Multi-Robot Cooperation Systems for Assembly Automobile Industry
Joana Raquel Ramiro Santos · Open Repository of the University of Porto (University of Porto) · 2014
Increasingly, companies have the need to optimize their production system and the automation of the processes is, many times, one of the solutions. The coordination of multiple robots, represents a challenge in the robotic community. A single solution does not exist, because it depends of the application, the level of difficulty and the time requirements. However any well developed multi-robot system, ensures greater efficiency and speed in the execution of a set of tasks, instead of the use of a single robot. In this sense, it’s required an algorithm that executes the coordination of multiple automoted guided vehicles. This dissertation proposes to solve a multi-robot coordination problem, under the project STAMINA. This project is inserted in the Robotics Unit and Intelligent Systems of the INESC TEC Porto. This is a research center dedicated to the development of the robotic solutions that contributes to the industry needs and to the development of new technologies. In addition to the study of the available platforms to develop and test the coordination algorithm, this work had as objective to build a robust method to coordinate several AGVs. ROS (Robotic Operating System) was used as an integration platform due to its excellent properties as tool for the code development to robotic systems. Furthermore, there is a ROS community that allows sharing and reusing several methods and functions. The main advantage of its use it’s the possibility of integrate many processing nodes, on the same system. Thus a complex task can be divided, in order to develop simple tasks in independent ROS nodes. Later, these tasks can be integrated on the complete system. On this dissertation, ROS was used to integrate the node which contains the coordination algorithm with the respective nodes of each AGV and finally communicates with the simulator. Initially, considering the requirements of this project, were studied the available simulators on the market, and analyzed the features of each one . Four interesting simulation softwares are described. A study about some path planning methods and some developed works in the area of multirobot coordination were made. Based on the A* path planning algorithm, was considered interesting to develop an extension of this method, Time enhanced A* Algorithm. The main difference of this algorithm is that the initial map is a three-dimensional matrix that includes the time component. This additional feature allows it, to determine the optimal path for each AGV, considering the map obstacles, and the movements of the other AGVs. To provide a better evaluation of the proposed algorithm, was also implemented a method studied on the Literature Review, the Modified Banker’s Algorithm. This method presents a different approach, in terms of the map’s construction and in the way how the path control is done. The capacity to avoid collisions and deadlocks were some of the comparison criteria considered. These are the main critical problems that any coordination method should be able to solve. In this sense, are presented the methodologies used by each algorithm in order to avoids or solves these situations. Finally, are shown some results of the Time enhanced A*, for a better understanding and anal-