JPH04133680A - Rotational speed detector - Google Patents

Abstract

PURPOSE:To realize accurate detection of the fluctuation of instantaneous rotational speed through a single sensor by making the interval of output pulse constant based on each slit in a slit board thereby eliminating detection error due to shifted installation of a rotary encoder. CONSTITUTION:When pulses 4 are outputted repeatedly based on the slits in a slit board 2, time interval between the output pulses is measured by means of a counter 5. Thus measured value is then stored in a memory 6 while corresponding to the slit number. Data stored in the memory 6 is then read out and an operating unit 7 performs operation for making the time interval between the output pulses 4 constant. In other words, total time intervals between output pulses for single revolution of the slit board 2 is divided by the number of slit to obtain an average time interval and then each time interval is divided by the average time interval to obtain a correction ratio. A switch is changed over at the time of next revolution of the slit board and the time interval corresponding to each slit is multiplied by the 'correction ratio' thus producing a signal 9 for making constant the rotational speed of an rotary object 1 to be detected.

Description

[Detailed Description of the Invention] [Summary] Regarding a device for detecting the rotational speed of a rotating object to be detected in order to correct an error with a cycle of one rotation, a rotary encoder with a single sensor is used, and a rotary encoder is used. The encoder is installed with a slit plate coaxially connected to the rotating body to be detected, with the aim of providing a rotational speed detection device for the rotating body to be detected that accurately detects fluctuations in instantaneous rotational speed by eliminating detection errors due to eccentricity, etc. In a device that detects the rotational speed of a rotating body to be detected using the output pulses of a rotary encoder, there is a counter that measures the time between output pulses based on each slit of a slit plate in the rotary encoder, and a memory for storing the value read out from the memory; a correction value calculation circuit for calculating the read value from the memory to make the time between the output pulses constant; and an output correction value of the calculation circuit for outputting the output correction value to the counter. and a correction circuit for correcting the rotational speed of the rotating body to be detected.

[Industrial Field of Application] The present invention relates to a device for detecting the rotational speed of a rotating body to be detected in order to correct an error with a period of one rotation.

It is widely practiced to detect the rotational speed of a rotating body such as in video equipment using a rotary encoder and configure a feedback control loop to suppress rotational irregularities. However, rotary
The rotational speed detected by the encoder includes detection errors due to eccentricity of the shaft when the rotary encoder is attached to the rotating body shaft, so there was a request to develop a simple technology to remove this error.

[Conventional technology]

In rotating bodies such as audio/video equipment and magneto-optical disk devices, fluctuations in instantaneous rotational speed during one rotation, that is, uneven rotation, cause jitter and flutter. Therefore, in order to reduce rotational unevenness, it is widely practiced to configure a feedback control loop to control the rotational speed and suppress rotational unevenness. Only one sensor is used at this time. The rotational speed detected by the rotary encoder includes detection errors due to eccentricity of mounting and slit machining distortion.
If the performance of the feedback control loop is improved, the output pulse period of the rotary encoder becomes constant, but the rotational irregularities of the rotating body will occur just as much as is necessary to cancel out the detection error of the rotary encoder.

The error due to eccentricity of the rotary encoder installation is
In principle, research has been conducted to see if it is possible to offset this by providing two sensors at diagonal positions.

In addition, in a rotary encoder with one sensor, the mounting of the slit plate can eliminate errors due to eccentricity, as disclosed in Japanese Patent Application Laid-open No. 63.
It is described in the publication No.-48658. The contents of this publication can be summarized as follows. The output of one rotary encoder that operates as a sensor includes an error due to eccentricity in the mounting of the slit plate. The average control error between the output of such a rotary encoder and a reference signal is stored over one rotation period as a function of time or rotation angle, and this average signal is subtracted from the control error for each corresponding time or rotation angle. . In this way, the influence of eccentricity of the slit plate is eliminated by controlling the rotation by obtaining an error signal that cancels only the control error synchronized with the rotation. The eccentricity of the rotary encoder's slit plate installation is mechanical and has reproducibility with respect to rotation, so if you remove this from the rotation control error signal, it will prevent random disturbances that are not synchronized with rotation. Only the control that is carried out is valid.

[Invention or problem to be solved]

Detecting the rotational speed with a rotary encoder and suppressing rotational unevenness using a feedback control loop is difficult because the detected rotational speed includes a detection error caused by eccentric mounting. The unevenness will remain. It was necessary to add other means to reduce detection errors.

Although it is theoretically possible to reduce the detection error by using two sensors, the positional relationship between the sensors is delicate and adjustment is difficult.

Next, in the matter described in the above-mentioned patent publication, control is performed only for random disturbances that are not synchronized with rotation, and it is not possible to suppress rotational irregularities with a period of one rotation.

The object of the present invention is to improve the above-mentioned drawbacks, use a rotary encoder with a single sensor, eliminate detection errors due to eccentricity, etc., and accurately detect fluctuations in instantaneous rotational speed. An object of the present invention is to provide a rotational speed detection device for a rotating body.

[Failure to solve the problem]

FIG. 1 is a diagram showing the basic configuration of the present invention. In Fig. 1, 1 is a rotating body to be detected, 2 is a slit plate, 3 is a rotary encoder, 4 is an output pulse of the rotary encoder, 5 is a time counter, 6 is a memory, 7 is an arithmetic circuit, 8 Reference numeral 9 indicates a correction circuit, and 9 indicates an output signal for maintaining a constant rotational speed.

The present invention has the following configuration in an apparatus for detecting the rotational speed of a rotating body 1 to be detected using output pulses 4 of a rotary encoder 3 that uses a slit plate 2 coaxially connected to the rotating body 1 to be detected. That is, a counter 5 that measures the time between output pulses 4 based on each slit of the slit plate 2 in the rotary encoder 3, a memory 6 that stores the counted value of the counter 5, and a read value from the memory 6. a correction value calculation circuit 7 that performs calculations to make the time between the output pulses 4 constant, and a correction value calculation circuit 7 that calculates the output correction value of the calculation circuit 7 and
A correction circuit 8 for correcting the output of the detection target rotating body 1 is provided, and the correction circuit 8 obtains a signal 9 for making the rotational speed of the detection target rotating body 1 constant.

[Effect]

As a result of recognizing that the rotation speed detection error of the rotary encoder itself is a periodic function of the rotation angle with one rotation as a period, and that the error occurs as a ratio to the pulse period,
The present invention has been devised. Therefore, in a rotary encoder 3 that uses a slit plate 2 having a plurality of slits coaxially connected to a rotating body 1 to be pressure tested such as a motor, when the pulse 4 based on each slit is repeatedly output, the output The time between pulses is measured by the counter 5 (for example, by counting the number of high-speed pulses generated).Then, the measured value is stored in the memory 6 in correspondence with the slit number. The data stored in the memory 6 is read out, and the arithmetic circuit 7 performs an arithmetic operation to make the time between the output pulses 4 constant. To calculate the average time, divide the total time between all output pulses for one rotation of the slit plate 2 by the number of slits.
Next, if the value obtained by dividing the time between each output pulse by this average time is the correction ratio, then the switch is changed at the next rotation of the slit plate, and at the time corresponding to each slit at that time, the above-mentioned "correction ratio '', it is possible to obtain a signal 9 for making the rotational speed of the rotating body 1 constant.

〔Example〕

FIG. 2 is a block diagram showing in detail the processing of the output pulse 4 from the rotary encoder 3 in FIG. 1 up to the correction circuit 8 as an embodiment of the present invention. 3 is an operational waveform diagram of FIG. 2, FIG. 4 is a diagram showing an example of data stored in the time measurement memory, and FIG. 5 is a diagram showing an example of storage of correction data in the memory.

It is assumed that the rotary encoder that obtains the input pulses in FIG. 2 has n slits.

In Fig. 2, 9 is a corrected signal, IO is an oscillator that generates high-speed pulses for time measurement, 11 is an operation sequencer that controls the processing order of each part, and 12 is a waveform shaping for the output pulse from the rotary encoder. 13 is a timing generation circuit that generates a clear signal and a latch signal from the signal waveform shaped by the waveform shaping circuit 12; 14 is an n-ary counter that counts slits one by one;
15 is an address generation circuit for addressing the memory 6; 5 is a counter; 5a is a latch that holds the count value of the counter 5; 6 is a memory; 6a is a multiplexer that switches data to be written to the memory 6; 6b is a memory 6 shows a multiplexer that switches the address input to 6. 7 shows the entire correction value calculation circuit, 7a is an adder, 7b is a latch that holds the result of adder 7a, 7c is a multiplier that multiplies 1/n, and 7d is used to divide input A by input B. Divider 8 indicates a multiplier as a correction circuit that multiplies the counter output and the memory output to obtain a correction signal.

The operation in Fig. 2 is based on the rotating body to be detected (not shown) and the rotary
Since the encoder has undergone predetermined adjustments at the time of manufacture, the initial writing operation to the memory 6, so-called 1-learning, is performed when it can be considered that it is initially rotating at a constant rotational speed. Therefore, when the sequencer 11 is instructed to start learning, the multiplexer 6a is switched to the latch 5a side and the multiplexer 6b is switched to the slit number counter 14 side. Every time a count value is obtained in the latch 5a, the count value is stored with the value indicated by the slit number counter 14 as an address in the memory 6. The count value of the latch 5a is obtained by counting the high-speed pulses oscillated by the oscillator 10 between the pulses obtained by waveform shaping the optical signal passing through the slit.

FIG. 4 shows an example of data stored in the memory 6 for rotation of the slit plate when there are ten slits in the slit plate. High speed pulse 800-1 between each slit
It shows that 100 pieces have been counted. At this time, the count value of the latch 5a is simultaneously supplied to the adder 7a, and the count value is integrated by the latch 7b. When the slit plate rotates once, the total number of pulses (10.000 in this case) is held in the latch 7b. Next, the sequencer 11 uses the multiplier 7C to calculate the total number of pulses as 1/n,
Here, 1/IO is used to obtain an average value of 1000. The sequencer 11 also connects the multiplexer 6b to the address generation circuit 1.
5 side, reads out the data in the memory 6, and divides the divider 7.
d to the terminal A side. Terminal B (II
The average value +000 is applied to J and divided by the data corresponding to the terminal. Since the result is a value for obtaining a correction value, the multiplexer 6a is switched to the divider 7d side and stored in the memory 6 at the same address as the read data. Next, the address of the address generation circuit 15 is set to ±1 and read operation and storage are performed in the same manner. When all the stored data in FIG. 4 are calculated, the data example shown in FIG. 5 is obtained. Here, the data shown in FIG. 5 may be stored in the memory 6, or may be stored in an independent correction ratio memory.

[Learning J] has now been completed, so the multiplexer 6b is switched to the slit number counter 14 side, and the correction value corresponding to each slit number is supplied from the memory 6 to the multiplier 8. A multiplier 8 multiplies the count value from the latch 5a by the correction signal from the memory to obtain a correction signal 9 for making the rotational speed of the rotating body to be detected constant.

Note that waveform A shown in FIG. 3 represents an input signal to the timing generation circuit 13, and waveform B represents a clear signal output from the same circuit 13, which is used to clear the counter 5. Waveform C
indicates the latch signal which is the output of the same circuit 13, and the latch 5
It is used to hold the count value of counter 5 in a. The waveform indicates the count value of the counter 5. In order to cause the latch 5a to hold the count value of the counter 5 at the rising edge of the input signal shown in waveform A, the latch signal of waveform B is used. Immediately thereafter, a clear signal of waveform C is used to clear counter 5 for the next count.

The above is an explanation of the operation of the device that detects the rotational speed of the rotating body to be detected, and FIG. 6 is a block diagram for explaining how to specifically stabilize the rotational speed of the rotating body using the resulting signal. be.

In FIG. 6, 21 is an instruction rotation speed signal, 22 is a periodic speed conversion circuit, 23 is a comparison circuit, 24 is a control calculation circuit,
25 is a D/A conversion circuit, 26 is a motor drive circuit, and 27 is a motor.

First, the motor 27 rotates the rotating body 1 to be detected with a constant driving force, and then the motor 27 stops driving and "learning" is performed while the rotating body 1 is rotating due to inertia. At that time, the torque ripple of the motor can also be removed. Next, from the correction circuit 8, a correction value Δ of the time required to rotate by an angle Δθ corresponding to one slit interval
Since t is obtained, this is converted into ω by the periodic speed conversion circuit 22.
=(Δθ)/(Δt) is performed to obtain the rotational speed ω, which is supplied to the comparator circuit 23.

The comparison circuit 23 compares ω with the commanded rotational speed and provides the difference e to the control calculation circuit 24. The control arithmetic circuit 24 executes a suitable algorithm such as a repeat control algorithm, creates a manipulated variable, and supplies it to the D/A conversion circuit 25. The D/A conversion circuit 25 converts U into an analog quantity, obtains a U that reflects the next ω, holds the current U, and supplies it to the motor drive circuit 26. The motor drive circuit 26 supplies a drive power proportional to the input magnitude of U to the motor 27.
give to In the feedback control loop configured in this way, the detection error of the rotary encoder is eliminated by the correction circuit 8, so the gain of the feedback control loop can be increased to widen the control band, or the arsenal control circuit 24 can be By implementing the algorithm, even fluctuations in the instantaneous rotational speed can be subject to feedback control and can be suppressed.

It goes without saying that the rotary encoder in the above description may be of an optical type, or may be of a mechanical type or a magnetic type.

Moreover, although the case has been described in which the rotational speed of the detection target rotating body during learning is constant, the predetermined effect can be obtained even when the rotational speed fluctuates by changing the correction value calculation method.

〔Effect of the invention〕

In this way, according to the present invention, since the installation of a rotary encoder with one sensor eliminates detection errors in the rotational speed of the rotating body to be detected due to eccentricity or processing distortion of the slit plate, fluctuations in the instantaneous rotational speed can be accurately detected. This greatly contributes to suppressing uneven rotation.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the principle configuration of the present invention, Fig. 2 is a diagram showing the configuration of an embodiment of the invention, and Fig. 3 is a diagram showing the configuration of the embodiment of the present invention.
4 is an example of data stored in the time measurement memory, FIG. 5 is an example of storage of correction data, and FIG. 6 is a block diagram showing a configuration for constantizing the rotational speed of the rotating body. 1 - Rotating body to be detected 2 - Slit plate 3 - Rotary encoder 4 - Output pulse 5 / Counter 6 - Memory 7 Correction value calculation circuit 8 Correction circuit 9 - Signal to keep the rotational speed constant Patent applicant: Fujitsu Limited t'l? Device b2 representative Patent attorney Eisuke Suzuki A Input B Latch operation waveform diagram 3rd! ! 1 Figure 1 Example of measurement data Figure 4 Example of correction data Figure 5

Claims (1)

[Claims] 1. Rotation of the rotating body (1) to be detected by the output pulse (4) of a rotary encoder (3) using a slit plate (2) coaxially connected to the rotating body (1) to be detected. In a device that detects speed, a slit plate (2) in a rotary encoder (3)
A counter (5) that measures the time between output pulses (4) based on each slit, a memory (6) that stores the value counted by the counter, and a counter that calculates the read value from the memory (6). a correction value calculation circuit (7) that performs calculations to make the time between the output pulses (4) constant; and a correction value that corrects the output correction value of the calculation circuit (7) with respect to the output of the counter (5). A rotation of a rotating body to be detected, characterized in that the correction circuit (8) obtains a signal (9) for constantizing the rotational speed of the rotating body to be detected (1). Speed detection device. 2. In the rotational speed detection device according to claim 1, each slit of the slit plate is assigned a slit number, and the time data between pulses is stored using the slit number as an address in the memory (6). A rotation speed detection device featuring: 3. The "correction ratio" value calculated by reading out the memory storage contents according to claim 2 is temporarily stored in the second memory before being corrected in the correction circuit (8). Rotation speed detection device.