Robotics and Computer-Integrated Manufacturing

In this paper, we present an intelligent control strategy for automated screw fastening. In automated assembly processes, there is a large number of dedicated stations for various types/sizes of screw fastening. Problems found in current processes include cross-threading, screw jamming, slippage and the need to apply precise torque. The intelligent controller developed supervises the integrated process of an electric driver mounted on a robotic positioning system to fasten screws. The new scheme controls continuously the motion and driving stages to avoid process caused failures, to achieve a desired precise torque and to detect bad parts at early stages of the assembly. Initial results are encouraging

Although an automated flexible production cell is an intriguing prospect for small to median enterprises (SMEs) in current global market conditions, the complexity of programming remains one of the major hurdles preventing automation using industrial robots for SMEs. This paper provides a comprehensive review of the recent research progresses on the programming methods for industrial robots, including online programming, offline programming (OLP), and programming using Augmented Reality (AR). With the development of more powerful 3D CAD/PLM software, computer vision, sensor technology, etc, new programming methods suitable for SMEs are expected to grow in years to come.

A wall-climbing robot intended for inspection in nuclear power plants has been developed in the context of a cooperative research project which is being carried out by Iberdrola and Nuclenor (Electric Companies), on the one side, and CEIT (Research Centre), on the other. In the first phase of the project, the tasks to be accomplished with the robotic system are of an inspection nature in boiling-water reactor plants. The robot, small in size and modular, is made up of pneumatic components exclusively. Vacuum suction cups are used for sticking the robot to walls to be climbed. The robot motion, made up of both elementary translations and rotations, is accomplished by means of pneumatic cylinders, which constitute the body of the mobile robot. A personal computer is used to command robot motion and a microprocessor controls the electronic valves of all pneumatic components. The paper presents the robotic system conceptual design and gives a detailed description of the mobile robot and its motion.

The layout design problem is a strategic issue and has a significant impact on the efficiency of a manufacturing system. Much of the existing layout design literature that uses a surrogate function for flow distance or for simplified objectives may be entrapped into local optimum; and subsequently lead to a poor layout design due to the multiple-attribute decision making (MADM) nature of a layout design decision. The present study explores the use of MADM approaches in solving a layout design problem. The proposed methodology is illustrated through a practical application from an IC packaging company. Two methods are proposed in solving the case study problem: Technique for order preference by similarity to ideal solution (TOPSIS) and fuzzy TOPSIS. Empirical results showed that the proposed methods are viable approaches in solving a layout design problem. TOPSIS is a viable approach for the case study problem and is suitable for precise value performance ratings. When the performance ratings are vague and imprecise, the fuzzy TOPSIS is a preferred solution method.

Information technology is the single most important factor in triggering innovation and increasing competitiveness in whole variety of other industries. The importance of Europe's competing results from an ever increasing share of the European market being supplied from Japan.Nearly all so-called “high-tech” products depend on semiconductors. Their increasing performance is of great strategic importance. The leading edge products in microelectronics are memory chips. Our technological capabilities will integrate memory and other functions with the processor on the same chip. IBM is devoting research and development efforts to finding a competitive European solution.Information technology prospects for the year 2000 impact applications, system structures, and changes in technology.European scientists and engineers have the capability to regain leadership in sectors important for the future.

A two-legged robot will have to generate its near-optimal gaits after ensuring maximum dynamic balance margin and minimum power consumption, while moving on the rough terrains containing some staircases and sloping surfaces. Moreover, the changes of joint torques should lie below a pre-specified small value to ensure its smooth walking. The balance of the robot and its power consumption are also dependent on hip trajectory and position of the masses on various limbs. Both neural network- and fuzzy logic-based gait planners have been developed for the same, the training of which are provided using a genetic algorithm off-line. Once optimized, the planners are found to generate optimal gaits of the two-legged robot successfully for the test cases.

Computers make accesible large amounts of information to the different levels of manufacturing organizations. However, this information can be of limited use if adequate decision making methodology is not applied. Very often, decisions made on the factory floor have a substantial impact on the performance of the entire manufacturing system. Process planning and scheduling are two activities that influence significantly these decisions. The common aspect of these activities is the assignment of various factory resources to the production tasks. The method presented in this paper seeks to use this commonality to integrate process planning and scheduling.

The operations of the semiconductor final test industry are complicated and characterized by multiple-resource constraints that require simultaneous considerations. One of the most challenging production-planning decisions in the industry concerns an efficient allocation of resources that results in high manufacturing performance. Firms in the industry are thus eager to discover resource-allocation knowledge from large manufacturing databases. This study develops a novel model via the extraction of fuzzy-business rules from databases for obtaining resource-allocation knowledge as well as allocating resources efficiently. The proposed model uses both a genetic algorithm to find the best priority sequence of customer orders for resource allocation and, in accordance with the priority sequence of orders, a fuzzy-inference model to allocate the resources and to determine the order-completion times. Experiments showed that the proposed model can significantly reduce task tardiness.

In reverse engineering, geometrical information of a product is obtained directly from a physical shape by a digitizing device. To fabricate the product, manufacturing information (usually tool-path) must be generated from a CAD model. The data digitized must be processed and in most cases, a surface model is constructed from them using some of the surface fitting technologies. However, these technologies are usually complicated and the process for constructing a surface patch from a massive digitizing data is time-consuming. To simplify the process for getting tool-path information, a simple algorithm is proposed in this paper. The algorithm is used to generate a 5-axis machining tool-path. Instead of implementing any complicated surface fitting techniques, a direct method is proposed for constructing three-dimensional (3D) triangular mesh from the digitizing data with the mesh points considered as the tool contact locations. Depending on the locations of the points digitized, a decimation procedure is applied such that some of the digitizing data will be filtered out. Then, the tool axis orientations which must be determined in 5-axis tool-path are calculated and the tool center locations are determined accordingly. A 3D biarc fitting technique is applied for all the tool center locations so that a complete 5-axis tool-path is obtained.

One of the problems that slows the development of off-line programming is the low static and dynamic positioning accuracy of robots. Robot calibration improves the positioning accuracy and can also be used as a diagnostic tool in robot production and maintenance. This work presents techniques for modeling and performing robot calibration processes with off-line programming using a 3D vision-based measurement system. The measurement system is portable, accurate and low cost, consisting of a single CCD camera mounted on the robot tool flange to measure the robot end-effector pose relative to a world coordinate system. Radial lens distortion is included in the photogrammetric model. Scale factors and image centers are obtained with innovative techniques, making use of a multiview approach. Results show that the achieved average accuracy using a common off-the-shelf CCD camera varies from 0.2 to 0.4 mm, at distances from 600 to 1000 mm from the target, respectively, with different camera orientations. Experimentation is performed on two industrial robots to test their position accuracy improvement using the calibration system proposed: an ABB IRB-2400 and a PUMA-500. The robots were calibrated at different regions and volumes within their workspace achieving accuracy from three to six times better when comparing errors before and after calibration, if measured locally. The proposed off-line robot calibration system is fast, accurate and easy to set up.

This paper presents a scheme for collaborative 3D design using product model at various levels of detail (LODs). Design features are selectively hidden at each level from certain participants, depending on their actual needs and individual accessibility in the collaboration. A tree data structure represents the feature hierarchy of CAD construction, the link between feature and LOD, and 2D mesh data for display control of each feature. An XML/XSLT-based approach is proposed to enable real-time visualization of different LOD models in distributed environment. A collaborative design system is implemented using multi-agent technologies, which focuses on function design of each agent, interactions among agents, the client–server structure, and generation of the LOD data using the XML/XSLT approach. A scenario of synchronous 3D mold assembly demonstrates that geometric categorization of product model provides an operational mechanism for assuring security of information sharing in engineering collaborations over the Internet. It also validates the effectiveness of the agent technologies for automating complex engineering activities.

Duplicate designs consume a significant amount of resources in most new product development. Search of similar parts for a given query part is the key to avoid this problem by facilitating design reuse. Most search algorithms convert the CAD model into a shape signature and compute the similarity between two models according to a measure function of their signatures. However, each algorithm defines the shape signature in a different way, and thus has its own limitations in discriminating 3D parts. This paper proposes a search scheme that successfully complements various shape signatures in similarity assessment of 3D mechanical components. It considers form-feature, topological, and geometric information in component comparison. Such an integrated approach can effectively solve the feature intersection problem, inherited in any feature-based approaches, and capture the user's intent more precisely in the search, which geometry-based methods fail to accomplish. We also develop a set of algorithms that performs the component comparison in a polynomial time. The proposed scheme is implemented in a product design environment consisting of commercial CAD and PDM systems. The result demonstrates the practicality of this work in automatic search of similar mechanical components for design reuse.

Six motion strategies for a Cartesian 4-degrees-of-freedom (4-DOF) biomass processing robot were developed. Each of the corresponding trajectories consists of more than 1300 three-dimensional coordinate points. The motion strategies were evaluated due to their efficiency to select the most promising one for being embedded into the control system of the robot. For evaluation, an algorithm was developed calculating different evaluation parameters such as total cycle time, covered distance and no-load time. The best strategy was able to perform the task within 23 h. The total covered distance within this time period amounts to 33 km. The efficiency of the motion strategy in terms of load- and no-load time phases was ε=57% and has to be enhanced during further research. By doubling maximum velocity to 60 m min−1 in longitudinal direction (x) and to 20 m min−1 in transverse direction (y) the total cycle time would be reduced additionally by maximum 20%.

In the past few years, extending usage of robotic systems has increased the importance of robot reliability and quality. To improve the robot reliability and quality by applying standard approaches such as Failure Mode and Effect Analysis (FMEA) and Quality Function Deployment (QFD) during the design of robot is necessary. FMEA is a qualitative method which determines the critical failure modes in robot design. In this method Risk Priority Number is used to sort failures with respect to critical situation. Two examples of mechanical robots are analyzed by using this method and critical failure modes are determined for each robot. Corrective actions are proposed for critical items to modify robots reliability and reduce their risks. Finally by using QFD, quality of these robots is improved according to the customers’ requirements. In this method by making four matrixes, optimum values for all technical parameters are determined and the final product has the desired quality.

In this paper, a particular emphasis is put on the workspace mapping with deficient-DOF space between the PUMA 560 robot and its exoskeleton-arm master-type manipulator, which is proved to be the key step for different structure-based master–slave manipulation. The deficient-DOF space of PUMA 560, made up with the singularity and joint limitation, affects the maneuverability and stability of the master–slave manipulation system. In this work, the deficient-DOF space in the mapped workspace with master–slave control is investigated as a main factor of the workspace mapping. Meanwhile, the orthogonal experiment design method is introduced and two rounds of orthogonal experiments are carried out for this mapping problem, which is simultaneously characterized by many other variables At last the simulation and experiment results demonstrate that the scheme of the mapping is feasible and the orthogonal experiment design method is effective. It is a novel application and exploration of the orthogonal experiment design method in the mechanical or robot optimal design.

Conceptual process planning (CPP) is an important technique for assessing the manufacturability and estimating the cost of conceptual design in the early product design stage. This paper presents an approach to develop a quality/cost-based conceptual process planning (QCCPP). This approach aims to determine key process resources with estimation of manufacturing cost, taking into account the risk cost associated to the process plan. It can serve as a useful methodology to support the decision making during the initial planning stage of the product development cycle. Quality function deployment (QFD) method is used to select the process alternatives by incorporating a capability function for process elements called a composite process capability index (CCP). The quality characteristics and the process elements in QFD method have been taken as input to complete process failure mode and effects analysis (FMEA) table. To estimate manufacturing cost, the proposed approach deploys activity-based costing (ABC) method. Then, an extended technique of classical FMEA method is employed to estimate the cost of risks associated to the studied process plan, this technique is called cost-based FMEA. For each resource combination, the output data is gathered in a selection table that helps for detailed process planning in order to improve product quality/cost ratio. A case study is presented to illustrate this approach.

For the control of abrasive flow machining (AFM) process, it is important to understand the mechanics of generation of its surface profile. This paper describes the analysis and simulation of profile of finished surface and material removal by the interaction of abrasive grains with workpiece. The abrasive grains are randomly distributed in media depending upon their percentage concentration and mesh size. The results predicted from simulation and obtained from response surface analysis (or experiments) are compared to explain the relative importance of AFM parameters. The generated surface profile and material removal are the function of number of cycles, percentage concentration and mesh size of abrasives, reduction ratio and extrusion pressure applied.

Manufacturing Systems are inherently complex and interdisciplinary, and are normally analyzed in a piecewise fashion using experimental techniques which provide relatively little physical insight or theoritical methods brrowed from other disciplines (e.g., structural mechanics, control theory, etc.). For these reasons Manufacturing Engineering is often considered an unscientific and intuitive subject. With the increasing demand for manufacturing systems to operate at higher production rates without human intervention to reduce manufacturing costs, it is becoming increasingly important to develop scientifically based, general, and efficient analysis tools specifically tailored to the complex interdisciplinary problems encountered in Manufacturing Engineering. In addition to having direct practical benefits, such tools would stimulate academic interest in this field and help alleviate current academic and industrial personnel shortages in the manufacturing area.This paper describes one such analysis tool, the Dynamic Data System (D.D.S.) methodology, which has been developed at the University of Wisconsin. The D.D.S. methodology combines time series and systems analysis concepts in a computer-based modeling strategy for obtaining a physically meaningfully model of a system directly from input and output data in the form of stochastic difference/differential equations. The methodology can be applied to forecasting, control, system identification, characterization, signature analysis, and design. The basic features of the methodology, representative applications to the on-line detection and suppression of chatter in turning and the active compensation for roundness errors in boring, and areas for future development are discussed.

Sensing, modeling, control and manufacturing uncertainties make it generally impossible to guarantee the success of high-precision robot tasks. The paper analyzes the relationships among these uncertainty parameters and derives constraints which govern the success of a new form of control strategy: the constrained accelerated-feedback (CAF) control strategy. The CAF control strategy is suitable for high-level control accommodating the use of multiple sensing modalities, and aims at guaranteeing the success of robot motion in spite of uncertainties.

This paper presents the application of the acceleration sensor in the enhancement of the performance of high-precision motion tracking linear actuators which are based on permanent magnet linear motors (PMLM). A feedforward–feedback control structure is developed which harness effectively the acceleration measurements made available. It utilises a linear full-state feedback controller and an iterative learning feedforward controller (ILC). Experimental results show the acceleration feedback can improve the tracking performance and learning convergence of the control system.

Acceleration profile generation for jerk limitation is a major issue in automated industrial applications like computer numerical control (CNC) machinery and robotics. The automation machinery dynamics should be kept as smooth as possible with suitable controllers where trajectory precision ensures quality while smoothness decreases machinery stress. During the operation of commercially available CNC and robotics controllers, small discontinuities on the dynamics are generated due to the controller position profiler which is generally based on a trapezoidal velocity profile. These discontinuities can produce undesirable high-frequency harmonics on the position reference which consequentially can excite the natural frequencies of the mechanical structure and servomotors. Previous works have developed jerk limited trajectories with higher degree polynomial-based profiles, but lack one or both of computer efficiency for on-line operation and low-cost hardware implementation. The present work shows a low cost, computationally efficient, on-line hardware implementation of a high-degree polynomial-based profile generator with limited jerk dynamics for CNC machines and robotics applications to improve the machining process. The novelty of the paper is the development of a multiplier-free recursive algorithm for computationally efficient polynomial evaluation in profile generation and a low-cost implementation of the digital structure in field programmable gate array (FPGA). Two experimental setups were prepared in order to test the polynomial profile generator: the first one with the servomotor at no load and the second one for the servomotor driving a CNC milling machine axis. From experimental results it is shown that higher degree polynomial profiles, compared to the standard trapezoidal speed profile improve the system dynamics by reducing peak jerk in more than one order of magnitude while precision is maintained the same and on-line operation is guaranteed.

One of the important issues about product assemblability (PA) is to design a product configuration that will facilitate assembly operations. The product configuration in this paper means the arrangement of components within a product. When a product is assembled, every component has to be handled by an assembly agent from the feeding position to the composing position. During this action, the product configuration plays a critical role in the planning and execution of the handling task of each component. The influence of the product configuration on the accessible range of a component can be investigated by considering the accessibility of the component. With an assembly oriented product configuration a product can achieve maximal assemblability in terms of the accessibility of each component.

With reference to a real industrial application of process control, some considerations are discussed concerning the accuracy of methods for auto-tuning of proportional, integral and derivative factor (PID). In particular, a theoretical–experimental approach is described, that allows to evaluate the adequateness of new methods for auto-tuning of PID, able to significantly reduce the time duration for auto-tuning with respect to traditional ones. This result has been achieved by using suitable techniques of experimental data processing, based on neural-networks algorithms, set for this specific application. The effect on described methodology of environmental and operating disturbances is also described.

In automomous navigation, it is essential to obtain a three-dimensional (3D) description of the static environment in which the vehicle is traveling. For rotorcraft conducting low-altitude flight, this description is particularly useful for obstacle detection and avoidance. In this paper, we address the problem of 3D position estimation for static objects from a monocular sequence of images captured from a low-altitude flying helicopter. Since the environment is static, it is well known that the optical flow in the image will produce a radiating pattern from the focus of expansion. We propose a motion analysis system that utilizes the epipolar constraint to accurately estimate 3D positions of scene objects in a real world image sequence taken from a low-altitude flying helicopter. Results show that this approach gives good estimates of object positions near the rotorcraft's intended flightpath.

This paper discusses the concepts associated with a new methodology, design for adaptation (DFAD), under development for achieving advanced sustainable designs. The DFAD methodology concept is based on the hypothesis that product life ends because a product is unable to adapt to change. A product may be retired for myriad reasons including that it is broken, out of style, or has become inefficient due to technology obsolescence. In these cases, the product was not able to adapt to change—it was unable to self-heal, it could not modify or reconfigure to meet changing fashion needs, or it could not be upgraded, for physical or economic reasons, to utilize new technology. To address these and similar issues, we are developing the DFAD methodology. DFAD is based on classical control theory and products are conceptualized and modeled as dynamic systems with feedback control strategies to respond, or adapt, effectively to changes in product performance criteria. The DFAD concept takes into account that changing performance requirements may be based on physical, cultural, environmental, and/or economic considerations, among others.

The ability to improve yield is an important competitiveness determinant for thin-film transistor-liquid crystal displays (TFT-LCD) factories. Until now, few studies were proposed to address the related issues for process analysis in TFT-LCD industry. Therefore, the information (e.g. the domain knowledge or the parameter effect) or the improvement chance hidden from process analysis will be frequently omitted. That is, the yield or yield loss model construction, the critical manufacturing processes (or layers) and the clustering effect based on the abnormal position (or defect) on TFT-LCD glasses will became the important issues to be addressed in TFT-LCD industry. In this study, we proposed an integrated procedure incorporating the data mining techniques, e.g. artificial neural networks (ANNs) and stepwise regression techniques, to achieve the construction of yield loss model, the effect analysis of manufacturing process and the clustering analysis of abnormal position (or it can be viewed as defect) for TFT-LCD products. Besides, an illustrative case owing to TFT-LCD manufacturer at Tainan Science Park in Taiwan will be applied to verifying the rationality and feasibility of our proposed procedure.

Forming processes are manufacturing processes based on deformation of raw material applying pressure in one or several stages until getting the final product. This process depends on many factors, e.g. process parameters, material properties or lubrication, leading to possible defective parts. Correct forming of parts is very important as any defective part may result in big economical losses, e.g. the return of a complete set of parts or the loss of some clients. Thus, in our European Craft Pro2Control project, leading German, French, Italian and Spanish companies, universities and forming industries are defining and implementing a zero-defect forming control system, minimizing costs and maximizing the throughput of parts.

This paper discusses the principles for the acquisition of a three-dimensional (3-D) computational model of the treatment area of a burn victim for a vision-servo-guided robot which ablates the victim's burned skin tissue by delivering a high-energy laser light to the burned tissue. The medical robotics assistant system consists of: a robot whose end effector is equipped with a laser head, whence the laser beam emanates, and a vision system which is used to acquire the 3-D coordinates of some points on the body surface; 3-D surface modeling routines for generating the surface model of the treatment area; and control and interface hardware and software for control and integration of all the system components. Discussion of the vision and surface modeling component of the medical robotics assistant system is the focus of this paper. The robot-assisted treatment process has two phases: an initial survey phase during which a model of the treatment area on the skin is built and used to plan an appropriate trajectory for the robot in the subsequent phase—the treatment phase, during which the laser surgery is performed. During the survey phase, the vision system employs a camera to acquire points on the surface of the patient's body by using the camera to capture the contour traced by a plane of light generated by a low power laser, distinct from the treatment laser. The camera's image is then processed. Selected points on the camera's two-dimensional image frame are used as input to a process that generates 3-D body surface points as the intersection point of the plane of light and the line of sight between the camera's image point and the body surface point. The acquired body surface points are then used to generate a computational model of the treatment area using the non-uniform rational B-splines (NURBS) surface modeling technique. The constructed NURBS surface model is used to generate a treatment plan for the execution of the treatment phase. The robot plan for treatment is discussed in another paper. The prototype of the entire burn treatment system is at an advanced stage of development and tests of the engineering principles on inanimate objects, discussed herein, are being conducted.

We propose several examples of robotics applications where interactions with the environment play an important role, and where no modelization of the robot or of the world is needed. We argue that, in general, this helps to simplify the complexity of the control system, and illustrate this claim through several examples. We propose different neural networks which allow clustering of scattered objects by several robots, learning of obstacle avoidance and learning of target retrieval.

The overall strategic goal of the European Community R&D programme ESPRIT is to provide the European IT industry with the technology base it needs to become and stay competitive. CIM is an important part of this programme and has an additional objective to accelerate the modernization process in a wide range of manufacturing and engineering industries. In this paper an overview is presented of strategies and ongoing work. Some results are highlighted and relations to non-ESPRIT initiatives are discussed.

In this paper, based on the conventional Newton–Euler approach, a simplification method is proposed to derive the dynamic formulation of a planar 3-DOF parallel manipulator with actuation redundancy. Closed-form solutions are developed for the inverse kinematics. Based on the kinematics, the Newton–Euler approach in simplification form is used to derive the inverse dynamic model of the redundant parallel manipulator. Then, the driving force optimization is performed by minimizing an objective function which is the square of the sum of four driving forces. The dynamic simulations are done for the parallel manipulator with both the redundant and non-redundant actuations. The result shows that the dynamic characteristics of the manipulator in the redundant case are better than that in the non-redundancy. The redundantly actuated parallel manipulator was incorporated into a 4-DOF hybrid machine tool which includes a feed worktable.

The aim of the research presented in this paper was to propose a simple and cheap system, able to produce a macroscopic (centimetric) travel with a very high (nano-metric) resolution. The solution principle described yields a theoretically infinite travel range based on the accumulation of successive steps. The travel range of the prototype realised is equal to , the size of the steps being about . The actuation is based on the stick–slip effect: during the first stage of a step, the legs of the actuator slowly translate the carried structure; in the second stage the legs are moved back in their initial position very quickly, so that, thanks to their inertia, the structure stays at the same place. Each leg of the system, glued on a main frame, consists in a piezoelectric device working in shear mode, ended by a ruby hemisphere. The structure itself is in steel to get a sufficiently high inertia. An originality of the proposed translator is that the guiding elements of the structure (guiding grooves) are also used to transmit the motion. The friction force between the legs and the grooves can be tuned thanks to a magnet placed in the main frame, allowing to adjust the normal load on the legs. The paper presents the different functional elements of the translator and its electronic command system, and explains its functioning. The influence of several parameters (supported load, friction, resistive axial load) on the step size and thus on both the resolution, hence the speed of the system is then studied. Finally, the power losses are identified and estimated.

This paper presents the design issues and hardware implementation for robot-operated automatic modular and adaptable fixtures. Modular fixtures are workholding devices made from stackable self-contained modular elements. Adaptable fixtures provide surface contact with the workpiece and therefore can adapt to the workpiece geometry. These fixtures are shown to have several advantages over conventional fixtures. Issues in modularity and adaptability for workpiece fixturing are discussed for the purpose of evaluating automatic modular fixtures in flexible manufacturing systems. The basic design requirements for robot-operated modular and adaptable fixturing systems are developed and classified into mechanical and operational. Automatic assembly issues such as the use of special mating surfaces, compact actuators for active modules, as well as the importance of communications between the robot manipulator and the modular fixture are discussed.Hardware design and implementation of a shape memory alloy actuated locking module and a discrete conformable surface module are presented. Performance characteristics such as free-play, stiffness and time response were evaluated experimentally for the locking module. Several workpiece geometries are tested on the comformable surface module.

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.

Automated test systems (ATS) are application-specific systems that help in enhancing reliability and productivity of testing activities in different stages of product development cycle and manufacturing. Different tests are necessary to anticipate and validate a product and its sub-systems performances along the development cycle. Moreover, in the production phase, quality control systems that perform up to 100% inspection may be present and the integration of test results with company's management systems may be required. In this paper, the design of ATS is analyzed under the light of design methodologies, which can basically be understood as procedures stating stages and intermediary results to discipline the development process of technical systems. Usually, design methodologies are presented as a set of prescribed actions and recommendations, kept with some degree of generality to allow their compatibility with a wide range of industrial products, based on different technology branches. In this paper, an adaptation of Pahl and Beitz's approach allowed the derivation of a reference model to ATS development. Proposed stages are explained considering ATS typical division, i.e.: physical system, hardware and software. The adapted methodology, in which prescriptions are made with an intermediary degree and directed to one particular kind of system, can make easier the design of a highly context-dependant kind of system, helping the design team to consider important aspects in decisions taken along the development process and keeping these decisions linked to the requirements defined in early stages. Through the use of the proposed methodology, shorter development cycles are expected, since less design loops tend occur in a higher-systematization environment.

The application of robotics to the assembly of large aero-structures has been limited by the large size and inherent compliance of the components involved. The compliance of the components is significant and simple ‘pick and place’ approaches cannot be used due to the inherent dimensional variability between mating parts. The research described in this paper aims to solve this problem by using a non-contact sensing system to measure part deformation and misalignment in real time. The acquired data can then be processed through a mathematical algorithm to calculate the relative component positions required for optimal assembly. The data can also be used to check gross distortion of components and to reject those outside the specification limits. Existing part-to-part holes were used to provide alignment for individual components within the structure. A series of experiments were performed to investigate the feasibility of the method. Results are presented along with a discussion of the problems that may be encountered during robotic assembly. The experimental results show that robots when combined with non-contact metrology can be used for the assembly of compliant aero-structure components within required tolerance limits.

In this paper, a Cartesian-space control scheme is developed to control the motion of kinematically redundant manipulators having 7 degrees of freedom (DOF) or more. The control scheme is composed of proportional-derivative (PD) controllers whose gains are adjusted by an adaptation law driven by the errors between the desired and actual Cartesian trajectories. The derivation of the adaptation law is based on the concept of model reference adapative control (MRAC) and Lyapunov direct method under the assumption that the manipulator end-effector motion is slow as compared to the controller adaptation rate. The developed control scheme is computationally efficient because its implementation does not require the computation of the manipulator dynamics and therefore does not need an extremely fast computer. Results of computer simulation performed to evaluate the performance of the developed control scheme on a 7 DOF manipulator tracking several test paths during sudden changes in payload are presented and discussed.

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.

This paper explores a strategy of model-referenced trajectory tracking for a rigid-link cylindrical robot by employing an Adaptive Computed Torque Control Scheme (ACTCS) in conjunction with a Linear Optimal Controller (LOC). The adaptive control scheme is based on a version of Narendra's Direct Model-referenced Adaptive Control algorithm and includes adaptive sampling. The results presented here represents an extention of previous work whereby the formulation of the ACTCS and its experimental evaluation for a 3-DOF cylindrical robot was developed. This paper investigates the addition of a linear optimal tracking controller in the scheme. Experimental results show that the adaptive controller brings the end-effector of the robot manipulator onto the model-referenced differential manifold swiftly and robustly.

This paper considers the trajectory tracking problem for uncertain robot manipulators and proposes two adaptive controllers as solutions to this problem. The first controller is derived under the assumption that the manipulator state is measurable, while the second strategy is developed for those applications in which only position measurements are available. The adaptive schemes are very general and computationally efficient since they do not require knowledge of either the mathematical model or the parameter values of the manipulator dynamics, and are implemented without calculation of the robot inverse dynamics or inverse kinematic transformation. It is shown that the control strategies ensure uniform boundedness of all signals in the presence of bounded disturbances, and that the ultimate size of the tracking errors can be made arbitrarily small. Experimental results are presented for a PUMA 560 manipulator and demonstrate that accurate and robust trajectory tracking can be achieved by using the proposed controllers.

Data compression will play an increasingly important role in the storage and transmission of image data within the NASA science programs as the Earth Observing System comes into operation. It is important that the science data be preserved at the fidelity the instrument and satellite communication systems were designed to produce. Lossless compression must therefore be applied, at least to archive the processed instrument data. In this paper, we present an analysis of the performance of lossless compression techniques and develop an adaptive approach that applies image remapping, feature-based image segmentation to determine regions of similar entropy, as well as high-order arithmetic coding, to obtain significant improvements over the use of conventional compression techniques alone. Image remapping is used to transform the original image into a lower entropy state. Several techniques were tested on satellite images including differential pulse code modulation, bi-linear interpolation, and block-based linear predictive coding. The results of these experiments are discussed, and trade-offs between computation requirements and entropy reductions are used to identify the optimum approach for a variety of satellite images. Further entropy reduction can be achieved by segmenting the image based on local entropy properties and then applying a coding technique that maximizes compression for the region. Experimental results are presented showing the effect of different coding techniques for regions of different entropy. A rule-base is developed through which the technique giving the best compression is selected. The paper concludes that maximum compression can be achieved cost effectively and at acceptable performance rates with a combination of techniques that are selected based on image contextual information.

A direct metal rapid tool making process, hybrid-layered manufacturing (HLM), was developed for building metallic dies and molds. This unique methodology has a numerical controlled system that integrates the TransPulse Synergic Metal Inert Gas (MIG)/Metal Active Gas (MAG) welding process for near-net layer deposition and Computer Numerical Control (CNC) milling process for net shaping. A customized software program was made to calculate the required adaptive slice thickness for the deposition of the filler metal with welding process as successive layers from the lowest to the topmost layer direction and to generate the required NC codes for machining from the top to the bottom layer direction of the deposited metallic layers for attaining the required contour profile shape. To implement this proposed process, a low-cost three-axis manipulator was fabricated with stepper motor divers in open-loop control and integrated with the weld machine. Adequate isolation to protect the motion control electronics from welding spike was incorporated. Synchronization of this two-step processing of each layer, yielding near-net deposition with welding process and near-net shaping with CNC milling operation offers a new accelerator way of building metal tools and dies.

Adaptive Control (AC) of machine tools requires many kinds of measured input data. The more information about the complex metal cutting process that can be obtained, the better the process can be controlled.The paper describes an Adaptive Control Optimization (ACO) system for turning operations. The system continuously chooses Optimal Cutting Data (OCD), taking into account both economical criteria and technical limitations.The system operates at three different levels: •• Advanced Process Monitoring•• Adaptive Control Constraint (ACC)•• Adaptive Control Optimization (ACO).Two commercial monitoring systems perform process monitoring. In addition, five independent measurement systems have been developed.A dedicated vision system has been installed in the lathe to measure the tool flank wear between cuts. The flank wear data are utilized to predict the tool life. Based upon these predictions economical optimum cutting data can be calculated at the ACO level.To obtain in-process real-time control of the metal cutting process the cutting forces are measured during machining. The forces are measured with conventional piezoelectric force transducers which are located between the turret housing and the cross-slide. The measured force signals are processed by a dedicated microcontroller at the ACC level and cutting data adjustments are fed back to the machine control.A vibration measurement system, which either can be connected to an accelerometer or use the dynamic force signal from the piezoelectric force transducer, is part of a vibration control module at the ACC level. An ultra-fast signal processor performs the signal analysis.The remaining two measurement systems—a high frequency tool signal analysis system and a power spectra analysis system—are mentioned in the paper but not further discussed.Finally, the paper deals with how the strategies at the three different levels will be combined, in order to form an AC system. The monitoring tasks will always reside in the background and be activated if any failure occurs. The ACO subsystem will act as a path-finder and suggest cutting data. The active control tasks will, however, be carried out at the ACC level.

The exploration of dynamic stability in bidedal machines requires a great deal of knowledge about the science of balancing, both equilibrium and motion. Recent work in robotic legged locomotion has concentrated on systems that require three or more legs on the ground at any given time. This research focuses on adaptive control strategies for a bipedal machine that will allow balance and controlled motion with one leg and, if not walking, on two legs on the ground at any given time. Our approach is to optimize a set of balance and motion profiles through extensive simulation and to validate the profiles on an experimental testbed. Once validated as capable of providing dynamic stability, the adaptive control model uses these profiles as nominal control. The sensory input is then used to modify the nominal control to allow precise control at each sampling period. Simply stated, our control model continuously measures the rate of fall of the biped, and adjusts torques at the knees and hips to constrain this fall to dynamic balance and controlled motion. As should be suspected at this time, our control model is sensor driven and does not require a solution to the Lagrangian equations of motion. The result is a faster, less complex, adaptive control process. Our experimental bipedal testbed currently, and repeatedly, exhibits 25 + stable steps on a flat but slightly varied terrain. Current technology could not provide the kind of actuation and measurements necessary to implement our control model; therefore, our team has developed new low pressure, servoed hydraulic systems and sensory devices. Our most recent experimentation has used parallel computing methods and devices in the C + + programming language on a transputer (parallel computer) based Cogent XTM parallel computing workstation.

In this paper the control problem for robot manipulators with flexible joints is considered. A reduced-order flexible joint model is constructed based on a singular perturbation formulation of the manipulator equations of motion. The concept of an integral manifold is utilized to construct the dynamics of a slow subsystem. A fast subsystem is constructed to represent the fast dynamics of the elastic forces at the joints. A composite control scheme is developed based on on-line identification of the manipulator parameters which takes into account the effect of certain unmodeled dynamics and parameter variations. Stability analysis of the resulting closed-loop full-order system is presented. Simulation results for a single link flexible joint manipulator are given to illustrate the applicability of the proposed algorithm.

In this paper, a neuro-adaptive motion control with velocity observer is developed and validated in real-time experiment using a 6 DOF PUMA 560 robot. The controller is constructed for the operational space formulation, such that dynamic terms and the generalized force descriptions in this algorithm are expressed in the task space. The proposed strategy assumes no prior knowledge of the robot dynamics, and is formulated without assuming the availability of joint velocity feedback. As such, the controller takes only position feedback. This is an important feature as industrial robots are often fitted only with joint displacement sensors, not joint rate sensors. Stability analysis of the algorithm is analysed and presented in the paper. Real-time experiments on a 6 degrees of freedom (DOF) PUMA 560 manipulator were carried out to evaluate the effectiveness of the proposed NN adaptive control strategy with velocity observer and to compare the performance with the conventional inverse-dynamics control and a similar NN adaptive strategy using filtered velocity feedback, obtained through the backward difference of the displacement feedback. It should be noted that the experimental platform, PUMA 560, provides only joint displacement feedback through its joint mounted encoders. The results show a comparable results between the proposed strategy and the inverse-dynamics control law, without the need to perform dynamics identification procedures.

Adaptive system often refers to the adaptive control system. In this paper, we discuss the adaptive system concept from an architectural perspective of the system. We use the robotic system as an example to illustrate the adaptive system concept, because the robotic system is a generic system underlying many manufacturing systems. Specifically, the paper presents our work on the development of a general architecture of the adaptive robotic system for manufacturing applications. The contribution of this paper includes: (i) elaboration of the concept of adaptive system and classification of means to make the system adaptive and (ii) formulation of a general architecture of the adaptive robotic system based on the criterion that the more system variants out of the architecture implies the more generality of the architecture. Throughout this paper, we use an industrial robotic system for illustration.

Last decade witnessed the growth of globally decentralized product development and manufacture. The complexity of products created in such a distributed environment often requires close collaborations among a number of design and production partners. In this paper, an agent-based system for coordinated product development and manufacture is presented. The system consists of two categories of agents. The first category consists solely of a managing agent (MA) and the second consists of many functional agents such as the manufacturability evaluation agent, resource agent, process-planning agent, scheduling agent, etc. Each agent represents a domain expert and it can be installed in an individual computer. All the agents could be dispersed in geographically different regions and communicate with one another through the Internet. With each functional agent having specific functionality, the MA is the center of the intelligent system. It assists the work of other agents and enables them to collaborate closely with one another. With such a system in place, a product life cycle can be optimized from product design to final manufacturing as all the procedures are considered comprehensively and integrally, and each procedure is performed in a way as to ease and expedite the work of other agents. An agent language, which includes many specifically defined performatives, is defined. Each agent can perform its task intelligently by interpreting the commands (performatives) from other agents. Moreover, with the consideration of possible future methodology changes, the internal structure of each functional agent is modularized into several components. Such an architecture ensures that the system is flexible, adaptive and upgradable.

This paper describes an orthogonal machining theory which can be used to determine the stresses, temperatures etc. involved in chip formation from a knowledge of the work material flow stress and thermal properties and cutting conditions. It is shown how these can be used to predict machinability factors such as power consumption, built-up edge range, tool wear rates (tool life) and those cutting conditions which cause plastic deformation of the cutting edge. An oblique machining theory which is more representative of practical machining processes than the orthogonal theory is then described, taking into account machining on more than one cutting edge as in bar turning. Throughout the paper comparisons are made between predicted and experimental results.

The paper describes a computer-based tool for the selection of techniques used in the manufacture of prototypes and limited production runs of industrial products. The underlying decision model, based on the AHP methodology, ranks available techniques by a score resulting from the composition of priorities at different levels, each considering homogeneous and independent evaluation criteria. At each level, priorities are calculated from pairwise comparisons among either manufacturing techniques or properties of the techniques with respect to different types of application. This approach is enhanced with a procedure that adapts the parameters of the decision model to prototype specifications. Compared to scoring procedures, the method reduces the ambiguity on the values of weighting factors and allows an easier interpretation of the rationale behind the selection process.