Run-Time Assurance: A Rising Technology

Run-Time Assurance (RTA) is a control architecture wherein a complex or nondeterministic controller operates freely under the supervision of a monitor that may transfer control away from the complex controller to a simpler, more trusted controller any time system behavior exceeds some pre-defined boundary. Based on the simplex architecture advocated by Sha in 2001, the use of such a scheme was intended to improve system reliability and lower software development cost. Research into the use of similar structures has continued up to the present day, fueling a minor movement seeking an alternative means of compliance for complex and nondeterministic avionics. To date, no comprehensive literature review has appeared to document the rise of this architecture. Applications are varied inside the avionics field and beyond, including topics such as satellite orientation, turbofan engine control, small unmanned aircraft, and ground-based vehicles. Many recent papers are discussed in this work in terms of their applications and their specific contributions to the growing body of work in the field of RTA.