JP2005051856A - Linear encoder device, linear motor, and single-axis robot - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly detect an origin position and a pole reference position of a motor with a simple structure, and to suitably realize a position control and a drive control of the motor in a linear encoder device used for a linear motor, etc. <P>SOLUTION: The linear encoder device includes a linear scale 11 disposed linearly at a fixing unit to record magnetically or optically readable position information, and a detecting head 12 provided at a movable unit moving by the drive of the linear motor to read the linear scale 11. The linear encoder device further includes first reference point information 13a, 13b for indicating the origin position recorded at two positions of predetermined distance from both ends of the linear scale 11, and second reference point information 14a, 14b recorded at two positions corresponding to specific poles of the motor near both ends of the linear scale 11 to show the reference pole position. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a linear encoder device including a linear scale and a detection head for reading the linear scale, a linear motor including the linear encoder device, and a single-axis robot using the linear motor.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a linear motor or the like in which a position is detected by a linear encoder device for movement control and motor drive control is known.
[0003]
In such a linear encoder, an origin is set at a specific position on the linear scale, and the origin position is detected, whereby calibration for position control is performed.
[0004]
When a linear encoder device is installed in a single-axis robot or the like using a linear motor, the origin position is usually set at a certain distance from each end of the linear scale in order to improve controllability. In this case, since the origin position and the reference position of the magnetic pole of the motor do not necessarily coincide with each other, the motor drive such as controlling the energization to the coil to adjust the phase of the current supplied to the motor coil in accordance with the magnetic pole position. There is insufficient data on the reference position of the magnetic pole necessary for control of the magnetic field.
[0005]
As countermeasures against this, in addition to a linear scale and a detection head that give normal position information, a scale and a detection head for detecting the magnetic pole position are further provided (for example, see Patent Document 1), or the origin position and the magnetic pole A method is conceived in which a deviation from a reference position is checked in advance and stored in a controller for robot control.
[0006]
[Patent Document 1]
JP-A-8-159810 [0007]
[Problems to be solved by the invention]
Among the methods conventionally considered as described above, in the case of the former, since it is necessary to additionally attach a scale and a detection head for detecting the magnetic pole position to the linear encoder, the apparatus becomes complicated, large, and Incurs cost increase. Also, in the latter case, it is necessary to check the deviation between the origin position and the magnetic pole reference position for each robot individually, and store the data in the controller for the robot. There are inconveniences such as the need to rewrite data.
[0008]
As another method, it is conceivable to set the origin position according to the reference position of the magnetic pole of the motor, but depending on the stroke of the robot, the stop position is the same as the magnetic pole pitch on one end side and the other end side of the movable range. Inconveniences such as the need to reset the stroke when the deviation or the magnetic pole pitch is large occur.
[0009]
The present invention has been made to solve such a problem. In the present invention, the origin position is set at a certain distance from both ends of the linear scale. It is an object of the present invention to provide a linear encoder device, a linear motor, and a single-axis robot capable of reliably detecting a position and appropriately performing position control and motor drive control.
[0010]
[Means for Solving the Problems]
The linear encoder device of the present invention is provided on a linear scale that is linearly arranged on a fixed portion and that records position information that can be read magnetically or optically, and a movable portion that moves by driving a motor. And a first reference point information for indicating an origin position at two predetermined distances from both ends of the linear scale, and the linear scale. The second reference point information for indicating the reference magnetic pole position is recorded at two locations near the both ends of the scale and corresponding to the specific magnetic pole of the motor.
[0011]
According to the present invention, the origin position is detected when the detection head passes through the location where the first reference point information is recorded on the linear scale, and when the detection head passes through the location where the second reference point information is recorded. The reference magnetic pole position is detected. In this way, both the origin position and the reference magnetic pole position are examined with a simple structure consisting of a set of linear scale and detection head, and based on this, the control of the moving position of the movable part and the control of the motor drive are properly performed. Done.
[0012]
In the encoder device according to the present invention, in the vicinity of both ends of the linear scale, the recording location of the second reference point information is positioned closer to the end of the scale than the recording location of the first reference point information. It is preferable that the positional relationship of the reference point information recording locations is set.
[0013]
In this way, each reference point information is read by the movement of the detection head and each position is detected, and among the detected reference point information positions, the one near the end of the linear scale is the reference magnetic pole position. It is determined that the position farther from the end of the linear scale is the origin position.
[0014]
The linear motor of the present invention has a linear motor body having a linear stator with magnetic poles arranged at a constant pitch, and a mover facing the stator, and is movable with respect to the linear motor body. The linear motor body is provided with a linear scale that is arranged in parallel with the stator and records position information that can be read magnetically or optically. In a linear motor provided with a detection head facing the rear scale and controlled to energize the coils constituting the stator or mover by a control means for receiving a signal from the detection head, First reference point information for indicating the origin position is recorded at two predetermined distances from both ends of the linear scale, and the linear scale is displayed. The second reference point information for indicating the reference magnetic pole position is recorded in two locations corresponding to the specific magnetic pole of the motor in the vicinity of both ends of the first and second reference points by the detection head. According to the reading of point information, the control means determines the origin position and the reference magnetic pole position.
[0015]
This linear motor incorporates a linear encoder composed of a linear scale on which the first reference point information and the second reference point information are recorded and the detection head, so that an origin position and a reference magnetic pole position are obtained. Both are checked, and based on this, the control of the moving position of the movable part and the control of the drive of the linear motor are appropriately performed.
[0016]
In the present invention, in the vicinity of both ends of the linear scale, the reference positions of the second reference point information are positioned closer to the end of the linear scale than the recording positions of the first reference point information. The positional relationship of the point information recording location is set, and the control means determines the reference magnetic pole position based on the reference point information first read when the detection head moves from the linear scale end to the linear scale center side, The origin position is preferably determined based on the read reference point information.
[0017]
The single-axis robot according to the present invention includes the linear motor, and the movable member is provided with a work member support table on which the work member is detachably attached.
[0018]
In this way, the linear motor equipped with the linear encoder of the present invention is effectively applied to a single-axis robot.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0020]
1 and 2 show a single-axis robot as an example of application of a linear motor provided with the linear encoder device of the present invention. In these drawings, a single-axis robot R is configured using a linear motor, and has a robot body (linear motor body) 1 having a stator and a mover facing the stator, And a movable portion 2 that can move linearly in a certain direction.
[0021]
The robot body 1 includes a base portion 3 and a pair of cover members 4 constituting both side wall portions, and is formed in a horizontally long frame shape extending in a uniaxial direction.
[0022]
In the robot body 1, a guide rail 5 having a constant width is provided on the base portion 3, and a stator portion (stator) 6 is disposed above the guide rail 5. The stator portion 6 has a large number of annular permanent magnets (not shown) arranged in the axial direction so that the N and S magnetic poles are alternately positioned in opposite directions, and is formed in a shaft shape. Is supported by the robot body 1.
[0023]
The movable portion 2 has a hollow movable block 8 through which the stator portion 6 is inserted, and a guided portion 9 that engages with the guide rail 5 is provided at the lower end of the movable block 8. A movable block 8 is slidably supported on the guide rail 5.
[0024]
A coil (movable element) 7 constituting an armature is fixed to the inner periphery of the hollow portion of the movable block 8. The coil 7 surrounds the stator unit 6 in a state where the movable unit 2 is assembled to the robot body 1.
[0025]
A work member support table 10 is provided on the upper portion of the movable portion 2, and various work members according to the application are attached to the table 10. The table 10 is attached to the movable block 8 by bolting or the like.
[0026]
Further, the single-axis robot R is provided with a linear encoder. The linear encoder includes a linear scale 11 that records position information that can be read magnetically or optically, and a detection head 12 that reads the linear scale 11. In the present embodiment, the linear scale 11 is composed of a magnetic scale in which position information is magnetically recorded, and the detection head 12 is composed of an MR sensor capable of reading magnetic recording information.
[0027]
The linear scale 11 is provided on the upper surface of the base portion 3 on one side of the guide rail 5 over substantially the entire length of the base portion 3, while the detection head 12 is provided on the lower end of one side portion of the movable block 8. It arrange | positions so that the said linear scale 11 may be opposed.
[0028]
FIG. 3 schematically shows a part of the linear motor mechanism portion of the single-axis robot R, the linear encoder, and the control means. In this figure, the linear scale 11 records information (A phase and B phase in the output signal phase) 15 indicating the position at a fixed minute pitch, and reference point information (Z phase in the output signal phase) 13a and 13b. , 14a, 14b are provided at four convenient locations, two in the vicinity of both ends.
[0029]
Of these reference point information (Z-phase), each of the two sides is the first reference point information (first Z-phase) 13a and 13b for indicating the origin position, and the remaining one is the reference magnetic pole position. The second reference point information (second Z phase) 14a and 14b is shown. The first Z phases 13a and 13b for indicating the origin position are provided at predetermined distances A1 and B1 from the left and right ends of the linear scale 11, respectively. The distance A1 from the end on the left end side of the linear scale 11 to the first Z phase 13a and the distance B1 from the end on the right end side of the linear scale 11 to the first Z phase 13a are substantially the same, for example, about 70 mm. Is set.
[0030]
The second Z phases 14a and 14b for indicating the reference magnetic pole position are provided at positions corresponding to the specific magnetic poles of the stator portion 6 in the linear motor. In this case, since the distance from the end of the linear scale 11 to the position corresponding to the specific magnetic pole is not always the same, the distances A2 and B2 from the end of the linear scale 11 to the second Z-phases 14a and 14b are The first Z phases 13a, 13b and the first Z phases 13a, 13b are positioned so that the second Z phases 14a, 14b are positioned on the linear scale end side with respect to the first Z phases 13a, 13b. The positional relationship with the two Z phases 14a and 14b is set.
[0031]
By forming the linear scale 11 in this way, as the detection head 12 moves on the linear scale 11, A-phase and B-phase signals are output, and at four locations near both ends of the linear scale 11, Z is output. A phase signal is output. The output signal of the detection head 12 is input to a controller (control means) C. The controller C controls the supply current to the coil 7 of the single-axis robot R, thereby controlling the linear motor drive and moving it. The movement of the unit 2 is controlled.
[0032]
The controller C determines the origin position and the reference magnetic pole position based on the Z-phase signal given from the detection head 12. In this case, the first Z-phase 13a, 13b and the second Z-phase 14a, 14b cannot be distinguished because the output signal of the detection head 12 is the same Z-phase signal. However, the positional relationship as described above is set. The origin position and the reference magnetic pole position can be determined in consideration of the above. That is, when the detection head 12 moves from the end of the linear scale to the center side of the linear scale, the reference magnetic pole position is determined based on the Z-phase signal read first, and then the origin position is determined based on the read Z-phase signal. Is done.
[0033]
A specific example of control for discriminating the origin position and the reference magnetic pole position will be described with reference to the flowchart of FIG.
[0034]
When the processing of this flowchart is started, the linear motor is first driven so that the movable part 2 moves to one end side, the end of the movable range is checked, and the direction of movement of the movable part 2 is detected when the end is detected. Is inverted (steps S1 to S3). Thus, after the movable part 2 is moved from one end of the movable range toward the center side, the Z-phase detection process is performed (step S4), and if the Z-phase is detected, whether or not it is the first time, That is, it is determined whether or not the Z-phase is detected for the first time after the movement from one end of the movable range is started (step S5). If it is the first time, it is determined that it is the reference magnetic pole position, and the magnetic pole position data is cleared (step S6). Further, by returning to step S4, the next Z phase is detected while the movable portion 2 is continuously moved.
[0035]
When the determination in step S5 is NO, that is, when the detection of the Z phase is the second time, it is determined that the position is the origin position, and the position is cleared (step S7).
[0036]
According to the present embodiment as described above, the origin position and the magnetic pole reference position are obtained by performing processing as shown in the flowchart of FIG. 4 at an appropriate time such as when the single axis robot R starts work or at predetermined intervals. Is examined and calibrated.
[0037]
In this case, the Z phases 13a, 13b, 14a, and 14b are set at two positions corresponding to the origin position and the magnetic pole reference position on both the left and right sides, and the magnetic pole reference position is set to the end of the linear scale with respect to the origin position. Thus, since the positional relationship between the two is determined in advance, the origin position and the magnetic pole reference position can be distinguished and detected based on the detection of the Z phase and the positional relationship.
[0038]
As described above, the origin position and the magnetic pole reference position can be examined by one set of the linear scale 11 and the detection head 12, so that compared with the case where the origin position and the magnetic pole reference position are detected by separate detection means as in the prior art. The structure of the linear encoder device can be simplified and the cost can be reduced.
[0039]
Further, it is not necessary to previously store the deviation between the origin position and the magnetic pole reference position in the controller C, and the compatibility of the controller C is not impaired.
[0040]
After the origin position and the magnetic pole reference position are checked, the position is detected by counting the A and B phase signals output from the detection head 12 as the position moves from the limited position. While controlling the movement position, the magnetic pole position of the stator portion 6 is checked based on the movement amount from the magnetic pole reference position, and the phase of the current supplied to the coil 7 is controlled according to the magnetic pole position. Control is performed properly.
[0041]
In addition, the specific structure of this invention is not limited to the said embodiment, As described below, various changes are possible.
[0042]
In the above embodiment, the magnetic scale 11 and the detection head 12 constitute a linear encoder. However, the linear encoder may be optical, for example, a linear scale is formed by a tape having a large number of slits, and an optical device. Alternatively, the detection head may be formed by a sensor that detects the slit.
[0043]
In the linear motor used in the single-axis robot R of the above embodiment, the stator is constituted by a permanent magnet and the mover is constituted by a coil. Conversely, the stator is constituted by a coil and the mover is constituted by a permanent magnet. A linear motor may be used.
[0044]
In addition to the single-axis robot R, the linear encoder of the present invention can be installed in a linear motor used for various applications. Furthermore, the present invention is not limited to a linear motor, and can be applied to a driving device that moves a movable part linearly via a ball screw or the like using a rotary motor. A linear scale is provided, a detection head is provided on the movable part, and a position on the linear scale corresponding to the reference magnetic pole position of the motor is checked in advance, and information indicating the position and information indicating the origin position are converted into the linear scale. Just record it.
[0045]
【The invention's effect】
As described above, in the present invention, the first reference point information for indicating the origin position is recorded at two predetermined distances from both ends of the linear scale, and in the vicinity of both ends of the linear scale. Since the second reference point information for indicating the reference magnetic pole position is recorded at two locations corresponding to the specific magnetic pole of the motor, the control of the moving position of the movable part and the control of the motor drive are based on the second reference point information. Can be performed properly. In addition, both the origin position and the reference magnetic pole position can be detected by a pair of linear scales and a detection head, and the origin position and the magnetic pole reference position are detected by separate detection means as in the prior art. In comparison, the structure of the linear encoder device can be simplified and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal plan view showing an example of a single-axis robot to which the present invention is applied.
FIG. 2 is a cross-sectional view taken along the line II-II in FIG.
FIG. 3 is a diagram schematically showing a part of a linear motor mechanism, a linear encoder, and control means.
FIG. 4 is a flowchart showing processing for examining an origin position and a reference magnetic pole position.
[Explanation of symbols]
R Single-axis robot 1 Robot body 2 Movable part 6 Stator part 7 Coil 11 Linear scale 12 Detection heads 13a, 13b, 14a, 14b Z-phase (reference point information)
C controller

Claims (5)

A linear scale that is linearly arranged on the fixed part and records position information that can be read magnetically or optically, and a detection head that is provided on a movable part that moves by driving a motor and reads the linear scale. A linear encoder device comprising:
First reference point information for indicating the origin position is recorded at two predetermined distances from both ends of the linear scale.
A linear encoder apparatus, wherein second reference point information for indicating a reference magnetic pole position is recorded at two locations corresponding to a specific magnetic pole of a motor, in the vicinity of both ends of the linear scale. In the vicinity of both ends of the linear scale, each of the reference point information recording locations is such that the recording location of the second reference point information is located closer to the end of the scale than the recording location of the first reference point information. 2. The linear encoder device according to claim 1, wherein a positional relationship is set. A linear motor main body having a linear stator in which magnetic poles are arranged at a constant pitch, and a movable portion having a movable element facing the stator and being movable with respect to the linear motor main body,
The linear motor body is provided with a linear scale that is arranged in parallel with the stator and records position information that can be read magnetically or optically. On the other hand, the movable head has a detection head that faces the rear scale. Is provided,
In the linear motor in which the energization to the coils constituting the stator or the mover is controlled by the control means that receives the signal from the detection head,
First reference point information for indicating the origin position is recorded at two predetermined distances from both ends of the linear scale.
Second reference point information for indicating the reference magnetic pole position is recorded in two locations corresponding to the specific magnetic pole of the motor in the vicinity of both ends of the linear scale,
A linear motor characterized in that the origin position and the reference magnetic pole position are discriminated by the control means in accordance with the reading of the first and second reference point information by the detection head. These reference point information recording locations so that the recording location of the second reference point information is located closer to the end of the linear scale than the recording location of the first reference point information in the vicinity of both ends of the linear scale. Is set,
The control means determines the reference magnetic pole position based on the reference point information read first when the detection head moves from the end of the linear scale toward the center of the linear scale, and then determines the origin based on the read reference point information. 4. The linear motor according to claim 3, wherein the position is discriminated. A single-axis robot comprising the linear motor according to claim 3, wherein a work member support table to which the work member is detachably attached is provided on the movable portion.

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