Common interference types and generation pathways in servo motor applications

During the process of using and debugging servo systems, various unexpected interferences may occasionally occur, especially for the application of pulse generating servo motors. Below, we will analyze the types and ways of interference from several aspects, in order to achieve targeted anti-interference. We hope to learn and research together.

Radiation interference from space

The most effective measure against radiation interference is metal shielding. Space radiated electromagnetic fields are mainly generated by power networks, lightning, radio broadcasting, and radar, and are commonly referred to as radiated interference.
Its impact mainly occurs through two paths: one is the direct radiation inside the servo, which causes interference through circuit induction; The second is the radiation to the servo communication network, which is caused by interference induced by communication lines. The probability of such interference is relatively low, and it is generally protected by setting up shielded cables.
The effective measures for conducting interference are to use power filters, isolated power sources, shielded cables, and reasonable and reliable grounding to solve the problem.

Three main types of conducted interference

1. Interference from power supply

Practice has proven that there are many cases of servo control system failures caused by interference introduced by the power supply, which are generally solved by adding voltage regulators, isolation transformers, and other equipment.

2. Interference introduced from signal lines

There are two main sources of this type of interference: one is grid interference caused by the power supply of the transmitter or the power supply of the shared signal instrument, which is often overlooked; The second is the interference induced by electromagnetic radiation in space on the signal line, that is, the external induced interference on the signal line, which is often very serious.
Interference introduced by signals can cause abnormal operation of circuit board components, and in severe cases, it can lead to component damage. For systems with poor isolation performance, it will also lead to mutual interference between signals, causing common ground system bus backflow, resulting in logical data changes, misoperations, and crashes.
There are also many cases where internal components of the control system are damaged due to signal interference, resulting in system failures. This type of interference often occurs in applications with long signal distances, and the method of adding relay isolation is often used to shield the induced voltage and solve the interference problem.

3. Interference from the chaotic grounding system

As is well known, grounding is one of the effective means to improve the anti-interference ability of electronic devices. Proper grounding can suppress the interference emitted by the device to the outside; However, incorrect grounding can actually introduce serious interference signals, making the system unable to function properly.
Generally speaking, the grounding of a control system includes system ground, shielding ground, AC ground, and protective ground. If the grounding system is chaotic, the interference to the servo system is mainly due to uneven distribution of potential at each grounding point, resulting in ground potential differences between different grounding points, causing ground loop currents and affecting the normal operation of the system.
For example, if both ends A and B of the cable shielding layer are grounded, there will be a ground potential difference, and current will flow through the shielding layer. When abnormal conditions such as lightning strikes occur, the ground current will be greater. In addition, the shielding layer, grounding wire, and earth may form a closed loop, and under the action of changing magnetic fields, induced currents may appear inside the shielding layer, interfering with the signal circuit.
If the system is confused with other grounding treatments, the generated ground current may cause unequal potential distribution on the ground wire, affecting the normal operation of the servo circuit. The key to solving such interference lies in distinguishing the grounding method and providing good grounding performance for the system.

Interference from within the system

Mainly generated by the mutual electromagnetic radiation between internal components and circuits of the system, such as the mutual radiation between logic circuits, the mutual influence between analog and logic grounds, and the mismatched use of components.
The actual working conditions on site are much more complex, and can only be analyzed on a case by case basis. However, in the end, there will always be a satisfactory solution, it's just a matter of different process experiences!