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Objective: The experiments investigated the "old issue" of the attitude indicator's moving-horizon versus moving-aircraft format with current primary flight display technology. Of interest was whether the effects found in earlier studies, favoring the moving-aircraft format, could be replicated with most recent technology including extended horizon displays, which depict the artificial horizon extended over the whole screen with overlaying speed and altitude scales (e.g., B787). Background: Although the moving-horizon format represents the standard approach in Western aviation, human factors research from the 1950s to the 1970s with round electromechanical instruments favored the moving-aircraft format with respect to better support of flight-path tracking and unusual attitude recoveries. However, recent studies using laboratory displays more similar to modern primary flight displays provided inconsistent results. This led to the assumption that the display's design is a moderating factor of those effects. Method: Thirty-two novices and 13 pilots flew several tracking and recovery tasks in a PC-based simulator equipped with moving-horizon and movingaircraft formats in classic and extended horizon design. Results: The data show that the previous effects favoring a moving-aircraft format of displaying bank information can be replicated with current primary flight display designs. However, the extended horizon design seems to reduce this effect, at least for pilots. Conclusion: The results suggest reconsidering the format of the attitude indicator at least for new applications, such as control of remotely piloted aircraft. [ABSTRACT FROM AUTHOR]

Control Moment Gyro (CMG) and Reaction Wheel (RW) generally serve in different spacecraft control tasks due to their unique characteristics, such as large output torque and control accuracy, respectively. The major concerns in using of CMG and RW are singularity and saturation, which could make spacecraft uncontrollable. RW as singularity escape equipment is adopted to construct hybrid actuator system named CMG & RW (CMGRW) to enhance and improve the spacecraft attitude performance as well as the CMG's. First, the attitude dynamic model of the spacecraft equipped with hybrid actuators is established and the corresponding singularity is analyzed thoroughly. Then null motion in CMGRW is further argued and proved feasible for both elliptical and hyperbolic singularities escape. A new performance index in terms of CMG and RW state is proposed, followed by a steering logic using gradient method with a feasible null motion vector to drive the hybrid actuator system to feasible states. Numerical simulations with initial conditions considering CMG singularity and RW saturation are selected to demonstrate the excellent performance of the hybrid actuators during the entire large angle agile maneuvering process, resulting in a group of feasible final states of the CMGRW that serves as great initial conditions for the next agile maneuvering. [ABSTRACT FROM AUTHOR]

This paper reports a more complete description of the design process of the Center Support Quadruple Mass Gyroscope (CSQMG), a gyro expected to provide breakthrough performance for flat structures. The operation of the CSQMG is based on four lumped masses in a circumferential symmetric distribution, oscillating in anti-phase motion, and providing differential signal extraction. With its 4-fold symmetrical axes pattern, the CSQMG achieves a similar operation mode to Hemispherical Resonant Gyroscopes (HRGs). Compared to the conventional flat design, four Y-shaped coupling beams are used in this new pattern in order to adjust mode distribution and enhance the synchronization mechanism of operation modes. For the purpose of obtaining the optimal design of the CSQMG, a kind of applicative optimization flow is developed with a comprehensive derivation of the operation mode coordination, the pseudo mode inhibition, and the lumped mass twisting motion elimination. The experimental characterization of the CSQMG was performed at room temperature, and the center operation frequency is 6.8 kHz after tuning. Experiments show an Allan variance stability 0.12°/h (@100 s) and a white noise level about 0.72°/h/√Hz, which means that the CSQMG possesses great potential to achieve navigation grade performance. [ABSTRACT FROM AUTHOR]

The basic principle of an angle measuring system using the fiber optic gyroscope (FOG) was introduced. The misalignment angle error of this system was analyzed theoretically. A tilt sensor for accurate measurement of the inclination angle was proposed for compensating this gyro misalignment angle. Experimental results showed that this method was effective for reducing the systematic error. [ABSTRACT FROM AUTHOR]

The noncomplete compensated calibration errors of a fiber optic gyro (FOG) can remain in the navigation stage, leading to decreased navigation accuracy. A new approach is presented to calibrate the FOG drift and scale factor error based on a double calculating program. Using an analysis of the relationship between the FOG error and misalignment, a FOG calibration error model is derived, and a three-step six-position calibration path is analyzed. In this method, the FOG drift and scale factor error are calculated from two groups of attitude information, which are resolved, respectively, from calculating programs A and B in the navigation computer. The input signal of these two calculating programs is measured from one FOG. Its effectiveness is demonstrated by simulation and turntable experiments. The results show that this method can further compensate the residual calibration errors with misalignments, thereby improving the FOG calibration accuracy. [ABSTRACT FROM AUTHOR]

Integrating the advantage of magnetic bearings with a double gimble control moment gyroscope (DGCMG), a magnetically suspended DGCMG (MSDGCMG) is an ideal actuator in high-precision, long life, and rapid maneuver attitude control systems. The work presented here mainly focuses on performance testing of a MSDGCMG independently developed by Beihang University, based on the single axis air bearing table. In this paper, taking into sufficient consideration to the moving-gimbal effects and the response bandwidth limit of the gimbal, a special MSDGCMG steering law is proposed subject to the limits of gimbal angle rate and angle acceleration. Finally, multiple experiments are carried out, with different MSDGCMG angular momenta as well as different desired attitude angles. The experimental results indicate that the MSDGCMG has a good gimbal angle rate and output torque tracking capabilities, and that the attitude stability with MSDGCMG as actuator is superior to 10-3°/s. The MSDGCMG performance testing in this paper, carried out under moving-base condition, will offer a technique base for the future research and application of MSDGCMGs. [ABSTRACT FROM AUTHOR]

A fast global motion estimation algorithm is proposed by employing the gyro with ordinary precision to sense the camera status. Firstly gyro is used to sense the jitter of camera system, and the bearings (quadrant) of video jitter are achieved from the gyro output. Secondly, singular points of local motion vector are filtered using the acquired direction and position as the reference. Finally, global motion parameters are worked out using the least square method (LS). Experimental result shows that this algorithm has the advantages of fast operation, high accuracy of motion estimation and low precision requirement of gyro. Also it could effectively filter singular points stemming from either interference of local motion or error of calculation [ABSTRACT FROM AUTHOR]

Earlier work based on nonlinear guiding center (NLGC) theory suggested that perpendicular cosmic-ray transport is diffusive when cosmic rays encounter random three-dimensional magnetohydrodynamic turbulence dominated by uniform two-dimensional (2D) turbulence with a minor uniform slab turbulence component. In this approach large-scale perpendicular cosmic-ray transport is due to cosmic rays microscopically diffusing along the meandering magnetic field dominated by 2D turbulence because of gyroresonant interactions with slab turbulence. However, turbulence in the solar wind is intermittent and it has been suggested that intermittent turbulence might be responsible for the observation of "dropout" events in solar energetic particle fluxes on small scales. In a previous paper le Roux et al. suggested, using NLGC theory as a basis, that if gyro-scale slab turbulence is intermittent, large-scale perpendicular cosmic-ray transport in weak uniform 2D turbulence will be superdiffusive or subdiffusive depending on the statistical characteristics of the intermittent slab turbulence. In this paper we expand and refine our previous work further by investigating how both parallel and perpendicular transport are affected by intermittent slab turbulence for weak as well as strong uniform 2D turbulence. The main new finding is that both parallel and perpendicular transport are the net effect of an interplay between diffusive and nondiffusive (superdiffusive or subdiffusive) transport effects as a consequence of this intermittency. [ABSTRACT FROM AUTHOR]

Abstract: A simulator study has been conducted demonstrating a positive effect on airsickness by utilizing a 3D artificial Earth-fixed visual pattern. Participants were exposed to the same turbulent physical aircraft motion in a simulator three times in a row, each time using a different visual cue. In one condition only the interior of the simulator cabin was visible. In another condition an Earth-fixed star field moving opposite the simulator cabin was projected in front of the participant. In a third condition the same star field was used, however with additional anticipatory information by means of a rollercoaster like track showing the trajectory to go. Participants were asked for their misery and joyfulness ratings at fixed time instants using an 11-points misery scale (no problems–vomiting) and joyfulness scale (unpleasant–pleasant). The results showed that viewing an Earth-fixed visual frame moving instantaneously opposite the cabin motion did reduce motion sickness significantly by a factor of 1.6, thereby improving comfort. This condition could be applied in air transport, where often a monitor is available in the back of the seat ahead. The largest effect, i.e., a reduction by a factor of 4.2 was realized by adding anticipatory information. Although it is not possible to predict the effect of turbulence on the aircraft motion yet, an anticipatory display might already be applicable in other domains, such as at sea by using a wave radar and a ship motion model. [Copyright &y& Elsevier]

Stability theorems for gyroscopic systems with integral correction under dissipative and nonconservative positional forces are proved. An inertial vertical gyro is used as an example to illustrate the results obtained [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an algorithm for controlling vibratory MEMS gyroscopes so that they can directly measure the rotation angle without integration of the angular rate, thus eliminating the accumulation of numerical integration errors incurred in obtaining the angle from the angular rate. The proposed control algorithm consists of a weighted energy control and a mode tuning control. The weighed energy control compensates unequal damping terms and keeps the amplitude of oscillation constant in an inertial frame by maintaining the prescribed total energy. The mode tuning control continuously tunes mismatches in spring stiffness in order to maintain a straight line of oscillation for the proof mass. The simulation results demonstrate the feasibility of the control algorithm and the viability of the concept of using a vibratory gyroscope to directly measure rotation angle. [Copyright &y& Elsevier]

An attitude determination and in-flight calibration extended Kalman filter and the corresponding smoother have been developed to estimate three-axis attitude of spinning sounding rockets. The attitude determination system uses low-accuracy commercial microelectromechanical system rate gyros, coupled with a three-axis magnetometer and a one-axis sun sensor. Because only postflight analysis is necessary, the improved performance of a smoother is used in the attitude reconstruction because postflight computation allows the use of a noncausal algorithm. Gyro misalignment and scale-factor errors are proportional to the angular rate, and spin-stabilized rockets without a despin unit usually have a large angular velocity in the range of 4-6 cycles per second about the spin axis. Therefore, gyro misalignment and scale-factor errors can have a significant effect on the attitude propagation, which is based on the gyro measurements. In this work, in-flight calibration is carried out, estimating sensor relative misalignments in addition to bias and scale-factor errors. To ensure filter convergence, an initialization algorithm suitable for producing an initial attitude estimate from a vector measurement and a scalar measurement has been developed. The initialization algorithm uses an attitude representation based on the minimum quaternion combined with a search method. The filter and smoother have been tested using a truth-model simulation, and the accuracy is shown to be dependent on the rocket motion. A rich motion time history makes the parameters more observable and thereby the estimates more accurate. Simulation results indicate that an attitude accuracy on the order of 0.5-1 degrees (3 sigma) can be achieved with a low-cost suite of sensors. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the use of an Artificial Neural Network (ANN) for the assessment of fall-risk (FR) in patients with different neural pathologies. The assessment integrates a clinical tool based on a wearable device (WD) with accelerometers (ACCs) and rate gyroscopes (GYROs) properly suited to identify trunk kinematic parameters that can be measured during a posturography test with different constraints. Our ANN – a Multi Layer Perceptron Neural Network with four layers and 272 neurones – shows to be able to classify patients in three well-known fall-risk levels. The training of the neural network was carried on three groups of 30 subjects with different Fall-Risk Tinetti scores. The validation of our neural network was carried out on three groups of 100 subjects with different Fall-Risk Tinetti scores and this validation demonstrated that the neural network had high specificity (≥0.88); sensitivity (≥0.87); area under Receiver-Operator Characteristic Curves (>0.854). [Copyright &y& Elsevier]

The motion of a conventional force-balancing-controlled gyroscope in a mode-matched operation does not have sufficient persistence of excitation, and as a result, all major fabrication imperfections cannot be identified and compensated for. This paper presents an adaptive force-balancing control for a microelectromechanical-system z-axis gyroscope using a trajectory-switching algorithm. The proposed adaptive force-balancing control supplies additional richness of excitation to the internal dynamics of the gyroscope by switching the trajectory of the proof mass of the gyroscope, and it provides quadrature compensation, drive- and sense-axis frequency tuning, and closed-loop identification of the angular rate without the measurement of input/output phase difference. This algorithm also identifies and compensates the cross-damping terms which cause zero-rate output. [ABSTRACT FROM AUTHOR]

Mathematical models of vibration gyroscopes of different types at the constant and harmonically changing angular velocity of the base were generalized. Conditions under which the vibration gyroscope becomes a turn of base indicator in the inertial space were researched. Characteristics of a gyroscope as a sensor of angular velocity were investigated. Gain and phase frequency characteristics of an angular velocity sensor at the harmonic angular velocity of translation were obtained. Expressions for the dynamic error of the system were obtained. The equivalent mathematical model of the vibration gyroscope as a structural unit of the control or navigation system was proposed. [ABSTRACT FROM AUTHOR]

An analysis is presented in this paper for a two-axis rate gyro subjected to linear feedback control mounted on a space vehicle, which is spinning with uncertain angular velocity ωz(t) about its spin of the gyro. For the autonomous case in which ωz(t) is steady, the stability analysis of the system is studied by Routh–Hurwitz theory. For the non-autonomous case in which ωz(t) is sinusoidal function, this system is a strongly non-linear damped system subjected to parametric excitation. By varying the amplitude of sinusoidal motion, periodic and chaotic responses of this parametrically excited non-linear system are investigated using the numerical simulation. Some observations on symmetry-breaking bifurcations, period-doubling bifurcations, and chaotic behavior of the system are investigated by various numerical techniques such as phase portraits, Poincare´ maps, average power spectra, and Lyapunov exponents. In addition, some discussions about chaotic motions of this system can be suppressed and changed into regular motions by a suitable constant motor torque are included. [Copyright &y& Elsevier]

The green flash is a well-known but elusive atmospheric phenomenon, in which the Sun is observed as it is setting behind a clear horizon. At the last moment before its disc disappears, a green flash is observed. The phenomenon is due to a vertical structure in the atmospheric refractive index which disperses the Sun’s light. We have simulated similar conditions in the laboratory, using a refractive index gradient in salt water in an aquarium. We photographed a white LED source simulating the Sun with an artificial horizon, and a blue flash was observed as the horizon obscured the image. Using the same system, we were also able to create a nonlinear refractive index profile and observe amplified mirage flashes, which are those normally observed in nature. We measured the refractive index gradient in the water with an Abbe refractometer. [ABSTRACT FROM AUTHOR]