Anti interference Countermeasures of the most expl

Anti interference Countermeasures of industrial control software

when the computer control and detection system is used in the industrial field, there are often a large number of interference sources caused by various large-scale electrical and mechanical equipment in industrial control. Although it will not damage the hardware system, it will instantly interfere with the normal operation of the computer system, resulting in control failure, parameter changes, control accuracy and control effect decline, and even major accidents. To solve the anti-interference of the computer system, we should not only start from the hardware to reduce and avoid the influence of the outside world on the computer system, but also make corresponding countermeasures in the software, so that the system can effectively identify the interference, so as to avoid the influence of the interference on the control system. Make the effect powder maintain the size and color effect to the greatest extent. Structural characteristics and interference ways of industrial control software 1 Structural characteristics

at present, there are many kinds of industrial control systems and industrial control software in domestic industrial control systems. Although these industrial control software have different functions, they have the following characteristics in terms of their structure:

(1) some events in real-time industrial control systems have randomness, which requires industrial control software to deal with random events in time

(2) after completing the initialization of the system, the periodic industrial control software will enter the main program cycle. If there is an interrupt application during the execution of the main program, continue the main program cycle after the execution of the corresponding interrupt service program

(3) correlation industrial control software is composed of multiple task modules, which work together, are interrelated and interdependent

(4) artificial industrial control software allows operators to intervene in the operation of the system and adjust the working parameters of the system. 2. Interference path

under ideal circumstances, the industrial control software can be executed normally. However, under the interference of industrial field environment, the periodicity, relevance and real-time of industrial control software are destroyed, and the program cannot be executed normally, resulting in the out of control of industrial control system. This out of control is manifested in the following aspects

(1) the PC value of the program counter changes, which destroys the normal operation of the program. The data after the PC value is disturbed is random, which causes the program execution confusion. Under the wrong guidance of the PC value, the program executes a series of meaningless instructions, and finally enters the meaningless dead cycle, making the system out of control

(2) the state of the input/output interface is disturbed, which destroys the correlation and periodicity of the industrial control software completed in about half a month, causing the system resources to be monopolized by a task module, causing the system to deadlock

(3) interference invades the forward channel of the system and superimposes on the signal, resulting in increased data acquisition error. Especially when the current sensor interface to the channel is a small voltage signal input, this phenomenon is more serious

(4) RAM data area changes due to interference. According to the different interference channels and the nature of the disturbed data, the system is damaged in different conditions, some of which cause numerical errors, some make the control fail, some change the program state, and some change the working state of some components (such as timer/counter, serial port, etc.)

(5) control state failure. In the industrial control system, the output of the control state is based on the input of some conditional States and the logical processing results of 8,1 #, 2 # Al Si alloy experimental head mold. In these links, due to the intrusion of interference, the condition state error will be caused, resulting in the increase of output control error, and even the control malfunction. The software countermeasure system of abnormal program operation is interfered and infringed, resulting in the change of PC value and abnormal program operation. The software countermeasure for the abnormal operation of the program is to guide the system to restore the original state in time after finding the abnormal state. 1. Set the monitoring and tracking timer

to monitor the running state of the program by using the timed interrupt. The timing time of the timer is slightly longer than the normal operation of the main program for a cycle, and the timer time constant refresh operation is performed once during the operation of the main program. In this way, as long as the program runs normally, the timer will not be interrupted. When the program runs abnormally and cannot refresh the timer time constant in time, it will lead to timing interruption. The system will be reset by using the timing interruption service program. Use software to resist interference in 8031 application system. The specific methods are:

(1) use the overflow signal generated by the timer of 8155 as the external interrupt source INT1 of 8031, and use 555 timer as the external clock input of the timer in 8155

(2) the timing value of the 8155 timer is slightly greater than the normal cycle time of the main program

(3) in the main program, refresh the timing constant of 8155 timer every cycle

(4) at the beginning of the main control program, classify and judge whether the automatic recovery caused by hardware reset or timing interruption is handled. 2. Set software trap

when the PC is out of control, causing the program to "fly around" and constantly enter the non program area, as long as the interception measures are set in the non program area, the program can enter the trap, and then force the program to enter the initial state. For example, the data FFH in the Z80 instruction system exactly corresponds to the restart instruction RST 56, which automatically transfers the program to the 0038h entry address. Therefore, in the application system composed of Z80 CPU, as long as all non program areas are set to FFH to intercept the out of control program, and the transfer instruction is set at 0038h, the program can be transferred to the anti-interference processing program [1]. Software countermeasures for system deadlock in industrial control systems, input/output interface circuits such as a/d, d/a and display are essential. These interfaces work with the CPU in the way of search or interrupt, which is very sensitive to interference. Once the interference signal destroys the state of an interface, it will cause the CPU to mistakenly think that there is an input/output request for the interface and stop the current work, and turn to execute the corresponding input/output service program. However, the interface itself has no input/output data, so that CPU resources are occupied by the service program for a long time without release, and other task programs cannot be executed, and the whole system will have deadlock. The deadlock caused by this interference can be solved by the method of time slice in software programming. The specific steps are:

(1) allocate the corresponding maximum normal input/output time according to the time requirements of different input/output peripherals

(2) in each input/output task module, add the corresponding timeout judgment program. After the interference destroys the state of the interface, resulting in CPU misoperation, because the prepared information of the peripheral is invalid for a long time, after a certain period of time, the system