并行程序性能检测及可视化

信息检测是信息处理的核心,随着并行计箅应用领域的不断拓展,实际应用中对并行程序性能分析的需求越来越迫切,其中并行程序性能数据的检测足性能分析的核心,获取的数据准确与否直接影响到性能分析的结果.本文提出了一种基于事件追踪方式的MPI并行程序性能软检测及可视化方法.并给出了一个原型系统PVADE,在获取的较完备、较精确的性能数据的基础上,对并行程序的执行过程可视化重演,帮助发现程序的瓶颈点,为并行程序的优化提供参考.     

Numerical solution of two-dimensional or axi-symmetric incompressible flow using the vorticity equations

A method to integrate the vorticity-velocity form of two-dimensional or axi-symmetric incompressible Navier-Stokes equations is described. The method employs equi-potential lines and streamlines of an inviscid flow as coordinate lines and the velocity field is determined from the vorticity distribution with boundary conditions on the normal velocity only, while the tangential velocities are used as boundary conditions for the vorticity. The results of numerical experiments on time-dependent flow past an impulsively started circular cylinder and sphere are, then, presented to demonstrate the performance of the scheme. Numerical results show that the present method is very stable and accurate.     

几种数值算法在弹道微分方程组解算中的仿真与比较

本文简述了数值分析的应用范围,介绍了微分方程几种不同的数值解法,及其在弹道解算中的应用。在简化弹丸弹道动力学微分方程的基础上,通过 Mablab 软件编写欧拉法、梯形法、经典四阶龙格库塔法程序,计算动力学微分方程组近似解及各种方法的局部截断误差和计算时间。通过对结果的分析比较,明确了几种经典解法在弹道解算中的优劣,为弹道解算方法的选择提供了依据。     

Energy dissipation rate control and parallel equations solving method for planar spined quadruped bouncing robot

This paper continues our investigation into Energy dissipation rate control (EDRC) and Parallel equations solving method (PESM). Our previous works showed how EDRC enables us to provide stable walking or running gaits for legged robots via controlling robot’s loss of energy rate during Impact phases (IP). This is while PESM facilitates the trajectory designing process of the robot’s active joints during each Single support phase (SSP) by solving the robot’s inverse kinematic and inverse dynamic equations in parallel. Even though PESM is very powerful and suitable for both quadruped robot, and despite the under actuation problem at the ankle joint, and biped robots, despite the presence of Zero momentum point criteria (ZMP) at the ankle joint, still, this method is limited to robots just with three and five DoFs. Therefore, the main purpose hereis to show how it is possible to extend the application of PESL to a spined quadruped robot with four DoFs by employment of the Central pattern generator (CPG) controller units and finding a connection among CPG’s output, PESM and the robot’s foot placement. Besides, as EDRC is employed to realize a stable bouncing gait for the robot, a whole numerical study is performed on the robot’s impact dynamic equations to evaluate the effect of spine joint on the robot’s impact dynamics.

     

Semi-conjugate residual method for iterative solving the Navier-Stokes problem

The semi-conjugate residual algorithm is applied to solving a three-dimensional Navier-Stokes problem on nested grids. A three-level iterative algorithm for solving the problem is described. Results of numerical experiments on a sequence of grids and different Reynolds numbers are presented for a test problem. The results prove efficiency of the proposed approach.     

Infinitesimal displacement analysis of a parallel manipulator with circular guide via the differentiation of constraint equations

This paper considers several subproblems associated with solving the forward and inverse position and speed problems and defining singular configurations for a parallel robot with six degrees of freedom and six kinematic chains that move along a circular guide (rotopod). The solution of these subproblems is necessary for analyzing the topological features of the parallel robot and employing the results of such analysis in control algorithms design.     

Homogenization of the unstationary incompressible Reynolds equation

This paper is devoted to the effects of surface roughness during hydrodynamic lubrication. In the numerical analysis a very fine mesh is needed to resolve the surface roughness, suggesting some type of averaging. A rigorous way to do this is to use the general theory of homogenization. In most works about the influence of surface roughness, it is assumed that only the stationary surface is rough. This means that the governing Reynolds type equation does not involve time. However, recently, homogenization was successfully applied to analyze a situation where both surfaces are rough and the lubricant is assumed to have constant bulk modulus. In this paper we will consider a case where both surfaces are assumed to be rough, but the lubricant is incompressible. It is also clearly demonstrated, in this case that homogenization is an efficient approach. Moreover, several numerical results are presented and compared with those corresponding to where a constant bulk modulus is assumed to govern the lubricant compressibility. In particular, the result shows a significant difference in the asymptotic behavior between the incompressible case and that with constant bulk modulus.     

不同驱动形式开炼机传动系统性能对比

开炼机是橡胶厂常用设备,主要用于胶料热炼、压片、塑炼及混炼等。其传动系统在整机质量中占很大比例。由于工作时尖峰负荷较高,条件恶劣,且环境较差,因此传动系统的减速机使用寿命较短。本工作对不同传动方式的开炼机传动系统性能进行对比,以期为开炼机传动系统的优化设计提供参考。     

Performance comparison of microchannel evaporators with refrigerant R-22

An experimental study on the performance comparison of microchannel evaporators with refrigerant R-22 was conducted. Six microchannel evaporators were designed and manufactured for a residential air-conditioner. They were tested with psychrometric calorimeter test facilities. The experiment was performed with both vapor compression system and refrigerant circulation system. Each evaporator was made up of two parallel flow heat exchangers connected with several return pipes. The parallel flow heat exchanger had 41 microchannel tubes inserted between inlet and outlet headers. The microchannel tube had 8 rectangular ports with the hydraulic diameter of 1.3 mm. For the vapor compression system, the flow area ratio and the number of return pipes had a great effect on the cooling capacity. Type 3 with a flow area ratio of 73% and 58% showed the best cooling capacity. It had 12 return pipes and 3 circuits. There is a merging manifold in it. The effect of the number of circuits and merging manifold on the cooling capacity was relatively small. For the refrigerant circulation system, the effect of the mass flow rate on the cooling capacity was slightly superior to that of inlet quality. The effect of the number of circuits on the cooling capacity was different from the result of the vapor compression system. The effect of merging manifold was negligible, which was consistent with the result of the vapor compression system. The cooling capacity proportionally increased as the vertical inclination angle of the evaporator increased due to gravity force.     

Projection of the rotation form Navier-Stokes equation onto the half-staggered grid

A projection method for computing incompressible fluid flow is proposed. For the method, the rotation form Navier-Stokes equation (NSE), for which the velocity and the total pressure are employed, is discretized on the half-staggered, finite difference spatial grid. The total pressure couples the static pressure gradient and the convection of momentum in the continuous NSE while the half-staggered grid provides weak pressure-velocity coupling in discrete space. These two features interact synergistically for the discretized NSE to produce smooth pressure fields without additional numerical artifacts such as the momentum interpolation. The method preserves the kinetic energy at the inviscid limit condition. Numerical solutions of the decaying Taylor vortex, the inviscid Taylor vortex, the sudden expansion channel and the square-prism wake are presented.

     

两类多油楔浮环轴承性能比较

高速轻载机械常使用多油楔轴承,通过对三油楔浮环轴承和油楔个数是其两倍的六油楔浮环轴承动压油膜流体动力特性的计算和比较,判断出多油楔浮环轴承油楔个数及浮环对轴承性能的影响.多油楔浮环轴承不但边界复杂而且是多域问题,由于边界元方法不需要域内网格划分,只需边界离散,因而在处理复杂边界问题、多域问题时有其独特的优越性,计算工作量小,精度高.利用边界元方法计算了三油楔、六油楔两类浮环轴承的外油膜流场分布、轴承及浮环表面压力分布、e =0.03时轴承表面压力分布直观图、有无浮环时内摩擦损耗,并且对两类轴承的稳定性、承载能力及内摩擦损耗作了比较.通过对计算结果的分析和比较判断出在相同的偏心率下油楔个数的增加可以提高轴承的稳定性和承载力,加入浮环后可以减小轴承的内摩擦损耗.     

九相感应电机与三相感应电机的性能比较

与三相电机相比,多相电机具有高可靠性,转矩脉动小,多可控自由度等优点.针对多相电机是否具有这些优势的问题,建立了多相电机的数学模型,从磁动势角度出发,深入分析比较了多相电机与三相电机的性能,并以一台九相电机为研究对象进行了有限元仿真.研究结果表明,多相电机具有较高的可靠性,并能进行非正弦供电,输出转矩提高,转矩脉动减小...     

失速型和变距型风力机的性能比较

扼要介绍了并网风力机的模型，并分别对失速型风力机和变距型风力机的偏载性能进行计算和比较。结果表明，变距型风力机风能利用系数高，在高风速时所受的载荷小。     

Constraint operator for the kinematic calibration of a parallel mechanism

This paper introduces a constraint operator for the kinematic calibration of a parallel mechanism. By adopting the concept of a constraint operator, the movement between two poses is constrained. When the constrained movements are satisfied, the active joint displacements are taken and inputted into the kinematic model to compute the theoretical movements. A cost function is derived by the errors between the theoretical movement and the actual movement. The parameters that minimize the cost function are estimated and substituted into the kinematic model for a kinematic calibration. A single constraint plane is employed as a mechanical fixture to constrain the movement, and three digital indicators are used as the sensing devices to determine whether the constrained movement is satisfied. This calibration system represents an effective, low cost and feasible technique for a parallel mechanism. A calibration algorithm is developed with a constraint operator and implemented on a parallel manipulator constructed for a machining center tool.     

Nonlinear problem of the mechanics of an incompressible continuous medium

An iterative algorithm for solving the problem of deformation of incompressible plastic bodies has been built. The incremental flow theory and the relationship of general form connecting stress intensities with deformation rate intensities have been used.     

Formulating Jacobian matrices for the dexterity analysis of parallel manipulators

The condition number of the Jacobian matrix has been commonly used in determining the dexterous regions of a manipulator workspace. This has been successful when applied to manipulators having either solely spherical or solely Cartesian degrees of freedom. However, for manipulators having a mix of both rotational and translational degrees of freedom, i.e., complex degree of freedom manipulators, the condition number of the Jacobian matrix may not be used due to dimensional inconsistencies with its elements. This paper furthers earlier work introduced in obtaining a Jacobian matrix which may be used to determine the dexterity of parallel mechanisms regardless of the number and type of degrees of freedom of the mechanism. The result of the method introduced in this paper is a dimensionally homogeneous Jacobian matrix mapping m actuator velocities to n independent end effector velocities. In the typical case where m = n, the Jacobian matrix is also square. As opposed to earlier works, the singular values of the Jacobian matrix obtained here have an evident physical significance. Furthermore, the ratio of the maximum and minimum singular values, i.e., the condition number may be used to measure the dexterity of the manipulator at a given pose. To illustrate the concepts introduced in this paper, the 3-PRS manipulator is analyzed.     

并联机床开放式数控系统

介绍了并联机床开放式数控系统的软件、硬件设计。     

Diffractive focusing fan-out element for the parallel DNA sequencer

Various issues of creation of diffractive optical elements transforming one laser beam with small divergence to a matrix of converging beams with a diffraction size of focused spots in the plane of object illumination and their application for problems of DNA sequencing and microscopy are considered. The parameters of diffractive elements are calculated and optimized in the approximation of the Fresnel–Kirchhoff diffraction theory. Diffractive elements are fabricated by the method of direct laser writing on a photoresist by using a circular laser writing system. Experimental characteristics of a diffractive element creating a matrix consisting of 33 × 33 beams, which are focused in one plane at a distance of 210 mm, are presented. The degree of nonuniformity of beam intensities determined by the ratio of beam intensities in the central region to intensities of peripheral beams is 1/2.5, which is potentially sufficient to be used in DNA sequencing problems. The maximum distortions of spot positions in the entire focusing field is <0.15%.     

并联机械手实验装置研制

研制了一种并联机械手装置,并对两台并联机械手对击小球的过程进行了研究。分析了该机械手的运动学问题,推导出其位置方程、速度方程。对机械手的运动和小球的运动建立了数学模型,并对机械手的位置、速度、角速度和运动轨迹进行仿真和试验。试验表明,该装置性能稳定、运动过程安全可靠,满足相关科研和教学使用要求。