RESET (INTEGRAL) CONTROL SYSTEMS
Process Controls
RESET (INTEGRAL) CONTROL SYSTEMS
The output rate of change of an integral controller is dependent on the magnitude
of the input.
EO 1.4
DESCRIBE the characteristics of the following types of
automatic control systems:
c.
Integral control
Reset Control (Integral)
Integral control describes a controller in which the output rate of change is dependent on the
magnitude of the input. Specifically, a smaller amplitude input causes a slower rate of change
of the output. This controller is called an integral controller because it approximates the
mathematical function of integration. The integral control method is also known as reset control.
Definition of Integral Control
A device that performs the mathematical function of integration is called an integrator. The
mathematical result of integration is called the integral. The integrator provides a linear output
with a rate of change that is directly related to the amplitude of the step change input and a
constant that specifies the function of integration.
For the example shown in Figure 19, the step change has an amplitude of 10%, and the constant
of the integrator causes the output to change 0.2% per second for each 1% of the input.
The integrator acts to transform the step change into a gradually changing signal. As you can
see, the input amplitude is repeated in the output every 5 seconds. As long as the input remains
constant at 10%, the output will continue to ramp up every 5 seconds until the integrator
saturates.
IC-07
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