A novel surface segmentation approach for robotic manipulator-based maintenance operation planning

This paper presents a novel approach to segmenting a three-dimensional surface map by considering the task requirements and the movements of an industrial robot manipulator. Maintenance operations, such as abrasive blasting, that are performed by a field robot manipulator can be made more efficient by exploiting surface segmentation. The approach in this paper utilises an aggregate of multiple connectivity graphs, with graph edges defined by task constraints, and graph vertices that correspond to small, maintenance-specific target surfaces, known as Scale-Like Discs (SLDs). The task constraints for maintenance operations are based on the characteristics of neighbouring SLDs. The combined connectivity graphs are analysed to find clusters of vertices, thus segmenting the surface map into groups of related SLDs. Experiments conducted in three typical bridge maintenance environments have shown that the approach can reduce garnet usage by 10%-40% and reduce the manipulator joint movements by up to 35%. © 2012 Elsevier B.V. All rights reserved

Segmentation and Coverage Planning of Freeform Geometries for Robotic Surface Finishing

Surface finishing such as grinding or polishing is a time-consuming task, involves health risks for humans and is still largely performed by hand. Due to the high curvatures of complex geometries, different areas of the surface cannot be optimally reached by a simple strategy using a tool with a relatively large and flat finishing disk. In this paper, a planning method is presented that uses a variable contact point on the finishing disk as an additional degree of freedom. Different strategies for covering the workpiece surface are used to optimize the surface finishing process and ensure the coverage of concave areas. Therefore, an automatic segmentation method is developed to find areas with a uniform machining strategy based on the exact tool and workpiece geometry. Further, a method for planning coverage paths is presented, in which the contact area is modeled to realize an adaptive spacing between path lines. The approach was evaluated in simulation and practical experiments on the DLR SARA robot. The results show high coverage for complex freeform geometry and that adaptive spacing can optimize the overall process by reducing uncovered gaps and overlaps between coverage lines

2차원 균일 커버리지 경로 계획을 위한 효율적 알고리즘

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 기계공학부, 2020. 8. 박종우.Coverage path planning (CPP) is widely used in numerous robotic applications. With progressively complex and extensive applications of CPP, automating the planning process has become increasingly important. This thesis proposes an efficient CPP algorithm based on a random sampling scheme for spray painting applications. We have improved on the conventional CPP algorithm by alternately iterating the path generation and node sampling steps. This method can reduce the computational time by reducing the number of sampled nodes. We also suggest a new distance metric called upstream distance to generate reasonable path following given vector field. This induces the path to be aligned with a desired direction. Additionally, one of the machine learning techniques, support vector regression (SVR) is utilized to identify the paint distribution model. This method accurately predict the paint distribution model as a function of the painting parameters. We demonstrate our algorithm on several types of analytic surfaces and compare the results with those of conventional methods. Experiments are conducted to assess the performance of our approach compared to the traditional method.본 논문에서는 2차원 표면의 균일 커버리지 경로 계획을 설명하고 이를 효율적으로 푸는 알고리즘을 제시한다. 우리는 경로 계획 문제를 두 개의 하위 문제로 분리하여 각각 푸는 기존의 방식을 보완하여 두 개의 하위문제를 한 번에 풀면서 계산시간을 줄이는 방법을 제시하였다. 또한 경우에 따라 주어진 벡터 필드와 나란한 방향으로 경로가 생성될 필요가 있는데 이를 위해 거스름 거리(upstream distance)의 개념을 제시하였으며 여행 외판원 문제(Traveling Salesman Problem)를 풀 때 이를 적용하였다. 우리는 차량 도장 응용분야에 균일 커버리지 경로 계획법을 적용하였으며 도장 시스템을 고려하여 균일한 페인트 두께를 보장하는 방법을 같이 제시하였다. 네 가지 타입의 2차원 곡면에 대해 시뮬레이션을 진행하였으며 기존의 방법에 비해 더 적은 계산시간을 요구하면서도 합리적인 수준의 페인트 균일도를 달성함을 검증하였다.1 Introduction 1 1.1 Related Work 3 1.2 Contribution of Our Work 7 1.3 Organization of This Thesis 8 2 Preliminary Background 9 2.1 Elementary Differential Geometry of Surfaces in R3 10 2.1.1 Representation of Surfaces 10 2.1.2 Normal Curvature 10 2.1.3 Shape Operator 12 2.2 Traveling Salesman Problem 15 2.2.1 Definition 15 2.2.2 Variations of the TSP 17 2.2.3 Approximation Algorithm for TSP 19 2.3 Path Planning on Vector Fields 20 2.3.1 Randomized Path Planning 20 2.3.2 Upstream Criterion 20 2.4 Support Vector Regression 21 2.4.1 Single-Output SVR 21 2.4.2 Dual Problem of SVR 23 2.4.3 Kernel for Nonlinear System 25 2.4.4 Multi-Output SVR 26 3 Methods 29 3.1 Efficient Coverage Path Planning on Vector Fields 29 3.1.1 Efficient Node Sampling 31 3.1.2 Divide and Conquer Strategy 32 3.1.3 Upstream Distance 34 3.2 Uniform Coverage Path Planning in Spray Painting Applications 35 3.2.1 Minimum Curvature Direction 35 3.2.2 Learning Paint Deposition Model 36 4 Results 38 4.1 Experimental Setup 38 4.2 Simulation Result 41 4.3 Discussion 41 5 Conclusion 45 Bibliography 47 국문초록 52Maste

Planification de trajectoires pour placement automatisé de fibres sur surfaces de géométries complexes

RÉSUMÉ Durant les 50 dernières années, l’utilisation des matériaux composites pour la fabrication de structures à hautes performances a connu un essor, dû notamment à l’industrie aéronautique. Toujours à la recherche de matériaux plus légers et performants pour la construction d’aéronefs, et devant tenir compte des contraintes de productivité pour rester compétitif, ce secteur a encouragé le développement de nouvelles technologies de production telles que le Placement Automatisé de Fibres (AFP). Cette technologie permet d’automatiser la production de structures en matériaux composites à l’aide de pré-imprégnés. Ces derniers se présentent sous forme de bandes composées de tresses de fibres (verre, carbone, etc.) imprégnées de résine semi-polymérisée. La plupart des cellules d’AFP actuellement en service ont été conçues pour la fabrication de larges panneaux plats ou présentant de faibles courbures, comme par exemple les fuselages d’avion. Cependant le secteur de l’aéronautique, mais également les industries de production d’équipement de sport s’intéressent à présent à cette technique pour la fabrication de pièces de plus faibles dimensions et possédant des géométries plus complexes. L’objectif du projet dans lequel s’inscrit le travail présenté ici est donc de mettre au point une cellule de travail et des techniques permettant la production de telles pièces par AFP. La recherche présentée dans ce mémoire concerne plus particulièrement le développement de nouvelles méthodes de planification de trajectoires pour AFP. La majeure partie de l’étude s’est concentrée sur la génération de celles-ci sur un type de surfaces en particulier : les surfaces de révolution multi-axiales de section circulaire constante telles que des tubes en forme de « Y ». Plusieurs algorithmes de génération de trajectoires seront présentés au travers de ce mémoire, chacun cherchant à couvrir la surface de la pièce le plus complètement possible afin de produire des objets finaux en un seul tenant. La méthodologie utilisée dans deux de ces algorithmes est de couvrir individuellement chaque branche par des trajectoires dérivant des hélices. Dans un cas l’hélice sera coupée au niveau de la jonction entre les branches (algorithme HD) et dans l’autre cas cette hélice pourra être déformée (algorithme HA) pour épouser les contours de la jonction. Les différentes branches seront ensuite liées entre elles grâce à une trajectoire définie sur l’intersection des cylindres. Ces deux méthodes ont cependant révélé posséder plusieurs défauts qui pourraient compromettre leur utilisation en pratique, ou conduire à la production de pièces présentant des défauts affaiblissant leurs propriétés mécaniques. Deux autres algorithmes ont donc été développés afin d’améliorer les trajectoires produites.----------ABSTRACT During the past 50 years, the use of composite materials drastically increase, mainly thanks to the interest of aeronautical industries for these strong and lightweight materials. To improve the productivity of composite materials manufacturing some of the largest aeronautics companies began to develop automated processes such as Automated Fibre Placement (AFP). The AFP workcells currently used by the industry were mainly developed for production of large, nearly flat, plates with low curvatures such as aircraft fuselages. However, the fields of aeronautics and sport goods production begin nowadays to show an interest for manufacturing of smaller and more complex parts. The aim of the project in which this research takes place is to design a new AFP workcell and to develop new techniques allowing production of parts with small size and complex geometry. The work presented in this thesis focuses on the path planning on multi-axial revolution surfaces, e.g. Y-shaped tubes of constant circular cross section. Several path planning algorithms will be presented aiming at the exhaustive coverage of a mandrel with pre-impregnated (prepreg) composite tape. The methodology used in two of these algorithms is to individually cover each branch of the Y-shaped part with paths deriving from a helix. In the first one, the helix will be cut at the boundary between a branch and the junction region (algorithm HD) while in the second (algorithm HA) the pseudo-helix path can be adjusted to follow this boundary. These two methods were shown to have some drawbacks compromising their practical use and possibly leading to parts with diminished mechanical properties. To avoid these drawbacks, two others algorithms were developed with a new methodology. With them, the aim is to cover two branches of the Y-shape with a continuous course (i.e. without cut). The first one uses a well known strategy which defines plies with a constant fibre orientation. Parallel paths are then computed to generate a full and uniform ply covering two branches. Once again this method suffers from a main drawback, namely that it can produce highly curved paths leading to manufacturing defects. To overcome this limitation, a last algorithm is proposed ensuring that the maximal curvature of a trajectory stays below a fixed threshold. However, fulfilling this constraint prevents to predict the complete shape of the path and to ensure a perfectly uniform coverage. It is thus proposed to generate an exhaustive set of trajectories having different shapes and covering all the part. Then, a selection algorithm is used to choose the ones which are best suited according to selection criteria

Design and Optimization of a Robot for Abrasive Waterjet Polishing of Hydraulic Turbine Blades

RÉSUMÉ Dans l’industrie de fabrication de turbine hydraulique, toutes les surfaces de turbines qui sont en contact avec de l’eau devraient être polies afin d’obtenir la qualité et l’efficacité maximales. Pour cela, il est nécessaire d’utiliser une méthode de polissage qui peut avoir accès à toutes les surfaces des turbines incluant leurs bords, leurs zones restreintes et leurs courbures serrées. En raison des propriétés particulières qu’offre la technique de polissage par jet d’eau abrasif, celle-ci peut être utilisée pour accomplir cette tâche. Par conséquent, dans cette recherche, les propriétés de cette méthode non-conventionnelle sont examinées dans un premier temps et les principaux paramètres affectant ses performances sont alors déterminés. Ensuite, les conditions nécessaires de manipulations de la buse de pulvérisation vis-à-vis des surfaces courbes sont étudiées et les propriétés d’un bras robotisé pour manipuler celle-ci sont obtenues afin de réaliser cette tâche d’une manière appropriée. Par après, plusieurs mécanismes robotiques tels que des mécanismes sériels, parallèles à membrures, parallèles à câbles, et des robots hybrides sont considérés et leurs capacités à être utilisé dans ce processus sont analysées. Il est alors démontré qu’une l’architecture hybride est le meilleur candidat à retenir pour le design d’un robot de polissage par jet d’eau abrasif. Ensuite, l’architecture conceptuelle d’un robot hybride à 5 DDL est proposée. La structure du robot est constituée d’un mécanisme parallèle à câbles à 3 DDL et d’un poignet sériel à 2 DDL. Afin d’améliorer les propriétés cinématiques du mécanisme à câbles tout en minimisant le nombre d’actionneurs nécessaires, il est proposé d’utiliser des différentiels pour guider ce robot manipulateur. Aussi, la rigidité et la compacité du mécanisme sont améliorées en utilisant une liaison prismatique. Par la suite, les systèmes à câbles différentiels sont examinés et les différences entre leurs propriétés cinématiques et celles de systèmes actionnés indépendamment pour chaque câble sont décrites. Il est démontré que la force résultante de tous les câbles d’un différentiel à câbles doit être prise en compte dans son analyse cinématique. En effet, dans un système différentiel planaire, la direction de la force résultante n’est pas fixée vers un point particulier. Mais plutôt, elle se déplace dans le plan de ce système différentiel. Cette propriété peut être bénéfique pour les propriétés cinématiques des robots à câbles. En comparant deux types d’espace de travail de plusieurs robots planaires actionnés par des mécanismes différentiels par rapport à leurs équivalents pleinement actionnés, il est alors montré qu’en utilisant ces mécanismes, les espaces de travail des robots planaires à câbles peuvent être améliorés. Cependant, cette même propriété qui augmente la plage de variation de la direction de la force résultante dans un câble différentiel, diminue aussi son amplitude. Ainsi, le design optimal d’un différentiel à câble résulte d’un compromis entre ces deux propriétés.----------ABSTRACT In hydraulic turbine manufacturing, all surfaces of the turbines which are in contact with the water flow should be polished to obtain the desired quality and maximal efficiency. For this, it is needed to use an effective polishing method which can have access to all surfaces of the turbines including edges, narrow areas and tight bends. Because of the particular properties of the abrasive waterjet polishing technique, it can be used to accomplish this task. Therefore, in this research, the properties of this non-conventional method are first investigated and the main parameters affecting its performance are then determined. Next, the manipulation requirements of the jet nozzle over free-form surfaces are studied and the properties of a robotic arm to appropriately perform this task are obtained. Afterwards, several robotic mechanisms, e.g., serial, linkage-driven parallel, cabledriven parallel, and hybrid robots are considered and their abilities to be used in this process are investigated. It is then shown that a hybrid architecture is the best candidate for the design of an abrasive waterjet polishing robot. Next, the conceptual design of a 5-DOF hybrid robot is proposed. The structure of this robot is made of a 3-DOF cable-driven parallel mechanism and a 2-DOF serial wrist. To improve the kinematic properties of the cable-driven mechanism while the number of required actuators is kept at a minimum, it is proposed to use cable differentials to drive this manipulator. Also, the rigidity and compactness of the mechanism is improved through the use of a prismatic joint in its structure. Afterwards, differentially driven cable systems are investigated and the differences between their kinematic properties and these of independently actuated cables are described. It is shown that the resultant force of all cables of a cable differential should be taken into account in its kinematic analysis. Indeed, in a planar differential, the direction of the resultant force is not fixed toward a particular point. Instead, it moves within the plane of that differential. This property can be beneficial in the kinematic properties of differentially driven cable robots. By comparing two types of workspaces of several planar robots actuated by differentials with their fully actuated counterparts, it is then shown that using these mechanisms, these workspaces of planar cable robots can be improved. However, the same property that increases the range of variation of the resultant force direction in a cable differential, decreases its magnitude. Thus, the optimal design of a cable differential is a trade-off between these two properties. Next, a synthesis method is presented to find all possible arrangements of the cable differentials to generalize the idea of using such mechanisms in the design of planar cable robots. Additionally, the application of differentials in spatial robots is also investigated and it is shown that they have properties similar to the planar types