Zero-order hold is a method of reconstructing a continuous analog signal from a discrete digital one. In a robotic control loop, the digital-to-analog converter samples a command value and holds that exact voltage steady until the next clock cycle. This creates a staircase-like signal that drives the motor amplifiers, introducing a slight delay that engineers must account for when tuning high-frequency servo loops.
Heard on the job
If you model the plant without including the ZOH delay, your simulated step response will look much cleaner than the real hardware.
Insider tip
The ZOH inherently introduces a phase lag of half the sampling period, which can eat into your phase margin and destabilize an aggressively tuned PID controller.
Also heard as
- zero-order hold