Array Of Gyroscopes Research Articles

Possible Tests of Fundamental Physics with GINGER

The GINGER (gyroscopes in general relativity) project foresees the construction of an array of large frame ring laser gyroscopes, rigidly connected to the Earth. Large frame ring laser gyroscopes are high-sensitivity instruments used to measure angular velocity with respect to the local inertial frame. In particular, they can provide sub-daily variations in the Earth rotation rate, a measurement relevant for geodesy and for fundamental physics at the same time. Sensitivity is the key point in determining the relevance of this instrument for fundamental science. The most recent progress in sensitivity evaluation, obtained on a ring laser prototype, indicates that GINGER should reach the level of 1 part in 1011 of the Earth’s rotation rate. The impact on fundamental physics of this kind of apparatus is reviewed.

Intersatellite and Downlink Agile Attitude Maneuvers

This research is focused on the problem of agile attitude maneuvering, aimed at the precise pointing of a satellite forming a typical constellation in low Earth orbit. We consider two different operational scenarios: (a) pointing toward a specific ground station, located on the Earth surface (for downlink data routing), and (b) pointing toward a companion satellite (for establishing an intersatellite connection). The two preceding operational requirements can both be formulated as attitude tracking problems. In this study, we use an inertia-free nonlinear attitude control algorithm based on rotation matrices and possessing remarkable stability properties, in conjunction with a pyramidal array of single-gimbal control momentum gyroscopes. Numerical simulations, in both nominal and nonnominal flight conditions, demonstrate that the attitude control architecture proposed in this work is effective for the purpose of performing agile attitude maneuvering, aimed at precise pointing during downlink and intersat data routing.

Scale-Wise Variance Minimization for Optimal Virtual Signals: An Approach for Redundant Gyroscopes

The increased use of low-cost gyroscopes within inertial sensors for navigation purposes, among others, has brought to the development of a considerable amount of research in improving their measurement precision. Aside from developing methods that allow to model and account for the deterministic and stochastic components that contribute to the measurement errors of these devices, an approach that has been put forward in recent years is to make use of arrays of such sensors in order to combine their measurements thereby reducing the impact of individual sensor noise. Nevertheless combining these measurements is not straightforward given the complex stochastic nature of these errors and, although some solutions have been suggested, these are limited to certain specific settings which do not allow to achieve solutions in more general and common circumstances. Hence, in this work we put forward a non-parametric method that makes use of the wavelet cross-covariance at different scales to combine the measurements coming from an array of gyroscopes in order to deliver an optimal measurement signal without needing any assumption on the processes underlying the individual error signals. As a result of this work we also study an appropriate non-parametric approach for the estimation of the asymptotic covariance matrix of the wavelet cross-covariance estimator which has important applications beyond the scope of this work. The theoretical properties of the proposed approach are studied and are supported by simulations and real applications, indicating that this method represents an appropriate and general tool for the construction of optimal virtual signals that are particularly relevant for arrays of gyroscopes. Moreover, the results of this work can support the creation of optimal signals for other types of inertial sensors other than gyroscopes as well as for redundant measurements in other domains other than navigation.

Length measurement and stabilization of the diagonals of a square area laser gyroscope

Large frame ring laser gyroscopes are top sensitivity inertial sensors able to measure absolute angular rotation rate below prad s−1 in few seconds. The GINGER project is aiming at directly measuring the Lense–Thirring effect with an 1% precision on an Earth based experiment. GINGER is based on an array of large frame ring laser gyroscopes. The mechanical design of this apparatus requires a micrometric precision in the construction and the geometry must be stabilized in order to keep constant the scale factor of the instrument. The proposed control is based on square cavities, and relies on the length stabilization of the two diagonals, which must be equal at micrometric level. GP2 is the prototype devoted to the scale factor control test. As a first step, the lengths of the diagonals of the ring cavity have been measured through an interferometric technique with a statistical accuracy of some tens of nanometers, and they have been locked to the wavelength of a reference optical standard. Continuous operation has been obtained over more than 12 h, without loss of sensitivity. GP2 is located in a laboratory with standard temperature stabilization, with residual fluctuations of the order of 1 °C. Besides the demonstration of the control effectiveness, the analysis of the Sagnac frequency demonstrates that relative small and low-cost ring lasers (around one meter of side) can also achieve a sensitivity of the order of nrad s−1 in the range 0.01–10 Hz in a standard environment, which is the target sensitivity in many different applications, such as rotational seismology and next generation gravitational waves detectors.

Sagnac gyroscopes, GINGERINO, and GINGER

GINGER (Gyroscopes IN GEneral Relativity), based on an array of large dimension ring laser gyroscopes, is aiming at testing on Earth General Relativity effects, like the gravito-electric and gravito-magnetic effects (also known as De Sitter and Lense-Thirring effects) and the Lorentz violation. The sensitivity is a function of the size and of the losses of the ring laser optical cavity. In this kind of measurement long term stability is matter of concern, and underground location is desirable for its natural thermal stability and for being isolated from atmospheric disturbances. Considering the present sensitivity of the RLG prototype GINGERINO, and assuming total losses of 6 ppm, a 40 m perimeter and 1 day of integration time, a sensitivity of the order of frad/s could be achieved. The construction of GINGER is at present under discussion.

Ring laser gyroscopes in the underground Gran Sasso Laboratories

Gyroscopes IN GEneral Relativity (GINGER) is a proposed experiment with the aim of measuring the gravito-electric (known also as De Sitter effect) and gravito-magnetic effects (or Lense – Thirrings effect) in a ground laboratory, foreseen by general relativity, through an array of large dimension ring laser gyroscopes. The site is located inside the Gran Sasso laboratories (LNGS) of INFN, under more than one thousand meter underground, well protected from surface perturbations. GINGERINO is a square ring-laser prototype with 3.6 m side, which has been built to investigate the level of noise of this site. GINGERINO has already completed its task, showing the advantage of the underground location. It cannot reach the sensitivity suitable for the fundamental physics measurements, but it can provide important data for geophysics and seismology. Its high sensitivity in the frequency band of fraction of Hz and its location in a seismically active area make it suitable for seismology studies. It recorded a sequence of central Italy earthquakes in the autumn of 2016 and many other events both from near field and from far field. The analysis of 90 days of continuous operation shows that its duty cycle is higher than 95 %, with a quantum shot noise limit of the order of 10−10 rad s−1 Hz−1/2.

Analysis of 90 day operation of the GINGERINO gyroscope.

Gyroscopes IN GEneral Relativity (GINGER) is a proposed experiment with the aim of measuring in a ground laboratory the gravitoelectric and gravitomagnetic effects foreseen by general relativity through an array of ring laser gyroscopes. GINGERINO is a square ring-laser prototype that has been built to investigate the level of noise inside the Gran Sasso underground laboratory. GINGERINO has shown the advantage of the underground location. Now it provides suitable data for geophysics and seismology. Since May 2017, it has continuously acquired data. The analysis of the first 90 days shows that the duty cycle is higher than 95%, and the quantum shot noise limit is of the order of 10-10(rad/s)/Hz. It is located in a seismically active area, and it recorded part of the central Italy earthquakes. Its high sensitivity in the frequency band of fraction of hertz makes it suitable for seismology studies. The main purpose of the present analysis is to investigate the long-term response of the apparatus. Simple and fast routines to suppress the disturbances coming from the laser have been developed. The Allan deviation of the raw data reaches some 10-6 after about 106 s of integration time, while the processed data show an improvement of 1 order of magnitude. Disturbances at the daily time scale are present in the processed data, and the expected signal induced by polar motion and solid Earth tides is covered by those disturbances.

A Hamiltonian approach to model and analyse networks of nonlinear oscillators: Applications to gyroscopes and energy harvesters

Over the past twelve years, ideas and methods from nonlinear dynamics system theory, in particular, group theoretical methods in bifurcation theory, have been used to study, design, and fabricate novel engineering technologies. For instance, the existence and stability of heteroclinic cycles in coupled bistable systems has been exploited to develop and deploy highly sensitive, low-power, magnetic and electric field sensors. Also, patterns of behaviour in networks of oscillators with certain symmetry groups have been extensively studied and the results have been applied to conceptualize a multifrequency up /down converter, a channelizer to lock into incoming signals, and a microwave signal generator at the nanoscale. In this manuscript, a review of the most recent work on modelling and analysis of two seemingly different systems, an array of gyroscopes and an array of energy harvesters, is presented. Empirical values of operational parameters suggest that damping and external forcing occur at a lower scale compared to other parameters, so that the individual units can be treated as Hamiltonian systems. Casting the governing equations in Hamiltonian form leads to a common approach to study both arrays. More importantly, the approach yields analytical expressions for the onset of bifurcations to synchronized oscillations. The expressions are valid for arrays of any size and the ensuing synchronized oscillations are critical to enhance performance.

Interferometric length metrology for the dimensional control of ultra-stable ring laser gyroscopes

We present the experimental test of a method for controlling the absolute length of the diagonals of square ring laser gyroscopes. The purpose of this is to actively stabilize the ring cavity geometry and to enhance the rotation sensor stability in order to reach the requirements for the detection of the relativistic Lense–Thirring effect with a ground-based array of optical gyroscopes. The test apparatus consists of two optical cavities 1.32 m in length, reproducing the features of the ring cavity diagonal resonators of large-frame He–Ne ring laser gyroscopes. The proposed measurement technique is based on the use of a single diode laser, injection locked to a frequency stabilized He–Ne/iodine frequency standard, and a single electro-optic modulator. The laser is modulated with a combination of three frequencies, allowing us to lock the two cavities to the same resonance frequency and, at the same time, to determine the cavity free spectral range (FSR). We obtain a stable lock of the two cavities to the same optical frequency reference, providing a length stabilization at the level of 1 part in , and the determination of the two FSRs with a relative precision of ∼2 · 10−7. This is equivalent to an error of on the absolute length difference between the two cavities.

Dynamics and bifurcations in a [formula omitted]-symmetric Hamiltonian network. Application to coupled gyroscopes

The advent of novel engineered or smart materials, whose properties can be significantly altered in a controlled fashion by external stimuli, has stimulated the design and fabrication of smaller, faster, and more energy-efficient devices. As the need for even more powerful devices grows, networks have become popular alternatives to advance the fundamental limits of performance of individual units. In many cases, the collective rhythmic behavior of a network can be studied through the classical theory of nonlinear oscillators or through the more recent development of the coupled cell formalism. However, the current theory does not account yet for networks in which cells, or individual units, possess a Hamiltonian structure. One such example is a ring array of vibratory gyroscopes, where certain network topologies favor stable synchronized oscillations. Previous perturbation-based studies have shown that synchronized oscillations may, in principle, increase performance by reducing phase drift. The governing equations for larger array sizes are, however, not amenable to similar analysis. To circumvent this problem, the model equations are now reformulated in a Hamiltonian structure and the corresponding normal forms are derived. Through a normal form analysis, we investigate the effects of various coupling schemes and unravel the nature of the bifurcations that lead a ring of gyroscopes of any size into and out of synchronization. The Hamiltonian approach can, in principle, be readily extended to other symmetry-related systems.

Measuring general relativity effects in a terrestrial lab by means of laser gyroscopes

GINGER is a proposed tridimensional array of laser gyroscopes with the aim of measuring the Lense–Thirring effect, predicted by the general relativity theory, in a terrestrial laboratory environment. We discuss the required accuracy, the methods to achieve it, and the preliminary experimental work in this direction.