Speed encoder works generally associated with shaft speed encoder, speed measuring the amount of pulse encoder is fixed, the axis of rotation, can output pulse speed encoder, PLC or receive pulse counter, according to the speed of the shaft to turn at the same time, not received in unit time is different, the total pulse speed performance here, according to the length of the pulse amount and the actual transfer can calculate the real speed m/min.
Motor speed detection is very important in the motor control, especially need to accurate rotor position control motor motion applications, such as the position servo system.
Motor control system of position detection usually have: micro-motor solution components, optoelectronic devices, magnetic sensor, electromagnetic induction components etc.
The position detection sensor or coaxial connected with the load of the motor end, or installed in certain parts of the motor directly.
The photoelectric element measuring accuracy is higher, can accurate reflection of the motor of the mechanical rotor position, thus indirectly reflect the mechanical load, which is connected with motor accurate mechanical position, so as to achieve the purpose of precise control motor position.
Speed measuring method of photoelectric encoder is a kind of photoelectric encoder digital Angle sensor, it can transform angular displacement quantity for the corresponding electrical pulse output, it is mainly used for mechanical Angle position and rotating speed of detection and control.
At a speed measuring system consisting of photoelectric encoder, there are three kinds of commonly used speed measuring method, namely the 'M', 'T', and 'M/T method'.
Acceleration value theory, as long as according to the above method measured the speed of the adjacent two speed points difference and its time interval can be calculated.
In the analysis and comparison of the existing various speed measuring method based on photoelectric encoder is proposed on the basis of a new method, has high speed measuring precision and real-time performance.
The following is the commonly used several kinds of speed measuring method based on photoelectric encoder.
Speed - 'M method'
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By measuring a fixed time interval of the encoder pulse number to calculate the rotational speed, suitable for high speed occasion.
'T' speed -
By measuring the time interval of the two adjacent pulse encoder calculating speed, suitable for speed is low, when the speed is higher the accuracy is poor.
Speed - 'M/T method'
Before the 'M/T method' is a combination of the two methods, measuring a certain number of encoder pulses and these pulses at the same time the time, has good accuracy in the whole speed range, but with low speed, this method need long test time to ensure the accuracy of the results, can meet the rapid dynamic response speed detection system.
New speed measuring method based on photoelectric encoder, 'M/T method' comprehensive 'M' and 'T' advantage, but low speed dynamic response is too slow, so if you can according to the speed of real-time change '1 M value of M/T method', as the speed reduce the value of reduced by 1 M, can improve the M/T method in low speed 'speed slow dynamic response.
Based on this principle, through the corresponding software and hardware design to realize a high precision speed measuring method.
Its principle and the calculation of the relative error of speed on the surface and there is no difference between 'M/T method', and actually 'M/T method' of sampling period always produce 1 M encoder pulse time, as the speed increases, the encoder pulse frequency, sampling period gradually become smaller, the relative error increases;
The proposed speed measuring method due to the value of 1 m can change with speed, increase at a high speed period of 1 m value made sampling period basically remain unchanged.
And its relative error is basically the same, in a low speed, 1 M value to be 1, satisfy the requirement of the system dynamic response, and the difference between 'M/T method' relative error is small.
Mentioned above all sorts of speed measuring method error analysis are established on the basis of the encoder pulse width is uniform.
The manufacturing of the encoder and ordinary deviation in 0.
About 5%, if not handled, will greatly influence the speed measuring precision.
Comparison analysis of all kinds of the commonly used the principle of speed measuring method based on photoelectric encoder, the relative error, dynamic response is proposed on the basis of a new kind of high precision speed measuring method.
Through the corresponding hardware and software design makes the new method of speed in speed measuring precision and the relative error and similar 'M/T method', and well solve the 'M/T method' in the period of slow dynamic response at low speed.
For encoder pulse width inhomogeneity problems, using linear least square method according to the previous rate of n points to predict the current value method, the speed measuring precision is improved.
Based on m measured speed point before the slope is obtained by using the linear least squares fitting of measuring acceleration method is simple and practical, and can get high accuracy of measurement.