Hartmut Ludwig

High Communication Throughput and Low Scan Cycle Time with Multi/Many-Core Programmable Logic Controllers

Programmable logic controllers (PLCs) are hard real-time embedded systems designed to interact with (through sensors and actuators) and control physical processes in pharmaceutical, manufacturing, energy, and automotive industries. PLCs are the fundamental building blocks in modern industrial automation systems; they are designed to operate in extreme, harsh environments for decades without interruption. This letter presents and evaluates a novel, scalable hardware/software architecture for multi/many-core PLCs capable of pipelining the “sensing-executing-actuating” stages of a control system and thus reducing the scan cycle time (SCT) and maintaining a high-throughput communication (HTC). SCT and HTC are two of the most important key performance indicators (KPIs) in industrial control systems because they determine the accuracy of the control algorithms.

Managing residential-level EV charging using network-as-automation platform (NAP) technology

The amount of power that can be provided for charging the batteries of the electric vehicles connected to a single neighborhood step-down transformer is constrained by the infrastructure. This paper presents a distributed and collaborative residential-level power grid management application to alleviate the need of costly infrastructure upgrade. The application is designed to be hosted in our in-house developed network-as-automation platform (NAP) technology where most of the control functionalities may be moved onto the networking devices. Moreover, we have adapted a service-oriented software engineering principle to achieve scalability, autonomous, and architecture agnostic properties for the residential-level EV charging. We demonstrate a functional prototype where off-the-shelf networking devices capable to host a Linux Operating system are used to showcase the NAP technology. Furthermore, we developed a web-based user interface that may be accessible from any standard computing device, e.g. iPhone, to monitor the runtime operation of this application.

Pipelining for cyclic control systems

This paper presents a novel pipelining technique designed specifically to improve the execution of cyclic control systems and applications in terms of scan cycle time reduction and/or execution of additional workload. Based on the observation that cyclic control systems are tightly coupled with physical processes and that state information (e.g. on/off signals, temperature, pressure) is the most critical data in an application, we present new execution schemes that overlap the execution of multiple cycles in multi-core processors over time. Using an edge detection application benchmark and a software real-time PLC (Programmable Logic Controller) implementation on a quad-core processor, we validate our pipelining method and show the performance scalability of the various schemes. Additionally, we analyze the resilience of our pipelining approach to time delays and propose a speculative execution method to deal with data dependency violations.