JP2011075391A - Position management device for movable shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a position management device capable of accurately managing the position and posture of a movable shaft although it includes an inexpensive and a simple structure. <P>SOLUTION: The position management device 20 for the movable shaft includes: a light projection means 21 emitting a light beam BL; a reflection means 22 diffuse reflecting the light beam BL; a light receiving means 23 receiving the reflected light and for output of a light amount thereof; and a sensor amplifier as a detection means detecting a shift amount of a tool 12 from a reference position on the basis of the output value from the light receiving means 23. The light projection means 21 is mounted on a rack 6 as a stationary body, and the reflection means 22 and the light receiving means 23 on the tool 12 provided at the tip of a robot arm 11 constituted by connecting a plurality of movable shafts. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a movable shaft position management device.

  For example, during welding of an underbody and a side member that are welded to each other in a car body welding line of an automobile, it is necessary to position the side member with respect to the underbody. Positioning was performed. However, in this way, there are various problems in recent years when multi-product production is progressing to meet a wide variety of needs. Specifically, it is necessary to prepare a large number of dedicated jigs, which increases initial investment and storage space, and the problem that production efficiency does not increase because it is necessary to replace dedicated jigs for each product type. Is mentioned. Therefore, in recent years, a robot such as a so-called articulated robot is sometimes introduced into a production line and the workpiece is positioned by the robot.

  For example, the posture / position of a movable shaft that constitutes a robot arm (also referred to as a manipulator) of an articulated robot is controlled by numerical information given from an encoder incorporated in the movable shaft. However, it is difficult to control the attitude and position of the movable shaft with high accuracy only by the encoder. That is, the servo motor that is the drive source of the robot arm may have problems such as shaft slip and gear backlash, and the deviation of the stop position of the movable shaft due to such problems cannot be detected by the encoder. Therefore, it is customary to install a separate management device for managing the posture and position of the movable shaft in the robot (production line). An example of such a management device is a visual sensor as described in Patent Document 1.

JP 2003-31670 A

  The visual sensor is useful in that the attitude and position of the movable shaft can be managed and controlled with high accuracy, but there is a problem that the equipment investment is increased because the device is generally an expensive device. In addition, since the visual sensor is a device that is complicated to manage and control itself, there is also a problem that a great deal of labor and labor are required for various setting operations and maintenance.

  In addition to the visual sensor, it is conceivable to use a position sensor whose main components are a light projecting unit and a light receiving unit that are arranged to face each other. In this case, for example, the position of the movable axis can be managed by attaching a laser oscillator as a light projecting means to a stationary body such as a gantry on which the robot is installed, and attaching a laser light receiving unit as a light receiving means to the robot arm (movable axis). It can be carried out. However, although such a position sensor is inexpensive, it is not determined that an abnormality has occurred as long as the emitted laser beam is received by the laser beam receiving unit, and thus a large position shift that prevents the laser beam from hitting the laser beam receiving unit. (For example, about several mm) can only be detected. For this reason, it is basically impossible to detect a minute positional deviation, and it is not functionally sufficient as a management apparatus for dealing with recently required quality. A highly sensitive position sensor capable of detecting a minute position shift is also commercially available. However, such a position sensor is as expensive as a visual sensor, and the actual situation is that it cannot be adopted in consideration of capital investment.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to accurately determine the posture and position of a movable shaft that is controlled based on numerical information while having a relatively inexpensive and simple configuration. An object of the present invention is to provide a position management device that can be managed well, and to construct a production line that can stably produce high-quality products while suppressing capital investment as much as possible.

  In order to solve the above-described problems, the present invention provides a position management device for managing the position of a movable shaft, which is attached to either the movable shaft or the stationary body and projects a light beam onto the other. A light means, a reflection means attached to the other and diffusely reflecting the light beam emitted from the light projecting means, a light receiving means attached to the one or the other, receiving the reflected light and outputting the light amount; And a detecting means for detecting a shift amount of the movable shaft from a reference position based on an output value from the movable shaft. The “stationary body” referred to here means a base, a frame, a floor surface, or the like that does not move by itself, and “reflected light” refers to light (light flux) that is diffusely reflected by the reflecting means. The “reference position” refers to a position serving as a reference when detecting the amount of displacement of the movable shaft (determining whether or not there is a position displacement), and is not limited to the origin of the movable shaft.

  As described above, a general position sensor detects if the light beam emitted from the light projecting means is diffusely reflected and the amount of shift of the movable axis from the reference position is detected based on the amount of received reflected light. It is possible to detect a minute positional deviation from a reference position that is difficult to do. This is because the amount of deviation is detected based on the amount of received light of the diffusely reflected light beam (reflected light). That is, if the received light amount of the reflected light is used as an index for determining the amount of deviation, the amount of light received by the light receiving means greatly changes even when the movable shaft is slightly displaced from the reference position. In addition, the position management device of the present invention has a simple configuration in which a reflection unit is added to the configuration of a general position sensor, and a laser oscillator that can be considered to be used as a projection unit is equivalent to the reflection unit. It is sufficient to use an inexpensive laser that can irradiate a laser that diffuses after that, that is, a laser with low beam intensity. Therefore, the position management device according to the present invention can manage the position accuracy of the movable shaft with high accuracy while having a low-cost and simple configuration as compared with a visual sensor or the like.

  Further, with the position management device having the above-described configuration, it is possible to detect the shift amount of the movable axis from the reference position simply by irradiating the light beam from the light projecting means, so that it is easy and highly accurate to determine abnormality every cycle. Can be done. For example, a threshold value can be set in advance in the detection means, and the movable shaft can be immediately stopped when the amount of deviation from the reference position exceeds the threshold value. Furthermore, if the deviation amount for each cycle is recorded, it is possible to grasp the tendency of the positional deviation of the movable shaft, so that preventive maintenance can be performed efficiently.

  In addition, as a specific attachment mode of each component means of the above-described position management device, (1) the light projecting means and the light receiving means are attached to either the movable shaft or the stationary body, and the reflection means is attached to the other, or (2) It is conceivable that the light projecting means is attached to either the movable shaft or the stationary body, and the reflecting means and the light receiving means are attached to the other. Although the configuration (1) has the merit that the connection (wiring) between each means can be extremely simplified, the light receiving means receives the reflected light and outputs the amount of light. Therefore, it may be difficult to increase the distance between the light projecting / receiving unit and the reflecting unit. On the other hand, the configuration (2) has an advantage that the distance between the light projecting unit and the reflecting unit can be increased, although the connection between the units is easily complicated as compared with the configuration (1). Accordingly, whether to adopt the above configuration (1) or (2) may be selected in consideration of various factors.

  In the above configuration, the reflecting means can be configured to be detachable from the mounted member. In this way, it is possible to set the sensitivity of the management device to an appropriate level corresponding to the required quality level. For example, in order to increase the sensitivity, that is, to enable detection of a smaller amount of deviation, the reflection means may be changed to a reflecting means having a curved surface with a large curvature.

  As described above, according to the present invention, it is possible to provide a position management device capable of managing the position accuracy of the movable shaft with high accuracy while having an inexpensive and simple configuration. This makes it possible to construct a production line that can stably produce high-quality products while minimizing capital investment.

1 is a partial schematic perspective view of an automobile body welding line provided with a position management device according to an embodiment of the present invention. It is a block diagram which shows typically the whole structure of the position management apparatus shown in FIG. It is a principal part enlarged view of the position management apparatus shown in FIG. 1, and is an enlarged view in case a robot arm exists in a reference position. It is a principal part enlarged view of the position management apparatus shown in FIG. 1, and is an enlarged view which shows notionally the case where the robot arm has shifted from the reference position. It is a figure which shows an example of correlation with the light reception amount of reflected light, and the deviation | shift amount from a reference position. It is a figure which shows the other example of correlation with the light reception amount of reflected light, and the deviation | shift amount from a reference position. It is a block diagram which shows typically the whole structure of the position management apparatus which concerns on other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following, in order to perform position management of a robot arm of an articulated robot configured by connecting a plurality of movable axes, more precisely, a tool attached to the tip of the robot arm, the position management according to the present invention is performed. The description will be given by taking the case of using the apparatus as an example.

  FIG. 1 is a partial schematic perspective view of a vehicle body welding line 1 for welding a pair of side members 5 and 5 and a roof panel (not shown) to an underbody 4. The underbody 4 is transported toward the downstream side on the transport conveyor 2 while being placed on the transport pallet 3, and the underbody 4 to be transported is paired in a plurality of steps provided along the transport conveyor 2. Side members 5 and 5 and a roof panel (not shown) are sequentially welded. In addition, FIG. 1 extracts and shows the temporary assembly process of the side members 5 and 5 among the some processes provided along the conveyance conveyor 2. FIG. On both sides of the conveyor 2 in the width direction, a stand 6 as a stationary body is provided, and a robot 10 is installed on the stand 6. However, in FIG. 1, illustration of the robot provided in the width direction one side of the conveyance conveyor 2 is abbreviate | omitted.

  The robot 10 in the illustrated example transfers the side member 5 set up on a stock unit (not shown) to a predetermined position (fixed position with the side member 4) and positions and holds the side member 5 at the predetermined position during temporary assembly. Take a role. The robot 10 in the illustrated example is a so-called multi-joint robot formed by connecting a plurality of movable shafts, and has a robot arm 11 having a joint structure capable of turning, stretching, tilting, and the like, and a tertiary at the tip of the robot arm 11. A tool 12 that is attached so as to be movable and that grips the side member 5 is provided as a main component. The robot 10 incorporates a servo motor (not shown), and each movable shaft and the tool 12 constituting the robot arm 11 perform various operations in response to an operation command of the servo motor. Although illustration is omitted, an encoder is incorporated in the robot arm 11 (each movable axis), and each movable axis of the robot arm 11 is controlled based on numerical information given from the encoder.

  The robot 10 installed along the conveyor 2 is provided with a position management device 20 according to the present invention. The position management device 20 has an abnormality that is difficult to detect with an encoder incorporated in the robot arm 11, such as a posture / position abnormality of the robot arm 11 caused by a shaft slip of a servo motor, a gear backlash, etc. (Abnormal position) is detected, and a stop command or the like is transmitted based on the detection result. Furthermore, for example, the robot arm 11 and the tool 12 perform a series of operations based on a program from a state stopped at the origin, and then return to the origin and stop. This operation cycle is repeated. However, when the servo motor is caused to slip by repeated operations and the position accuracy at a predetermined position (reference position) is lowered, each movable axis of the robot arm 11 and the tool 12 are changed in the subsequent cycles. Operational quality and thus product quality are adversely affected. The location management device 20 is used to prevent such problems. Details will be described below.

  As schematically shown in FIG. 2, the position management device 20 of the present invention includes a light projecting means 21 attached to a gantry 6 as a stationary body and a mounting base 24 as a member to be attached (refer to FIG. 3 for details). ) And the reflecting means 22 for diffusing and reflecting the light beam BL irradiated from the light projecting means 21 and the light beam BL (reflected light BL ′) diffused and reflected by the reflecting means 22 and receiving the light quantity thereof And a sensor amplifier 27 as a detecting means connected to the light receiving means 23, and a display device 28 and a control device 29 are further connected to the sensor amplifier 27.

  The light projecting unit 21 has a light source that irradiates the light beam BL toward the reflecting unit 22 as a main part. The light source is defined by a low-energy light beam BL, such as JIS C6802, that has directivity that does not attenuate as much as possible until it reaches the reflecting means 22 and diffuses when it hits the reflecting means 22. A laser oscillator capable of irradiating (emitting) a “class 1” laser is used.

  In the present embodiment, the reflecting means 22 and the light receiving means 23 are fixed to a mounting base 24 as a mounted member to be mounted on the tool 12 as a unit as shown in FIG. The reflecting means 22 is a hemispherical portion provided at the tip, diffuses and reflects the light beam BL irradiated from the light projecting means 21 (having a convex curved reflecting surface that diffusely reflects the light beam BL), and a reflection part 22a It is a pin-shaped member integrally provided with a screw portion 22b inserted into the hole 24a of the base 24, and a mounting base is obtained by screwing a nut 25 to the screw portion 22b inserted into the hole 24a. 24 is fixed. That is, the reflecting means 22 is configured to be detachable from the mounting base 24. In the present embodiment, the reflecting means 22 is fixed to the mounting base 24 so that its axis Op is parallel to the axis Ob of the light beam BL irradiated from the light projecting means 21. However, the axis Op of the reflecting means 22 is not on the axis Ob of the light beam BL, and the reflecting means 22 is fixed to the mounting base 24 at a position where the axis Op is shifted by a predetermined amount in the radial direction from the axis Ob of the light beam BL. .

  The light receiving means 23 has a light receiving portion (light receiving surface) 23 a at the tip, and outputs the amount of light received by the light receiving portion 23 a to the sensor amplifier 27. The light receiving unit 23 receives the light beam BL (reflected light BL ′) diffused and reflected by the reflecting unit 22 a of the reflecting unit 22, so that the light receiving unit 23 a is aligned with the axis Ob of the light beam BL irradiated from the light projecting unit 21. It is fixed to the mounting base 24 at an angle to the mounting base 24. More specifically, the light receiving means 23 irradiates the light beam BL from the light projecting means 21 in a state where the tool 12 is at a reference position for detecting and determining the amount of deviation of the tool 12 (the state shown in FIG. 3). The position and orientation at which the amount of the reflected light BL ′ received by the light receiving unit 23a is maximized (here, the position and orientation where the center of the reflected light BL ′ coincides with the center of the light receiving unit 23a). Fixed to the mounting base 24.

  The sensor amplifier 27 plays a role of detecting and determining the amount of deviation of the tool 12 from the reference position for each cycle based on the output value from the light receiving means 23 (light receiving unit 23a). In order to make this possible, the sensor amplifier 27 includes a recording element on which data indicating the correlation between the amount of reflected light BL ′ received by the light receiving unit 23 a and the amount of deviation of the tool 12 from the reference position is recorded. It has been incorporated. On the display device 28 connected to the sensor amplifier 27, numerical data corresponding to the light amount of the reflected light BL 'received by the light receiving unit 23a is monitored and displayed.

  An example of the correlation data recorded in the recording element is shown in FIG. As is clear from FIG. 5, there is a correlation in which the amount of reflected light BL 'decreases as the amount of deviation of the tool 12 increases. Two threshold values A and B are set for the sensor amplifier 27. The first threshold A is a critical value for sending an abnormality warning. That is, it is determined that the received light amount of the reflected light BL ′ input to the sensor amplifier 27 is below the first threshold value A, and the amount of deviation of the tool 12 from the reference position is greater than a predetermined value, here 0.2 mm. Then, an abnormality warning is displayed on the display device 28 by monitoring. The second threshold value B is a critical value for outputting a signal for stopping the servo motor that is a drive source of the robot arm 11 and the tool 12. That is, it is determined that the received light amount of the reflected light BL ′ input to the sensor amplifier 27 is less than the second threshold value B, and the amount of deviation of the tool 12 from the reference position is greater than a predetermined value, here 0.3 mm. Then, a signal for stopping the servo motor which is a drive source of the robot arm 11 and the tool 12 is output to the control device 29.

  During operation of the robot 10, the light beam BL is irradiated from the light projecting means 21 toward the reflecting means 22 every time the robot arm 11 and the tool 12 return to predetermined positions, and the light receiving means 23 (light receiving portion 23a). The amount of the reflected light BL ′ received at is output to the sensor amplifier 27. At this time, as shown in FIG. 4, if the tool 12 is displaced from the reference position, the reflected light BL ′ cannot be received by the light receiving unit 23a to the maximum (the center of the reflected light BL ′ is the light receiving unit 23a). 3), the amount of the reflected light BL ′ received by the light receiving unit 23a is smaller than that shown in FIG. When it is determined that the amount of received light is less than the first threshold A and the amount of deviation of the tool 12 from the reference position is greater than 0.2 mm, an abnormality warning is displayed on the display device 28 by monitoring. If it is determined that the amount of received light is less than the second threshold value B and the amount of deviation of the tool 12 from the reference position is greater than 0.3 mm, the robot arm receives a stop signal input to the control device 29. 11 and the tool 12 are stopped.

  In the case where the light beam emitted from the light projecting means is directly received by the light receiving means, such as a general position sensor, even if the tool is slightly displaced from the reference position, the range of the light receiving portion of the light receiving means Since it is not determined as abnormal as long as the luminous flux is irradiated inside, it is basically impossible to detect a minute positional deviation of the tool 12. On the other hand, when the received light amount of the reflected light BL ′ is used as an index for determining the deviation amount as in the present invention, it is clear from FIG. 5 even when the tool 12 is slightly displaced from the reference position. The amount of light received by the light receiving unit 23a greatly changes. Therefore, as in the present invention, the light beam BL irradiated from the light projecting means 21 is diffusely reflected, and the amount of deviation of the tool 12 from the reference position (in other words, the robot arm 11 is moved based on the amount of reflected light BL ′ received). If a displacement amount of the movable axis to be configured is detected, it is possible to detect a minute positional deviation from a reference position that is difficult to detect with a general position sensor.

  More specifically, in a general position sensor that directly receives the light beam emitted from the light projecting means by the light receiving means, the tool is not displaced for the first time when the amount of deviation of the tool from the reference position becomes several mm or more. On the other hand, with the configuration of the present invention, it is determined that the tool 12 is misaligned only by a positional deviation of several tens of μm, as is clear from FIG. Can do.

  Further, the position management device 20 of the present invention has a simple configuration in which a reflection unit 22 is added to the configuration of a general position sensor, and the light source constituting the main part of the light projecting unit 21 is a reflection unit. An inexpensive laser oscillator capable of emitting a laser (class 1 laser) having a weak beam intensity that diffuses after hitting the reflecting portion 22a of 22 is sufficient. As described above, the position management device 20 according to the present invention can manage the position accuracy of the movable shaft with high accuracy while having a low-cost and simple configuration as compared with a known visual sensor or the like. As a result, it is possible to construct a production line capable of stably producing a high-quality product (here, the assembly of the underbody 4 and the side member 5) while suppressing capital investment as much as possible.

  Further, in the position management device 20 of the present invention, a minute shift amount of the tool 12 (movable axis) from the reference position can be detected simply by irradiating the light beam BL from the light projecting means 21, so that every cycle. Abnormality determination can be performed easily and with high accuracy. That is, as described above, if a threshold value is set in advance in the sensor amplifier 27 serving as the detecting means, the amount of reflected light BL ′ is less than the threshold value (here, the second threshold value B), and the tool from the reference position is set. The robot arm 11 can be configured to stop immediately when the amount of deviation 12 becomes relatively large. In addition, if the amount of deviation for each operation cycle of the tool 12 is recorded (if it is monitored and displayed on the display device 28), the tendency of the positional deviation of the tool 12 to be detected can be grasped. Maintenance can be performed efficiently.

  In addition, since the reflecting means 22 is configured to be detachable from the mounting base 24 as the mounted member, the sensitivity of the position management device 20 should be set to an appropriate value according to the configuration of the robot arm 11 and the required quality level. Can do. For example, if the tip is replaced with the reflecting means 22 having the reflecting portion 22a provided with a convex curved portion having a larger curvature, the sensitivity of the position management device 20 can be further improved, that is, a finer reference. It is possible to detect the amount of deviation from the position.

  Note that when the reference position for detecting the amount of deviation of the tool 12 is changed, data indicating the correlation between the amount of received light of the reflected light BL ′ and the amount of deviation of the tool 12 from the reference position may be changed. . FIG. 6 shows correlation data when the distance between the light projecting means 21 and the reflecting portion 22a of the reflecting means 22 is different from the case shown in FIG. 5 (specifically when it is increased). Yes, two threshold values A ′ and B ′ are set as described above. The first threshold value A ′ is a critical value for monitoring and displaying an abnormal warning on the display device 28, and the second threshold value B ′ is for outputting a signal for stopping the servo motor to the control device 29. It is a critical value.

  The position management device 20 for the movable shaft according to the embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and various types are possible without departing from the gist of the present invention. Changes can be made.

  For example, in the position management device 20 described above, the light beam BL emitted from the light projecting unit 21 is diffusely reflected by using the reflecting unit 22 including the reflecting portion 22a having a convex curved end. The reflecting portion 22a may have a prism-like portion (a reflecting surface is configured by a plane) having a large number of planes continuously provided at the tip thereof. In the position management apparatus 20 described above, the two threshold values A and B (A ′, B ′) are set, but it is of course possible to set the threshold value to 1 or 3 or more.

  In addition, the position management device 20 described above is such that the light projecting means 21 is attached to the gantry 6 as a stationary body, and the reflecting means 22 and the light receiving means 23 are attached to the tool 12, but conversely, The light projecting means 21 may be attached to the tool 12, and the reflecting means 22 and the light receiving means 23 may be attached to the gantry 6.

  In the above description, the case where the light projecting means 21 and the light receiving means 23 are separately attached has been described. For example, as shown in FIG. The reflecting means 22 may be attached to 12. In this way, there is an advantage that the connection between each means can be simplified as compared with the embodiment described above. However, in this case, due to the configuration of the present invention that the light receiving means 23 receives the reflected light BL ′ and outputs the amount of light, the light receiving means 23 (and the light projecting means 21) and the reflecting means 22 are separated. It may be difficult to increase the distance as compared with the above-described embodiment. Therefore, whether to adopt the configuration shown in FIG. 2 or the configuration shown in FIG. 7 may be selected in consideration of various factors. Even when the apparatus configuration shown in FIG. 7 is adopted, the reflecting means 22 may be attached to the gantry 6, and the light projecting means 21 and the light receiving means 23 may be attached to the tool 12.

  The case where the position management device 20 according to the present invention is used to manage the position of the robot arm 11 (the tool 12 attached to the tip of the robot arm 11) formed by connecting a plurality of movable axes has been described above. However, the position management device 20 according to the present invention may be a position management device such as a movable shaft that operates in one axial direction, a movable shaft that operates in three axial directions (XYZ directions), and a movable shaft that rotates. Is preferred. That is, the position management device 20 according to the present invention is used not only for the robot arm of an articulated robot, but also for managing the position of a robot arm such as a Cartesian coordinate type robot or a cylindrical coordinate type robot. It can also be preferably used as a device for managing the position of the shaft.

1 Car body welding line 4 Underbody 5 Side member 6 Mount (stationary body)
10 Robot 11 Robot arm (movable axis)
12 Tool 20 Position management device 21 Light projecting means 22 Reflecting means 22a Reflecting part 23 Light receiving means 23a Light receiving part 24 Mounting base (attached member)
27 Sensor amplifier (detection means)
28 Display device 29 Control device BL Light flux BL 'Reflected light

Claims (2)

A position management device for managing the position of a movable axis,
A light projecting means that is attached to either the movable shaft or the stationary body and irradiates the other with a light beam;
Reflecting means attached to the other and diffusely reflecting the light beam emitted from the light projecting means;
A light receiving means attached to the one or the other, receiving reflected light and outputting the amount of light;
A movable shaft position management device comprising: detecting means for detecting a shift amount of the movable shaft from a reference position based on an output value from the light receiving means.   The position management apparatus of the movable shaft according to claim 1, wherein the reflecting means is configured to be detachable from a member to be attached.

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