Collision-free motion of two robot arms in a common workspace

Collision-free motion of two robot arms in a common workspace is investigated. A collision-free motion is obtained by detecting collisions along the preplanned trajectories using a sphere model for the wrist of each robot and then modifying the paths and/or trajectories of one or both robots to avoid the collision. Detecting and avoiding collisions are based on the premise that: preplanned trajectories of the robots follow a straight line; collisions are restricted to between the wrists of the two robots (which corresponds to the upper three links of PUMA manipulators); and collisions never occur between the beginning points or end points on the straight line paths. The collision detection algorithm is described and some approaches to collision avoidance are discussed

Towards building a team of intelligent robots

Topics addressed include: collision-free motion planning of multiple robot arms; two-dimensional object recognition; and pictorial databases (storage and sharing of the representations of three-dimensional objects)

Motion planning of mobile robot in dynamic environment using potential field and roadmap based planner

Mobile robots are increasingly being used to perform tasks in unknown environments. The potential of robots to undertake such tasks lies in their ability to intelligently and efficiently locate and interact with objects in their environment. My research focuses on developing algorithms to plan paths for mobile robots in a partially known environment observed by an overhead camera. The environment consists of dynamic obstacles and targets. A new methodology, Extrapolated Artificial Potential Field, is proposed for real time robot path planning. An algorithm for probabilistic collision detection and avoidance is used to enhance the planner. The aim of the robot is to select avoidance maneuvers to avoid the dynamic obstacles. The navigation of a mobile robot in a real-world dynamic environment is a complex and daunting task. Consider the case of a mobile robot working in an office environment. It has to avoid the static obstacles such as desks, chairs and cupboards and it also has to consider dynamic obstacles such as humans. In the presence of dynamic obstacles, the robot has to predict the motion of the obstacles. Humans inherently have an intuitive motion prediction scheme when planning a path in a crowded environment. A technique has been developed which predicts the possible future positions of obstacles. This technique coupled with the generalized Voronoi diagram enables the robot to safely navigate in a given environment

Improvement of Geometric Quality Inspection and Process Efficiency in Additive Manufacturing

Additive manufacturing (AM) has been known for its ability of producing complex geometries in flexible production environments. In recent decades, it has attracted increasing attention and interest of different industrial sectors. However, there are still some technical challenges hindering the wide application of AM. One major barrier is the limited dimensional accuracy of AM produced parts, especially for industrial sectors such as aerospace and biomedical engineering, where high geometric accuracy is required. Nevertheless, traditional quality inspection techniques might not perform well due to the complexity and flexibility of AM fabricated parts. Another issue, which is brought up from the growing demand for large-scale 3D printing in these industry sectors, is the limited fabrication speed of AM processes. However, how to improve the fabrication efficiency without sacrificing the geometric quality is still a challenging problem that has not been well addressed. In this work, new geometric inspection methods are proposed for both offline and online inspection paradigms, and a layer-by-layer toolpath optimization model is proposed to further improve the fabrication efficiency of AM processes without degrading the resolution. First, a novel Location-Orientation-Shape (LOS) distribution derived from 3D scanning output is proposed to improve the offline inspection in detecting and distinguishing positional and dimensional non-conformities of features. Second, the online geometric inspection is improved by a multi-resolution alignment and inspection framework based on wavelet decomposition and design of experiments (DOE). The new framework is able to improve the alignment accuracy and to distinguish different sources of error based on the shape deviation of each layer. In addition, a quickest change point detection method is used to identify the layer where the earliest change of systematic deviation distribution occurs during the printing process. Third, to further improve the printing efficiency without sacrificing the quality of each layer, a toolpath allocation and scheduling optimization model is proposed based on a concurrent AM process that allows multiple extruders to work collaboratively on the same layer. For each perspective of improvements, numerical studies are provided to emphasize the theoretical and practical meanings of proposed methodologies

Industrial manipulators collision detection algorithms

In this work we present some algorithms for detecting collisions between two robots. Firstly we estimate robot trajectories given via points and workcell configuration, then we develop the actual algorithm to detect collisions, providing multiple models of each link which differ in reliability and simplicity. The algorithm is then optimized for anthropomorphic robots, in order to be performed on-line. Finally some results are summarized, which show the effective behaviour in worst case

Coordenação de multi-robots num ambiente industrial

Atualmente, uma grande diversidade dos ambientes industriais recorrem à utilização de vários robôs móveis para executar as tarefas a si associadas. Pela grande mobilidade que lhes é conferida surge o problema de controlo de tráfego, dentro de um ambiente limitado. Para que tal seja possível é necessário implementar um sistema capaz de efetuar a coordenação entre os diferentes veículos, evitando colisões e bloqueios mútuos, também designados por deadlocks. O principal foco desta dissertação prende-se, portanto, na implementação desse sistema, tendo como base o algoritmo de planeamento de trajetórias TEA*. Tendo como base o algoritmo A*, este promove uma pesquisa dos caminhos ótimos e livres de colisão ao longo de diversas camadas temporais. A ideia fundamental do algoritmo passa por planear a trajetória de cada robô tendo como ponto de partida as posições correntes e futuras de cada um dos seus veículos concorrentes. Após a sua implementação pretende-se validar o sistema em ambiente real, através da utilização de 3 a 4 robôs inseridos numa plataforma de testes coma geometria de um labirinto

물체 수송을 위한 협업 로봇의 행동 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2016. 2. 이범희.This dissertation presents two cooperative object transportation techniques according to the characteristics of objects: passive and active. The passive object is a typical object, which cannot communicate with and detect other robots. The active object, however, has abilities to communicate with robots and can measure the distance from other robots using proximity sensors. Typical areas of research in cooperative object transportation include grasping, pushing, and caging techniques, but these require precise grasping behaviors, iterative motion correction according to the object pose, and the real-time acquisition of the object shape, respectively. For solving these problems, we propose two new object transportation techniques by considering the properties of objects. First, this dissertation presents a multi-agent behavior to cooperatively transport an active object using a sound signal and interactive communication. We first developed a sound localization method, which estimates the sound source from an active object by using three microphone sensors. Next, since the active object cannot be recalled by only a single robot, the robots organized a heterogeneous team by themselves with a pusher, a puller, and a supervisor. This self-organized team succeeded in moving the active object to a goal using the cooperation of its neighboring robots and interactive communication between the object and robots. Second, this dissertation presents a new cooperative passive object transportation technique using cyclic shift motion. The proposed technique does not need to consider the shape or the pose of objects, and equipped tools are also unnecessary for object transportation. Multiple robots create a parallel row formation using a virtual electric dipole field and then push multiple objects into the formation. This parallel row is extended to the goal using cyclic motion by the robots. The above processes are decentralized and activated based on the finite state machine of each robot. Simulations and practical experiments are presented to verify the proposed techniques.Chapter 1 Introduction 1 1.1 Background and Motivation 1 1.2 Related Work 4 1.2.1 The Categories of Object Transportation Techniques 4 1.2.2 Sound Localization Techniques for Active Object Transportation 7 1.3 Contributions 8 1.4 Organization 10 Chapter 2 Object Transportation Problem 11 2.1 Passive Object versus Active Object 11 2.2 Problem Formulation 13 2.3 Assumptions 13 Chapter 3 Active Object Transportation using a Sound Signal and Interactive Communication 15 3.1 Overview of Active Object Transportation 16 3.2 Sound Vector Generation using Triple Microphones 17 3.2.1 Sound Isocontour Generation using ILD 18 3.2.2 Sound Circle Generation using Inverse-square Law 21 3.2.3 Sound Vector Generation 22 3.3 Cooperative Control Method using Interactive Communication 25 3.3.1 Role Assignment of Multi-robot Team 25 3.3.2 Position Assignment of Multi-robot Team 26 3.3.3 Transportation Process of an Active Object 29 Chapter 4 Passive Object Transportation using Cyclic Shift Motion 33 4.1 Overview of Passive Object Transportation 34 4.2 Multi-robot Team Organization 35 4.3 Row Formation Generation using Multiple Robots 37 4.3.1 Cyclic Shift Motion 37 4.3.2 Path Generation using Virtual Electric Dipole Field 39 4.3.3 Path Following using Bang-bang Controller 42 4.4 Multi-object Transportation by a Decentralized Multi-robot Team 45 4.4.1 Information Acquisition Methods for Finite State Machine 45 4.4.2 Finite State Machines (FSMs) 48 4.4.2.1 The FSM of Guider Robots 49 4.4.2.2 The FSM of a Pusher Robot 52 4.4.2.3 The FSM of a Leader Robot 54 4.4.3 Object Transportation Process 55 4.4.4 Formation Constraints for Curved Transportation Path 57 Chapter 5 Simulation Results 61 5.1 Simulation Environment 61 5.2 Simulation Result of Passive Object Transportation 63 5.3 Comparison Results with Other Passive Object Transportation Techniques 69 5.3.1 Simulation Result of Leader-Follower Technique 70 5.3.2 Simulation Result of Caging Technique 72 Chapter 6 Practical Experiments 77 6.1 Experimental Environment 77 6.2 Experimental Results of Active Object Transportation 81 6.2.1 Experimental Result of the SV Estimation 81 6.2.2 Experimental Result of Active Object Transportation 82 6.3 Experimental Results of Passive Object Transportation 86 6.3.1 Small-object Transportation with Straight Path 86 6.3.2 Small-object Transportation with Curved Path 91 6.3.3 Large-object Transportation 93 6.4 Comparison Result with Caging Technique 95 Chapter 7 Discussion 96 Chapter 8 Conclusions 99 Appendix A: The Approaching Phase of Passive Object Transportation 101 A.1 Approaching Phase 101 A.2 Experimental Result of Approaching Phase 107 Appendix B: Object Transportation in a Static Environment 109 B.1 Overview 109 B.2 Object Transportation Problem in a Static Environment 111 B.3 Multi-object Transportation using Hybrid System 112 B.4 New Finite State Machines 113 B.4.1 The States of Guider Robots 114 B.4.2 The States of a Pusher Robot 115 B.4.3 The States of a Leader Robot 116 B.5 Simulation Results 118 B.5.1 Simulation Result: An Obstacle 118 B.5.2 Simulation Result: Two Obstacles 120 B.6 Practical Experiment 122 Bibliography 124Docto