JP2008082785A - Variable resolution position detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position detector capable of performing precise position detection with simple system constitution using a linear scale in which a narrow scale pitch region for high-resolution position detection and a coarse scale pitch region for medium/low-resolution position detection are mixed. <P>SOLUTION: The detector includes the region in which N poles and S poles are alternately magnetized at a narrow scale pitch for high-resolution position detection and the region in which N poles and S poles are alternately magnetized at a coarse scale pitch that is integral multiple of the scale pitch for medium/low-resolution position detection. The detector includes a magnetic head having an A-phase magnetic detection element and a plurality of B-phase magnetic detection elements arranged at a quarter of the interval of the narrow scale pitch for detecting the variation of magnetic field of the linear scale and a means for selecting and switching one B-phase magnetic detection element from among the plurality of B-phase magnetic detection elements having the quarter of the pitch interval with the A-phase magnetic detection element from an output pattern of the plurality of B-phase magnetic detection elements. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a position detection device that detects the position of a moving body that moves along a rail, and more specifically, by detecting a magnetic field of a linear scale in which N and S poles are alternately magnetized. The present invention relates to a position detection device that detects a position.

Conventionally, when the position of a moving body is detected using a linear scale, only a part of the moving body moving section needs to be detected with a high resolution position, and the low resolution position detection may be used for other parts. A linear scale in which N poles and S poles are alternately magnetized in accordance with a narrow scale pitch necessary for high-resolution position detection over the entire moving section has been installed (for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-127078

  However, in sections where low-resolution position detection is sufficient, high-speed movement is generally performed, but the entire moving section is magnetized with a narrow scale pitch necessary for high-resolution position detection. The output change frequency of the detection element becomes high, and the converter converts the two-phase pulses in the positive direction (traveling direction) and the negative direction (backward direction) according to the movement of the magnetic head in the moving body moving direction. The response could not catch up, and accurate position detection corresponding to the movement of the magnetic head could not be performed. In addition, when a narrow scale pitch necessary for high-resolution position detection is used over the entire moving section, the number of pulses output in response to movement increases, so the number of bits in the counter that accumulates the number increases, resulting in cost savings. Was the cause of high.

  On the other hand, if the entire section is set to a coarse scale pitch in accordance with the high-speed movement of the moving body, there is a problem that the required stop accuracy cannot be obtained in a place where high stop accuracy is required.

  In addition, when using a linear scale composed of an area magnetized with a narrow scale pitch for high-resolution position detection and an area magnetized with a coarse scale pitch for low-resolution position detection, high-resolution position detection is used. With only a magnetic head corresponding to a narrow scale pitch for use, there are cases where an output pulse cannot be obtained in a region magnetized with a coarse pitch for low-resolution position detection. For this reason, a separate magnetic head for detecting a low resolution position is separately provided, and a sensor and output switching processing means for specifying the switching timing corresponding to the scale pitch of the outputs of the two magnetic heads are required, and there are particularly many switching sections. In this case, the system was complicated and costly.

  Accordingly, an object of the present invention is to perform accurate position detection with a simple system configuration using a linear scale in which a narrow scale pitch area for high-resolution position detection and a coarse scale pitch area for medium-low resolution position detection are mixed. The present invention provides a position detecting device capable of performing the above.

  The present invention provides a high resolution position detection region in which N poles and S poles are alternately magnetized at a narrow scale pitch for high resolution position detection in the moving direction of the moving body, and the scale pitch for medium and low resolution position detection. A position detection device having a linear scale having a medium and low resolution position detection region in which N poles and S poles are alternately magnetized at a coarse scale pitch that is an integer multiple of the number, and detects a change in the magnetic field of the linear scale A magnetic head having an A-phase magnetic detection element and a plurality of B-phase magnetic detection elements arranged in a moving direction of the movable body at intervals of a quarter of the narrow scale pitch, and the plurality of B-phases A plurality of B-phase magnetic detection elements having a pitch interval of a quarter of that of the A-phase magnetic detection element with respect to the scale pitch in which the interval magnetized on the linear scale changes from the output pattern of the magnetic detection element Means for selectively switching one B-phase magnetic detection element from among the outputs from the two magnetic detection elements of the A-phase magnetic detection element and the selected B-phase magnetic detection element. It has a converter that converts it into a two-phase pulse consisting of a positive edge pulse and a negative edge pulse according to the movement of the magnetic head, and the position of the moving body is specified by counting the two-phase pulse with an integration counter. By doing so, the above object is achieved.

  In the present invention, the interval between the A-phase magnetic detection element and the B-phase magnetic detection element is a quarter of the scale pitch of the linear scale that is sequentially magnetized as N pole, S pole, N pole, S pole,. The reason for setting to 1 is that if the distance between the A-phase magnetic detection element and the B-phase magnetic detection element is not arranged at one-fourth of the scale pitch, the magnetic head, that is, the moving body is output in the traveling direction and the retreating direction. Since the position at which the pulse appears is shifted, it is necessary to select a B-phase magnetic detection element that has a quarter pitch interval. The present invention uses a magnetic head composed of an A-phase magnetic detection element and a plurality of B-phase magnetic detection elements arranged at a quarter interval of a narrow scale pitch (minimum scale pitch) of a linear scale. One B-phase magnetic detection element is selected from the output pattern of the B-phase magnetic detection element so as to be a quarter of the scale pitch.

  With the above configuration, the present invention has a high resolution position detection region in which N poles and S poles are alternately magnetized at a narrow scale pitch for high resolution position detection in the moving direction of the moving body, Even when a linear scale in which medium and low resolution position detection areas in which N poles and S poles are alternately magnetized with a coarse scale pitch that is an integral multiple of the scale pitch for resolution position detection is used, The A phase magnetic detection element and B phase magnetic detection element corresponding to one-fourth of the scale pitch can be selected as appropriate, so accurate position detection is possible with a simple system configuration regardless of the change in scale pitch. It becomes possible.

  Embodiments of the present invention will be described with reference to FIGS. 1 to 5 based on examples. FIG. 1 shows a B-phase magnetic sensing element that satisfies the relationship between the A-phase magnetic sensing element and the pitch interval of a quarter of the scale pitch in a high-resolution position detection region (here, the scale pitch P = λ = 10 mm). A time chart for explaining a method of selecting is shown together with the magnetic head 10 and the linear scale L1. FIG. 2 shows a B-phase magnetism that satisfies the relationship between the A-phase magnetic detection element and the pitch interval of a quarter of the scale pitch in the medium resolution position detection region (here, the scale pitch P = λ × 2 = 20 mm). The time chart for demonstrating the method to select a detection element is shown with the magnetic head 10 and the linear scale L2. FIG. 3 shows a B-phase magnetism that satisfies the relationship between the A-phase magnetic detection element and the pitch interval of a quarter of the scale pitch in the low-resolution position detection region (here, the scale pitch P = λ × 3 = 30 mm). A time chart for explaining a method of selecting a detection element is shown together with the magnetic head 10 and the linear scale L3. FIG. 4 shows the output from the output of the magnetic head 10 having A-phase magnetic detection elements and a plurality (eight in this embodiment) of B-phase magnetic detection elements arranged at a quarter interval of the scale pitch P1. The block diagram is shown until a phase output is obtained by selectively switching between the phase magnetic detection element and the B phase magnetic detection element having a quarter pitch interval. FIG. 5 is an explanatory diagram for converting the counter output into the position output.

First, in the high-resolution position detection region (scale pitch P = λ = 10 mm), a method for selecting a B-phase magnetic detection element that satisfies the relationship between the A-phase magnetic detection element and the pitch interval of a quarter of the scale pitch is shown in FIG. And it demonstrates based on FIG. The output of the A-phase magnetic detection element and the output of the B-phase magnetic detection elements (B1 to B8) output from the magnetic head 10 are input to the waveform shaping circuit 20 (see FIG. 4) and converted from sin waves to rectangular waves. The The converted waveform is shown as T1 in FIG. Here, the outputs of B5 to B8 are not shown because they are not involved in the detection of the scale pitch. From the obtained waveform, the following relational expression
F1: signA = signB2 = sign ^ B4
In other words, when the sign of the A phase magnetic detection element, the sign of the B2 phase magnetic detection element, and the sign of the inverted output of the B4 phase magnetic detection element are equal, the linear scale L1 is determined by the scale pitch determination circuit 30 in FIG. The B1 phase magnetic detection element is selected as a B phase magnetic element that is determined to have a pitch corresponding to the high resolution and the pitch interval between the A phase magnetic detection element and the pitch interval is ¼ of the scale pitch. (Refer to FIG. 4) is set to ON, and selection outputs of other elements are set to OFF. As a result, the analog-pulse conversion circuit 50 shown in FIG. 4 receives the analog output of the phase A magnetic detection element as the phase A input, and the switching circuit 40 outputs the output of the phase B1 magnetic detection element as the phase B input. The analog output is selected and input.

Next, in the medium resolution position detection region (scale pitch P = λ × 2 = 20 mm), a method of selecting the B-phase magnetic detection element that satisfies the relationship between the A-phase magnetic detection element and the pitch interval of a quarter of the scale pitch. Will be described with reference to FIGS. The output of the A-phase magnetic detection element and the output of the B-phase magnetic detection elements (B1 to B8) output from the magnetic head 10 are input to the waveform shaping circuit 20 (see FIG. 4) and converted from sin waves to rectangular waves. The The converted waveform is shown as T2 in FIG. From the obtained waveform, the following relational expression
F2: signA = signB4 = sign ^ B8
4, that is, when the sign of the A phase magnetic detection element, the sign of the B4 phase magnetic detection element, and the sign of the inverted output of the B8 phase magnetic detection element are equal, the linear scale L2 is determined by the scale pitch determination circuit 30 in FIG. The B2-phase magnetic detection element is selected as the B-phase magnetic detection element, which is determined to have a medium resolution corresponding pitch and the pitch interval between the A-phase magnetic detection element and the pitch interval is 1/4 of the scale pitch. The output (see FIG. 4) is turned on, and the selection outputs of other elements are turned off. As a result, the analog-pulse conversion circuit 50 shown in FIG. 4 receives the analog output of the phase A magnetic detection element as the phase A input, and the switching circuit 40 outputs the output of the phase B2 magnetic detection element as the phase B input. Selected and analog output is input.

Furthermore, in the low-resolution position detection region (scale pitch P = λ × 3 = 30 mm), a method of selecting a B-phase magnetic detection element that satisfies the relationship of a quarter pitch pitch with the A-phase magnetic detection element 3 and FIG. The output of the A-phase magnetic detection element and the output of the B-phase magnetic detection elements (B1 to B8) output from the magnetic head 10 are input to the waveform shaping circuit 20 (see FIG. 4) and converted from sin waves to rectangular waves. The The converted waveform is shown as T3 in FIG. From the obtained waveform, the following relational expression
F3: (signA = signB6) and (^ F1) and (^ F2)
Is satisfied, that is, when the sign of the phase A magnetic detection element is equal to the sign of the B6 magnetic detection element and the conditions of the above relational expressions F1 and F2 are not satisfied, the linear scale L3 determines the scale pitch in FIG. The circuit 30 selects a B3-phase magnetic detection element as a B-phase magnetic element that is determined to have a low-resolution corresponding pitch and satisfies a quarter pitch interval of the A-phase magnetic detection element and the pitch interval, and B3 The element selection output (see FIG. 4) is turned on, and the selection outputs of other elements are turned off. As a result, the analog-pulse conversion circuit 50 shown in FIG. 4 receives the analog output of the phase A magnetic detection element as the phase A input and the analog output of the phase B3 magnetic detection element as the phase B input.

  The scale pitch determination circuit 30 that determines the scale pitch described above can be configured by a general logic circuit using an AND circuit or a NOT circuit. In addition, since the switching circuit 40 can also be configured by general circuit elements such as transistors and analog switches, a specific circuit configuration and the like are omitted.

  The analog-to-pulse converter 50 converts an analog input consisting of two phases, that is, an output of the A-phase magnetic detection element and an output of the B-phase magnetic detection element, which is selected as described above, by a quarter of the phase, When added to the B-phase input, the analog input is processed, and a positive edge pulse is output when the magnetic head 10 moves in the positive direction (for example, the traveling direction) and moves in the negative direction (for example, the backward direction). A negative edge pulse is output. The calculation process will be described below.

  Analog signals (sin waves) input to the A-phase input and the B-phase input are converted into 0 or 1 rectangular waves. It is constant when the A-phase output rises from 0 to 1 when the B-phase inverted output (^ B) is 1 and when the A-phase output falls from 1 to 0 when the B-phase output is 1. A positive edge pulse of width is output. On the other hand, it is constant when the A phase output rises from 0 to 1 when the B phase output is 1, and when the A phase output falls from 1 to 0 when the B phase inverted output (^ B) is 1. A negative edge pulse with a width is output. Such an analog-pulse conversion circuit is well known and can be handled by a commercially available general-purpose product.

  Next, the positive direction edge pulse and the negative direction edge pulse output from the analog-pulse conversion circuit 50 are input to the integration counter 60, and the value obtained by subtracting the negative direction edge pulse number from the positive direction edge pulse number is output from the counter. The The position of the moving body is detected by associating this output with the arrangement patterns of different known scale pitches, that is, the arrangement of the high resolution section, the medium resolution section, and the low resolution section. How to make this correspondence will be described below with reference to FIG.

  Here, for the sake of explanation, the pitch of the high resolution section is 10 mm, the middle resolution section is 20 mm, and the low resolution section is 30 mm, as described above. Then, as the sections of the known scale pitch, the origins P1 to P2 (1000 mm in absolute position) are the high resolution sections, P2 to P3 (5000 mm in absolute position) are the medium resolution sections, and P3 to P4 (17000 mm in absolute position). Is a low resolution section, P4 to P5 (18000 mm in absolute position) is a high resolution section, and P5 to P6 (27000 mm in absolute position) is a low resolution section.

  Here, since 1 count in the high resolution section corresponds to 10 mm, at the position of P2, 1000 mm ÷ 10 mm and 100 is output as the count value. In the position of P3, in the absolute position, the interval between P3 and P2 is 4000 mm between 5000 mm and 1000 mm. However, since this section is an intermediate decomposition section, one count corresponds to 20 mm, and 4000 mm ÷ 20 mm. Thus, it is 200 counts, and is added to the count value 100 of P2, and 300 is output as the count value of P3.

  Furthermore, in the position of P4, in the absolute position, the interval between P4 and P3 is 12000 mm with 17000 mm-5000 mm. However, since this section is a low resolution section, 1 count corresponds to 30 mm, and 12000 mm ÷ 30 mm. 400, and added to the count value 300 of P3, 700 is output as the count value of P4.

  Similarly, in the position of P5, in the absolute position, the interval between P5 and P4 is 18000 mm-17000 mm and 1000 mm, but since this section is a high resolution section, one count corresponds to 10 mm, and 1000 mm ÷ 10 mm, 100 counts, and added to the count value 700 of P4, and 800 is output as the count value of P5.

  Furthermore, in the position of P6, in the absolute position, the interval between P6 and P5 is 27000 mm-18000 mm and 9000 mm, but since this section is a low resolution section, 1 count corresponds to 30 mm, and 9000 mm ÷ 30 mm 300 counts, 1100 is output as the count value of P6 by adding to the count value 800 of P5.

  Conversely, when the absolute position of the moving object is obtained from the counter output value, it can be obtained by performing the operation opposite to the above operation.

  A linear scale composed of a region magnetized with a narrow pitch for detecting high resolution positions and a region magnetized with a coarse pitch for detecting medium to low resolution positions is an integral unit. Alternatively, they may be a combination of those configured separately.

  In the above-described embodiment, eight B-phase magnetic detection elements are used so that the scale pitch can be up to 3 times. However, the number of magnetic detection elements and the switching circuit can be set with the same idea as the embodiment. By increasing the number, it is possible to cope with a scale pitch exceeding 3 times.

  The present invention is capable of accurate position detection even when the magnetization pitch of the linear scale is variable to high resolution, medium resolution, and low resolution, and can control the linear motor and the like easily. The availability is very high.

Explanatory drawing of the selection method of the B phase magnetic detection element in a high-resolution position detection area | region. Explanatory drawing of the selection method of the B-phase magnetic detection element in a medium-resolution position detection area. Explanatory drawing of the selection method of the B-phase magnetic detection element in a low-resolution position detection area. The block diagram from the output of a magnetic head to obtaining a counter output. Explanatory drawing for converting a counter output into a position output.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Magnetic head 20 ... Waveform shaping circuit 30 ... Scale pitch discrimination circuit 40 ... Switching circuit 50 ... Analog pulse conversion circuit 60 ... Integration counter

Claims (1)

A high resolution position detection area in which N poles and S poles are alternately magnetized at a narrow scale pitch for high resolution position detection in the moving direction of the moving body, and an integer multiple of the scale pitch for medium to low resolution position detection A variable resolution position detection device having a linear scale having a medium and low resolution position detection region in which N poles and S poles are alternately magnetized at a coarse scale pitch,
A magnetic head having an A-phase magnetic detection element and a plurality of B-phase magnetic detection elements arranged in the moving direction of the movable body at intervals of a quarter of the narrow scale pitch for detecting a change in the magnetic field of the linear scale. Have
From the output patterns of the plurality of B-phase magnetic detection elements, a plurality of the pitch intervals that are a quarter of the pitch of the A-phase magnetic detection elements with respect to the scale pitch at which the interval magnetized on the linear scale changes. Means for selectively switching one B-phase magnetic detection element from among the B-phase magnetic detection elements;
2 consisting of a positive edge pulse and a negative edge pulse corresponding to the movement of the magnetic head with respect to the linear scale from the outputs of the two magnetic detection elements of the A phase magnetic detection element and the selected B phase magnetic detection element. A variable-resolution position detecting device having a converter for converting into a phase pulse and specifying the position of the moving body by counting the two-phase pulse with an integration counter.

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