A common source of interference in the servo control system - Xinjie

Radiative disturbance from space

The most useful method for radiation disturbance is metal shielding. Space radiated electromagnetic fields are mainly caused by power networks, lightning, radio broadcasting, radar, etc., and are generally referred to as radiation disturbances.

Its influence mainly goes through two paths: one is to directly radiate to the servo internally, and the circuit induces disturbance; The second is the radiation of the servo communication network, which is disturbed by the communication line. The probability of this kind of disturbance is relatively small, and it is generally maintained by setting up shielded cables.

A common source of interference in the servo control system - Xinjie

A common source of interference in the servo control system - Xinjie

There are three primary types of conduction disturbances

A useful way to deal with conducted disturbances is to use power filters, block power supplies, shielded cables, and reasonable and reliable grounding to deal with the problem.

1. Disturbance from the power supply

Practice has proved that there are many cases of servo control system failures caused by the disturbance introduced by the power supply, which are generally treated by equipment such as voltage regulators and barrier transformers.

There are two main ways of information for this kind of disturbance: one is the disturbance of the power grid connected through the power supply of the transmitter or the power supply of the common signal appearance, which is often ignored; The second is that the signal line is disturbed by space electromagnetic radiation induction, that is, the external induction disturbance on the signal line, which is often very severe.

2. Disturbance from the introduction of signal lines

Disturbances introduced by signals can cause abnormal operation of circuit board components, and in severe cases, damage to components. As for the system with poor blocking function, it will also cause the signals to disturb each other, causing the bus backflow of the common-ground system, resulting in logical data changes, malfunctions and crashes.

There are many cases where the internal components of the control system are damaged due to signal introduction disturbances, and there are many cases where the system fails. This kind of disturbance often occurs in the use of long signal distances, and the method of adding relay blocking is often used to shield off the induced voltage and deal with the disturbance problem.

3. Disturbance from the chaos of the grounding system

As we all know, grounding is one of the useful methods to improve the anti-disturbance of electronic equipment, and the correct grounding can not only press the equipment to announce the disturbance; However, incorrect grounding can introduce severe disturbance signals and make the system unable to function properly.

Generally speaking, the ground wire of the control system includes the system ground, shielding ground, AC ground and maintenance ground, etc., if the grounding system is chaotic, the disturbance to the servo system is mainly the uneven distribution of the potential of each grounding address, and there is a ground potential difference between different grounding addresses, which causes the ground loop current and affects the normal operation of the system.

For example, if both ends of the cable shield A and B are grounded, there is a ground potential difference, and there is a current flowing through the shield. When an abnormal situation such as lightning strikes occurs, the ground current will be greater. In addition, the shield, ground wire, and ground may form a closed loop, and under the effect of changing magnetic fields, induced currents will occur in the shield, disturbing the signal loop.

If the system is chaotic with other grounding treatments, the ground-ground circulation may have unequal potential distribution on the ground, which will affect the normal operation of the servo circuit. The key to dealing with this type of disturbance is to identify the grounding method and provide a good grounding function for the system.

Disturbances from within the system

It is mainly caused by the electromagnetic radiation between the components and circuits within the system, such as the mutual radiation of logic circuits, the mutual influence of imitation and logic, and the mismatch between components.

The actual on-site working conditions are much more complex, and can only be analyzed in specific problems, but in the end, there will be a satisfactory solution, but the process experience is different.

A common source of interference in the servo control system - Xinjie

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