Speed acquiring method based on communication encoder

Abstract

The invention discloses a speed acquiring method based on a communication encoder, comprising the following steps: a, whether the pulse number of angular displacement in a speed measurement period issmaller than a preset pulse number threshold or not is judged; b, if the pulse number of angular displacement in a speed measurement period previous to a current speed measurement period is smaller than the preset pulse number threshold, the pulse number N.M of angular displacement in the current speed measurement period is predicted according to the rotating speed and the acceleration of the previous speed measurement period; c, the period duration Tcnt of one pulse number is calculated; d, timing is started at the starting moment of the current speed measurement period, the timing duration is Tcnt*N, counting is carried out by using counting pulses at the end of timing, and the count value of the starting moment of a speed measurement period next to the current speed measurement period is recorded; and e, the rotating speed Vel of a rotating object detected in the current speed measurement period is calculated. The method can improve the speed measurement precision.

Description

technical field [0001] The present invention relates to speed acquisition technology. Background technique [0002] Communication encoders have been widely used in motion control systems due to their easy wiring and high resolution. Since the communication encoder lacks the pulse edge of the pulse type (ABZ type) encoder, it is difficult to use the T method to measure the speed, so the M method is generally used for speed detection. The angular displacement is obtained by differential calculation. In general, the angular displacement of the motor rotor in the speed measurement cycle is obtained by the difference between the two readings of the encoder, and the speed measurement cycle is obtained by using the speed loop cycle or the time difference between the two readings of the encoder. [0003] figure 1 The principle of the existing speed acquisition method based on a communication encoder is shown. The method uses the following formula to calculate the average rotation...

AI Technical Summary

Problems solved by technology

[0007] 1. The delay t between the moment when the CPU reads the program instruction and the start moment of the request frame sent by the CPU to the communication encoder offset1 There is time jitter;

[0008] 2. The delay t between the start time of the request frame sent by the CPU to the communication encoder and the start time of the return frame received by the CPU from the communication encoder offset2 There is time jitter;

[0009] 3. When the motor runs at low speed, the speed measurement period is very short or the resolution of the communication encoder is low, ±1 pulse has a great influence on the average speed, or the value of the encoder does not change within a sampling period, resulting in The average speed is 0, and it becomes a sudden change in speed

[0010] due to t offset1 and t offset2 Uncertainty, so the P used to calculate the speed Vel 2 -P 1 and T 2 -T 1 There are jitters in both, which will cause the speed calculation results to be inaccurate

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