PID controller is the mechanical and electrical, metallurgical, mechanical, chemical and other industries most widely used industrial controller. There are two PID control by the drive mode: one is the built-in PID control function of the inverter, a given signal input through the terminal panel or inverter feedback signal to the control terminal. PID in the inverter. Adjusted to change the output frequency; the other is the use of an external PID controller is set to a given amount of feedback amount, and outputs it as a control signal to the control terminal of the drive.
A, PID control block diagram
Two, PID control overview
In automatic control, the general P (proportional), I (integral), D (differential) is not used alone. Often the PI operation, PD and PID control, combined control mode.
1) PI control
P operation control does not completely eliminate the deviation. In order to eliminate the residual deviation, PI control is generally used, i.e., P + I sum operation. When using PI control, and the target can be eliminated by a change in bias.
2) PD control
And oscillation damping system for the stable operation of the P, PD control is available, i.e., the sum of P and D operation. In other words, PD control is suitable for the process itself is not supported on the braking action.
3) PID control
PID control using PI control and advantages of the PD control to control the combination. PID calculation is the sum of the P, I and D of the three operational obtained unbiased, high precision and stable control process system.
① negative effects: When the deviation X (a target value) is positive, the amount of addition is performed (output frequency); if the deviation is negative, the execution amount is reduced.
② Positive effect: When the deviation X (target value - measured value) is negative, the execution amount increases (output frequency); if the deviation is positive, the execution amount is reduced.
Third, the access method of the feedback signal
1) given input method: When the drive is the PID function, the feedback signal measured by the sensor directly to the end of a given signal, which target signal is given by a keyboard.
2) Input independent: independent drive specially configured feedback signal input terminal, and some also inverter power sensor configuration, which may be the target value given from the keyboard, may also be input by the specified input terminal.
Four, PID regulation preset function
1) Preset PID adjustment function
PID is preset content inverter regulation is valid. PID adjustment function of the effective drive, which acceleration / deceleration process will depend entirely determined by the dynamic response of the P, I, D data, the original default "acceleration time" and "deceleration time" will no longer function.
2) a preset target value
PID regulator fundamental basis is the result of comparison between the target amount and the amount of feedback. Therefore, to accurately preset target value is very important, mainly in the following two aspects.
① panel input type: simply enter the target value to the keyboard. The target value is generally measured than the actual size of the sensor range of percentage. For example, the required air compressor pressure (target pressure) 6MPa, used pressure gauge range is 0 ~ 10Mpa, the target is 60%.
② Outer given formula: preset by an external potentiometer, adjustment more convenient.
Five, the inverter P, I, D - regulation law runtime
1) the input frequency of the inverter is adjusted only based on the comparison of the actual value and the target value, and no correspondence between the amount charged.
2) the output frequency of the inverter is always in a state to adjust its value usually fluctuates.
Text / Rongjiu College
Reproduced in: https: //www.jianshu.com/p/f03e860be175