Servo Motor position feedback component incremental encoder and absolute encoder
Mainstream servo motor position feedback components include incremental encoder, absolute encoder, sine and cosine encoder and Rotary transformer.
Phase alignment of incremental encoder. In this discussion, the output signal of incremental encoder is square wave signal, which can be divided into incremental encoder with commutation signal and traditional incremental encoder.
Ordinary incremental encoder has two-phase square wave pulse output signals A and B, and zero signal Z;
The incremental encoder with phase change signal has ABZ output signal, each electronic commutation signal differs by 120 degrees, and the number of cycles of each rotation is consistent with the polar logarithm of the motor rotor.
The phase of UVW electronic commutation signal and commutation signal of incremental encoder are aligned with the phase of rotor magnetic pole, and the electrical angle phase is as follows: 1.
Use DC power supply to transfer the UV winding of the motor to DC current less than rated current U in, V out to direct the motor shaft to the balanced position; 2.
Observe the U-phase signal and Z-phase signal of the encoder with an oscilloscope.
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 convenience of operation. Location; 3.
During adjustment, observe the U-phase signal transition edge and Z signal of the encoder until the Z signal stabilizes at a high level (
In this case, the default Z signal is usually low), Lock the encoder and engine. Relative positional relationship; The motor shaft twists back and forth.
After releasing the hand, if each motor shaft can freely return to the equilibrium position, the Z signal can be stabilized at a higher level and the alignment is effective.
After removing the DC power supply, please perform the following verification: Observe the U-phase signal of the encoder and the UV back electromotive force waveform of the motor with an oscilloscope;
When the motor shaft is rotated, the rising edge of the U-phase signal of the encoder coincides with the UV back electromotive force waveform of the motor at the zero crossing point from low to high, and the Z signal of the encoder also appears at the zero crossing point.
The above verification method can also be used as an alignment method.
It should be noted that due to electrical reasons, the zero phase point of the U-phase signal of the incremental encoder is consistent with the zero phase of the motor UV back electromotive force.
The U potential of the machine differs by 30 degrees from the reverse gap of the UV line.
Therefore, after this alignment, the zero phase of the U-phase signal of the incremental encoder is the opposite potential of the motor U-30 degree phase point alignment.
The phase angle of the electric angle of the motor is the same as the phase of the U-potential waveform, so the phase zero of the U-phase signal of the incremental encoder is the same as that of the electric angle phase of the motor-Align at 30 degrees.
Some servo companies are used 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.
Connect three stars with the same resistance into one star, and then connect the three resistors connected to the star to the UVW three-phase winding of the motor; 2.
Observe the U-phase input of the motor and the midpoint of the star resistance with an oscilloscope to approximate the U-potential waveform of the motor.
Adjust the phase of encoder shaft and motor shaft according to the convenience of operation.
The position or relative position of the encoder housing and the motor housing; 3.
During adjustment, 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 to lock the encoder and the motor. Relative positional relationship, fully aligned.
Since ordinary incremental encoders do not have UVW phase information and the Z signal can only reflect a point in a circle, there is no direct phase alignment potential. Therefore, this is not the subject of this discussion.
Phase alignment of absolute encoder, phase alignment of absolute encoder is not much different for single turn and multi turn.
In fact, the phase of the encoder is aligned with the motor. The phase of the electrical angle.
The early absolute encoder provided the highest single turn phase as a separate pin.
Encoder and motor can also be realized through horizontal inversion of 0 and 1. Phase alignment is as follows: 1.
The DC power supply is used to transfer the DC winding of the motor to a DC current less than the rated current U in and V out, and the motor shaft is directed to a balanced position; 2.
Observe the highest count bit level signal of absolute encoder with oscilloscope;
Adjust the relative position of the encoder shaft and the motor shaft according to the convenience of operation, or adjust the position of the encoder shell and the motor shell. When adjusting the relative position, observe the edge of the highest count bit signal, until the jumping edge happens to appear in the directional balance position of the motor shaft, the relative position of the encoder is then locked to the motor. 3.
After releasing the hand, rotate the motor shaft back and forth. If the motor shaft is freely returned to the equilibrium position each time, the jump edge can be accurately reproduced and the alignment is effective. TAG