Matériaux composites à renfort végétal pour l'amélioration des performances de systèmes robotiques

Improvement of the robot’s performances is a major challenge in the industrial field. In general, improvement objectives are increasing workspace, transportable capacity, speed and precision of the robot. To achieve these objectives, it must increase rigidity, reduce weight and increase damping capacity of the robot. Currently, the robots are generally made of metals: aluminum or steel, which limits their performances due to low damping capacity of these materials.Composite materials present an advantage to combine different materials, which leads to a variety of composite material properties. Among the types of reinforcements, carbon fibers show high modulus that enables robotic parts with high static rigidities to be designed. However, carbon fibers have generally a low damping capacity. Natural fibers have low density, good specific properties and high damping capacity.This thesis focuses on the improvement of the performances of the 3CRS parallel robot by using the composite material to redesign robot parts initially made of aluminum. The thesis begins with static and dynamic characterizations of the original robot. Then, the shape of segments of the robotic arms is optimized with respect to applying force on the robot. A hybrid laminated composite reinforced with carbon fibers and flax fibers is proposed for the use. This combination enables to combine the advantages of two fiber types in a composite for using in high loaded components. The structure of the new hybrid laminated composite is optimized and a composite segment is then fabricated in order to validate the design. Finally, the analysis of the new robot with composite arms is executed. The result shows that the new robot has a slightly higher rigidity, lighter mass and considerably greater damping capacity in comparison with the original robot. Therefore, the application of the hybrid composite could improve the static and dynamic performances and increases considerably the accuracy in operation of the robot 3CRS.L’amélioration des performances des robots est un enjeu important dans le domaine industriel. Les objectifs visés sont l’augmentation de l’espace de travail, de la capacité de charge transportable, de la vitesse de travail et de la précision du robot. Pour atteindre ces objectifs, il faut en général augmenter la rigidité, diminuer la masse et augmenter la capacité d’amortissement du robot. Les robots actuels sont généralement fabriqués en métaux : aluminium ou acier, ce qui limite leurs performances en raison des faibles capacités d’amortissement des vibrations de ces matériaux. Les matériaux composites présentent l’avantage de combiner des matériaux différents, ce qui conduit à une variété de leurs performances. Parmi les types de renforts, les fibres de carbone présentent un module d’élasticité élevé permettant la conception de pièces de grandes rigidités statiques mais elles possèdent une faible capacité d’amortissement. Les fibres végétales, par contre, possèdent une faible densité, de bonnes propriétés spécifiques et des capacités d’amortissement élevées. Cette thèse porte sur l’amélioration des performances d’un robot parallèle 3CRS en utilisant des matériaux composites pour reconcevoir des pièces initialement fabriquées en aluminium. La thèse commence d’abord par une caractérisation des comportements statiques et dynamiques du robot initial constitué de bras en aluminium. Ensuite, la forme des segments des bras robotiques est optimisée par rapport aux sollicitations mécaniques sur le robot. Un nouveau composite stratifié hybride renforcé par des fibres de carbone et des fibres de lin est alors proposé. Cette combinaison permet d’allier les avantages des deux types de fibres dans un composite pour le dimensionnement des composants sous sollicitation élevée. La structure de ce nouveau composite a été optimisée puis un segment est fabriqué pour valider la conception. Finalement, l’étude du nouveau robot avec des bras en matériaux composites a été réalisée, les résultats montrent que la rigidité du robot augmente, sa masse diminue légèrement et sa capacité d’amortissement augmente considérablement par rapport au robot initial. Donc, l’application du composite stratifié hybride peut améliorer les performances statiques et dynamiques et augmenter significativement la précision en fonctionnement du robot 3CRS

Parameter identification and model based control of direct drive robots

Imperial Users onl

Large space structures and systems in the space station era: A bibliography with indexes

Bibliographies and abstracts are listed for 1372 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1990 and June 30, 1990. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion, and solar power satellite systems

NASA Tech Briefs, October 2002

Topics include: a technology focus on sensors, electronic components and systems, software, materials, materials, mechanics, manufacturing, physical sciences, information sciences, book and reports, motion control and a special section of Photonics Tech Briefs

Object Detection and Tracking in Cooperative Multi-Robot Transportation

Contemporary manufacturing systems imply the utilization of autonomous robotic systems, mainly for the execution of manipulation and transportation tasks. With a goal to reduce transportation and manipulation time, improve efficiency, and achieve flexibility of intelligent manufacturing systems, two or more intelligent mobile robots can be exploited. Such multi-robot systems require coordination and some level of communication between heterogeneous or homogeneous robotic systems. In this paper, we propose the utilization of two heterogeneous robotic systems, original intelligent mobile robots RAICO (Robot with Artificial Intelligence based COgnition) and DOMINO (Deep learning-based Omnidirectional Mobile robot with Intelligent cOntrol), for transportation tasks within a laboratory model of a manufacturing environment. In order to reach an adequate cooperation level and avoid collision while moving along predefined paths, our own developed intelligent mobile robots RAICO and DOMINO will communicate their current poses, and object detection and tracking system is developed. A stereo vision system equipped with two parallelly placed industrial-grade cameras is used for image acquisition, while convolutional neural networks are utilized for object detection, classification, and tracking. The proposed object detection and tracking system enables real-time tracking of another mobile robot within the same manufacturing environment. Furthermore, continuous information about mobile robot poses and the size of the bounding box generated by the convolutional neural network in the process of detection of another mobile robot is used for estimation of object movement and collision avoidance. Mobile robot localization through time is performed based on kinematic models of two intelligent mobile robots, and conducted experiments within a laboratory model of manufacturing environment confirm the applicability of the proposed framework for object detection and collision avoidance

3D printing materials for large-scale insulation and support matrices : thesis by publications presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering, Massey University, Albany, New Zealand

Figures are re-used with permission.Additive manufacturing (AM) techniques have promising applications in daily life due to their superiority over conventional manufacturing techniques in terms of complexity and ease of use. However, current applications of polymer-based 3D printing (3DP) are limited to small scale only due to the high cost of materials, print times, and physical sizes of the available machines. In addition, the applications of 3DP are yet to be explored for insulation of different large-scale mechanical structures. For example, milk vats are large structures with complex assemblies (like pipes, joints, couplings, valves, ladders, vessel doors) that requires insulation to store the milk at a low temperature of 6 °C as per the NZCP1 regulations in New Zealand. Generally, milk vats lack any kind of proper insulation around them and require additional cooling systems to keep the milk at a prescribed temperature. Any variations in the temperature can lead to deterioration in the quality of milk. Therefore, there exists a research gap that can not only help to solve an industrial issue but also can be a first step towards real large-scale 3DP applications that can potentially lead to many others in future. For example, pipe insulation, food storage tanks, chemical storage tanks, water treatment. This research explores new and inexpensive materials for large-scale 3DP. For this purpose, the current state of the 3DP materials is analyzed and based upon this analysis two distinct approaches are devised: 1) in-process approach to improve the mechanical properties of the existing materials like polylactic acid (PLA), and 2) modification of inexpensive materials (like materials used in injection, rotational, and blow moulding) to make them printable. In the first approach, by controlling the process parameters, mechanical properties are studied. While in the second approach, blends of high density polyethylene (HDPE) and polypropylene (PP) with different thermoplastics (acrylonitrile butadiene styrene, ABS and polylactic acid, PLA) are investigated to achieve printability. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) are used to analyze the proposed materials. The overall objective of this research is to devise low-cost materials comparable to the conventional processes that are capable of providing good mechanical properties (tensile, compressive and flexural) along with high resistance to thermal, moisture, and soil degradation. The results present significant enhancement, up to 30%, in tensile strength of PLA through in-process heat treatment. However, the softness induced during printing above 70 °C directs to the second approach of developing the novel blends of HDPE and PP. In this regard, the research develops three novel blend materials: 1) PLA/HDPE, 2) ABS/HDPE, and 3) ABS/PP. These materials are compatibilized by a common compatibilizer, polyethylene graft maleic anhydride (PE-g-MAH). PLA/HDPE/PE-g-MAH provides highest tensile strength among all existing FDM blends (73.0 MPa) with superior resistance to thermal, moisture and soil degradation. ABS/HDPE and ABS/PP provide one of the highest mechanical properties (tensile, compressive, and flexural) in ABS based FDM blends with superior thermal resistance to six days aging. ii The chemical characterization of aforementioned novel FDM blends shows partial miscibility with sufficient signs of chemical grafting. The significant intermolecular interactions are noted in FTIR that shows the grafting through compatibilizer (PE-g-MAH). The DSC analysis shows visible enhancement in different thermal parameters like glass transition, melt crystallization and degradation along with signs of partial miscibility. Furthermore, TGA analysis confirms the partial miscibility along with the enhanced onset of degradation temperature. The increase in onset temperatures of each of the three blends proves the thermal stability to high temperatures. Hence, each of the developed blends is capable of resisting any material deterioration during routine cleaning operation at 70 °C of milk vats. This research has resulted in 5 journal publication (four published and one submitted), two conference proceedings and a number of posters presented at local conferences. This research is the part of food industry and enabling technologies (FIET) research program funded by the ministry of business, innovation and employment (MBIE), New Zealand in collaboration with Massey University, Auckland

Experimental Investigations on Machining of CFRP Composites: Study of Parametric Influence and Machining Performance Optimization

Carbon Fiber Reinforced Polymer (CFRP) composites are characterized by their excellent mechanical properties (high specific strength and stiffness, light weight, high damping capacity etc.) as compared to conventional metals, which results in their increased utilization especially for aircraft and aerospace applications, automotive, defense as well as sporting industries. With increasing applications of CFRP composites, determining economical techniques of production is very important. However, as compared to conventional metals, machining behavior of composites is somewhat different. This is mainly because these materials behave extremely abrasive during machining operations. Machining of CFRP appears difficult due to their material discontinuity, inhomogeneity and anisotropic nature. Moreover, the machining behavior of composites largely depends on the fiber form, the fiber content, fiber orientations of composites and the variability of matrix material. Difficulties are faced during machining of composites due to occurrence of various modes of damages like fiber breakage, matrix cracking, fiber–matrix debonding and delamination. Hence, adequate knowledge and in-depth understanding of the process behavior is indeed necessary to identify the most favorable machining environment in view of various requirements of process performance yields. In this context, present work attempts to investigate aspects of machining performance optimization during machining (turning and drilling) of CFRP composites. In case of turning experiments, the following parameters viz. cutting force, Material Removal Rate (MRR), roughness average (Ra) and maximum tool-tip temperature generated during machining have been considered as process output responses. In case of drilling, the following process performance features viz. load (thrust), torque, roughness average (of the drilled hole) and delamination factor (entry and exit both) have been considered. Attempt has been made to determine the optimal machining parameters setting that can simultaneously satisfy aforesaid response features up to the desired extent. Using Fuzzy Inference System (FIS), multiple response features have been aggregated to obtain an equivalent single performance index called Multi-Performance Characteristic Index (MPCI). A nonlinear regression model has been established in which MPCI has been represented as a function of the machining parameters under consideration. The aforesaid regression model has been considered as the fitness function, and finally optimized by evolutionary algorithms like Harmony Search (HS), Teaching-Learning Based Optimization (TLBO), and Imperialist Competitive Algorithm (ICA) etc. However, the limitation of these algorithms is that they assume a continuous search within parametric domain. These algorithms can give global optima; but the predicted optimal setting may not be possible to adjust in the machine/setup. Since, in most of the machines/setups, provision is given only to adjust factors (process input parameters) at some discrete levels. On the contrary, Taguchi method is based on discrete search philosophy in which predicted optimal setting can easily be achieved in reality.However, Taguchi method fails to solve multi-response optimization problems. Another important aspect that comes into picture while dealing with multi-response optimization problems is the existence of response correlation. Existing Taguchi based integrated optimization approaches (grey-Taguchi, utility-Taguchi, desirability function based Taguchi, TOPSIS, MOORA etc.) may provide erroneous outcome unless response correlation is eliminated. To get rid of that, the present work proposes a PCA-FuzzyTaguchi integrated optimization approach for correlated multi-response optimization in the context of machining CFRP composites. Application potential of aforementioned approach has been compared over various evolutionary algorithms

Dynamic modeling, property investigation, and adaptive controller design of serial robotic manipulators modeled with structural compliance

Research results on general serial robotic manipulators modeled with structural compliances are presented. Two compliant manipulator modeling approaches, distributed and lumped parameter models, are used in this study. System dynamic equations for both compliant models are derived by using the first and second order influence coefficients. Also, the properties of compliant manipulator system dynamics are investigated. One of the properties, which is defined as inaccessibility of vibratory modes, is shown to display a distinct character associated with compliant manipulators. This property indicates the impact of robot geometry on the control of structural oscillations. Example studies are provided to illustrate the physical interpretation of inaccessibility of vibratory modes. Two types of controllers are designed for compliant manipulators modeled by either lumped or distributed parameter techniques. In order to maintain the generality of the results, neither linearization is introduced. Example simulations are given to demonstrate the controller performance. The second type controller is also built for general serial robot arms and is adaptive in nature which can estimate uncertain payload parameters on-line and simultaneously maintain trajectory tracking properties. The relation between manipulator motion tracking capability and convergence of parameter estimation properties is discussed through example case studies. The effect of control input update delays on adaptive controller performance is also studied

Design considerations for light weight mechanical parts

Context and Background - Lightweight design is important for many engineering fields due to the increased energy efficiency and process performance that it can result in. Functionally graded materials (FGMs) give a key contribution to lightweight design when low mass along with a gradual change in a second primary constraint is required such as alleviation of a large temperature gradient. With the evolution of additive manufacturing (AM), FGM use for light weighting is rising in practicality. Therefore, research into combining FGMs with AM is required, and should include topics relevant to these, including form, material choice and structural design. The work is tested on robotic arm links due to the ever-increasing adoption of automation, and the practical accessibility of them for the researcher. Aim of Research - The aim of the research is to investigate the mass reduction of robotic arm links by merging second moment of area calculations, structured cells, topology optimisation, functionally graded materials and additive manufacture in various combinations. Key Work - The main output of this work is a set of design guidelines that have been written to assist engineers with combining FGMs, topology optimisation, structured cells and high-level AM restrictions. Within the field of lightweight design, the guidelines are use-case agnostic. The design guidelines have been trialled using test cases, each aimed at individual elements of the guidelines. The objective of the first test case is to discover if FGMs will reduce stresses in parts constructed of dissimilar materials when used in conjunction with high-level AM constraints. The second test case trails the various computational testing sections required in the guidelines, including part sectioning rules and material distribution techniques. The third test case incorporates heat ow simulation during AM deposition of the FGMs, including the three heat transfer mechanisms and interaction with the print bed of AM hardware. The final test case assesses the entirety of the design guidelines, re-examining the aspects tested in the second and third test cases, together with a technique to decide whether structured cells or topology optimisation should be used based on the use case of the part, and a first pass at inspecting the residual stresses in the additively manufactured part once it has cooled. Conclusions - Overall, the use of FGMs along with lightweight structural design techniques and high-level AM restrictions are computationally successful at reducing the mass in robotic arm links. While the design guidelines are use case agnostic, they make most sense used in fields of engineering that have a substantial requirement for light weight design, such as aerospace and space. Ideally, physical testing would have been used to increase validity of the design guidelines. Unfortunately, funds were not available, and thus physical testing is deemed the next step for this work in the future.Context and Background - Lightweight design is important for many engineering fields due to the increased energy efficiency and process performance that it can result in. Functionally graded materials (FGMs) give a key contribution to lightweight design when low mass along with a gradual change in a second primary constraint is required such as alleviation of a large temperature gradient. With the evolution of additive manufacturing (AM), FGM use for light weighting is rising in practicality. Therefore, research into combining FGMs with AM is required, and should include topics relevant to these, including form, material choice and structural design. The work is tested on robotic arm links due to the ever-increasing adoption of automation, and the practical accessibility of them for the researcher. Aim of Research - The aim of the research is to investigate the mass reduction of robotic arm links by merging second moment of area calculations, structured cells, topology optimisation, functionally graded materials and additive manufacture in various combinations. Key Work - The main output of this work is a set of design guidelines that have been written to assist engineers with combining FGMs, topology optimisation, structured cells and high-level AM restrictions. Within the field of lightweight design, the guidelines are use-case agnostic. The design guidelines have been trialled using test cases, each aimed at individual elements of the guidelines. The objective of the first test case is to discover if FGMs will reduce stresses in parts constructed of dissimilar materials when used in conjunction with high-level AM constraints. The second test case trails the various computational testing sections required in the guidelines, including part sectioning rules and material distribution techniques. The third test case incorporates heat ow simulation during AM deposition of the FGMs, including the three heat transfer mechanisms and interaction with the print bed of AM hardware. The final test case assesses the entirety of the design guidelines, re-examining the aspects tested in the second and third test cases, together with a technique to decide whether structured cells or topology optimisation should be used based on the use case of the part, and a first pass at inspecting the residual stresses in the additively manufactured part once it has cooled. Conclusions - Overall, the use of FGMs along with lightweight structural design techniques and high-level AM restrictions are computationally successful at reducing the mass in robotic arm links. While the design guidelines are use case agnostic, they make most sense used in fields of engineering that have a substantial requirement for light weight design, such as aerospace and space. Ideally, physical testing would have been used to increase validity of the design guidelines. Unfortunately, funds were not available, and thus physical testing is deemed the next step for this work in the future