Dynamic control system upgrade using the Simplex architecture

One of the most attractive features of computer-controlled systems should be the ease with which they can be modified to incorporate improvements and new capabilities. It would be desirable to make the software changes in a safe and reliable fashion while the system is running. The Simplex architecture, a real-time software technology developed at the Carnegie Mellon University Software Engineering Institute, is designed for this purpose. We introduce the basic structure of the Simplex architecture and describe the types of faults it can handle. We describe the fault detection mechanism based on the trajectories of the physical system in its state space, and derive the control switching logic that determines which controller is chosen to control the physical system in each sampling period.