Electrostatic Gyroscope Research Articles

Design of a magnetic torquing system for an ESG north finder

This paper describes the design and experimental investigation of a magnetic torquing system for a strapdown north finder using an electrostatic gyroscope (ESG). The specially designed magnetic torquing system consists of 3 pairs of coils, which are located symmetrically around the gyro rotor. The supporting electronics consists of a rotor speed regulator, radial null control and torque rebalancing circuit and a current stabilizer of Z-coils. The system generates orthogonally distributed magnetic fields and ensures a linear controllable torque along the X- and Y-coils. When the spin axis of the gyro rotor has been aligned along the local vertical, the azimuth can be obtained by measuring the equilibrium torque on the gyro rotor. Experimental results show that the ESG north finder with the special magnetic torquing system provides a north-seeking accuracy of 10" (1/spl sigma/) with a measurement time less than 30 min.

Design of an electrostatic suspension system with minimum electric disturbing torque - for precision electrostatic gyroscopes

An electrostatic gyroscope (ESG) requires an electrostatic suspension system (ESS) to keep its rotor suspended in a vacuum cavity. The conventional ESS operates with high standing voltage on opposing electrodes that causes a large electric disturbing torque (EDT) applied to the gyro rotor, with consequent loss of accuracy. In the newly-designed ESS the suspension voltage is applied to one electrode only, whilst the opposing electrode is kept at zero potential. With no standing voltage the EDT is kept to a minimum. The new system has an inherent square-root compensation. Theoretical analysis and computer simulations show that the new system meets the requirements for marine applications.

Electrostatic suspension system with sliding mode control

Two aspects must be considered in selecting the preload of electrostatic suspension system (ESS) for the electrostatic gyroscope (ESG), both the required load capacity and the tolerable electrical disturbing torques exerted on the rotor. By means of sliding mode control (SMC), ESS may operate in three modes: (1) two-sided linear suspension (2) single-sided nonlinear suspension, and (3) single-sided suspension with nonlinearity compensation. Therefore a low preload can be selected for reducing both the electrical disturbing torques and the power consumption, meanwhile ensuring the required load capacity. It has been proven by experiments that the ESS with 2 g preload can bear overload acceleration up to 6 g successfully.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Electrostatic disturbance forces on a three-axis drag-free sensor

The electrostatic analysis of a multiple-capacitance 3-axis drag-free sensor is presented in this paper. The instrument consists of a proof-mass (a dense metallic ball) floating freely inside a spherical cavity enclosed by the sensor plates and the shield. Since the ball and the cavity are not necessarily concentric, the problem in three-dimensional potential theory for electrostatics is solved by the method of boundary perturbations and specifically in terms of spherical harmonics. The capacitance outputs of the instrument and the electrostatic forces acting on the system are derived as non-linear functions of the ball position, ball charge and the sensor plate potentials. The instrument sensitivity and cross-coupling effects are discussed. The analysis may also be useful for electrostatic gyros and suspensions.

Gravity measurements in an airplane using state‐of‐the‐art navigation and altimetry

In 1976 the U. S. Naval Oceanographic Office made experimental gravity measurements over the Atlantic in an airplane using a LaCoste and Romberg shipboard gravity meter, a Honeywell electrostatic gyro inertial system, a Rosemont pressure port altimeter, a Honeywell radar altimeter, Loran C and other electronic navigational aids. Preliminary results were reported at the 47th Annual International SEG Meeting in Calgary, Canada, in 1977. These preliminary results were compared with sea gravity data furnished by the Naval Oceanographic Office and were found to be in general agreement. However, there were some unexplained systematic errors of about 15 mgal and the airplane gravity profiles were considerably more noisy than helicopter gravity profiles reported by William Gumert (1977, personal communication). After the paper was given, we found that corrections for Schuler oscillations in the inertial system significantly reduced the systematic errors. We also found that by making full use of a half‐second sampling rate of the radar altimeter, we could make meaningful vertical acceleration corrections relative to sea level as well as relative to an atmospheric pressure surface. A comparison of the two corrections showed that variations in the isobaric surfaces were the main cause of the noise in the airplane gravity profiles. It also became apparent that the noise could be reduced by flying slower or making successive flights at different speeds.

Similarities Between Classical Celestial Navigation and Electrostatic Gyro Navigation

In the absence of torque, a gyroscope's spin axis will maintain a fixed angular orientation in space. This angular orientation is analogous to the fixed line of sight to a star. In principle then, one should be able to perform celestial navigation using gyroscopes as self-contained stars. Unfortunately, most current inertial auto-navigators apply torques to the gyroscopes. Ideally these torques are of just the right magnitude to cause the stable platform on which the gyros are mounted to stay locally level. In the case of strapdown inertial auto-navigators, the gyroscopes are torqued to follow the host vehicle angular rates. This results in the gyroscope becoming just an angular rate sensor, and the only measure of true angular orientation rests within the system computer. These mechanizations lead to concepts unfamiliar to many navigators familiar with celestial navigation. Electrostatic gyroscope (ESG) inertial navigation systems are unique in that they are normally operated untorqued. As such, the orientation of their gyro spin axes remain fixed in inertial space. This makes it possible to consider their operation in terms of classical celestial navigation concepts. This paper will develop this similarity to the point where one familiar with celestial navigation will be able to understand the alinement problem and the fundamental error sources of ESG inertial systems. A specific type of ESG employed at Rockwell International in both gimbaled and strap-down systems will be discussed. This will provide the basis for relating angle readout errors and drift rate to their counterparts in celestial navigation. The buzz words used in inertial navigation, such as Schuler tuning and Kalman filtering, will be related to concepts familiar to celestial navigators. The paper will be based on straightforward physical principles and the concepts presented without resorting to mathematical development.

High-Accuracy Calibration of Electrostatic Gyro Strapdown Navigation Systems

A one-half order of magnitude accuracy improvement is obtained for an electrostatic gyro strapdown navigation system using a high-accuracy calibration technique. The system achieves cancellation of instrument errors by rotating the instrument cluster. The instrument errors that do not cancel out with rotation are modeled in a rotated function space. The coefficients of the rotated function space are obtained with a calibration that uses Kalman filtering. These are used to update the instrument model coefficients in a nonrotated function space. Flight test results are presented that show navigation accuracy with and without a high-accuracy calibration.