Development of a completely decentralized control system for modular continuous conveyors

Contents

1. Introduction

1.1 Motivation

1.2 Aim of the dissertation

1.3 Structure of the dissertation

2. Centralized material flow controls

2.1 Classification of material flow controls

2.1.1 Control concepts

2.1.2 Structure of the control systems

2.1.3 Signal processing

2.2 Tasks of the control levels in the material flow automation

2.3 Operating method of conventional PLC controls

2.3.1 Field of application of a PLC

2.3.2 Structure of a PLC

2.3.3 Programming languages

2.3.4 Operating concepts

2.3.5 PLC networks

2.3.6 Limits of and alternatives to centralized controls for material flow systems

3. Decentralized control systems

3.1 Definition of the term ”decentralized” in material flow

3.2 Research projects in decentralized material flow controls

3.2.1 The Internet of Things

3.2.2 MATVAR

3.2.3 Transport system in analogy to routing in data networks

3.2.4 Need for research to achieve complete decentralization

3.3 Decentralized control of IT networks

3.3.1 The OSI reference model

3.3.2 LAN technology

3.3.3 Transport protocol

3.3.4 Routing in networks

3.3.5 Decentrally controlled information vs. material flows

4. Completely decentralized autonomic continuous conveyor system

4.1 Overview and general assumptions

4.1.1 Requirements for a completely decentralized system

4.1.2 Determination of the physical features

4.1.3 Application example

4.2 Control concept

4.2.1 Decentralized generation of topological information

4.2.2 Identification of the conveyor unit

4.2.3 Routing and route reservation

4.2.4 Transportation of conveyor units

4.2.5 Deadlock avoidance

4.3 Throughput analysis

4.3.1 Simulation environment

4.3.2 Throughput calculation

4.3.3 Topology analysis

4.4 Throughput regulation

4.5 Interfaces to the environment

5. Technical implementation

5.1 Introduction of the ”Flexconveyor”

5.2 Construction

5.2.1 Base plate with lifting mechanism

5.2.2 Diverter with integrated RFID antenna

5.2.3 Roller arrangement and sensor system

5.3 Control of the Flexconveyor

5.3.1 Electrical connection

5.3.2 Control procedure

5.4 Connection of several modules to the topology

6. Summary

Research Objectives and Themes

The dissertation aims to establish a foundation for highly flexible material flow systems by developing a completely decentralized control system that allows modules to operate autonomously without central infrastructure. The work focuses on increasing layout flexibility and system adaptability through modular, intelligent conveyor components.

• Decentralized control architectures in material flow systems.
• Technical implementation of modular, autonomous conveyor components.
• Throughput analysis and deadlock prevention in distributed systems.
• Application of IT-inspired routing mechanisms to physical conveyor systems.

Excerpt from the Book

Summary of Chapters

1. Introduction: Outlines the motivation for flexible material flow systems driven by e-commerce and globalization, defining the dissertation's aim to develop a decentralized control architecture.

2. Centralized material flow controls: Reviews conventional centralized control methods like PLC controls and identifies their limitations in terms of flexibility and adaptability.

3. Decentralized control systems: Analyzes existing research on decentralization, including the "Internet of Things" and IT networking principles applied to logistics.

4. Completely decentralized autonomic continuous conveyor system: Describes the development of an autonomous, decentralized conveyor system, including control concepts, deadlock avoidance, and throughput analysis.

5. Technical implementation: Details the mechanical and electrical construction of the "Flexconveyor" prototype, focusing on modules with integrated control and sensing capabilities.

6. Summary: Concludes with an assessment of the achieved flexibility and discusses future steps toward the industrial application of the decentralized system.

Keywords

Material flow systems, Decentralized control, Autonomous conveyor modules, Intralogistics, Throughput analysis, Deadlock avoidance, RFID, Routing protocols, Modular automation, Flexconveyor, Distributed systems, Industrial Ethernet, Network topology, PLC, Supply chain flexibility.

Frequently Asked Questions

What is the core focus of this research?

This work focuses on designing a completely decentralized control system for modular continuous conveyor systems to increase flexibility and reduce the need for central infrastructure.

What are the primary challenges in material flow systems today?

Challenges include shorter project durations, smaller batch sizes, and the need for higher flexibility to adapt to rapidly changing production environments.

What is the main objective of the proposed control system?

The primary goal is to enable conveyor modules to act autonomously, managing their own routing, identification, and collision avoidance without relying on a central computer.

What methodology is used to develop the control system?

The research uses simulation techniques to test control algorithms and draws inspiration from IT network routing protocols to achieve decentralized material flow management.

What topics are covered in the main section of the dissertation?

The main part covers the requirements for decentralized systems, the control concept, routing algorithms, deadlock avoidance strategies, and a throughput analysis for different topologies.

What defines the proposed control system?

It is characterized by high autonomy, distributed decision-making, and the capability of modules to automatically generate topological information and perform routing tasks.

How are deadlocks handled in this decentralized architecture?

Deadlocks are managed through a "deadlock token" process, where modules verify the route reservation for a conveyor unit across the entire path to ensure circular waiting conditions are prevented.

What is a "cross deadlock" and how is it addressed?

A cross deadlock occurs when multiple circular layouts are interconnected. It is mitigated by self-diagnostic tokens that allow modules to recognize their role as links between circles and apply specific safety checks.

What is the role of the "Flexconveyor" module?

The Flexconveyor is the physical prototype developed in this work; it integrates motors, sensors, and RFID technology to demonstrate the practical viability of the decentralized control logic.