PID control: the P, I and D explained

Lesson notes

Key points

• A PID controller computes its motor command from the error, which is the target value minus the measured value.
• The proportional term pushes harder when the error is large, but alone it often leaves a small steady-state error.
• The integral term adds up past error over time, so it keeps increasing output until that leftover error is removed.
• The derivative term reacts to how fast the error changes, damping the motion so the joint overshoots and oscillates less.

Definitions

Steady-state error

The error that remains after the system settles, when a constant correction is still needed.

Takeaway: P reacts to now, I to the past, D to the trend of the error.

ErrorProportionalIntegralDerivative