Application of a Robust Control Algorithm for Satellite Cyber-Security and System Resilience

A unique model-reference-based control system architecture has been devised that greatly improves a closed-loop control system's ability to function in the event of a malfunction, including malicious intervention. This architecture, called the ICAR (Integral Command Augmentation for Robustness) loop, was first applied to make missile autopilots more robust to unanticipated changes and disturbances. The ICAR loop, which features a feedforward/feedback topology, monitors the system and corrects the control signal to the system, if necessary. The ICAR loop has the important characteristic that it is totally transparent in normal operation and does not alter the performance of the in-place control system. It only becomes active when the system being controlled changes and/or its operation deviates from its intended transient response. The ICAR loop generates a signal to restore the system response to its originally intended character. The novel idea of this paper is to exploit the robustness feature of the ICAR loop as a diagnostic and system-resilience mechanism for satellite cyber-security. The ICAR loop can be implemented as a standalone device. This makes it particularly easy to implement it as a completely separate and independent computing unit. This idea could further extended to implement the ICAR loop as an analog device thus overcoming total dependence on digital monitoring and protection technologies. ICAR loop application with a satellite attitude control system is shown in a series of operational examples. For a hypothetical satellite, different malfunction scenarios are presented encompassing a variety of ways that computation-related processes can fail due to cyber-attack and the ICAR loop's remedial role. The ICAR loop's powerful capability to successfully provide a detection and operational resilience capability is demonstrated. The malfunctions considered span a range of origin and illustrate the ICAR loop's ability to defend against disturbances caused by cyber-attack.