JP2963019B2 - Speed detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed detecting device used in a motor control device and the like having improved accuracy and response of speed detection particularly in a low speed range.

[0002]

2. Description of the Related Art A description will be given with reference to FIGS. FIG.
Denotes a conventional example, wherein 1 is a pulse encoder, 2 is a rotating body, 3 is a quadruple circuit, and 4 is a speed calculator for one pulse. FIG. 4 shows an example of the relationship between the pulse encoder and the quadrupled pulse. That is, the pulse encoder 1 is directly connected to the rotating body 2, and the output of the pulse encoder 1 is a three-phase rectangular wave having a frequency proportional to the rotation speed of the rotating body 2.
The quadruple circuit 3 receives the two-phase rectangular waves A and B of the output of the pulse encoder 1 and generates pulses at the rise and fall of each waveform as shown in FIG. Is output.

Further, the one-pulse speed calculator 4 performs a calculation as shown in equation (1) from the output of the quadrupler circuit 3 and outputs a signal. Nm1 = Gn / (Tm-Tm-1) (1) That is, the time between each pulse of the output of the quadruple circuit 3 is detected, and the reciprocal thereof is calculated. , The average speed of the rotating body 2 between each pulse is obtained. Here, Gn is a conversion gain, T
m-1 is the pulse time one pulse before the pulse time Tm, and Nm1 is the average speed from the pulse time Tm-1 to the pulse time Tm.

FIG. 3 shows another conventional example, and reference numeral 5 denotes a 4-pulse speed calculator. That is, in FIG.
A four-pulse speed calculator 5 is used in place of the one-pulse speed calculator 4 in FIG. 2, and this four-pulse speed calculator 5 has a four-multiplier circuit 3 output 4 as shown in FIG.
The time for the pulse is measured, the reciprocal thereof is calculated, and the average speed of the rotating body 2 during four pulses is obtained and output. The calculation is represented by equation (2). Nm4 = 4Gn / (Tm-Tm-4) (2) where Nm4 is the average speed from the pulse time Tm-4 to the pulse time Tm.

[0005]

In this type of prior art, the duty ratio of the rectangular wave output from the pulse encoder is not completely 50%, and even if the rotating body is rotating at a constant speed, for example, ( Tm−2−Tm−4) and (Tm−Tm−)
2) and (Tm-1-Tm-3) are not necessarily equal to (Tm + 1-Tm-1). The phase difference between the rectangular wave A and the rectangular wave B is not necessarily 90 degrees. Thus, even if the rotating body is rotating constantly, the time between each pulse is not equal. Therefore, the output of the speed detecting device shown in FIG. 2 is not a constant value, and furthermore, the speed detected value has a ripple. The speed cannot be detected correctly. In addition, the speed detection device shown in FIG. 3 calculates the average speed between four pulses, and there is no speed detection error due to the shift in the duty ratio or the shift in the phase described above. The complete detection can be made after four pulses after the speed has changed, and thus the detection response becomes slow. Accordingly, it is an object of the present invention to provide a high-accuracy, high-speed response speed detection device free from the influence of the duty ratio and phase shift of such a pulse encoder.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and the means for solving the problems are as follows. (1) A pulse encoder that outputs a two-phase rectangular wave at a frequency proportional to the rotation speed of a rotating body, a quadruple circuit that inputs a pulse encoder output and outputs a pulse whose frequency is quadrupled, and a quadruple circuit A correction coefficient storage device for storing four correction coefficients in a speed detection device having a one-pulse speed calculator for detecting a rotation speed of a rotating body by measuring a time between output pulses and calculating a reciprocal thereof. And a phase discriminator for inputting a two-phase rectangular wave of a pulse encoder output and discriminating into four phases, and a correction coefficient selector for selecting and outputting four correction coefficients in a correction coefficient storage unit with the phase discriminator output And a compensator that computes and outputs the rotation speed of the rotating body corrected based on the rotation speed of the one-pulse speed calculator output and the correction coefficient of the correction coefficient selector output.

(2) Further, a four-pulse speed calculator for detecting the rotation speed of the rotating body by measuring the time for four pulses of the output of the quadruple circuit and calculating the reciprocal thereof;
A correction coefficient calculator for calculating the correction coefficient by inputting the output of the pulse calculator between pulses and the output of the speed calculator between pulses, and outputs the output of the correction coefficient calculator to the correction coefficient memory selected by the output of the phase discriminator. And a correction coefficient setting device. (3) Further, the automatic measurement setting device which automatically measures the electrical constants and mechanical constants of the rotating body and sets the correction coefficient setting device as a driving device for driving the rotating body is operated. It is made to operate when it is.

[0008]

As mentioned above, the duty ratio and the phase shift of the output waveform of the pulse encoder hardly change in each cycle of the output waveform of the pulse encoder, as pointed out in the above-mentioned problem. Here, as shown in FIG. 4, from the four phases P1 to P4 determined by the state of the rectangular waves A and B of the pulse encoder output, for example, the time of the same phase P1 is (Tm−3−Tm−4). ) And (Tm + 1 -T
m) will be equal if the rotation speed is constant.

That is, since the speed detection error due to the duty ratio and the phase shift depends on the phase P1 to the phase P4, the corrected average speed Nam using the correction coefficient Kx corresponding to each phase is expressed by the following equation (3). ), The average speed Nm1 obtained by the equation (1) can be corrected. Nam = Nm1 (1 + Kx) (3) where the correction coefficient Kx is the correction coefficient K1, K2, K3, K
4 corresponding to the phases P1 to P4. In this manner, the phase discriminator discriminates the phases P1 to P4 from the output waveform of the pulse encoder and sets it as Px. The correction coefficient selector selects one of the correction coefficients K1 to K4 corresponding to the discriminated phase Px. One of them is selected and output as Kx, the equation (3) is calculated by the corrector, and the corrected average speed Nam can be output as a speed detection value.

Then, the correction coefficient Kx is calculated by using the equation (3) as Kx
Can be obtained from the equation (4) solved by Kx = Nbm / (Nm-1) (4) Here, the average speed Nbm must be an actual speed.
The speed detected by the speed calculator between four pulses may be used as in a circuit. The time between the four pulses corresponds to one cycle of the square wave before being multiplied by four, and the speed calculator between four pulses has no influence on the duty ratio or the phase. Equation (4) is calculated by the correction coefficient calculator, and the correction coefficient storage is selected by the output of the phase discriminator in the correction coefficient setting unit,
Obviously you can set it.

It is not necessary to set the correction coefficient at all times. For example, an automatic measurement for automatically measuring an electric constant or a mechanical constant of the rotating body and setting the same in a driving device for driving the rotating body. When the setting device is operating, the correction coefficient setting device may be operated at the same time to store and set the four correction coefficients. Thereafter, high-accuracy speed detection can be performed without changing the correction coefficient. In addition, the speed detection is accurate during one pulse, and the speed detection response is of course faster than the speed detection during four pulses. The present invention will be further described by way of examples.

[0012]

FIG. 1 shows a main part of an embodiment of the present invention in a manner similar to FIGS. 2 and 3, wherein 6 is a phase discriminator, 7 is a correction coefficient storage, and 8 is a correction coefficient selector. , 9 is a compensator, 10
Denotes a correction coefficient calculator, 11 denotes a correction coefficient setter, and 12 denotes a switch. In FIG. 1, a pulse encoder 1, a rotating body 2,
The connection configuration consisting of the quadruple frequency multiplier 3 and the inter-pulse speed calculator 4 is the same as the circuit in FIG. Further, a 4-pulse arithmetic circuit 5, a phase discriminator 6, a correction coefficient memory 7, a correction coefficient selector 8, a corrector 9, a correction coefficient calculator 10, a correction coefficient setter 11, and a switch 12 are provided and connected. It has been done. The operation of such a connection configuration is as follows.

That is, the pulse encoder 1 includes the rotating body 2
The output is a two-phase rectangular wave having a frequency proportional to the rotation speed of the rotating body 2. The quadruple circuit 3 receives the rectangular waves A and B output from the pulse encoder 1 and outputs a pulse whose input frequency is quadrupled. The one-pulse speed calculator 4 outputs the average speed Nm1 according to equation (1). The phase discriminator 6 receives the rectangular waves A and B and outputs a phase Px based on the states. Correction coefficient selector 8
Selects a correction coefficient in the correction coefficient storage 7 according to the phase Px, and outputs it as a correction coefficient Kx. The correction coefficient Kx is input to the corrector 9 and is output as a signal using the corrected average speed Nam as a speed detection value according to equation (3).

When the correction coefficient Kx is set and stored, the switch 12 is turned on and the four-pulse speed calculator 5 calculates the equation (2). The output Nm1 is set to Nbm, and the equation (4) is calculated. And the correction coefficient Kx
Is required. It is set and stored in the selected correction coefficient storage unit 7 via the correction coefficient setting unit 11.

[0015]

As described above, according to the present invention, even if the pulse encoder has a duty ratio or phase shift, the speed can be detected with high accuracy without delaying the detection response, and can be applied to a wide range of fields. The practical effect is remarkable.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional example.

FIG. 3 is a block diagram showing another conventional example.

FIG. 4 is a waveform diagram showing an example of a relationship with a quadrupled pulse of a pulse encoder.

[Explanation of symbols]

 Reference Signs List 1 pulse encoder 2 rotator 3 4 multiplication circuit 4 1-pulse speed calculator 5 4-pulse speed calculator 6 phase discriminator 7 correction coefficient storage 8 correction coefficient selector 9 corrector 10 correction coefficient calculator 11 correction coefficient setting 12 Switch A Square wave B Square wave Nm1 Average speed Nm4 Average speed Nam Average speed Nbm Average speed

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) G01P 3/44-3/495 G01P 5/245 H02P 5/00

Claims (2)

(57) [Claims] 1. A pulse encoder that outputs a two-phase rectangular wave at a frequency proportional to the rotation speed of a rotating body, a quadruple circuit that receives the pulse encoder output and outputs a pulse whose frequency is quadrupled, A speed detector comprising an inter-pulse speed calculator for measuring a time between pulses of the output of the quadruple circuit and calculating a reciprocal thereof to detect a rotation speed of the rotator; A storage unit that has an automatic measurement setting device that automatically measures a mechanical constant, and stores correction coefficients corresponding to four phases in one cycle of the pulse of the pulse encoder output when the automatic measurement setting device is operating; Determining means for obtaining the pulse encoder output to determine four phases; selecting means for selecting and outputting a correction coefficient of the storage means based on the output of the determining means; A speed detecting device comprising: a correcting means for calculating and outputting a rotating speed corrected based on the rotating speed and a correction coefficient of an output of the selecting means. 2. A four-pulse speed calculator for measuring a time corresponding to four pulses of the output of the quadruple circuit, calculating a reciprocal thereof, and detecting a rotation speed of the rotating body, and an output of the four-pulse speed calculator. And a correction coefficient calculator for inputting the inter-pulse speed calculator output and calculating a correction coefficient, and a correction coefficient setter for outputting the correction coefficient calculator output to the storage means selected by the discriminating means output. 2. The speed detecting device according to claim 1, wherein the speed detecting device is provided.