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.     

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.     

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.     

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.     

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...     

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.     

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.     

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.     

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。     

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.     

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.     

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.     

Comparing CONCEPT and FLOWTRAN using a process simulator evaluator

A test flowsheets has been written to the specifications evolced by a group of engineers with academic and industrial backgrounds. Incorporated into it are features which are known to give problems in simulations. The test flowsheet was evaluated by carrying out a comparison of CONCEPT and FLOWTRAN. It was demonstrated that the test could be used to identify strengths and weaknesses, major and minor. The study revealed a serious weakness in both systems.     

An efficient scheme on wet/dry transitions for shallow water equations with friction

The present work concerns the derivation of a suitable discretization to approximate the friction source terms in the shallow-water model. Such additional source terms are known to be very stiff as soon as the water height is vanishing. The proposed numerical procedure comes from a relevant correction of a Godunov-type scheme that approximates the solutions of hyperbolic systems of conservation laws. The adopted correction gives a discretization of the source term which preserves the robustness and does not change the CFL condition. The scheme is shown to be particularly efficient for wet/dry transition simulations. In addition, this numerical procedure can be used together with any robust and well-balanced discretization of the topography source term. Second order extension is also investigated. Extensive numerical validations illustrate the interest of this new approach.     

An efficient solution procedure for fuzzy relation equations withmax-product composition

We study a system of fuzzy relation equations with max-product composition and present an efficient solution procedure to characterize the whole solution set by finding the maximum solution as well as the complete set of minimal solutions. Instead of solving the problem combinatorially, the procedure identifies the “nonminimal” solutions and eliminates them from the set of minimal solutions     

On efficient computation of highly oscillatory retarded potential integral equations

This paper presents an efficient numerical method for retarded potential integral equations with highly oscillatory spatially time-harmonic incident waves, which is based on inverse Fourier transforms and efficient algorithms for the highly oscillatory Volterra integral equation of the first kind. From the integral equation, it leads to an efficient approximation by applying the Clenshaw–Curtis-type method which costs the same operations independent of large values of frequencies. Applying inverse Fourier transforms yields numerical results on solving the retarded potential integral equations. Preliminary numerical results show the efficiency and accuracy of the approximations.     

Driving saccade to pursuit using image motion

Within the context of active vision, scant attention has been paid to the execution of motion saccades—rapid re-adjustments of the direction of gaze to attend to moving objects. In this paper we first develop a methodology for, and give real-time demonstrations of, the use of motion detection and segmentation processes to initiate capture saccades towards a moving object. The saccade is driven by both position and velocity of the moving target under the assumption of constant target velocity, using prediction to overcome the delay introduced by visual processing. We next demonstrate the use of a first order approximation to the segmented motion field to compute bounds on the time-to-contact in the presence of looming motion. If the bound falls below a safe limit, a panic saccade is fired, moving the camera away from the approaching object. We then describe the use of image motion to realize smooth pursuit, tracking using velocity information alone, where the camera is moved so as to null a single constant image motion fitted within a central image region. Finally, we glue together capture saccades with smooth pursuit, thus effecting changes in both what is being attended to and how it is being attended to. To couple the different visual activities of waiting, saccading, pursuing and panicking, we use a finite state machine which provides inherent robustness outside of visual processing and provides a means of making repeated exploration. We demonstrate in repeated trials that the transition from saccadic motion to tracking is more likely to succeed using position and velocity control, than when using position alone.