JPS61259172A - Speed detection system - Google Patents

Abstract

PURPOSE:To detect a speed in a wide speed range from a low speed to a high speed with good accuracy, by using a speed detector for outputting two sine wave signals which have phases different by 90 deg. to each other and of which the frequencies are proportional to the speed of a rotor or moving body. CONSTITUTION:A motor 5 has an encoder 6 mounted to the motor shaft thereof and two sine wave signals, which have phases different by 90 deg. to each other and of which the frequencies are proportional to speed of rotation, are outputted from said encoder 6. As the number of rotations of the motor 5 becomes larger, the pulse interval of rectangular wave pulses becomes small and the frequency dividing ratio of a frequency divider 18 changes and a counter 25 is constituted so as to count a clock pulse fC applied at a pulse interval T1 at first but to be capable of subsequently counting the clock pulse fC applied at a two-pulse interval T2 to prevent the lowering in measuring accuracy due to the lowering in a count time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a speed detection method for detecting the speed of a rotating body or a moving body. This invention relates to a speed detection method using a sine wave encoder that outputs two sine wave signals having a frequency proportional to the speed of the body and having a phase difference of 900 degrees.

[Conventional technology]

FIG. 5 is a general configuration block diagram when all motor speed control is performed. In the figure, (1) is a servo amplifier, (2
) is a drive unit that controls the power given to the motor (3) based on the output from the servo amplifier (1), and (4) is an analog drive unit that is attached to the motor shaft of the motor (3) and that corresponds to the rotation speed. 'It is a speed detector like a tacho generator that outputs bottom pressure vrbk.

The speed control circuit configured as described above controls the speed of the motor (3) so that the analog bottom pressure vfb from the speed detector (4) becomes a constant value corresponding to the speed setting bottom pressure vref.

By the way, recently, an optical encoder that outputs a pulse train signal or a magnetic encoder using a Hall element or the like has come to be used as the speed detector (4) instead of the l-cosienerator.

FIGS. 6 and 7 are waveform diagrams for explaining a detection method when an encoder that outputs a pulse train signal is used as a speed detector. In FIG. 6, Ca) is the pulse train signal from the speed detector, and (b) Vi shows the sampling period. In the method shown in FIG. 6, the total speed is measured by counting the number of pulses N during sampling of the pulse train signal lxΔtr=t2-1, ). That is, if the pulse a from the speed detector output per one rotation of the motor is M, then the motor rotation speed n is n=-(r, p, s) Δt-M.

In FIG. 7, (a) is the pulse train signal from the speed checker, and (C) is the repetition period T of this pulse train signal.
This is the time span that indicates. Further, (d) shows a clock pulse with a period To output from a crystal oscillator or the like. The method shown in FIG. 7 counts by the pulse period Tt of the pulse train signal - the clock pulse fc, the pulse period Tfl,
What about the count of clock pulses during this period? If LQ, then T = 'ro X tz (1).

[Problem that the invention seeks to solve]

In each of these conventional methods, when the speed becomes low, the number of measurement pulses between Δ decreases or disappears, so it is necessary to increase Δt.
If Δ is made larger, there is a problem that the responsiveness deteriorates.

Furthermore, in the system shown in FIG. 7, the period T becomes extremely small during high-speed rotation, and the resolution deteriorates unless the frequency of the clock pulse fc is extremely high. Furthermore, at low speeds, there is a problem that the period T becomes large and the responsiveness deteriorates.

The present invention was made to solve these problems in the conventional method, and its purpose is to provide a speed detection method that can perform speed detection with good accuracy over a wide speed range from low speed to high speed. It's a book.

[Means for solving problems]

The present invention, which solves the above-mentioned problems, uses a speed detector that outputs two sinusoidal signals having a phase difference of 900 degrees from each other and a frequency proportional to the speed of the rotating body or moving body, When the speed is below a predetermined speed, the amount of change in the sine wave signal during a certain sampling period is measured, and when the speed is above the predetermined speed, the pulse interval of the pulse train signal obtained by shaping each of the two sine waves is changed from 1 pulse interval to 1 pulse interval depending on the speed. The clock pulses are measured up to a plurality of pulse intervals, and the clock pulses between them are measured.

This allows highly accurate speed detection over a wide speed range.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. Figure 1 shows a device that implements the method of the present invention! It is a R configuration block diagram. Here, gold is shown when detecting the rotational speed tk of the motor (5).

An encoder (6) is attached to the motor shaft of the motor (5), and as shown in Fig. 2 (a), the encoder (6) has a phase difference of 906 degrees and its frequency is proportional to the rotation speed. It outputs two sine wave signals SIN A and 5INB. The operational amplifier (8) manually adds the two sine wave signals SIN A and SIN B from the encoder (6), and generates the sine wave signal SIN A as shown in equation [1]. A sine wave signal 5INCt- having a phase difference of 450 with respect to the output signal 5INCt- is output.

This sine wave signal SlNCt-11g2 is shown by a broken line in Figure (a).

This sine wave signal SIN C is waveform-shaped by a Schmitt circuit α to obtain a rectangular wave signal PHAt- as shown in FIG. 2(c).

The operational amplifier (9) and αO each receive a sine wave signal SI
Input N A and SIN B and convert them as shown in Figure 2 (
As shown in b), 711X k 1M M SIN A
, SIN B and D') o Top Nose '9M nE device (6) generates a sine wave signal SIN A and an inverted signal SIN B
is input, both signals are added, and a sine wave signal SIN D t- having a phase difference of 90' with respect to the sine wave signal SIN C is outputted as shown in equation [2].

= S engineering N (C+7-)゛゛°゛°scream °゛°old-°-[2
1 This sine wave signal SIN D! It is shown by the wavy line in Fig. 2(b).

This sine wave signal SIN D is waveform-shaped by a Schmitt circuit (to) to obtain a rectangular wave signal PHB as shown in FIG. 2(c). Here, the square wave signals PHA and P
As is clear from FIG. 2(c), there is a phase difference of 900 with respect to HB.

A logic circuit α4 including a differentiation circuit inputs these two rectangular wave signals PHA and PHB, and uses the differential signals of rising and falling edges and their logic to produce the results shown in FIG. 2(e) and (
A forward pulse train signal dP and a reverse pulse train signal δN as shown in f) are obtained. Rectangular wave signals PHA, PHB are added to the forward rotation pulse train signal δP and the reverse rotation pulse train signal δN.
and the inverted signal PHA.

If the signal obtained by completely differentiating Pi(B is denoted by δ), it is expressed by equations [3] and [4].

δP=(PHA)・(PHB)−δ(PHA)+4
PHA)・rp■B)ψδ(before)trPl(A)−(here)kaiδ(PHA)ten(A)(PH8)→+÷←・δ(P
HB) ・・・・・・・・・・・・[6] δN=(P
Hsu)・rpHn)Fist δ(菰)Ju(PHA)Fist(PHB)
)・δ(PHB) + (PHA)・(before) δrP
HA, )+(PHA)・(PHB)・d(PHB
) ·····song···············〔
4] Counter 4 (to) calculates this forward rotation pulse train 1 word δP and reverse rotation pulse train signal δN,! :t-by hand and counting this for a predetermined sampling time ΔtI7) to obtain the speed vt-.

When the rotation speed of the motor (5) becomes low, pulses to be counted may not be generated during the predetermined sampling time Δt. In this case, the X invention uses the analog value of the sine wave signal. At +7, the analog multiplexer receives each cosine wave signal SIN A.

SIN B, SIN A, SI+'J B, each square wave No. 18 P) (A, PHB is fully powered, and each square wave signal PHA, PL (H) produces one of the sine waves as follows Select the signal and output SINE.

(PHA) (5INBt when PI(B) = 1
-Selection (PT(A)(PFrB)=1 when 5rNA
@Selection As a result, a signal SINE as shown in FIG. 4 (rd) is obtained from the analog multiplexer αQ.

Sample and hold circuit (1!1c, output from analog multiplexer a6) N g 'k, as shown in Figure 6, samples and holds at a predetermined sampling time tt, I2, and outputs the value AI + A2 to A/D. Apply the transformer ■ to the microcomputer (CP[J) @.

The CPUI 21 controls the applied sample hold Ili
From A rA2, the moving spear θ at the time Δt (=t2-t,) is calculated with reference to the sine wave table stored in the ROM+27), and the speed v is obtained from the formula [5].

θ V=□ ・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・ [5] Δt In addition, when Δ is large in time (if the speed V is fast), the counted value on the counter is [5]
By combining the calculation result of the formula, speed detection is performed with high accuracy.

For example, if A/D conversion is performed using a SIN E k 8-bit A/D converter, and the number of pulses generated from the encoder (6) to one rotation of the motor (5) is δP and δN is 1024 pulses. , isometrically 1024x2
56=262144 pulses/rev high resolution encoder. As a result, speed detection at low speeds can be performed with higher accuracy than the conventional method shown in FIG. Due to the problem of the bandwidth of the operational amplifier, highly accurate detection cannot be expected. Therefore, in the present invention, the following detection method is adopted when the sieving speed is high.

FIG. 4 is an operational waveform diagram for explaining the entire detection method at high speed. The gate circuit a25 inputs the forward rotation signal δP and the reverse rotation pulse δN from the logic circuit α,
One of the measurement pulses is selected by the direction command signal P/H outputted from the output port (CPU +29 via 2υ).

The frequency divider OF1 inputs the pulse from the gate appositive white η,
This is determined by the value output from Kanayama Kapo-1+20,
According to the predetermined division ratio, a pulse signal having a width T1 as shown in Figure 4 (c) or a pulse signal having a time width T2 as shown in Figure 4 (d) is output.

The flip-flops receive the command signal 5 from the CPU
A54PT and time width T from the frequency divider section! Synchronize with the pulse signal of a certain time width T2, and gate!
2,1. A clock pulse having a frequency fc as shown in FIG. 4 ra) is applied to the counter through C'4).

In this way, the counter 1251 shows that as the speed increases, that is, as the pulse interval of the rectangular wave pulse shown in FIG. 4(b) decreases, the frequency division ratio in the frequency divider Oa changes. Initially, 8 is applied at one pulse interval Tl.
As shown in Fig. 4 (e), the lock pulse fcf that was being counted is now applied at the 2-pulse interval T2! @4
Figure rf) [As shown in Figure 7, lock pulses fc can be counted, and the measurement accuracy is prevented from decreasing due to a decrease in counting time (due to narrower pulse intervals) as in the conventional method shown in Figure 7. ing.

In the above explanation, the counting time of the counter (2) is changed in two steps, that is, the one-pulse interval TI and the two-pulse interval T2, but it may be further changed up to a plurality of pulse intervals.

In addition, CPU (to) is the count value of counter υ, A/D
The signal from the converter 4 and the count value of the counter □□□ are respectively input, and the optimum detection method is adopted depending on the speed of the motor (5), and a predetermined calculation is performed to obtain a speed signal.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to realize a speed detection method that can perform highly accurate measurement over a wide speed range from low speed to high speed.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the configuration of a device that implements the method of the present invention, Figures 2 (ra) to rf), Figures 3 and 4 (a).
~(1> is an operation waveform diagram for explaining the operation, fifth
The cause is shown in the groove bottom block diagram of the motor speed control circuit, Figure 6 (
a), (b) and Figure 7 (a), (c), f'd
) is an operating waveform diagram of the conventional method ^ (5)...Mo4 (6i...Encoder (8L (9), Od...Encoder
q4...Logic circuit (IQ...analog multiplexer 0 seconds...minutes? M'1% (to)...sample hold circuit +1...A/D variation f15L 3αB,
r, 151... Kara 74 @-CPU agent Patent attorney Masaru Sato Figure 2 Figure 3 8t*t2-f. Figure 4 (a) JPHA (Da 11 Okita) (f) Figure 5 pulse t, tg Figure 7

Claims (1)

[Claims] It is equipped with a speed detector that outputs two sine wave signals with a 90° phase difference from each other and a frequency proportional to the speed of the object to be measured, and when the speed of the object to be measured is below a predetermined speed, the sine wave signal of a certain sampling period is output. The amount of change in the wave signal is determined and the speed is determined from this amount of change, and when the speed is greater than a predetermined speed, the
The pulse interval of the pulse train signal obtained by shaping each of the two sine wave signals is set to one pulse interval to multiple pulse intervals depending on the speed, and the speed is determined by measuring the number of clock pulses in this pulse interval. A speed detection method characterized by: