JPH0412429B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital speed detection device that detects the speed of a rotating machine using a two-phase incremental rotary encoder directly connected to the shaft end and generates a speed signal.

Conventionally, there has been a digital speed detection device of this type as shown in FIG. FIG. 2 is a waveform diagram of the main part of FIG. 1. In FIG. 1, reference numeral 1 denotes a rotational direction determining circuit which inputs an output signal from a rotary encoder (not shown) and determines the rotational direction of a rotary body, and 2 a transmitter circuit which generates a clock signal C. 3 is a timing circuit which receives the A signal from the rotary encoder and the clock signal C and generates an output signal M. Reference numeral 4 denotes a latch and reset pulse generating circuit which generates a signal R based on the signal M and the clock signal C. 5 is a speed detection pulse counter, which is a pulse signal M within the pulse period Ts of the signal R.
Count. 7 is a first buffer circuit, and 8 is a second buffer circuit.

Next, the operation of the conventional circuit shown in FIG. 1 will be explained with reference to the waveform diagram of the main part shown in FIG. The input terminals A and B of the rotation direction discrimination circuit 1 are connected to the input terminals 2 detected by a rotary encoder as shown in FIG.
A phase waveform is input. When the output signal from the rotation direction discrimination circuit 1 receives the two-phase wave, it outputs a binary output signal D of "1" or "0" depending on the rotation direction of the rotating body. Further, a timing circuit 3 which receives the clock signal C of the transmitting circuit 2 and the output signal A of the rotary encoder as input signals outputs the signal M when the pulse generated at the rising edge of the signal A coincides with the pulse generation timing of the clock signal C. is output. Therefore, the M signal and the clock signal C
The signal R is output from the latch and reset pulse generation circuit 4 as shown in the figure, and when the generation period of the signal R is Ts, the speed detection pulse counter 5 outputs the signal R as shown in the figure.
Count the signal M within the Ts period and output the signal P,
It is reset at the falling edge of signal R. The clock pulse counter 6 receives the clock signal C within the synchronization period Ts.
It counts and outputs the signal N, and is reset at the falling edge of the signal R. Of the output signals N of the clock pulse counter 6, the Nd signal generated by Nn is applied to the latch and reset pulse generation circuit 4 which receives both the signal M and the clock signal C as inputs to set it to "1" or "0". A reset signal is transmitted, and if the signal Nd is "1", a signal R synchronized with the signal M is output. However, the pulse width of the signal Nd is given by a pulse signal outputted from the output signal of the clock pulse counter 6 at a preset count value n. The first and second buffer circuits 7 and 8, which have latch and buffer functions, latch the signals P, D, and N at the rising edge of the signal R, and output "H" or "L" digital speed signals to their respective outputs. do.

In the above speed detection method, since the signal M and the signal R are synchronized after the signal N reaches the output signal level n of the clock pulse counter 6 (after Nd becomes "1"), the pulse interval of the signal R is Ts. During the period of , the signal N has Ns (for threshold level n, n
The number of pulses Ns) is counted, and P _S (the output signal of the speed detection pulse counter 5 at nN) is counted in the signal P during the synchronization period of the signals M and R. In this case, the calculation result Sf of the rotating body speed S is expressed as Sf=KPs/Ns (K=constant). The above calculation is performed in a circuit other than that shown in FIG. 1 by reading the "H" and "L" output signals of the first and second buffer circuits 7 and 8. That is, as shown in Figure 3, when the speed S changes from normal rotation to reverse rotation at point a, the signal D changes from "1" to "0" at point b.
The subsequent control data is processed as reverse, but the signal D is switched to during the pulse period of the signal R.
It is clear that the Tsd period when the switch is not the speed detected by the original encoder, and the speed calculated by the signal Nsd during this Tsd period
Sfd is Sfd=KPsd/Nsd, which is not normal speed detection data.

Since the conventional speed detection method is configured as described above, abnormal data may be generated when the rotation direction of the rotating machine is switched from normal rotation to reverse rotation, which may cause control problems.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it focuses on the fact that the control data before and after the abnormal data when the rotation direction is reversed is normally detected. It is an object of the present invention to provide a digital speed detection device that can reliably obtain speed detection data proportional to a change in rotational speed even when switching from normal rotation to reverse rotation.

An embodiment of the present invention will be described below with reference to the drawings. In FIGS. 4 and 5, the same parts as in FIGS. 1 to 3 are designated by the same reference numerals. In FIGS. When the signal Nd is "1", a signal Ra is generated in synchronization with the signal M, and a signal R is generated with a slight delay from the signal Ra. 9 uses the signals D and Ra as input signals, and the signal D changes from "1" to "0" or "0".
After changing from 1 to 1, when signal Ra is input, only one pulse synchronized with signal Ra is output.
A speed detection pulse counter reset circuit outputs to Rb. 5a is a speed detection pulse counter that counts the signal M within the pulse signal period Ts of the signal R. The count value of the signal M is output to the signal P and is reset at the fall of the signal R. In addition to this, when the pulse signal of the signal Rb is input, the function of resetting the output signal P is activated with priority.

Next, the operation of the present invention will be described with reference to FIGS. 4 and 5, taking as an example the case where the rotational direction of the rotating body changes. First, FIG. 5 shows the circuit operation in FIG. 4 at the same time as in FIG. 3. When the signal D changes from "1" to "0" at point b within the Tsd period,
The signal Rb is generated at the end of the Tsd' period, and the speed detection pulse counter 5a counts the pulses of the signal M and outputs "1" to the signal P. However, the signal Rb resets the pulse of the signal M and outputs "1" to the signal P, and the signal P becomes "0". Become.
Therefore, after the signal Rb is generated until the next signal Ra is generated, the detected speed Sfd is Sfd = KPsd / Nsd = 0 (however, Psd = 0), and "0" is always detected at the time of switching. Ru.

Therefore, forward rotation is detected in the period before the detection period Tsd, and reverse rotation is detected in the period after the detection period Tsd, and the actual speed is closer to "0" than the values before and after the detection period Tsd. It is expected that the value of
Considering the limitations of low speed detection that are usually said to occur when a rotary encoder is used, it can be said that it is extremely appropriate to approximate the speed at the switching point to "0".

As described above, according to the present invention, the circuit configuration is such that the rotation direction detection signal is once forcibly reset to "0" at the switching point between forward and reverse rotation in the speed detection method of a rotating body using a rotary encoder. Therefore, there is an excellent effect that a value extremely close to the actual speed can be reliably obtained as a speed detection signal not only during rotation but also when switching the rotation direction.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram showing an example of a conventional digital speed detection device, FIGS. 2 and 3 are signal waveform diagrams of the main parts of FIG. 1, and FIG. 4 shows an embodiment of the present invention. FIG. 5 is a block diagram of the digital speed detection device, and FIG. 5 is a signal waveform diagram of the main part of FIG. 4. DESCRIPTION OF SYMBOLS 1... Rotation direction discrimination circuit, 2... Transmission circuit, 3... Timing circuit, 4, 4a... Latch and reset pulse generation circuit, 5, 5a... Speed detection pulse counter, 6... Clock pulse counter, 7... First buffer circuit , 8...Second buffer circuit, 9...Speed detection pulse counter reset circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1 A rotary encoder that generates the rotation speed of a rotating body as a two-phase pulse signal with a phase difference of 90 degrees, a rotation direction determination circuit that determines the rotation direction based on the two-phase pulse signal of the rotary encoder, and a rotation direction determination circuit that determines the rotation direction from the two-phase pulse signal of the rotary encoder, a timing circuit that generates a signal synchronized with a one-phase pulse signal; a latch and reset pulse generation circuit that generates a signal at predetermined intervals synchronized with the output pulse of the timing circuit; and a latch and reset pulse generation circuit that counts the pulse signal of the timing circuit. a speed detection counter that is reset by a signal generated by the latch and reset pulse generation circuit;
a speed detection pulse counter reset circuit that forcibly resets the count value of the speed detection counter to zero when the discrimination signal of the rotation direction discrimination circuit is inverted;
A digital speed detection device comprising: a circuit for calculating the rotational speed of the rotating body based on the count value of the speed detection counter.