I. Introduction With the development of computer, electronic, electrical, and sensor technologies, my country's mechatronics level is also rising. Many product categories, including machine tools, automobiles, instruments, home appliances, light industrial machinery, textile machinery, packaging machinery, printing machinery, metallurgical machinery, chemical machinery, as well as industrial robots and intelligent robots, see new developments every year. Therefore, mechatronics technology has received increasing attention from all sectors, playing a significant role in improving people's lives, increasing work efficiency, saving energy, reducing material consumption, and enhancing enterprise competitiveness. Currently, many automated devices have increasingly stringent positioning requirements. Positioning control technology, as a core component of mechatronics systems, directly affects equipment performance in terms of reliability and stability. One of the main factors affecting its reliability and stability is anti-interference. How to effectively solve the interference problem is an issue that cannot be ignored in the design of positioning control systems. II. Composition of a Positioning Control System A complete positioning control system generally consists of a host controller, an actuator motor, a mechanical transmission mechanism, and position detection elements. Its structural block diagram is shown below: The host controller sends the analyzed and calculated motion commands to the motor driver in the form of digital pulse signals or analog signals. The driver performs power conversion and drives the motor to rotate according to the host control command. Simultaneously, if the actuator is an AC servo system, the photoelectric encoder or the grating (or magnetic ruler) at the motor end that detects the linear trajectory feeds back the detected position to the controller or driver, forming a semi-closed loop or full closed loop control. III. Interference Phenomena In applications, the following main interference phenomena are often encountered: 1. The motor rotates irregularly when the control system does not issue a command. 2. When the servo motor is stationary, the value fed back by the photoelectric encoder at the motor end jumps erratically when reading the actual position of the motor. 3. When the servo motor is running, the encoder value read does not match the issued command value, and the error value is random and irregular. 4. When the servo motor is running, the difference between the encoder value read and the command value issued is a stable value or changes periodically. 5. Devices that share the same power supply with the AC servo system (such as monitors) will not work properly. IV. Analysis of Interference Sources There are two main channels through which interference enters the positioning control system: signal transmission channel interference, which enters through the signal input and output channels connected to the system; power supply system interference. The signal transmission channel is the way for the control system or driver to receive feedback signals and issue control signals. Because pulse waves will experience delay, distortion, attenuation and channel interference on the transmission line, long-line interference is the main factor during transmission. Any power supply and transmission line has internal resistance. It is these internal resistances that cause noise interference from the power supply. If there is no internal resistance, any noise will be absorbed by the power supply short circuit and no interference voltage will be established in the line. In addition, the AC servo system driver itself is also a strong source of interference. It can interfere with other devices through the power supply. V. Anti-interference Measures 1. Anti-interference design of the power supply system (1) Implement power supply grouping. For example, separate the drive power supply of the actuator motor from the control power supply to prevent interference between devices. (2) Using a noise filter can also effectively suppress the interference of the AC servo drive to other devices. This measure can effectively suppress the above-mentioned interference phenomena. (3) Using an isolation transformer, considering that high-frequency noise is mainly coupled by the parasitic capacitance of the primary and secondary coils rather than by the mutual inductance of the primary and secondary coils, the primary and secondary windings of the isolation transformer are isolated by a shielding layer to reduce its distributed capacitance and improve the anti-common-mode interference capability. 2. Anti-interference design of signal transmission channel (1) Optocoupler isolation measures In the long-distance transmission process, an optocoupler is used to cut off the connection between the control system and the input channel, output channel and the input and output channels of the servo drive. If optocoupler is not used in the circuit, external spike interference signals will enter the system or directly enter the servo drive device, producing the first type of interference phenomenon. The main advantage of optocoupler is that it can effectively suppress spike pulses and various noise interferences, thereby greatly improving the signal-to-noise ratio in the signal transmission process. The main reason is that although the interference noise has a large voltage amplitude, the energy is small and can only form a weak current. The light-emitting diode in the input part of the optocoupler works in the current state, and the conduction current is generally 10-15mA. Therefore, even if there is a high voltage amplitude interference, it will be suppressed because it cannot provide enough current. (2) Twisted pair shielded cable long-line transmission signal will be affected by interference factors such as electric field, magnetic field and ground impedance during transmission. Using grounded shielded cable can reduce the interference of electric field. Compared with coaxial cable, twisted pair cable has a poorer frequency band, but high wave impedance and strong anti-common mode noise capability, which can make the electromagnetic induction interference of each small link cancel each other out. In addition, differential signal transmission is generally used in long-distance transmission to improve anti-interference performance. Using twisted pair shielded cable long-line transmission can effectively suppress the generation of the second, third and fourth interference phenomena. (3) Grounding Grounding can eliminate the noise voltage generated when the current flows through the ground wire. In addition to connecting the servo system to the earth, the signal shielding cable should also be grounded to prevent electrostatic induction and electromagnetic interference. If the grounding is not correct, the second interference phenomenon may occur. VI. Summary Interference suppression is a highly complex and practical problem, as interference phenomena can be caused by several factors. Therefore, in the design of positioning control systems, we should not only take anti-interference measures in advance, but also analyze the phenomena encountered during debugging, and continuously improve the system's circuit principles, specific wiring, shielding, and protection methods to enhance the system's reliability and stability.