Control Frequency

How many times per second a controller sends out commands, in Hz; its reciprocal is the control period.

Control frequency is how many times per second a controller completes the loop of reading sensors, computing, and sending a command, measured in hertz (Hz); its reciprocal is the control period — 1 kHz, for instance, means once every 1 millisecond. Robots typically nest several such loops, running faster the closer they are to the motor: a large model or VLA policy might output actions a few to a few dozen times per second, joint position or torque loops run at hundreds to a few thousand hertz, and the current loop inside a motor driver runs faster still. Too low a frequency makes the robot slow to react to disturbances, risking shaking or falling; too high a frequency can outrun the available compute or communication bandwidth, so commands that aren't computed in time get rejected or throw an error. It's related to but distinct from “policy inference frequency” and “control latency”: the former measures only how fast the model produces a result, while the latter measures the full time from sensing to the action actually taking effect. The control frequency used in simulation training has to match the real robot, or the sim-to-real gap widens.

ExampleFranka's arm runs its FCI interface at 1 kHz: the network round trip, the user's callback computation, and the robot's own processing must together finish within 1 millisecond, or that tick's command gets dropped — and 20 dropped ticks in a row trigger an error stop. A quadruped policy in legged_gym, by contrast, runs at 50 Hz, producing a new action every 20 milliseconds.

Also called

Control Rate, Control Period, Control Cycle

Related

Policy Inference Frequency · Control Latency · Control Decimation · Real-Time Control · Control Bandwidth · Proportional-Derivative Control

Sources

libfranka robot.h（Since the robot is controlled with a 1 kHz frequency…）
Franka FCI Docs: Minimum system and network requirements（RTT + 控制回路 + 机器人处理 < 1 ms；连续丢 20 包即停机） (Chinese)
legged_gym: legged_robot_config.py（sim dt = 0.005, decimation = 4）
Figure: Helix（System 1 200 Hz / System 2 7–9 Hz）