Closed-loop Chain Research Articles

Probabilistic behaviour of joints on joint forces in mechanisms

This paper discusses the influence of the clearance in joints on the joint reaction forces in mechanisms. By using mathematical programming, the optimal parameters of kinematic chains can be efficiently obtained by using the deterministic approach. However, the situation becomes more sophisticated if random effects of tolerances of the arm lengths and the random pin positions have to be considered. In this work the influence of clearances on joint forces is calculated by using the Taylor approximation and the Monte Carlo method. The implementation of the model is illustrated with two examples. The first example considers a closed loop chain, representing a four-bar mechanism being an actual part of a hydraulic support, employed in mining industry. The second example considers joint reaction forces of car wiper mechanism.

An optimization approach to risk decision-making of closed-loop logistics based on SCOR model

In green logistics operation, all logistics processes form a bidirectional closed-loop topology. In order to model and optimize such a kind of structure, a standardized closed-loop logistics operation reference model is built which aims to provide supply chain managers with general analysis. Based on the reference model, potential risks of closed-loop logistics chain can be analyzed including not only the visible forward and reverse logistics flow but also the invisible information flow. A qualitative decision-making model for different logistics organizations under risk is proposed and a profit function is developed according to logistics management decision-making process of all logistics nodes under different risks. The proposed model considers different risk management strategy problems. The optimization problem is described as a multi-objective decision-making problem with minimization of the risk loss as well as risk management cost and maximization of the profit. The profit model is solved by genetic algorithm. In the model, in order to express uncertainties of different risk preference information, risk is assessed by a three-dimensional vector in priority, probability and loss. A quantified reference model is introduced through a three-dimensional vague vector map, where several information gathering methods based on vague set are discussed and compared through a case study.

Preliminary Study on Process Mapping and Policy Recommendations of the WEEE Closed-loop in China

With high speed of increasement in electrical and electronic products, the relevant wastes turn out to be serious in China. But a corresponding recycling system of WEEE has yet to be established. The actual WEEE flow in China is therefore kind of unknown. Through an in-depth analysis of the recycling system and extended survey of the WEEE recycling process in Beijing, this paper puts forward a WEEE closed loop chain model concerning the source, pathway and volume of the flow. It identified some key control points in the WEEE recycling process, which are taken into account in several policy recommendations.

The Study of Green Evaluation Support System in Manufacturing Process Based on Multi Agent

Owing to the diversity of green evaluation index and multiple-factor related to the process evaluation, existing green evaluation of manufacturing process lacks a set of effective knowledge management model. It leads to the high cost and inefficiency of analysis and evaluation process. A green evaluation model for manufacturing process based on multi agent is presented. Based on the model, green evaluation support system of manufacturing process based on multi agent is developed with the knowledge base introduced. The implementation strategy of green evaluation for manufacturing process is implemented by the closed-loop knowledge chain, which is composed of knowledge mining, knowledge transferring, knowledge application and knowledge feedback. The feasibility of this system is verified by an instance of the valve stem manufacturing process in a valve factory.

Review of biomechanical models for human shoulder complex

The human shoulder plays an important role in human posture and motion, especially in scenarios in which humans need to achieve tasks with external loads. The complexity of the shoulder mechanism makes it difficult to model a shoulder complex realistically. Although many researchers have attempted to model the human shoulder complex, there has not been a survey of these models including their benefits and limitations. This paper attempts to review various biomechanical models proposed and summarise the pros and cons. It focuses mainly on the human modelling domain, although some of these models were originally from the robotics field. The models are divided into three major categories: open-loop chain models, closed-loop chain models and musculoskeletal shoulder models. The open-loop models are the simplest ones to represent the gross structure of the shoulder complex. Closed-loop models are closer to the real structure of the shoulder complex. Musculoskeletal models are more accurate representation of the actual shoulder complex.

Linkage Mechanisms With Cam-Integrated Joints for Controlled Harmonic Content of the Output Motion: Theory and Application

In a recent study, the authors presented a systematic method for the modification of the output motion of linkage mechanisms with closed-loop chains using cams positioned at one or more joints of the mechanism. In this paper, the method is applied to the design of a linkage mechanism with an integrated cam mechanism to eliminate high harmonic component of the output motion. The mechanism may be synthesized using any existing linkage mechanism synthesis technique. In the present study, a cam mechanism is synthesized to eliminate all high harmonic components of the output link motion of a four-bar linkage mechanism to illustrate the potentials of the present approach. The mechanism is then constructed and successfully tested. With the present method, selected ranges of high harmonic motions generated due to the mechanisms kinematics nonlinearity can be eliminated by integrating appropriately designed cams, thereby significantly reducing the potential vibrational excitation that the mechanism can impart on the overall system, including its own structure. Such systems should therefore be capable of operating at higher speeds and with increased precision.

Micro/Macro or Link-Integrated Micro-actuator Manipulation—A Kinematics and Dynamics Perspective

Smart (active) materials based actuators, hereinafter called micro-actuators, have been shown to be well suited for the elimination of high harmonics in joint and/or end-effector motions of robot manipulators and in the reduction of actuator dynamic response requirements. Low harmonic joint and end-effector motions, as well as low actuator dynamic response requirements, are essential for a robot manipulator to achieve high operating speed and precision with minimal vibration and control problems. Micro-actuators may be positioned at the end-effector to obtain a micro- and macro-robot manipulation configuration. Alternatively, micro-actuators may be integrated into the structure of the links to vary their kinematics parameters, such as their lengths during the motion. In this paper, the kinematics and dynamics consequences of each of the aforementioned alternative are studied for manipulators with serial and closed-loop chains. It is shown that for robot manipulators constructed with closed-loop chains, the high harmonic components of all joint motions can be eliminated only when micro-actuators are integrated into the structure of the closed-loop chain links. The latter configuration is also shown to have dynamics advantage over micro- and macro-manipulator configuration by reducing the potential vibration and control problems at high operating speeds. The conclusions reached in this study also apply to closed-loop chains of parallel and cooperating robot manipulators.

Discontinuously Movable Seven-Link Mechanisms Via Group-Algebraic Approach

Combining planar and spherical 4R chains generates three kinds of new discontinuously movable (DM) seven-link mechanisms. The mobility analysis is based on algebraic concepts of set theory. These mechanisms are called hybrid planar-spherical 7R, hybrid spherical-spherical 7R, and hybrid planar-planar 6RIP DM mechanisms. Their discontinuous mobility is explained employing the Lie group algebraic properties of the displacement set. Moreover, the same given spatial arrangement of joints can be linked in two ways constituting two distinct chains, which have a quite different mobility. One chain has two global degrees of freedom (d.o.f.), which disobey the general Grubler-Kutzbach mobility criterion. The other chain exhibits a singular pose, which is a bifurcation towards two distinct working modes of mobility with one d.o.f. Then the set of relative motions between any two specific links is not manifold but consists of the union of displacement one-dimensional manifolds. In general, when two or more subgroups are involved in a closed-loop chain, the discontinuous mobility can happen by changing the order of the kinematic pair linking.

Kinematics Synthesis of Linkage Mechanisms With Cam Integrated Joints for Controlled Harmonic Content of the Output Motion

A new method is presented for the modification of the output motion of linkage mechanisms with closed-loop chains using cams positioned at one or more of its joints. As an example and to present the basic concept, the method is applied to a four-bar linkage mechanism that is synthesized for function generation for the purpose of eliminating the high harmonic component of the output link motion. By eliminating the high harmonic component of the output motion of a mechanism, the potential vibrational excitation that the mechanism can impart on the overall system, including its own structure, is greatly reduced. The resulting system should therefore be capable of operating at higher speeds and with increased precision. For mechanisms with rigid links, the primary source of high harmonics in the output motion is the nonlinearity of the kinematics of their closed-loop chains. With the present method, a selected range or ranges of high harmonic motions generated due to such nonlinearities may be eliminated by integrating appropriately designed cams that are used to vary the effective length of one or more of the links during the motion. A numerical example is provided together with a discussion of the related topics of interest.

Dynamic modeling of structurally-flexible planar parallel manipulator

This paper presents a dynamic model of a planar parallel manipulator including structural flexibility of several linkages. The equations of motion are formulated using the Lagrangian equations of the first type and Lagrangian multipliers are introduced to represent the geometry of multiple closed loop chains. Then, an active damping approach using a PZT actuator is described to attenuate structural vibration of the linkages. Overall dynamic behavior of the manipulator, induced from structural flexibility of the linkage, is well illustrated through simulations. This analysis will be used to develop a prototype parallel manipulator.

Proportional derivative and strain (PDS) boundary feedback control of a flexible space structure with a closed-loop chain mechanism

A simple space truss structure, a rigid connection of two flexible beams, is modeled as a distributed parameter system subject to holonomic constraints. Boundary feedback control synthesis is developed for this structure. The synthesis is carried out in the infinite-dimensional setting, mathematical features of which give rise to a stabilizing PDS control algorithm. Due to simplicity of the implementation, the algorithm becomes extremely attractive under limitations on the computer power in the space. The effectiveness of the control strategy proposed is supported by experimental tests.

A Systematic Method for Kinematics Synthesis of High-Speed Mechanisms With Optimally Integrated Smart Materials

A systematic method is presented for kinematics synthesis of high-speed mechanisms with optimally integrated smart materials based actuators for the purpose of modifying the output link motion. As an example, the method is applied to a four-bar linkage mechanism that is synthesized for function generation to eliminate the high harmonic component of the output link motion. For mechanisms with rigid links, the high harmonic motions are generated due to the nonlinearity of the kinematics of their closed-loop chains. By eliminating the high harmonic component of the output motion, the potential vibrational excitation that the mechanism can impart on the overall system and its own structure is greatly reduced. The resulting system should therefore be capable of operating at higher speeds and with greater precision. A numerical example is provided together with a discussion of the application of the method to other mechanism synthesis problems and some related topics of interest.

Task-specific optimal simultaneous kinematic, dynamic, and control design of high-performance robotic systems

A task-specific optimal simultaneous kinematic, dynamic and control design approach is proposed for high-performance computer-controlled machines, such as robots. This mechatronics design approach is based on the trajectory pattern method and a fundamentally new design philosophy that such machines, in general, and ultrahigh-performance machines, in particular, must only be designed to perform a class or classes of motions effectively. In the proposed approach, given the structure of the manipulator, its kinematic, dynamic, and control parameters are optimized simultaneously with the parameters that describe a selected trajectory pattern with which the desired class(es) of task(s) can best be performed. In one example, a weighted sum of the norms of the higher harmonics appearing in the actuating torques and the integral of the position and velocity tracking errors are used to form the optimality criterion. The selected optimality criterion should yield a system that is optimally designed to accurately follow the specified trajectory at high speed. Other objective functions can be readily formulated to synthesize systems for optimal performance. Based on the developed design methodology, a two-degrees-of-freedom robot manipulator with a closed-loop chain is optimally designed and constructed for point-to-point motions. The preliminary results of experiments indicate that the robot can, in fact, execute point-to-point motions rapidly and with minimal residual vibration. The potentials of the developed method and its implementation for generally defined motion patterns are discussed.

Entanglements in polymers: I. Annealed probability for loops

The effect of the preservation of the topology of the entanglement in systems of polymer loops is investigated. We define a simple two-state linking invariant for a pair of loop polymer chains and show its relationship to the familiar Gaussian linking number. The probability of linking two disjoint sets chosen from a dense melt of closed-loop chains is determined. We discuss the form of the resulting probability and the approximations necessary in obtaining it.

On the Completeness of Kinematic Chains of Mobility Unity

A complete kinematic chain is a chain in which every link of the chain makes contact at a joint with every other link of the chain. Simple closed-loop chains, semicomplete, and complete chains of mobility unity are investigated topologically to determine the limits within which it is possible for all these three kinds of chains to exist. A study is made mainly in terms of: (a) the number of links, l; (b) the number of joints, j; and (c) the degree of that link of the chain whose degree is greatest, Δ. Some brief remarks are made on the application of these ideas to the field of practical machine design.

A compact efficient Schottky collector transistor switch

A vertical Schottky collector transistor switch with merged vertical n-p-n load is described which is useful in both memory and logic applications. The device has been fabricated in an infant oxide isolated bipolar technology with Schottky collector area of 3.8 /spl mu/m/spl times/5.0 /spl mu/m (0.15 mil/spl times/0.2 mil). The intrinsic n-p-n load transistor directly below the Schottky collector requires no additional surface area. Contact location to extrinsic device regions is not restricted, providing wiring flexibility. Current gains of 3 and 4 have been obtained for prototype Schottky collector and n-p-n transistors, respectively. A power-delay product of 60 fJ/V has been observed on a 25-state (fan-out=1) closed-loop inverter chain using 5 /spl mu/m metal lines and spaces. A 5.0 ns delay at 15 /spl mu/A/stage (power-delay product=75 fJ/V) reveals potential for fast, low power VLSI application. The intrinsic speed limit of 2.76 ms is attained at 60 /spl mu/A/stage.

Integrated injection logic-present and future

Integrated injection logic (I/SUP 2/L) or merged transistor logic (MTL) incorporating lateral p-n-p transistors as current sources and multicollector n-p-n transistors as invertors, are discussed. Speed-power products of 0.13 pJ per gate have been measured in a five-stage closed-loop invertor chain, and packing densities of 400 gates/mm/SUP 2/ have been achieved. A layout comparison with MOS logic is presented. A possible way of producing faster circuits is proposed.

Application of Remote Handling in the CPS Tunnel

Two hands and a crane are controlled from the ring centre via 300 m long cables and observed with three closed-loop TV chains. This installation, with more than 30 remote controlled functions, is capable of performing work along 40 m of the PS ring tunnel. The second hand, which has been developed at CERN, executes the more delicate work such as disconnecting ordinary water and electrical cornnectors of different types. One test operation was the removal of a vacuum tank with a septum magnet of the ejection system. Althougn this equipment was not designed for remote handling, only the connection to the power cable could not be removed from a distance. All the other work - vacuum connections to chamber and. pumps, electrical and water connections, lifting out onto a chariot - was done with no one present in the ring tunnel.

Many-body propagators of a self-coupled spinor field in Edwards-Lieb’s approximation

The continuous integral representation of the complete, many-body propagators of a self-coupled spinor field is deduced and investigated. The continuous integrals are calculated by means ofEdwards—Lieb’s non-perturbative approximation method. In first approximation, the physical one-body propagator agrees with the propagator of a free, dressed particle and the physical two-body propagator corresponds to the one obtained in the “closed-loop chain” approximation ofAbrikosov et al.