Many of my friends have this doubt, how to determine encoder damage? Today, apart from electronics are several ways to tell you, teach you determine whether the encoder is damaged.
1. The rotary encoder connected to PLC, code value or number of pulses view correct?
2. rotary encoder connected to an oscilloscope to view the waveform.
3. The voltage profile with a multimeter test output is normal?
4 encoder NPN output: measuring the positive power supply and the signal output line, the output voltage is close to the supply voltage when the transistor turns ON, the output voltage is near 0V when the transistor turns OFF.
The encoder is PNP output: measuring signal output line and the negative power supply, the output voltage is close to the supply voltage when the transistor turns ON, the output voltage is near 0V when the transistor turns OFF.
There are many reasons encoder damage, pick a few small series and we talk about.
① mechanical damage
The encoder servo feedback failure is the most common variety of mechanical damage, the encoder includes an inner element structure due to the mechanical vibration, impact, shock, abrasion and other factors (the code wheel, the shaft and bearings, etc. ...) hardware damage.
② excessive vibration
Excessive mechanical vibration is likely to cause damage to the encoder code wheel, the shaft and bearings.
Servo feedback for instance, some vibration caused by the vibration of the motor body, such as: mechanical structure of the vibration motor in which the motor with the load requires a continuous movement ..., etc., this is relatively easy to prevent and avoid, as such vibration looks relatively straightforward, can be easily measured and corrective action is taken, as long as the intensity of the vibration motor body can be controlled in its nominal vibration levels (acceleration and frequency) range, will substantially avoid this vibration servo motor and a feedback harm.
There are some cases, is accompanied by mechanical vibrations in the shaft rotation during motor operation caused by, for example: the servo motor shaft output side being subjected to excessive axial force, occurs before and after the operation resulting in traverse shaft encoder mechanical axis the vibration; Alternatively, the servo motor is running, the output shaft has long been an excessive radial force, causing the motor shaft and bearing wear, thereby making the motor shaft by an eccentric to produce a strong vibration during high-speed rotation, etc. ....
These vibrations are substantially free of the vibration motor body and the mechanical structure so much equipment, and the motor is running but the forces of its output shaft and the shaft / bearing closely related to wear, even if the motor itself can not see any vibration, the encoder most likely because the axial or radial abnormal vibration and damage; the same time as these mechanical vibrations mainly in the interior of the motor shaft rotating at high speed, with a strong hidden, they tend to harm neglected people.
However, to prevent such an encoder failure or damage caused by the vibration motor shaft is not difficult, but requires the installation, use and maintenance of the servo motor, to ensure the axial and radial forces during operation the product within nominal limits.
③ impact
And all the machinery and electronic products, the servo motor and encoder products will have a nominal impact acceleration of nominal value. Excessive impact force may cause the encoder code plate, shaft, bearing, and damage to the IC chip of the circuit board, and even the entire feedback encoder damage and scrap.
Thus, the process of using an encoder, the body must try to avoid its impact is any external force, and in particular, to prevent the collision of the motor output shaft of the tap, either axially or radially from, for example: to the motor output shaft when installing various driving sleeve (belt wheel, coupling, reducer sleeve ... etc.), or in the process of mounting the motor drive mechanism, do not force the motor shaft and the housing body knocking.
④ wear
Another mechanical damage, that encoder shaft and bearing wear. Although not very common, but also need to attract some attention.
It is possible because the motor shaft chronic vibration (axial or radial) caused; also may be due to overdrive the motor shaft caused, although the general situation of overdrive servo motor rarely occurs, and the maximum allowable feedback encoder than the peak speed of the servo motor speed much higher, but in some unusual circumstances, for example: a feedback signal interference, the servo motor tuning error, and so on ... vertical load tumbled out of control, because the motor encoder feedback "is" overdrive the risk of damage is still present.
⑤ electrical damage
In various encoder failure, electrical damage occurred frequently. In one aspect, when the servo motor and / or when in poor electromagnetic compatibility electromechanical system environment, it may be because of the strong electromagnetic noise is instantaneously generated is very high (several thousand in which encoder feedback loop signal line even thousands of volts) voltage is high impact, resulting in damage to the encoder signal circuit.
On the other hand, the abnormal external line encoder, for example: a short circuit, open circuit, then the wrong line polarity reversal, the power supply abnormality (such as volatility) ..., etc., are also likely to cause an electrical servo feedback failure or damage.
The first two failures should be relatively pure electrical failure, electrical failure and universal encoder is the same. Another electrical damage is unique servo feedback, due to the mechanical damage caused by the motor. If the servo motor is running, because the output shaft has long been excessive axial or radial force, cause wear of the shaft and the bearing, it can lead to large metal chips and dust inside the motor, when attached to metal dusting encoding these when the circuit board is very likely due to the short caused by damage or malfunction of the internal circuit.
⑥ environmental impact
The environment here, of course, refers to the first servo motor in which the physical environment, comprising: humidity, temperature, dropping, oil, dust, corrosion, etc. .... Maintenance reports after the failure of many servo motors returned to the manufacturer, the encoder feedback will be referred to the erosion of pollutants due to damage, such as: immersion, dust ... and so on.
These contaminants from entering the interior of the reasons a lot of motor, the motor itself may be insufficient to degree of protection against harsh environments, such as: the IP54 servo motor is placed flush with water needs of food sanitation ...; it may be caused by improper installation methods , for example: a liquid splash is mounted on the motor axially to the environment seal is not installed, or due to motor plug / socket along its improper use causes the liquid into the interior of the motor cable interfaces, etc. ....
Therefore, the servo motor itself of IP protection, and environmental protection measures during product application integration and operation and maintenance are taken is very important. Open to electronic agents such as import encoder, high posital, Rennes and other encoders protection level, to adapt to harsh environments and long service life are welcome.
However, only good protection for servo motor applications is not enough, because the servo feedback, it is also affected by the internal environment of the motor. We need to pay attention to in the course of the encoder.
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