1、 PLC automatic control system to improve the reliability 1. The main reasons for the lower control system reliability Although the main reason for the decline in industrial control system reliability and control aircraft PLC itself has high reliability But if the input signal to the PLC Switch mista
2、kes analog signal larger deviations, Output PLC control by the implementing agencies do not require action, which will enable control of mistakes The economic losses caused irreparable. PLC wrong signal to the scene affect the importation of the main reasons are: 1. Signal transmission line caused a
3、 short circuit or open circuit (due to mechanical shearing, their aging lines connecting dislocation). When the signal transmission line failure, the signal can not be transmitted to the scene PLC, the controlling mistakes. 2, the mechanical contact tremble, although close contact one scene, but tha
4、t closed several PLC, Although the increase in the filter circuit hardware, software differential increased orders, but because PLC scan cycle is too short, it was possible to count, add up. Displacements orders mistake, error control results. 3, the transmitter site and switches their own fault, su
5、ch as contact connections and Transmitter site reflects the normal work of non-electricity or larger deviations. These same fault control system will not function properly. Impact of implementing agencies to identify two main reasons: one, the contact is not reliable load control actions Although PL
6、C issued a direct action, but did not request executive body movements. 2, starting inverter control, inverter own fault, no converter required to bring the electrical work. 3, various electrical valve did not open the solenoid valve is opened, the customs clearance can not place As the implementing
7、 agency did not require action by the PLC control, the systems normal work, the systems reliability. To improve the reliability of the entire control system, it is necessary to increase the input signal reliability and accuracy of the executive body movements. Otherwise PLC should be able to promptl
8、y identify problems and suggest ways to use sound and light alarm and other operators as soon as possible troubleshooting. Let safe, reliable and correct manner. 2.Designed Fault Alarm System Sound design fault in the alarm system in automatic control system design, we designed a three-level fault d
9、isplay and warning system. 1 in the control of the control cabinet-level panel set up with the normal operation of the equipment and troubleshooting instructions light. When the corresponding light-normal operation of the equipment, the operation of the equipment malfunction indicator light to the f
10、requency of 1Hz scintillation. Light bulbs to prevent damage to equipment not properly reflect the work, set up a specialized fault reduction / Test button lights. Continuous system operation any time by more than 3 seconds the button, all beacons should all brightened. If, at this time, there are n
11、o instructions on the bright light shows are bad, they should be replaced after the light changed buttons reduction upon the state of the original work and display equipment operating status. 2-level fault show large-screen monitors set up in the center control room, equipment failure, written show
12、faults, process flow diagram corresponding equipment flickered in the incident will be recorded in the history of failure. Level 3 indicates fault signal box located in the center control room, equipment failure, the acoustic signal boxes will be used. - Alarm suggested staff time fault. At fault, t
13、he fault will classify some system failures is to stop the operation. But some little fault of the system, operating system fault zone, faults can be excluded from the operation. This will greatly reduce the entire system to stop the running time and improve system reliability operating standards. 3
14、.Input Signal Reliability PLC input signal to the scene to improve the reliability, it is first necessary to choose the higher reliability of the transmitter, and various switches. Sign al transmission lines to prevent short circuit caused a variety of reasons, disconnected or have access to. Second
15、, in the process of increasing digital filtering process and increase the credibility of the input signal. Design digital signal filtering methods are available, input contact at the scene after the one timer. Contact timing jitter and time based system to determine the response rate, the general in
16、 dozens of ms.This can ensure stability in close contact indeed, the only other response. Analog filter design procedures are available on the spot for sampling analog signal three times D conversion rate and the sampling interval from the analog signal changes in the rate-determining. 3rd sampling
17、data were stored in the data register DT10 and DT11 and DT12. When the last one after the use of data sampling, direct data exchange, data comparison of the maximum and minimum order removed. The median value of retained as a result of sampling DT0 were stored in the data register. In practical appl
18、ication, and also to extend the sampling of the number of tools to achieve better results. Improve the reliability of signal and can be read into the PLC control system using their own characteristics, signal to determine the relationship between the degree of credibility. If for liquid level contro
19、l, known as the size of the tank, the valve opening into the fluid and the fluid pressure is known. changes in a certain period of highly liquid tank is known about what extent, If given time Level PLC great difference in level data and estimates, judgments may be Level Fault, Failure to notify the
20、alarm system operating officer of the Level. Another example is the ultimate protection Tank Level namely, when he switches to send signals PLC, and the signal is really reliable, in the process of the tank level when we turn signal and the signal, if it also limit Level Meter readings position Note
21、 that the signal is true； If Level Meter readings not limit location. Level limit switch is the likely transmission of signal failure or fault lines. Similarly informed by the operator to address the alarm system failure. Because of the above methods in the design process, greatly improving the reliability of the input signal 4.Reliability implementing agencies
