JPH04264212A - Automatic offset/amplitude correction system for sensor signal - Google Patents

Abstract

PURPOSE:To automatically execute an offset correction and an amplitude correction for a signal from a sensor of a detector which detects a speed and position. CONSTITUTION:Signals from sensors in detectors which are mounted on a spindle of a machine tools and a rotating shaft of a motor to detect rotational speeds and positions are converted into digital values to obtain (S3) averages (S1 and S2). As the averages are values of amplitude centers, offset correction values HA and HB are determined (S4) in difference between the values and values of set amplitude centers. An offset correction value is added to values of signals from the sensors to determine signals PCDa and PCDb without offset (S7) and a signal of the position interpolated in a sine wave of the sensor signal is determined from the signals. Moreover. analog values of the offset correction values HA and HB are added to the sensor signal to determine an analog signal offset corrected while an amplitude correction is performed to obtain feedback signals of the position and speed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offset and amplitude correction method for a sensor that detects the speed and position of a main shaft of a machine tool or a rotating shaft of a motor.

0002

[Prior Art] A detector for detecting the speed and position of the main shaft of a machine tool or the rotating shaft of a motor has a code plate attached to the rotating shaft, and a sensor arranged with respect to the code plate has a 90 degree phase difference. Output a certain A-phase and B-phase sine wave, and
The speed and position of the rotating shaft are detected from the phase and B phase sine waves. In this case, if there is an offset in the A-phase and B-phase sine waves (if the center of amplitude deviates from the set value), accurate speed and position cannot be detected. Therefore, a sensor signal offset correction circuit is provided.

FIG. 7 is a circuit diagram of this conventional sensor signal offset correction. In Figure 7, MA,
RMA is a sine wave of an A-phase signal and an A-phase inverted signal obtained by inverting that signal. Further, MB is a B-phase sine wave signal having a phase difference of 90 degrees from the A-phase signal, and RMB is an inverted signal of this B-phase signal MB. A differential amplifier 100a amplifies the difference between the A-phase sine wave signal MA and its inverted signal RMA. Also, 1
00b is also a differential amplifier, which amplifies the difference between the B-phase sine wave signal MB and its inverted signal RMB. 101a and 101b are variable resistors for offset adjustment, VM is a set neutral point voltage, and the output voltages of the differential amplifiers 100a and 100b are observed, and the amplitude center of the sine wave of the output voltage is set to the above neutral point voltage. The variable resistors 101a and 101b are adjusted so that VM is reached and the offset is 0V. Also, 102a,
Reference numeral 102b is an analog/digital converter (hereinafter referred to as an A/D converter) which converts the offset-corrected outputs of the differential amplifiers 100a and 100b into digital values. Further, 103 is a ROM, which uses the outputs of the A/D converters 102a and 102b as address signals, and generates a rectangular wave signal Sg2 synchronized with the A-phase sine wave and this signal S.
Rectangular wave signal Sg3 with a 45 degree phase difference from g2, and B
Rectangular wave signal Sg4 synchronized with phase signal MB and this signal Sg
4, a rectangular wave signal Sg5 having a phase difference of 45 degrees is output.

That is, if the A-phase signal output from the A/D converter 102a is plotted on the horizontal axis, and the B-phase signal output from the A/D converter 102b is plotted on the vertical axis, each of the A-phase and B-phase The point indicated by the value becomes a circle in the Lissajous figure, and the rotation angle within one cycle of the sine wave can be determined. Therefore, A/D converter 1
The A-phase and B-phase signals output from 02a and 102b are RO
By inputting it as the address of M103 and storing the rotation angle information in that address, the above-mentioned output signal S
It is possible to output signals g2 to Sg5. Then, the speed and position are detected from these signals Sg2 to SG5. Note that Sg1 is an alarm signal when the input signal of the ROM 103 deviates from the standard value. Further, in FIG. 7, R is a resistance.

[0005]

[Problems to be Solved by the Invention] As described above, offset correction of the sensor signal is performed using the variable resistors 101a and 10.
This is done by adjusting 1b. Therefore,
The offset value is determined by the temperature at the time offset correction is performed, the speed of the rotating shaft, etc., and is fixed. If the offset value shifts due to temperature changes and is no longer 0V, the address in the ROM 103 will change, and the detected speed will change. , the position will also fluctuate, making stable detection impossible. Furthermore, if the amplitude of the sine wave fluctuates, the detection speed and position will also fluctuate, making it impossible to detect accurate values. In addition, in cases such as C-axis control of the spindle that determines the rotational position or synchronization of two spindles, the value at a certain angle of the above sine wave becomes a problem, so amplitude fluctuations are affected by these C-axis control, synchronous operation, etc. A phenomenon occurs in which accurate control cannot be achieved.

SUMMARY OF THE INVENTION An object of the present invention is to provide an offset/amplitude correction method that automatically corrects the offset of a sensor signal and also automatically corrects the amplitude.

[0007]

[Means for Solving the Problems] The present invention samples signals from a sensor that outputs signals with a 90 degree phase difference depending on the rotation of the main shaft of a machine tool or the rotating shaft of a motor at a predetermined period, converts them into digital values, and averages them. determine an offset correction amount from the average value and the neutral point voltage value, convert the offset correction amount into an analog amount, and perform offset correction on the sensor signal based on the analog quantified offset correction amount; The amplitude of the offset-corrected signal is normalized, the amplitude is corrected, and the signal is used as a feedback signal for velocity/position. At the same time, the digital value of the signal from the sensor detected at each sampling period is converted into a digital value. The above offset correction amount is added to obtain the offset-corrected signal values of the A-phase and B-phase, and the rotational position signal is obtained by interpolating the inside of the sine wave from the offset-corrected A-phase and B-phase signal values. I also asked for it.

[0008]

[Operation] When the rotating shaft rotates at a speed sufficiently faster than the sampling period, the average value becomes the value at the center of the amplitude of the A phase and B phase. Therefore, when the difference between the amplitude center determined from this average value and the set neutral point voltage values (amplitude center voltage values) of the A phase and B phase is determined, this becomes the offset correction amount. If this offset correction amount is converted into an analog value and the converted offset correction amount is corrected for the signal from the sensor, a signal without offset (the neutral point voltage of the sine wave is equal to the set voltage) will be obtained. The amplitude of the offset-corrected signal is normalized and the amplitude is corrected to obtain a velocity/position feedback signal. Furthermore, by adding the digital offset correction amount to the digital value of the signal from the sensor detected every sampling period, offset-corrected A-phase and B-phase signals are obtained, and this offset-corrected A-phase and B-phase signals are obtained. From the phase and B phase signals, a signal equivalent to a position coder indicating the position of the rotation angle for interpolating the sine wave is obtained using a method similar to the conventional method.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 and 2 are circuit diagrams for sensor signal offset/amplitude correction according to an embodiment of the present invention. In the figure, 1a,
1b is a differential amplifier that amplifies the difference between the A-phase sine wave signal MA and its inverted signal RMA, and the difference between the B-phase sine wave signal MB and its inverted signal RMB; 2a and 2b are A/D converters;
3a, 3b, 5a, 5b, 8a, 8b are latch circuits, 4
is a microcomputer with processor, ROM, and RAM
It has memory such as. 6a and 6b are digital/analog converters (hereinafter referred to as D/A converters), 7a and 7b are adders, 9 is a ROM, a circuit for creating a signal equivalent to a position coder, 11a and 11b are adders/subtractors, and 12a and 12b are A /
A D converter, 13 is a ROM, 14a and 14b are D/A converters, and 15a and 15b are subtracters.

A-phase signal MA and its inverted signal RMA, and B-phase signal MB and its inverted signal R output from the sensor.
The MBs are amplified by differential amplifiers 1a and 1b, respectively, and converted into digital signals by A/D converters 2a and 2b. Then, it is latched by the latch circuits 3a and 3b in response to a latch command LT1 from the microcomputer 4, and is then input to the microcomputer 4 via the data bus DB in response to a read command output from the microcomputer 4. . . Note that the A/D converters 2a, 2
b outputs an 8-bit output, and the A-phase and B-phase signals are each represented by 8-bit digital values.

On the other hand, the processor of the microcomputer 4 executes the process shown in FIG. 3 at predetermined intervals. In addition,
In this example, the number of sampled data is 25.
6 to find the offset correction value. Also,
As the number of sampling data increases, offset correction becomes possible up to a low speed range.

First, when the power is turned on to this device, the processor of the microcomputer 4 initializes and stores sampling data D(0) to D(255).
Each value of AM is converted to the value of neutral point voltage VM (128 in decimal notation)
) and set the index i to "0". The processor of the microcomputer 4 has latch circuits 3a and 3.
After outputting a latch command LT1 to b, outputting a read command to latch circuits 3a and 3b, and reading data D(i) stored in latch circuits 3a and 3b (step S1);
Next, the read data D(i) is stored in the RAM address corresponding to the index i (step S2). Note that the 0 to 7 bits of each address contain A phase data of 8 to 15 bits.
B-phase data is stored in the bit. And RAM
The average values Na and Nb of the A-phase and B-phase data stored in addresses 0 to 255 are obtained by calculating the following equations 1 and 2 (step S3), and the center point of the Lissajous figure of the circle is obtained. Note that Da(i) is the A-phase data of the data D(i), and Db(i) is the B-phase data of the data D(i).

[0013] Na=[Da(0)+Da(1)+Da(2)
+……+Da(255)]/256
...(1) Nb=[Db(0)+Db(1)
)+Db(2)+......+Db(255)
]/256...(2) And this average value Na
, "2's" complement of Nb NEG (Na), NEG (Nb)
are set as offset correction values HA, HB and output to the data bus DB (steps S4, S5), and the latch circuits 5a, 5b
This offset correction value H is output by outputting the latch command LT3 to
A and HB are latched by latch circuits 5a and 5b (step S6). Next, the A-phase and B-phase data Da detected in the corresponding period are added to the offset correction values HA and HB, respectively.
Add (i) and Db(i) as shown in equations 3 and 4,
Subtract the value "128" corresponding to the neutral point voltage VM to obtain the position coder equivalent signal PCD (PCDa, PCDb)
is determined and output to the data bus DB (steps S7, S8
), outputs the latch signal LT2 to the latch circuits 8a, 8b (step S9), and stores it in the latch circuits 8a, 8b. In this embodiment, since each address of the A phase and B phase of the ROM 9, which will be described later, is composed of 6 bits, the position coder equivalent signal PCD (PCDa,
PCDb), the lower 2 bits are discarded and only the upper 6 bits are output.

PCDa=Da(i)+HA-1
28...(3) P
CDb=Db(i)+HB-128...
(4) Then, the index i is incremented by "1" (step S10), and it is determined whether the index i is "256" (step S11), and if it is not "256", the processing for the corresponding cycle is terminated. , if the index i is "256", the index i is set to "0" (step S12) and the cycle ends. Thereafter, the processor repeats the above process every predetermined period.

Next, it will be explained with reference to FIG. 4 that the offset correction values HA and HB become offset correction values and correspond to the position coder equivalent signal PCD.

If a Lissajous figure is drawn with phase A on the horizontal axis and phase B on the vertical axis, a circle will be drawn since the phases A and B have a 90 degree phase difference. Therefore, phase A,
When a Lissajous figure is drawn using the B-phase data sine wave data Da and Db, for example, if it is a circle C1 in FIG.
By taking the average of these data Da and Db, the coordinate values (Na, Nb) of the center point Nm can be found. Then, “2” of the center point Nm
'' becomes the offset correction values HA and HB. If corrected using this correction value, the set neutral point VM
The offset is corrected to create a corrected circle C2 centered at . The rotation angle for interpolating within the sine wave can be determined from the corrected A-phase and B-phase values. For example, if the calculated A-phase value Na at the center point is "148",
By reversing the “1” and “0” of each bit in binary numbers, we get the binary number “1” and “0”.
If we take the complement by adding ``1'', we get ``108''. That is, the correction value HA = NEG (148) = 108, and the detected value of the A phase is, for example, "236", the above correction value "108" is added to this value, and the value corresponding to the neutral point voltage VM is "128" is subtracted, it becomes "216", which is A
This means that offset correction has been performed on the phase. Offset correction is also performed for the B phase by performing similar processing.

In step S5, offset correction values HA, H
When B is output from the microcomputer 4 and latched by the latch signal LT3 in the latch circuits 5a and 5b, the output of the latch circuits 5a and 5b is converted into an analog voltage by a D/A converter, and corrected to this voltage. Voltage normalized voltage VN
and the neutral point voltage VM are added, and adders 7a and 7b create offset correction voltages HA and HB by normalizing the offset correction value. For example, if the output of the D/A converter is 4 to 5V, it is converted to 2 to 3V.

Then, the adder/subtractors 11a and 11b apply the normalized offset voltages HA and HB to the differential amplifier 1a.
, 1b are added, and the neutral point voltage VM is subtracted to output speed feedback signals VA and VB. That is, the speed feedback signals VA and VB are the potential difference with the neutral point voltage VM, and vibrate up and down with 0V as the center.

Furthermore, these speed feedback signals VA and VB are A
The signal is input to the /D converters 12a and 12b and converted into a digital value, and this signal is input as an address to the ROM 13, and the ROM 13 stores amplitude correction data in accordance with the combination of the values of the velocity feedback signals VA and VB. This amplitude correction data is output, and is converted into analog voltages VAc and VBc by D/A converters 14a and 14b, and added by adders 15a and 15b.
Ac, VBc, speed feedback signals VA, VB output from adders/subtractors 11a, 11b, and neutral point voltages VM, VM
are added to output speed feedback signals VfA and VfB. That is, as shown in FIG. 5, sinusoidal A-phase and B-phase sine wave signals having the amplitude center at the neutral point voltage VM are output as speed feedback signals VfA and VfB.

On the other hand, the output in step S6 is
The latch circuit 8a is activated by the latch signal LT2 output at 7.
, 8b is input to the address of the ROM 9. As shown in FIG. 6, this ROM9 stores the rotation angle of 16 divided sine wave half cycles in 4 bits.The output of each bit is outputted from this ROM9, and from this output, the position coder As shown in FIG. 6, the equivalent signal generating circuit 10 outputs A-phase and B-phase position coder equivalent signals PA and PB, each of which has one period equal to 1/4 period of a sine wave. In addition,
This ROM9, position coder equivalent signal creation circuit 1
The details of 0 are the same as those described in Japanese Patent Application No. 2-330006.

[0021]

[Effects of the Invention] In the present invention, the amplitude center of the signal from the sensor is determined, and offset correction is always performed so that this center becomes the set amplitude center. Any offset deviations are automatically corrected, resulting in accurate velocity and position feedback signals. Furthermore, since the amplitude of the sensor signal is also corrected to a standardized value, the interpolated position within the sine wave cycle of the sensor signal is also accurate, and the C-axis control of the spindle, which determines the rotational position, and the synchronous control of the spindle. becomes accurate.

[Brief explanation of the drawing]

FIG. 1: Sensor signal offset and
This is part of the amplitude correction circuit diagram.

FIG. 2 is a continuation of the same circuit diagram.

FIG. 3 is a flowchart of processing executed by the processor of the microcomputer in the same embodiment.

FIG. 4 is an explanatory diagram of offset correction in the same embodiment.

FIG. 5 is an explanatory diagram of amplitude correction in the same embodiment.

FIG. 6 is an explanatory diagram of creating a position coder-equivalent signal in the same embodiment.

FIG. 7 is a diagram of a conventional offset correction circuit.

[Explanation of symbols]

1a, 1b Differential amplifier 2a, 2b, 12a, 12b A/D converter 3a, 3
b, 5a, 5b, 8a, 8b Latch circuit 4 Microcomputer 6a, 6b Digital/analog converter (hereinafter referred to as D/
A converter) 7a, 7b Adder 9, 13 ROM 10 Position coder equivalent signal creation circuit 11a,
11b Addition/subtraction device 14a, 14b D/A converter 15a, 15b Subtractor

Claims (3)

[Claims] 1. A speed/position detection method for detecting the speed and position of a rotating shaft of a machine tool or a rotating shaft of a motor based on a signal from a sensor that outputs a signal with a 90 degree phase difference according to the rotation of the rotating shaft, The signal from the above sensor is sampled at a predetermined period, converted into a digital value, and the average value is determined. The offset correction amount is determined from the average value and the neutral point voltage value. The offset correction amount is converted to an analog value. The sensor signal is offset-corrected based on the offset correction amount, and the amplitude of the signal is normalized for the offset-corrected signal, and the amplitude is corrected. Automatic offset/amplitude correction method. 2. A speed/position detection method that detects the speed and position of the rotating shaft from a sensor outputting a signal with a 90 degree phase difference depending on the rotation of the main shaft of a machine tool or the rotating shaft of a motor, The signal from the sensor is sampled at a predetermined period, converted into a digital value, and the average value is determined. The offset correction amount is determined from the average value and the neutral point voltage value, and the digital value of the signal from the sensor detected at each sampling period is calculated. The offset-corrected A-phase and B-phase signal values are obtained by adding the above offset correction amount to the offset-corrected A-phase and B-phase signal values. Automatic offset method for sensor signals as desired. 3. The average value obtained by sampling the signal from the sensor and converting it into a digital value and the offset correction amount obtained from the neutral point voltage value are calculated as the digital value of the signal from the sensor detected at each sampling period. The offset-corrected A-phase and B-phase signal values are obtained by adding the offset-corrected A-phase and B-phase signal values, and the rotational position signal is also obtained by interpolating the inside of the sine wave from the offset-corrected A-phase and B-phase signal values. The automatic offset/amplitude correction method for a sensor signal according to claim 1.