Abstract: This paper analyzes the interference problems encountered by mechatronic systems in industrial applications and proposes some specific solutions. Keywords: Mechatronics, Interference, Anti-interference Mechatronics is a system that integrates microelectronics technology into the main functions, power functions, information functions, and control functions of machinery, and combines mechanical and electronic devices with relevant software. When mechatronic systems are deployed in industrial environments, they are always subject to interference from the power grid, space, and the surrounding environment. If the system cannot withstand the impact of interference, the electrical functional modules will not function normally, the microcomputer system will often experience program "runaway" due to interference, the sensor module will output false signals, the power drive module will output distorted drive signals, causing the actuator to malfunction, ultimately leading to system failure or even paralysis. 1 Interference Sources From the perspective of the channels through which interference enters the system, the interference sources encountered by the system can be divided into power supply interference, process channel interference, and field interference, as shown in Figure 1. (1) Power supply interference High-power equipment can cause serious pollution to the power grid, resulting in large fluctuations and surges in the power grid voltage. Due to the switching on and off of high-power switches and the starting and stopping of motors, high spike pulse interference often occurs on the power grid. According to statistics, the power supply input, instantaneous short circuit, undervoltage, overvoltage, and noise entering the power grid cause CPU malfunctions and data loss, accounting for more than 90% of various interferences. (2) Process channel interference Process channel interference mainly comes from long-line transmission. When there is leakage in electrical equipment in the system, the grounding system is not perfect, or the insulation of sensor measuring components is not good; and if the transmission lines of each channel are in the same cable or bundled together, especially when the signal line and the AC power line are in the same conduit, the common-mode or differential-mode voltage generated will affect the system and make the system unable to work. (3) Field interference There are always magnetic fields, electromagnetic fields, and electrostatic fields in the space around the system, such as solar and celestial radiation; electromagnetic waves from radio, telephone, and communication transmitters; and electromagnetic radiation emitted by surrounding intermediate frequency equipment. These field interferences will affect the normal operation of each functional module through the power supply or transmission line, causing the level to change or generating pulse interference signals. 2 Measures to resist power supply interference (1) Anti-interference of power distribution system First, measures should be taken from the power distribution system, and the power distribution scheme shown in Figure 2 can be adopted. Secondly, a discrete power supply scheme can be adopted, that is, each module of the system is powered by a DC power supply composed of independent transformer, rectifier, filter and voltage regulator circuits. This reduces the danger of centralized power supply, and also reduces the common impedance and mutual coupling of common power supply, improves the reliability of power supply, and is also conducive to heat dissipation of power supply. In addition, the AC power input line should use thick wire, the DC output line should use twisted pair wire, the twist pitch should be small, and the wiring length should be shortened as much as possible. (2) Using power monitoring circuit to implement anti-interference measures in the power distribution system is essential, but these are still difficult to resist microsecond-level interference pulses and transient power outages, especially the latter, which is a malicious interference and may cause serious accidents. Therefore, further protective measures should be taken, that is, using power monitoring circuit. The power monitoring circuit needs to have the functions of monitoring the instantaneous short circuit, instantaneous voltage drop, microsecond-level interference and power failure of the power supply voltage; and timely output of reset signals and interrupt signals for the CPU to accept. 3 Anti-interference measures for process channels The main measures to suppress interference on the process channel are opto-isolation, twisted-pair transmission, impedance matching, current transmission and reasonable wiring. (1) Opto-isolation Utilizing the current transmission characteristics of optocouplers, two optocouplers between modules can be "floated" by connecting wires during long-distance transmission. This method not only effectively eliminates the noise voltage interference generated when the current flows through the common line between electrical functional modules, but also effectively solves the problem of long-distance driving and impedance matching. (2) Twisted-pair transmission Twisted-pair is a commonly used transmission line in long-distance transmission. Compared with coaxial cable, although the bandwidth is narrower, the impedance is higher, which reduces common-mode interference. Since the loops formed by the twisted pair change the direction of electromagnetic induction between the lines, they cancel each other out, thus having a certain suppression effect on electromagnetic field interference. (3) Impedance matching: In long-distance transmission, if the impedances at the transmitting and receiving ends are mismatched, signal reflection will occur, causing signal distortion. The degree of harm is related to the transmission frequency and the length of the transmission line. (4) Current transmission: In long-distance transmission, using current transmission instead of voltage transmission can achieve better anti-interference capability. (5) Reasonable wiring: High-voltage feeders must be routed separately, and strong signal lines and weak signal lines should avoid parallel routing as much as possible. 4 Suppression of field interference : The main methods to prevent field interference are good shielding and proper grounding. The following issues should be noted: (1) The simplest way to eliminate electrostatic interference is to ground the inductor. When grounding, prevent the formation of grounding loops. (2) To prevent electromagnetic field interference, signal lines with shielding layers can be used, and the shielding layer should be grounded at one end. (3) Do not use the shielding layer of the conductor as a signal line or a common line. (4) In terms of wiring, do not use common lines between power supply circuits and detection and control circuits, nor between analog circuits and digital pulse circuits, to avoid crosstalk. 5 Software Anti-interference Technology Various forms of interference will eventually be reflected in the microcomputer module of the system, resulting in data acquisition errors, control failure, data tampering, and program malfunction. Although the above-mentioned anti-interference measures are taken in the system hardware, the normal operation of the microcomputer system cannot be guaranteed. Because software anti-interference is a self-defense behavior of the microcomputer system, the necessary conditions for implementing software anti-interference are: (1) Under the action of interference, the microcomputer hardware and its connected functional modules will not be damaged, or the easily damaged units are equipped with monitoring status that can be queried. (2) The system program and fixed constants will not change due to the intrusion of interference. (3) Important data in the RAM area can be re-established after the interference intrusion, and no disallowed data will appear when the system restarts. To suppress interference in data sampling, the following methods can be used: digital filtering, width judgment to resist spike pulse interference, etc., or repeated checking method and deviation judgment method can be used to check and judge whether there is interference signal. The software anti-interference measures for program malfunctions generally include: (1) Setting up a WATCHDOG function, with hardware cooperation, to monitor the operation of the software and handle the corresponding faults. (2) Setting up software traps. When the program pointer goes out of control and the program enters the non-program space, an interception instruction is set in the space to make the program enter the trap and then force it to return to the initial state. References: [1] Zhang Jianmin. Mechatronics Principles and Applications. Beijing: National Defense Industry Press, 1992 [2] Tianjin Electric Drive Design Institute. Electric Drive Automation Technology Handbook. Ministry of Machinery and Electronics Industry, 1993 [3] Wei Junmin, Zhou Yanjiang. Mechatronics System Design. Beijing: China Textile Press, 1998