Actuator Commissioning and Characterization
Before an actuator can be trusted in a loop, its real response, limits, and quirks must be measured and modeled.
Knowing the actuator
A controller commands an actuator expecting a certain response. If the real response differs from the assumed one in gain, delay, or limits, the loop misbehaves. Actuator commissioning measures the true input-output behavior of each actuator so the control model matches reality before the actuator is placed in a feedback loop.
What is characterized
- Static gain: how much output per unit command
- Dynamic response: delay, rise time, and bandwidth
- Hard limits: maximum output, slew rate, duty cycle
- Nonlinearities: saturation, dead zones, discrete steps
- Cross-effects: what else the actuator disturbs
Methods
Actuators are driven with test waveforms, step changes and swept frequencies, and their response is recorded. Fitting a model to this data yields the parameters the controller and estimator need. For heating and current-drive systems, deposition location is mapped as well, since where the effect lands matters as much as how much.
Feeding the control design
The characterized models update the control-oriented models used for feedforward, estimation, and prediction. An accurately characterized actuator lets feedforward carry more of the load, keeping feedback corrections small. A poorly characterized one forces conservative, feedback-heavy control that risks saturation.
In the Kronos program
For the Hyperion breeder and the burner generators, actuator commissioning covers the poloidal field coils, the central solenoid, heating and current-drive systems, fueling, and the mirror plug coils of the burner. Measured responses refine the shared reduced models used across the flight simulator and digital twin. This characterization is part of the staged commissioning that follows construction.