Ivica Draganjac

Multi-Agent Formation Control Based on Bell-Shaped Potential Functions

In this paper we analyze stability properties of multi-agent control system with an artificial potential based on bell-shaped functions. In our approach attractive and repulsive forces created by potential gradient have the same form. This particular property allows definition of target formation that is parameter invariant. Due to the fact that agents are identical, the proposed structure of formation potential is invariant to the interchange of agents configurations, hence, target in which particular agent would eventually end up, depends only on formation initial condition. It has been demonstrated that stability analysis, given for stationary targets, applies to moving targets formation as well. We show that position of unwanted stable equilibria can be controlled by a single parameter that defines an elementary potential function. This fact has been used for synthesis of an adaptation algorithm, such that arrival of agents at required formation is guarantied. Simulation results, presented at the end of the paper, confirm correctness of the proposed control scheme.

Decentralized control of free ranging AGVs in warehouse environments

In this paper we propose an algorithm for decentralized control of Automated Guided Vehicles (AGVs) operating in automated warehouse environments. The motion planning part of the algorithm provides vehicles with capabilities for autonomous motion planning considering nonholonomic vehicle constraints and collision-free path execution. The decision making part of the algorithm ensures safe vehicle motions and reliable conflict situation resolution. The proposed control algorithm also prevents occurrence of deadlock and livelock situations. Stability of the algorithm has been proven by its analysis based on automata theory, while its performance has been validated by simulation on a system comprising twenty vehicles as well as experimentally on a laboratory setup comprising five Pioneer 3DX vehicles.

Decentralized Control of Multi-AGV Systems in Autonomous Warehousing Applications

In this paper, we present an algorithm for decentralized control of multiple automated guided vehicles performing transportation tasks within industrial and warehousing environments. By running on each vehicle in the system, the algorithm provides vehicles with capabilities for autonomous path planning and motion co-ordination. The path planning part of the algorithm implements a free-ranging motion scheme by determining the shortest feasible paths considering nonholonomic vehicle constraints. The motion co-ordination part of the algorithm ensures safe vehicle motions by reliable detection and resolution of different conflict situations with other vehicles in the shared workspace. Conflict resolution is based on a vehicle priority scheme and results in temporary stopping or removal of the lower priority vehicles taking part in the conflict. Removal action is always performed within the vehicles private zone, i.e., the pre-allocated local region of the workspace surrounding the vehicle. By encoding information on the vehicle size and its kinematic constraints, the introduced private zone mechanism provides the necessary physical space required for successful execution of every removal action. We also analyze the stability of the presented algorithm and discuss its deadlock-free and livelock-free properties. Algorithm performance has been validated by simulation using ten vehicles and experimentally on two different setups-a laboratory setup comprising five Pioneer 3DX vehicles and by two state-of-the-art autonomous forklifts in industrial-like operating conditions.

Bell-shaped potential functions for multi-agent formation control in cluttered environment

In this paper we analyze stability properties of multi-agent control system in a cluttered environment with an artificial potential based on bell-shaped functions. In our approach attractive and repulsive forces created by potential gradient have the same form which allows definition of target formation that is parameter invariant. Due to the fact that agents are identical, the proposed structure of formation potential is invariant to the interchange of agents configurations, hence, target in which particular agent would eventually end up, depends only on formation initial condition and environment structure (obstacles). We show that position of unwanted stable equilibria can be controlled by parameters that define elementary potential functions. This fact has been used for synthesis of an adaptation algorithm, such that arrival of agents at required formation is guarantied. Simulation results, presented at the end of the paper, confirm correctness of the proposed control scheme.

Control system for reactor vessel inspection manipulator

In this paper a system for control and 3D visualization of a manipulator for weld inspection of nuclear reactor vessels is described. Based on a client-server TCP/IP software architecture, the presented control system enables an operator to perform the entire inspection procedure remotely over a network, avoiding exposure to dangerous radiation which is commonly present in nuclear reactor environments. The developed graphical user interface provides all necessary tools needed for planning robot scan trajectories, their verification on a virtual 3D model and execution on a remote robot. In addition, the weld inspection process can be observed in parallel on a virtual robot and reactor vessel model and on live video streams captured by two special cameras mounted on the robot.

Dual camera surveillance system for control and alarm generation in security applications

In this paper we present an integrated system for intelligent video surveillance, control and alarm generation in security applications related to protection of public buildings (e.g. various financial institutions). By using only two networked cameras, video information is collected, dispatched via network and processed on-line with a group of integrated image processing algorithms able to detect humans in motion, track their motion, and check the visibility of their faces while entering the building. In addition, the developed system counts peoplepsilas traffic and keeps the record of a number of people in the protected area. The integration of given algorithms is made in order to raise the reliability of the threat recognition. The emphasis is on the fast detection of the invisible (masked) face of the approaching person. Based on the outputs of the algorithms, either alarm generation or adequate control actions may take place.

Fast visual tracking and localization in multi-agent systems

In this paper an implementation of an algorithm for fast visual tracking and localization of mobile agents has been described. Based on an extremely rapid method for visual detection of an object, described localization strategy provides a real time solution suitable for the design of multi-agent control schemes. The agents tracking and localization is carried out through five differently trained cascades of classifiers that process images captured by cameras mounted on agents. In this way, each agent is able to determine relative positions and orientations of all other agents performing tasks in its field of view. The described localization method is suitable for applications involving robot formations. Performance of the proposed method has been demonstrated on a laboratory setup composed of two mobile robot platforms.

An internet-based system for remote planning and execution of SCARA robot trajectories

In this paper we describe an Internet accessible robot control laboratory, providing remote trajectory planning and execution for a SCARA robot. The laboratory provides students with hands-on experimental experience with a robotic manipulator. The system is based on client-server TCP/IP architecture. The server-side system, running on an ultimodule embedded platform, controls the 4DOF SCARA robot motion. A PC-based client application enables users to plan trajectories and download them to the motion controller. Trajectory execution can be observed in parallel on a virtual robot model and a camera video stream capturing robot motion.

A Low Cost Vision Based Localization System Using Fiducial Markers

Abstract This paper investigates a mobile robot self-localization system based on fiducial markers which are placed on the ceiling. Recently there have been many articles related to path planning and coordination of mobile agents within an unknown environment. These algorithms demand dedicated (and often expensive) hardware that is capable of handling complex tasks in real time. In this paper, we have explored the possibility to realize an inexpensive and simple navigation system, based on passive fiducial markers, which are able to guide an autonomous mobile robot along a predefined path. Fiducial markers provide not only improved performance in runtime, but also much better identification and localization. Marker design based on circle shape is presented. Using a low-cost webcam and appropriate marker detection algorithm three features are determined: robot position, new movement direction and marker ID. Experimental results are presented at the end of the paper.

Harmonization of Research and Development Activities towards Standardization in the Automated Warehousing Systems

In this chapter, we describe some ideas of robotic system standardization based on ongoing research and development processes in a European FP7 project named EC-SAFEMOBIL, which is focused on estimation and control technologies for safe, wireless, high-mobility cooperative systems. Strongly influenced by the European Commission, demand has been to commercialize as many project results as possible, EC-SAFEMOBIL researchers and developers needed some standards to follow for the main project application areas—unmanned aerial systems (UAS) and automated warehousing systems (AWS). Although many aspects of UAS are covered by adequate standards, this does not hold true for automated warehouses. In the given analysis of possible standardization of automated warehousing systems, we elaborate on ideas on how to overcome evident gaps between academic achievements and viable industry practice. Paying particular attention to process and development standards, as well as function-specific standards, we describe our view of reaching new standards in automated warehousing systems, particularly with a number of deployed automated guided vehicles (AGVs). This involves adopting or extending existing standards from other application areas (UAS), creating new ones, and defining standard benchmark tests. We have proposed a few benchmark scenarios for testing two system functionalities—marker-less indoor localization and distributed control.