# Control Engineering

Control engineering is a basic study for almost all machines. Things with input and output need the theory to control.

The target of control engineering is dynamic system . In many cases, the theory made of linear simultaneous differential equation.

Control engineering has long history. Linear simultaneous differential equations have been studied. And non-linear cases have been also studied, and there is an interaction with chaos field.

## Feedback

The word "feedback" is used in business seen as a method to improve. "PDCA" is also used for same method.

"Feedback" is an important technique to control in control engineering. Feedback is used mathematically.

## Theory to Control

There are two kinds of theories to control, classical and modern. Both of them are same by the step to make differential equations for a system.

### Classical Control Theory

In classical theory, we use Laplace transform to integrate Control Theory. The integration is from 0 to infinity.

After Laplace transform, the relation of input and output is showed easily by transfer function.

### Modern Control Theory

In modern control theory, differential equations are showed as equation of state. After that, we do Differential Equation Model of matrix .

## Stability of The System

Stability is an important factor to control. "Stable" means values go defined value. In a wide sense, stable means values go in a small range.

## System Modeling

"Modeling" means to show the system by function. There are two kinds of modeling. The combination of them is called "gray box modeling".

• First Principle Modeling : Made by combination of physical laws
• System Identification Modeling (Black Box Modeling) : Statistically identified from experimental data

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