## What is a PID controller?

A PID controller is an instrument used in industrial control applications to regulate temperature, flow, pressure, speed, and other process variables. PID is the abbreviation for proportional integral derivative. PID controllers use a control loop feedback mechanism to control process variables and are the most accurate and stable controllers.

## What is meant by PID?

In the manufacturing process, if the equipment or space needs to be kept at a constant temperature, then PID is the best choice.

What is meant by PID?

P: Proportion, the input deviation is multiplied by a coefficient;

I: Integral, perform an integral operation on the input deviation;

D: It is differentiation, which performs a differential operation on the input deviation.

Mathematical description of PID:

u(t)=kp[e(t)+1/TI∫e(t)dt+TD×de(t)/dt].

Where

E(t) is the error signal;

U(t) is the output signal of the controller;

kp is the ratio coefficient;

TI is the integral time constant;

TD is the derivative time constant.

PID control is a kind of negative feedback control. Because in the feedback control system, the automatic regulator and the controlled object form a closed loop.

There are two possible situations when connected into a closed-loop: positive feedback and negative feedback.

The effect of positive feedback aggravates the imbalance of the inflow and outflow of the controlled object, resulting in system instability;

Negative feedback is to alleviates the imbalance, so as to correctly achieve the purpose of automatic control.

The instrument used in PID control is a PID regulator (also called a PID controller). Simply put, the PID control algorithm determines the price of the PID regulator. The temperature controller is also a kind of control algorithm that is more suitable for temperature control PID regulator. Its control algorithm is different from the regulator control algorithm commonly used for process control such as flow and pressure.

## Working principle of PID controller

PID controller, Promotion Integration Differentiation, that is, proportional-integral-derivative controller. It is mainly through the setting of three parameters Kp, Ki, and Kd. It is used to control the basic linearity and dynamic characteristics that do not change with time.

PID controller is based on the PID control principle to adjust the deviation of the entire control system. So that the actual value of the controlled variable is consistent with the predetermined value required by the process. Different control laws are applicable to different production processes. The corresponding control law must be selected reasonably. Otherwise, the PID controller will not achieve the expected control effect.

PID controller is a kind of feedback loop component that is very common in industrial control applications. This controller compares the collected data with a reference value. This difference is then used to calculate the new input value. The purpose of this new input value is to allow the system data to reach or maintain the reference value.

The PID controller can adjust the input value based on historical data and the occurrence rate of differences. This can make the system more accurate and more stable. It can be proved by mathematical methods. When other control methods lead to system stability errors or process repetitions, a PID feedback loop can keep the system stable.

## PID controller Applications

The PID controller is the most widely used controller. There are many digital pid algorithms.

PID controllers are mostly used for temperature control. But there are other more advanced and lower-level programs.

The PID regulator used by the instrument ranges from tens of yuan to tens of thousands of yuan. The difference lies in IO precision, type, algorithm complexity, operation speed, and additional functions.

The PID algorithm used by PLC is also different. Usually simpler than meters.

In the field of temperature control, there are PID meters, smart fuzzy meters, fuzzy PID meters, and even industrial computers.

If the temperature control also needs to control the temperature rise curve, then a simple PID meter is not suitable. A set value generator is also needed, and most intelligent thermostats with this function are built-in.

**Classic PID control algorithm regulator**

For example, the accuracy is 0.5%. The intelligent regulator is used for process control such as pressure, flow, and liquid level to achieve good control effects. The temperature control effect is not good when used for temperature control.

**Fuzzy control algorithm regulator**

Such as accuracy of 0.3%. The fuzzy PID regulator is used for pressure, flow, liquid level, and other process control effects. It is best for temperature control in plastic/food/packaging machinery, heating furnaces, and other industries with a constant temperature effect of ±1℃. PID parameter self-tuning effect is excellent It is the classic PID control algorithm regulator. The price of the two is the same.

**Artificial intelligence control algorithm regulator**

Such as an accuracy of 0.2%. This artificial intelligence regulator is suitable for all automatic control sites and can achieve very good control effects. The best constant temperature effect for temperature control is ±0.1℃. The effect of PID parameter self-tuning is better than the adjustment of classic PID control algorithms and fuzzy control algorithms The price is slightly higher. Product performance is no different from European and American products.

**Temperature controller**

Such as an accuracy of 0.2%. The temperature controller is dedicated to the temperature control of various large lag working conditions (such as kilns, electric furnaces). The temperature is constant and does not fluctuate. The performance is not much different from that of Japanese island power products. The cost is lower.

## Related measurement and control instruments

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