JP2004239829A - Original point detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely detect a position of a specific original point regardless of direction of a relative movement of an incremental encoder. <P>SOLUTION: A directional signal obtained from a periodic signal for increment measurement output from the increment encoder via an interpolation circuit 11, indicating the direction of the relative movement of the incremental encoder is compared with a specific comparison value by the comparator 12. The directions of the relative movement are discriminated, and the original point signal is generated by the gate circuit 15 based on the fixed point signal output from the incremental encoder and the result of the discrimination of directions of the relative movement. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an origin detection device suitable for application to a scale device for detecting a relative displacement amount between two members that are relatively displaced in, for example, a machine tool or a precision measuring device.
[0002]
[Prior art]
In a scale device that detects the relative displacement between two members that are relatively displaced in a metal working machine, a precision measuring device, or the like, for example, a phase modulation signal corresponding to the relative displacement is obtained by an optical incremental encoder or a magnetic incremental encoder, By comparing the cycle of the phase modulation signal with the cycle of the reference signal, an incremental signal representing the relative displacement is generated, and the displacement is obtained by counting the incremental signal. An interpolation process is performed to increase the accuracy.
[0003]
Conventionally, an incremental encoder has a function of outputting a signal representing an absolute origin (hereinafter, referred to as an origin signal) in order to realize highly accurate and highly reliable measurement. For example, the scale for the fixed point signal is recorded separately from the scale for the incremental signal, and the fixed point signal itself obtained from the scale for the fixed point signal is used as the origin signal, or one incremental signal is used with the fixed point signal as a gate. An origin signal is obtained by making a selection (for example, see Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 10-104017
[Problems to be solved by the invention]
Meanwhile, in the high-precision incremental encoder, the period of the periodic signal for incremental measurement has been particularly short in recent years in order to improve the interpolation accuracy.
[0006]
In the conventional incremental encoder in which the wavelength (period) of the periodic signal for incremental measurement is about 20 μm, as shown in FIG. 20, it is possible to obtain a fixed-point signal having substantially the same period corresponding to the period of the incremental signal, As a result, a fixed position of the incremental signal was detected, and the fixed-point signal was used as a gate to select one of the incremental signals as the origin signal.
[0007]
However, when the wavelength (period) of the periodic signal for incremental measurement becomes shorter, it becomes difficult to generate a fixed-point signal having substantially the same period corresponding to the period of the incremental signal.
[0008]
Therefore, in the case where the wavelength (period) of the periodic signal for incremental measurement is set to 4 μm or less, as shown in FIG. 21, a fixed-point signal having a longer period of about 10 to 100 times that of the incremental signal is generated. Then, a method of using the edge of the fixed-point signal, that is, a change point of the signal as the origin, or a method of using the fixed-point signal by gating and using the first incremental signal when the fixed-point signal becomes active, is considered.
[0009]
However, in either case, there is a problem that a different origin position is detected depending on the relative movement direction of the incremental encoder.
[0010]
Accordingly, an object of the present invention is to provide an origin detection device capable of reliably detecting a specific origin position regardless of the relative movement direction of an incremental encoder in view of the above-described conventional problems. It is in.
[0011]
[Means for Solving the Problems]
In the present invention, a specific origin position is detected regardless of the relative movement direction of the incremental encoder by discriminating the relative movement direction of the incremental encoder based on the periodic signal for incremental measurement.
[0012]
That is, the present invention is an origin detection device in a scale device including an incremental encoder that outputs a periodic signal for incremental measurement and a fixed point signal for detection of an origin, wherein the incremental measurement periodic signal output from the incremental encoder is A directional signal generating means for generating a directional signal indicating a relative moving direction of the incremental encoder based on the directional signal, and discriminating a relative moving direction of the incremental encoder based on the directional signal generated by the directional signal generating means. Discriminating means; and origin signal generating means for generating an origin signal based on the fixed point signal output from the incremental encoder and a discrimination result of the relative movement direction of the incremental encoder by the discriminating means. .
[0013]
In the origin detection device according to the present invention, the origin signal generating means includes, for example, a rising edge and a falling edge of the fixed point signal based on the discrimination result in the relative movement direction of the incremental encoder by the fixed point signal and the discrimination means. Is selected as the origin signal.
[0014]
Also, in the origin detection device according to the present invention, the origin signal generating means may be, for example, a signal for the origin periodically generated from an incremental measurement periodicity signal relative to the fixed point signal and the incremental encoder by the discriminating means. The moving direction is gated based on the discrimination result and the fixed point signal to be an origin signal.
[0015]
Further, in the origin detection device according to the present invention, the directional signal generating means includes, for example, a change amount of an interpolated incremental value generated based on an incremental measurement periodic signal output from the incremental encoder. Is detected as a directional signal by detecting the polarity of the change for each unit time.
[0016]
Further, the origin detecting device according to the present invention includes, for example, an integrating means for integrating a directional signal supplied from the directional signal generating means to the origin signal generating means.
[0017]
In the origin detection device according to the present invention, the integration means may include, for example, an up-down counter whose count operation is controlled by a count control signal obtained by binarizing a direction signal generated by the direction signal generation means. Become.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0019]
First, the present invention is applied to an origin detecting device that detects a rising edge or a falling edge of a fixed point signal as an origin position in a scale device including an incremental encoder that outputs a periodic signal for incremental measurement and a fixed point signal for origin detection. Will be described.
[0020]
The origin detection device according to the present invention is configured, for example, as shown in FIG.
[0021]
The origin detecting device 10 shown in FIG. 1 is applied to an optical scale device in which a scale for an incremental signal and a scale for a fixed point signal are recorded, and a two-phase output from an incremental encoder of the scale device. An interpolation circuit 11 to which the periodic signals A and B for incremental measurement are input, a comparator 12 to which a directional signal obtained by the interpolation circuit 11 is supplied, and a fixed-point signal C obtained by the incremental encoder are supplied. And a gate circuit 15 for outputting an origin signal. The outputs of the comparator 12, the rising differentiator 13 and the falling differentiator 14 are supplied to the gate circuit 15. It has a configuration.
[0022]
In the origin detecting device 10, the two-phase incremental measurement periodic signals A and B supplied to the interpolation circuit 11 are relative to a measurement object generated based on a scale for an incremental signal by an incremental encoder. For example, it is a phase modulation signal corresponding to the displacement amount. The fixed point signal C supplied to the rising differentiator 13 and the falling differentiator 14 is obtained by binarizing a signal indicating a fixed point position generated by an incremental encoder based on a scale for the fixed point signal.
[0023]
The interpolation circuit 11 outputs an incremental value obtained by interpolating the period of the incremental signal from the two-phase incremental measurement periodic signals A and B.
[0024]
As an interpolation method of an incremental signal, for example, a vector addition method or a phase modulation method as an interpolation method of a two-phase signal having a phase difference of 90 °, a sine wave signal SIN and a cosine wave signal COS as shown in FIG. There is known a method of digitizing by the D converters 11A and 11B and reading out a value (θ, R) obtained by performing tan- ¹ conversion from the look-up table 11C. Further, as an interpolation method of a three-phase signal having a phase difference of 120 °, as shown in FIG. 3, a method of interpolating only an amplitude level using only a linearly approximated portion is known.
[0025]
Further, the interpolation circuit 11 generates and outputs a directional signal indicating a relative movement direction of the incremental encoder with respect to the measurement object based on the two-phase incremental measurement periodic signals A and B. The interpolation circuit 11 detects, for example, the polarity of the change in the amount of change of the incremental value per unit time, and uses the detected polarity as a directional signal.
[0026]
The comparator 12 compares the signal level of the directional signal generated by the interpolation circuit 11 with a predetermined comparison value, thereby discriminating the relative movement direction of the incremental encoder with respect to the measurement object, and The converted directional signal is supplied to the gate circuit 15 as a gate control signal GC.
[0027]
Here, the binarized directional signal indicates a forward direction by a logic H and a reverse direction by a logic L with respect to the relative movement direction of the incremental encoder with respect to the measurement object.
[0028]
The rising differentiator 13 and the falling differentiator 14 differentiate the binarized fixed-point signal C supplied from the incremental encoder, thereby obtaining a rising differential signal UD and a falling differential corresponding to the rising edge of the fixed-point signal C. A falling differential signal DD corresponding to the edge is generated and supplied to the gate circuit 15.
[0029]
The gate circuit 15 is controlled as follows by supplying the binarized directional signal as the gate control signal GC.
[0030]
That is, as shown in the timing chart of FIG. 4, the operation of the origin detecting device 10 is such that when the binarized directional signal is logic H, that is, the relative position of the incremental encoder with respect to the measurement object is increased. When the moving direction is the positive direction, the gate is opened for the rising differential signal UD and the gate is closed for the falling differential signal DD, so that the rising differential signal UD is selected and output as the origin signal. When the binarized directional signal is logic L, that is, when the direction of the relative movement of the incremental encoder with respect to the object to be measured is in the opposite direction, a gate is opened for the falling differential signal DD and the rising differential signal UD , The falling differential signal DD is selected and output as the origin signal.
[0031]
As described above, in the origin detecting device 10, the rising differential signal UD or the falling differential signal DD is selected as the origin signal by the gate circuit 15 according to the relative movement direction of the incremental encoder with respect to the measurement object. Regardless of the relative movement direction of the incremental encoder with respect to the measurement object, an origin signal indicating a specific origin position can be output.
[0032]
Here, when the interpolation circuit 11 detects the polarity of the change in the amount of change of the incremental value per unit time and uses it as a directional signal, the change in the incremental value originally moves as shown in FIG. It indicates the direction opposite to the direction in which it occurs, and may generate an incorrect origin signal. This is caused by disturbance or noise when the amount of change per unit time is small. The frequency of occurrence of this state becomes more pronounced as the amount of change per unit time decreases.
[0033]
However, when the incremental encoder is moving, the duty ratio of the directional signal has a higher value ratio indicating the moving direction. When the directional signal whose duty ratio changes in this way is integrated, the integrated directional signal changes as a voltage value according to the duty ratio as shown by a thick line in FIG. Hardly follows.
[0034]
Therefore, by providing an integrator 21 for integrating the directional signal supplied from the interpolation circuit 11 to the comparator 12 as in the origin detecting device 20 shown in FIG. The origin can be reliably detected without making a mistake in sex discrimination.
[0035]
That is, by filtering the directional signal by integrating the directional signal and comparing the directional signal with a predetermined comparison value by the comparator 12, the current accurate moving direction can be obtained. In addition, it is possible to ignore the temporarily generated signal in the opposite direction, and thereby it is possible to accurately grasp the reading direction of the origin.
[0036]
Since the other components of the origin detecting device 20 shown in FIG. 7 are the same as those of the origin detecting device 10 shown in FIG. 1, the same reference numerals are given in FIG. 7 and the detailed description is omitted.
[0037]
Here, as the integrator 21, for example, as shown in FIG. 8, an integrator 21A having a simple circuit configuration including a capacitor C and a resistor R can be used. When a large time constant is required, an active integrator 21B including a capacitor C, a resistor R, and an operational amplifier OP may be used as shown in FIG.
[0038]
Further, it goes without saying that a digital filter can be used as the integrator 21, but it can also be realized by a relatively simple digital circuit using a counter, for example, as shown in FIG.
[0039]
The integrator 21C shown in FIG. 10 includes a 4-bit up / down counter 22 and a control circuit 23 for controlling the operation of the up / down counter 22.
[0040]
The 4-bit up / down counter 22 is supplied with a clock signal via a control circuit 23 to a clock terminal CLK, and counts a directional signal output from the interpolation circuit 11 as a count control signal. It is supplied to terminal DIR.
[0041]
The control circuit 23 is supplied with the directional signal output from the interpolation circuit 11, the 4-bit outputs Q0 to Q3 of the up / down counter 22, and the clock signal CLK.
[0042]
As shown in FIG. 11, the up / down counter 22 retains “7” without taking a count value larger than “7” in the addition direction, and holds “8” in the subtraction direction, even if the incremental encoder is moving. The count operation is controlled so as to maintain “8” without taking a smaller count value, and the most significant bit Q3 of the count outputs Q0 to Q3 is used as a direction signal.
[0043]
In the integrator 21C having such a configuration, when the directional signal is completely in one direction, the count value is "7" or "8", and the duty in the addition direction can be ignored up to eight samples. In the subtraction direction, signals in the reverse direction can be ignored up to 16 samples.
[0044]
In the above description, only the directional signal has been described. However, a binarized directional signal can be generated by cumulatively adding and subtracting the incremental value obtained by the interpolation circuit 11.
[0045]
For example, the integrator 21 can be configured by hard logic as shown in FIG.
[0046]
An integrator 21D shown in FIG. 12 is an example of an integrator using a phase accumulator. And a latch circuit 26 for setting the lower limit value and a latch circuit 26 for latching an addition / subtraction value output from the adder / subtractor 24 via the limiter circuit 25 and inputting the input to the adder / subtractor 24. Is used as the direction signal.
[0047]
In the integrator 21D having such a configuration, since the difference value of the incremental value obtained by the interpolation circuit 11, that is, the deviation for each sample is cumulatively added / subtracted (integrated), the increase / decrease value does not change unless movement is involved. Since the purpose of the adder / subtractor 24 in this case is not to obtain the distance, the upper limit value and the lower limit value of the addition / subtraction value by the adder / subtractor 24 are set by the limiter circuit 25. FIG. 13 shows the data movement of the adder / subtractor. The upper limit value and the lower limit value (in the example of FIG. 13, the reference value is 000, the upper limit value is 7FF, and the lower limit value is 800) is a hysteresis value with respect to the distance. As long as the direction does not change, the moving direction can be accurately grasped, and when the moving direction is suddenly reversed, the deviation amount corresponds to the speed, so that the followability of the direction reversal is improved.
[0048]
When a binarized directional signal is generated by accumulatively adding and subtracting an incremental value, it can be configured by hard logic as shown in FIG. 12, but it is not possible to perform software processing using a digital signal processor (DSP). Are suitable.
[0049]
As described above, the present invention is applied to an origin detection device that detects a rising edge or a falling edge of a fixed point signal as an origin position in a scale device including an incremental encoder that outputs a periodic signal for incremental measurement and a fixed point signal for origin detection. According to the present invention, for example, as shown in FIG. 14, an origin signal having a configuration in which an origin signal periodically generated from an incremental measurement periodic signal is gated based on a fixed point signal to be an origin signal is provided. It can also be applied to the detection device 30.
[0050]
The origin detecting device 30 receives two phases of periodic signals A and B for incremental measurement output from an incremental encoder of an optical scale device on which a scale for an incremental signal and a scale for a fixed point signal are recorded. An interpolation circuit 31, a comparator 32 to which a directional signal obtained by the interpolation circuit 31 is supplied, a gate circuit 33 for outputting an origin signal, and an origin mask signal generation circuit 34, an origin detection direction setting signal, an origin gate signal , The match signal obtained by the interpolation circuit 31, the directional signal output from the comparator 32, and the origin mask signal obtained by the origin mask signal generation circuit 34. The origin mask signal generation circuit 34 is supplied with an origin mask release signal.
[0051]
In the origin detection device 30, the two-phase incremental measurement periodic signals A and B supplied to the interpolation circuit 31 are relative to a measurement object generated by an incremental encoder based on a scale for the incremental signal. For example, it is a phase modulation signal corresponding to the displacement amount.
[0052]
The origin gate signal supplied to the gate circuit 33 is obtained by binarizing a fixed point signal indicating a fixed point position generated based on a fixed point signal scale by an incremental encoder.
[0053]
The origin detection direction setting signal and the origin mask release signal are supplied to the gate circuit 33 from a controller (not shown).
[0054]
The interpolation circuit 31 outputs an incremental value obtained by interpolating the cycle of the incremental signal from the two-phase incremental measurement periodic signals A and B, as shown in FIG. Further, based on the two-phase incremental measurement periodic signals A and B, a directional signal indicating a relative movement direction of the incremental encoder with respect to the measurement object is generated and supplied to the comparator 32. Further, a coincidence signal corresponding to the timing at which the signal levels of the two-phase incremental measurement periodic signals A and B coincide with each other is obtained from the incremental value, and the coincidence signal is used as the origin signal as a gate circuit 33. To supply.
[0055]
The comparator 32 compares the signal level of the directional signal generated by the interpolation circuit 31 with a predetermined comparison value, thereby discriminating the relative movement direction of the incremental encoder with respect to the measurement object, and The converted directional signal is supplied to the gate circuit 33.
[0056]
Here, the binarized directional signal indicates a forward direction by a logic H and a reverse direction by a logic L with respect to the relative movement direction of the incremental encoder with respect to the measurement object.
[0057]
The gate circuit 33 outputs the origin signal obtained at the two positions by taking the logical product of the origin signal supplied from the interpolation circuit 31, that is, the coincidence signal, the origin gate signal and the origin mask signal. It is configured to be selected according to the sex signal and output as the origin signal. As shown in FIG. 15, this gate circuit outputs the origin signal only in the moving direction in which the origin gate signal is active and coincides with the origin detection setting signal.
[0058]
The origin mask signal generation circuit 34 includes an SR flip-flop circuit 34A that is set at the falling edge of the origin signal output from the gate circuit 33 and reset at the rising edge of the origin mask release signal.
[0059]
In the origin detection device 30 having such a configuration, the operation thereof is shown in the timing charts of FIGS. 16 to 19, and the direction signal matches the logic "L" and the origin detection direction setting signal matches the logic "H". When there is no such signal (see FIG. 19) and when the direction signal does not match the logic "H" and the origin detection direction setting signal does not match the logic "L" (see FIG. 17), the origin signal is not obtained and the direction signal is not obtained. And the origin detection direction setting signal are both coincident with logic "H" (see FIG. 16), and the directional signal and origin detection direction setting signal are both coincident with logic "L" (see FIG. 18). ), An origin signal indicating a specific origin position can be output regardless of the relative movement direction of the incremental encoder with respect to the measurement object.
[0060]
Here, in the origin detecting device 30 configured to gate the origin signal periodically generated from the incremental measurement periodic signal as described above to generate the origin signal based on the fixed point signal, the origin detection device 30 shown in FIG. By providing an integrator 35 that integrates the directional signal supplied from the interpolation circuit 31 to the comparator 32 as in the origin detecting device 20, the directional discrimination can be erroneously performed due to a sudden change in the directional signal due to jitter. And the origin can be reliably detected.
[0061]
As the integrator 35, one having the configuration shown in FIGS. 8 to 13 can be used.
[0062]
【The invention's effect】
As described above, in the origin detection device according to the present invention, by discriminating the relative movement direction of the incremental encoder based on the incremental measurement periodicity signal, regardless of the relative movement direction of the incremental encoder, the specific origin position can be determined. Can be detected. Further, by digitizing the integrator, the circuit configuration can be reduced in size and the influence of aging caused by analog elements can be suppressed. Further, in the integrator using the phase accumulator, the difference data of the position is integrated as it is, so that the error due to the time delay can be reduced.
[Brief description of the drawings]
FIG. 1 shows a configuration example of an origin detection device that detects a rising edge or a falling edge of a fixed point signal as an origin position in a scale device including an incremental encoder that outputs a periodic signal for incremental measurement and a fixed point signal for origin detection. It is a block diagram.
FIG. 2 is a diagram for explaining an interpolation method of an incremental signal;
FIG. 3 is a diagram for explaining a method of interpolating three-phase signals having phases different from each other by 120 °;
FIG. 4 is a timing chart showing the operation of the origin detection device.
FIG. 5 is a timing chart showing an operation in a case where the interpolation circuit of the origin detecting device detects the polarity of a change in the amount of change of an incremental value per unit time to generate a directional signal.
FIG. 6 is a diagram showing an integration result of a directional signal in which a duty ratio changes.
FIG. 7 is a block diagram showing another configuration example of the origin detection device according to the present invention.
FIG. 8 is a circuit diagram showing a configuration example of an integrator provided in the origin detecting device.
FIG. 9 is a circuit diagram showing another configuration example of the integrator.
FIG. 10 is a block diagram showing a configuration example when the integrator is realized by a digital circuit.
FIG. 11 is a timing chart showing the operation of the integrator constituted by the digital circuit.
FIG. 12 is a block diagram illustrating a configuration example of an integrator configured by hard logic to generate a binarized directional signal by cumulatively adding and subtracting an incremental value obtained by an interpolation circuit.
FIG. 13 is a timing chart showing the operation of the integrator constituted by the above-described hard logic.
FIG. 14 is a block diagram illustrating a configuration example of an origin detection device that gates an origin signal periodically generated from an incremental measurement periodic signal based on a fixed point signal and uses the gate as an origin signal.
FIG. 15 is a timing chart showing the operation of the origin detecting device.
FIG. 16 is a timing chart showing the operation of the origin detection device when both the directionality signal and the origin detection direction setting signal coincide with each other with a logic “H”.
FIG. 17 is a timing chart showing the operation of the reference point detection device when the direction signal is logic “L” and the reference point detection direction setting signal is not “H”.
FIG. 18 is a timing chart showing the operation of the origin detection device when both the directionality signal and the origin detection direction setting signal coincide with each other with a logic “L”.
FIG. 19 is a timing chart showing the operation of the origin detection apparatus when the direction signal does not match the logic "H" and the origin detection direction setting signal has the logic "L".
FIG. 20 is a timing chart showing the operation of a conventional incremental encoder in which the wavelength (period) of the periodic signal for incremental measurement is about 20 μm.
FIG. 21 is a timing chart showing the operation of an incremental encoder in which the wavelength (period) of the periodic signal for incremental measurement is set to 4 μm or less.
[Explanation of symbols]
10, 20, 30 Origin detection device, 11, 31 interpolation circuit, 11A, 11B A / D converter, 11C look-up table, 12, 32 comparator, 13 rising differentiator, 14 falling differentiator, 15, 33 Gate circuit, 21, 21A to 21D, 35 Integrator, C capacitor, R resistor, OP operational amplifier, 22 up / down counter, 23 control circuit, 24 adder / subtractor, 25 limiter circuit, 26 latch circuit, 34 origin mask signal generation Circuit, 34A SR flip-flop circuit

Claims (7)

An origin detection device for a scale device including an incremental encoder that outputs a periodic signal for incremental measurement and a fixed-point signal for origin detection,
Directional signal generating means for generating a directional signal indicating the relative movement direction of the incremental encoder based on the incremental measurement periodic signal output from the incremental encoder,
Discriminating means for discriminating a relative movement direction of the incremental encoder based on the directional signal generated by the directional signal generating means,
An origin detection device, comprising: origin signal generation means for generating an origin signal based on the fixed point signal output from the incremental encoder and the result of discrimination of the relative movement direction of the incremental encoder by the discrimination means. The origin signal generating means selects a rising edge and a falling edge of the fixed point signal as an origin signal based on a result of discrimination of the relative movement direction of the incremental encoder by the fixed point signal and the discriminating means. The origin detecting device according to claim 1, wherein The origin signal generating means gates the origin signal periodically generated from the incremental measurement periodicity signal based on the fixed point signal, the discrimination result of the incremental encoder relative movement direction by the discriminating means, and the fixed point signal. 2. The origin detecting device according to claim 1, wherein the origin detecting signal is used as an origin signal. The directional signal generation means is configured to change per unit time the amount of change in the absolute value of the interpolated incremental signal generated based on the incremental measurement periodic signal output from the incremental encoder in one cycle. 2. The origin detecting device according to claim 1, wherein a polarity signal is detected as a direction signal. The origin detecting device according to claim 1, further comprising an integrating unit that integrates a directional signal supplied from the directional signal generating unit to the origin signal generating unit. 6. The origin detection according to claim 5, wherein said integration means comprises an up / down counter whose count operation is controlled by a count control signal obtained by binarizing the direction signal generated by said direction signal generation means. apparatus. 6. The origin detecting apparatus according to claim 5, wherein said integrating means comprises a phase accumulator whose count operation is controlled by a count control signal obtained by binarizing the direction signal generated by said direction signal generating means. .

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