Showing papers in "Robotics and Computer-integrated Manufacturing in 2017"

Workload-based multi-task scheduling in cloud manufacturing

Abstract: Cloud manufacturing is an emerging service-oriented business model that integrates distributed manufacturing resources, transforms them into manufacturing services, and manages the services centrally. Cloud manufacturing allows multiple users to request services at the same time by submitting their requirement tasks to a cloud manufacturing platform. The centralized management and operation of manufacturing services enable cloud manufacturing to deal with multiple manufacturing tasks in parallel. An important issue with cloud manufacturing is therefore how to optimally schedule multiple manufacturing tasks to achieve better performance of a cloud manufacturing system. Task workload provides an important basis for task scheduling in cloud manufacturing. Based on this idea, we present a cloud manufacturing multi-task scheduling model that incorporates task workload modelling and a number of other essential ingredients regarding services such as service efficiency coefficient and service quantity. Then we investigate the effects of different workload-based task scheduling methods on system performance such as total completion time and service utilization. Scenarios with or without time constraints are separately investigated in detail. Results from simulation experiments indicate that scheduling larger workload tasks with a higher priority can shorten the makespan and increase service utilization without decreasing task fulfilment quality when there is no time constraint. When time constraint is involved, the above strategy enables more tasks to be successfully fulfilled within the time constraint, and task fulfilment quality also does not deteriorate. Multi-task scheduling problems in cloud manufacturing are the focus.Task inherent attributes are considered.A model for attribute-based multi-task scheduling is built.With no time constraint, scheduling large tasks with a higher priority can effectively decrease the total completion time.With time constraint, the scheduling method can make more large tasks successfully executed.

SDMSim: A manufacturing service supply–demand matching simulator under cloud environment

Abstract: Nowadays, with the introduction and application of new information technologies in manufacturing, various advanced manufacturing modes and national strategies have been put forward and paid more and more attention, such as Industry 4.0, Industrial Internet, Cyber-Physical System or Cyber Manufacturing, Made in China 2025, Internet Plus Manufacturing, Cloud Manufacturing, etc. For these modes and strategies, how to realize the effective and intelligent supply–demand matching (SDM) of various manufacturing resources and capabilities (MR&C) in the form of service is one of the common issues and aims. In order to provide a uniformed research platform for related researchers both in academic and industry, the concept of manufacturing service SDM simulator (SDMSim) is proposed in this paper. A hypernetwork based architecture for the simulator is designed, as well as its seven key functions and subsystems, including manufacturing service management, manufacturing task management, manufacturing service SDM hypernetwork, manufacturing service SDM problem formulation and configuration, matching and scheduling algorithms/strategies selection and design, statistical analysis, and visualization. It illustrates that SDMSim has the potential to serve the users of manufacturing service provider, manufacturing service consumer, manufacturing service operator in the field of SoM, as well as the related researchers.

Development of a slender continuum robotic system for on-wing inspection/repair of gas turbine engines

Abstract: The maintenance works (e.g. inspection, repair) of aero-engines while still attached on the airframes requires a desirable approach since this can significantly shorten both the time and cost of such interventions as the aerospace industry commonly operates based on the generic concept "power by the hour". However, navigating and performing a multi-axis movement of an end-effector in a very constrained environment such as gas turbine engines is a challenging task. This paper reports on the development of a highly flexible slender (i.e. low diameter-to-length ratios) continuum robot of 25 degrees of freedom capable to uncoil from a drum to provide the feeding motion needed to navigate into crammed environments and then perform, with its last 6 DoF, complex trajectories with a camera equipped machining end-effector for allowing in-situ interventions at a low-pressure compressor of a gas turbine engine. This continuum robot is a compact system and presents a set of innovative mechatronics solutions such as: (i) twin commanding cables to minimise the number of actuators; (ii) twin compliant joints to enable large bending angles (ź90°) arranged on a tapered structure (start from 40mm to 13mm at its end); (iii) feeding motion provided by a rotating drum for coiling/uncoiling the continuum robot; (iv) machining end-effector equipped with vision system. To be able to achieve the in-situ maintenance tasks, a set of innovative control algorithms to enable the navigation and end-effector path generation have been developed and implemented. Finally, the continuum robot has been tested both for navigation and movement of the end-effector against a specified target within a gas turbine engine mock-up proving that: (i) max. deviations in navigation from the desired path (1000mm length with bends between 45° and 90°) are ź10mm; (ii) max. errors in positioning the end-effector against a target situated at the end of navigation path is 1mm. Thus, this paper presents a compact continuum robot that could be considered as a step forward in providing aero-engine manufacturers with a solution to perform complex tasks in an invasive manner. A novel slender continuum robot is introduced for in-situ repair/inspection of jet engines.A new kinematic model is introduced for the new tapered design.Modes of control for the continuum robot were developed, including tip-following, feeding-in/out, Machining commands.Navigation and inspection/machining tests in engine model were introduced.

Multisensory fusion based virtual tool wear sensing for ubiquitous manufacturing

Abstract: Pervasiveness of ubiquitous computing advances the manufacturing scheme into a ubiquitous manufacturing era which poses significant challenges on sensing technology and system reliability. To improve manufacturing system reliability, this paper presents a new virtual tool wear sensing technique based on multisensory data fusion and artificial intelligence model for tool condition monitoring. It infers the difficult-to-measure tool wear parameters (e.g. tool wear width) by fusing in-process multisensory data (e.g. force, vibration, etc.) with dimension reduction technique and support vector regression model. Different state-of-the-art dimension reduction techniques including kernel principal component analysis, locally linear embedding, isometric feature mapping, and minimum redundancy maximum relevant method have been investigated for feature fusion in a virtual sensing model, and the kernel principal component analysis performs best in terms of sensing accuracy. The effectiveness of the developed virtual tool wear sensing technique is experimentally validated in a set of machining tool run-to-failure tests on a computer numerical control milling machine. The results show that the estimated tool wear width through virtual sensing is comparable to that measured offline by a microscope instrument in terms of accuracy, moreover, in a more cost-effective manner. A multi-sensory fusion based virtual tool wear sensing model is developed.KPCA performs best among the dimension reduction techniques investigated.The virtual tool wear sensing model is validated using a machining tool life test.The performance of the model is comparable to the costly offline instrumentation.

Ubiquitous manufacturing system based on Cloud

Abstract: Modern manufacturing industry calls for a new generation of production system with better interoperability and new business models. As a novel information technology, Cloud provides new service models and business opportunities for manufacturing industry. In this research, recent Cloud manufacturing and Cloud robotics approaches are reviewed. Function block-based integration mechanisms are developed to integrate various types of manufacturing facilities. A Cloud-based manufacturing system is developed to support ubiquitous manufacturing, which provides a service pool maintaining physical facilities in terms of manufacturing services. The proposed framework and mechanisms are evaluated by both machining and robotics applications. In practice, it is possible to establish an integrated manufacturing environment across multiple levels with the support of manufacturing Cloud and function blocks. It provides a flexible architecture as well as ubiquitous and integrated methodologies for the Cloud manufacturing system. A ubiquitous manufacturing system based on Cloud manufacturing.Industrial robots utilized as implementation applications in the Ubiquitous manufacturing environment.Systematic analysis and guidelines for adpoting advanced manufacturing technologies.Multiple deployment models for private, community and public scenarios.Proposed system is implemented and evaluated in the near-real manufacturing environment.

Implementing speed and separation monitoring in collaborative robot workcells

Abstract: We provide an overview and guidance for the speed and separation monitoring methodology as presented in the International Organization of Standardization's technical specification 15066 on collaborative robot safety. Such functionality is provided by external, intelligent observer systems integrated into a robotic workcell. The SSM minimum protective distance function equation is discussed in detail, with consideration for the input values, implementation specifications, and performance expectations. We provide analytical analyses and test results of the current equation, discuss considerations for implementing SSM in human-occupied environments, and provide directions for technological advancements toward standardization. An overview of the speed and separation monitoring from ISO TS 15,066 is presented.Thoughts for integrators and end users are provided to illustrate factors that impact safety.Provisions for verification and validation of robot system functionality are given.Results from physical and simulation trials are presented to demonstrate functionality and integration considerations.Alternative interpretations and representations of system parameters are discussed.

A statistical analysis of the effects of Scrum and Kanban on software development projects

Abstract: Traditionally, software development processes have relied on the use of the "Waterfall" and "Vee" models. Later, Agile methodologies were used to handle the challenges of managing complex projects during the development phase. Agile methodologies are a group of incremental and iterative methods that are more effective, and have been used in project management. Kanban and Scrum are two powerful Agile project management approaches in software development. The objective of Scrum and Kanban is achieved by optimizing the development process by identifying the tasks, managing time more effectively, and setting-up teams. A review of the literature reveals that there is a lack of statistical evidence to conclude which methodology is more effective in dealing with the traditional project management factors of budget handling, risk control, quality of the project, available resources, having clear project scope, and schedule handling. This research statistically compares the effectiveness of the Scrum and Kanban methods in terms of their effects on the project management factors for software development projects. Numerical analysis is performed based on survey responses from those with experience in the Scrum and Kanban methods. Results suggest that both Scrum and Kanban lead to the development of successful projects, and that the Kanban method can be better than the Scrum method in terms of managing project schedule. Statistical analysis of Scrum vs. Kanban according to project management factors.Data obtained from surveys of people involved in software development.Analysis suggests that Kanban is slightly better than Scrum for the Schedule factor.

Posture optimization methodology of 6R industrial robots for machining using performance evaluation indexes

Abstract: For industrial robots, the relatively low posture-dependent stiffness deteriorates the absolute accuracy in the robotic machining process. Thus, it is reasonable to consider performing machining in the regions of the robot workspace where the kinematic, static and even dynamic performances are highest, thereby reducing machining errors and exhausting the advantages of the robot. Simultaneously, an optimum initial placement of the workpiece with respect to the robot can be obtained by optimizing the above performances of the robot. In this paper, a robot posture optimization methodology based on robotic performance indexes is presented. First, a deformation evaluation index is proposed to directly illustrate the deformation of the six-revolute (6R) industrial robot (IR) end-effector (EE) when a force is applied on it. Then, the kinematic performance map drawn according to the kinematic performance index is utilized to refine the regions of the robot workspace. Furthermore, main body stiffness index is proposed here to simplify the performance index of the robot stiffness, and its map is used to determine the position of the EE. Finally, the deformation map obtained according to the proposed deformation evaluation index is used to determine the orientation of the EE. Following these steps, the posture of the 6R robot with the best performance can be obtained, and the initial workpiece placement can be consequently determined. Experiments on a Comau Smart5 NJ 220-2.7 robot are conducted. The results demonstrate the feasibility and effectiveness of the present posture optimization methodology.

Modeling of manufacturing service supply-demand matching hypernetwork in service-oriented manufacturing systems

Abstract: The supply-demand matching and optimal-allocation of manufacturing resource and manufacturing capability, is always one of the key scientific issues to be addressed and the common objectives to be pursued for various advanced manufacturing systems (AMSs). Especially to the service-oriented manufacturing (SOM) systems (e.g., cloud manufacturing), which is a kind of typical and hot AMSs nowadays , it is extremely difficult to achieve the optimal allocation of large scales of different manufacturing services and the collaboration of manufacturing activities and business among massive manufacturing enterprises (no matter manufacturing service providers and consumers). Thus, under the current environment of social competition and collaboration, the most important challenge is how to integrate a variety of distributed manufacturing resources and capabilities in the form of manufacturing services efficiently and cost-effectively, as well as various demands or manufacturing tasks. In response to this challenge, the concept of supply-demand matching hypernetwork ( Matching_Net ) of manufacturing services in SOM system is put forward firstly in this paper. The proposed Matching_Net is constructed with manufacturing service network ( S_Net ), manufacturing task network ( T_Net ), and hyper-edges between those two networks which are revealing the matchable correlations between each service (supply) and each task (demand). Secondly, by comparing with the input or output information of manufacturing services and tasks from the functional view, the intelligent modeling of Matching_Net is illustrated and divided into those three constituent parts respectively. Finally, the simulation is carried out to validate and verify the proposed models and the modeling method. The model of hypernetwork (i.e., network of networks) is introduced into the supply-demand matching issues in service-oriented manufacturing systems.The concept and model of supply-demand matching hypernetwork ( Matching_Net ) of manufacturing services in SOM system are put forward considering both manufacturing services and manufacturing tasks.By comparing with the input or output information of manufacturing services and tasks, the intelligent modeling flow of Matching_Net is proposed and illustrated.The simulation is carried out to validate and verify the proposed models and the corresponding modeling method.

The role of wearable devices in meeting the needs of cloud manufacturing

Abstract: Cloud manufacturing is a service-oriented, customer-centric and demand-driven process with well-established industrial automation. Even though, it does not necessarily mean the absence of human beings. Due to products and their corresponding manufacturing processes becoming increasingly complex, operators' daily working lives are also becoming more difficult. Enhanced human-machine interaction is one of the core areas for the success of the next generation of manufacturing. However, the current research only focuses on the automation and flexibility features of cloud manufacturing, the interaction between human and machine and the value co-creation among operators is missing. Therefore, a new method is needed for operators to support their work, with the objective of reducing the time and cost of machine control and maintenance. This paper describes a practical demonstration that uses the technologies of the Internet of things (IoT), wearable technologies, augmented reality, and cloud storage to support operators' activities and communication in discrete factories. This case study exhibits the capabilities and user experience of smart glasses in a cloud manufacturing environment, and shows that smart glasses help users stay productive and engaged. Cloud manufacturing is a business strategy towards services, customers, and demands.Enhanced human-machine interaction is the success of the next generation of manufacturing.Wearable devices and other related technologies are used to support communication.

Efficiency evaluation of robots in machining applications using industrial performance measure

Abstract: The paper is devoted to the robotic based machining. The main focus is made on robot accuracy in milling operation and evaluation robot capacity to perform the task with desired precision. Particular attention is paid to the proper modeling of manipulator stiffness properties and the cutting force estimation. In contrast to other works, the robot performance is evaluated using the circularity norm that evaluates the contortion degree of the benchmark circle to be machined. The developed approach is applied to five industrial robots of KUKA family, which have been ranked for several machining tasks. The validity of the proposed technique was confirmed by experimental study dealing with robot-based machining of circular grooves for several workpiece samples and different locations.

Process planning for 8-axis robotized laser-based direct metal deposition system

Abstract: Laser-based direct metal deposition (LBDMD) is a promising additive manufacturing technology that is well suited for production of complex metal structures, low-volume manufacturing, and high-value component repair or modification. It finds broad application in the automotive, biomedical, and aerospace industries. The Research Center for Advanced Manufacturing (RCAM) at Southern Methodist University is developing a robot controlled LBDMD system that couples a 6-axis robot arm with an additional 2-axis tilt and rotatory positioning system. The system simplifies the process planning of multiple-directional deposition for complex parts and reduces production time. This paper describes the printing process specific to complex revolved parts. Taking advantage of the coupled 2-axis tilt and rotatory system, a hybrid slicing method is developed to map the overhanging structures of a revolved part to be at a planar base. Consequently, the traditional path planning strategies are applicable to generate the tool-path for the mapped structures. The method is successfully applied to build a propeller. An 8-axis robotized laser-based direct metal deposition system is developed.The process planning is developed to build the complex revolved parts.The hybrid slicing method maps the overhanging structures to a planar base.A propeller was printed to verify the performance of the process planning.

Ubiquitous manufacturing

Abstract: Ubiquitous manufacturing (UM) features a "design anywhere, make anywhere, sell anywhere, and at any time" paradigm that grants factories an unlimited production capacity and permanent manufacturing service availability. However, the research and applications of UM have been limited thus far to in-factory operations or logistics. For this reason, this study reviews the current practices of UM, discusses the challenges faced by researchers and practitioners, and determines potential opportunities for UM in the near future. Finally, we conclude that the success of UM depends on the quality of the manufacturing services deployed, and that UM is a realizable target for Industry 4.0. We reviewed the literature on ubiquitous manufacturing.We discussed the challenges faced by researchers and practitioners.We determined potential opportunities for UM in the near future.We concluded that ubiquitous manufacturing is a realizable target for Industry 4.0.

A particle swarm approach for optimizing a multi-stage closed loop supply chain for the solar cell industry

Abstract: In order to implement sustainable strategies in a supply chain, enterprises should provide highly favorable and effective solutions for reducing carbon dioxide emissions, which brings out the issues of designing and managing a closed-loop supply chain (CLSC). This paper studies an integrated CLSC network design problem with cost and environmental concerns in the solar energy industry from sustainability perspectives. A multi-objective closed-loop supply chain design (MCSCD) model has been proposed, in consideration of many practical characteristics including flow conservation at each production/recycling unit of forward/reverse logistics (FL/RL), capacity expansion, and recycled components. A deterministic multi-objective mixed integer linear programming (MILP) model capturing the tradeoffs between the total cost and total CO2 emissions was developed to address the multistage CSLC design problem. Subsequently, a multi-objective PSO (MOPSO) algorithm with crowding distance-based nondominated sorting approach is developed to search the near-optimal solution of the MCSCD model. The computational study shows that the proposed MOPSO algorithm is suitable and effective for solving large-scale complicated CLSC structure than the conventional branch-and-bound optimization approach. Analysis results show that an enterprise needs to apply an adequate recycling strategy or energy saving technology to achieve a better economic effectiveness if the carbon emission regulation is applied. Consequently, the Pareto optimal solution obtained from MOPSO algorithm may give the superior suggestions of CLSC design, such as factory location options, capacity expansion, technology selection, purchasing, and order fulfillment decisions in practice. An integrated CLSC problem by using PSO algorithm in the solar energy industry has been studied.A deterministic multi-objective mixed integer programming model has been established.The results Pareto CLSC solutions between CPLEX and MOPSO have been compared.MOPSO provides a rapid algorithm to search Pareto solution compare to CPLEX in large scale issues.

Fuzzy logic based tool condition monitoring for end-milling

Abstract: Monitoring the cutting condition of the tool in end-milling is a very complicated and prone to error task.Filtering and processing the data can be an extremely tedious process because of the relati...

An integrated approach of reverse engineering aided remanufacturing process for worn components

Abstract: The worn mechanical components/parts arrived in the remanufacturing system exhibit highly uncontrolled variabilities in failure conditions as well as structures and shape complexities. With the aid of reverse engineering (RE) technologies, a quick and accurate acquisition of the damaged areas of the worn part is attainable and thereby facilitates remanufacturing operations necessary to bring the parts back to like-new conditions. In this paper, a reverse engineering based approach is proposed to aid the remanufacturing processes of worn parts. The proposed approach integrates 3D surface data collection, nominal model reconstruction, fine registration, extraction of additive/subtractive repair, tool path generation and actual machining process, seeking to improve the reliability and efficiency of manual repair process. For nominal model reconstruction, a Prominent Cross-Section algorithm embedded with curvature constraint is proposed to automatically identify the boundary of the part's damaged area and thereby eliminate the defective point clouds from the reconstruction process. With the nominal reconstruction model and the 3D model of the worn part, a modified ICP algorithm integrating curvature and distance constraints is proposed to achieve a best-fit position of the two models by automatically identifying and eliminating the unreliable corresponding pairs through iterations. The proposed approach is demonstrated through remanufacturing of two different mechanical components and is approved to be efficient and effective.

Optimal trajectory generation algorithm for serial and parallel manipulators

Abstract: In this paper, an Optimal Trajectory Generation Algorithm (OTGA) is developed for generating minimum-time smooth motion trajectories for serial and parallel manipulators. OTGA is divided into two phases. The first phase encompasses derivation of minimum-time optimal trajectory using cubic spline due to its less vibration and overshoot characteristics. Although cubic splines are widely used in robotics, velocity and acceleration ripples in the first & last knots can worsen manipulator trajectory. The second phase includes changing cubic spline interpolation in the first and last knots of optimized trajectory with 7th order polynomial for having zero jerk at the beginning and end points of trajectory. Performing this modification eliminate undesired worsening in the trajectory and provide smoother start and stop of joint motions. Particle Swarm Optimization (PSO) is chosen as optimization algorithm because of its easy implementation and successful optimization performance. OTGA has been tested in simulation for PUMA robot and results are compared with algorithms proposed by earlier authors. In addition, a discrete-time PID control scheme for PUMA robot is designed for comparing energy consumption of OTGA with algorithms developed by previous authors. Comparison results illustrated that OTGA is the better trajectory generation algorithm than the others.

Workspace and dynamic performance evaluation of the parallel manipulators in a spray-painting equipment

Abstract: The paper deals with the workspace and dynamic performance evaluation of the PRR-PRR parallel manipulator in spray-painting equipment. Functional workspace of planar fully parallel robots is often limited because of interference among their mechanical components. The proposed 3-DOF planar parallel manipulator with two kinematic chains connecting the moving platform to the base can reduce interference while still maintaining 3 DOFs. Based on the kinematics, four working modes are analyzed and singularity is studied. The workspace is investigated and the inverse dynamics is formulated using the virtual work principle. The dynamic performance evaluation indices are designed on the basis of maximum and minimum magnitude of acceleration vector of the moving platform produced by a unit actuated force. The index not only can evaluate the accelerating performance of a manipulator, but also can reflect the isotropy of accelerating performance. Workspace and dynamic performances of the four working modes are compared and the optimal working mode for the painting of a large object with conical surface is determined. HighlightsFour working modes are analyzed and the optimal mode for painting a long rocket fairing with conical surface is determined.Dynamic performance indices are designed on the basis of acceleration vector of the moving platform produced by a unit actuated force.The index not only can evaluate the accelerating performance, but also can reflect the isotropy of accelerating performance.

Machine-vision-based identification of broken inserts in edge profile milling heads

Abstract: This paper presents a reliable machine vision system to automatically detect inserts and determine if they are broken. Unlike the machining operations studied in the literature, we are dealing with edge milling head tools for aggressive machining of thick plates (up to 12 centimetres) in a single pass. The studied cutting head tool is characterised by its relatively high number of inserts (up to 30) which makes the localisation of inserts a key aspect. The identification of broken inserts is critical for a proper tool monitoring system. In the method that we propose, we first localise the screws of the inserts and then we determine the expected position and orientation of the cutting edge by applying some geometrical operations. We compute the deviations from the expected cutting edge to the real edge of the inserts to determine if an insert is broken. We evaluated the proposed method on a new dataset that we acquired and made public. The obtained result (a harmonic mean of precision and recall 91.43%) shows that the machine vision system that we present is effective and suitable for the identification of broken inserts in machining head tools and ready to be installed in an on-line system. HighlightsA novel machine-vision-based method that detects broken inserts in milling heads.Unlike other methods, this approach does not require comparison to reference images.We demonstrate its effectiveness on a new data set of 144 images with 180 inserts.It is very efficient and it can be used without delaying any machining operations.

A non-retraction path planning approach for extrusion-based additive manufacturing

Abstract: Notwithstanding the widespread use and large number of advantages over traditional subtractive manufacturing techniques, the application of additive manufacturing technologies is currently limited by the undesirable fabricating efficiency, which has attracted attentions from a wide range of areas, such as fabrication method, material improvement, and algorithm optimization. As a critical step in the process planning of additive manufacturing, path planning plays a significant role in affecting the build time by means of determining the paths for the printing head's movement. So a novel path filling pattern for the deposition of extrusion–based additive manufacturing is developed in this paper, mainly to avoid the retraction during the deposition process, and hence the time moving along these retracting paths can be saved and the discontinuous deposition can be avoided as well. On the basis of analysis and discussion of the reason behind the occurrence of retraction in the deposition process, a path planning strategy called “go and back” is presented to avoid the retraction issue. The “go and back” strategy can be adopted to generate a continuous extruder path for simple areas with the start point being connected to the end point. So a sliced layer can be decomposed into several simple areas and the sub-paths for each area are generated based on the proposed strategy. All of these obtainable sub-paths can be connected into a continuous path with proper selection of the start point. By doing this, separated sub-paths are joined with each other to decrease the number of the startup and shutdown process for the extruder, which is beneficial for the enhancement of the deposition quality and the efficiency. Additionally, some methodologies are proposed to further optimize the generated non-retraction paths. At last, several cases are used to test and verify the developed methodology and the comparisons with conventional path filling patterns are conducted. The results show that the proposed approach can effectively reduce the retraction motions and is especially beneficial for the high efficient additive manufacturing without compromise on the part resistance.

Design and control of a 6-degree-of-freedom precision positioning system

Abstract: This paper presents the design and test of a 6-degree-of-freedom(DOF) precision positioning system, which is assembled by two different 3-DOF precision positioning stages each driven by three piezoelectric actuators (PEAs). Based on the precision PEAs and flexure hinge mechanisms, high precision motion is obtained. The design methodology and kinematic characteristics of the 6-DOF positioning system are investigated. According to an effective kinematic model, the transformation matrices are obtained, which is used to predict the relationship between the output displacement from the system arrangement and the amount of PEAs expansion. In addition, the static and dynamic characteristics of the 6-DOF system have been evaluated by finite element method (FEM) simulation and experiments. The design structure provides a high dynamic bandwidth with the first natural frequency of 586.3Hz. Decoupling control is proposed to solve the existing coupling motion of the 6-DOF system. Meanwhile, in order to compensate for the hysteresis of PEAs, the inverse Bouc-Wen model was applied as a feedforward hysteresis compensator in the feedforward/feedback hybrid control method. Finally, extensive experiments were performed to verify the tracking performance of the developed mechanism. Design of a 6-degree-of-freedom (DOF) precision positioning system.According to an effective kinematic model, the transformation matrices are obtained.The inverse Bouc-Wen model was applied as a feedforward hysteresis compensator.Extensive experiments were performed to verify the good tracking performances.

On the detection of defects on specular car body surfaces

Abstract: The automatic detection of small defects (of up to 0.2 mm in diameter) on car body surfaces following the painting process is currently one of the greatest issues facing quality control in the automotive industry. Although several systems have been developed during the last decade to provide a solution to this problem, these, to the best of our knowledge, have been focused solely on flat surfaces and have been unable to inspect other parts of the surfaces, namely style lines, edges and corners as well as deep concavities. This paper introduces a novel approach using deflectometry- and vision-based technologies in order to overcome this problem and ensure that the whole area is inspected. Moreover, since our approach, together with the system used, computes defects in less than 15 s, it satisfies cycle time production requirements (usually of around 30 s per car). Hence, a two-step algorithm is presented here: in the first step, a new pre-processing step (image fusion algorithm) is introduced to enhance the contrast between pixels with a low level of intensity (indicating the presence of defects) and those with a high level of intensity (indicating the absence of defects); for the second step, we present a novel post-processing step with an image background extraction approach based on a local directional blurring method and a modified image contrast enhancement, which enables detection of defects in the entire illuminated area. In addition, the post-processing step is processed several times using a multi-level structure, with computed image backgrounds of different resolution. In doing so, it is possible to detect larger defects, given that each level identifies defects of different sizes. Experimental results presented in this paper are obtained from the industrial automatic quality control system QEyeTunnel employed in the production line at the Mercedes-Benz factory in Vitoria, Spain. A complete analysis of the algorithm performance will be shown here, together with several tests proving the robustness and reliability of our proposal.

Dynamic performance analysis of the X4 high-speed pick-and-place parallel robot

Abstract: With the closed-loop structure, parallel manipulators possess some inherent advantages, such as high stiffness, enhanced dynamics, and compact structure. As a result, parallel manipulators gradually gain wide application. In the great variety of parallel manipulators, a kind of high-speed parallel robot, the limb of which is composed of active pendulum and passive parallelogram, gets popular and has realized industrial application firstly. Dynamic performance is the core of the high-speed parallel manipulator, which is usually illustrated through dynamic performance analysis with the aid of the index. Thus, developing reasonable dynamic performance indices is of great theoretical and practical significance for the high-speed parallel manipulator. In this paper, the Coefficient of Variation of joint-space Inertia (CVI) index is proposed to illustrate the acceleration consistency of each limb of the parallel manipulator. By taking the X4 high-speed pick-and-place parallel manipulator as object, the dynamic model and joint-space inertia matrix is established, and the dynamic performance analysis is carried out with the proposed CVI index and the existing Joint-Reflected Inertia (JRI) index. Simulation results illustrate changes of the dynamic performance of the X4 parallel manipulator, and reveal that the JRI index is well complemented with the CVI index. Finally, the workspace with good dynamic performance is discussed. This paper provides a new approach for dynamic analysis and optimal design of high-speed parallel manipulator. Limb Jacobian matrices of the X4 manipulator are given.Dynamic model and inertia matrix of the X4 manipulator are deduced.The CVI index is proposed to evaluate the dynamic performance.Dynamic performance of the X4 mahipulator is analyzed with indices.The workspace with good dynamic performance is disscussed.

Design, analysis and control of a winding hybrid-driven cable parallel manipulator

Abstract: This paper is related to the design, analysis and control of a winding hybrid-driven cable parallel manipulator (WHCPM). The WHCPM has the advantages of both cable parallel manipulator and hybrid-driven planar five-bar mechanism. Design of the WHCPM is explained, and the structure static analysis is carried out by using finite element method. Dynamics and payload capability of the WHCPM are studied. The WHCPM prototype is built for precision tracking experiments. To evaluate the manipulator design, the dynamic control compensation is performed on the basis of the conventional PID controller and the adaptive fuzzy sliding mode controller. The simulated and experimental results are reported and the tracking performance of the WHCPM is significantly improved by applying the proposed control technique in comparison with the performance when applying the conventional PID controller.

Dynamic analysis and driving force optimization of a 5-DOF parallel manipulator with redundant actuation

Abstract: Redundant actuation can improve the performance and ability of parallel manipulator. In order to deal with coordination and distribution of the driving force of the parallel manipulator with redundant actuation and to realize the control strategy based on dynamics, on the basis of the original 5UPS/PRPU parallel manipulator, it increases a drive for the middle PRPU passive constraint branch to make it a redundant actuation branch. It introduces configurations’ redundant types and compositions of 5UPS/PRPU parallel manipulator with redundant actuation, illustrates that the mechanism is redundant actuation from the perspective of degree of freedom and establishes a dynamic model based on Lagrangian method. On the basis of the weighted optimization principle of driving torque, it optimizes the driving torque of the parallel manipulator and calculates the driving force of the redundant driving chain with cutting force. It carries out the simulation by using ADAMS software and proves validity of dynamic model. Finally it detects the dynamic performance of the parallel manipulator by processing experiment of parallel manipulator with redundant actuation and its non-redundant counterpart.

Synchronized production and logistics via ubiquitous computing technology

Abstract: The integration of manufacturing and logistics has drawn widespread research attentions in recent years. This paper focuses on the Synchronized Production and Logistics (SPL), which is operational level integration. SPLźis defined as synchronizing the processing, moving and storing of raw material, WIP and finished product within one manufacturing unit by high level information sharing and joint scheduling to achieve synergic decision, execution and overall performance improvement. Through analysing the requirements and challenges in real life industry, the ubiquitous computing is adopted as an enabling technology and an Ubi-SPL (Synchronized Production and Logistics via Ubiquitous Technology) framework is proposed. This framework is consists of four layers, which creates a close decision-execution loop by linking the frontline real time data, user feedback and optimized decision together. A real life case study of applying Ubi-SPL solution in a chemical industry has been conducted. The implementation results show that the proposed Ubi-SPL solution can significantly improve the overall performance in both production and logistics service. This paper focuses on the Synchronized Production and Logistics.The ubiquitous computing is adopted as an enabling technology.Synchronized Production & Logistics via Ubiquitous Technics framework is proposed.A real life case study in a chemical industry has been conducted.

Kinematics analysis of a hybrid manipulator for computer controlled ultra-precision freeform polishing

Abstract: As one of the final processing steps of precision machining, polishing process is a very key decision for surface quality. This paper presents a novel hybrid manipulator for computer controlled ultra-precision (CCUP) freeform polishing. The hybrid manipulator is composed of a three degree-of-freedom (DOF) parallel module, a two DOF serial module and a turntable providing a redundant DOF. The parallel module gives the workpiece three translations without rotations. The serial module holds the polishing tool and gives it no translations on the polishing contact area due to its particular mechanical design. A detailed kinematics model is established for analyzing the kinematics of the parallel module and the serial module, respectively. For the parallel module, the inverse kinematics, the forward kinematics, the Jacobian matrix, the workspace and the dexterity distribution are analyzed systematically. Workspaces are also investigated for varying structural parameters. For the serial module, the inverse kinematics, the forward kinematics, the workspace and the precession motion analysis are carried out. An example of saddle surface finishing with this manipulator is given and the movement of actuators with respect to this shape is analyzed theoretically. These analysis results illustrate that the proposed hybrid manipulator is a very suitable machine structure for CCUP freeform polishing. A novel hybrid manipulator for ultra-precision freeform polishing is proposed.Precession polishing process is adopted to produce Gaussian-like tool influence function.A detailed kinematics model of the hybrid manipulator is presented.An example of saddle surface finishing with this manipulator is analyzed theoretically.

Evaluation of thermo-mechanical damage and fatigue life of solar cell solder interconnections

Abstract: The soldering process of interconnecting crystalline silicon solar cells to form photovoltaic (PV) module is a key manufacturing process. However, during the soldering process, stress is induced in the solar cell solder joints and remains in the joint as residual stress after soldering. Furthermore, during the module service life time, thermo-mechanical degradation of the solder joints occurs due to thermal cycling of the joints which induce stress, creep strain and strain energy. The resultant effect of damage on the solder joint is premature failure, hence shortened fatigue life. This study seeks to determine accumulated thermo-mechanical damage and fatigue life of solder interconnection in solar cell assembly under thermo-mechanical cycling conditions. In this investigation, finite element modelling (FEM) and simulations are carried out in order to determine nonlinear degradation of SnAgCu solder joints. The degradation of the solder material is simulated using Garofalo-Arrhenius creep model. A three dimensional (3D) geometric model is subjected to six accelerated thermal cycles (ATCs) utilising IEC 61215 standard for photovoltaic panels. The results demonstrate that induced stress, strain and strain energy impacts the solder joints during operations. Furthermore, the larger the accumulated creep strain and creep strain energy in the joints, the shorter the fatigue life. This indicates that creep strain and creep strain energy in the solder joints significantly impacts the thermo-mechanical reliability of the assembly joints. Regions of solder joint with critical stress, strain and strain energy values including their distribution are determined. Analysis of results demonstrates that creep energy density is a better parameter than creep strain in predicting interconnection fatigue life. The use of six ATCs yields significant data which enable better understanding of the response of the solder joints to the induced loads. Moreover, information obtained from this study can be used for improved design and better-quality fabrication of solder interconnections in solar cell assembly for enhanced thermo-mechanical reliability. Thermo-mechanical damage of solder joints in Si solar cell assembly evaluated.FEM and simulations carried out to determine nonlinear degradation of solder joints.Results show that induced stress and strain impacts solder joints reliability.Creep energy density better than creep strain in solder joint life prediction.Results useful for improved design of solder joints and better-quality fabrication.

Adaptive backstepping control for an n-degree of freedom robotic manipulator based on combined state augmentation

Abstract: The aim of this paper is to improve the tracking performance of a robotic manipulator by designing an adaptive controller and implementing it on the system. The proposed controller guarantees the system stability as well as good tracking performance in existence of nonlinearity and parameter uncertainties. The requirement to decrease the system response overshoot and steady state error as well as increasing speed of tracking for manipulators is essential to many manufacturers. To this mean, in this paper, the tracking error equations for an n-DOF manipulator are derived and the response characteristics are improved by augmenting a new state to the system equations. The stability of the closed-loop system is guaranteed based on the Lyapunov theory via backstepping control approach. The robotic manipulator model contains parametric uncertainties and many of the parameter values are unknown. To solve the problem, an adaption law is proposed via adaptive backstepping mechanism. Different experiments are carried out for a 2-DOF manipulator to show the effectiveness of the proposed approach and the results are compared with four of the recently revealed researches on control. Experimental results present the superiority of the state augmented adaptive backstepping in tracking the desired joint angles. Moreover, in order to present the industrial application of the proposed control method, it is simulated for a large industrial Scara manipulator. A state augmented adaptive backstepping controller is designed for robotic arms.Stability of the system is guaranteed based on the Lyapunov stability theorem.The proposed controller is implemented on a 2-DOF manipulator experimentally.Response characteristics are improved through state augmentation.Comparison results demonstrate the superiority of the proposed controller.

Multi-sensor measurement system for robotic drilling

Abstract: In this paper we present a multi-sensor measurement system for robotic drilling. The system enables a robot to measure its 6D pose with respect to the work piece and to establish a reference coordinate system for drilling. The robot approaches the drill point and performs an orthogonal alignment with the work piece. Although the measurement systems are readily capable of achieving high position accuracy and low deviation to perpendicularity, experiments show that inaccuracies in the test scenario and slippage on the work piece when exerting clamping force considerably impact the results. With the current robotic drilling system an average position deviation of 0.334mm and an average deviation to perpendicularity of 0.29 are achieved. A multi-sensor measurement system for robotic drilling is presented.The system enables a robot to measure its 6D pose with respect to the work piece.Out of measurements a reference coordinate system for drilling is established.At the drill point the robot performs an orthogonal alignment with the work piece.A deviation of less than 0.1mm in position and less than 0.2 is within reach.