18685518
A novel 2-DOF parallel mechanism based design of a new 5-axis hybrid machine tool
In this paper, the concept of a new 5-axis hybrid machine tool is proposed. The machine is a tool being with both parallel and serial structures, which is based on a novel 2-DOF parallel platform and serial orientations. The machine tool has advantages in terms of high stiffness, high dexterity, high speed, and being capable of long components manufacturing. The kinematics characteristics, such as inverse and forward kinematics, conditioning indices, of the novel 2-DOF parallel platform are studied. The dimensional synthesis based on the workspace and conditioning indices is presented. The results of the paper are very useful for the design of the hybrid machine tool.
14450831
Some New Parallel Mechanisms Containing the Planar Four-Bar Parallelogram
A parallelogram allows the output link to remain at a fixed orientation with respect to an input link, for which it acts as a unique role in the design of parallel mechanisms. In this paper, the unique role of a parallelogram is used completely to design some new parallel mechanisms with two to six degrees of freedom (DoFs). In these mechanisms, some with three DoFs possess the advantage of very high rotational capability and some with two DoFs have the translational output of a rigid body. More than that, the design concept is also applied first to some parallel mechanisms to improve the systems' rotational capability. The parallel mechanisms proposed in this paper have wide applications in industrial robots, simulators, micromanipulators, parallel kinematics machines, and any other manipulation devices in which high rotational capability and stiffness are needed. Especially, the paper provides new concepts of the design of novel parallel mechanisms and the improvement of rotational capability for such systems.
3096595
Analysis of a novel cylindrical 3-DoF parallel robot
Abstract In this paper, a novel three degrees of freedom (DoFs), that are two degrees of translational freedom and one degree of rotational freedom, parallel robot is proposed. The parallel robot consists of a base plate, a movable platform, and three connecting legs. Because the locus of any point on the moving platform is the subset of a cylinder if z is specified, the robot is called a cylindrical parallel robot. The inverse and forward kinematics problems are described in closed forms. And the velocity equation of the new parallel robot is given. Three kinds of singularities are presented. The workspace for the robot is analyzed systematically, especially, a new index to evaluate the mobility (In this paper, mobility means rotational capability.) of the moving platform of the robot is defined and discussed in detail. The parallel robot has wide application in the fields of industrial robots, simulators, microrobots and parallel machine tools.
790904
A new three-degree-of-freedom parallel manipulator
In this paper, a novel spatial three degree-of-freedom, that are two degrees of translational freedom and one degree of orientational freedom, parallel manipulator is proposed. The parallel manipulator consists of a base plate, a movable platform, and three non-identical connecting legs. The kinematics problems and velocity equation of the new parallel manipulator are given. Three kinds of singularities are presented. The parallel manipulator has wide application in the fields of industrial robots, motion simulators, and parallel kinematics machines.
33701205
Inverse dynamics and simulation of a 3-DOF spatial parallel manipulator
Recently the parallel manipulators with less DOF have attracted the researchers, but works on their dynamics are relative few. In this paper, an inverse dynamic formulation is presented by the Newton-Euler approach for a spatial parallel manipulator, which has two translational degrees of freedom and one rotational degree of freedom. The inverse kinematics analysis is firstly performed in closed form. Then the force and moment equilibrium equations for the manipulator are presented. According to the kinematic constraints of the legs and the platform, some joint constraint forces are eliminated and an algorithm to solve the actuator forces is given. In addition, ADAMS is used to perform the kinematic and dynamic simulation for the manipulator. The simulation results are compared to those derived from algebraic formulae and the comparison shows the validity of the mathematical model.
7114960
On the optimum design of planar 3-DOF parallel manipulators with respect to the workspace
The design of the robotic mechanisms is one of the most important activities, because these mechanisms determine the performance characteristics of the robots. The paper concerns the issue of computer-aided design (CAD) for planar 3-DOF parallel robotic mechanisms by means of the physical model of the solution space, which can be used systematically to express the relationships between the performance criteria and all link lengths of one type of the robotic mechanism. The performance atlases of the workspace volume for the manipulators are plotted in the physical model of the solution space. The characteristics of the distribution of the workspace shapes in the physical model of the solution space are presented. The results are useful for the optimum design of the robotic mechanisms. The paper proposes a new way for the robotic CAD.
426496
Freeze: engineering a fast repeater insertion solver for power minimization using the ellipsoid method
This paper presents a novel repeater insertion algorithm for the power minimization of realistic interconnect trees under given timing budgets. Our algorithm judiciously combines a local optimizer based on the dynamic programming technique and a global search engine using the ellipsoid method. As a result, our approach is capable of producing high-quality solutions at a very fast speed. Furthermore, our scheme is robust and does not need any manual tuning of the iteration-control parameters. We have developed a repeater insertion tool, called Freeze, using the proposed algorithm and applied it to various interconnect trees with different timing targets. Experimental results demonstrate the high effectiveness of our approach. In comparison with the state-of-the-art low-power repeater insertion schemes, Freeze requires 5.8 times fewer iterations on the average, achieving up to 27 times speedup with even better power savings. When compared with a dynamic programming based scheme, which guarantees the optimal solution, our tool delivers up to 50 times speedup with 0.9% power increase on the average.
32095656
Analyzing Outliers Cautiously
Outliers are difficult to handle because some of them can be measurement errors, while others may represent phenomena of interest, something "significant" from the viewpoint of the application domain. Statistical and computational methods have been proposed to detect outliers, but further analysis of outliers requires much relevant domain knowledge. In our previous work (1994), we suggested a knowledge-based method for distinguishing between the measurement errors and phenomena of interest by modeling "real measurements" - how measurements should be distributed in an application domain. In this paper, we make this distinction by modeling measurement errors instead. This is a cautious approach to outlier analysis, which has been successfully applied to a medical problem and may find interesting applications in other domains such as science, engineering, finance, and economics.
2869410
UMass at TREC 2003: HARD and QA
Abstract : The Center for Intelligent Information Retrieval (CIIR) at UMass Amherst participated in two tracks for TREC 2003: High Accuracy Retrieval from Documents (HARD) and Question Answering (QA). In the HARD track, we developed document metadata to correspond to query metadata requirements; implemented clarification forms based on query expansion, passage retrieval, and clustering; and retrieved variable length passages deemed most likely to be relevant. This work is discussed at length in Section 1. In the QA track, we focused on retrieving passages that were likely to contain the answer to the question. In the QA track, we developed a dynamic passaging retrieval system to identify passages likely to contain answers. CIIR last participated in the QA task in TREC 9 (2000). At that time we fielded the Marsha system [11]. This system was based on an INQUERY document retrieval engine followed by the application of a series of heuristics rules to identify 250-byte long passages in the retrieved documents that were likely to contain the desired answers. This year's passage sub-task in the QA track has allowed us to participate once again utilizing our current approach to passage retrieval with language models. We developed a dynamic passaging system that retrieved document passages based on the simplest implementation of language models: cross-entropy between bag-of-word models for a question and a candidate passage.
848425
Location awareness in unstructured peer-to-peer systems
Peer-to-peer (P2P) computing has emerged as a popular model aiming at further utilizing Internet information and resources. However, the mechanism of peers randomly choosing logical neighbors without any knowledge about underlying physical topology can cause a serious topology mismatch between the P2P overlay network and the physical underlying network. The topology mismatch problem brings great stress in the Internet infrastructure. It greatly limits the performance gain from various search or routing techniques. Meanwhile, due to the inefficient overlay topology, the flooding-based search mechanisms cause a large volume of unnecessary traffic. Aiming at alleviating the mismatching problem and reducing the unnecessary traffic, we propose a location-aware topology matching (LTM) technique. LTM builds an efficient overlay by disconnecting slow connections and choosing physically closer nodes as logical neighbors while still retaining the search scope and reducing response time for queries. LTM is scalable and completely distributed in the sense that it does not require any global knowledge of the whole overlay network. The effectiveness of LTM is demonstrated through simulation studies.
5760140
Reliable control design of fuzzy dynamic systems with time-varying delay
This paper focuses on the reliable fuzzy control design problem for fuzzy control systems with time delay. Based on linear matrix inequality (LMI) approach, a method for designing a reliable fuzzy controller is presented. The resulting fuzzy control systems are reliable in the sense that asymptotic stability is achieved not only when all control components are operating well, but also in the presence of some component failures. A reliable fuzzy control design scheme via state feedback is proposed in terms of LMIs. The result is extended to the case of observer-based reliable fuzzy control. Two illustrative examples are given to illustrate the validity of the proposed design procedures.