J
jeremy
16 minutes
What Good PID Tuning Looks Like
A well tuned loop does four things. It reaches a new setpoint quickly. It goes past the setpoint only a little, or not at all; going past is called overshoot. It holds the setpoint when something outside pushes on it, like a door opening on an oven. And its output stays calm, so the actuator is not worn out by constant jumps. These goals pull against each other. A faster rise usually brings more overshoot. A stronger hold against upsets usually means a busier output. So there is no single best tuning. There is only the right one for the job. A reflow oven may need no overshoot at all. A drone needs speed and can accept a little ringing. A tank level may be fine if it drifts slowly. Before you tune, write down what matters most for your loop. Then judge each test against that list, not against how pretty the curve looks. Run both a setpoint step and an upset, because a loop can look great on one and poor on the other. If no tuning meets your list, the cause may be the process, such as a long delay or a sticky valve, not the gains. After this Concept you can write the goals for your loop and judge a trend chart against them.