JPS63179260A - Speed detecting method - Google Patents

Abstract

PURPOSE:To correctly detect the rotating speed of a rotary body by counting forward or backward rotation pulses from a rotary encoder arranged coaxially with a motor and correcting said pulses according to positive or negative variation in the sign of the incremental number of pulses. CONSTITUTION:The rotary encoder 12 is arranged on the rotary body 11 and an A-phase signal SA and a B-phase signal SB having a phase difference are outputted by the forward or backward rotation. Then a pulse generating circuit 13 outputs a positive pulse AP with the signal SA or backward pulse BP with the signal SB, and the forward and backward pulses are inputted to and counted by a forward-side counter 14 and a backward-side counter 15. A computer 18 finds the incremental number of pulses from the last read to a current read. Further, the incremental number of pulses is increased by one when the sign of the incremental number of pulses varies from positive to negative or decreased by one when the sign varies from negative to positive, thus making corrections. The speed of the rotary body is computed from the corrected incremental number of pulses and a pulse read time. Thus, corrections are made according to variation in the sign of the incremental pulse number, so the speed is accurately detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of detecting the speed of a rotating body from the output of a rotary encoder disposed coaxially with a motor.

(Prior art) Figure 2 is a block diagram of a device that detects speed using this type of speed detection method, and Figures 3 (a) and (b) are time charts of Figure 2 during forward rotation and reverse rotation, respectively. , FIG. 4 is a time chart for explaining the speed detection method.

A-phase signals SA and B that have a phase difference due to the rotation of the rotating body 11
A phase signal SR is output from the rotary encoder 12. The pulse generation circuit 13 generates an A-phase signal SA and a B-phase signal SB.
Due to the phase relationship, as shown in Figure 3 (a), during forward rotation, a positive pulse AP is output at the rising edge of the A-phase signal SA, and during reverse rotation,
As shown in FIG. 3(b), a reverse pulse BP is output at the falling edge of the A-phase signal SA. The positive pulse AP and reverse pulse BP are up-counted by a positive counter 14 and a reverse counter 15 at the next stage, respectively. At the same time, the T timer 16 is reset by the logical sum of the positive pulse PA and the reverse pulse PB by the logical sum circuit 17. When the T timer 16 is reset, the count value becomes 0, and after the reset is released, the T timer 16 counts the time again and performs an up-count operation until the next reset. The microcomputer 18 reads the values of the forward counter 14, reverse counter 15, and T timer at predetermined intervals, and calculates the speed f (Hz) as shown in the following equation. "Δ" in FIG. 4 is the counter 14 of the microcomputer 18.
．． 15 and T timer 16 are read.

f = ((NP, .NP, .-1) (-NRnNR
n-+)) / (T+ T, -1-Tn) = ΔN
/T.

Here, f: Speed (,z) NF, n: Current count value N of the positive side counter 14
P. -1: Previous count value NR of positive side counter 14
, n: current count value NR of the opposite side counter 15,
n-1: Previous count value of the opposite side counter 15 To: Reading time of the microcomputer 18 from generation of pulse (current value) Tn-1: Same as above (previous value) ΔN = Counted from previous reading to current reading Incremental pulse number (positive pulse is +) T: Pulse AP output at time T.

The time T from the pulse APN outputted at time Tn, , to the previous T timer 1 of the second microcomputer 18
6. Time from the reading point of the counter 14.15 to the current reading point of the T timer 16 and the counter 14.15 [Problem to be solved by the invention] In the conventional method described above, the case shown in FIG. Considering that, when the previous incremental pulse ΔNn -1 is positive and the current incremental pulse number ΔNn is -1, T, α0, and therefore the speed 1f+ becomes much larger than the actual speed. this is,
This is because although the forward pulse AP' and the reverse pulse BP' occur at different times as pulses, they occur at the same position as position signals, so speed cannot be detected using the time passing between these two pulses. be.

Needless to say, the above occurs even if the previous incremental pulse number ΔNn-1 is negative and the current incremental pulse ΔN, . . . is +1.

As a conventional measure, when the sign of the incremental pulse ΔN changes, the speed f is forcibly set to O. However, in this method, considering the case shown in FIG. 6, since the incremental pulse number ΔN changes from positive to negative, the speed f becomes 0 even though it is calculated correctly.

An object of the present invention is to provide a speed detection method that correctly detects speed even if the sign of the incremental pulse number ΔN changes.

[Means for solving problems]

In the speed detection method of the present invention, when the sign of the number of incremental pulses changes from positive to negative, the number of incremental pulses is corrected by adding 1, and when the number of incremental pulses changes from negative to positive, the number of incremental pulses is This is a correction that subtracts 1 from .

[Effect]

When the above correction is performed, for example in the case shown in Figure 5, the sign of the incremental pulse number changes from positive to negative.
f-(-1+1)/T+-0, and the speed f never increases. Also, in the case as shown in Fig. 6, f-(
1-3+1)/Tl-17T+, and accurate speed detection becomes possible. In addition, in FIG. 5, when the sign of the incremental pulse number changes from negative to positive, f-(1-1)/TI-
It becomes 0.

In this way, when the sign of the number of incremental pulses changes, the speed can be detected correctly by applying the above-described correction to the number of incremental pulses according to the change in sign.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a flowchart showing an embodiment of the speed detection method of the present invention. Note that FIG. 2 is used as a diagram of the apparatus.

It is assumed that this process is executed using the microcomputer 18 at predetermined intervals.

First, the current values N, , n, NR9°, and Tn of the forward counter 14, reverse counter 15, and T timer 16 are read (step 1). Positive side incremental pulse number (NF, .-NP, .-
1) to the opposite side incremental pulse number (NR, n-NR, n-1)
is subtracted and set as ΔN (step 2). It is determined whether the number of incremental pulses ΔN=O or not (step 3). If ΔN is 20, no speed detection is performed and the process ends.

If ΔN≠0, this ΔN is set as the current incremental pulse number ΔNn, and the current value NF. , NR, and n are the previous values NF, n-1+ NR, n-1, respectively (Step 4)
. Next, the incremental number of pulses ΔNn, ΔNn−1 between the previous time and this time
If there is no change in sign, the number of incremental pulses ΔNr is set to ΔNn゛; if there is a change in sign, proceed to determination of the sign of the number of incremental pulses ΔNn (step 6); If ΔNn>0, subtract 1 from ΔN to obtain ΔNn°. Step 8), Δ
If N, < 0, add 1 to ΔN,
ΔNn' (step 9). Finally, calculate the speed, set it to F, and set the incremental pulse number ΔNn8 time Tn as ΔNn-1+Tn for the next calculation.
-1 (step 10).

(Effects of the Invention) As explained above, the present invention, when the sign of the number of incremental pulses changes, adds 1 or -1 to the number of incremental pulses according to the change in sign, thereby increasing the number of incremental pulses. This has the effect that the speed can be detected correctly even if the sign of changes.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an embodiment of the speed detection method of the present invention, FIG. 2 is a block diagram of a device for detecting the speed of a rotating body from the output of a rotary encoder, and FIG. 3(a)
, (b) is a time chart of the device shown in Fig. 2 during forward rotation and reverse rotation, respectively, Fig. 4 is a time chart for explaining the speed detection method, and Figs. 5 and 6 show problems with the conventional system. This is a time chart for explanation. 1 to 10 - Step, 11 Rotating body, 12 Rotary encoder, 13
... Pulse generation circuit, 14 ... Positive side counter, 15 ... Reverse side counter, ! 6.-T timer, 17.. OR circuit, 18.. microcomputer.

Claims (1)

[Claims] A rotary encoder that outputs two-phase signals having a phase difference as the rotating body rotates, and a rotary encoder that outputs two-phase signals having a phase difference as the rotating body rotates, and from these two-phase signals, outputs a forward pulse when the rotating body is rotating in the forward direction and a reverse pulse when the rotating body is rotating in the reverse direction. A pulse generation circuit that generates , a forward counter and a reverse counter that count forward and reverse pulses, respectively, and a timer that is reset by the logical sum of the forward and reverse pulses and performs an up-count operation until the next reset. Then, read the values of the positive counter, reverse counter, and timer, and calculate the incremental number of pulses from the previous reading to this reading = {(current positive counter count value - previous positive counter count value)
- (count value of the current reverse side counter - count value of the previous reverse side counter)} and the positive pulse or reverse pulse output immediately before the current reading from the positive pulse or reverse pulse output immediately before the previous reading. In a speed detection device that has an arithmetic circuit that calculates the speed of the rotating body by determining the time until the reverse pulse, when the sign of the number of incremental pulses changes from positive to negative, the number of incremental pulses must be corrected by adding 1. A speed detection method that corrects the incremental pulse number by adding -1 when it changes from negative to positive.