ELEC 251 Lecture Notes - Lecture 2: Industrial Control System, Process Variable, Control Variable
Document Summary
The process of observing a parameter, comparing it against a desired value, and the action to bring the parameter as close as possible to the desired value. Automatic controls are designed to handle dynamic situations where there are unplanned changes. Different types of control actions: reverse and direct actions. Few parameters are common for each control system: setpoint (sp, error, offset, setpoint (sp) the desired value at which the process should be controlled. It is used by the controller as a reference for comparison with the process variable. (temperature or pressure setting, speed or position setting etc. : error the difference between the process variable and the setpoint. Controllers use the error to calculate the output to a final element: offset a steady-state error that is a permanent part of system response, direct action the controller output increases with an increase in the measurement of the pv.
