Proportional, integral and derivative terms combine to reduce error and improve response.
u=K_p e+K_i∫e dt+K_d de/dt (or K_p(1+1/(T_i s)+T_d s)). P reduces rise time, I removes steady-state error, D adds damping. Implementation issues: derivative filtering, anti-windup, bumpless transfer, setpoint weighting. PID handles >90% of industrial loops.
A temperature loop uses PI control; a servo uses PID.
PID control is the most widely used controller, so knowing what each term does helps you tune and troubleshoot almost any loop.
Proportional, integral and derivative terms combine to reduce error and improve response.
PID control is the most widely used controller, so knowing what each term does helps you tune and troubleshoot almost any loop.
It responds to the present error, giving a quick correction that is proportional to the error size.
It responds to how fast the error changes, which damps overshoot but amplifies noise, so filtering is often used.
Typical applications include holding the temperature of an oven with a PID controller, controlling the position of a motor with a PID loop and keeping the level of a tank steady with a PID controller.
Study "Nyquist stability criterion" first (topic 55 of 101 in Signals, Control & Comms). It covers the groundwork this topic builds on.
Parallel and ideal forms. Integral windup. Derivative kick.
A temperature loop uses PI control; a servo uses PID.
The next topic is "PID tuning", which builds directly on this one.
It is classed as Intermediate in Signals, Control & Comms (topic 56 of 101). It is an intermediate topic. Work through the beginner topics in Signals, Control & Comms first.
Want to practise? Open the interactive course for quick checks, quizzes, simulations and progress tracking.