First, the definition of interference
Interference is an internal or external factor that adversely affects the normal operation of the system. Broadly speaking, the interference factors of mechatronics systems include electromagnetic interference, temperature interference, humidity interference, acoustic interference and vibration interference. Among many disturbances, electromagnetic interference zui is common, and the influence on the control system is large. Other interference factors can often be solved easily by some physical methods. This section focuses on the relevant content of electromagnetic interference.
1 , the source of interference
Devices that generate interfering signals are referred to as sources of interference, such as transformers, relays, microwave equipment, motors, cordless and high voltage power lines, etc., which can generate airborne electromagnetic signals. Of course, lightning, the sun and cosmic rays are sources of interference.
2 , the route of transmission
The propagation path refers to the propagation path of the interference signal. Electromagnetic signals travel in a straight line in the air, and the penetrating propagation is called radiation propagation; the propagation of electromagnetic signals into the device by means of wires is called conduction. The route of transmission is the main reason for interference with proliferation and ubiquity.
3 , accept the carrier
Accepting a carrier means that a certain part of the affected device absorbs the interference signal and converts it into an electrical parameter that affects the system. The receiving carrier cannot sense the interference signal or weaken the interference signal so that it is not affected by the interference, thereby improving the anti-interference ability. The acceptance process of accepting the carrier becomes coupling again, and the coupling is divided into two types, conduction coupling and radiation coupling. Conductive coupling means that electromagnetic energy is coupled to the receiving carrier in the form of a voltage or current through a metal wire or lumped element (such as a capacitor, transformer, etc.). Radiative coupling means that electromagnetic interference energy is coupled to the receiving carrier in the form of an electromagnetic field through space.
According to the definition of interference, the reason why the signal is interference is because of its adverse effect on the system, and vice versa, it cannot be called interference. It can be seen from the elements that form interference that eliminating any of the three elements will avoid interference. Anti-jamming technology is the research and processing of three elements.
Second, the electronic platform anti-jamming method:
1 , shielding
The shielding is a box-shaped or shell-shaped shielding body made of conductive or magnetically permeable material, which surrounds the interference source or the interference object to cut or weaken the spatial coupling channel of the interference field and prevent the transmission of electromagnetic energy. The nature of the interference field shielded on demand can be divided into electric field shielding, magnetic field shielding and electromagnetic field shielding.
The electric field shielding is to eliminate or suppress interference due to electric field coupling. A metal material having good electrical conductivity such as copper or aluminum is usually used as a shield. The shield structure should be as complete and tight as possible and maintain a good grounding.
Magnetic field shielding is to eliminate or suppress interference due to magnetic field coupling. For static magnetic fields and low-frequency alternating magnetic fields, materials with high magnetic permeability can be used as shielding bodies to ensure smooth magnetic circuit. For the high-frequency alternating magnetic field, the diamagnetic field generated by the eddy current induced on the shield body mainly acts to repel the original magnetic field. The materials used are also good conductors such as copper and aluminum.
2 , isolation
Isolation means that the interference source is isolated from the receiving system, so that the useful signal is transmitted normally, and the interference coupling channel is cut off to achieve the purpose of suppressing interference. Common isolation methods are photoelectric isolation, transformer isolation, and relay isolation.
3 , filtering
Filtering is an important method to suppress interference conduction. Since the spectrum of the electromagnetic interference emitted by the interference source tends to be much wider than the spectrum of the signal to be received, when the receiver receives the useful signal, it also receives unwanted interference. At this time, a filtering method can be employed to suppress only the required frequency components and suppress the interference frequency components.
Commonly used filters can be classified into low-pass, high-pass, band-pass, and band-stop filters according to their frequency characteristics. The low-pass filter only passes the low-frequency components, while the components above the cut-off frequency are suppressed, attenuated, and not allowed to pass. The high-pass filter only passes the high-frequency component, while the component below the cut-off frequency is suppressed, attenuated, and is not allowed to pass. The bandpass filter only allows the frequency components in a certain frequency band to pass, while the components below the lower cutoff and above the upper cutoff frequency are suppressed and are not allowed to pass. The band rejection filter only suppresses the frequency components in a certain frequency range and does not allow them to pass, and the frequency components below the lower cutoff and above the upper cutoff frequency pass.
4 , grounding
A low-impedance connection is made between a circuit, a device case, and the like as a common reference point (earth) as a zero potential, which is called grounding. There are two purposes for grounding: one is for safety, for example, the casing and the base of an electronic device are connected to the earth. When there is leakage in the device, it does not affect personal safety, which is called safety grounding. The second is to give the system Provide a reference potential, such as the zero potential point of the pulse digital circuit, or to suppress interference, such as shield grounding. Called the working ground. The working ground includes two grounding methods and multiple grounding.
5 , software anti-jamming design
a, software filtering
A method of identifying useful and interfering signals with software and filtering out interfering signals is called software filtering. There are two principles for identifying signals:
(1) Time principle If you master the regularity of the useful signal and the interference signal in time, you can program to open the input port in the time zone where the useful signal is received, and close the input port in the time zone where the interference signal may occur. Filter out the interference signal.
(2) Space principle In order to ensure that the received signal is correct, the same signal received from different locations, with different detection methods, via different routes or different input ports can be compared and judged according to the established logical relationship. True or false, thus filtering out interference signals.
(3) Attribute principle The useful signal is often a signal of a certain amplitude or frequency range. When the received signal is far away from the signal area, the software can be rejected by identification.
b, software "trap"
From the perspective of software operation, transient electromagnetic interference may cause the CPU to deviate from the predetermined program pointer and enter the unused RAM area and ROM area, causing some inexplicable phenomena, in which the infinite loop and the program "fly off" are common. In order to effectively eliminate such interference failures, the software "trap method" is commonly used. The basic guiding principle of this method is to fill the unused units of the system memory (RAM and ROM) with a certain restart code command as a software "trap" to capture the "fly-off" program. Generally, when the CPU executes the instruction, the program automatically transfers to a starting address, and starting from the starting address, a hot start program for restarting the program is resumed, and the hot start program scans various states of the scene. Based on these states, it is determined which program the program should go to, and the system is put back into normal operation.
c, software "watchdog"
"Watchdog" (WATCHDOG) is a hardware (or software) method that requires the use of a monitoring timer to periodically check a certain program or interface. When the system does not check the program or interface for a certain period of time, the system can be determined to be running incorrectly ( Interference occurs), can be reset by software or run in a predetermined manner. "Watchdog" is a software anti-jamming measure commonly used by industrial control machines. WATCHDOG can help the system automatically resume normal operation when the intruding spike electromagnetic interference causes the computer to "fly the program."
Pigment
China Pigment Suppliers
Here you can find the related products in Pigment, we are professional
manufacturer of Pigment. We focused on international export product
development, production and sales. We have improved quality control processes of Pigment to ensure each export qualified product.
If you want to know more about the products in Pigment, please click the Product details to view parameters, models, pictures, prices and Other information about Pigment.
Whatever you are a group or individual, we will do our best to provide you with accurate and comprehensive message about Pigment!
Lycopene, Amaranth, β-Carotene, Beta carotene, Carmine, Food Colorant
Xi'an Gawen Biotechnology Co., Ltd , https://www.ahualynbios.com