Servo motor phase and encoder position adjustment
2023-12-18
- Servo Motor phase and Encoder position adjustment The mainstream servo motor position feedback components include incremental encoders, absolute encoders, sine and cosine encoders, and resolvers.
Phase Alignment of Incremental Encoders In this discussion, the output signal of an Incremental Encoder is a square wave signal, and it can be divided into an incremental encoder with a commutation signal and an ordinary incremental encoder. Ordinary incremental encoders have two-phase orthogonal square-wave pulse output signals A and B, and zero-bit signal Z; in addition to the ABZ output signal, incremental encoders with commutation signals have a mutual difference of 120 degrees. The number of revolutions per revolution of the electronic commutation signal coincides with the number of pairs of magnetic poles of the motor rotor. The alignment of the phase of the UVW electronic commutation signal of the incremental encoder with a commutation signal and the phase of the rotor pole or the phase of the electrical angle is as follows:
1. Use a DC power supply to pass the motor's UV winding with a DC current less than the rated current, U in, V out, and orient the motor shaft to an equilibrium position;
2. Observe the U-phase signal and Z-signal of the encoder with an oscilloscope. According to the convenience of operation, adjust the relative position of the encoder shaft and the motor shaft, or the relative position of the encoder housing and the motor housing;
4. While adjusting, observe the U-phase signal edge of the encoder, and the Z signal until the Z signal is stable at a high level (in this default Z signal, the normal state is at a low level), lock the relative position between the encoder and the motor. Positional relationship;
. Rotate the motor shaft back and forth. If the motor shaft retracts to the equilibrium position each time, the Z signal can be stabilized at a high level, and the alignment is effective.
After removing the DC power supply, verify the following:
Observe the U-phase signal of the encoder and the UV back-EMF waveform of the motor with an oscilloscope;
2. Rotate the motor shaft. The rising edge of the U-phase signal of the encoder coincides with the zero-crossing point of the back-EMF waveform of the motor from low to high. The Z signal of the encoder also appears at this zero-crossing point.
The above verification method can also be used as an alignment method.
It should be noted that at this time, the phase zero of the U-phase signal of the incremental encoder is aligned with the phase zero of the back EMF of the motor's UV wire. Because the U reverse potential of the motor is different from the UV back-EMF by 30 degrees, After this alignment, the phase zero of the U-phase signal of the incremental encoder is aligned with the -30 degree phase point of the opposite potential of the motor U, and the phase of the electrical angle of the motor coincides with the phase of the opposite potential waveform of the U, so the incremental encoding is now performed. The phase zero of the U-phase signal of the device is aligned with the -30 degree point of the electrical angle of the motor.
^ Some servo companies are accustomed to aligning the zero point of the U-phase signal of the encoder directly with the zero point of the electrical angle of the motor. To do this, you can:
1. Use 3 resistors of equal resistance to connect into star type, and then connect the 3 resistors of the star connection respectively to the UVW three-phase winding leads of the motor; -
2. Using an oscilloscope to observe the midpoint of the U-phase input and star resistance of the motor, the U-reverse potential waveform of the motor can be approximated;
According to the convenience of operation, adjust the relative position of the encoder shaft and the motor shaft, or the relative position of the encoder housing and the motor housing;
4. While adjusting, observe the rising edge of the U-phase signal of the encoder and the zero-crossing point of the opposite potential waveform of the motor U from low to high, and finally make the rising edge coincide with the zero-crossing point, and lock the relative position relationship between the encoder and the motor to complete the alignment. .
( @1 V-O: a0 |, h Because the conventional incremental encoder does not have UVW phase information, and the Z signal can only reflect one point in a circle, it does not have direct phase alignment potential and is therefore not The topic of this discussion.
Absolute Encoder Phase Alignment Absolute Encoder Phase Alignment For single-turn and multi-turn applications, there is little difference. In fact, the alignment phase of the encoder is aligned with the phase of the motor's electrical angle within one turn. Early absolute encoders would give the highest bit level of a single-turn phase as a single pin. Using the 0 and 1 flip of this level, the phase alignment between the encoder and the motor can also be achieved as follows:
Using a DC power supply to the motor's UV winding to pass less than the rated current of DC, U into, V out, the motor shaft orientation to a balanced position;
2. Observe the highest count bit level signal of the absolute encoder with an oscilloscope;
According to the convenience of operation, adjust the relative position of the encoder shaft and the motor shaft, or the relative position of the encoder housing and the motor housing while adjusting, while observing the edge of the highest count signal until the edge of the motor appears accurately in the motor. The position of the shaft is balanced, and the relative positional relationship between the encoder and the motor is locked;
5. Turn the motor shaft back and forth, and if the motor shaft can return to the balance position each time it is free to return to the balance position, the alignment will be effective.
