Showing papers in "Robotics and Computer-integrated Manufacturing in 2011"
TL;DR: In this paper, a robust and fast procedure that can be used to identify the joint stiffness values of any six-revolute serial robot is introduced, where the links of the robot are assumed to be much stiffer than its actuated joints.
Abstract: Although robots tend to be as competitive as CNC machines for some operations, they are not yet widely used for machining operations. This may be due to the lack of certain technical information that is required for satisfactory machining operation. For instance, it is very difficult to get information about the stiffness of industrial robots from robot manufacturers. As a consequence, this paper introduces a robust and fast procedure that can be used to identify the joint stiffness values of any six-revolute serial robot. This procedure aims to evaluate joint stiffness values considering both translational and rotational displacements of the robot end-effector for a given applied wrench (force and torque). In this paper, the links of the robot are assumed to be much stiffer than its actuated joints. The robustness of the identification method and the sensitivity of the results to measurement errors and the number of experimental tests are also analyzed. Finally, the actual Cartesian stiffness matrix of the robot is obtained from the joint stiffness values and can be used for motion planning and to optimize machining operations.
255 citations
TL;DR: An overview of the surgical robotics field is presented, highlighting significant milestones and grouping the various propositions into cohorts to highlight how surgical robotics is acting as an enabling technology for minimally invasive surgery.
Abstract: This paper presents an overview of the surgical robotics field, highlighting significant milestones and grouping the various propositions into cohorts. The review does not aim to be exhaustive but rather to highlight how surgical robotics is acting as an enabling technology for minimally invasive surgery. As such, there is a focus on robotic surgical solutions which are commercially available; research efforts which have not gained regulatory approval or entered clinical use are mostly omitted. The practice of robotic surgery is currently largely dominated by the da Vinci system of Intuitive Surgical (Sunnyvale, CA, USA) but other commercial players have now entered the market with surgical robotic products or are appearing in the horizon with medium and long term propositions. Surgical robotics is currently a vibrant research topic and new research directions may lead to the development of very different robotic surgical devices in the future-small, special purpose, lower cost, possibly disposable robots rather than the current large, versatile and capital expensive systems. As the trend towards minimally invasive surgery (MIS) increases, surgery becomes more technically demanding for surgeons and more challenging for medical device technologists and it is clear that surgical robotics has now an established foothold in medicine as an enabling technology of MIS.
195 citations
TL;DR: The results show that the new approach has a high Hit rate and that the robot succeeded to reach its target in a collision free path in most cases which is the most desirable feature in any navigation algorithm.
Abstract: In this paper, a new approach is developed for solving the problem of mobile robot path planning in an unknown dynamic environment based on Q-learning. Q-learning algorithms have been used widely for solving real world problems, especially in robotics since it has been proved to give reliable and efficient solutions due to its simple and well developed theory. However, most of the researchers who tried to use Q-learning for solving the mobile robot navigation problem dealt with static environments; they avoided using it for dynamic environments because it is a more complex problem that has infinite number of states. This great number of states makes the training for the intelligent agent very difficult. In this paper, the Q-learning algorithm was applied for solving the mobile robot navigation in dynamic environment problem by limiting the number of states based on a new definition for the states space. This has the effect of reducing the size of the Q-table and hence, increasing the speed of the navigation algorithm. The conducted experimental simulation scenarios indicate the strength of the new proposed approach for mobile robot navigation in dynamic environment. The results show that the new approach has a high Hit rate and that the robot succeeded to reach its target in a collision free path in most cases which is the most desirable feature in any navigation algorithm.
187 citations
TL;DR: The kinematic characteristics of this new machine tool is investigated, the concise models of forward and inverse kinematics have been developed and these models can be used to evaluate the performances of an existing Exechon machine tool and to optimize new structures of an ExECHon machine to accomplish some specific tasks.
Abstract: The studies on PKMs have attracted a great attention to robotics community. By deploying a parallel kinematic structure, a parallel kinematic machine (PKM) is expected to possess the advantages of heavier working load, higher speed, and higher precision. Hundreds of new PKMs have been proposed. However, due to the considerable gaps between the desired and actual performances, the majorities of the developed PKMs were the prototypes in research laboratories and only a few of them have been practically applied for various applications; among the successful PKMs, the Exechon machine tool is recently developed. The Exechon adopts unique over-constrained structure, and it has been improved based on the success of the Tricept parallel kinematic machine. Note that the quantifiable theoretical studies have yet been conducted to validate its superior performances, and its kinematic model is not publically available. In this paper, the kinematic characteristics of this new machine tool is investigated, the concise models of forward and inverse kinematics have been developed. These models can be used to evaluate the performances of an existing Exechon machine tool and to optimize new structures of an Exechon machine to accomplish some specific tasks.
160 citations
TL;DR: A review of computer-aided fixture design (CAFD) tools and approaches can be found in this paper, where the main focus is on supporting the detailed design of a fixture's physical structure.
Abstract: A key characteristic of the modern market place is the consumer demand for variety. To respond effectively to this demand, manufacturers need to ensure that their manufacturing practices are sufficiently flexible to allow them to achieve rapid product development. Fixturing, which involves using fixtures to secure workpieces during machining so that they can be transformed into parts that meet required design specifications, is a significant contributing factor towards achieving manufacturing flexibility. To enable flexible fixturing, considerable levels of research effort have been devoted to supporting the process of fixture design through the development of computer-aided fixture design (CAFD) tools and approaches. This paper contains a review of these research efforts. Over seventy-five CAFD tools and approaches are reviewed in terms of the fixture design phases they support and the underlying technology upon which they are based. The primary conclusion of the review is that while significant advances have been made in supporting fixture design, there are primarily two research issues that require further effort. The first of these is that current CAFD research is segmented in nature and there remains a need to provide more cohesive fixture design support. Secondly, a greater focus is required on supporting the detailed design of a fixture's physical structure.
145 citations
TL;DR: In this article, Canny edge detection of the robotic MAG beads was carried out and the data were smoothed with a Gaussian filter and fitted with Gaussian function, logistic function, parabola function and sine function, respectively.
Abstract: As a deposition technology, robotic metal active gas (MAG) welding has shown new promises for rapid prototyping (RP) of metallic parts. During the process of forming metal parts with the robotic MAG welding technology, the sectional geometry of single-pass bead and the overlap of the adjacent beads have critical effects on the dimensional accuracy and quality of metal parts. In this work, Canny edge detection of the robotic MAG beads was carried out and the data were smoothed with a Gaussian filter and fitted with Gaussian function, logistic function, parabola function and sine function, respectively. In addition, a mathematical model of bead section was developed to analyze the bead geometry. Based on ''surfacing of equivalent area'' method, the concept of overlapping coefficient and optimum-overlapping coefficient was put forward, and calculated model of overlapping was analyzed. Optimal overlapping coefficient was calculated to be 63.66% under experimental condition. The conclusion is that the edge detection of bead section with Canny operator is continuous and distinct, and as compared with Gaussian function, logistic function and parabola function, sine function has higher accuracy to fit the measured data, and ''surfacing of equivalent area'' method shows to be rational and feasible by the experiments.
125 citations
TL;DR: This paper aims to integrate didactically some engineering concepts to understand and teach the screw- based methods applied to the kinematic modeling of robot manipulators, including a comparative analysis between these and the Denavit-Hartenberg-based methods.
Abstract: This paper aims to integrate didactically some engineering concepts to understand and teach the screw-based methods applied to the kinematic modeling of robot manipulators, including a comparative analysis between these and the Denavit-Hartenberg-based methods. In robot analysis, kinematics is a fundamental concept to understand, since most robotic mechanisms are essentially designed for motion. The kinematic modeling of a robot manipulator describes the relationship between the links and joints that compose its kinematic chain. To do so, the most popular methods use the Denavit-Hartenberg convention or its variations, presented by several author and robot publications. This uses a minimal parameter representation of the kinematic chain, but has some limitations. The successive screw displacements method is an alternative representation to this classic approach. Although it uses a non-minimal parameter representation, this screw-based method has some advantages over Denavit-Hartenberg. Both methods are here presented and compared, concerning direct/inverse kinematics of manipulators. The differential kinematics is also discussed. Examples of kinematic modeling using both methods are presented in order to ease their comparison.
121 citations
TL;DR: A comprehensive review of existing virtual manufacturing systems can be found in this article, where the focus and approaches (i.e. virtual reality, web-based techniques, mathematical modelling, hardware interactions and STEP-NC-based methodologies) are discussed in detail.
Abstract: Virtual manufacturing systems provide a useful means for products to be manufactured 'right the first time' without the need of physical testing on the shop floor. Earlier research was mostly on developing a virtual manufacturing environment. Over the years, simple graphical prediction and simulation gave way to complex multi-science predictions. Virtual systems such as Virtual Machine Tool, Virtual Machining, Virtual Assembly, Virtual Tooling and Virtual Prototype have been developed to support virtual manufacturing. Different systems and approaches have different targeted applications. This paper aims to provide a comprehensive review of existing virtual systems. Their focuses and approaches (i.e. virtual reality, Web-based techniques, mathematical modelling, hardware interactions and STEP-NC-based methodologies) are discussed in detail. To better understand the systems, we have categorized them into different groups according to their application domains. Discussions and concluding remarks are given based on the review.
115 citations
TL;DR: In this article, a micro-scale manipulator based on a six-DOF compliant parallel mechanism (CPM), which is featured by piezo-driven actuators and integrated force sensor capable of delivering sixDOF motions with high precision and providing real-time force information for feedback control, is presented.
Abstract: This paper describes the design of a micro-scale manipulator based on a six-DOF compliant parallel mechanism (CPM), which is featured by piezo-driven actuators and integrated force sensor capable of delivering six-DOF motions with high precision and providing real-time force information for feedback control Particularly, the position and screw-based Jacobian analyses of the CPM are presented Then, the compliance model and the workspace evaluation of the CPM are proposed in order to account for the compliance and obtain design guidelines Finally, the integrated sensor is introduced The static features of such a mechanism include high positioning accuracy, structural compactness and smooth and continuous displacements
95 citations
TL;DR: In this article, a robot manipulator's joints are tested with prescribed trajectory end-effectors for the different joints speeds and noise and vibration of each joint are measured, and then, the related parameters are test with neural network predictor to predict servicing period.
Abstract: Nowadays, gas welding applications on vehicle's parts with robot manipulators have increased in automobile industry. Therefore, the speed of end-effectors of robot manipulator is affected on each joint during the welding process with complex trajectory. For that reason, it is necessary to analyze the noise and vibration of robot's joints for predicting faults. This paper presents an experimental investigation on a robot manipulator, using neural network for analyzing the vibration condition on joints. Firstly, robot manipulator's joints are tested with prescribed of trajectory end-effectors for the different joints speeds. Furthermore, noise and vibration of each joint are measured. And then, the related parameters are tested with neural network predictor to predict servicing period. In order to find robust and adaptive neural network structure, two types of neural predictors are employed in this investigation. The results of two approaches improved that an RBNN type can be employed to predict the vibrations on industrial robots.
95 citations
TL;DR: In this article, a framework for an assembly-oriented design (AOD) approach as a new functional product lifecycle management (PLM) strategy, by considering product design and assembly sequence planning phases concurrently, is described.
Abstract: The paper describes a novel framework for an assembly-oriented design (AOD) approach as a new functional product lifecycle management (PLM) strategy, by considering product design and assembly sequence planning phases concurrently. Integration issues of product life cycle into the product development process have received much attention over the last two decades, especially at the detailed design stage. The main objective of the research is to define assembly sequence into preliminary design stages by introducing and applying assembly process knowledge in order to provide an assembly context knowledge to support life-oriented product development process, particularly for product structuring. The proposed framework highlights a novel algorithm based on a mathematical model integrating boundary conditions related to DFA rules, engineering decisions for assembly sequence and the product structure definition. This framework has been implemented in a new system called PEGASUS considered as an AOD module for a PLM system. A case study of applying the framework to a catalytic-converter and diesel particulate filter sub-system, belonging to an exhaust system from an industrial automotive supplier, is introduced to illustrate the efficiency of the proposed AOD methodology.
TL;DR: The proposed framework is demonstrated through a smart forklift gateway around which smart objects are deployed and real-time data are collected by smart objects from the shop floor and processed by the corresponding gateway for further application in enterprise information systems (EISs).
Abstract: In ubiquitous manufacturing (UM) environment, radio frequency identification (RFID) technology enables real-time traceability, visibility and interoperability in improving the performance of shop-floor planning, execution and control. This paper presents an innovative gateway technology. A gateway is physically composed of smart objects that are logically related to each other according to a shop-floor workflow configuration. Although smart objects are equipped with heterogeneous RFID devices, they are converted into standard web services using the concept of agents. The resulted agent-based smart objects (ASOs) are then centrally managed through a specially purposed smart objects Universal Description, Discovery and Integration registry (SO-UDDI) where facilities such as register, publish, find, bind and invoke are provided for ASOs. Through these facilities, smart objects can be deployed at a gateway in a ''Plug and Play'' fashion. Real-time data are collected by smart objects from the shop floor and processed by the corresponding gateway for further application in enterprise information systems (EISs). The proposed framework is demonstrated through a smart forklift gateway around which smart objects are deployed.
TL;DR: In this article, an adaptive robust tracking controller for WMRs is proposed to cope with both parametric and nonparametric uncertainties in the robot model, where an adaptive nonlinear control law is designed based on input-output feedback linearization technique to get asymptotically exact cancellation of the parametric uncertainty in the WMR parameters.
Abstract: In this paper, the integrated kinematic and dynamic trajectory tracking control problem of wheeled mobile robots (WMRs) is addressed. An adaptive robust tracking controller for WMRs is proposed to cope with both parametric and nonparametric uncertainties in the robot model. At first, an adaptive nonlinear control law is designed based on input-output feedback linearization technique to get asymptotically exact cancellation of the parametric uncertainty in the WMR parameters. The designed adaptive feedback linearizing controller is modified by two methods to increase the robustness of the controller: (1) a leakage modification is applied to modify the integral action of the adaptation law and (2) the second modification is an adaptive robust controller, which is included to the linear control law in the outer loop of the adaptive feedback linearizing controller. The adaptive robust controller is designed such that it estimates the unknown constants of an upper bounding function of the uncertainty due to friction, disturbances and unmodeled dynamics. Finally, the proposed controller is developed for a type (2, 0) WMR and simulations are carried out to illustrate the robustness and tracking performance of the controller.
TL;DR: In this article, an interactive control scheme is developed to suppress the vibrations of a welding torch during the welding of novice welders, using an air-paint brush and a haptic-robot.
Abstract: This paper presents a first attempt to assist manual welding with a physically interactive robot. An interactive control scheme is developed to suppress the vibrations of torch during the welding of novice welders. The torch is attached to the end-effector of a haptic-robot. Human and robot act together on the welding torch: the human controls the direction and speed; the robot suppresses the sudden and abrupt motions. The control scheme is developed by experimenting with an air-paint-brush. The painting process emulates the actual welding. Such an emulating environment is useful to surmount the difficulties of experimentation with actual welding. The impedance parameters of the control scheme are investigated. A damping value is determined for an effective vibration suppression and minimum human effort. A variable impedance control scheme is applied to ease the manipulation of the torch while not welding. The results of real welding of novice welders with and without robot assistance are presented. There is a considerable improvement in the performance of the welders when they are assisted with the robot.
TL;DR: In this article, the 3-PRS parallel mechanism is classified into seven subcategories based on the geometrical arrangements of limbs and the complexity of parasitic motion is determined by the limb arrangement.
Abstract: The 3-PRS parallel mechanism (PM) is an important category of lower-mobility parallel mechanisms. Because it can undergo one translational degree of freedom (DOF) and two rotational DOFs, the 3-PRS PM has great potential in practical application and has received extensive attention. Parasitic motion occurring in the constrained DOFs of a 3-PRS PM is a key issue affecting its application. First, the 3-PRS PM is classified into seven subcategories based on the geometrical arrangements of limbs. Then, parasitic motion of each subcategory is discussed in detail and case studies are presented. It is illustrated that the complexity of parasitic motion of the 3-PRS PM is determined by the limb arrangement. The architecture of the 3-PRS PM without parasitic motion is also identified.
TL;DR: In this article, recursive matrix relations in kinematics and dynamics of the 6-6 Stewart-Gough parallel manipulator having six mobile prismatic actuators are established. And the inverse dynamics problem is solved using an approach based on the principle of virtual work, but it has been verified the results in the framework of the Lagrange equations with their multipliers.
Abstract: Recursive matrix relations in kinematics and dynamics of the 6-6 Stewart-Gough parallel manipulator having six mobile prismatic actuators are established in this paper. Controlled by six forces, the manipulator prototype is a spatial six-degrees-of-freedom mechanical system with six parallel legs connecting to the moving platform. Knowing the position and the general motion of the platform, we develop first the inverse kinematics problem and determine the position, velocity and acceleration of each manipulator's link. Further, the inverse dynamics problem is solved using an approach based on the principle of virtual work, but it has been verified the results in the framework of the Lagrange equations with their multipliers. Finally, compact matrix relations and graphs of simulation for the input velocities and accelerations, the input forces and powers are obtained.
TL;DR: In this paper, a novel macro/micro 3-DOF parallel platform is proposed for micro positioning applications, where the kinematics model of the dual parallel mechanism system is established by the stiffness model with individual wide-range flexure hinge and the vector-loop equation.
Abstract: In recent years, nanotechnology has been developing rapidly due to its potential applications in various fields that new materials and products are produced. In this paper, a novel macro/micro 3-DOF parallel platform is proposed for micro positioning applications. The kinematics model of the dual parallel mechanism system is established by the stiffness model with individual wide-range flexure hinge and the vector-loop equation. The inverse solutions and parasitic rotations of the moving platform are obtained and analyzed, which are based on a parallel mechanism with real parameters. The reachable and usable workspace of the macro motion and micro motion of the mechanism are plotted and analyzed. Finally, based on the analysis of parasitic rotations and usable workspace of micro motion, an optimization for the parallel manipulator is presented. The investigations of this paper will provide suggestions to improve the structure and control algorithm optimization for the dual parallel mechanism in order to achieve the features of both larger workspace and higher motion precision.
TL;DR: In this paper, two inspection modules for an automatic solder joint classification system are proposed, which includes illumination normalisation, localisation and segmentation, and the back-end inspection involves the classification of solder joints using the Log-Gabor filter and classifier fusion.
Abstract: Inspection of solder joints has been a critical process in the electronic manufacturing industry to reduce manufacturing cost, improve yield, and ensure product quality and reliability. This paper proposes two inspection modules for an automatic solder joint classification system. The ''front-end'' inspection system includes illumination normalisation, localisation and segmentation. The ''back-end'' inspection involves the classification of solder joints using the Log-Gabor filter and classifier fusion. Five different levels of solder quality with respect to the amount of solder paste have been defined. The Log-Gabor filter has been demonstrated to achieve high recognition rates and is resistant to misalignment. This proposed system does not need any special illumination system, and the images are acquired by an ordinary digital camera. This system could contribute to the development of automated non-contact, non-destructive and low cost solder joint quality inspection systems.
TL;DR: A geometric representation for human operators and robotic manipulators, which cooperate in the development of flexible tasks, which is composed of a set of bounding volumes based on swept-sphere line primitives, which encapsulate their links more precisely than previous sphere-based models.
Abstract: This paper presents a geometric representation for human operators and robotic manipulators, which cooperate in the development of flexible tasks. The main goal of this representation is the implementation of real-time proximity queries, which are used by safety strategies for avoiding dangerous collisions between humans and robotic manipulators. This representation is composed of a set of bounding volumes based on swept-sphere line primitives, which encapsulate their links more precisely than previous sphere-based models. The radius of each bounding volume does not only represent the size of the encapsulated link, but it also includes an estimation of its motion. The radii of these dynamic bounding volumes are obtained from an algorithm which computes the linear velocity of each link. This algorithm has been implemented for the development of a safety strategy in a real human-robot interaction task.
TL;DR: A novel three degrees-of-freedom (DOFs) actuation redundant parallel manipulators is introduced and it is concluded that @n-SVM with a linear kernel function has the best performance to estimate the forward kinematic mapping of a parallel manipulator.
Abstract: Kinematic analysis is one of the key issues in the research domain of parallel kinematic manipulators. It includes inverse kinematics and forward kinematics. Contrary to a serial manipulator, the inverse kinematics of a parallel manipulator is usually simple and straightforward. However, forward kinematic mapping of a parallel manipulator involves highly coupled nonlinear equations. Therefore, it is more difficult to solve the forward kinematics problem of parallel robots. In this paper, a novel three degrees-of-freedom (DOFs) actuation redundant parallel manipulator is introduced. Different intelligent approaches, which include the Multilayer Perceptron (MLP) neural network, Radial Basis Functions (RBF) neural network, and Support Vector Machine (SVM), are applied to investigate the forward kinematic problem of the robot. Simulation is conducted and the accuracy of the models set up by the different methods is compared in detail. The advantages and the disadvantages of each method are analyzed. It is concluded that @n-SVM with a linear kernel function has the best performance to estimate the forward kinematic mapping of a parallel manipulator.
TL;DR: In this paper, the authors describe the design, integration, simulations, and field testing trials of a new type of welding robotic system, the RRXC, which is composed of a 6-axis modularized controller, a 3P3R serial manipulator, and an auxiliary transportation device.
Abstract: Over the last few decades, there have been a large number of attempts to automate welding in the shipbuilding process. However, there are still many non-automated welding operations in the double-hulled blocks, even though it presents an extremely hazardous environment for the workers. And, the hazards come about mainly because of the dimensional constraints of the access-hole. Thus, much effort has been recently directed toward the research on compact design of the fully-autonomous robot working inside of the double-hulled structures. This paper describes the design, integration, simulations, and field testing trials of a new type of welding robotic system, the RRXC, which is composed of a 6-axis modularized controller, a 3P3R serial manipulator, and an auxiliary transportation device. The entire cross section of the RRXC is small enough to be placed inside the double-hulled structures via a conventional access hole of 500x700mm^2, from the outside shipyard floor. The weight of the manufactured RRXC is 60kg, with a 6-axis manipulator and modularized controller, and the weight of an auxiliary transportation device is 8kg, with a 2.5m steel wire of [email protected] Throughout the field tests in the enclosed structures of shipbuilding, the developed RRXC has successfully demonstrated welding functions without the use of any additional finishing by manual welders, and has shown good mobility using an auxiliary transportation device in double-hulled structures.
TL;DR: A kind of feed-axis gearbox condition monitoring system using the built-in position sensors such as motor encoders and linear scales with high resolution and high precision, which is more directly related to machine dynamics and is sensitive to the early and weak fault.
Abstract: This paper describes a kind of feed-axis gearbox condition monitoring system using the built-in position sensors such as motor encoders and linear scales with high resolution and high precision, which is more directly related to machine dynamics and is sensitive to the early and weak fault. To obtain the position information, several data acquisition approaches for open numerical control systems (NCs) and commercial NCs are suggested. Then, the mathematical models between the faults and the position signals are thoroughly investigated. Finally, the ensemble empirical mode decomposition (EEMD) method is introduced to localize the fault of the feed-axis gearbox. The experimental results show that it is effective to use built-in position sensors and EEMD method for on-line monitoring the gearbox state and fault diagnosis.
TL;DR: A self-adaptation system is presented in replacement of the low-effective manual tuning of weights, integrated into the twist decomposition algorithms, and is successfully applied to the examples of joint-limits and singularity avoidances as secondary task.
Abstract: Kinematic redundancy of a pair of manipulator-task can be classified into intrinsic and functional redundancies. With the help of redundancy, the manipulator is able to approximate a secondary task while completing the main task. However, the success of the redundancy resolution relies on a proper choice of weights, that plays an important role in balancing the different components of the secondary task. In order to ensure the fulfillment of both the main and secondary tasks, the weights have to be tuned for each given manipulator-task. In this paper, a self-adaptation system is presented in replacement of the low-effective manual tuning of weights. The self-adaptation system is integrated into the twist decomposition algorithms, and is successfully applied to the examples of joint-limits and singularity avoidances as secondary task.
TL;DR: In this paper, the authors present an industrial application of simulation-based optimization (SBO) in the scheduling and real-time rescheduling of a complex machining line in an automotive manufacturer in Sweden.
Abstract: This paper presents an industrial application of simulation-based optimization (SBO) in the scheduling and real-time rescheduling of a complex machining line in an automotive manufacturer in Sweden. Apart from generating schedules that are robust and adaptive, the scheduler must be able to carry out rescheduling in real time in order to cope with the system uncertainty effectively. A real-time scheduling system is therefore needed to support not only the work of the production planner but also the operators on the shop floor by re-generating feasible schedules when required. This paper describes such a real-time scheduling system, which is in essence a SBO system integrated with the shop floor database system. The scheduling system, called OPTIMISE scheduling system (OSS), uses real-time data from the production line and sends back expert suggestions directly to the operators through Personal Digital Assistants (PDAs). The user interface helps in generating new schedules and enables the users to easily monitor the production progress through visualization of production status and allows them to forecast and display target performance measures. Initial results from this industrial application have shown that such a novel scheduling system can help both in improving the line throughput efficiently and simultaneously supporting real-time decision making.
TL;DR: This paper presents a comparison study on the dynamics of three planar 3-DOF parallel manipulators, one with 3-RRR structure, and the other two with 2- RRR and 4-RRr structures, and shows that the 2-RRS parallel manipulator has the worst dynamic performance.
Abstract: This paper presents a comparison study on the dynamics of three planar 3-DOF parallel manipulators, one with 3-RRR structure, and the other two with 2-RRR and 4-RRR structures. The inverse kinematics and Jacobian matrix of these mechanisms are analyzed. The dynamic formulations in the linear form are derived and a dynamic performance index is given to compare their dynamic performances. The results show that the 2-RRR parallel manipulator has the worst dynamic performance.
TL;DR: An accurate contour error estimation procedure for three-dimensional machining tasks is proposed based on an iterative estimation of the instantaneous curvature of the reference trajectory and coordinates transformation approach, and hence, it is effective for complex reference trajectories with high curvatures.
Abstract: Recently, there has been a growth of interest in high precision machining in multi-axis feed drive systems, subjected to problems such as friction, cutting force and incompatibility of individual driving axis dynamics. To guarantee high precision machining in modern computer numerical controlled (CNC) machines, CNC's controllers do its control efforts to reduce contour error. One of the common approaches is to design a controller based on the estimation of contour error in real time. However, for complex contours with severe curvatures, there is a lack of effective algorithms to calculate contour errors accurately. To address this problem, this paper proposes an accurate contour error estimation procedure for three-dimensional machining tasks. The proposed method is based on an iterative estimation of the instantaneous curvature of the reference trajectory and coordinates transformation approach, and hence, it is effective for complex reference trajectories with high curvatures. In addition, contour error controller is presented to reduce the estimated contour error. The feasibility and superiority of the proposed model as well as contour error controller are demonstrated through experimental system using a desk-top three-axis CNC machine.
TL;DR: In this paper, the authors propose the development of factory templates to address the design and operation practices throughout the entire life cycle of the factory, including the creation and creation of a factory, its remodelling and even the disassembly and recycling stages.
Abstract: The global industry is currently facing a growing increase in the competitiveness that forces companies to adopt and develop new strategies and methods of production. Therefore, one of the most relevant challenges in manufacturing engineering is innovatively integrating Product, Process and Factory dimensions and life cycles, in a holistic approach, from design to recycling/disposal and reuse. The challenge faced here is the synchronization and simultaneous generation of all three-domain models by integrating manufacturing engineering knowledge into the early stage of the modelling and planning processes. The next generation of factories has to be modular, scalable, flexible, open, agile and knowledge-based in order to be able to adapt, in real time, to the continuously changing market demands, technology options and regulations. Therefore, integration, flexibility and efficiency requirements and the ability to simulate the production life cycle of a factory play a crucial role in decreasing ramp-up and design times. Furthermore they play a crucial role in improving the performance in the evaluation and reconfiguration of new or existing facilities, in supporting management decisions and providing tools that can guarantee real-time performance monitoring. Therefore, it is necessary to research and implement the underlying models and ideas during the foundation stage of a new conceptual framework, which is designed to be implemented in the next generation of factories. This will be supported by suitable Information and Communication Technologies (ICT) and digital infrastructures and should lay down the foundations for future applications in this research area-the industrial paradigm of ''Factory as a Product''. In line with the context presented here, we propose the development of factory templates to address the design and operation practices throughout the entire life cycle of the factory. Different dimensions of the factory templates are presented in this paper; they cover the design and creation of the factory, its remodelling and even the disassembly and recycling stages. This entire study takes into account relevant factors such as costs, quality, time, flexibility, environmental and social issues and energy efficiency. Throughout the article, different kinds of models are presented, which describe and adjust the structure of the analysis, design and development of a factory integration project that helps provide a formal analysis of the system. Furthermore, templates integrating the factory's response to internal and external disturbances will also be developed.
TL;DR: In this paper, a generic procedure model and a specification technique for the integrative development of mechatronic products and their production systems are presented, which can be used to deal with the stated problem.
Abstract: The increasing penetration of mechanical engineering by information technology enables considerable benefits. The arising new discipline is referred to by the term mechatronics, which expresses the close integration of mechanics, electrics/electronics, control engineering and software engineering. Hence, the design and production of such systems is an interdisciplinary and complex task. An effective and continuous cooperation and communication between developers from different domains during the whole development process is required. Moreover, the multidisciplinary and synergetic effectiveness of mechatronic systems as well as new production technologies cause strong interdependencies between system parts, which are to be produced. As a consequence, the production system determines the product concept. Restrictions by manufacturing technologies have to be considered already during the early stages of the product development. This contribution deals with the stated problem by providing both, a generic procedure model and a specification technique for the integrative development of mechatronic products and their production systems.
TL;DR: In this paper, an intelligent virtual assembly system is described in which an optimal assembly algorithm is used to allow haptic interactions during virtual assembly operations. But the authors focus on the task of gripper selection, inter-part movement, and part assembly.
Abstract: Virtual assembly and disassembly simulations can be accomplished in intuitive and effective ways using haptic information in virtual environments (VEs). Potential problems in a given assembly scheme can be predicted by a user who may be able to suggest an alternative scheme in the VE. This paper describes an intelligent virtual assembly system in which an optimal assembly algorithm is used to allow haptic interactions during virtual assembly operations. This algorithm provides optimal paths for haptic guidance as well as an assembly sequence of the parts to be assembled. The performance of the given assembly schemes was simulated using a virtual assembly system. Experimental results showed that the haptic-path sequence-guidance (HSG) mode gave the best performance improvement in terms of accumulated assembly time (28.33%) and travel distance (15.05%) compared to the unguided mode, while the sequence-guidance (SG) mode alone increased performance by 15.33% for assembly time and 11.36% for travel distance. The experimental results were analyzed by the sub-tasks of gripper selection, inter-part movement, and part assembly. For the HSG mode, the greatest contributor to the time and distance reductions was the optimized haptic path, while for the SG mode, the reduced numbers of gripper exchanges and orientation change made the greatest contributions to reducing the assembly time and the travel distance. As a result, the optimized haptic path, as well as sequence guidance, enhanced the working performance of virtual assembly tasks.
TL;DR: In this article, a new design of microfluidic device for the separation of soft microorganisms using the deterministic lateral displacement principle is presented, which is based on creating new post shape that should address the challenges posed using the conventional circular post arrays.
Abstract: This paper presents a new design of microfluidic device for the separation of soft microorganisms using the deterministic lateral displacement principle. The novelty of the proposed design is based on creating new post shape that should address the challenges posed using the conventional circular post arrays. Based on experimental observations of trypanosome particles, circular posts have negative effects on the separation process of deformable and non-spherical cells. These effects reside in either shifting soft cells toward random streamlines further down the array or clogging the device. Airfoil and diamond post shapes have been proposed and compared against the circular posts. The flow around these posts has been simulated and analyzed numerically based on computational fluid dynamic (CFD). The results show that airfoil post shape has the potential to overcome complications when working with soft biological samples, namely the cells that are not rigid and not spherical. Microfluidic systems based on airfoil obstacles could easily be manufactured for clinical laboratory and biomedical applications providing a good promise in nano/micro-separation field.