IEC 61508 Techniques & Measures for EMI Risk Reduction: EMI detectors as a warning system?

IEC 61508 is the central standard for functional safety. It proposes many hardening techniques and measures to increase safety. Previous studies of electromagnetic interference (EMI) have emphasized the necessity for electromagnetic resilience, which includes EMI-hardening based on EMI detection. In this PhD, the focus is primarily on the development and evaluation of EMI detectors for wired communication channels that will help to reduce the risk of fatal errors due to electromagnetic disturbances (EMDs). The detector should react to unwanted EMDs and notify the control unit, or  the person handling the electronic device, to follow a precautionary procedure  and reduce the risks related to EMI. This should make the system "EMI-hardened by design" and, hence, inherently resilient to EMI.

In this PhD five designs of EMI detector  are presented, including the Adder & Subtractor (A&S) EMI detector, the Field Probe (FP) EMI detector, the Field Probe and Adder & Subtractor (FPAS) EMI detector, the Advanced EMI detector, and the Single Line (SL) EMI detector. Each design introduces improvements primarily aimed at increasing safety while minimizing the need for supplementary hardware. The proposed detectors are evaluated using various analyses based on a theoretical design, a Monte Carlo simulation framework, a mathematical model, and a hardware design. The main objective of these analyses is to determine whether the EMI detector under test can detect a bit error due to an EMD while simultaneously ensuring that it does not compromise the system's availability. Furthermore, new EMD condition assessment definitions are proposed and used to analyze the performance of the EMI detectors from the systems' perspective. The performance of these detectors is also compared with previously published technologies.

The A&S EMI detector, based on the previously proposed comparator-based EMI detector, uses two data-transmission lines to transmit inverted data, followed by re-inversion of the data from one line and subsequent comparison. Unlike its predecessor, the A&S EMI detector analyzes the received signal through addition and subtraction operations, subsequent removal of the constant DC component, and rectification. Results demonstrate that the A&S EMI detector outperforms the performance of the comparator-based EMI detector. However, it still fails in some cases, notably when the EMD frequency is an integer multiple of the EMI detector's sampling rate.

The FP EMI detector utilizes fast field probes to analyze the electromagnetic fields. It uses field strength as a metric to determine whether an EMD is  enough to disrupt the transmitted data. Despite its effectiveness in detecting bit errors due to EMI in all tested scenarios, the FP EMI detector compromises availability. Therefore, the FPAS EMI detector is proposed as a hybrid design that merges the A&S and FP EMI detectors. It addresses this shortcoming of the FP EMI detector by offering improved availability while maintaining detection capabilities for all the tested scenarios. However, for both the FP and FPAS EMI detectors, the placement of fast field probes poses a significant challenge, especially for electrically long-wired communication channels.

To  overcome the shortcomings of the A&S EMI detector without utilizing fast field probes, the Advanced EMI detector is proposed. It also employs a pair of data transmission lines to transmit inverted data. However, it adds the signals from the receiver end of both data transmission lines, followed by a phase shift to one channel. The results demonstrate that the Advanced EMI detector can detect bit errors caused by EMI in closely coupled data-transmission lines. However, it can fail when an EMD induces a voltage with a significant phase difference between the data-transmission lines.

The proposed EMI detectors employ multiple data-transmission lines or additional field probes to effectively detect bit errors caused by EMDs. Therefore, the focus was on designing an EMI detector that utilizes a single data-transmission line. The SL EMI detector is proposed in this regard as a groundbreaking design that can identify EMD induced bit errors without the requirement for a redundant data transmission channel. The SL EMI detector effectively detects EMI in all the tested cases, subjected to hardware limitations to process higher frequencies. Therefore, this design can help in developing wired communication channels that are electromagnetically resilient by design.

This manuscript presents a comprehensive research study on the development and evaluation of EMI detectors. The results obtained from this study offer unique insights into the functionality of EMI detectors and their potential to enhance the safety of wired communication systems. This manuscript serves as a proof of concept of EMI detectors, presenting a compelling case for their broader adoption in safety-critical applications. Additionally, the valorization plan outlined in the thesis includes a roadmap for effectively disseminating and utilizing the research findings. This will enable industries to consider EMI detectors as an appropriate measure to ensure the reliable and secure operation of their safety-critical systems.