On-off control is the simplest form of feedback control where the manipulated variable is driven fully open or closed based on the controlled variable position relative to the setpoint, causing oscillations. A sequential control system processes steps in a predetermined order dependent on defined time-based, external event-based, or combined conditions being satisfied. A PID controller continuously calculates error as the difference between the setpoint and process variable, applying a correction based on proportional, integral, and derivative terms to reduce oscillations.
On-off control is the simplest form of feedback control where the manipulated variable is driven fully open or closed based on the controlled variable position relative to the setpoint, causing oscillations. A sequential control system processes steps in a predetermined order dependent on defined time-based, external event-based, or combined conditions being satisfied. A PID controller continuously calculates error as the difference between the setpoint and process variable, applying a correction based on proportional, integral, and derivative terms to reduce oscillations.
On-off control is the simplest form of feedback control where the manipulated variable is driven fully open or closed based on the controlled variable position relative to the setpoint, causing oscillations. A sequential control system processes steps in a predetermined order dependent on defined time-based, external event-based, or combined conditions being satisfied. A PID controller continuously calculates error as the difference between the setpoint and process variable, applying a correction based on proportional, integral, and derivative terms to reduce oscillations.
On-off control is the simplest form of feedback control where the manipulated variable is driven fully open or closed based on the controlled variable position relative to the setpoint, causing oscillations. A sequential control system processes steps in a predetermined order dependent on defined time-based, external event-based, or combined conditions being satisfied. A PID controller continuously calculates error as the difference between the setpoint and process variable, applying a correction based on proportional, integral, and derivative terms to reduce oscillations.
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On-Off control is the simplest form of feedback control.
An on-off controller simply
drives the manipulated variable from fully closed to fully open depending on the position of the controlled variable relative to the setpoint. Although on-off is a very cheap form of control it is rarely used in process control applications because of the oscillation it causes in the controlled and manipulated variables. In a connected process these oscillations would be propagated right through the system You can turn a controller ON or OFF. For example, the wall thermostat measures a room temperature and compares it to a set temperature (the desired temperature). Then, if the temperature is too high, the thermostat turns the furnace/heater OFF. If the temperature is too low, the thermostat turns the furnace/heater ON. You might make the control effort (the amount of fuel fed to the furnace, for example) proportional to the error (the difference between where you are - the measured temperature - and where you want to be - the desired temperature. And, there are other algorithms that use the error, or some function of the error (like the integral of the error, for example) to calculate the control effort.
Sequential Control System
A control system in which the individual steps are processed in a predetermined order, progression from one sequence step to the next being dependent on defined conditions being satisfied. Such a system may be time-dependent, in which the step transition conditions are functions of time only; on external-event dependent, where the conditions are functions of Input signals only; or combinations of these (and perhaps more complex) conditions. Sequential control may be either to a fixed sequence or to a logical one that will perform different actions depending on various system states. An example of an adjustable but otherwise fixed sequence is a timer on a lawn sprinkler.
A proportionalintegralderivative controller (PID controller) is a control loop
feedback mechanism (controller) commonly used in industrial control systems. A PID controller continuously calculates an error value {\displaystyle e(t)} e(t) as the difference between a desired setpoint and a measured process variable and applies a correction based on proportional, integral, and derivative terms, (sometimes denoted P, I, and D respectively) which give their name to the controller type.
Program control is how a program makes decisions or organizes its activities.
Program control typically involves executing particular code based on the outcome of a prior operation or a user input.