Incremental encoder output signal is a square wave signal, but also can be divided into incremental encoder with commutation signal and ordinary incremental encoder, ordinary incremental encoder with two-phase orthogonal square wave Pulse output signals A and B, and zero signal Z; incremental encoder with commutation signal in addition to the ABZ output signal, but also have 120 degrees of mutual difference between the electronic commutation signal UVW, UVW cycles per revolution The number of poles of the motor rotor is the same. The phase alignment of the UVW electronic commutation signal with the rotor pole phase, or phase angle, of an incremental encoder with a commutation signal is as follows:
1. With a DC power supply to the motor through the UV winding with less than the rated current of the DC, U in, V out, the motor shaft orientation to a balanced position;
2 with the oscilloscope to observe the encoder U-phase signal and Z signal;
3. Adjust the encoder shaft and motor shaft relative position;
4. While adjusting, observe the encoder U-phase signal transition edge and Z signal until the Z signal is stable at high level (in this case the default Z signal is normally low), lock the encoder relative to the motor Positional relationship;
5. Back and forth to reverse the motor shaft, after sacking, if the motor shaft free to return to the equilibrium position each time, Z signal can be stabilized at high level, the alignment effective.
After removing the DC power, verify as follows:
1. Observe the encoder U-phase signal and the motor UV line back EMF waveform with an oscilloscope;
2. Turn the motor shaft. The rising edge of the U phase signal of the encoder coincides with the UV line back EMF waveform of the motor from low to high zero crossings, and the Z signal of the encoder also appears at this zero cross point.
The above verification method can also be used as an alignment method.
It should be noted that the phase zero of the U-phase signal of the incremental encoder is aligned with the zero point of the UV back electromotive force of the motor. Since the U-phase potential of the motor is different from the UV back electromotive force by 30 degrees, After 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 is the same as the phase of the U-phase opposite potential waveform. Therefore, The phase zero of the U phase signal of the unit is aligned with the -30 degree phase of the motor electrical angle phase.
Some servo companies accustomed to the encoder U-phase signal zero and electrical zero point directly aligned, in order to achieve this goal, you can:
1. Use three resistors of equal resistance to connect into a star, then connect the three resistors of the star to the UVW three-phase winding leads of the motor respectively;
2. Oscilloscope to observe the motor U-phase input and the midpoint of the star resistor, you can get the approximate motor U-phase potential waveform;
3. According to the convenience of operation, adjust the encoder shaft and motor shaft relative position, or encoder housing and motor housing relative position;
4 while adjusting, while observing the encoder U-phase signal rising edge and the motor U opposite potential waveform from low to high zero-crossing, the final coincidence of the rising edge and zero crossing, the lock encoder and the relative position of the motor to complete the alignment .