A novel coordination framework for multi-robot systems

Having made great progress tackling the basic problems concerning single-robot systems, many researchers shifted their focus towards the study of multi-robot systems (MRS). MRS were shortly found to be a perfect t for tasks considered to be hard, complex or even impossible for a single robot to perform, e.g. spatially separate tasks. One core research problem of MRS is robots' coordinated motion planning and control. Arti cial potential elds (APFs) and virtual spring-damper bonds are among the most commonly used models to attack the trajectory planning problem of MRS coordination. However, although mathematically sound, these approaches fail to guarantee inter-robot collision-free path generation. This is particularly the case when robots' dynamics, nonholonomic constraints and complex geometry are taken into account. In this thesis, a novel bio-inspired collision avoidance framework via virtual shells is proposed and augmented into the high-level trajectory planner. Safe trajectories can hence be generated for the low-level controllers to track. Motion control is handled by the design of hierarchical controllers which utilize virtual inputs. Several distinct coordinated task scenarios for 2D and 3D environments are presented as a proof of concept. Simulations are conducted with groups of three, four, ve and ten nonholonomic mobile robots as well as groups of three and ve quadrotor UAVs. The performance of the overall improved coordination structure is veri ed with very promising result

Design and implementation of a vision based in-situ defect detection system of automated fiber placement process

In this paper, an in-situ defect detection system is proposed for automated fiber placement (AFP) process monitoring. To acquire meaningful data about the laid-up tows, the design, manufacturing and integration of a flexible three degrees of freedom vision system to the AFP machine is proposed. An image segmentation algorithm is developed to locate and isolate defects in input images. The proposed algorithm utilizes Gabor filters to extract the desired texture features which is followed by an adaptive thresholding. Successful results with four of the main defect classes namely, foreign bodies, wrinkles, gaps and bridging, were obtained. This monitoring system can reduce time-consuming and expensive efforts of manual quality inspection and will significantly increase AFP process reliability