Introduction to the Special Issue on Fault-Resilient Cyber-Physical Systems—Part I

Cyber-Physical Systems (CPS) are increasingly pervasive in modern society due to their growing use in many complex applications of our everyday life, such as autonomous delivery drones and medical robotics. These systems, interacting with the environment, are often mission- or safety-critical systems and must therefore satisfy strict dependability requirements. Such requirements include not only reliability, maintainability, and availability goals but also specific constraints, including performance, power, energy, or timing.

It is arguably crucial for safety-critical CPS to provide dependability against faults incurred by mobile and dynamic physical environments, which is very challenging, especially if fault tolerance is provided at the cost of time and computation. Hardware is getting more and more complex and the semiconductor scaling is pushing toward the smallest size possible, both with the goal to increase the available computational power. These two trends, in addition to the employment of emerging technologies, like non-volatile memory, increase the reliability threats.

Safety-critical hardware struggles to provide sufficient computational capabilities to modern applications, which often need to resort to Commercial Off-The-Shelf (COTS) components rather than specialized and fault-tolerant hardware. Hence, the use of COTS is leading to a shift from fault-tolerance to fault-resilience: the hardware is no longer considered capable of tolerating any fault, thus modern systems need to be designed, at hardware and software levels, in a way that is able to self-recover from errors. Novel techniques, solutions, algorithms, and tools are thus needed to tackle the design and development of CPS that needs to guarantee dependability and safety.

This special issue offers substantial contributions in several fields, with the goal of improving their resilience against faults. To accommodate the numerous submissions, this special issue is divided into two parts. Part I includes eight papers published in this issue, while the remaining papers will be featured in Part II, which will appear in a subsequent issue.

We start the special issue with two articles focusing on Unmanned Aerial Vehicles (UAVs), which has been widely used in mission-critical scenarios without human attendance.

An emerging field where CPS plays a relevant role is the connected vehicle and intersection control where autonomous and timely decisions can improve drivers’ and passengers’ safety. In this field, fault resilience and robustness are critical for ensuring safety.

Fault resilience has also become an increasingly important design consideration for edge computing and Internet of Things, where mission-critical data require resilient and secure storage, communication, and sharing.

We believe this part of the special issue holds value for readers, who are interested in the latest developments in fault-resilient designs for CPS, a topic that is expected to be increasingly relevant for the years to come. Specifically, it focuses on UAVs, autonomous and timely decisions, as well as edge computing and Internet of Things. We extend our sincere gratitude to the reviewers, whose invaluable assessment made this issue possible, and to the editorial team for their guidance and insightful suggestions, without which this endeavor would not have been achievable.