Resilient control systems

A resilient control system is one that maintains state awareness and an accepted level of operational normalcy in response to disturbances, including threats of an unexpected and malicious nature".

[2] This ease of readily adding sensors and logic through software, which was once done with relays and isolated analog instruments, has led to wide acceptance and integration of these systems in all industries.

[1] From a philosophical standpoint, advancing the area of resilient control systems requires a definition, metrics and consideration of the challenges and associated disciplinary fusion to address.

Organizational resilience considers the ability of an organization to adapt and survive in the face of threats, including the prevention or mitigation of unsafe, hazardous or compromising conditions that threaten its very existence.

[9] However, based upon the application of control dynamics to industrial processes, functionality and determinism are primary considerations that are not captured by the traditional objectives of information technology.

The consideration of the malicious actor and cyber security are not directly considered, which might suggest the definition, "an effective reconstitution of control under attack from intelligent adversaries," which was proposed.

[14] Considering the rubber ball in terms of a system, resilience could then be defined as its ability to maintain a desired level of performance or normalcy without irrecoverable consequences.

While resilience in this context is based upon the yield strength of the ball, control systems require an interaction with the environment, namely the sensors, valves, pumps that make up the industrial operation.

At the center, an understanding of performance and priority provide the basis for an appropriate response by a combination of human and automation, embedded within a multi-agent, semi-autonomous framework.

[19][20][21] These cyber-physical tenants complement the fundamental concept of dependable or reliable computing by characterizing resilience in regard to control system concerns, including design considerations that provide a level of understanding and assurance in the safe and secure operation of an industrial facility.

[23][24] Considering control system design and interaction, the goal would be to tailor the amount of automation necessary to achieve some level of optimal resilience for this mixed initiative response.

Therefore, in considering resilient control system architecture, atypical designs that imbed active and passively implemented randomization of attributes, would be suggested to reduce this advantage.

In moving to a smart grid, the complex interconnected nature of individual homes, commercial facilities and diverse power generation and storage creates an opportunity and a challenge to ensuring that the resulting system is more resilient to threats.

[40] 2) As our society becomes more automated for a variety of drivers, including energy efficiency, the need to implement ever more effective control algorithms naturally follow.

However, advanced control algorithms are dependent upon data from multiple sensors to predict the behaviors of the industrial operation and make corrective responses.

This type of system can become very brittle, insofar as any unrecognized degradation in the sensor itself can lead to incorrect responses by the control algorithm and potentially a worsened condition relative to the desired operation for the industrial facility.

Addressing this need, a semester course in resilient control systems was established over a decade ago at Idaho and other universities as a catalogue or special topics focus for undergraduate and graduate students.

[45] However, developing a level of effectiveness can be time-consuming, and when done in a professional environment can expend a lot of energy and time that provides little obvious benefit to the desired outcome.

It is clear that the earlier these STEM disciplines can be successfully integrated, the more effective they are at recognizing each other's contributions and working together to achieve a common set of goals in the professional world.

Team competition at venues such as Resilience Week will be a natural outcome of developing such an environment, allowing interdisciplinary participation and providing an exciting challenge to motivate students to pursue a STEM education.

Standards and policy that define resilience nomenclature and metrics are needed to establish a value proposition for investment, which includes government, academia and industry.

Fig. 1. Resilient Control System Design and Metrics Philosophy.
Fig. 2. Resilient Control System Framework.
Fig. 3. Resilience Base Metrics.
Fig. 4. Resilience Manifold for MDS.