JP2014169992A - Method and device for detecting front end position of tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow detection of a front end position of a tool in one position detector to achieve space-saving and reduction in cost of an automatic assembling system including position detectors.SOLUTION: In a position detection method, a reference member rotationally movable around a rotation axis is rotationally moved from a prescribed rotation start point to obtain a rotation radius R at the time of crossing an optical axis of a light blocking sensor at two intersections, and rotation angles θ1 and θ2 to the two intersections on the optical axis. A tool rotationally movable around the rotation axis is rotationally moved from the same rotation start point around the rotation axis and is caused to cross the optical axis of the light blocking sensor at two intersections to measure rotation angles θ1' and θ2' to the two intersections on the optical axis, and an amount of displacement between a reference point 12 being a front end of the reference member and a detection point 13 being a front end of the tool is calculated on the basis of the rotation angles θ1' and θ2', the radius R, and the rotation angles θ1 and θ2.

Description

  The present invention relates to a method and an apparatus for detecting the tip position of a tool for machining, and more particularly to a method and an apparatus for detecting the tip position of a tool used in an automatic machining system that automatically performs machining such as assembly or painting.

  In general, industrial robots equipped with tools, which are various tools, are used in automatic processing systems that automatically assemble and the like, and the tip of the tool is used for position adjustment to improve the processing accuracy of the tool. Position detection is performed. Examples of the tool for detecting the tip position include those having a rod-like or pin-like form such as a coating nozzle, a drill, and a screw driver.

  By the way, in a tool of an automatic machining system using a robot, the tip position of the tool may be shifted due to reasons such as mounting errors when replacing parts and tool dimensional tolerances. Further, when these tools are used for assembling precision parts or the like that require positioning accuracy in units of micrometers, high-precision positioning is required. In order to prevent the processing accuracy from being lowered due to the displacement, the tip position of the tool is detected, the displacement amount is obtained, and the teaching position to the robot is corrected.

  Conventionally, as a method for detecting the planar position of a tool, a tool that can move in the X and Y directions on planes orthogonal to each other is used. There is known a method of detecting by crossing (see Patent Document 1). The position of the tool is detected by reading a signal from a position detection device such as an encoder provided in the drive motor, corresponding to the intersection between the tool and the optical axis of the light shielding sensor. Then, it is possible to calculate a difference in position with a reference object that has been subjected to the same operation in advance, and to correct the teaching position of the actuator that moves the tool, using the calculated difference as a positional deviation amount.

JP 2000-354816 A

  However, in the case of the configuration of the prior art, two or more movement axes of the light shielding sensor and the tool are required, and at the same time, two pairs of light shielding sensors are necessary to detect the position of the tool in the X and Y directions. For this reason, there is a problem that the cost is increased and installation space is taken up.

  The present invention has been made in view of the above-described conventional problems, and reduces the movement axis of the light-shielding sensor and the tool and makes it possible to detect the tip position of the tool with a pair of light-shielding sensors. The object is to reduce the cost and space required.

In order to solve the above problems, a first aspect of the present invention is a method for detecting the tip position of a movable tool,
A light-shielding sensor that senses light-shielding of the optical axis between the light exiting part and the light entering part is provided, and the tool can be rotated about the rotational axis, provided with a reference member that can be rotationally moved about the same rotational axis as described above. When the member and the tool are rotated around the rotation axis, the optical axis is provided at a position where it intersects at two locations,
Each rotation angle θ1 from a rotation radius R when the reference member is rotated about the rotation axis from a predetermined rotation start point to two intersections between the rotation start point and the optical axis of the light-shielding sensor. And θ2 are known,
The tool is rotated around the rotation axis from the same rotation start point as described above, intersects the optical axis of the light-shielding sensor at two locations, and 2 from the rotation start point to the optical axis of the light-shielding sensor. Measure the rotation angles θ1 ′ and θ2 ′ up to the intersection of the points, and based on the rotation angles θ1 ′ and θ2 ′, the rotation radius R, and the rotation angles θ1 and θ2, a reference that is the tip of the reference member The present invention provides a tool tip position detection method characterized by including a step of calculating a positional deviation amount between a point and a detection point which is the tip of the tool.

The second aspect of the present invention is a tip position detecting device for a movable tool,
A light-shielding sensor for sensing the light-shielding of the optical axis between the light-emitting part and the light-incident part, provided with a reference member that is capable of rotational movement about the rotational axis and a rotational member that can be rotated about the same rotational axis as described above Is provided at a position that intersects the optical axis at two locations when the reference member and the tool are rotated around the rotation axis, respectively,
Each rotation angle θ1 from a rotation radius R when the reference member is rotated about the rotation axis from a predetermined rotation start point to two intersections between the rotation start point and the optical axis of the light-shielding sensor. And θ2 stored therein, and
The tool is rotated around the rotation axis from the same rotation start point as described above, and intersects the optical axis of the light shielding sensor at two locations, so that the optical axis of the light shielding sensor is The rotation angles θ1 ′ and θ2 ′ up to the two intersections can be measured, and from the rotation angles θ1 ′ and θ2 ′, the rotation radius R, and the rotation angles θ1 and θ2, It is an object of the present invention to provide a tool tip position detecting device capable of calculating a positional deviation amount between a reference point which is a tip and a detection point which is the tip of the tool.

  In the position detection method of the present invention, the detection point, which is the tip of the tool, is rotated about the same rotation axis as the rotation axis of the reference member, and is shielded from light at two different locations on the optical axis of the pair of light shielding sensors. Then, the rotation angles θ1 ′ and θ2 ′ when the light is shielded are detected, and the positions of the detection point and the reference point are determined based on the rotation angles θ1 and θ2 and the radius R of the reference point that is the tip of the reference member that is known in advance. The amount of deviation can be calculated. Therefore, in the present invention, it is possible to detect the position with only one rotating shaft, and it is possible to accurately obtain position information in the X direction and the Y direction with only a pair of light shielding sensors. As a result, position detection can be performed at low cost and in a narrow space.

It is a general view of an automatic processing system provided with the position detection device of the present invention. It is explanatory drawing at the time of detecting the front-end | tip position of the nozzle for application | coating which is one of the tools, (a) is a top view around a turntable, (b) is a side view of a light shielding sensor, a syringe, and a nozzle. It is the schematic diagram which looked at the lower part of the turntable shown in FIG. 1 from the downward direction. It is explanatory drawing which shows the angle definition of the position detection method of this invention. It is explanatory drawing which shows the control conceptual diagram of the position detection method of this invention.

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiments. In addition, the well-known or well-known technique of the said technical field is applied about the part which is not illustrated or described in particular in this specification. In the drawings referred to below, the same reference numerals denote the same components.

  First, the tip position detection method and tip position detection apparatus of the present invention will be described with reference to FIGS. In addition, the automatic processing system 11 of this embodiment is a coating system. In this automatic processing system 11, a plurality of syringes 5 having nozzles 1 connected to the lower part are held on a rotary table 6. In the present embodiment, one of the plurality of arranged nozzles 1 is a reference member, and the position of a reference point 12 (see FIGS. 2 and 4) that is the tip of the nozzle 1 is detected as the tip of another nozzle 1. This is a reference for specifying the position of the point 13 (see FIG. 4). In this embodiment, the same nozzle 1 as the target nozzle 1 whose position is to be detected is used as the reference member, but another member such as a pin may be used as the reference member, and the tip thereof may be used as the reference point 12.

  The turntable 6 is rotatable around a rotation axis extending in the vertical direction. Accordingly, the syringe 5 held on the rotary table 6 and the nozzle 1 connected to the lower portion of each syringe 5 also rotate around the rotation axis. That is, the nozzle 1 serving as the reference member and the other nozzles 1 can be rotated around the same rotation axis. Each nozzle 1 is provided with its tip facing downward in the direction of the rotation axis. The motor 17 (see FIG. 5) that rotates the turntable 6 is provided with an encoder 15 (see FIG. 5) so that the rotation angle of the turntable 6 can be measured. In this embodiment, the rotation axis of the rotary table 6 which is also the rotation axis of all the nozzles 1 is vertical, but this can be inclined. In the following description, “rotary axis” means the rotary axis of the rotary table 6.

  The light shielding sensor 2 senses light shielding of the optical axis 3 between the light exiting portion and the light entering portion, and can detect the position of the nozzle 1 protruding below the syringe 5 as shown in FIGS. In addition, it is installed at the lower part of the rotary table 6. In this embodiment, the detection target of the tip position is the nozzle 1, but the position detection of the present invention can also be applied to a tool other than the nozzle 1. In particular, the present invention can be suitably applied to tools such as rod-shaped or pin-shaped drills and screwdrivers. By detecting the tip position of the tool, it is possible to correctly specify the position at which the tool performs the machining operation on the machining target.

  As shown in FIGS. 2 and 4, the light-shielding sensor 2 includes a nozzle 1 that is a reference member whose tip is a reference point 12 and a nozzle 1 that is a detection target whose tip is a detection point 13. Each is provided at a position where it intersects the optical axis 3 at two locations when rotated around. The light shielding sensor 2 is provided so that the optical axis 3 is orthogonal to the rotation axis, and is provided on an installation base 7 that can be moved up and down so as to be movable in the direction of the rotation axis. An encoder 16 (see FIG. 5) is installed on the motor 18 (see FIG. 5) for raising and lowering the seventh installation, and the position of the installation table 7 can be detected and measured.

  As shown in FIG. 5, an encoder 15 provided in a motor 17 for rotating the turntable 6 and an encoder 16 provided in a motor 18 for raising and lowering the installation table 7 are connected to the control unit 14 respectively. Yes. The encoder 15 sends rotation angle information to the control unit 14, and the encoder 16 sends lift position information to the control unit 14. The light shielding sensor 2 is also connected to the control unit 14, and sends a signal to that effect to the control unit 14 when it senses the intersection of the nozzle 1 and the optical axis 3. The control unit 14 is connected to the motors 17 and 18 and the robot 8, and operates the motors 17 and 18 and the robot 8 based on information stored in advance and information from the encoders 15 and 16 and the light shielding sensor 2. It is intended to control. Moreover, the control part 14 can calculate the position error mentioned later.

  Different syringes 5 are filled with different coating agents. When performing the application, the control unit 14 selects the syringe 5 in which a necessary coating agent is stored, rotates the rotary table 6 by a necessary rotation angle, and rotates the selected syringe 5 to a predetermined position. . Further, the control unit 14 controls the robot 8 to move the application object 9 (see FIG. 1) to a predetermined application position, and performs application by making the nozzle 1 of the selected syringe 5 and the application object 9 face each other. It will be.

  Next, a series of operations for application will be described.

  First, teaching is performed for the number of nozzles 1 that apply to the workpiece 9. In the present embodiment, one predetermined nozzle 1 is used as a reference member for teaching, and its tip is used as a reference point 12. The rotation radius R of the reference point 12 is measured in advance and stored in the control unit 14. The application position for moving the object 9 to be applied by the robot 8 can be set at an arbitrary position, but it is preferable to set it at a position where the robot 8 can easily access. Further, the position just above the application position is the movement position of the nozzle 1, and the position information is stored and accumulated in the control unit 14 so that each nozzle 1 used for application can be moved to this position. Further, the robot 8 teaches information such as the orientation and posture of the object 9 to be applied at the application position. All the taught position information is stored in the control unit 14.

  When the teaching is completed, the tip position of the reference point 12, which is the tip of the teaching reference member, is detected. The tip position detection operation will be described in detail later.

  Thereafter, the tip position of the application nozzle 1 is detected in the same manner, and position errors ΔX, ΔY, and ΔZ with respect to the reference point 12 are obtained for each nozzle 1 and the information is stored in the control unit 14 of FIG. Here, ΔX is a displacement amount in a direction perpendicular to the optical axis 3, ΔY is a displacement amount in a direction parallel to the optical axis 3 (FIG. 4), and ΔZ is a displacement amount in the rotation axis direction. At the time of application, the robot 8 corrects and moves the position difference of ΔX, ΔY, and ΔZ from the application teaching position, and applies the object 9 that is held at the correct position.

  The position detection method of the present invention will be described in detail.

  First, the reference point 12 which is the tip of the nozzle 1 as a reference member for teaching which is taught first is detected. A command is issued from the control unit 14 to the rotary table 6 to move the reference member to a predetermined rotation start point 10. When the movement is finished, a command is issued from the control unit 14 to the installation table 7 and the position is raised to a height at which the optical axis 3 of the position detection device 2 can intersect the reference point 12.

  Next, the rotary table 6 is rotated and moved so that the reference member crosses the optical axis 3 of the light shielding sensor 2. As shown in FIG. 2, the nozzle 1 which is a reference member whose tip is the reference point 12 intersects at two different points from the optical axis 3, but the first one of the intersections is clockwise and counterclockwise. Crossing so as to reciprocate from both directions. The values of the respective encoders when the reference member blocks the optical axis 3 are stored in the control unit 14 as rotation angle information, and the average values of the measured values (rotation angles θ1a, θ1b) detected in the clockwise direction and the counterclockwise direction, respectively. Is calculated as a rotation angle θ1 (see FIG. 4). This is because the center angle when the optical axis 3 intersects the nozzle 1 serving as the reference member is accurately calculated by calculating the center angle when crossing from both directions. When the calculation is finished, the control unit 14 issues a command to the rotary table 6 and moves the nozzle 1 to the position of the calculated rotation angle θ1.

  Next, at that point, the installation base 7 on which the position detection device 2 is arranged is once lowered to remove the light-shielded optical axis 3 from the intersection with the nozzle 1 from the tip side of the nozzle 1, and from the reference point 12. Release. Thereafter, the installation table 7 is raised again, and the encoder value when the nozzle 1 blocks the optical axis 3 again is stored in the control unit 14 as the position (height position Z) of the reference point 12 in the rotation axis direction.

  Next, the rotary table 6 is further rotated clockwise so that it also traverses in both the clockwise and counterclockwise directions at the other intersection with the optical axis 3, and the rotation angle is the same as described above. θ2a and θ2b are measured, and the rotation angle θ2 (see FIG. 4) is calculated.

  As described above, the rotation angles θ1 and θ2 and the height position Z with respect to the reference point 12 that is the tip of the nozzle 1 serving as the reference member can be obtained and stored and stored in the control unit 14, respectively.

  Next, detection and measurement similar to the above are performed for the coating nozzle 1 to obtain the rotation angles θ1 ′ and θ2 ′ and the height position Z ′ shown in FIG. When there are a plurality of coating nozzles 1, the same data is acquired for all nozzles 1. The acquisition of these data is performed by replacing one of the nozzles 1 with a reference member, obtaining the reference member data, and then replacing the reference member with the application nozzle 1 for measurement. You can also get data about. The obtained rotation angles θ1 ′ and θ2 ′ and the height position information Z ′ are both stored and stored in the control unit 14. Then, the detection point 13 with respect to the reference point 12 is calculated from the already measured rotation radius R, the rotation angles θ1 and θ2, the height position Z, the rotation angles θ1 ′ and θ2 ′, and the height position Z ′ obtained previously. The positional deviation amounts ΔX, ΔY, ΔZ can be obtained.

Next, a method for calculating the positional deviation amounts ΔX and ΔY will be described. Using the values obtained by the series of position detection operations described above, the plane center of the rotary table 6, that is, the center of the rotation axis is the origin, the axis orthogonal to the optical axis 3 is the X axis, and the axis is parallel to the optical axis 3 Is the Y axis. Further, as shown in FIG. 4, the angle formed by the straight line connecting the intersection point between the reference point 12 and the optical axis 3 and the origin and the X axis is A, and the straight line connecting the intersection point between the detection point 13 and the optical axis 3 and the origin. And the angle formed by the X axis is B,
A = (θ2−θ1) / 2
B = (θ2′−θ1 ′) / 2
It can be expressed.

On the other hand, as shown in FIG. 4, if the rotation angle error between the reference point 12 and the detection point 13 is φ, the angle formed by the X axis and the straight line connecting the rotation start point 10 and the origin is θ ₀ ,
φ = θ ₀ −θ1′−A
It can be expressed.

If the rotation radius of the reference point 12 is R and the rotation radius of the detection point 13 is R ′,
RcosA = R'cosB
Can be expressed as follows, and this is modified to R ′ = RcosA / cosB
It can be. Then, when the value of the rotation radius R of the nozzle 1 whose tip is the reference point 12 when taught in advance is known, the rotation radius R ′ of the coating nozzle 1 as the detection point 13 can be obtained. .

The angle θ ₀ formed by the X axis and the straight line connecting the rotation start point 10 and the origin is
θ ₀ = (θ1 + θ2) / 2
It can be expressed.

Therefore, if the point P is the application position, the point P ′ is the error position of the detection point 13 which is the tip of the application nozzle 1, and if the angle of the application position stored in advance is θ, FIG. Thus, the positional deviation amounts ΔX and ΔY between the detection point 13 and the reference point 12 to be obtained are
ΔX = R′cos (θ−θ ₀ + φ) −Rcos (θ−θ ₀ )
ΔY = R′sin (θ−θ ₀ + φ) −Rsin (θ−θ ₀ )
It becomes.

  With the above calculation method, the positional deviation amounts ΔX and ΔY between the reference point 12 and the detection point 13 at the tip of the nozzle 1 when the nozzle 1 is replaced can be obtained. In addition, as for the positional deviation amount ΔZ of the height, the height difference may be simply obtained. In the other syringes 5 arranged on the rotary table 6, the position of the detection point 13 that is the tip of the nozzle 3 connected to each syringe 5 is detected based on the reference point 12, and the error is calculated by the above calculation method. Can be obtained respectively for the positional deviation amounts ΔX, ΔY, ΔZ.

  The obtained positional deviation amounts ΔX, ΔY, and ΔZ are stored and accumulated in the control unit 14, respectively. In actual application, the tip position deviation amounts ΔX, ΔY, and ΔZ corresponding to the detection points 13 are controlled from the application position taught by the reference point 12 at the tip of the nozzle, which is a reference member for teaching. The unit 14 corrects the teaching point of the robot 8 and moves the workpiece 9 to the corrected coating position. As a result, the positional deviation from the reference position in the tip direction of the nozzle 1 that occurs when the nozzle 1 is exchanged can be eliminated, and the application object 9 can be applied with high accuracy.

  In addition, although this invention was demonstrated based on the said embodiment, this invention is not limited to this. In the said embodiment, the positional offset amount of the front-end | tip of the nozzle at the time of changing to the application nozzle for operation is calculated on the basis of the nozzle 1 connected to the syringe 5 is calculated. However, if the position detection device 2 is arranged so that the reference member serving as a reference blocks the optical axis 3 at two places, it can be applied to a screw tightening system such as a driver.

  The order of operations described in this embodiment is an example, and the order can be changed as appropriate. Furthermore, when it is not necessary to detect an error in the height direction, it can be omitted.

  1: nozzle, 2: tip position detection device, 3: optical axis, 5: syringe, 6: rotating table, 7: installation table, 8: robot, 9: workpiece, 10: rotation start point, 11: automatic processing System, 12: Reference point, 13: Detection point, 14: Control unit, 15, 16: Encoder, 17, 18: Motor

Claims (5)

In the method for detecting the tip position of a movable tool,
A light-shielding sensor that senses light-shielding of the optical axis between the light exiting part and the light entering part is provided, and the tool can be rotated about the rotational axis, provided with a reference member that can be rotationally moved about the same rotational axis as described above. When the member and the tool are rotated around the rotation axis, the optical axis is provided at a position where it intersects at two locations,
Each rotation angle θ1 from a rotation radius R when the reference member is rotated about the rotation axis from a predetermined rotation start point to two intersections between the rotation start point and the optical axis of the light-shielding sensor. And θ2 are known,
The tool is rotated around the rotation axis from the same rotation start point as described above, intersects the optical axis of the light-shielding sensor at two locations, and 2 from the rotation start point to the optical axis of the light-shielding sensor. Measure the rotation angles θ1 ′ and θ2 ′ up to the intersection of the points, and based on the rotation angles θ1 ′ and θ2 ′, the rotation radius R, and the rotation angles θ1 and θ2, a reference that is the tip of the reference member A tool tip position detection method comprising a step of calculating a positional deviation amount between a point and a detection point which is a tip of the tool.   The tool is attached with its tip directed in the direction of the rotation axis, the light shielding sensor can be moved in the direction of the rotation axis, the position of the reference point in the direction of the rotation axis is known, and the tool is shielded from light. After the rotational movement to the position intersecting the optical axis of the sensor, the light shielding sensor is moved until the intersection of the optical axis and the tool is disengaged to the tip side of the tool, and then the light shielding sensor is moved. The position of the detection point in the rotation axis direction is detected by moving the tool toward the tip side of the tool and intersecting the tip of the tool with the position of the reference point in the rotation axis direction. The tool tip position detecting method according to claim 1, further comprising a step of calculating a deviation amount.   The θ1 and θ2 are average values of the measured value when the reference member is moved clockwise and the measured value when the reference member is rotated counterclockwise, and the θ1 ′ and θ2 ′ are the clocks of the tool. 3. The tool tip position detecting method according to claim 1, wherein the tool tip position detecting method is an average value of a measured value when the tool is moved around and a measured value when the tool is rotated counterclockwise. In the tip position detection device of the movable tool,
A light-shielding sensor for sensing the light-shielding of the optical axis between the light-emitting part and the light-incident part, provided with a reference member that is capable of rotational movement about the rotational axis and a rotational member that can be rotated about the same rotational axis as described above Is provided at a position that intersects the optical axis at two locations when the reference member and the tool are rotated around the rotation axis, respectively,
Each rotation angle θ1 from a rotation radius R when the reference member is rotated about the rotation axis from a predetermined rotation start point to two intersections between the rotation start point and the optical axis of the light-shielding sensor. And θ2 stored therein, and
The tool is rotated around the rotation axis from the same rotation start point as described above, and intersects the optical axis of the light shielding sensor at two locations, so that the optical axis of the light shielding sensor is The rotation angles θ1 ′ and θ2 ′ up to the two intersections can be measured, and from the rotation angles θ1 ′ and θ2 ′, the rotation radius R, and the rotation angles θ1 and θ2, A tool tip position detection device capable of calculating a positional deviation amount between a reference point which is a tip and a detection point which is a tip of the tool.   The tool is mounted with its tip directed in the direction of the rotation axis, the light-shielding sensor is provided so as to be movable in the direction of the rotation axis, and the position of the reference point in the direction of the rotation axis is controlled. The amount of deviation between the position of the detection point in the direction of the rotation axis and the position of the reference point in the direction of the rotation axis detected by intersecting the optical axis and the tip of the tool. The tool tip position detecting device according to claim 4, wherein the tool tip position detecting device can be calculated.

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