Hardware configuration:
1-----Variable frequency drive -2 units of 3.7KW. It should have (main+auxiliary functions) VF type setting
2-----2 frequency converters -1 for air outlet and 1 for air inlet
3------The air inlet frequency converter must be connected to a resistor. Improve the output stability of the frequency converter.
4------Program operation. Manual setting of air outlet - frequency remains unchanged. Inlet air is based on outlet air. Adjust up and down by 50%. For example, the air outlet is set at 15Hz and the maximum frequency of the air inlet is set. 15+15x50%=22.5HZ Minimum frequency -15-15X50%=7.5HZ. This can be set in the (superposition amplitude) of the intake frequency converter. Two frequency converters use (main+auxiliary) function. The wind is the main source. Air intake is auxiliary.
5----The acceleration and deceleration time of the two frequency converters is set at around 15-25 seconds. Improve air flow stability
6-----We need one 4AD module. One 2DA module.
7-----Ultrasonic sensor - Beijiafu UB500-18GW75-U-V15 (voltage type) with a maximum sensing distance of 450MM and a minimum sensing distance of 50MM. Three ultrasonic waves are used to measure the change in membrane bubble diameter using the three-point center method.
8----Method for calculating bubble width, diameter X3.14=circumference.
9----Usage - First install 3 sensors. Installation distance must be manually entered. Set this value. Equivalent to an initial value. The distance between the three centers should be close. For example, if the input installation distance is 550MM, the actual sensing range is. Between 50-500. Because both the maximum and minimum have a blind spot of 50MM, and a width of 800MM is set, the distance between its centers is. 800/3.34=approximately 255mm. Measure distance using three ultrasonic sensors. Calculate the position deviation value between the comparison and the set distance. PID will be used. Control the frequency of the air inlet frequency converter. For example, the current distance required is 255mm. If the ultrasonic monitoring shows that the membrane bubble is less than 255mm, the air intake will accelerate. Reduce speed when the size is 255mm to maintain stability at a distance of 255mm.
10----In manual mode. You can freely set and modify the frequency of air intake and exhaust. In automatic mode, only the frequency of the air outlet frequency converter can be set and modified. Cannot modify the intake frequency. The air intake is automatically controlled by following. The main frequency is air intake. The auxiliary frequency is controlled by the output of the DA module.
11----The AD module collects simulated voltage values of three ultrasonic waves. Convert to digital quantity. Compare instructions through PLC. Compare and calculate with the set value. Convert digital quantity to voltage analog quantity. Through the DA module. Directly control the intake frequency converter.
12----Ultrasonic sensors are of analog voltage type. After sensing an object. Measure distance changes and provide feedback on voltage changes. Collect this simulated voltage variation. Perform comparative calculations within the PLC.
13---Require high resolution of the frequency converter, followed by processing of DA analog voltage output. To achieve minimal voltage fluctuations. Quick response.
14----The control error should be small. The air intake should be stable. Cannot be too big or too small.
15-----The adjustment range of the intake frequency should be flexible. The adjustment amount cannot be a fixed value. For example, the larger the deviation. The greater the adjustment range. The smaller the deviation amplitude. The smaller the adjustment range. Because the acceleration and deceleration are fixed values set by the frequency converter. PLC program controls the size of DA analog output.
16-----Control DA analog output. It needs to be divided into three to four sections. Cannot output and adjust in place at once. Because of the airflow controlled by the fan. It belongs to the soft traffic type curve variation. It does not belong to the mechanical control type. For example, calculating an analog quantity requires outputting a voltage of 2V. Output 70% first Convert to 1.4V. Then output 20% Convert to 0.4V. Finally, output 10% to 0.2V.
17-----Collect AD analog signals. We need to make 5 counters and set the interval time. This time can be set and modified. It is not a collection. We need to collect 5 results. Perform comparative analysis and calculations. Only then can the comparative deviation be determined, because the changes in membrane bubbles are not only influenced by internal air changes. It will also be affected by changes in external air. So the change amount collected once cannot be used as a basis, and ultrasonic sensors measure distance as a reference. Three point circle method. It is divided equally by the sum of three measured distances. Determine the diameter distance. It is not based on one of the measured distances.
18-----The system calculates - simply and directly - using diameter. Pi (pi). Conversion of perimeter.. There are also comparative instructions. PID instruction. And communicate with the frequency converter. Touch screen communication. However, during initial use and actual production, continuous testing and modification are required to stabilize the program.
19----Correction value for width. Excessive and insufficient values. For example, setting 800MM. In reality, there is only 780MM. It is necessary to set 20MM in the lower value. For example, if it is too large. Set the value to be too high.
20----I will provide the touch screen operation interface on my end.
21----The program needs to be used. Gain. Calculus. PID。 Counter. Compare instructions. Send instructions. Perimeter formula.
Editor: Sichuan Jinzhongde Science and Technology Research Institute
