Gyro Unit Research Articles

Installation angle calibration between the star sensor and gyro unit using the equivalent rotation vector transformation

To improve the dynamic performance of the star sensor, different star image frames are correlated using the attitude-correlated frame (ACF) approach, and the attitude changes among these star image frames are measured by the strapdown gyro unit (GU). The GU consists of three orthogonally assembled gyros, while the accelerometer is excluded. Accurate calibration of the installation angles between the star sensor and the GU is essential for the ACF approach. An installation angle calibration method using the equivalent rotation vector transformation between the star sensor and the GU is proposed in this work. Through three to five maneuverings of the star sensor/GU system, the equivalent rotation vector transformation of the observed vector is performed by the installation matrix, and the optimal values of the installation angles are estimated. Simulations and experiments are designed and conducted, and both verify the proposed calibration method. The calibration results in the experiment show that the standard deviation of the installation angles in each measurement data group is less than 5 arcseconds and the difference between different data sets is less than 14 arcseconds, both for the three axes, which are accurate enough for the ACF approach and other applications.

Attitude Correlated Frames Based Calibration Method for Star Sensors.

Star sensors undergo laboratory calibration before they leave the factory. In addition, recalibration is necessary after they experience vibration, deformation, etc. Using the analysis of attitude-dependent and attitude-independent interstar angular invariance calibration methods (IAICMs) as a reference, an attitude-correlated frame-based calibration method (ACFCM) is proposed in this work, which combines the advantages of both methods. Using outdoor star observations, the ACFCM correlates star image frames obtained at different times via a strapdown gyro unit. As a result, the number of efficient star images for calibration increases rapidly and the distribution of star images becomes much more uniform, thus improving the calibration accuracy of the star sensor. A simulation and experimental tests were designed and carried out. Both the simulation and experimental results verify the feasibility of the proposed ACFCM method. Furthermore, by comparing our method with the IAICMs, the repeatability and reliability of the principal point obtained from the calibration with the ACFCM method proposed in this work were significantly improved.

The Guaranteeing Estimation Method to Calibrate a Gyro Unit

The Guaranteeing Estimation Method to Calibrate a Gyro Unit

A Method of Deflection of the Vertical Measurement Based on Attitude Difference Compensation

To solve the problem of dynamic measurement of deflection of the vertical (DOV) based on the combination of the strapdown inertial navigation system (SINS) and the global navigation satellite system (GNSS), a DOV recovery method based on attitude difference compensation is proposed. The method does not need to model the unknown DOV and avoids the modeling inaccuracy error. Firstly, the attitude angles are estimated by the SINS/GNSS integrated navigation system using Kalman filter. At the same time, the attitude angles are also calculated by integrating the gyro unit of SINS with GNSS. The difference between attitude angles obtained by the two methods is made, and the horizontal attitude difference includes the DOV information and the gyro attitude error with definite characteristics. Then the DOVs in the inertial navigation system are compensated by the horizontal attitude difference with modeled gyro attitude error. The fading memory Kalman filter is used to estimate the attitude angles of INS after DOV compensation, and the attitude angles are taken as the benchmark to make a difference with the attitude angles obtained by SINS/GNSS integrated navigation system. The difference result is the DOVs along the trajectory. In order to find out the optimal fading factor, a traversal search method based on the velocity error of pure inertial solution after DOV compensation is proposed. The shipboard experiment shows that the method can recover the DOVs along the trajectory. After compensation with the recovered DOVs, the positioning error of 21.6-hours pure inertial solution of the SINS is not more than 150 meters, and the positioning accuracy is improved about 6.7 times compared with the Sandwell model compensation.

Multiple antenna gyro-GNSS attitude determination system

Attitude determination system is one of the most important system to control the moving object of any type. GNSS attitude determination systems have been actively developed in the last decade. Such systems have obvious drawbacks associated with the need for the visibility of a sufficient number of satellites. GNSS/Inertial integration is the best way to reduce satellite visibility dependence. The new concept of multiple antenna integrated inertial-satellite system design is proposed. System structure allows to exclude accelerometers from inertial measurement unit replacing it with gyro unit only. An important feature of the system is the availability of the initialization mode in motion and in conditions of limited satellite visibility. System performance was estimated in simulation and car test.

Transient thermal contact in gyro unit–platform assembly

Thermal contact conditions of parts change in time in the process of heating. Cases of thermal contact instability may occur even under constant boundary conditions. This is due to the combination of temperature and strain fields interdependence based on thermal expansion, the influence of shape of parts and the conditions of their connection in the assembly. In this paper, using the example of a model problem of thermal contact of a gyro unit–platform assembly, we study qualitative and quantitative aspects of the temporal behavior of thermal contact conductance. A significant qualitative difference between thermal contact conductance and its steady-state value has been obtained. Given that the magnitude of the deviation is within the acceptable engineering accuracy, it is of interest in terms of thermal contact model development.

Calculation of Program Controls Not Generating Singular States of a Gyro System. II

The paper is devoted to the applied aspect of a new technology for calculating the laws of program controls for the orientation of a spacecraft (SC) [1]. The two-point boundary problem of reorienting a SC by gyrodynes is solved. The results of the numerical implementation of a new method of forming the program laws of reorientation that do not generate singular states of the executive gyro system are presented. The numerical implementation is carried out using the example of a dynamic model of a space telescope with real characteristics and six gyrodynes, which make up three pairs with collinear precession axes. The obtained results demonstrate the principal novelty of the new method of calculating the controls: the calculated laws of the telescope’s guidance lack the singular values of the precession angles of the gyro units of the executive gyrodynes. When the gyro units enter these positions, the space telescope loses controllability and the guidance process is interrupted. The absence of singular positions of gyro unit points guarantees the non-stop execution of the calculated laws with the required accuracy and speed.

Algorithm of Analytical Bank-And-Climb Gyro Unit Without a Heading Gyro

Abstract An analytical bank-and-climb gyro unit supplies the flight crew with information about aircraft angular movement relative to the local vertical. This article describes the particular principles of unit operation providing a step by step explanation of principles governing the operation of the analytical bank-and-climb gyro unit and provides a kinematic scheme of the unit. The article also gives an insight into the occurrence of errors in the bank-and-climb gyro unit as well as explains their significance.

CMGユニットを用いたロープ型宇宙エレベーター実験用クライマーの昇降安定化制御

By using a tether (cable) to link the ground station and the space station at 36,000[km] altitude, a space elevator is envisioned where transportation is achieved by a climber that ascends and descends the tether. In anticipation of industrial applicability near the ground, a climber for a rope-type tether (rope-type climber) was developed in this study. Compared with a climber for a belt-type tether, the rope-type climber has a small contact area between the tether and the roller, leading to problems with slippage and roller deterioration. Accordingly, here the contact area between the rope and roller was increased by using four drive wheels, and synchronized velocity control was accomplished with two drive motors for two drive wheels. Also the rope-type climber has more difficulty maintaining its orientation and is easily rotated around the tether by wind and other factors, so a control moment gyro (CMG) unit was developed that can be applied to the climber. An optimal servo system using a disturbance observer was applied to a rope-type climber with the developed CMG unit to achieve lift stabilization control. Then the effectiveness of the developed system was verified in lift experiments at the 25[m] outdoor test site of Kanagawa University and in a 1.2[km] lift experiment at the Space Elevator Challenge.

Attitude-correlated frames approach for a star sensor to improve attitude accuracy under highly dynamic conditions.

The attitude accuracy of a star sensor decreases rapidly when star images become motion-blurred under dynamic conditions. Existing techniques concentrate on a single frame of star images to solve this problem and improvements are obtained to a certain extent. An attitude-correlated frames (ACF) approach, which concentrates on the features of the attitude transforms of the adjacent star image frames, is proposed to improve upon the existing techniques. The attitude transforms between different star image frames are measured by the strap-down gyro unit precisely. With the ACF method, a much larger star image frame is obtained through the combination of adjacent frames. As a result, the degradation of attitude accuracy caused by motion-blurring are compensated for. The improvement of the attitude accuracy is approximately proportional to the square root of the number of correlated star image frames. Simulations and experimental results indicate that the ACF approach is effective in removing random noises and improving the attitude determination accuracy of the star sensor under highly dynamic conditions.

Elimination of Gyro Drift by Using Reversal Measurement

We aim to realize a large-scale straightness evaluation using a gyro. It detects tangential angles to evaluate a profile without any references. However, fluctuations of angular signal, called gyro drift, are considered a major contributor of error. We adopted a reversal measurement for eliminating the drift. The reversal measurement has been widely used for eliminating stable error from ancient. Here, we periodically performed reversal measurements for eliminating drift of a commercially available fiber optic gyro (FOG) unit. As a result, an angle could be derived with a standard deviation of 0.4 mrad for 1 hour of repeated measurements with an interval of 60 s, even though the gyro has a drift of several mrad/h including the effects of the Earth’s rotation. This indicates that the reversal measurement is effective in reducing the drift.

1P2-V10 宇宙エレベーター昇降実験機におけるCMGユニットの開発

The space elevator has been attracting as an alternative transportation between the earth and space. In the laboratory, we have been researching the climber technology to the realization of space elevator. In the space elevator, the attitude control of climbers is very important for ensuring the safety and feeling while riding of passengers. However attitude is influenced by surrounding environment because the climber is supported only by the tether. Generally, there is equipment that is called Control Moment Gyro (CMG) for attitude hold and vibration damping. In this paper, we introduced a control moment gyro unit for the attitude stabilization and we have examined attitude control of the climber using an optimal digital servo system including a disturbance observer.

Precision device for three-axes orientation measurement employing optical gyros

A scheme for a three-axes orientation measurement device that provides low sensitivity of orientation measurement errors to gyro errors is analyzed. The low-sensitivity property of the device is provided at the expense of continuous, one-directional rotation of the gyro unit. Gyro unit rotation enables measurement of spatial orientation when all gyros but one fail. This results from the fact that three components of the moving vehicle full-angle speed vector modulate three different parameters of the output signal of each gyro. The results obtained are significant for the development of small-sized strapdown inertial navigation systems that have high accuracy and reliability and employ low-cost optical gyros-laser, fiber optic, and integrated optic gyros.

A GYRO‐ORIENTED 3‐COMPONENT BOREHOLE MAGNETOMETER FOR MINERAL PROSPECTING, WITH EXAMPLES OF ITS APPLICATION1

ABSTRACTA triple axis borehole magnetometer is described that consists of a Förster‐probe (fluxgate) triplet (sensitivity 1 n T), a Förster‐probe gradiometer (sensitivity 2 nT/40 cm), a gyro unit (mean angular drift approx. 0.5°/h) which is equipped with accelerometers (sensitivity 1/100°), and a data transmission unit (with multiplexer and 16‐bit AD converter). The sensitive fluxgate‐magnetometer can detect weakly magnetic or small source bodies. Data from the gyro and the accelerometers allow the 3‐component magnetic field values to be transformed to north, east and vertical components. Since they do not rely on magnetically‐determined directional data, the results are not disturbed by local anomalies of the magnetic declination. Furthermore, the magnetometer can also be used in vertical boreholes. 3‐component measurements are carried out at discrete points in the neighbourhood of a source body to locate its position, and within the source body to determine the direction of magnetization. The strength of magnetization and information on magnetic classification are obtained by continuous measurement of one or more components within the source body. Calculation algorithms and computer programs are available to simplify data processing and interpretation. Survey examples are discussed.

An Integrated System for Land Navigation

Perhaps the most stringent requirement for land navigation is imposed by winter operations in the high arctic. The serious consequences of being lost or failing to find a supply dump in the arctic make reliability and accuracy vital necessities. A combination of circumstances conspire to also make the arctic a particularly difficult area in which to navigate by conventional means. Until GPS becomes fully operational, there will be no single system capable of continuously providing the necessary position and heading accuracy. Even then, reliability considerations will dictate that a self contained or autonomous backup be available, certainly for the military user. The Defence Research Establishment in Ottawa (DREO) has therefore developed a multi-sensor, optimally integrated navigation system to satisfy the present operational requirements of the Canadian land forces, which are most severe in the arctic. This system, called PLANS (Primary Land Arctic Navigation System) was designed to be a highly reliable, high- to moderately-accurate, automatic navigation system for all weather off-the-road use. Although designed primarily to meet an arctic requirement, PLANS would of course be just as applicable for desert navigation, or for any application in which reliability and accuracy are a priority, or where simpler and less costly methods are ineffective. PLANS combines several self contained sensors with two satellite receivers, using Kalman filter techniques to provide a continuous optimal estimate of position, height and heading. Time and attitude are also provided, along with waypointing functions. The self contained sensors consist of a gyrocompass/directional gyro unit, an odometer pickoff for speed, a magnetic fluxgate sensor (for which a detailed geomagnetic field model is used in the software) and a baroaltimeter. The satellite receivers are a single channel C/A-code GPS and a dual channel Transit. This paper describes the requirement, the difficulties in meeting this requirement, the design of a multi-sensor integrated system solution, some simulation results and some field trial results.

Development of methods for calibration and testing gyroscopic instruments for GW applications

As a preview to the main discussion, the role of the Twin Gyro Unit as a component part of the weapon's guidance system is first described. The reader will appreciate that there are as many types and configurations of gyro units as there are weapons and a full treatment of the subject would be beyond the scope of this paper. For the purposes of the discussion that follows, the gyro unit chosen is the two degree of freedom, electrically driven, Rotoraced displacement gyro, as used on the Sea Eagle, Anti Ship sea skimming missile.