Loop
Feedback control loop
You might say: servo loop, closed loop
A closed loop measures the robot, compares the measurement with a target, computes a correction, commands an actuator, and measures again.
- What it does
- It rejects errors and disturbances by feeding the measured result back to the controller.
- Ask
- What bandwidth, delay and stability margin remain?
What to look for
- Target compared with measurement
- Repeated measurement after the command
Parts
- PID controller: A PID law combines proportional error, accumulated error and error-rate terms into a command.
- Control rate: Control rate is the number of control updates made each second.
- Tracking error: Tracking error is the difference between the desired motion and the measured motion over time.
Loop: balancing
PID controller → Motor driver → Electric motor → Encoder → Tracking error ↺
Pattern
Negative feedback (thermostat)
Sources
- Kevin M. Lynch and Frank C. Park, Modern Robotics: Mechanics, Planning, and Control, Ch. 8 §8.9
The amplifier uses a local feedback control loop to adjust the time-averaged voltage across the motor to achieve the desired current.
Use it on your project
teardown-apply: hold "Feedback control loop" (control-loop) from the teardown at https://teardownatlas.com/robotics/ against my project
Paste it into a coding agent that has the teardown skills.
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