Modern distributed control systems comprise multiple intelligent devices capable of performing complex time and mission-critical tasks both independently of each other or partly jointly with each other. To do so, they strongly depend on an accurate common notion of time as well as a reliable shared communication medium for timely data exchange. Traditional legacy communication technologies (field bus systems) supported time transport to a certain extent or provided at least a common frequency. Due to its numerous undisputed advantages, Ethernet has become the only viable communication medium effectively replacing such systems. Being inherently asynchronous time and frequency transfer has to be accomplished using a packet-based approach when moving to Ethernet. After explaining the basic principles of packet-based time transfer, the most common standards are explained compared with each other with respect to their intended application domains. Special emphasis will be put on the Precision Time Protocol (PTP) as defined in the underlying IEEE 1588 standard and its variant IEEE 802.1AS used for time-sensitive networks. Maintaining a highly accurate common notion of time under all circumstances is a crucial prerequisite for most distributed systems. Although PTP has proven to provide sub-microsecond accuracies, it can cope only with a limited number of error conditions. This paper describes all major sources that can either deteriorate the accuracy or cause a total loss of synchronization altogether. Selected countermeasures and enhancements are presented, which can greatly improve the resilience of PTP against errors as well as malicious attacks. This paper concludes by presenting the selected measurements' results of a novel proposed method.

Network-based clock synchronization is an important prerequisite for many application areas and more and more required for the factory floor for network arbitration, control, and monitoring. Limitations of existing clock synchronization protocols are that they either support high redundancy and robustness or high precision. This paper presents an approach to integrate slave-side robustness into high precision clock synchronization. To achieve this goal, a system design facilitating the IEEE 1588 Precision Time Protocol (PTP) is proposed, which supports multiple masters in parallel and provides highly reliable and robust clock synchronization, while at the same time demanding no changes to the network and timing infrastructure. The slave-side robustness can be further enhanced to provide improved monitoring support for IEEE 1588. This makes the solution especially appealing for large-scale networks where retrofitting must be done efficiently and the network infrastructure is not under the control of the end device operator.

The use of wireless technologies in Factory Automation is attractive due to several advantages (mobility, cost, etc.); however, to satisfy the requirements of industrial applications, they have to be improved in terms of real-time performance. Handover is a particular weakness in cellular wireless systems, e. g., in IEEE 802.11, since it may introduce delay beyond acceptable bounds. The project “flexWARE - Flexible Wireless Automation in Real-Time Environments” aims at implementing such an infrastructure based on IEEE 802.11. To enhance overall system performance, it offers a localisation service. In this paper we present theflexWARE handover mechanism which exploits localisation to reduce the discovery phase. A performance evaluation, based on simulation and empirical measurements, shows that the mechanism results in a seamless handover for a class of industrial applications.

This paper presents a smart capacitive angle sensor suited for automotive and industrial use. To comply with tough constraints of such applications in terms of environmental conditions, unit costs, and physical size, a fully integrated solution is mandatory. However, the limitations and capabilities of a single mixed-signal integrated circuit have considerable impact not only on the hardware architecture of the digital and analog system components, but also on the feasible measurement algorithm. A thorough investigation of all major nonlinear effects leads to an accurate system-level model of the sensor which is used to design a robust and reliable fully integrated sensor system capable of handling signal offset and amplitude variations. In addition, the proposed system recognizes and reacts on electromagnetic disturbances. Measurements taken from a final prototype comply with the simulation results.

This article describes the architecture and implementation of two systems on a chip, which support high accuracy clock synchronization over Ethernet networks. The synchronization is based on the SynUTC technology and on the novel IEEE 1588 standard for a precision clock synchronization protocol for networked measurement and control systems. The network interface node on one hand provides all necessary hardware support to be flexibly used in a broad range of applications. The switch add-on on the other hand accounts for the packet delay uncertainties of Ethernet switches and is crucial for high accuracy clock synchronization.

Today's smart sensors allow for the implementation of ample computing resources to improve their performance without increasing chip area and thus production costs significantly. What makes them more complex and at first sight less robust is in fact also a chance to improve their fault tolerance. In this paper we present a fault analysis for a capacitive angular sensor designed for automotive applications. Based on the assessment of potential faults and effects degrading the performance, we discuss constructive and operative measures and design decisions that have been taken to enhance the robustness of the system. A key component is a self-calibrating carrier frequency measurement principle, which is used to compensate common drift effects as well as to filter out electromagnetic disturbances. Electrical faults can be detected and lead to a fail stop behavior of the system. It is shown how these fault tolerance mechanisms are implemented in both a passive (i.e., by virtue of system design) and active way through appropriate data processing algorithms. The results of the case study are considered typical for capacitive sensors, but seem applicable also to similar problems.

Reliable real time data transmission ought to be able to tolerate both transient faults and line failures. The former are readily dealt with by employing appropriate error control coding, whereas the latter require multiple transmission lines. The conventional approach is to use one active and several standby channels. However, utilizing all available channels through multiple feeding and implementing active redundant receivers allows instantaneous recovery from line failures. We investigate such receiver structures for a data transmission system based on a double-error correcting BCH-code with underlying Manchester line coding and three parallel data links. Different approaches for implementing majority voting strategies are compared with respect to overall error handling capabilities. As a result we will propose an optimal structure called majority Manchester decoder requiring only moderate implementation overhead.