Supervisory Control and State Machines

The supervisor sequences discharge phases, enables and disables controllers, and holds the logic that ties fast loops into one discharge.

The conductor of the orchestra

Individual feedback loops each do one job. The supervisor is the layer that decides which loops run when, sets their references from the pulse schedule, arbitrates shared actuators, and moves the discharge through its phases. It is the logic that turns a collection of controllers into a coherent discharge.

State machines

Supervisory logic is naturally expressed as a state machine: the discharge is in a state such as breakdown, ramp-up, flat-top, or ramp-down, and transitions happen when conditions are met. Each state enables a specific set of controllers and limits. State machines are used because they are explicit, testable, and easy to reason about in fault conditions.

Event-driven transitions

Transitions can be time-based or event-based. An event-based transition, such as entering flat-top when the target current is reached, makes the discharge adapt to reality rather than a fixed clock. Off-normal events also drive transitions, moving the machine into a recovery or termination state when a fault is detected.

Arbitration

When controllers request the same actuator, the supervisor decides who wins using the priority order. It also enforces mutual exclusion where two controllers must not act at once, and it hands actuators between controllers cleanly so there is no glitch at the transfer.

In the Kronos program

The Hyperion breeder's supervisor sequences the ramp to 9.86 megaamperes, the flat-top at the design operating point, and a controlled ramp-down, while allocating the shared electron cyclotron and beam systems among competing uses. Its state machine also embeds the off-normal transitions. The logic is exercised against normal and fault scenarios in the flight simulator.