JPS6349807A - Servo device - Google Patents

Abstract

PURPOSE:To ensure the highly accurate control with a servo device by using a computing element to correct the deviation to a duty ratio that is caused when the output signal of a speed generator is multiplied by 2. CONSTITUTION:The deviation of a duty ratio caused by the offset of an ampli fier when the output signal of a speed generator 2 is multiplied by 2 is detected while said deviation is controlled based on the value of a single cycle of the output signal of the generator 2 and then stored in a memory 5b of a processor 5 as the output correction data. The same correction data is also stored in the memory 5b against each signal waveform of the AC signal of a rotor. Then a speed error output is calculated based on the output correction data when the control is shifted to that applying the 2-multiplication. Thus it is possible to have an output of an error that receives no influence of said deviation to the duty ratio to ensure the highly accurate control.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a servo device that controls the rotational speed of a rotating body to a desired value.

BACKGROUND OF THE INVENTION Conventionally, as a method of controlling the rotational speed of a rotating body to a desired value, there has been a method that utilizes a speed generator that is connected to the rotating body and generates an output signal having a frequency and voltage corresponding to the rotational speed. It occupies the mainstream, and the output signal of the speed generator (F
Since only the frequency or repetition period of the G-times signal is used as speed information, a servo device in which a series of processes is digitized (for example, as shown in Japanese Patent Publication No. 53-19745 or U.S. Pat. No. 3,836,756). ) had the advantage of being able to obtain extremely high stable pressure.

By the way, this frequency or period detection method generates an error output signal by assuming that a predetermined edge of the output signal of the speed generator, which has been sufficiently amplified to become a rectangular wave signal, has speed information.

For example, in a typical period detection method, by counting clock pulses in the period from the leading edge of the output signal of the speed generator to the next leading edge of the output signal of the speed generator after amplification, the Then, based on this count value, a pulse width modulation signal (used when using a chopper type drive method) is generated, or the count value is converted into an analog voltage. I am getting the error output.

Therefore, in order to achieve control with higher resolution, it is necessary to increase the number of edges.

An easy way to increase the number of edges of the speed generator is to utilize both the leading and trailing edges of the square wave signal obtained by amplifying the speed generator's output signal. There is a method of measuring the period twice for each half period during one signal period, that is, doubling the output signal of the speed generator to obtain speed information at twice the frequency of the original output signal.

Problems to be Solved by the Invention However, in the above configuration, the output signal of the speed generator is amplified by using both the leading edge and the trailing edge of the rectangular wave obtained by amplifying the output signal of the speed generator. When multiplying, the duty ratio of the amplified speed generator output signal is not 50:50 due to amplifier offset and waveform distortion of the speed generator output signal, so the frequency of the speed generator output signal must be adjusted in the control system. There was a problem in that controllability deteriorated due to the disturbance. In particular, when an amplifier is constructed using a CMOS (complementary metal oxide semiconductor) process to save power, the offset is large, making it difficult to double the output signal of the speed generator.

In view of the above-mentioned problems, the present invention makes it possible to check whether the duty ratio is 50:50 even if the duty ratio after doubling the output signal of the speed generator is not exactly 50:50 due to the offset of the amplifier or the like. The present invention aims to realize a servo device that corrects the duty shift and performs accurate control during doubling.

Means for Solving the Problems In order to solve the above-mentioned problems, the servo device of the present invention doubles an AC signal having speed information of a rotating body and doubles the first and second signals during one period of the AC signal. doubling means for generating an output signal; period detection means for detecting the period of the output signal of the doubling means; memory means for storing the detected value of the period detecting means; an arithmetic unit for calculating an output; a disturbance means for supplying driving power to the rotating body based on the error output; and a period from the first output signal to the second output signal of the doubling means and a second output signal. A first method that calculates a deviation from a normal value from the period from the output signal to the first output signal, and causes the arithmetic unit to correct the error output by doubling at each period detection point based on the calculation result.
and a second error that causes the arithmetic unit to correct the error output by doubling when detecting a period at the same rotational position of the rotary body from the calculation result corresponding to the rotational position of the rotary body. This device is characterized by being equipped with an output correction means.

Function The present invention uses the above-described configuration to correct the shift in duty ratio that occurs when doubling the output signal of the speed generator, so that the duty ratio of the output signal of the speed generator after doubling is corrected by the arithmetic unit. Even if the speed generator is out of alignment, there is almost no disturbance in the frequency of the output signal of the speed generator in the control system, and highly accurate control can be performed.

Embodiment Hereinafter, a servo device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, in which the output of a speed generator (generally called a frequency generator or simply FG) 2 connected to a motor 1 is doubled by a doubling circuit 3. be done. The output of the doubler circuit 3 is supplied to a channel selector 4, which generates an address update signal for the memory 5b of the processor 5, and the address update signal is sent to the control bus 6.
is supplied to the processor 5 via.

Further, when the doubler circuit 3 outputs an output signal, a timing signal is outputted from the timing signal output terminal 4a of the channel selector 4 and supplied to the period detector 7. The period detector 7 is connected to the timing signal output terminal 4a.
The period of the timing signal outputted from the processor, that is, the period of the output signal of the doubler circuit 3 is measured and supplied to the processor sensor 50 memory 5b via the data bus 8. The memory 5b stores periodic data at an address based on the address update signal of the channel selector 4.

Next, in the processor 5, the speed of the motor 1 is determined by the calculator 5a from the period detector 7 via the data bus 8 based on the period data stored in the memory 5b of the processor 5 and the reference speed data set in advance. An error output is calculated and the calculated result is supplied to a digital-to-analog converter 10 via a data bus 9. The output of the digital-to-analog converter 10 is amplified by a power amplifier (indicated as a power amplifier in the figure) 11 and supplied to the motor 1 as driving power.

FIG. 2 is a circuit connection diagram showing a specific configuration of the 27x circuit 3, and 2a and 2b are input terminals to which the output signal of the speed generator 2 and the reference clock signal are input, respectively.

The output signal of the speed generator 2 is amplified to a certain voltage level by the amplifier 21 and input to the D input terminal of the D flip-flop 23. The Q output terminal of the D flip-flop 23 is connected to the D input terminal of the D flip-flop 24 and one input terminal of an EX-OR (exclusive OR) gate 25.
The Q output terminal of the D flip-flop 24 is connected to the other input terminal of the EX-OR gate 25. Clock terminals 23a, 24a of D flip-flops 23, 24 are connected to clock terminal 2b. The output terminal of the EX-OR gate 25 is connected to the output terminal 2C of the doubler circuit.

FIG. 3 is a signal waveform diagram for explaining the operation of the doubler circuit 3, and FIG. 3(a) shows the output signal waveform of the speed generator 2. 21, FIG. 3(C) is the output signal waveform of the waveform shaper 22, and is the signal waveform input to the D flip-flop 23, and FIG. It is a signal waveform, and is a signal with a pulse width of one clock of the reference clock signal manually inputted to the clock 2b at both edges of the signal of C1, and is a signal obtained by doubling the output signal of the speed generator 2. In other words, as shown in Figure 3 (dl
is the output signal of the doubler circuit 3.

Here, since there is an offset in the amplifier 21, the signal waveform after amplification of the output signal of the speed generator 2 is as shown in FIG.
), the waveform is offset from the center. Therefore,
The duty ratio of the output signal of the waveform shaper 22 is shown in FIG.
), the waveform does not have a duty ratio of 50:50 but deviates from the duty ratio of 50:50. Therefore, the period of the output of the EX-OR gate 25 shown in FIG. If it is rotating and the duty ratio after doubling is 48:52, the detected value of the period detector 7 will be the time interval from time t1 to time t2 in Fig. 3, which is 4% lower than the normal value. It will be a short value. Also, the time t
When the period detector 7 detects the time interval from time t2 to time t3, the period value is 4% longer than the normal value.

Furthermore, the same holds true for the next cycle from time L3 to time t5, and the time interval from time t3 to time L4 is 4% shorter than the normal value, and from time L4 to time t5.
The time interval will be 4% longer than the normal value. Therefore, by doubling the output signal of the speed generator 2, sections shorter and longer than the normal period value appear during one cycle of the output signal of the speed generator 2.

The processor 5 uses a signal obtained by doubling the output signal of the speed generator 2, that is, by doubling the signal, a period value that is shorter than the normal value and a period that is longer than the normal value appears.
When the computing unit 5a calculates the speed error output, the period is 4 in the section where the time interval from time t1 to time t2 is measured.
% shorter, this is the speed error output when the speed becomes 4% faster.In the section from time t2 to time t3, the period is 4% longer, so the speed is the speed when the speed becomes 4% slower. This is the error output. Therefore, motor 1
Even though the motor is rotating at the set speed, the error output increases or decreases, which is not desirable as a control system. In particular, at the time of startup, the speed error output does not take a normal value due to a shift in the duty ratio, so the motor 1 may hunt and not start properly.

However, in the embodiment of the present invention shown in FIG. 1, the duty ratio after doubling by the doubling circuit 3 is approximately 5.0.
It is configured so that a sufficient duty ratio can be secured even if it is not 750, and high-precision control can be achieved.
The process will be explained below.

The first period (third period) after doubling the output signal of the speed generator 2
High level section of the output signal of the waveform shaper 22 in Figure C)
Assuming that the second cycle #JJ (low level section of the waveform shaper 22 in Figure 3 C) is the section B, the motor 1 is controlled by one period of the output signal of the speed generator 2, Assume that the motor rotates at the set speed without being affected by the duty shift of the multiplier circuit.

Therefore, the value of one period of the output signal of the speed generator 2 becomes a constant value. That is, the periodic sum of the A section and the B section is also a constant value.

Here, if there is no deviation in the duty ratio due to the doubler circuit 3, the period values of the A section and the B section will be the same. However, due to the offset of the amplifier 21, the duty ratio is 50.
: Since it deviates from 50, the period values of section A and section B will not be the same, but will differ by a value corresponding to the offset. If the period deviation value of the A section is ΔA, the period deviation value of the B period is −ΔA. That is, amplifier 2
The shift in the period when the output signal of the speed generator is doubled due to an offset of 1 can be obtained from the difference between the A section and the B section, and is expressed as (1) 2.

Here, A and B indicate the period values of the interval and B interval, respectively. Further, selection of the address of the memory 5b according to the A section and the B section is performed based on the address update signal of the channel selector 4.

However, by finding the shift ΔA in the duty ratio due to the offset of the amplifier 21, calculating +ΔA on the measured period value in section B, and calculating -ΔA on the measured period value in section B, the amplifier 21 can be adjusted. It is possible to correct the period deviation due to the offset of 21. At the time of doubling, the arithmetic unit 5a calculates the speed error output based on the corrected period data, and the amplifier 21 is used for the speed error output.
The offset shadow does not appear.

A flowchart of duty ratio correction by the processor 5 based on the above calculation formula is shown in FIG.

Here, in order to increase the detection accuracy of period detection in the section B and section B (because one measurement is vulnerable to noise, etc.), we will average the measurements taken several times, and if there are large differences in period, we will Exclude from average data. If the number of times of averaging is n, then it is expressed as A-ward B i /n. Therefore, equation (1) becomes equation (2).

First, in block 401, the duty ratio after doubling the output signal of the speed generator 2 is not 50:50 due to the offset of the amplifier 21, so the motor 1 is started by one cycle of the output signal of the speed generator 2. and block 40
2, it is determined whether the motor 1 has reached a constant speed. If the speed is not constant, control is performed based on the value of one cycle of the output signal of the speed generator 2 until the speed becomes constant. When the motor 1 starts rotating at a constant speed, block 403 indicates that the motor 1 is rotating at a constant speed.
The period of each section is measured, and it is determined in block 404 whether or not it has been completed 0 times. If it has not been completed 0 times, the process returns to block 403. If it is completed 0 times, in block 405, after calculating the average of each of the sections H and B, the average value of the A section is subtracted from the average value of the B section, and the subtraction result is divided by 1/
2 to obtain the correction value ΔA.

After the correction value ΔA is determined, the process moves to block 406, which is doubling control.

The calculation formulas for the speed error output of the calculation unit 5a after shifting to the double multiplication control are as shown in formulas (3) and (4).

○ = A - D + ΔA (3) OR = B - D - ΔA (4) Here, D is predetermined reference speed data, OA is the speed error output of section A, 0. l is the speed error output in section B.

In this way, since the error output is corrected for the shift in duty ratio using the correction value ΔA, highly accurate control is possible.

However, the amplitude of the output signal of the speed generator 2 is not constant and A
When receiving M modulation, the shift in duty ratio is also A.
Due to the influence of M modulation, the only correction value for duty ratio correction is no longer sufficient, and a correction error remains, so highly accurate control cannot be expected. Therefore, when the output signal of the speed generator 2 is subjected to AM modulation, the duty ratio must be corrected according to each output signal of the speed generator 2.

First, FIG. 5 shows changes in the duty ratio when the output signal of the speed generator 2 is subjected to AM modulation. Figure 5 (a
) is the output signal waveform of the speed generator 2 when the motor 1 is rotating at a constant speed, and the first correction is performed based on this signal waveform. The waveform marked ■ in FIG. 5(a) is a signal waveform when the output signal of the speed generator 2 is subjected to AM modulation, and in this case, the amplitude is larger than the signal waveform at the time of the first correction. FIG. 5(bl) is the output signal waveform of the waveform shaper 22 for the signal waveform of ■ in FIG. 5(a), and FIG. 5(C) is the waveform shaping for the signal waveform of ■ in FIG. 5(a). This is the output signal waveform of the device 22.

Although the duty ratio is shifted in the signal waveform of FIG. 5 (bl), it is corrected by the correction value ΔA, so that an accurate duty ratio can be ensured.

However, in the signal waveform of Fig. 5(C), even if the correction value ΔA is used, a deviation of only 8E remains due to AM modulation, making it impossible to accurately correct the duty ratio, and further correcting the duty ratio. must be carried out.

In the following, the correction value ΔA obtained by the flowchart of FIG. 4 will be referred to as a first correction value, and the correction value ΔE of the duty ratio for AM modulation will be referred to as a second correction value.

Since the amplitude of the output signal of the speed generator 2 due to AM modulation is normally constant with respect to the rotational position of the motor 1, correction of the shift in duty ratio due to AM modulation can be performed for each output signal of the speed generator 2. The number of correction values ΔE of 2 is the same as the number of pulses of the output signal output by the waveform shaper 22 during one rotation of the motor 1. For example, motor 1
If the waveform shaper 22 outputs 360 pulses during one rotation, the second correction value ΔE will be 360.

The second correction value is determined using the same method as the first correction value. In the first correction, the period after doubling of the speed generator 2 was measured once and the difference between the average values was taken as the first correction value ΔA, but in the second correction The period corresponding to the rotational position of the motor 1 of the machine 2 is measured m times, and the value obtained by subtracting the first correction value ΔA from the value obtained by halving the difference between the average values is set as the second correction value ΔE.

The period after doubling the j-th output signal of speed generator 2 is A
If j and Bj, there will be an Aj interval and a Bj interval. Therefore, the j-th second correction value ΔEj is expressed by equation (5).

Z Therefore, the speed error output AOj of Aj section and Bj section
, BOj are expressed by the formulas (61 and (71), respectively.

AOj=Aj-D+ΔA+ΔE j (5)B
Oj=Bj-D-ΔA-ΔE j (71th 6th
The figure is a flowchart for calculating the second correction value of the duty ratio during AM modulation. Here, it is assumed that the first correction for the shift in duty ratio has been completed and the first correction value ΔA has been calculated according to the flowchart of FIG.

Accordingly, the flowchart of FIG. 6 continues with block 405 of FIG. It is also assumed that the waveform shaper 22 outputs P pulses during one rotation of the motor.

First, in block 601, the arithmetic unit 5a reads the period data whose period has been detected from the period detector 7, and determines which period data of the output signal of the speed generator 2 and the section where the period has been detected is section A. Whether it is in section B or not is read from the channel selector 4. And block 60
2, and according to the read data, it is determined whether the motor l has rotated once in each j-th rotation, that is, it is determined whether j=p, and if j=P, the process proceeds to block 601. return. If j=P, it means that one measurement of the period corresponding to each output signal of the speed generator 2 has been completed, and the process moves to block 604.

In block 604, it is determined whether or not the measurement of the cycle corresponding to each output signal of the speed generator 2 has been completed m times, and if it has not been completed m times, the process returns to block 601.

If m times are completed, block 605 indicates Aj section.

After calculating the average value of each of the Bj sections, subtract the average value of the Aj section from the average value of the Bj section, and subtract the first correction value ΔA from the value obtained by halving the subtraction result to obtain the second correction value. ΔE
We are looking for the value of j. After finding the correction value ΔEj,
The process moves to block 606, which is control for doubling.

After shifting to double multiplication control, the speed error output is output from the calculator 5a.
It is calculated using equations (6) and (7).

In this way, the shift in the duty ratio that occurs when doubling the output signal of the speed generator 2 can be calculated using the first correction value ΔA obtained from equation (2) and the second correction value ΔE obtained from equation (5). Since the speed error output is corrected using the equations (6) and (7), highly accurate control is possible.

Note that the first and second corrections are performed at the same time, and the first and second corrections are performed simultaneously.
It is also possible to store the correction value in the memory according to the output signal of the speed generator, but since the first correction value is larger than the second correction value and only one first correction value is required. , 1st
By storing the correction value and the second correction value in the memory according to each output signal of the speed generator, it is possible to store one first correction value and the second correction value according to each output signal of the speed generator. This is not preferable because it requires a larger memory size than storing the correction values in memory.

In addition, the second correction value is a correction value for a shift in the duty ratio at the time of doubling due to the offset of the amplifier and the AM modulation of the output signal of the speed generator, so for example, even if the AM modulation of the output signal of the speed generator is sinusoidal, For example, it is not necessary to store all the second correction values in memory, but by storing some second correction values in memory and making a table of sine wave functions, all outputs of the speed generator can be calculated. A second correction position for the signal can be calculated, and the memory capacity can be reduced.

As described above, according to this embodiment, when the output signal of the speed generator is doubled and used, the shift in duty ratio caused by the offset of the amplifier can be corrected based on the value of one cycle of the output signal of the speed generator. It is detected during control and stored in the processor memory as output correction data.
When shifting to control by doubling, the speed error is calculated using the output correction data, so it is possible to output an error output that is not affected by the shift in duty ratio.

Highly accurate control can be achieved.

Effects of the Invention As described above, the present invention doubles an AC signal having speed information of a rotating body, and calculates the first and second signals during one period of the AC signal.
doubling means for generating an output signal; period detection means for detecting the period of the output signal of the doubling means; memory means for storing the detected value of the period detecting means; an arithmetic unit for calculating an output; a disturbance means for supplying driving power to the rotating body based on the error output; a cycle from a first output signal to a second output signal of the doubling means; and a second output signal. A first method that calculates a deviation from a normal value from the period from the output signal of an error output correction means, and a calculation unit for each signal waveform of the alternating current signal of the rotary body at the time of period detection at the same rotational position of the rotary body based on the calculation result according to the rotational position of the rotary body; The device is characterized in that it is equipped with a second error output correction means for correcting the error output by doubling, and the duty ratio caused by the offset of the amplifier when the output signal of the speed generator is doubled and used. The deviation is detected during control based on the value of one cycle of the output signal of the speed generator and stored in the processor's memory as output correction data, so when control is shifted to doubling, Since the speed error output is calculated using the output correction data, it is possible to output an error output that is not affected by the shift in the duty ratio.
This has an extremely large effect in that highly accurate control can be achieved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a servo device according to an embodiment of the present invention, FIG. 2 is a circuit connection diagram showing a specific example of a doubler circuit, and FIG. 3 is a signal diagram for explaining the circuit operation of FIG. 2. Waveform diagram, Figure 4 is a flowchart for explaining the error correction operation, Figure 5 is a signal waveform diagram for explaining the change in duty ratio due to AM modulation, and Figure 6 is for explaining the error correction operation due to AM modulation. This is a flowchart for 1...Motor, 2...Speed generator, 4
...Channel selector, 5...Processor, 7...Period detector, 10...
Digital-to-analog converter, 11...Power amplifier.

Claims (3)

[Claims] (1) A doubling means for doubling an alternating current signal having speed information of a rotating body and generating first and second output signals during one period of the alternating current signal, and a period of the output signal of the doubling means. a period detection means for detecting the period detection means, a memory means for storing the detection value of the period detection means, a calculation unit for calculating an error output from the previous detection value and a reference value, and a drive power for the rotating body based on the error output. and a drive means for supplying the same, and a deviation from the normal value is calculated from the period from the first output signal to the second output signal of the doubling means and the period from the second output signal to the first output signal. and a first error output correction means for causing the arithmetic unit to correct the error output by doubling at each period detection time based on the calculation result; A servo device comprising second error output correction means for causing the arithmetic unit to correct the error output by doubling at the time of period detection at the same rotational position. (2) an amplifier that amplifies an AC signal having speed information of a rotating body; a waveform shaper that shapes the output signal of the amplifier; and a waveform shaper that converts both edges of the output signal of the waveform shaper into A servo device according to claim (1), comprising a doubling means for producing a multiplied output. (3) Every time the doubling means generates an output signal of an AC signal having speed information of the rotating body over at least one revolution of the rotating body, the address of the memory means storing the detected value of the period detecting means is updated and calculated. Claim (1): wherein the device is equipped with a channel selector that compares the periodic data stored at the corresponding address of the memory means with a reference value and sends an error output to the disturbance means according to the magnitude thereof. The servo device described.