A criterion for guaranteed closed loop simulation stability

The general problem of closed loop real-time simulation is discussed. It is shown that the simulation must be designed not only for the open-loop system but also for the controller in the loop in order to maintain stability while still allowing for a maximal time step. Several methods of guaranteeing closed-loop stability for a simulated system with hardware in the loop are discussed. No one method is claimed to be the solution to the general problem of closed-loop simulation stability. Rather, they are intended to serve as additional tools for the simulation engineer