19 Facts About PID controller

Proportional–integral–derivative controller is a control loop mechanism employing feedback that is widely used in industrial control systems and a variety of other applications requiring continuously modulated control.

In practical terms, PID automatically applies an accurate and responsive correction to a control function.

Today the PID controller concept is used universally in applications requiring accurate and optimized automatic control.

The response of the PID controller can be described in terms of its responsiveness to an error, the degree to which the system overshoots a setpoint, and the degree of any system oscillation.

PID controller explored the mathematical basis for control stability, and progressed a good way towards a solution, but made an appeal for mathematicians to examine the problem.

PID controller noted the helmsman steered the ship based not only on the current course error but on past error, as well as the current rate of change; this was then given a mathematical treatment by Minorsky.

PID controller's goal was stability, not general control, which simplified the problem significantly.

Independently, Clesson E Mason of the Foxboro Company in 1930 invented a wide-band pneumatic PID controller by combining the nozzle and flapper high-gain pneumatic amplifier, which had been invented in 1914, with negative feedback from the PID controller output.

The result was the "Stabilog" PID controller which gave both proportional and integral functions using feedback bellows.

The integral in a PID controller is the sum of the instantaneous error over time and gives the accumulated offset that should have been corrected previously.

Mathematical PID controller loop tuning induces an impulse in the system and then uses the controlled system's frequency response to design the PID controller loop values.

Advances in automated PID controller loop tuning software deliver algorithms for tuning PID controller Loops in a dynamic or non-steady state scenario.

The fundamental difficulty with PID controller control is that it is a feedback control system, with constant parameters, and no direct knowledge of the process, and thus overall performance is reactive and a compromise.

Example, a PID controller loop is used to control the temperature of an electric resistance furnace where the system has stabilized.

The integral function of the PID controller tends to compensate for error by introducing another error in the positive direction.

PI PID controller can be modelled easily in software such as Simulink or Xcos using a "flow chart" box involving Laplace operators:.

The PID controller primarily has to compensate for whatever difference or error remains between the setpoint and the system response to the open-loop control.

The error term of this PID controller is the difference between the desired bath temperature and measured temperature.

Each PID controller can be tuned to match the physics of the system it controls – heat transfer and thermal mass of the whole tank or of just the heater – giving better total response.