robodatech.P · Respond to error
Proportional gain increases effort when error grows. Low gain is gentle but slow; excessive gain can excite oscillation in a real mechanism with delay or inertia.
Control
Make motion follow a target.
Learn error, feedback, proportional control, integral action, derivative damping, and the practical limits of a real robot.
Try it yourselfChange an input.
Change an input.
See what follows.
A simplified learning model. Values describe the model, not a connected robot.
Close the loop around something you can measure.
An open-loop command asks for effort, such as a PWM duty cycle. A closed-loop controller measures the result, compares it with a target, and adjusts the effort. For wheel speed, an encoder supplies feedback; for a joint, use an appropriate angle sensor. Position, speed, and current are different quantities and need distinct units and limits.
e = target − measurement
u = Kp·e + Ki·∫e dt + Kd·de/dt
u = Kp·e + Ki·∫e dt + Kd·de/dt
Understand each term
I · Remove persistent error
Integral action accumulates error to compensate for constant loads. Clamp or condition the integral when the actuator saturates so it does not keep winding up.
D · Dampen rapid change
Derivative action reacts to the rate of change. It is sensitive to noisy measurements, so filtering and derivative-on-measurement are common practical choices.
Read this model correctly
The experiment uses only proportional control on the normalized first-order plant dy/dt = −y + u, with u = Kp(1 − y). Its exact response is y(t) = Kp/(1 + Kp) × (1 − exp(−(1 + Kp)t)). A gain of 2 settles at 2/3 of the target; a gain of 0 produces no motion. This deliberately simple model has no delay, saturation, noise, or oscillatory dynamics and cannot predict whether your physical robot is stable.
Tune on the real mechanism
- Verify sensor polarity, units, and update period with the actuator disabled.
- Set conservative output and speed limits. Begin with I and D at zero.
- Increase P gradually while logging target, measurement, error, and output.
- Add a small integral term only when persistent error needs correction; implement anti-windup.
- Add filtered damping when required, then retest under different loads.
- Test sensor loss, stale commands, saturation, and recovery before normal operation.
A network connection should not be the only way to stop an actuator. Keep local watchdog and driver-disable behavior independent of high-level planning.
Go to the source
Manufacturer and project documentation. Reviewed 20 September 2026; check your exact board revision and software release.