Proportional, Integral, and Derivative (PID) Controllers

Proportional, Integral, and Derivative (PID) Controllers

  • Proportional, Integral, and Derivative (PID) controllers are commonly used in control systems for feedback mechanisms.
  • They aim to adjust system input based on the error signal from the desired output.
  • The PID controller combines the three fundamental actions of proportional, integral, and derivative controls.

Proportional Control

  • A proportional control adjusts the process input based on the current error magnitude.
  • The component of the PID controller that is proportional provides an output which is directly related to the error magnitude.
  • The value of the proportional response can be adjusted via the proportional gain, known as the P gain.
  • Greater the P gain, the larger the response for a given error.

Integral Control

  • The integral control is based upon both the magnitude and the duration of the error.
  • It accumulates the instantaneous error over time and works to eliminate the offset, which results in the steady-state error.
  • This accumulation results in significant action when the error exists over a long period.
  • The integral term is defined by the integral gain, or I gain.

Derivative Control

  • Derivative control responds to the rate of change of the error with time.
  • It calculates the derivative of the process error and generates an output.
  • This control action allows the controller to anticipate future behaviour of the error based on its current rate of change.
  • The degree of influence is adjusted in the controller through the derivative gain, or D gain.

PID Controller Response

  • The controller output is the sum of the proportional, integral and derivative responses.
  • PID Controllers can be tuned for specific performance by adjusting the P, I and D gains.
  • Optimal tuning of a PID controller can be a complex task as it requires fine adjustments of the P, I, and D gains.

Applications of PID Controllers

  • PID controllers are used in a wide range of applications, from industrial control processes to navigational systems in aircrafts and ships.
  • They are also implemented in temperature control systems, robotics and autonomous vehicles.

Advantages of PID Controllers

  • PID controllers are fundamentally stable and robust with proper tuning.
  • They combine the benefits of better stability (P), steady-state response (I), and responsiveness to sudden changes (D).
  • PID controllers are versatile and can be used in simple and complex systems.

Disadvantages of PID Controllers

  • PID Controllers can be difficult to tune accurately, especially in systems with nonlinear or complex dynamics.
  • They might respond too aggressively to sudden changes if not appropriately tuned, leading to overshoot.
  • PID controllers may not be the best choice for systems with significant time delay or multiple input, multiple output (MIMO) Ssystems.