Plant Control State Machines
A supervisory state machine sequences the whole plant through its operating phases and enforces the conditions required to move between them.
Operation as states
A fusion plant does not run continuously in one mode; it moves through distinct phases: standby, pump-down, magnet energization, plasma initiation, flat-top operation, ramp-down, and shutdown. A supervisory state machine represents these phases as states and defines the transitions between them, so the plant always occupies a well-defined, known condition.
Guarded transitions
Each transition has guard conditions that must be satisfied before it is allowed. Plasma operation is not permitted until vacuum, magnet, cooling, and safety conditions are all met. This structure turns a mass of interlocks into an orderly permission scheme: the plant advances only when it is ready, and any lost condition forces a transition back toward a safe state.
Coordination role
The state machine coordinates subsystems that would otherwise act independently. Entering the energization state tells power supplies to ramp, cryogenics to expect load, and quench protection to arm. Entering ramp-down reverses the sequence in the right order. Subsystems report readiness to the supervisor, which holds a transition until all are ready, preventing out-of-order actions.
- Phases become explicit, well-defined states
- Guard conditions gate every transition
- Lost conditions force a fallback to a safe state
- Supervisor coordinates subsystem readiness
Fault handling
When a fault occurs, the state machine drives the plant to the appropriate safe state, coordinating a controlled plasma termination, magnet dump if needed, and safe parking of utilities. Because the safe state is explicit, the response is predictable rather than improvised. In the Kronos control architecture, described as a design and simulation model, the plant state machine is the top layer that ties component control, interlocks, and scenarios together.
A clear state machine is what turns many subsystems into one coherently operated plant.