Real-time exception handling—Use cases and response requirements

Adequate real-time event detection and exception handling for machine protection and plasma optimization are important for safe and efficient operation of fusion devices. Within the scope of a layered protection hierarchy, the exception handling goals of the real-time control system are to optimize control performance, switch to alternate investigations, terminate the discharge in a controlled way, or alarm the interlock system when control is lost. Analysis of these goals shows that they can be implemented with two methods: the modification of the reference values to respond to degradation of sensors, actuators or controllers, and the replacement of schedules to perform other investigations, which includes controlled termination and interlock alarm cases. In support of these methods the sensor and evaluated data quality and the time-varying actuator characteristics and capacity must be communicated to users of those information to avoid failure propagation.