Zero setting method of incremental servo motor encoder
The output signal of incremental is square wave signal, and it can be divided into with changing trust sign and ordinary incremental encoder. The ordinary incremental encoder has the output signal A and B of two-phase ortho-wave pulse, as well as the zero-position signal Z.In addition to ABZ output signals, incremental encoders with changing trust signs are also equipped with electronic changing trust signs UVW with a difference of 120 degrees. UVW's respective number of cycles per revolution is consistent with the number of magnetic poles of the motor rotor.The alignment between the phase of the UVW electron change trust sign of the incremental encoder with the change trust sign and the phase of the magnetic pole of the rotor or the phase of the electric Angle is as follows:
1. Use a DC power supply to pass the UV winding of the motor with direct current less than the rated current, U in and V out, and direct the motor shaft to a balanced position;
2. Observe the U and Z signals of the encoder with an oscilloscope;
3. Adjust the relative position of the encoder shaft and the motor shaft;
4. While adjusting, observe the switching edge of the encoder U sign, and Z signal until the Z signal is stable at a high level (the default Z signal is low level), and lock the relative position relationship between the encoder and the motor;
5. Twist the motor shaft back and forth. After giving up, if the motor shaft freely returns to the balance position each time, Z signal can be stable at the high level, then alignment is effective.
After the DC power supply is removed, the verification is as follows:
1. Use an oscilloscope to observe the u-sign of the encoder and the inverse potential waveform of the UV line of the motor;
2. Rotate the motor shaft, the rising edge of the encoder's U sign coincides with the reverse potential waveform of the motor's UV line from low to high zero crossing, and the encoder's Z signal also appears at this zero crossing.
The above validation method can also be used as an alignment method.
It is important to note that at this time of incremental encoder U believe the phase zero and motor UV line against potential phase zero alignment, because U instead of the motor electric potential, and UV line between the potential difference between 30 degrees, so that after alignment, U believe the phase zero point of incremental encoder and motor U instead of potential - 30 degrees phase alignment, and motor phase Angle with U instead of voltage waveform in phase, so the number of incremental encoder U believe the phase zero and electrical mechanical and electrical Angle of phase - 30 degrees point alignment.
Some servo enterprises are used to align the zero point of the encoder U trust number directly with the zero point of the electro-mechanical Angle. To achieve this purpose, it can:
1. Connect three resistors with the same resistance value into the star type, and then connect the three resistors connected with the star type into the UVW three-phase winding lead of the motor respectively;
2. By observing the middle point of the motor's U phase input and the star resistance with an oscilloscope, the U inverse potential waveform of the motor can be approximately obtained;
3. Adjust the relative position of the encoder shaft and the motor shaft, or the relative position of the encoder housing and the motor housing according to the ease of operation;
4. While adjusting, observe the zero crossing of the rising edge of the encoder's U confidence sign and the opposite electric potential waveform of the motor U from low to high, and finally make the rising edge and the zero crossing coincide, lock the relative position relationship between the encoder and the motor, and complete alignment.
Since the ordinary incremental encoder does not have UVW phase information and the Z signal can only reflect a point position within a circle, it does not have direct phase alignment potential, so it will not be discussed any more.