantly reduce the computational load of the conventional integrated navigation system without a significant reduction in position and velocity accuracy. [ABSTRACT FROM AUTHOR]

Heading angle is a vital parameter in maintaining a vessel's track along a planned course and should be guaranteed in a stable and reliable way. An innovative method of heading determination based on a fisheye camera, which is almost totally unaffected by electromagnetism and geomagnetism, is proposed in this paper. In addition, unlike traditional astronomical methods, it also has a certain degree of adaptability to cloudy weather. Utilising the super wide Field Of View (FOV) of the camera, it is able to simultaneously image the Moon and the horizon. The Moon is treated as the observed celestial body and the horizon works as the horizontal datum. Two experiments were conducted at sea, successfully proving the feasibility of this method. The proposed heading determination system has the merits of automation, resistance to interference and could be miniaturised, making application viable. [ABSTRACT FROM AUTHOR]

When faults of some flight actuators have occurred, an unexpected need to use larger magnitudes and higher actuation rates of fault-free actuators is often caused if fault-tolerance design is not considered. This paper presents a fault-tolerant flight control (FTFC) capable of accommodating aircraft actuator failures while respecting to the physical control authority of healthy actuators, on the basis of sliding mode (SM) and adaptive techniques. Furthermore, this paper accounts for the availability of the measured angular rate. In the presence of reliable gyro onboard, the sensed pitch rate can be applied to the developed FTFC loop. In the absence of pitch rate measurement, a SM observer (SMO) is exploited to recover the pitch rate information, while the integrated design of the SMO and FTFC is investigated. Simulation studies of a nonlinear Boeing 747 longitudinal model are conducted to manifest the effectiveness of the proposed schemes. [ABSTRACT FROM AUTHOR]

This experiment demonstrated the resonance asymmetry phenomenon in the resonant fiber optic gyro. The asymmetry of resonant curve affects the system open-loop bias and its stability, which directly affects the accuracy of angular velocity measurement. In this paper, a new mathematic model is established. The influence of the coupler normal mode loss difference (the phase difference between the coupler cross port output optical field and direct port is less than the ideal π/2) on the symmetry of resonant curve, the resonant signal modulated by the triangular wave, and the demodulation curve are analyzed. Moreover, the asymmetry of the resonant curve leads to the asymmetry of the resonant signal, as modulated by the triangular wave and the demodulation curve from the theoretical simulation and the experiment. [ABSTRACT FROM AUTHOR]

This article has looked into the role of the magnetic compass in providing navigational safety for ships. The existing requirements of the magnetic compass for safe navigation in case the gyro compass breaks-down and in case of terrorists abusing GPS signals do not solve the problems that occur in everyday life. Therefore, a new rational requirement has been proposed for the accuracy and frequency of deviation adjustment work assuring the safety and cost effectiveness of navigation. Vessel owners and masters have responsibilities to ensure that magnetic compasses are maintained in good working order, are adjusted and accompanied by a table or curve of residual deviations. This article has outlined the most urgent problems for the adjustment of magnetic compasses that apply to all ships irrespective of size and navigation area. The proposed method has been verified experimentally. [ABSTRACT FROM AUTHOR]

In-motion alignment of strapdown inertial navigation systems (SINS) without any geodetic-frame observations is one of the toughest challenges for autonomous vehicles. Considering the characteristics of SINS, this paper presents a dual-model-based in-motion alignment method for the odometer-aided SINS. Two inertial navigation calculation loops are established for an inertial measurement unit (IMU), one of which executes the in-motion gyrocompass horizontal alignment algorithm to decompose the body velocity measured by odometer to navigation frame and attenuate the disturbance. And the other is the attitude determination-based alignment loop, where the vector observation-based SINS alignment is executed. The contributions of the work presented here are twofold. First, the dual-model initial alignment (DMIA) algorithm for SINS is proposed, which introduces the idea of constructing multiple calculation loops for an IMU to maximize the advantages of SINS. Second, depending on the body-frame speed-aided attitude determination and navigation-frame speed-aided attitude determination, the body-frame velocity observation with disturbance is accurately decomposed to navigation frame with the noise attenuated by gyrocompass horizontal alignment. The experimental results show that the proposed DMIA algorithm can achieve a rapid and accurate in-motion alignment. [ABSTRACT FROM AUTHOR]

For the strapdown inertial navigation system (SINS), the procedure of initial alignment is a necessity before the navigation can commence. On the quasi-stationary base, the self-alignment can be fulfilled with the high quality inertial sensors, and the fine alignment is usually executed to improve the alignment performance. Generally, fast estimating of heading misalignment is still a challenge due to the existence of gyro errors. An innovative data processing strategy called forward and backward resolution is proposed for INS initial alignment. The Rauch-Tung-Striebel (RTS) smoothing is applied to obtain the smoothed attitude estimates with the filter information provided by the forward data processing. The obtained attitudes are then treated as aiding measurements to implement the forward resolution with the repeated data set, the converged sensor biases are used as constraints, and the iterative processing is conducted to obtain the updated attitudes. Simulation studies have been conducted to validate the proposed algorithm. The results have shown that the alignment accuracy and convergence rate have been improved with the added RTS aided forward and backward resolution; more stable heading estimates can be obtained by calibrating with estimated gyro bias. A real test with a high quality inertial sensor was also carried out to validate the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

In a waist-worn Pedestrian Navigation System (PNS) based on Dead-Reckoning (DR), heading drift caused by Micro-Electro-Mechanical System (MEMS) gyro bias is an essential factor affecting DR accuracy. Considering the characteristics of pedestrian navigation and the poor bias repeatability of MEMS gyros, this paper presents a standing calibration method for MEMS gyro bias. The current gyro biases for each boot can be calibrated accurately in the initial stage before walking. Since the attitude angles calculated by the output data from magnetic sensor and accelerometers do not drift, this paper applies the reverse algorithm of attitude updating to calculate the angular velocities of human motion. Then the gyro biases at each moment can be acquired by subtraction operation between the measured angular velocities from gyros and the calculated angular velocities of human motion. Finally, in order to restrain the random error caused by sensor noise, the calculated biases in the initial stage are smoothed, and consequently the optimal estimate of current gyro biases after each boot can be obtained. Still and dynamic turntable experiments and a walking experiment are performed to compare and analyse the proposed method and the Zero Angular Rate Update (ZARU) method. Experimental results show that the proposed method can also calibrate the gyro bias accurately in the case of body swaying. [ABSTRACT FROM AUTHOR]

Fiber-optic gyro strapdown inertial navigation system is typically physically separated from the log giving an aiding velocity. This results in a velocity difference under angular motions, otherwise known as the outer lever arm effect. The mathematical relationship between the velocity difference and the outer lever arm is derived, and the effect of the outer lever arm on angular velocity compensation and harmful acceleration compensation is analyzed using the structure of in-motion gyrocompass alignment. Based on this analysis, a method for outer lever arm correction is given to counteract the outer lever arm effect on the performance of the alignment. Simulation and trial tests are then used to verify the analysis results. [ABSTRACT FROM AUTHOR]

The author presents a new perspective on the process of controlling course indicators, to fit with the modern equipment of present day ships, in line with current trends and prospects for its development. The newly proposed measures and methods in this research must address the following issues: the improvement of safety, reduction in routine work and improvement of the navigation services on a ship. This article includes an analysis of requirements and also test results relating to compliance with respect to the course indicators used on commercial vessels. The author presents and justifies the need to introduce changes to the procedures and practices of conduct, updating the current actual situation. The proposed new procedures should have a direct impact on the security of navigation. [ABSTRACT FROM AUTHOR]

BeiDou satellites transmit triple-frequency signals, which bring substantial benefits to carrier phase Ambiguity Resolution (AR). The traditional geometry-free model Three-Carrier Ambiguity Resolution (TCAR) method looks for a suitable combination of carrier phase and code-range observables by searching and comparing in the integer range, which limits the AR success probability. By analysing the error characteristics of the BeiDou triple-frequency observables, we introduce a new procedure to select the optimal combination of carrier phase and code observables to resolve the resolution of Extra-Wide-Lane (EWL) and Wide-Lane (WL) ambiguity. We also investigate a geometry-free and ionosphere-eliminated method for AR of the Medium-Lane (ML) and Narrow-Lane (NL) observables. In order to evaluate the performance of the improved TCAR method, real BeiDou triple-frequency observation data for different baseline cases were collected and processed epoch-by-epoch. The results show that the improved geometry-free TCAR method increases the single epoch AR success probability by up to 90% for short baseline and 80% for long baseline. The A perfect (100%) AR success probability can also be effortlessly achieved by averaging the float ambiguities over just tens of epochs. [ABSTRACT FROM AUTHOR]

Many ship accidents have arisen from an error in course indication. Bearing in mind that the actual errors in gyrocompass and satellite compass are really minor, they may be considered valid to be input into an autopilot provided that any failure in such devices is controlled by means of a secondary heading source such as a magnetic compass. However, magnetic compass deviation may be significant and its heading should be corrected before being input to the autopilot. The errors caused by the geographic variability of the deviation should also be taken into account. Moreover, the current way to reduce the deviation requires that the ship is un-berthed to execute a complete swing. The aim of this article is to obtain a ship magnetic model by means of an algorithm based on least squares to correct magnetic compass heading input in the autopilot and to permit definitive magnetic compass compensation without swinging the ship through 360°. [ABSTRACT FROM AUTHOR]

In this paper, two types of computational procedures are presented for a rest-to-rest spacecraft maneuver using a variable-speed double-gimbal control moment gyro (VSDGCMG). The first procedure is a numerical computational procedure in which a quasi-time-optimal trajectory satisfying several physical constraints is obtained by repeating the Newton’s method. The other procedure is an approximate computational procedure in which an analytical solution is obtained by approximately solving a series of linear optimal control problems. The two procedures play complementary roles: the former is suitable for implementation, and the latter can be used to select an initial value for use in the former. The effectiveness of the proposed procedures is demonstrated by plotting the surfaces of maneuvering time for all rotational axes and by plotting time responses for several maneuvering examples. [ABSTRACT FROM AUTHOR]

A magnetic compass has too large a heading error for many applications, and it is often not obvious how to achieve an accurate heading, in particular for low-cost navigation systems. However, there are several different methods available for finding heading, and their feasibility depends on the given scenario. Some of the methods may seemvery different, but they can all be related and categorised into a list by studying the vector that each method is using when achieving heading. A list of possible methods is very useful when ensuring that all relevant methods are being considered for a given application. For practical navigation, we have identified seven different vectors in use for heading estimation, andwe define seven corresponding methods. The methods are magnetic and gyrocompass, two methods based on observations, multi-antenna Global Navigation Satellite Systems (GNSS), and two methods based on vehicle motion. [ABSTRACT FROM AUTHOR]

In strap-down gyro-compass in-motion alignment, the alignment accuracy depends not only on the quality of the gyroscopes and accelerometers, but also on the accuracy of the velocity provided by the aiding sensors such as odometers. To improve the accuracy of the in-motion alignment, real-time accurate odometer velocity estimation is required. In this paper, the effect of the noise of the odometer velocity on strap-down gyro-compass in-motion alignment accuracy is presented, based on the strap-down gyro-compass algorithm. A velocity tracking model is designed as the state model, to describe the relationship between and among the vehicle’s velocity, acceleration and jerk in the vehicle frame. Based on the velocity equation applied to strap-down navigation system mechanizations, the vehicle’s acceleration in the vehicle frame can be obtained from the specific forces measured by accelerometers. With the observations including the vehicle’s acceleration in the vehicle frame and the vehicle’s velocity in the vehicle frame obtained from the odometer using the first order difference algorithm, real-time velocity estimates are produced by a Kalman filter. The field test results show that the proposed method can successfully improve the accuracy of the odometer velocity. The comparison with the traditional method highlights the superior performance of the proposed method. [ABSTRACT FROM AUTHOR]

The most important issue for intelligent mobile robot development is the ability to navigate autonomously in the environment to complete certain tasks. Thus, the indoor localization problem of a mobile robot has become a key component for real applications. In general, two categories of mobile robot localization technique are identified: one is robot pose tracking, and the other is robot global localization. In pose tracking problems such as the simultaneous localization and mapping (SLAM) process, the robot has to find its new pose using the observed landmarks or features in its knowledge base of its previous observations. In global localization methodology, a robot does not have knowledge of its previous pose. It has to find its new pose directly in the environment, such as by using a global positioning system (GPS). On the other hand, an artificial beacon-based localization technique, such as the received signal strength indicator (RSSI), causes higher pose uncertainty. However, the artificial beacon can provide a good initial reference for robot position mapping. The gyrocompass of a mobile robot is suited for short-term dead-reckoning. Also the RGB-D camera of a mobile robot can record meaningful features or landmarks in 3D space. The purpose of this work is to fuse the advantages of these sensors via strategy control by a particle filter to enhance the estimation accuracy of indoor mobile robot localization. [ABSTRACT FROM AUTHOR]

The interferometric fiber optic gyro (IFOG) that is inside the gyrocompass has been gradually equipped on the marine vessel and the vessel's swing is sensed by IFOG. This will affect the detection of Allan variance coefficients of IFOG while the vessel is in moorage especially in temperature variation conditions. However, the standard IFOG Allan variance noise analysis method is computationally expensive and requires massive data storage which is inappropriate for Allan variance coefficients real-time detection. In addition, for long-voyage and long-endurance requirements of the vessel in the marine environments, the ambient temperature variation causes errors that will degenerate IFOG accuracy. The vessel needs more independence including the fault diagnosis system and reconfiguration of the IFOG gyrocompass. To meet the marine vessel autonomy need, we propose a method for Allan variance coefficients detection including rate ramp R , rate stochastic walk K , bias instability B , angular stochastic walk N and quantization noise Q . In the study, we first eliminate the angular increments of vessel attitude by gravity in inertial frame in the moorage condition, and then realize the Allan variance coefficients real-time detection by adopting nonlinear adaptive Kalman filter with proposed state-space model. Simulations show that the proposed method potentially could implement the Allan variance coefficients’ real-time detection, and estimate the coefficients’ temperature variation effectively and correctly. [ABSTRACT FROM AUTHOR]

An EM-Log (Electromagnetic Log) aided in-motion gyrocompass alignment algorithm is proposed to accomplish the fine alignment for marine SINS (strapdown inertial navigation system) on sailing vessel. The EM-Log is used to track the maneuver velocity of the vessel and remove the earth rotation angular velocity and the angular velocity of the navigation frame relative to the earth frame from accelerometer measurements. In terms of SINS damping technology, we change the structure of gyrocompass alignment loop and employ EM-Log measurements to reduce the negative effects of vessel accelerations. The simulation and experiment results show that our proposed method could accomplish fine alignment of in-motion marine SINS, while the conventional one failed. [ABSTRACT FROM AUTHOR]

A new technique to improve the tracking performance of a ship-borne mobile telemetry antenna system in the marine environment is presented for Korea Space Launch Vehicle-I (KSLV-I) mission. The concept of ‘pointing bias’ is introduced to compensate for the instability or inaccuracy of a sensor in the ship-borne mobile telemetry antenna system. The LEO satellites in the form of ‘tracking campaign’ are used to measure the pointing bias. The proposed technique is verified through the tests in Jeju sea and Pacific sea in the period of November 23–28, 2012. The results demonstrated that the azimuth pointing bias about −0.27° and −0.49° appears in Jeju sea and Pacific sea, respectively and the pointing bias was proved to be mainly relevant to the heading measurement error of the gyrocompass. Taking into consideration of the pointing bias results in Jeju sea and Pacific sea, the gyrocompass was corrected by 0.25° to compensate for the heading measurement error on the ship-borne mobile telemetry antenna system. The correction value of 0.25° is selected to reduce the risk in tracking. Due to insufficient correction, the residual pointing bias about −0.12° in Pacific sea was observed and the successful tracking of KSLV-I is achieved on January 30, 2013. [ABSTRACT FROM AUTHOR]

Harmonic vibrations of high-speed rotors in momentum exchange devices are primary disturbances for attitude control of spacecraft. Active magnetic bearings (AMBs), offering the ability to control the AMB-rotor dynamic behaviors, are preferred in high-precision and micro-vibration applications, such as high-solution Earth observation satellites. However, undesirable harmonic displacements, currents, and vibrations also occur in the AMB-rotor system owing to the mixed rotor imbalances and sensor runout. To compensate the rotor imbalances and to suppress the harmonic vibrations, two control methods are presented. Firstly, a four degrees-of-freedom AMB-rotor model with the static imbalance, dynamic imbalance, and the sensor runout are described. Next, a synchronous current reduction approach with a variable-phase notch feedback is proposed, so that the rotor imbalances can be identified on-line through the analysis of the synchronous displacement relationships of the geometric, inertial, and rotational axes of the rotor. Then, the identified rotor imbalances, which can be represented at two prescribed balancing planes of the rotor, are compensated by discrete add-on weights whose masses are calculated in the vector form. Finally, a repetitive control algorithm is utilized to suppress the residual harmonic vibrations. The proposed field balancing and harmonic vibration suppression strategies are verified by simulations and experiments performed on a control moment gyro test rig with a rigid AMB-rotor system. Compared with existing methods, the proposed strategies do not require trial weights or an accurate model of the AMB-rotor system. Moreover, the harmonic displacements, currents, and vibrations can be well-attenuated simultaneously. [ABSTRACT FROM AUTHOR]

In a dedicated collisionality scan in Tore Supra, the geodesic acoustic mode (GAM) is detected and identified with the Doppler backscattering technique. Observations are compared to the results of a simulation with the gyrokinetic code GYSELA. We found that the GAM frequency in experiments is lower than predicted by simulation and theory. Moreover, the disagreement is higher in the low collisionality scenario. Bursts of non harmonic GAM oscillations have been characterized with filtering techniques, such as the Hilbert-Huang transform. When comparing this dynamical behaviour between experiments and simulation, the probability density function of GAM amplitude and the burst autocorrelation time are found to be remarkably similar. In the simulation, where the radial profile of GAM frequency is continuous, we observed a phenomenon of radial phase mixing of the GAM oscillations, which could influence the burst autocorrelation time. [ABSTRACT FROM AUTHOR]

The general geometry of the experimental tokamak magnetic equilibrium is implemented in the global gyrokinetic simulation code GEM. Compared to the general geometry, the well used Miller parameterization of the magnetic equilibrium is a good approximation in the core region and up to the top of the pedestal. Linear simulations indicate that results with the two geometries agree for r/a≤0.9. However, in the edge region, the instabilities are sensitive to the magnetic equilibrium in both the L-mode and the H-mode plasmas. A small variation of the plasma shaping parameters leads to large changes to the edge instability. [ABSTRACT FROM AUTHOR]

The kinetic instability of the obliquely propagating drift magnetosonic wave for temperature anisotropic low beta plasmas is studied by using the gyro-kinetic model. The interplay between the temperature anisotropy and the density inhomogeneity free energy sources is discussed in order to provide stabilization of drift instability by the temperature anisotropy effect. It is shown that the anisotropy suppresses the growth rate when the anisotropy ratio Ae,i(= T⊥(e,i)/T‖(e,i)) is greater than unity, whereas it enhances the growth rate for Ae,i <1 . Comparison of kinetic instability with reactive instability [Naim et al., Phys. Plasmas 21, 102112 (2014)] and the scaling of growth time with the diffusion and the anisotropy relaxation times are presented. Additionally, the stability analysis applicable to a wide range of plasma parameters is also performed. [ABSTRACT FROM AUTHOR]

Due to the impact of the nonlinear factor caused by large azimuth misalignment, the conventional gyrocompass alignment method is hard to favorably meet the requirement of alignment speed under the condition of large azimuth misalignment of INS. In order to solve this problem, an improved gyrocompass alignment method is presented in this paper. The improved method is designed based on the nonlinear model for large azimuth misalignment and performed by opening the azimuth loop. The influence of the nonlinear factor on gyrocompass alignment will be reduced when opening the azimuth loop. Simulation and experimental results show that the initial alignment can be efficiently accomplished through using the improved method in the case of existing large azimuth misalignment, and in the same conditions, the alignment speed of the improved method is faster than that of the conventional one. [ABSTRACT FROM AUTHOR]

0.91K0.47Na0.47Li0.06NbO3-0.09NaSbO3 lead-free piezoelectric ceramics were prepared at 1000°C using a sintering aid comprising of Cu and Ba in a molar ratio of 71.5/28.5. A dense structure with a high density of 4.43 g/cm3 was obtained for the ceramic added with 2.5 wt% of the sintering aid. Probably due to the smaller grains and doping of Cu2+, the piezoelectric coefficient and dielectric loss were reduced to 120 pC/N and 1.0%, respectively. The ceramics were then fabricated into vibratory gyro sensors of dimensions 0.6 mm × 0.6 mm × 4 mm; and good sensitivity (~0.7 mV/dps) was obtained in the range of −360 to 360 dps. [ABSTRACT FROM AUTHOR]

A new method for calculating space vehicle (SV) attitude controls ensuring their effective implementation by a system of collinear pairs of single-gimbal forced unrestrained gyros (gyrodynes) has been proposed. The novelty of the method consists in a virtual kinematic configuration of the gyro system, i.e., the precession of gyro units in the collinear pairs of gyrodynes is coupled in a nonmechanical manner. In addition, the angular momentum of the system as a state variable for describing the dynamics of the SV permanent rotation was used for the first time at the stage of computing controls performed nonstop by gyrodynes. In the general formulation, when the desired final state of the SV is arbitrary, the SV attitude control problem can be reduced to a sequence of permanent rotations. The performance of the method is demonstrated as applied to the calculation of program gyrodyne controls with a permanent reduction in the SV angular velocity around its center of mass with a nonzero SV angular momentum after its discharge. [ABSTRACT FROM AUTHOR]

In tokamak plasmas, it is recognized that ITG (ion temperature gradient instability) and trapped electron modes (TEM) are held responsible for turbulence giving rise to anomalous transport. The present work focuses on the building of a model including trapped kinetic ions and trapped kinetic electrons. For this purpose, the dimensionality is reduced by averaging the motion over the cyclotron motion and the 'banana' orbits, according to the fact that the instabilities are characterized by frequencies of the order of the low trapped particle precession frequency. Moreover, a set of action-angle variables is used. The final model is 4D (two-dimensional phase space parametrized by the two first adiabatic invariants namely the particle energy and the trapping parameter). In this paper, the trapped ion and electron modes (TIM and TEM) are studied by using a linear analysis of the model. This work is currently performed in order to include trapped electrons in an existing semi lagrangian code for which TIM modes are already taken into account. This study can be considered as a first step in order to include kinetic trapped electrons in the 5D gyrokinetic code GYSELA [J. Abiteboul et al., ESAIM Proc. 32, 103 (2011)]. [ABSTRACT FROM AUTHOR]

Conventional strapdown gyrocompass alignment methods are based on the assumption that the fiber-optic-gyro inertial navigation system has a small azimuth misalignment angle. A large azimuth misalignment angle would lead to an extension of the alignment duration. A time-varying gyrocompass alignment method to solve this problem is provided. An appropriate parameter setting is given for the gyrocompass alignment with a large misalignment angle. Also, a proper protocol for a parametric switch is derived. Simulation and trail results show that the proposed method has better alignment performance than conventional ones, as the system has large misalignment angles. [ABSTRACT FROM AUTHOR]

Inspired by the alignment mechanism of Octans, an initial alignment method for strapdown gyrocompass is designed based on gravitational apparent motion in inertial frame. In this method, the gyro outputs are used to trace the body frame and the measurement from accelerometers are projected to the inertial frame to form the track of gravitational apparent motion. According to the calculations on the vectors involved in this track, the attitude matrix between the inertial frame and navigation frame can be obtained and further alignment can be finished. In order to identify the true gravitational apparent motion from the accelerometer measurement containing random noise as well as to avoid the collinear of vectors in vector operation, a reconstruction algorithm concerning parameter identification and reconstruction of apparent motion is devised and simulated. Simulation and turntable test show that the proposed alignment method can realize self-alignment in a swinging condition. The alignment accuracy is able to reach the theoretical one determined by sensor errors and no external information is needed. [ABSTRACT FROM AUTHOR]

The present article introduces the development of a corrected gyrocompass with an automatic switch of the gyrocompass into the gyroazimuth mode. The issues of multi-criterion synthesis of the gyrocompass control loop have been studied. The necessity of temporary delay input (with selected values) under the previously mentioned switching is shown. On the basis of given requirements, we chose the parameters which provide the device with a switching-back into the gyrocompass mode under any initial gyrocompass deviations in the horizontal plane. An algorithm of gyrocompass ballistic deviation compensation due to the amendment generated by the special observing device, without recourse to external information regarding the ship's acceleration, was developed. [ABSTRACT FROM PUBLISHER]

Highlights: [•] We proposed the optimal AFSA according to the optic gyrocompass IMU parameters identification. [•] We supplied a novel re-calibration method to the marine navigation system. [•] Experiments tested and verified the optic gyrocompass accuracy and reliability requirements with AFSA. [•] Experiments results demonstrated that the AFSA is much less costly and workload reduce. [•] The AFSA can substitute the conventional indoor IMU calibration method to some extent. [ABSTRACT FROM AUTHOR]

This paper aims to propose a new strapdown fiber optic gyrocompass (strapdown FOGC) using adaptive network-based fuzzy inference system (ANFIS). The strapdown FOGC is based on the principle of strapdown inertial navigation system and utilizes electromagnetic log (EM log) and damping equalizer to bound oscillatory errors existing in attitude and heading. As the introduction of damping technique, extra errors are aroused by EM log errors. To decrease the extra errors, ANFIS is utilized to adjust the damping ratio automatically in terms of the ship maneuver conditions. The simulation and trial results indicate that, compared with the conventional gyrocompass scheme, the proposed one can reduce the attitude and heading errors and improve the system performance effectively. [ABSTRACT FROM AUTHOR]

An improved method of gyrocompass alignment for strap-down inertial navigation system (SINS) on moving base assisted with Doppler velocity log (DVL) is proposed in this paper. After analyzing the classical gyrocompass alignment principle on static base, implementation of compass alignment on moving base is given in detail. Furthermore, based on analysis of velocity error, latitude error, and acceleration error on moving base, two improvements are introduced to ensure alignment accuracy and speed: (1) the system parameters are redesigned to decrease the acceleration interference and (2) a data repeated calculation algorithm is used in order to shorten the prolonged alignment time caused by changes in parameters. Simulation and test results indicate that the improved method can realize the alignment on moving base quickly and effectively. [ABSTRACT FROM AUTHOR]

The main objective of this paper is the study of a FDIR for an IMU aiming at space applications with focus on the gyro signal analysis and the tests of the filtering algorithms. The algorithms have been tested by using lab data provided by the DMC LABSIM (Physical's Simulation Laboratory of the Space Mechanics and Control Division of INPE). The results have demonstrated good agreement with the concepts applied in this study. Automatic detection procedures are very important in the characterization of occurrence, definition of criteria, and device types in the scenario of AOCS FDIR. An IMU comprised of four gyros in a tetrahedral configuration is one of the assumed components for the AOCS (attitude and orbit control subsystem) considered in this work. The types of failures considered in this paper are the step abrupt change, ramp/drift/slow, stuck, cyclic, erratic, spike, and finally the stuck for variance alteration noise. An appropriate algorithm for the automatic detection of each type of fault is developed. The approach includes the mapping capability of fault event indicators to the IMU. This mapping is very important in the characterization of the occurrence, definition of criteria, and device types as well as associated fault identification for an AOCS. [ABSTRACT FROM AUTHOR]

North-finding based on micromachined gyroscopes is an attractive possibility. This paper analyzes north-finding methods and demonstrates a measured 4 mrad standard deviation azimuth uncertainty using an in-house developed vibratory silicon MEMS quadruple mass gyroscope (QMG). We instrumented a vacuum packaged QMG with isotropic Q-factor of 1.2 million and Allan deviation bias instability of 0.2^\circ/hr for azimuth detection by measuring the earth's rotation. Continuous rotation (“carouseling”) produced azimuth datapoints with uncertainty diminishing as the square root of the number of turns. Integration of 100 datapoints with normally distributed errors reduced uncertainty to 4 mrad, beyond the noise of current QMG instrumentation. We also implemented self-calibration methods, including in-situ temperature sensing and discrete \pm180^\circ turning (“maytagging” or two-point gyrocompassing) as potential alternatives to carouseling. While both mechanizations produced similar azimuth uncertainty, we conclude that carouseling is more advantageous as it is robust to bias, scale-factor, and temperature drifts, although it requires a rotary platform providing continuous rotation. Maytagging, on the other hand, can be implemented using a simple turn table, but requires calibration due to temperature-induced drifts. \hfill[2012\-0378] [ABSTRACT FROM PUBLISHER]

We present a method for determining the phase and contrast of a single shot of an atom interferometer. The application of a phase shear across the atom ensemble yields a spatially varying fringe pattern at each output port, which can be imaged directly. This method is broadly relevant to atom-interferometric precision measurement, as we demonstrate in a 10 m 87Rb atomic fountain by implementing an atom-interferometric gyrocompass with 10 mdeg precision. [ABSTRACT FROM AUTHOR]