Objective Prediction Tracking Control Technology Assisted by Inertial Information

In the weak-field and slow-motion approximation of the General Relativity theory the relativistic theory of construction of nonrotating harmonic coordinate reference systems is developed. The general case of an isolated astronomicalN-body system is considered. The bodies are assumed to consist of a perfect fluid and to possess any number of the internal mass and current multipole moments characterizing the internal structure and own gravitational field of the bodies. The description of the coordinate reference systems and gravitational field is realized by the specific forms of the metric tensor. A metric is determined by the method of the Post-Newtonian Approximations (PNA) from the inhomogeneous Einstein equations under the harmonic coordinate condition. We have obtained two different specific forms of a metric, which are related to the inertial and quasiinertial coordinate reference systems. The metric in inertial coordinates is a near-zone solution of the Einstein equations for anN-body system. The metric in quasi-inertial coordinates is a solution of Einstein equations in the body's neighborhood, which is a world tube surrounding the body under consideration and extending up to another nearest body. The coordinate transformation between the inertial and quasiinertial reference systems is derived by a matching of both solutions in the body's neighborhood. A new method is proposed for construction of the body's proper reference system. This coordinate system has an origin which moves along a nongeodesic (in the general case) worldline of the body's center of inertia. The proper reference system is used for derivation of the Newtonian equations of translational and rotational motion of the body. The equations give us exhaustive information about the nonlinear Newtonian interaction between gravitational fields of the bodies in terms of internal mass multipole moments. Finally, the coordinate transformation between the inertial and proper reference systems is discussed in the first PNA.

The recent developments in spatial data collection, management and software require the availability of proper geodetic infrastructures for integrating different types and sources of coordinates without causing effective changes in positions. Nowadays, positions are mostly collected by GNSS data collectors based on WGS84/ITRF reference systems. The data are then subjected to transformations and projections to a locally used system. Another possibility is direct data collection based on the local coordinate system by classical surveys using land surveying, photogrammetry, laser scanning, etc. The spatial data management is commonly operated using Geographic Information Systems (GIS) software for mapping, analysis, planning, and other services. The conversions between different coordinate systems should be well defined to guarantee the consistency of the coordinates on all systems and tools. In Palestine, the classical and local surveys are all based on the local coordinate system Pal1923Grid for engineering, cadastral and planning applications. The different GNSS RTK-service providers use different definitions and transformation methods between WGS84 or the International Terrestrial Reference Frames (ITRF) and the local Palestine1923Grid, whereas the Land authority has adopted a group of parameters to be implemented on the Global Navigation Satellite Systems (GNSS) data collectors, which do not fit with Palestine1923Grid properties. Additionally, different transformation methods are used in GIS applications for converting the coordinates between the different systems using WGS84 as an intermediate system. Here, the coordinates of a group of the geodetic network in the West Bank of Palestine are used to assess the accuracy of the different transformations and systems by comparing the transformed coordinates using the GNSS system and the originally registered coordinates. Furthermore, a grid of points covering the coordinate system extents is used to describe the differences between the transformations and systems. It was found that the parameters provided by GNSS service providers have results that are consistent with each other and the geodetic network in the West Bank of Palestine compared to GIS-software parameters. By contrast, all systems have extremely deteriorated coordinates in the Gaza strip and the further parts of the Pal1923Grid extents.

Based on the description of the commonly used coordinate systems for shipborne satellite antennas, this paper calculates the conversion matrices between the geographic coordinate system and the deck coordinate system, and the deck coordinate system and the antenna coordinate system, and establishes the AEC three-axis mount model. Based on the geometric derivation calculation of the polarization angle, the polarization angle deviation formula is derived using the antenna three-axis model, and the numerical simulation is performed using MATLAB to analyze the influence of the different angles of the C-axis deviation on the polarization angle under different elevation angles, and further verify the correctness of the theoretical analysis.

An idea of using computer mechanics for inertial navigation systems is given and examples are presented. The equations, algorithms, and properties of the pendulum-type strapdown inertial navigation system are analyzed. As a result, it has been stated that such a system is analogous to analytical systems. A similar comparison for both semi-analytical and strapdown inertial navigation systems, in which the Schuler’s pendulum models are described in a horizontal coordinate system, is carried out. An analogy of their properties is established. By comparing the analytical system, platform axes of which are directed along the axes of the inertial coordinate system (orientation of the Schuler’s pendulum is also described in the inertial coordinate system), and the strapdown inertial navigation system with the same orientation of the platform’s computer model (the comparison is also made for the operation algorithms of such systems), an analogy of such systems has been established. The degree of use of computer mechanics in all types of strapdown inertial navigation systems is much greater than in platform ones. According to the degree of utilization for principles of computer mechanics, types of inertial navigation systems can be arranged in the following order: strapdown pendulum, other strapdown systems, semi-analytical, analytical, and geometric platform inertial navigation systems. Their accuracy depends on the degree of sophistication of the element base, that is, on sensitive elements and on-board computers. We claim that the smaller the volume and mass of the mechanical part of the system the better its weight-and-dimensional characteristics and cost.

Visual and inertial navigation have obvious complementarity in navigation accuracy, and the combined navigation of the two has excellent anti-interference ability. In this paper, a visual-inertial-based satellite quality evaluation method is proposed. This method can judge whether the GPS (Global Positioning System) is interfered by comparing the visual-inertial navigation information with the GPS data information in the geographic coordinate system. This method enables the UAV to quickly switch the navigation mode under the condition of being disturbed, which ensures that the navigation function is accurate and free from interference, and provides a more solid foundation for the navigation of the UAV and other platforms.

This paper aims to study the fast finite-time (FFT) tracking control strategy for permanent magnet synchronous motor (PMSM). The design of FFT tracking controller for PMSM faces many difficulties due to the coupling between current and rotational speed, as well as the nonlinear characteristics of motor torque. To overcome the difficulty, we utilize a novel coordinate transformation to establish the mathematical models of PMSM in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha -\beta $ </tex-math></inline-formula> coordinate system and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d-q $ </tex-math></inline-formula> coordinate system. Based on the obtained PMSM model, novel FFT tracking control strategy including FFT direct axis current tracking controller and FFT position tracking controller is developed. Superior to the existing control schemes of PMSM, the new FFT tracking control strategy ensures that the states error of the system can be quickly stabilized in a limited time with faster convergence speed and stronger anti-interference. Finally, the effectiveness of the proposed control method is illustrated by simulation results.

The post-flight estimation of guidance instrument error is called guidance instrument error separation. It estimates the error coefficient of the airborne inertial navigation system by comparing the airborne inertial data received by the ground with the velocity and position data obtained by external measurement tools such as radar. Since the flight time is short and the error coefficient is not entirely appreciable, the traditional post-flight estimation usually adopts optimization methods such as least squares rather than filter-based methods to avoid convergence problems. The conventional separation method is based on the apparent inertial space navigation velocity or position matching, eliminating gravity’s effect. This treatment avoids the calculation of the partial derivative of the complex gravity model. Still, it makes the measurement error no longer independent, so it is not the best estimate of the error coefficient. With the continuous improvement of the accuracy of the strap-down inertial system, it is difficult for traditional methods to obtain valuable parameter estimation results. This paper proposes a new estimation method that employs a novel mixed calculation coordinate system called ”self-conjugate inertial space.” This coordinate system combines the advantages of the Earth-centered inertial coordinate system, the Earth-centered Earth-fixed coordinate system, and another coordinate system that turns in reverse around the Earth to simplify error analysis. The method considers the influence of external measurement data frequency, external measurement noise, telemetry noise, model linearization error, etc., and reduces the calculation error of the traditional error separation model. Numerical simulation and semi-physical experiments show that the proposed method can significantly improve airborne inertial navigation systems’ error coefficient estimation accuracy under typical conditions.

With a number of special Hamiltonians, solutions of the Schrödinger equation may be found by separation of variables in more than one coordinate system. The class of potentials involved includes a number of important examples, including the isotropic harmonic oscillator and the Coulomb potential. Multiply separable Hamiltonians exhibit a number of interesting features, including “accidental” degeneracies in their bound state spectra and often classical bound state orbits that always close. We examine another potential, for which the Schrödinger equation is separable in both cylindrical and parabolic coordinates: A z-independent V∝1/ρ2=1/(x2+y2) in three dimensions. All the persistent, bound classical orbits in this potential close, because all other orbits with negative energies fall to the center at ρ=0. When separated in parabolic coordinates, the Schrödinger equation splits into three individual equations, two of which are equivalent to the radial equation in a Coulomb potential—one equation with an attractive potential, the other with an equally strong repulsive potential.

A novel two-loop large offset tracking control of an uncertain nonlinear system with input constraints

We study the problem of tracking control and maneuver regulation control for a nonlinear nonminimum phase control system. First, a tracking controller, consisting of feedforward and static-state feedback, is designed to guarantee uniform asymptotic trajectory tracking. The feedforward is determined by solving a stable noncausal inversion problem. Constant feedback gains are determined based on linear quadratic regulator (LQR) optimization and assumed satisfaction of a robustness inequality. A maneuver regulation controller is obtained from the tracking controller by introducing a suitable state projection that is related to the LQR feedback gains. Properties of the closed loop, including local asymptotic convergence of the transverse errors are described. A multivariable flight control problem is used to demonstrate the approach.

Combined rigorous-generic direct orthorectification procedure for IRS-p6 sensors

With the explosive usage of smart mobile devices, sustainable access to wireless networks (e.g., Wi-Fi) has become a pervasive demand. Most mobile users expect seamless network connection with low cost. Indeed, this can be achieved by using an accurate received signal strength (RSS) map of wireless access points. While existing methods are either costly or unscalable, the recently emerged mobile crowdsensing (MCS) paradigm is a promising technique for building RSS maps. MCS applications leverage pervasive mobile devices to collaboratively collect data. However, the heterogeneity of devices and the mobility of users could cause inherent noises and blank spots in collected data set. In this paper, we study how to: 1) tame the sensing noises from heterogenous mobile devices and 2) construct accurate and complete RSS maps with random mobility of crowdsensing participants. First, we build a mobile crowdsensing system called $i$ Map to collect RSS measurements with heterogeneous mobile devices. Second, through observing experimental results, we build statistical models of sensing noises and derive different parameters for each kind of mobile device. Third, we present the signal transmission model with measurement error model, and we propose a novel signal recovery scheme to construct accurate and complete RSS maps. The evaluation results show that the proposed method can achieve 90% and 95% recovery rate in geographic coordinate system and polar coordinate system, respectively.

This paper presents a wearable anemometer for detecting wind absolute orientation and wind speed, as well as attitude and heading angles by incorporating a micro homemade thermal flow vector sensor with commercial triaxial micro accelerometer and triaxial micro magnetometer. The thermal flow vector sensor is comprised of three roundabout Pt hot-films uniformly distributed in a circle that is fabricated on a polyimide substrate. The flow sensor detects flow speed and flow relative angle in the body coordinate system, which is calculated from the heating powers of three hot-films that are operated in constant temperature difference circuits. The flow relative angle is further converted to the wind absolute orientation in the geographic coordinate system by means of the attitude and heading angle detected by using the triaxial accelerometer and triaxial magnetometer. The power consumption of the whole anemometer is about 400~500 mW under a wind blowing of 0 20 m/s. Using a rechargeable lithium battery with a capacity of 600 mAh, the anemometer can be continuously worked for about 4 h. Wind experimental results demonstrate that the root mean square (rms) error of the wind speed measurement reaches 0.17 m/s in the range of 0~18.9 m/s, the rms errors of wind relative angle and absolute orientation reach 2.79° and 3.22°, respectively, in the range of 0~360°. Attitude and heading experimental results illustrate that the rms errors of heading and roll measurements reach 0.42° and 0.15°, respectively, in the range of -180°~180°, and the rms error of pitch reaches 0.13° in the range of -90°~90°.

Integration of robotic total station and digital image correlation to assess the three-dimensional surface kinematics of a landslide

In this paper, we present PTZ-Calib, a robust two-stage PTZ camera calibration method, that efficiently and accurately estimates camera parameters for arbitrary viewpoints. Our method includes an offline and an online stage. In the offline stage, we first uniformly select a set of reference images that sufficiently overlap to encompass a complete 360° view. We then utilize the novel PTZ-IBA (PTZ Incremental Bundle Adjustment) algorithm to automatically calibrate the cameras within a local coordinate system. Additionally, for practical application, we can further optimize camera parameters and align them with the geographic coordinate system using extra global reference 3D information. In the online stage, we formulate the calibration of any new viewpoints as a relocalization problem. Our approach balances the accuracy and computational efficiency to meet real-world demands. Extensive evaluations demonstrate our robustness and superior performance over state-of-the-art methods on various real and synthetic datasets. Datasets and source code can be accessed online at https://github.com/gjgjh/PTZ-Calib