Geometry-based efficient rata coordination for manipulators with kinematic redundancy

The redundancy resolution problem for kinematically redundant serial chain manipulators is addressed. In this article we present a generalization of the geometry-based rate allocation algorithm, developed initially for only a minimum norm solution, to obtain the optimal joint rate solution for any specified objective function, with or without weightage. This generalization is made possible through a physial interpretation of the common pseudoinverse-based gradient solution scheme, and by developing a modified formulation for the objective function as a minimum criterion not with respect to the origin of the joint rate space, but with respect to another point in the joint rate space represented by the gradient of the specified objective. Application examples of the algorithm including procedures of solution are demonstrated using 7R manipulators with two generic types of geometry. Moreover, a closed form optimal solution for the class of 7R anthropomorphic arms is also given. © 1995 John Wiley & Sons, Inc.     

Driving simulator parameterization using double-lane change steering metrics as recorded on five modern cars

Steering sensitivity and steering torque gradient are two important metrics describing on-center vehicle dynamics response and steering feedback. The objective of this work is to acquire the steering metrics of real cars during double-lane change tests and indicate the key parameters of the vehicle that determine these steering metrics. Harnessing the reported findings, driving simulator users can swiftly adjust key parameters to achieve a realistic on-center response. We instrumented and tested five modern passenger cars, and used a vehicle dynamics model to extract the metrics for multiple vehicular parameterizations (steering ratio, power assist gain, etc.) and test speeds. Sensitivity analysis showed that steering sensitivity was mainly influenced by the components that determine the steering ratio whereas the steering torque gradient was also affected by power assist steering settings. An example study indicated how vehicular parameterization could be adapted to achieve realistic on-center vehicle steering response and steering feedback in a driving simulator.     

Solution of nonlinear fractional differential equations using an efficient approach

We present an efficient approach for solving nonlinear fractional differential equations. The convergence analysis of the approach is studied. To demonstrate the working of the presented approach, we consider three special cases of nonlinear fractional differential equations. The results of theses examples and comparison with different methods provide confirmation for the validity of the proposed approach.     

Optimum design of long-span suspension bridges considering aeroelastic and kinematic constraints

Cable supported bridges are wind prone structures. Therefore, their aerodynamic behaviour must be studied in depth in order to guarantee their safe performance. In the last decades important achievements have been reached in the study of bridges under wind-induced actions. On the other hand, non-conventional design techniques such as sensitivity analysis or optimum design have not been applied although they have proved their feasibility in the automobile or aeronautic industries. The aim of this research work is to demonstrate how non-conventional design techniques can help designers when dealing with long span bridges considering their aeroelastic behaviour. In that respect, the comprehensive analytical optimum design problem formulation is presented. In the application example the optimum design of the challenging Messina Strait Bridge is carried out. The chosen initial design has been the year 2002 design proposal. Up to a 33% deck material saving has been obtained after finishing the optimization process.     

An efficient architecture for a transputer based vehicle simulator

This paper presents an efficient architecture for the rendering and display sections of a vehicle simulator prototype. The architecture for the rendering stage, which consists of three independent concurrent units, has been optimised to support the two-layer dynamic load balancing technique. The display stage has also been partitioned to facilitate parallel updating of the pixel data to the dual frame buffers. The design of the frame buffers and the interface logic to access them by direct memory access (DMA) controllers (via three common address and data buses) and the colour video controller are also presented. Simulation results show that the adoption of DMA based memory transfer between the local memory of the transputer nodes and the frame buffers can alleviate the communication bottleneck prevalent in an earlier prototype.     

MASE-BDI: agent-based simulator for environmental land change with efficient and parallel auto-tuning

This paper presents an agent-based simulator for environmental land change that includes efficient and parallel auto-tuning. This simulator extends the Multi-Agent System for Environmental simulation (MASE) by introducing rationality to agents using a mentalistic approach—the Belief-Desire-Intention (BDI) model—and is thus named MASE-BDI. Because the manual tuning of simulation parameters is an error-prone, labour and computing intensive task, an auto-tuning approach with efficient multi-objective optimization algorithms is also introduced. Further, parallelization techniques are employed to speed up the auto-tuning process by deploying it in parallel systems. The MASE-BDI is compared to the MASE using the Brazilian Cerrado biome case. The MASE-BDI reduces the simulation execution times by at least 82 × and slightly improves the simulation quality. The auto-tuning algorithms, by evaluating less than 0.00115 % of a search space with 6 million parameter combinations, are able to quickly tune the simulation model, regardless of the objective used. Moreover, the experimental results show that executing the tuning in parallel leads to speedups of approximately 11 × compared to sequential execution in a hardware setting with 16-CPU cores.     

A parallel simulator for multibody systems based on group equations

The Journal of Supercomputing - Multibody systems consist of a set of components connected through some joints, where the movement of the system is determined by those of its components. Their...     

Expansion of the cross-efficiency evaluation by using the equations forming the efficient frontier in DEA

In this paper, we propose an algorithm to calculate cross-efficiency scores which used the equations forming the efficient frontier in data envelopment analysis (DEA). In many standard DEA models, each decision-making unit (DMU) is evaluated by using the advantageous weight for itself. Then, many DMUs are evaluated as efficient, and those efficient DMUs are not ranked by the models. The cross-efficiency evaluation is a method to rank DMUs by using the advantageous weights for all DMUs. Previously, the cross-efficiency scores based on different ideas are calculated by solving multiple linear or nonlinear programming problems. However, it is often hard to solve such a nonlinear programming problem. Therefore, by analysing the efficient frontier, we construct an algorithm to calculate alternative cross-efficiency scores.     

Asymptotic behaviour of infinite chains of coupled kinematic points: second-order equations

The behaviour of infinite chains of coupled kinematic points is studied. The points are second order, that is, they have mass. The chains could have been designed in any number of ways, including linear-quadratic optimal control. Behaviour means what happens as time goes to infinity. It is not assumed that the initial state is in the Hilbert space \(l^{2}\) because it has been seen in our previous work that in some situations this assumption has anomalous results. Instead, the initial state taken to be \(l^{\infty }\) . The finite-dimensional version of the infinite second-order system we study arises in physics in the theory of phonons.     

Teaching microcomputer-based design using a lift simulator

The most difficult part of any course on microcomputer-based design is teaching how to recognize what parts of a problem solution should be implemented in hardware and what parts should be implemented in software. An outline is given of how a simple lift simulator can be used to illustrate the differences between different implementations and how students can be taught to evaluate these differences.     

Application of a new efficient attitude determination algorithm on a ground simulator

In general, precise attitude information is required to control a ground simulator, which is designed to simulate attitude control of spacecraft. Two algorithms are well-known to determine the attitude through two or more observation vectors. One is the deterministic method, such as the TRI-axis Attitude Determination (TRIAD) algorithm, and the other is the optimal method, such as the QUaternion ESTimator (QUEST) algorithm. This paper suggests a new efficient attitude determination algorithm, which the authors name an algorithm “Averaging TRIAD.” First, it is transformed from the attitude matrix to the attitude angle vectors to maintain orthogonal constraints during calculation. Second, the covariance matrix is used instead of the variance and then it is applied to an unbiased minimum variance formula for more accurate solutions. Finally, the authors suggest a methodology to determine the attitude when more than three measurements are given. The performance of the Averaging TRIAD algorithm upon the combination of different sensors, which are fixed to the ground simulator, is investigated by numerical simulation in terms of standard deviations and computational time.     

A formulation of kinematic constraints imposed by kinematic pairs using relative pose in vector form

This paper presents a formulation that expresses kinematic pairs in form of holonomic constraints as functions of a measure of the relative position and orientation of the connected bodies expressed in vector form. While formulating the relative position measure is straightforward, expressing a suitable measure of the relative orientation requires some care. The problem is addressed by computing the Euler vector of the product of the actual and prescribed relative rotation matrices. By arbitrarily combining the error measures in up to six independent equations, a general family of holonomic rheonomic constraints can be formulated. The relative motion between the bodies can be constrained or specified component-wise, respectively, resulting in scleronomic or rheonomic constraints. The proposed formulation is implemented in a free, general-purpose multibody solver; numerical applications to generic mechanical and aerospace problems are presented.     

大规模三角线性方程的高效求解

大规模三角线性方程求解是科学与工程应用中重要的计算核心,受限于处理器的缓存容量和结构设计,其在CPU和GPU等平台上的计算效率不高。大规模三角线性方程的分块求解中,矩阵乘是主要运算,其计算效率对提升三角线性方程求解的计算效率至关重要。以矩阵乘计算效率较高的矩阵乘协处理器为计算平台,针对其结构特点提出了矩阵乘协处理器上大规模三角线性方程分块求解的实现方法和性能分析模型。实验结果表明,矩阵乘协处理器上大规模三角线性方程求解的计算效率最高可达85.9%,其实际性能和资源利用率分别为同等工艺下GPU的2.42倍和10.72倍。     

Explicit smooth/nonsmooth cosimulation using kinematic constraints

Multibody System Dynamics - An explicit cosimulation scheme is developed to study the coupling of smooth and nonsmooth systems using kinematic constraints. Using the force-displacement...     

An interactive data-driven driving simulator using motion blending

Compared to the motion equations the data-driven method can simulate reality from sampling of real motions but real-time interaction between a user and the simulator is problematic. Existing data-driven motion generation methods simply record and replay the motion of the vehicle. Character animation technology enables a user to control motions that are generated by a motion capture database and an appropriate motion control algorithm. We propose a data-driven motion generation method and implement a driving simulator by adapting the method of motion capture. The motion data sampled from a real vehicle are transformed into appropriate data structures called motion blocks, and then a series of motion blocks are saved into the motion database. During simulation, the driving simulator searches for and synthesizes optimal motion blocks from the motion database and generates motion streams that reflect the current simulation conditions and parameterized user demands. We demonstrate the proposed method through experiments with the driving simulator.     

基于虚拟仪器的DRFM干扰模拟器设计

为满足雷达对抗数字射频存储(DRFM)干扰的技术验证和系统测试需求,采用矢量信号收发仪结合DRFM技术设计了一种模块化、可扩展、轻量便携的干扰模拟器,采用一种流控制器实现对干扰模拟器的控制,并通过雷达和干扰模拟器的注入测试验证了设计的有效性。该设计能根据雷达回波产生包括间歇采样转发干扰在内的多种类型雷达干扰信号,能通过更换、扩展板卡实现多种任务功能,可用于雷达测试环境构建,有力支撑了雷达抗干扰技术的研究与验证。     

An efficient dynamical systems method for solving singularly perturbed integral equations with noise

In this paper we apply the dynamical systems method (DSM) proposed by A. G. Ramm, and the variational regularization method (VRM), to obtain numerical solution to some singularly perturbed ill-posed problems contaminated by noise. The results obtained by these methods are compared to the exact solution for the model problems. It is found that the dynamical systems method is preferable because it is easier to apply, highly stable, robust, and it always converges to the solution even for large size models.     

Adams methods for the efficient solution of stochastic differential equations with additive noise

The application of Adams methods for the numerical solution of stochastic differential equations is considered. Especially we discuss the path-wise (strong) solutions of stochastic differential equations with additive noise and their numerical computation. The special structure of these problems suggests the application of Adams methods, which are used for deterministic differential equations very successfully. Applications to circuit simulation are presented.     

Robot manipulator kinematic compensation using a generalized jacobian formulation

The kinematic error compensation of robot manipulators is at present being attempted by improving the precision of the nominal robot kinematic parameters. This paper addresses the problem of kinematic compensation using a new mathematical joint model proposed to account for shortcomings in existing methods. The corrected manipulator transformation is formulated in terms of “generalized Jacobians”: relating differential errors at the joints to the differential change in the manipulator transformation. The details of application are discussed for a particular industrial manipulator.     

An efficient algorithm for solving stiff ordinary differential equations

The Brayton-Gustavson-Hatchel (BGH) method for solving stiff ordinary differential equations belongs to the group of backward difference formulas methods. Basic details of the BGH method are presented. A new implementation with original modifications is described. Special attention is paid to the reduction of operation count and improvement of error control. Two examples including mildly stiff and stiff equation systems prove spectacular superiority of the BGH method with respect to the classic Gear method. The software presented in this paper is scalable and has been ported without any problems from the PC/DOS platform to two UNIX environments.