JP2005098735A - Position-detecting means and position control means using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems wherein resistor divided multiplying methods cannot adopt so many divisions, because increasing the number of divisions results in requiring more comparators which increase the cost and make the resistance to noise poor, and that in the case of A/D conversions, a position detection timing is delayed for a period required to carry out the A/D conversions and calculations, and in order to increase the number of divisions, the number of bits of the A/D conversion must be increased, and the calculations are complicated. <P>SOLUTION: A position-detecting means which outputs a plurality of positional waveform signals with positional phases differing from each other and corresponding to relative positions between itself and an object to be measured, is provided with: a signal generating means which generates a plurality of temporal waveform signals being in forms identical to the plurality of positional waveform signals and having phases differing from them; a plurality of comparing means which compare the plurality of positional waveform signals with the plurality of temporal waveform signals, respectively; and a phase detecting means which receives output signals of the comparing means and outputs phase information of the positional waveform signals. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to position detection means and position control means using the position detection means.

  As a conventional technique, there is a method of A / D converting a sine wave encoder signal and calculating its phase by calculation (see, for example, Patent Document 1).

Further, there is a method of performing pulse width modulation as compared with a high-frequency sine wave, calculating a signal amplitude from the pulse width, and interpolating (for example, refer to Patent Document 2).
Japanese Patent Laid-Open No. 54-019773 JP 63-263418 A

  In the multiplication method by resistance division, if the number of divisions increases, the number of divisions cannot be increased due to the cost increase due to the increase in the number of comparators and noise-sensitive problems. In the case of A / D conversion, the position detection is delayed by the time required for A / D conversion and calculation, the number of bits for A / D conversion must be increased to increase the number of divisions, and the calculation is complicated. There's a problem. There is also a method of knowing the signal level by the pulse width modulation method, but since the voltage level is only A / D converted by detecting the pulse width, there is a problem similar to the method by the A / D conversion.

  Therefore, an exemplary object of the present invention is to provide a position detecting means for solving the problem.

  To achieve the above object, according to a first aspect of the present invention, there is provided a position detecting means for outputting a plurality of positional waveform signals having different positional phases corresponding to a relative position with respect to an object to be measured. A signal generating means for generating a plurality of temporal waveform signals having the same shape and different phases as the plurality of positional waveform signals, and the plurality of positional waveform signals and the plurality of temporal waveform signals respectively. A plurality of comparison means for comparison, and a phase detection means for inputting the output of the comparison means and outputting phase information of the positional waveform signal are characterized.

  In the present invention, a positional waveform of a plurality of phases corresponding to a position is compared with a temporal waveform of the same shape having a predetermined frequency in which the position is replaced with time, whereby one period of the predetermined frequency is compared. The positional phase is detected by making use of the fact that all the waveforms match once in the period.

  According to a second aspect of the present invention, there is provided an oscillator in which the signal generating means for generating the temporal waveform signal generates a clock signal of a reference frequency, an integrating means for integrating a predetermined integrated value at the timing of the clock signal, Waveform generating means for generating an analog signal having a predetermined value in accordance with the integrated value.

  The present invention is to generate a temporal waveform signal based on a highly accurate oscillator.

  In a third aspect of the invention, the signal generating means for generating the temporal waveform signal is characterized in that a low pass filter is connected to the output of the waveform generating means.

  The present invention smoothes the stepped waveform output.

  According to a fourth aspect of the invention, the predetermined integrated value is switched according to the frequency of the positional waveform signal.

  In the present invention, the position detection resolution is switched in accordance with the frequency of the positional waveform signal.

  The fifth invention is characterized in that phase detection is performed by exclusive OR means for performing exclusive OR between output signals of the comparison means.

  In the present invention, the exclusive phase means performs multiplication of the sign level between the output signals when the output signal of the comparison means is represented by positive and negative signs, and detects the positional phase.

  According to a sixth aspect of the present invention, there is provided filter means for inputting the output signal of the phase detection means and for preventing the output from being changed when the pulse width of the output signal is narrower than a predetermined pulse width.

  In the present invention, noise included in the phase detection signal is removed.

  According to a seventh aspect of the invention, there is provided phase difference detection means for inputting an output signal of the phase detection means and outputting a phase difference signal indicating a phase difference with respect to a reference phase signal.

  In the present invention, the phase is obtained with respect to an arbitrary reference phase.

  According to an eighth aspect of the present invention, there is provided an amplitude comparing means for detecting a difference in amplitude between the positional waveform signal and the temporal waveform signal, and an amplitude for adjusting the amplitude so as to reduce the amplitude difference according to the output of the amplitude comparing means. An adjustment means is provided.

  According to the present invention, the difference in amplitude between the positional waveform signal and the temporal waveform signal is detected, and the amplitudes of both waveforms are made equal to improve the phase detection accuracy.

  According to a ninth aspect of the present invention, the positional waveform signal and the temporal waveform signal are input to exclusive OR means, and the maximum pulse width within a predetermined time of the pulse width of the output pulse signal of the exclusive OR means is detected. A maximum pulse width detecting means for adjusting the amplitude, and an amplitude adjusting means for adjusting the amplitude so as to reduce the amplitude difference in accordance with the output of the maximum pulse width detecting means.

  In the present invention, the difference in amplitude between the positional waveform signal and the temporal waveform signal is detected by the maximum value of the pulse width of the output signal of the exclusive OR means.

  The tenth invention is characterized in that the difference in amplitude between the positional waveform signal and the temporal waveform signal is corrected by adjusting the power of the light source of the position detecting means.

  The present invention adjusts the amplitude of the positional waveform signal by changing the power of the light source.

  An eleventh aspect of the invention relates to an offset comparison means for detecting a difference in offset level between the positional waveform signal and the temporal waveform signal, and an offset so as to reduce the difference in offset level in accordance with the output of the offset comparison means. An offset adjusting means for adjusting the level difference is provided.

  The present invention improves the phase detection accuracy by detecting the difference between the offset levels of the positional waveform signal and the temporal waveform signal and equalizing the offset levels of both waveforms.

  A twelfth aspect of the invention relates to a plurality of comparison means for comparing the positional waveform signal and the temporal waveform signal, respectively, and phase detection for inputting the output of the comparison means and outputting phase information of the positional waveform signal Means, a high / low ratio detection means for detecting a ratio of high and low times within a predetermined time of the output pulse signal of the comparison means, and the positional waveform signal and the temporal signal according to the output of the high / low ratio detection means An offset adjusting means for adjusting an offset level of at least one of the waveform signals is provided.

  The present invention detects the ratio of the high and low times within a predetermined time of the output pulse signal of the comparison means for the difference between the offset levels of the positional waveform signal and the temporal waveform signal, compares this with a predetermined value, By detecting the difference in the offset level based on the comparison result, the difference in the offset level is detected by a small-scale digital circuit.

  The thirteenth invention is characterized in that the difference in offset level between the positional waveform signal and the temporal waveform signal is corrected by adjusting the power of the light source of the position detecting means.

  The present invention adjusts the offset level of the positional waveform signal by changing the power of the light source.

  In a fourteenth aspect of the present application, phase comparison means for comparing the phase of the output signal of the phase detection means and a pulse signal corresponding to the speed command, and input of the phase comparison signal to give an operation amount to the operation target The position of the operation target having an actuator device such as a motor is controlled by the phase compensation means and the driver that drives the operation target.

  In the present invention, a high-resolution speed signal is generated by the phase detecting means, and the phase is compared with a pulse signal corresponding to an arbitrary speed command to perform PLL speed control.

  Further objects and other features of the present invention will be made clear by the preferred embodiments described below with reference to the accompanying drawings.

  According to the first aspect of the invention, by comparing the positional waveform of a plurality of phases corresponding to the position with the temporal waveform of the same shape having the predetermined frequency obtained by replacing the position with time, the predetermined waveform is obtained. By detecting the positional phase using the fact that all the waveforms match once within a period of one cycle of the frequency, the position detection resolution is enhanced and the detection delay is reduced.

  According to the second aspect of the present invention, it is possible to improve the position detection accuracy by generating the temporal waveform signal with reference to a highly accurate oscillator.

  According to the third aspect of the present invention, the stepped waveform output is smoothed to obtain an ideal waveform signal, and the positional phase detection resolution is enhanced.

  According to the fourth aspect of the invention, position detection at high speed can be performed while increasing the position detection resolution at low speed.

  According to the fifth aspect of the invention, by multiplying the sign level between the output signals when the output signal of the comparing means is represented by positive and negative signs by the exclusive OR means, the multiplication effect can be obtained with a simple configuration. It has been realized.

  According to the sixth aspect of the invention, the position detection accuracy is improved by removing the noise contained in the phase detection signal.

  According to the seventh aspect, the phase is obtained with respect to an arbitrary reference phase.

  According to the eighth aspect of the invention, the difference in amplitude between the positional waveform signal and the temporal waveform signal is detected, and the amplitudes of both waveforms are made equal to improve the phase detection accuracy.

  According to the ninth aspect, the difference in amplitude between the positional waveform signal and the temporal waveform signal is detected by the maximum value of the pulse width of the output signal of the exclusive OR means, so that the amplitude can be reduced by a small-scale digital circuit. The difference is detected.

  According to the tenth aspect of the invention, the amplitude of the positional waveform signal is adjusted by changing the power of the light source to adjust the amplitude in an analog manner with a simple configuration.

  According to the eleventh aspect of the invention, the difference between the offset levels of the positional waveform signal and the temporal waveform signal is detected and the offset levels of both waveforms are made equal to improve the phase detection accuracy.

  According to the twelfth aspect of the present invention, the difference between the offset levels of the positional waveform signal and the temporal waveform signal is detected by detecting the ratio of the high and low times within the predetermined time of the output pulse signal of the comparing means, By comparing with the value and detecting the difference in the offset level based on the comparison result, the difference in the offset level is detected by a small-scale digital circuit.

  In the thirteenth aspect of the invention, the offset level of the positional waveform signal is adjusted by changing the power of the light source to adjust the offset level in an analog manner with a simple configuration.

  According to the fourteenth aspect of the invention, high-precision speed control can be performed by generating a high-resolution speed signal by the phase detection means.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 shows an example of a circuit showing the first embodiment, and FIG. 2 shows waveforms of respective parts of FIG.

  In FIG. 1, 1 is a rotary encoder that outputs two-phase sinusoidal signals PA and PB with a 90 ° positional phase shift, and is attached to a rotating body (not shown) and has a value corresponding to the phase corresponding to the rotation angle. Is output. The rotary encoder 1 outputs two-phase sine wave signals PA and PB having a predetermined cycle per rotation according to the rotation speed of the rotating body. Reference numeral 2 denotes a quartz oscillator, and 3 denotes an 8-bit counter as an integration means for counting a high-frequency clock signal oscillated using the quartz oscillator 2 and outputting the count value. Reference numerals 4 and 5 denote ROMs for outputting waveform data in accordance with the output signal of the counter 3. The Sin waveform is written in the ROM 4 and the Cos waveform is written in the ROM 5 in advance, and data is set so as to generate a waveform having a predetermined cycle by an 8-bit parallel signal from 0 to 255 from the counter 4. Reference numerals 6 and 7 denote 8-bit D / A conversion means for converting 8-bit data output from the ROMs 4 and 5 into analog signals. Reference numerals 8 and 9 denote low-pass filters, for example, the sine wave output from the D / A conversion means 6 and 7 so as to smooth the waveform signal output from the outputs of the D / A conversion means 6 and 7 stepwise. The cut-off frequency is set to 10 times the frequency. Therefore, the output signals CA and CB of the low-pass filters 8 and 9 are two-phase sine wave signals with a 90 ° phase shift. The ROMs 4 and 5 are adjusted so that the sine wave signals PA and PB output from the rotary encoder 1 and the signals CA and CB output from the low-pass filters 8 and 9 have substantially the same value. Reference numerals 10 and 11 denote comparison means for comparing the two-phase output signals PA and PB of the rotary encoder 1 with the two-phase output signals CA and CB from the low-pass filters 8 and 9, respectively, and outputting the signals SA and SB as comparison results. ing. 12 is a timing detection means for inputting the output signals SA and SB of the comparison means 10 and 11, detecting that the timings of the changes of the two signals SA and SB are substantially the same timing, and outputting the detection timing signal Pdet. is there. Reference numeral 13 denotes phase detection means for detecting the count value output by the counter 4 at the detection timing of the Pdet signal and outputting a phase signal, and the temporal shift amount between the signal CA and the signal Pdet is detected as the phase shift amount. This temporal phase shift amount corresponds to the positional phase information of the output signal of the rotary encoder 1 and enables high-resolution position detection. This principle will be described with reference to FIG.

  The outputs PA and PB of the rotary encoder 1 having sine wave outputs with different 90 ° phases are two-phase sine waves represented by solid lines in FIG. 2 and are sine waves set with the same amplitude of the two phases output by the low-pass filters 8 and 9. The wave signals CA and CB are two-phase sine wave signals represented by broken lines in FIG. Signals PA and PB and signals CA and CB are input to comparison means 10 and 11, respectively, and signals SA and SB are output. Then, the timing detecting means 12 detects a portion where the pulse edges of the signals SA and SB are substantially equal, and outputs a signal Pdet. Here, since the output signal of the counter 3 is the phase information of the signal CA, the phase relationship with the signal Pdet using the CA ′ signal indicating the sign of the signal CA is used to determine the output signals PA and PB of the rotary encoder 1. It can be seen that the phase difference between the signal Pdet and the signal CA ′ gradually changes to large values such as P0, P1, P2, P3, and P4 according to the change.

  FIG. 3 shows a waveform when the rotation direction of a rotating body (not shown) is switched. The signals PA and PB in the figure are in the middle of the figure, the phase is inverted, and the state is switched from the state in which the phase of the signal PB is delayed with respect to the signal PA. The period of the signal Pdet is gradually longer, and the phase relationship between the signal Pdet and the signal CA ′ is almost at the center. On the left side, the phase of the signal Pdet gradually decreases with time. Indicates that the phase delay of the signal Pdet gradually increases with time, and the rotation direction of the rotating body (not shown) is reversed. Here, since the period or frequency of the Pdet signal changes according to the rotational speed including the rotational direction, the phase of the pulse signal having the frequency corresponding to the speed command and the signal Pdet is compared to determine the motor speed. If PLL control is performed, speed control including the rotation direction can be performed.

  FIG. 4 shows a block diagram of the control device in this case. 4 in FIG. 4 is a known phase controller for PLL control, and a pulse signal for speed command and a Pdet signal are inputted from command means (not shown), and 15 is a motor which removes noise from the phase comparison signal and which will be described later. Filter means for setting the control gain of the speed control 17, 16 a driver for driving the motor 17, 17 a motor, and the rotary encoder 1 connected to the rotary shaft. Briefly, when the motor 17 is stopped, pulse signals having the same frequency as the sine wave signals CA and CB output from the low-pass filters 8 and 9 are input to the phase comparator 14 from command means (not shown). . Since the pulse signal having the same frequency as the sine wave signals CA and CB is also output from the signal Pdet when the motor 17 is stopped, the motor 16 is controlled to stop by the driver 16 so that the output of the phase comparator 14 becomes zero. The Here, when a pulse signal having a frequency lower than the sine wave signals CA and CB is input to the phase comparator 14 from a command means (not shown), the output of the phase comparator 14 becomes a negative value, and the motor 17 rotates in the CCW direction. It rotates at the rotation speed according to the speed command signal. Conversely, when a speed command signal having a frequency higher than that of the sine wave signals CA and CB is input to the phase comparator 14, the motor 17 rotates in the CW direction and speed control is performed.

  In this example, the position detection signal is multiplied for the rotary encoder that generates a two-phase signal having a 90 ° positional phase, but a three-phase signal is generated having a 120 ° positional phase. Even when an encoder is used, it is natural that the same effect can be obtained if the phase difference of the temporal waveform as a comparison signal is set to the same 120 ° and compared.

  FIG. 5 shows an example of the waveform in that case. The three-phase signals with shifted phase phases were designated as signals PA, PB, and PC, and the signals with shifted temporal phases were designated as signals CA, CB, and CC. Solid lines in the figure indicate signals PA, PB, and PC, and broken lines indicate signals CA, CB, and CC. Then, the comparison results of the signals PA, PB, PC and the signals CA, CB, CC are taken as signals SA, SB, SC, and the same timing of all the edges of the signals SA, SB, SC is detected and shown in the signal Pdet2, as shown in FIG. The signal CA 'was also displayed on the sway. The phase relationship between the signal Pdet2 and the signal CA 'is almost the same as that in FIG. This is because the frequencies of the signals PA, PB, and PC in FIG. 5 are the same as the signals PA and PB in FIG.

  FIG. 6 is a block diagram showing a second embodiment, in which an exclusive OR element 18 is used in place of the timing detection means 12 of FIG.

  FIG. 7 shows the waveform at this time. The output signals SA and SB of the comparison means 10 and 11 are the same as those in FIG. 3, but the output signal Pdet1 of the exclusive OR element 18 in FIG. 6 has a frequency opposite to that of the signal Pdet in FIG. Understand. In other words, the frequency on the left side is higher than that on the right side from the approximate center of FIG. 3, whereas the signal Pdet1 in FIG. 7 has a lower frequency on the left side. However, considering this opposite characteristic, it is obvious that the same operation as in FIG. 4 can be performed in the block diagram of FIG.

  FIG. 8 shows an example in which an exclusive OR element 18 is used instead of the timing detection means 12 of FIG. Similarly to the embodiment of FIG. 6, this is the same operation as the embodiment of FIG. 1 except that the change of the phase signal is reversed according to the rotation direction of the rotating body (not shown). Here, as a result of using the exclusive OR element 18, the principle of changing the frequency of the signal Pdet1 according to the rotational speed of a rotating body (not shown) as shown in FIG. 7 will be described. First, the output signals PA and PB of the rotary encoder 1 are expressed by the following equations.

  Here, φ indicates a positional phase. Next, the output signals CA and CB of the low-pass filters 8 and 9 are

  And Here, ω represents an angular frequency, and t represents time.

  Therefore, the following formula is derived by multiplying the result of subtracting the signal CA from the signal PA and the result of subtracting the signal CB from the signal PB.

It becomes. Here, since (cos (φ−ωt) −1) of the second multiplication term in the equation (5) is 0 or less, the equation (5) is amplitude-modulated by the second multiplication term and the angular frequency has a phase of φ. This is a sine wave of ω. Then, the output signal PA of the rotary encoder 1, consider the case where PB is changing over time, the φ When ω _{p t} (5) Equation

It becomes. Thus, Equation (6) is considered to be a sine wave having an angular frequency ω _p + ω that is amplitude-modulated by (cos ((ω _p −ω) t) −1) of the second term of multiplication. Here, consider the circuit of this embodiment. The comparison means 10 and 11 perform operations of V _PA -V _CA and V _PB -V _{CB in} the formula (5). However, the outputs of the comparison means 10 and 11 are binary outputs of 0 and 1, and the exclusive OR element 18 is used instead of multiplication, so that the calculation formula does not follow. Here, the relationship of this equation is shown in Table 1 for comparison.

Thus, it can be seen that + and 0, and-and 1 correspond to the sign of the multiplication result and the output of the exclusive OR element 18, respectively. Therefore, since the timing at which the sign changes coincides with the pulse edge of the output signal of the exclusive OR element 18, the frequency of the output signal of the exclusive OR element 18 matches ω _p + ω in the equation (6). Become. In this way, a multiplication effect can be produced by a simple digital element without multiplication using an expensive analog multiplier, and a pulse signal having a frequency corresponding to the rotational speed of a rotating body (not shown) can be generated.

  FIG. 9 shows a block diagram of the third embodiment. In the description of the mathematical expression of the second embodiment, it has been described that the amplitudes of PA, PB, CA, and CB are equal to each other. The waveform of each part in that case is shown in FIG. The main part of FIG. 9 is the same as that of the above-described embodiment. However, in this embodiment, measures are taken when PA, PB, CA, and CB amplitudes are different.

  Here, before explaining the block diagram of FIG. 9, the waveform of the signal Pdet1 when the amplitudes are different will be described with reference to FIG. In FIG. 10, the signals PA and PB are sinusoidal waveforms indicated by solid lines, and the signals CA and CB are displayed in a case where the amplitude is larger than that of the signals PA and PB and the case where the amplitude is smaller than the signals PA and PB. . Next, regarding the Pdet1 signal, the cases where the signals CA and CB are larger, smaller, and equal than the signals PA and PB are shown. As can be seen from the figure, if the amplitudes of the signals PA and PB and the signals CA and CB are not equal, many thin pulses appear in the Pdet1 signal. Then, it becomes difficult to detect the phase of the signal Pdet1, and malfunction may occur. Therefore, in this embodiment, a low-pass filter for removing a thin pulse signal included in the signal Pdet1 is provided.

  Here, the block diagram of FIG. 9 will be described. In the above embodiment, the 8-bit signal from the counter 3 is input to the ROMs 4 and 5, but in the present embodiment, the upper 4 bits of the counter 3 are input to the ROMs 4 and 5. The D / A conversion means 6 and 7 and the low-pass filters 8 and 9 are the same as in the above embodiment. By using 4-bit data, the capacity of the ROMs 4 and 5 can be reduced, and the timing detection means 13 is also input with the lower 4-bit data from the counter 3, so that the positional phase detection resolution does not change. It is configured. Further, instead of the rotary encoder 1, the LED 19, the resistor R, the optical scale 20, the attending elements PD1 to PD4, and the detection signals of the four photodiodes PD1 to PD4 are used for the two phases corresponding to the movement of the optical scale 20. An optical position sensor composed of a differential amplifier 21 that outputs a signal having a sine wave waveform is used.

  The amplitude difference between the signals PA and PB and the signals CA and CB, which is a problem in this embodiment, can be dealt with by changing the value of the resistor R to change the value of the current flowing in the LED 19 and adjusting the emission intensity of the LED 19. Is also possible. Reference numeral 22 denotes a noise filter for removing a thin pulse generated in the signal Pdet1 when the signals PA and PB and the signals CA and CB have different amplitudes. The digital filter mainly passes only a signal having a predetermined pulse width or more. Used. In this embodiment, an example of an optical rotary encoder is shown. However, this is used for a signal multiplying process of a linear encoder, a magnetic encoder, or a known resolver or laser interferometer that generates a similar output signal for a position. You may do it.

  FIG. 11 is a block diagram showing the fourth embodiment. In this embodiment, it is detected from the Pdet1 signal which of the signals PA and PB and the signals CA and CB is larger, and the light emission intensity of the light source LED 19 constituting the optical position detection sensor is controlled.

  Here, a method for detecting which of the signals PA and PB and the signals CA and CB is larger will be described using the waveform of FIG. When attention is paid to the pulse width of the signal Pdet1 in FIG. 10, it can be seen that the maximum value of the pulse width when the signals CA and CB are large is smaller than the maximum value of the pulse width when the signals CA and CB are small. In addition, even when the signals CA and CB are large and small, thin pulses generated when the signals PA and PB and the signals CA and CB have different amplitudes are removed by filtering, and the time for several cycles is measured. If the time per cycle is calculated, the pulse width when the signals CA and CB have the same amplitude as the signals PA and PB can be obtained, and it is possible to detect which of the signals PA and PB and the signals CA and CB is larger. is there.

  FIG. 11 is a block diagram for realizing this, 23 is a maximum pulse width detecting means for detecting the maximum pulse width by inputting the signal Pdet1, 24 is a signal Pdet1 and the signals PA, PB and the signal by the above method. An ideal pulse width detecting means for detecting the pulse width when the amplitudes of CA and CB are equal, 25 is a differential amplifier for detecting the difference between the output of the maximum pulse width detecting means 23 and the output signal of the ideal pulse width detecting means, and 26 is An integrating means for integrating the output signal of the differential amplifier 25. If the signals CA and CB have larger amplitudes than the signals PA and PB, the maximum pulse width becomes smaller than the ideal pulse width of the signal Pdet1, so that the differential amplifier 25 Output becomes a positive value, the integration result signal that is the output of the integrating means 26 increases, the light emission intensity of the light source LED 19 increases, and the amplitudes of the signals PA and PB increase. Is to go, signal PA, PB signal CA, and is configured so that the amplitude of the CB are equal.

  In the fourth embodiment, the outputs of the photodiodes PD1 and PD3 and PD2 and PD4 are different so that the offset levels of the signals PA and PB do not change even if the light emission intensity of the light source LED 19 changes. Because of dynamic amplification, the light emission intensity of the light source LED 19 is changed to adjust the difference in amplitude between the signals PA and PB and the signals CA and CB. In this example, when the light emission intensity of the light source LED 19 is changed, the signal PA, An example in which the amplitude and offset level of PB change simultaneously is shown.

  FIG. 12 is a block diagram showing the present embodiment, and FIG. 13 shows waveforms of respective parts. The first feature of this example is that the number of photodiodes that receive light from the light source LED 19 is two, that is, PD1 and PD2 compared to four in the fourth embodiment. As a result, the amplitudes and offset levels of the signals PA and PB change depending on the change in the light emission intensity of the light source LED 19. Further, the waveforms of the signals PA and PB that change due to a change in the position of the optical scale 20 that moves in accordance with the movement of a moving body (not shown) are asymmetrical in the vertical direction. The second feature is that the difference between the offset levels of the signals PA and PB and the signals CA and CB is performed by switching the tables of the ROMs 4 and 5 storing the waveform data. The third feature is that the same waveforms as the vertically asymmetric waveforms of the signals PA and PB are stored in the ROM 4 and ROM 5.

  Hereinafter, a part for realizing the second feature which is a new component will be described with reference to FIG. FIG. 13 shows an example of waveforms when the signals PA and PB have the same amplitude and different offset levels as the signals CA and CB. The signals PA and PB are solid line waveforms, and the upper and lower waveforms are asymmetric. The signals CA and CB are represented by broken lines and have the same waveforms as the signals PA and PB. In the example where the offset levels of the signals CA and CB are small, it can be seen that the pulses of the signals SA and SB are often low.

  When the offset levels of the signals PA and PB and the signals CA and CB are the same, the signals SA and SB are output with waveforms having a substantially equal ratio between the high level and the low level. Therefore, the offset levels of the signals PA and PB are detected by detecting the ratio of the time between the high level and the low level of the signals SA and SB while moving the moving body (not shown), and the offset levels of the signals CA and CB are changed. Thus, the offset levels of the signals PA and PB and the signals CA and CB can be matched. Then, by matching the signal amplitudes of the signals PA and PB and the signals CA and CB based on the method of the fourth embodiment, the signals PA and PB and the signals CA and CB become signals having the same amplitude and offset level.

  Now, a configuration for realizing this will be described with reference to FIG. Reference numeral 27 denotes a high / low ratio detecting means for inputting the signal SA to detect the ratio between the high level and the low level of the signal SA. Offset setting means. The waveform data of the ROMs 4 and 5 are selected so that the high / low ratio is normally 50%. The ROM 4 and 5 store waveform data of a plurality of offset levels divided into a plurality of blocks, and the offset levels of the signals CA and CB are changed by selecting the blocks by the offset setting means 28. In this example, the high / low ratio detecting means 27 detects the high / low ratio for the signal SA, but the signal SB may also be obtained and the result of the signal SA may be averaged.

  In the above embodiment, the position is detected using the output of the phase detection means 13, but there is no problem if the signals PA and PB generate only one period of the waveform within the moving range of the moving body (not shown). When generating a waveform signal, it is necessary to count how many periods it has moved.

  FIG. 14 is a block diagram showing a first example of this embodiment, in which 29 is inputted with signals PA and PB, converted into a pulse signal with a duty of 50%, and converted into a two-phase pulse signal. This is a position counter that counts the position by four times. By using the position signal which is the output of the position counter and the phase signal of the phase detection means 13, the position counter 29 counts the periods of the signals PA and PB even when the signals PA and PB output waveforms for many periods. At the same time, since the phase detection means 13 can detect the phase within one cycle of the signals PA and PB with high resolution, the dynamic range of position detection can be widened.

  Reference numeral 30 denotes integration means for integrating resolution command signals from command means (not shown) at the timing of the oscillation frequency of the crystal resonator 2. When the integrated value exceeds 255, the integrating means 30 continues the integration from the excess value at the next integration timing. Therefore, the output of the phase detection means 13 is output according to the resolution of the resolution command. In practice, however, there is a problem that the phase output from the phase detector 13 and the count phase of the position counter 29 are slightly shifted. Such a case can be dealt with by selectively using the position signal and the phase signal by a calculation means (not shown).

  For example, when the optical scale 20 moves at a high speed, the position is detected using only the value of the position counter 29 without using the phase signal that is the output of the phase detection means 13, and when the optical scale 20 moves at a low speed, the phase is detected. In this method, a carry (exceeding 360 degrees or exceeding 0 degrees) of the phase signal, which is the output of the detection means 12, is detected and the phase signals are accumulated and calculated.

  FIG. 15 is a flowchart showing this operation. The operation of this flowchart is performed every predetermined time, and shows a case where the position detection resolution is 256 (when the phase signal is output from 0 to 255). When the operation timing comes, first the position signal P0 and the phase signal PH0 are detected. Then, the absolute value Pd of the difference between the previous position signal P1 and the position signal P0 is calculated, and it is determined whether Pd is larger than a predetermined value Pd0. When Pd is larger than Pd0, it is considered that the optical scale 20 is moving at high speed, the position information Pout is set to a value 64 times P0, and the switching flag CH is set to 0. Further, when Pd is equal to or less than Pd0, it is detected whether or not the switching flag CH is 1. If it is 0, the position information Pout is set to a value 64 times P0, and if the phase signal PH0 is between 85 and 170, the switching flag CH is set to 1. When the switching flag CH is 1, the difference PHd between the previous phase signal PH1 and the phase signal PH0 is calculated, the lower 8 bits of the position information Pout are deleted, and the value obtained by adding the phase signal PH0 is substituted into the position information Pout. . When PHd is 85 or more, 256 is subtracted from position information Pout, and when PHd is -85 or less, 256 is added to position information Pout. After calculating the position information Pout in this way, the current position signal P0 and the phase signal PH0 are assigned to P1 and PH1, respectively, and the process ends.

  Here, the position is detected when the optical scale 20 moves at high speed using the position counter 29. However, when it is guaranteed that the optical scale 20 moves at a sufficiently slow speed, only the phase information is obtained. It may be used to calculate the cumulative position.

  FIG. 16 is a flowchart showing this example. The operation of this flowchart is also performed every predetermined time, and shows a case where the position detection resolution is 256 (when the phase signal is output from 0 to 255). When the operation timing comes, the phase signal PH0 is first detected. First, the difference PHd between the previous phase signal PH1 and the phase signal PH0 is calculated, the lower 8 bits of the position information Pout are deleted, and the value obtained by adding the phase signal PH0 is substituted into the position information Pout. Next, when PHd is 85 or more, 256 is subtracted from the position information Pout, and when PHd is smaller than −85, 256 is added to the position information Pout. After the position information Pout is calculated in this way, the current phase signal PH0 is assigned to PH1 and the process ends. Even in the case of FIG. 16 where the phase is calculated using only the phase signal, the frequency of the signals CA and CB is increased by changing the resolution command Sd from the command means (not shown) to a large value. Therefore, when the phase signal changes quickly, the resolution command Sd may be set to a large value.

  FIG. 17 shows a flowchart in this case. Basically, the operation is the same as that of FIG. 16, but when the absolute value of the phase signal change PHd is smaller than 10, it is determined that the moving speed of the optical scale 20 is slow. It is set to be half the value, the frequency of the signals CA and CB is lowered, and the phase detection resolution of the phase detection means 13 is increased. If the absolute value of the phase signal change PHd is larger than 40, it is determined that the moving speed of the optical scale 20 is fast. If the resolution command Sd is not the maximum, Sd is set to double, and the signals CA and CB The frequency is set to be high and the phase detection resolution of the phase detection means 13 is set to be low.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

It is a block diagram which shows a 1st Example. It is a timing chart which shows the waveform of each part of the 1st example. It is a timing chart which shows the waveform of each part of the 1st example. It is a block diagram which shows a 1st Example. It is a timing chart which shows the waveform of each part of the 1st example. It is a block diagram which shows a 2nd Example. It is a timing chart which shows the waveform of each part of the 2nd example. It is a block diagram which shows a 2nd Example. It is a block diagram which shows a 3rd Example. It is a timing chart which shows the waveform of each part of the 3rd example. It is a block diagram which shows a 4th Example. It is a block diagram which shows a 5th Example. It is a timing chart which shows the waveform of each part of the 5th example. It is a block diagram which shows a 6th Example. It is a flowchart which shows a 6th Example. It is a flowchart which shows a 6th Example. It is a flowchart which shows a 6th Example.

Explanation of symbols

1 Rotary encoder 2 Crystal resonator 3 Counter 4 ROM
5 ROM
6 D / A conversion means 7 D / A conversion means 8 Low-pass filter 9 Low-pass filter 10 Comparison means 11 Comparison means 12 Timing detection means 13 Phase detection means 14 Phase comparator 15 Filter means 16 Driver 17 Motor 18 Exclusive OR element 19 LED
DESCRIPTION OF SYMBOLS 20 Optical scale 21 Differential amplifier 22 Noise filter 23 Maximum pulse width detection means 24 Ideal pulse width detection means 25 Differential amplifier 26 Integration means 27 Hi / Lo ratio detection means 28 Offset setting means 29 Position counter

Claims (17)

A position detecting means for outputting a plurality of positional waveform signals having different positional phases corresponding to a relative position with a measurement object,
Signal generating means for generating a plurality of temporal waveform signals having the same shape and different phases as the plurality of positional waveform signals;
A plurality of comparing means for respectively comparing the plurality of positional waveform signals and the plurality of temporal waveform signals;
Phase detection means for inputting the output of the comparison means and outputting phase information of the positional waveform signal.   The signal generating means for generating the temporal waveform signal includes an oscillator for generating a clock signal of a reference frequency, an integrating means for integrating a predetermined value at the timing of the clock signal, and a predetermined value according to the integrated value of the integrating means The position detection means according to claim 1, further comprising: a waveform generation means for generating an analog signal of value.   3. The position detecting means according to claim 2, wherein the signal generating means for generating the temporal waveform signal has a low-pass filter connected to an output signal of the waveform generating means.   The position detection means according to claim 2 or 3, wherein the predetermined number of times is switched according to a frequency of the positional waveform signal.   5. The position according to claim 1, wherein the phase detection unit is configured to invert the output signal when the output signals of the plurality of comparison units change substantially simultaneously. Detection means.   The position detection means according to any one of claims 1 to 4, wherein the phase detection means is an exclusive OR means for performing an exclusive OR between output signals of the comparison means.   7. A filter unit that receives an output signal of the phase detection unit and does not change the output when the pulse width of the output signal is narrower than a predetermined pulse width. The position detection means described in.   The position according to any one of claims 1 to 7, further comprising: a phase difference detection unit that inputs an output signal of the phase detection unit and outputs a phase difference signal indicating a phase difference with respect to a reference phase signal. Detection means.   Amplitude comparison means for detecting a difference in amplitude between the positional waveform signal and the temporal waveform signal, and amplitude adjustment means for adjusting the amplitude to reduce the amplitude difference according to the output of the amplitude comparison means are provided. The position detecting means according to any one of claims 1 to 8, wherein the position detecting means is provided. A position detecting means for outputting a plurality of positional waveform signals having different positional phases corresponding to a relative position with a measurement object,
Signal generating means for generating a plurality of temporal waveform signals having the same shape and different phases as the plurality of positional waveform signals;
A plurality of comparison means for respectively comparing the plurality of positional waveform signals and the plurality of temporal waveform signals;
Phase detection means for inputting the output of the comparison means and outputting phase information of the positional waveform signal;
Exclusive OR means for performing an exclusive OR operation by inputting the output of the comparison means;
Maximum pulse width detecting means for detecting a maximum pulse width within a predetermined time of the pulse width of the output pulse signal of the exclusive OR means; and
An amplitude adjusting means for adjusting an amplitude of at least one of the positional waveform signal and the temporal waveform signal so as to reduce an amplitude difference in accordance with an output of the maximum pulse width detecting means. Detection means.   The position detection means according to claim 10, wherein the phase detection means also serves as the exclusive OR means.   The position detection means according to any one of claims 9 to 11, wherein the amplitude adjustment means adjusts the power of a light source.   Offset comparison means for detecting a difference in offset level between the positional waveform signal and the temporal waveform signal, and an offset for adjusting the offset level so as to reduce the difference in the offset level according to the output of the offset comparison means The position detecting means according to any one of claims 1 to 12, further comprising an adjusting means. A position detecting means for outputting a plurality of positional waveform signals having different positional phases corresponding to a relative position with a measurement object,
Signal generating means for generating a plurality of temporal waveform signals having the same shape and different phases as the plurality of positional waveform signals;
A plurality of comparison means for respectively comparing the plurality of positional waveform signals and the plurality of temporal waveform signals;
Phase detection means for inputting the output of the comparison means and outputting phase information of the positional waveform signal;
A high / low ratio detection means for detecting a ratio between a high time and a low time within a predetermined time of the output pulse signal of the comparison means;
An offset adjusting means for adjusting an offset level of at least one of the positional waveform signal and the temporal waveform signal in accordance with the output of the high / low ratio detecting means.   The position detection means according to claim 14, wherein the phase detection means is an exclusive OR means for performing an exclusive OR between output signals of the comparison means.   16. The position detection unit according to claim 14, wherein the offset adjustment unit adjusts the power of a light source.   Phase comparison means for comparing the phase of the output signal of the phase detection means and the pulse signal corresponding to the speed command, phase compensation means for inputting an operation amount to the operation object by inputting the phase comparison signal, and a driver for driving the operation object And a position detecting means according to any one of claims 1 to 16.

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