**Controller mode** is the way in which a control system issues
orders related to deviation. From the point of view of controlling instruments,
controller mod is a method by which the controller changes its output according
to deviations.

__Controller Modes__

**Controller mode **is the way in which a control system issues orders related to deviation. From the point of view of controlling instruments, controller mod is a method by which the controller changes its output according to deviations.

__Enlist the types of
controller modes__

**ON/OFF Modes****Proportional Modes****Integral Modes****Derivative Modes**

There are four basic modes of this controller. The rest of the mods are made from their combination. Which are as follows.

**Proportional Integral Control Mode (P+I)****Proportional Derivative Control Mode (P+D)****Proportional Integral Derivative Control Mode (P+I+D)**

__ON/OFF Mode/Two Way
Mode/Bang Bang Mode__

**On-off control mode** is a control system in which the final
control element is either on or off. That is, it has only two positions on or off.
Hence it is also called Two Way Control and Bang Bang Control.

__Working Principle__

On-Off control oscillates above and below the controlled variable set point in control mode. That is, the controlled rebel does not reach its set point. This system is not permanent but always oscillating. Input's 100% changes require a 200% change in output. Which reduces the gain of the controller. This is about 0.5. If the pointer is moved from left to right, then a 50% change in input leads to a 100% change in output. In this case, the gain of the controller is higher.

__Proportional Modes__

A mode of the control system in which the percentage change
in the output of the final control element is proportional to the percentage
change in error. This is called **proportional control mode**.

__Integral Control Mode__

**Integral action** is also called reset action. A control whose
output is proportional to the integral of the input. This is called integral
mode/Action.

__Derivative Modes__

A control system whose output is proportional to the
derivation of its input time. And this process is called derivative mode.

__Proportional +
Integral (P+I) Control Mode__

Integral with **proportional control** is added to eliminate
offset error caused by proportional control. Integral control integrates input
signal offset error. That is, its output is proportional to the integral of the
input. In the **integral control action**, the controller keeps changing its output
until the offset error is eliminated.

**Integral control**, if used separately, has a very weak
response. If the error signal is stopped, the response of the integral control
is initially a ramp type. Conversely, if the step error signal is given at the
input of the proportional controller, then its output is also stepping
proportional to the input.

But cannot completely clear the proportional controller.
Since the offset error generated by the **proportional controller** cannot be
ignored. Therefore integral controller is used along with a typical controller.
The integral controller integrates any difference between the setpoint and the
measured quantity in the process. When the proportional control and the
integral control are used together, the change or difference caused by the
**proportional control** in a reset time can be corrected.

**Controller Gain/Proportional Band Formulas**

**The ratio of the change in input and output of the
controller is called gain.**

**Controller Gain** = Delta Output/Setpiont-Measurement

**Gain = **1/Proportional Band%

The ratio between the proportional band and the gain.

**Proportional Band% = **1/Gain*100

__P.B__

A proportional band is the amount of full-scale operator that turns on or off completely. Proportional bands often denote P. B.

__Relation b/w Gain and
Proportional Band__

The higher the proportional band, the lower the gain. Similarly, the lower the proportional band, the higher the gain. That is, they are inversely proportional to each other.

__Proportional +
Integral + Derivative (PID) Modes__

This type of controller is called a PID controller if all
three controls are combined in the same system, called the PID controller. The
integral component automatically resets the controller to eliminate residual
error. And provides a rapid response to changes in error. This control is also
called Three-Male control.

In this circuit PID control, v1 is a proportional control an
integral control v3 is a derivative control and v4 is a summing circuit. Which
combines the output of all three controls. And inverts it.

__Applications of PID__

PID is used in places where both errors are found.

**Software Performance****Mission Accomplished**

__Disadvantages of
Single Proportional Band__

When the signal uses the proportional band, it has the
following disadvantages.

- In the low proportional band, it works exactly like on-off control.
- The more proportional the band, the lower it gains so that these valves do not close or open completely.
- These always generate offset errors.

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