Motion control system anti-interference analysis - Database & Sql Blog Articles

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As the core part of some automation equipment, the motion control system directly affects the performance of the equipment, and one of the main factors affecting its reliability and stability is the anti-interference problem. Therefore, how to effectively solve the interference problem is a problem that cannot be ignored in the design of the motion control system.
First, the interference phenomenon In the application, often encounter the following main interference phenomena:
1. When the control system does not issue a command, the motor rotates irregularly.
2. The servo motor stops moving. When the motion controller reads the motor position, the value returned by the photoelectric encoder at the motor end is irregularly jumped.
3. When the servo motor is running, the value of the encoder read does not match the value of the command issued, and the error value is random and irregular.
4. When the servo motor is running, the difference between the value of the encoder read and the command value issued is a stable value or periodically.
5. Devices that share the same power supply as the AC servo system (such as monitors) are not working properly.
Second, interference source analysis There are two main types of channels for interference into the motion control system:
1. The signal transmission channel interferes, and the interference enters through the signal input channel and the output channel connected to the system;
2, power supply system interference.
The signal transmission channel is a way for the control system or driver to receive the feedback signal and issue the control signal. Because the pulse wave will have delay, distortion, attenuation and channel interference on the transmission line, the long-line interference is the main factor in the transmission process. Any power supply and transmission line have internal resistance. It is these internal resistance that cause noise interference of the power supply. If there is no internal resistance, no matter what kind of noise will be absorbed by the short circuit of the power supply, no interference voltage will be established in the line. The AC servo drive itself is also a strong source of interference, which can interfere with other devices through the power supply.
Third, anti-interference measures
1. Anti-interference design of power supply system
(1 line power supply is supplied, for example, the drive power of the execution motor is separated from the control power to prevent interference between devices.
(2) The noise filter can also effectively suppress the interference of the AC servo drive to other devices. This measure can effectively suppress the above several interference phenomena.
(3) The isolation transformer is adopted. Considering that the high-frequency noise passes through the transformer mainly by the mutual inductance coupling of the primary and secondary coils, but by the primary and secondary parasitic capacitance coupling, the isolation between the primary and secondary of the isolation transformer is shielded by the shielding layer. Distributed capacitance to improve resistance to common mode interference.
2. Anti-interference design of signal transmission channel (1) Optocoupler isolation measure In the long-distance transmission process, the optocoupler can be used to cut off the input and output channels of the control system and the input channel, output channel and servo driver. contact. If opto-isolation is not used in the circuit, external spikes will enter the system or go directly into the servo drive, creating the first type of interference. The main advantage of optocoupler is that it can effectively suppress spikes and various noise interferences, so that the signal-to-noise ratio during signal transmission is greatly improved. The main reason is: although the interference noise has a large voltage amplitude, but the energy is small, only a weak current can be formed, and the light-emitting diode of the input part of the optocoupler operates in a current state, and the general on-current is 10-15 mA, so Even if there is a high degree of large disturbance, it is suppressed because it cannot supply enough current.
(2) The long-distance transmission signal of the twisted-pair shielded wire is affected by the interference factors such as electric field, magnetic field and ground impedance during transmission. The grounding shielded wire can reduce the interference of the electric field. Compared with the coaxial cable, the twisted pair has a high frequency band, but has high wave impedance and strong anti-common mode noise, which can cancel the electromagnetic induction interference of each small link. In addition, in the long-distance transmission process, differential signal transmission is generally adopted to improve anti-interference performance. The use of twisted-pair shielded wire long-line transmission can effectively suppress the generation of second, third and fourth interference phenomena.
(3) Grounding grounding can eliminate the noise voltage generated when current flows through the ground. In addition to connecting the servo system to the ground, the signal shielding wire should also be grounded to prevent static induction and electromagnetic interference. If there is no proper grounding, a second type of interference may occur.