基于相机状态方程多模增广的改进MSCKF算法

针对基于多状态约束卡尔曼滤波(MSCKF)的视觉-惯性里程计算法中相机状态方程增广过程的误差累积问题,提出了一种相机状态方程多模增广方法。该方法首先对视觉特征跟踪状态的稳定性进行判断,然后自动地选择基于视觉图像信息优化求解相机相对位姿参数或基于惯性传感器(IMU)状态递推结果联合相机外参初始化新图像帧相机位姿参数两种途径增广相机的状态方程,解决特征跟踪状态稳定情况下IMU误差的累积问题。实验部分通过EuRo C数据和实际应用数据对算法的性能进行了验证分析,结果表明,改进后的MSCKF算法能够在特征跟踪稳定状态下有效避免IMU误差的累积,进一步融合视觉与惯性系统之间的互补优势,提高载体的定位定向精度和稳定性。     

背架式隔振系统特性的状态空间分析方法

使用状态空间法,将背架式隔振系统的微分方程组转化为状态空间方程,使用MATLAB/Simulink模块可方便求解背架式隔振系统的固有频率和隔振系数,为背架式隔振器系统设计、选用提供理论依据.     

Automating studies of the technical state of dangerous mechanical systems

Automation of the process of studying the dynamics of the technical state of dangerous machines and constructions by combined application of object-oriented modeling of data and knowledge, model- and precedent-based reasoning, and mathematical modeling is suggested. Automation ensures the efficient performance of preproject studies and also the timely interpretation of parameters of the technical state and identification of failure and damage precursors at the stage of operation, aimed at ensuring reliability and technogenic safety.     

Determining the equation of state of amorphous solids at high pressure using optical microscopy

A method to determine the volumetric equation of state of amorphous solids using optical microscopy in a diamond anvil cell is described. The method relies on two- dimensional image acquisition and analysis to quantify changes in the projected image area with compression. The area analysis methods prove to be robust against improper focusing and lighting conditions while providing the accuracy necessary to deduce small area changes, which correspond to small volume changes in an isotropic material. The image capture, area analysis method is used to determine the compression of cubic crystals, yielding results in good agreement with diffraction and volumetric measurements. As a proof of concept, the equation of state of amorphous red phosphorus is measured up to 12 GPa under hydrostatic conditions where the quantified volume change between the red and black phases is approximately ΔV/V(0) ≈ 0.05 after a reduction of volume nearing 35% at 8 GPa. A large hysteresis is present during decompression and eventually results in a 15% permanent densification relative to the starting volume, which is attributed to a pressure induced crystallization from red to black phosphorus. The robustness of the technique is also demonstrated by measuring the equation of state of GeSe(2) glasses for semi transparent samples and As(2)O(3) in which gold coating is used as a contrasting aid.     

Passive identification of heat equation coefficients with account for errors in estimating the state of the object and measuring system

This paper describes the problem of passive identification of heat equation coefficients with account for the noise of the behavior of the object dynamics model and for the noise of the measuring system model. The use of the finite difference method allowed for reducing the solution of partial differential equations to the solution of a system of linear finite-difference and algebraic equations described by models in the form of a state space. Presentation of the heat equation in form of such a model makes it possible to apply the Kalman filter algorithm for the reliable estimation of the behavior of the object under study.     

State-dependent differential Riccati equation to track control of time-varying systems with state and control nonlinearities

This work studies an optimal control problem using the state-dependent Riccati equation (SDRE) in differential form to track for time-varying systems with state and control nonlinearities. The trajectory tracking structure provides two nonlinear differential equations: the state-dependent differential Riccati equation (SDDRE) and the feed-forward differential equation. The independence of the governing equations and stability of the controller are proven along the trajectory using the Lyapunov approach. Backward integration (BI) is capable of solving the equations as a numerical solution; however, the forward solution methods require the closed-form solution to fulfill the task. A closed-form solution is introduced for SDDRE, but the feed-forward differential equation has not yet been obtained. Different ways of solving the problem are expressed and analyzed. These include BI, closed-form solution with corrective assumption, approximate solution, and forward integration. Application of the tracking problem is investigated to control robotic manipulators possessing rigid or flexible joints. The intention is to release a general program for automatic implementation of an SDDRE controller for any manipulator that obeys the Denavit–Hartenberg (D–H) principle when only D–H parameters are received as input data.     

Differential equation for continuous normalization

When the response of a dynamical system is seemingly random and is confined in a finite region and shows extreme sensitivity to small changes in initial conditions, we say that the motion is chaotic. To represent chaos of a system precisely and quantitatively, we employ measurement quantity that represents the system's degree of chaos such as a Lyapunov exponent. A way of computing a Lyapunov exponent employs periodic renormalization for the state perturbation vector. However, the application of periodic renormalization for a Lyapunov exponent computation poses difficulties. One difficulty is exponential growth of the norm of the state perturbation vector. A common approach for avoiding this computational problem is periodic renormalization. However, periodic renormalization raises a discontinuity in the state perturbation vector that is not a standard case in optimal control theory as one wants to extremize chaos by manipulating a Lyapunov exponent. To circumvent the exponential growth in magnitude and the state perturbation vector discontinuity problem, one may employ a method of “continuous normalization” which replaces periodic discontinuous renormalization with differential equations that correspond to continuous normalization at each instant of time. This study provides details concerning the development of continuous normalization technique and presents an example for some systems. Also the comparison between the result produced by continuous normalization and that by the periodic renormalization of the state perturbation vector will be given.     

The equation for the friction of metals

Experimental evidence is given for the equation μ = (σ/p) cot ψ, where σ/p involves the material properties and cot ψ the surface properties of the sliding surfaces, and the equation is further discussed.     

Generalized Reynolds equation for porous boundaries

A generalized form of Reynolds equation has been obtained which permits the variation of relevant quantities across as well as along the lubricant film with porous boundaries. The equation has been derived with a minimum of restrictive assumptions and in particular cases it reduces to the various forms which other workers have developed. It is suggested that the equation derived is applicable to the various models for synovial joints and porous bearings.     

A new method for comparative light and electron microscopic studies of individual cells,selected in the living state

A method is described which permits comparative light and electronmicroscopic studies of cell cultures, cell spreads or single selected cells which have been kept in the Plastic Film Dish (PFD). The PFD is a versatile large surface tissue culture chamber which, for electron microscopy, is mounted with a transparent FEP-Teflon film bottom. Cells are observed, selected and marked on the PFD-bottom with a high power inverted light microscope. The cells are fixed and dehydrated with a semi-automatic device while they are still in situ in the PFD. During the preparation steps for electron microscopy the topographical relationship between individual cells and between cells and cell support is accurately retained. After embedding and polymerization the Teflon film is easily peeled off the polymerized Epon, leaving a replica of the mark around the selected cell. This permits relocation of the selected cells for ultrathin sectioning in a plane plan-parallel to the original cell support. To enable orientated sectioning of selected cells in a plane perpendicular to the cell support, cells are tagged with Letraset-letters after original embedding and polymerization. Subsequently the re-embedded polymerized specimens are orientated in the microtome in a position which permits controlled thin sectioning of the tagged cells in the previously selected plane.     

Bosi's method for solving Laplace's equation

Conformal mapping is used to obtain an implicit solution for a slightly specialized version of a planar electrostatic mirror for which Bosi claims to have obtained an exact solution by means of a Taylor series in the ratio of two dimensions. It is shown that the intervention of logarithmic terms invalidates Bosi's series after the first-order term. Comparison of Bosi's series for cylindrical and spherical mirrors with the exact expansion for an analogous planar problem suggests that in these cases not even the first-order terms are valid.     

A streak-photography method for measuring the shock-wave velocity in experiments on studying the equation of state of matter on the Iskra-5 laser facility

A technique for measuring the velocity of a shock wave arising in laser-irradiated samples in experiments involved in studies of the shock compressibility of substances is described. This method ensures a spatial resolution of 10 μm, an error in measuring the shock-wave delay in layers of 10 ps, an error in measuring the shock-wave velocity of 2.5%, and a dynamic range of recording of ∼200. The measurement results are presented. Original Russian Text ? S.A. Bel’kov, A.G. Kravchenko, A.V. Kunin, D.N. Litvin, V.M. Murugov, A.V. Senik, 2006, published in Pribory i Tekhnika Eksperimenta, 2006, No. 2, pp. 150–153.     

汽车制动器摩擦材料的研究现状和发展

介绍汽车制动器摩擦材料的研究现状。探讨半金属基摩擦材料、非石棉有机摩擦材料和粉末冶金摩擦材料的优缺点。提出汽车制动摩擦材料研究的发展趋势。     

Determination of Johnson-Cook constitutive equation for Inconel 601

Due to their superior thermal and mechanical properties, super alloys widely used in the aerospace industry have been well-documented in terms of AdvantEdge-based analysis of cutting characteristics rather than experimental methods. However, the well-known super alloy Inconel 601 does not have any database of its material properties in AdvantEdge, which underscores the urgency to build such a database. Hence, the current study uses the Johnson-Cook equation to build a database of Inconel 601’s material properties in AdvantEdge. To that end, drawing on a room temperature tensile test, elevated temperature tensile test and orthogonal cutting test, the current study determines the Johnson-Cook constitutive equation for Inconel 601, and verifies the reliability of the determined Johnson-Cook constitutive equation by comparing the experimental values with the analytical values.     

Derivation of an equation for quantitative SIL assignment

Quantitative risk analysis for selection of safety integrity levels (SIL's) is becoming more prevalent due to the high equipment costs associated with qualitative methods. Procedures for applying quantitative methods to the SIL selection problem are in the early stages of development. Literature explaining quantitative methods is scarce and many engineers are forced to develop ad hoc procedures, some of which are mathematically flawed. One of the equations popularly used to assign a probability of failure on demand (PFD) to a safety instrumented function (SIF) based on tolerable risk and unmitigated event frequency is shown in the equation below. Variations of this equation are in use by various SIS practitioners: PFD(SIF) = f(Tolerable)_Risk/f(Unmitigated)_Event. This paper presents a rigorous derivation of this equation based on scientific laws of probability math and standardized definitions used in the field of SIS engineering. By publishing this derivation the author hopes to lend more credibility to this type of SIL selection process and increase its usage in the process industries.     

Equation of state for carbon dioxide

An equation of state (EOS) for carbon dioxide has been presented by Span and Wagner (1996). This equation of state is accurate but contains many terms. Some of the terms are complex exponential which become difficult for computation. Therefore a new simple equation of state with 30 terms is proposed. Bank of terms are suggested and an optimum set of terms is selected by a random search method. This new equation of state with less terms and simple exponential is simpler to use. The two equations of state are compared with the available experimental data. The results show that the new EOS is less accurate than Span and Wagner in gas and liquid regions but more accurate in the critical region.     

The three-dimensional Reynolds equation for micro-polar-fluid-lubricated bearings

The three-dimensional Reynolds equation for micropolar fluids is derived. The balance equations for micropolar fluids are simplified by using traditional lubrication assumptions and order-of-magnitude analysis. The simplified equations are solved to yield expressions for the velocity distribution and the microrotation velocities.A generalized Reynolds equation is subsequently derived in the conventional manner.     

Use of polar finite-difference approximation for solving bi-harmonic equation for plates

The bi-harmonic equation in polar coordinates is solved by using finite-difference approximations. It is found that the advantage of using a polar finite-difference grid on a plate sector with circular boundaries is that the mesh size and the location of the grid points can be chosen so that it can be superimposed on the circular boundaries. This minimizes the amount of computational work to properly apply the boundary conditions.Numerical examples of fully circular plates and plate sectors with various boundary conditions are solved. The finite-difference solutions are compared with the analytical solutions. The method is presented in general form so that it can be applied to plate sectors with any type of loading and a variety of boundary conditions. The method is found useful for several problems of this nature for which no close-form solution is available.     

Analysis of bioheat transfer equation for hyperthermia cancer treatment

Magnetic fluid hyperthermia is a new subclass of hyperthermia cancer treatment that can selectively heat up a tumor without damaging the surrounding healthy tissues. Some authors studied the temperature distribution of a magnetically mediated tumor assuming a homogeneous distribution of nanoparticles inside the tumor. Practically speaking, the injected nanoparticles do not usually distribute uniformly throughout the entire tumor, thus leaving some parts of the tumor without nanoparticles. In this study, an inhomogeneous dispersion of nanoparticles inside the tumor is assumed to investigate the tissues’ temperature profiles. The problem is solved for polar coordinate. Also in this study, the heating effect of magnetic fluid in a porcine liver tissue is experimentally examined. Numerical transient solutions are found to be in good agreement with experimental data.