Servo motor zero incremental encoder and back to the origin of the method
Incremental encoder output signal for the square wave signal, and can be divided into belt change believe incremental encoder and ordinary incremental encoder, ordinary have two phase incremental encoder is sores on wave pulse output signal A and B, and zero signal Z;
With incremental encoder in believe it ABZ output signal, has sent 120 degrees each electron in # believe the sale, the sale of their respective each turn the logarithmic cycles and motor rotor poles.
With the sale of incremental encoder in believe electronic phase with the rotor magnetic pole phase change believe, or electric Angle between phase alignment method is as follows: 1.
With a dc power supply to the motor windings of UV flux to less than the rated current of dc, U, V, and the motor shaft orientation to an equilibrium position;
Using oscilloscope to observe the encoder U believe and Z signal;
The relative position of adjust the encoder shaft and motor shaft;
Adjustment, while observing the encoder U believe jump along, and Z signal until the Z signal stability in high level (
In the default Z signal of the norm for low level)
, locking the motor encoder and the relative position relations;
Back and forth to reverse the motor shaft, after, if every time the motor shaft free to return to balance position, Z signal can be stable at a high level, the alignment is effective.
Removed after the dc power supply, validation is as follows: 1.
Using oscilloscope to observe motor encoder U believe and UV line back emf waveform;
Turn the motor shaft, encoder U believe that number increased along with the motor back emf waveform from low to high UV line passing zero overlap, Z of encoder signal also appear in the zero point.
This verification method, also can be used as 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 potential, and UV line between the potential difference between 30 degrees, so that after alignment, U believe number of incremental encoder phase zero point - in contrast to the motor U electric potential
Point at 30 degrees phase alignment, and motor phase Angle in contrast to the U potential waveform phase, so at this time of incremental encoder U believe, mechanical and electrical Angle of phase - phase zero and electricity
30 degrees point alignment.
Some servo enterprises are accustomed to the encoder U believe that number zero aligned with the zero point directly to the motor Angle, to achieve this purpose, can: 1.
With equal three resistances into a star, and then the three resistance of star join separately UVW three-phase winding wire connected to the motor;
U to oscilloscope to observe motor phase input to the halfway point of the star resistance, can approximate to get U instead of the motor voltage waveform;
According to the convenience of operation, adjust the relative position of encoder shaft and motor shaft, or the relative position of encoder housing and motor shell;
Adjustment, while observing the encoder number U believe U instead rise along with motor voltage waveform from low to high passing zero, eventually make up along and zero overlap, locking relationship between encoder and the relative position of the motor, complete alignment.
Incremental encoder servo motor back to the origin?
To find the origin of the servo motor, when touching the origin switch, slowing down to stop immediately, to point to the origin.
This method of back to the origin no matter you are to select mechanical approach switch, or induction switch, light back to the original precision is not high, the influence of the temperature and the power fluctuation and so on, the response time of the signal will each time there is a difference, plus from the back to the origin of the high speed slow suddenly stop process, can complete, even eliminate mechanical reasons, every time back to the origin of the difference in magnitude.
Back to the origin directly find encoder Z believe that number, when have Z believe that number, slowing down to stop immediately.
This method only commonly used in the back to the original axis of rotation, and back to the original speed is not high, the precision is not high also.
This kind of back to the original method are the most accurate, is mainly used on nc machine tools: motor in the first period of the first to find the origin switch, have the origin switch signal, motor speed in the second paragraph at once in search of Z believe, first Z believes must be at the origin file block (
So you can notice, in fact, the origin of high-grade CNC machine tools and machine gear block is mechanical rather than induction, and its length must be greater than the motor a circle into the length of the straight line distance)
When find the first number Z believe, at this point there are two kinds of test, is a kind of file before back to the origin, is a kind of gear block after back to the origin.
To gear block after back to the former case, find gear block, after the first number Z believe electricity opportunities continue to same direction to find out after the first number Z believe.
Generally the even if the true origin, but because sometimes this point just at the origin of the movement in the middle of the state, prone to misoperation, and combined with other process requirements, to set an offset;
At this point, this is the real mechanical origin.
This kind of back to the original method are the most accurate and repeat back to the original high precision.
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