Question

What is the problem with proportional control? (Control system, PID controller)

Answer 1

Proportional controller is called as gain controller, where the output position is related to the deviation of the set point and measured control process value. As the name specifies its output will be error deviation multiplied a factor (electronic circuit gain). Proportional controller can be used where the processing time of equipment or process is very large or where error magnitude is not needed to minimize to zero.

With proportional band, the proportional controller output changes in “proportion” to the error between process variable and set point. This controller works purely on existing error signal.So you always need a measurable error signal to generate an effective output signal.

Since proportional control does not incorporate the time that the error has existed, there will always be an offset from set point.

Control systems may also experience changes in setpoint, which are called setpoint load changes. Integrating and nonintegrating processes respond differently to these setpoint load changes under proportional control.