Robot system and position detection method

Abstract

To provide a robot system and a position detection method which can accurately detect a position of a tool.SOLUTION: A robot system includes: a robot arm; a tool mounted on the robot arm; a plurality of optical sensors which is arranged so that a relative position relation between the tool and the optical sensors becomes constant, and detects a translation amount to an object; and a control device which detects a translation amount and a rotation amount of the tool on the basis of the translation amount detected by the plurality of optical sensors, and detects a position of the tool from the translation amount and the rotation amount of the tool.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a robot system and a position detection method. [Background technology]

[0002] The printing system described in Patent Document 1 prints on an object by moving a robot equipped with a print head attached to its tip and ejecting ink toward the object. The printing system also has a rotation angle sensor for detecting the actual position of the print head, and a piezo actuator that is disposed between the print head and corrects the position of the print head based on the actual position of the print head. In this way, printing without strips (gaps) is achieved by correcting the position of the print head based on the actual position of the print head. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-202781 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the printing system of Patent Document 1, due to the arrangement of the rotation angle sensor, it is difficult to detect changes in the print head's posture in the translation direction. As a result, the detection accuracy of the actual position of the print head is low, and there is a problem that it is not possible to perform high-precision printing work. [Means for solving the problem]

[0005] The robot system of the present invention includes a robot arm and a tool attached to the robotic arm; and A plurality of optical sensors are arranged so that a relative positional relationship with the tool is constant, and detect an amount of translation with respect to the object; and a control device that detects a translation amount and a rotation amount of the tool based on the translation amounts detected by the plurality of optical sensors, and detects a position of the tool from the translation amount and the rotation amount of the tool.

[0006] The position detection method of the present invention includes a robot arm, a tool attached to the robot arm, and a plurality of optical sensors that are arranged so that a relative positional relationship between the tool and the robot arm is constant and detects a translational amount with respect to an object, A translation amount and a rotation amount of the tool are detected based on the translation amounts detected by the plurality of optical sensors, and a position of the tool is detected from the translation amount and the rotation amount of the tool. [Brief description of the drawings]

[0007] [Figure 1] 1 is an overall view of a robot system according to a first embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a printing operation. [Diagram 3] FIG. 2 is a plan view showing a moving stage. [Figure 4] FIG. 2 is a cross-sectional view of an optical sensor. [Diagram 5] FIG. 2 is a schematic diagram illustrating the detection principle of an optical sensor. [Figure 6] 1A and 1B are schematic diagrams for explaining problems with optical sensors. [Figure 7] 10A and 10B are schematic diagrams for explaining a method for detecting an amount of translation and an amount of rotation. [Figure 8] 10A and 10B are schematic diagrams for explaining a method for detecting an amount of rotation. [Figure 9] 10A and 10B are schematic diagrams for explaining a method for detecting an amount of rotation. [Figure 10] FIG. 13 is a plan view showing a modified example of the arrangement of the optical sensor. [Figure 11] FIG. 13 is a plan view showing a modified example of the arrangement of the optical sensor. [Figure 12] FIG. 13 is a plan view showing a modified example of the arrangement of the optical sensor. [Figure 13]FIG. 13 is a plan view showing a modified example of the arrangement of the optical sensor. [Figure 14] FIG. 13 is a plan view showing a modified example of the arrangement of the optical sensor. [Figure 15] FIG. 13 is a plan view showing a modified example of the arrangement of the optical sensor. [Figure 16] FIG. 13 is a plan view showing a modified example of the arrangement of the optical sensor. [Figure 17] FIG. 11 is an overall view of a robot system according to a second embodiment. [Figure 18] FIG. 2 is a schematic diagram showing a printing operation. [Figure 19] FIG. 2 is a schematic diagram showing a printing operation. [Figure 20] FIG. 2 is a schematic diagram showing a printing operation. [Figure 21] FIG. 11 is an overall view of a robot system according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A robot system and a position detection method according to the present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings.

[0009] First Embodiment FIG. 1 is an overall view of a robot system according to a first embodiment. FIG. 2 is a schematic diagram showing a printing operation. FIG. 3 is a plan view showing a moving stage. FIG. 4 is a cross-sectional view of an optical sensor. FIG. 5 is a schematic diagram showing the detection principle of an optical sensor. FIG. 6 is a schematic diagram for explaining problems with an optical sensor. FIG. 7 is a schematic diagram for explaining a method for detecting a translation amount and a rotation amount. FIGS. 8 and 9 are each a schematic diagram for explaining a method for detecting a rotation amount. FIGS. 10 to 16 are each a plan view showing a modified example of the arrangement of an optical sensor.

[0010] 1 is applied to a printing system that performs printing work on an object W. The robot system 1 has a robot 2, a print head 3 as a tool attached to the tip of the robot 2, a moving stage 4 arranged between the robot 2 and the print head 3, multiple optical sensors 5 arranged on the print head 3, and a control device 9 that controls the driving of the robot 2.

[0011] <Robot 2> The robot 2 is a six-axis vertical articulated robot having six drive axes, and includes a base 21 fixed to a mounting table, a floor, etc., and a robot arm 22 rotatably connected to the base 21. The robot arm 22 is configured with six arms 221, 222, 223, 224, 225, and 226 rotatably connected in this order from the base 21 side, and includes six joints J1, J2, J3, J4, J5, and J6. Among these joints J1 to J6, the joints J2, J3, and J5 are bending joints, and the joints J1, J4, and J6 are torsion joints. In addition, a drive mechanism including a motor and an encoder is installed in each of the joints J1, J2, J3, J4, J5, and J6, and the motor is driven by servo control that feeds back the output of the encoder.

[0012] However, the configuration of the robot 2 is not particularly limited. For example, the number of arms provided in the robot arm 22 is not limited to six. The robot 2 may be a dual-arm robot, a horizontally articulated robot (SCARA robot), or the like. The robot 2 may be a robot that is not fixed to a stand, a floor, or the like, and is capable of moving on its own.

[0013] <Print Head 3> The print head 3 is disposed at the tip of the robot arm 22, i.e., on the arm 226. The print head 3 is not particularly limited, but an inkjet head is used in this embodiment. The inkjet head has an ink chamber (not shown), a vibration plate disposed on the wall of the ink chamber, and ink ejection holes 31 connected to the ink chamber, and ink I in the ink chamber is ejected from the ink ejection holes 31 by vibration of the vibration plate. Then, as shown in FIG. 2, the robot arm 22 is driven to move the print head 3 along a predetermined printing trajectory Q relative to the object W, while ejecting ink I from the print head 3 and causing it to adhere to the printing surface of the object W, thereby performing printing.

[0014] In this embodiment, the tool is the print head 3, but is not limited to this and can be changed as appropriate depending on the work to be performed on the target object W.

[0015] <Mobile Stage 4> The moving stage 4 is disposed between the arm 226 and the print head 3, and is used to correct the position of the print head 3. As shown in Fig. 3, the moving stage 4 has a base 40 supported by the arm 226, a first stage 41 that moves linearly in a first direction A relative to the base 40, and a second stage 42 that moves linearly in a second direction B perpendicular to the first direction A relative to the first stage 41. The print head 3 is disposed on the second stage 42.

[0016] The movable stage 4 also has a first stage drive unit 45 that moves the first stage 41 along a first direction A relative to the base 40, and a second stage drive unit 46 that moves the second stage 42 along a second direction B relative to the first stage 41.

[0017] The first and second stage driving units 45 and 46 each include a piezoelectric actuator 400 that is driven by utilizing the expansion and contraction of a piezoelectric element due to energization, and transmit the vibration of the piezoelectric actuator 400 to the first and second stages 41 and 42 to move them. In this way, by using the piezoelectric actuator 400, the movement amount and movement speed of the first and second stages 41 and 42 can be finely and highly accurately controlled, and the movement direction can be quickly switched. Therefore, the position correction of the print head 3 can be performed with high accuracy. In addition, the moving stage 4 can be made smaller and lighter. Therefore, the increase in the weight of the tip of the robot 2 due to the placement of the moving stage 4 can be suppressed as much as possible, and the deterioration of the driving characteristics of the robot 2, such as responsiveness and vibration damping, can be effectively suppressed.

[0018] However, the configuration of the moving stage 4 is not particularly limited. For example, the first and second stage drivers 45, 46 may be configured to use a drive source other than the piezoelectric actuator 400, such as a motor that rotates when energized. Also, the moving stage 4 may be omitted. In this case, the position of the print head 3 can be corrected by the robot arm 22.

[0019] <Optical sensor 5> 3, the optical sensor 5 is disposed on the second stage 42 of the moving stage 4 together with the above-mentioned print head 3. The position and orientation of the print head 3 (hereinafter simply referred to as "position and orientation") is detected based on the output of the optical sensor 5.

[0020] The optical sensor 5 is an optical tracking sensor 50 that is also widely applied to optical mice. The optical tracking sensor 50 has two detection axes, an x-axis and a y-axis, which are orthogonal to each other, and can detect a translation amount Δx in the x-axis direction and a translation amount Δy in the y-axis direction independently. In addition, the optical tracking sensor 50 has a rectangular shape extending along the y-axis in a plan view. However, the shape of the optical tracking sensor 50 is not particularly limited, and may be a rectangular shape extending along the x-axis, a square, a circle, or the like.

[0021] 4, the optical tracking sensor 50 includes a base 51, a pair of lens members 521 and 522, a light source 53, an image sensor 54, and a processing circuit 55. The base 51 is disposed facing the object W. Light L emitted by the light source 53 is guided to the surface of the object W by the lens member 521 and a reflecting surface formed on the inner surface of the base 51, reflected by the surface of the object W, and collected by the lens member 522 and received by the image sensor 54. The image sensor 54 continues to capture images at a period of about 1 ms, and the processing circuit 55 determines the amount of translation of the optical tracking sensor 50 with respect to the object W based on the image captured by the image sensor 54.

[0022] Specifically, by irradiating the object W with light L, as shown in FIG. 5, the image captured by the imaging element 54 has light and dark areas corresponding to minute unevenness on the surface of the object W. The processing circuit 55 compares the image Gn newly captured by the imaging element 54 with the image Gn-1 captured previously, and detects the amount of movement of the image Gn relative to the image Gn-1 using an optical flow method or the like. Based on the detection result, the processing circuit 55 detects the translation amount Δx in the x-axis direction and the translation amount Δy in the y-axis direction of the optical tracking sensor 50 relative to the object W from the time when the image Gn-1 was captured to the time when the image Gn was captured. In particular, as in this embodiment, by irradiating the object W with light L in an oblique direction, that is, from a direction inclined with respect to the normal line of the printed surface of the object W, the light and dark areas appear more clearly, and the translation amounts Δx and Δy can be detected with higher accuracy.

[0023] The light source 53 is not particularly limited, and may be, for example, an LED (light emitting diode), a laser light source, etc. The light L from the light source 53 is not particularly limited, and may be, for example, red light, blue light, infrared light, etc. The imaging element 54 is not particularly limited, and may be, for example, a CCD image sensor, a CMOS image sensor, etc.

[0024] The optical tracking sensor 50 has been described above. As can be seen from the fact that the optical tracking sensor 50 is widely used in optical mice, it is inexpensive, small, and has high detection accuracy. Therefore, by using the optical tracking sensor 50 as the optical sensor 5, it is possible to obtain a robot system 1 that is inexpensive, small, and capable of highly accurate position detection.

[0025] However, as described above, the optical tracking sensor 50 can only detect the translational amounts Δx and Δy of the optical tracking sensor 50 between the compared images, and cannot detect the rotational amount Δθ. Therefore, for example, as shown in Fig. 6, when the optical sensor 5 moves to positions P1, P2, and P3 in order while performing a translational-rotational movement that is a mixture of translational movement and rotational movement, the deviation between the actual position shown by the solid line and the detected position shown by the dashed line gradually increases.

[0026] Due to these problems, it is necessary to set a simple print trajectory Q that does not involve rotational motion, and it is not possible to set a complex print trajectory Q that involves rotational motion. As a result, complex printing cannot be performed. In order to solve these problems, the robot system 1 is configured to be able to detect not only the translation amounts Δx and Δy but also the rotation amount Δθ using multiple optical sensors 5. This makes it possible to set a complex print trajectory Q that involves rotational motion, and more complex printing can be performed.

[0027] Specifically, the robot system 1 has a first optical sensor 5A and a second optical sensor 5B as two optical sensors 5. The first and second optical sensors 5A and 5B are both optical tracking sensors 50 and have the same configuration.

[0028] 3, the first and second optical sensors 5A, 5B are both disposed on the second stage 42 via a holding member 59. Therefore, the relative positional relationship between the first and second optical sensors 5A, 5B and the print head 3 is kept constant. The holding member 59 functions as a spacer for adjusting the distance between the first and second optical sensors 5A, 5B and the target object W during printing operations.

[0029] Moreover, the first and second optical sensors 5A, 5B are both disposed such that their x-axes coincide with the first direction A and their y-axes coincide with the second direction B. By aligning the movement direction of the moving stage 4 with the detection axes of the first and second optical sensors 5A, 5B in this way, a conversion function for aligning them is unnecessary or can be simplified. This makes it easier to create a control program for the robot system 1.

[0030] The first and second optical sensors 5A and 5B are arranged in the first direction A at a distance from each other, and the print head 3 is arranged between the first and second optical sensors 5A and 5B. That is, the first and second optical sensors 5A and 5B are arranged on the opposite side of the print head 3 in the first direction A. This allows both the first and second optical sensors 5A and 5B to be arranged near the print head 3, so that the position and orientation of the print head 3 can be detected with higher accuracy. In particular, in this embodiment, the first and second optical sensors 5A and 5B are arranged symmetrically with respect to the print head 3. Therefore, the function for determining the position and orientation of the print head 3 from the outputs of the first and second optical sensors 5A and 5B is simplified, and the control program for the robot system 1 is accordingly easier to create. The coordinates of the first and second optical sensors 5A and 5B and the print head 3 are each known and stored in advance in the control device 9.

[0031] As shown in FIG. 2, the first and second optical sensors 5A and 5B are disposed on the same plane F including the first direction A (direction along the x-axis) and the second direction B (direction along the y-axis). In a printing operation, the print head 3 is moved while keeping the plane F including the first direction A and the second direction B approximately parallel to the printing surface of the object W. Therefore, by adopting such a configuration, the distances between the first and second optical sensors 5A and 5B and the object W can be made equal. Therefore, the detection conditions of the first and second optical sensors 5A and 5B can be made equal to each other, and detection errors between the first and second optical sensors 5A and 5B can be suppressed. This allows the position and orientation of the print head 3 to be detected with higher accuracy.

[0032] However, the arrangement of the first and second optical sensors 5A, 5B is not particularly limited as long as the relative positional relationship with the print head 3 is kept constant. For example, the first and second optical sensors 5A, 5B may be arranged directly on the second stage 42 without the intermediary of the holding member 59. Furthermore, the first and second optical sensors 5A, 5B may be arranged not on the second stage 42 but directly on the print head 3 or via a holding member.

[0033] Furthermore, in this embodiment, the tip faces of the first and second optical sensors 5A, 5B are flush with the tip face of the print head 3, but this is not limited thereto, and the tip faces of the first and second optical sensors 5A, 5B may protrude further toward the target W than the tip face of the print head 3, or may be retracted toward the moving stage 4. This arrangement can be set appropriately depending on the recommended separation distance between the print head 3 and the target W, the recommended separation distance between the first and second optical sensors 5A, 5B and the target W, etc.

[0034] <Control device 9> The control device 9 controls the driving of the robot 2, the print head 3, and the moving stage 4, either independently or in conjunction with each other. The control device 9 is composed of, for example, a computer, and has a processor (CPU) that processes information, a memory communicatively connected to the processor, and an external interface that connects to an external device. Various programs that can be executed by the processor are stored in the memory, and the processor can read and execute the programs stored in the memory.

[0035] This concludes the description of the configuration of the robot system 1. Next, a method for detecting the position of the print head 3 using the first and second optical sensors 5A, 5B will be described using an example of translational and rotational movement as shown in Figure 7.

[0036] In this case, the first optical sensor 5A detects its own translational movement amount Δxa (Δx) and translational movement amount Δya (Δy) using the method described above, and transmits the results to the control device 9. Similarly, the second optical sensor 5B detects its own translational movement amount Δxb (Δx) and translational movement amount Δyb (Δy) using the method described above, and transmits the results to the control device 9. Note that the first and second optical sensors 5A and 5B are synchronized, and are controlled so that images are captured by the imaging element 54 at the same timing. This makes it possible to detect the position and orientation of the print head 3 with greater accuracy.

[0037] The control device 9 calculates (Δya+Δyb) / 2, which is the average of the translation amounts Δya and Δyb, as the translation amount Δy3 in the y-axis direction of the print head 3. Similarly, the control device 9 calculates (Δxa+Δxb) / 2, which is the average of the translation amounts Δxa and Δxb, as the translation amount Δx3 in the x-axis direction of the print head 3. Furthermore, the control device 9 calculates the amount of rotation Δθ of the print head 3 from the difference (Δya-Δyb) between the translation amounts Δya and Δyb and the separation distance D between the first and second optical sensors 5A, 5B.

[0038] The control device 9 then detects the latest position and orientation Pn of the print head 3 by adding the translational amounts Δx3, Δy3 and rotational amount Δθ detected this time to the previously detected position and orientation Pn-1 of the print head 3. The control device 9 repeats the above-mentioned process each time the first and second optical sensors 5A and 5B transmit new translational amounts Δx and Δy, and updates the latest position and orientation of the print head 3. The control device 9 can also detect the trajectory of the print head 3 by connecting the detected positions and orientations in chronological order. In this way, by using multiple optical sensors 5 that can only detect translational motion alone, it is possible to easily detect not only the translational motion of the print head 3 but also the rotational motion. According to this method, the position and orientation of the print head 3 can be detected with high accuracy.

[0039] Note that the method for detecting the translation amount and rotation amount of the print head 3 is not limited to the above-mentioned method. For example, one of the translation amounts Δya and Δyb may be the translation amount of the print head 3 in the y-axis direction. Similarly, one of the translation amounts Δxa and Δxb may be the translation amount of the print head 3 in the x-axis direction.

[0040] On the other hand, the rotation amount Δθ may be calculated, for example, by using odometry. In this case, as shown in FIG. 8, the movement distance ΔLa of the first optical sensor 5A is expressed as (p+d)Δθ, and the movement distance ΔLb of the second optical sensor 5B is expressed as (pd)Δθ. From these two equations, the rotation amount Δθ=(ΔLa-ΔLb) / 2d. This method can also easily detect the rotation amount Δθ. p is the distance from the rotation center O to the print head 3, and d is D / 2. Moreover, ΔLa can be calculated as the resultant force of the translation amounts Δxa and Δya, and ΔLb can be calculated as the resultant force of the translation amounts Δxb and Δyb.

[0041] Alternatively, the translational amounts Δx3 and Δy3 of the print head 3 may be detected based on the translational amounts Δx and Δy of the first optical sensor 5A, and the rotational amount Δθ of the print head 3 may be detected based on the translational amounts Δx and Δy of the second optical sensor 5B. In this case, the translational amounts Δx and Δy of the first optical sensor 5A are set as the translational amounts Δx3 and Δy3. As shown in FIG. 9, the center of rotation O is set at the center of the first optical sensor 5A, and the rotational amount Δθ is detected based on the translational amount Δy of the second optical sensor 5A and the separation distance D (the separation distance between the center of rotation and the second optical sensor 5B). The center of rotation O is not particularly limited and can be set appropriately based on the print trajectory Q.

[0042] The method for detecting the position and orientation of the print head 3 using the first and second optical sensors 5A and 5B has been described above. Next, a printing operation on the target object W using the robot system 1 will be briefly described. The control device 9 ejects ink I from the print head 3 onto the target object W at the specified timing while moving the print head 3 along the specified print trajectory Q by controlling the driving of the robot 2. In addition, while the print head 3 is moving along the print trajectory Q, the control device 9 periodically detects the latest position and orientation of the print head 3 using the above-mentioned position and orientation detection method, and controls the driving of the moving stage 4 so that the detected position and orientation coincides with the print trajectory Q. This suppresses deviation between the actual print trajectory and the print trajectory Q, and allows high-quality printing work to be performed. In particular, since the deviation of the print trajectory is corrected by driving the moving stage 4, the print trajectory can be corrected quickly and accurately compared to, for example, the case where the deviation of the print trajectory is corrected by driving the robot 2. Therefore, a higher quality printing work is possible.

[0043] In the above description, the deviation between the print trajectory Q and the actual print trajectory is detected in real time while the printing work is being performed, and the deviation is fed back to control the driving of the moving stage 4, but the method of the printing work is not limited to this. For example, before the actual printing work is performed, a test run is performed in which the print head 3 is moved along the print trajectory Q to obtain the actual print trajectory in advance. Furthermore, the deviation between the obtained actual print trajectory and the print trajectory Q is obtained, and a drive command for the moving stage 4 for correcting the deviation is generated. Then, in the actual printing work, the print head 3 is moved along the print trajectory Q without detecting the position and orientation of the print head 3, and the moving stage 4 is moved according to the generated drive command. Even with this method, the deviation between the print trajectory Q and the actual print trajectory is reduced, and high-quality printing work can be performed.

[0044] The robot system 1 and the position detection method have been described above. As described above, the robot system 1 includes a robot arm 22, a print head 3 as a tool attached to the robot arm 22, a plurality of optical sensors 5 that are arranged so that the relative positional relationship between the print head 3 and the robot arm 22 is constant, and detects translational amounts Δx and Δy relative to the object W, and a control device 9 that detects translational amounts Δx3 and Δy3 and rotational amount Δθ of the print head 3 based on the translational amounts Δx and Δy detected by the plurality of optical sensors 5, and detects the position of the print head 3 from the translational amounts Δx3 and Δy3 and rotational amount Δθ of the print head 3. In this way, the rotational amount Δθ can be detected by using the translational amounts Δx and Δy detected by the plurality of optical sensors 5. Therefore, the change in the posture of the print head 3 relative to the translational direction can be easily detected, and the position of the print head 3 can be detected with high accuracy.

[0045] As described above, the optical sensor 5 is an optical tracking sensor 50, which includes a light source 53, a lens member 521 that irradiates light L from the light source 53 onto the object W, and an image sensor 54 that receives the light L reflected by the object W, and detects the translational amounts Δx, Δy with respect to the object W by comparing a plurality of images captured by the image sensor 54 and calculating the amount of movement of the images. In this way, by using the optical tracking sensor 50 as the optical sensor 5, the robot system 1 can be made low-cost and compact while being capable of highly accurate position detection.

[0046] As described above, the optical sensor 5 irradiates the light L obliquely onto the object W. This makes it easier for light and dark areas corresponding to minute irregularities on the surface of the object W to appear in the image captured by the imaging element 54, and allows the translational amounts Δx and Δy of the object W to be detected with high accuracy.

[0047] As described above, the optical sensor 5 has two detection axes, the x-axis and the y-axis, which are perpendicular to each other. This allows the optical sensor 5 to detect the translational amounts Δx and Δy. This makes it easy to detect the two-dimensional movement of the print head 3.

[0048] Furthermore, as described above, the print head 3 is disposed between multiple optical sensors 5. This allows the multiple optical sensors 5 to be disposed in the vicinity of each of the print heads 3, making it possible to detect the posture of the print head 3 with greater accuracy.

[0049] As described above, the tool is the print head 3, which performs a printing operation on the object W. This makes it possible to perform a high-quality printing operation.

[0050] Furthermore, as described above, the control device 9 corrects the print trajectory Q of the print head 3 based on the detected position of the print head 3. This makes it possible to suppress deviation between the actual print trajectory and the print trajectory Q, enabling higher quality printing work to be performed.

[0051] As described above, the position detection method includes a robot arm 22, a print head 3 as a tool attached to the robot arm 22, and a plurality of optical sensors 5 that are arranged so that the relative positional relationship with the print head 3 is constant and detect the translational amounts Δx and Δy with respect to the object W, and detects the translational amounts Δx3 and Δy3 and the rotational amount Δθ of the print head 3 based on the translational amounts Δx and Δy detected by the plurality of optical sensors 5, and detects the position of the print head 3 from the translational amounts Δx3, Δy3 and the rotational amount Δθ of the print head 3. In this way, the rotational amount Δθ can be detected by using the translational amounts Δx and Δy detected by the plurality of optical sensors 5. Therefore, the change in the posture of the print head 3 in the translational direction can be easily detected, and the position of the print head 3 can be detected with high accuracy.

[0052] Although the first embodiment of the robot system 1 has been described above, there is no particular limitation on the arrangement or number of the optical sensors 5. For example, the optical sensors 5 may be arranged as shown in Figs.

[0053] In the configuration shown in Fig. 10, the first and second optical sensors 5A and 5B are arranged spaced apart in the first direction A and the second direction B, respectively, and the print head 3 is arranged between them. In the configuration shown in Fig. 11, the first optical sensor 5A is further rotated 90° from the configuration shown in Fig. 10. Moreover, in the configuration shown in Fig. 12, the second optical sensor 5B is further rotated 90° from the configuration shown in Fig. 11.

[0054] In the configuration shown in Fig. 13, the first and second optical sensors 5A and 5B are arranged side by side in the second direction B. In the configuration shown in Fig. 14, the first optical sensor 5A is rotated by 90° from the configuration shown in Fig. 13. In the configuration shown in Fig. 15, the second optical sensor 5B is rotated by 90° from the configuration shown in Fig. 14.

[0055] In the configuration shown in FIG. 16, four optical sensors 5, that is, first, second, third and fourth optical sensors 5A, 5B, 5C and 5D, are arranged.

[0056] <Second embodiment> Fig. 17 is an overall view of a robot system according to the second embodiment. Fig. 18 to Fig. 20 are schematic views showing the state of a printing operation.

[0057] The robot system 1 according to this embodiment is similar to the robot system 1 according to the first embodiment, except that a force sensor 7 is disposed on the robot 2. In the following description, the robot system 1 according to this embodiment will be described with a focus on the differences from the first embodiment, and a description of the similarities will be omitted. In addition, in each drawing of this embodiment, the same reference numerals are used for the same configurations as those in the above-mentioned embodiment.

[0058] 17, in the robot system 1 of this embodiment, the first and second optical sensors 5A, 5B are provided protruding toward the target object W side from the print head 3. In addition, a force sensor 7 is disposed between the robot 2 and the moving stage 4. The force sensor 7 has three detection axes that are perpendicular to each other, and can independently detect translational forces (axial forces) along each detection axis and rotational forces (torques) around each detection axis. In the robot system 1, the force sensor 7 is used to detect contact between the first and second optical sensors 5A, 5B and the target object W.

[0059] According to this configuration, by feeding back the detection result of the force sensor 7, as shown in FIG. 18, the print head 3 can be moved along the print trajectory Q while the first and second optical sensors 5A, 5B are lightly brought into contact with the object W with a predetermined force. According to this method, the distance between the first and second optical sensors 5A, 5B and the object W can be kept constant (zero). Therefore, the detection error of the first and second optical sensors 5A, 5B caused by the variation in the distance between the first and second optical sensors 5A, 5B and the object W is reduced, and the translation amounts Δx, Δy can be detected with higher accuracy. In addition, the distance between the print head 3 and the object W can be kept constant, so that higher quality printing can be performed.

[0060] In the above example, the first and second optical sensors 5A and 5B are in contact with the object W, but the present invention is not limited thereto. For example, as shown in FIG. 19, a contact portion 6 for contacting the object W may be separately arranged and the contact portion 6 may be in contact with the object W. For example, by printing while the contact portion 6 is in contact with a position that does not overlap with the printing area of ​​the object W or with an area of ​​the printing area that has not yet been printed, contact with ink I that is not completely dried can be suppressed. Therefore, printing of higher quality can be performed. In the illustrated example, the contact portion 6 protrudes from the holding member 59, but the configuration of the contact portion 6 is not particularly limited.

[0061] Furthermore, when the force sensor 7 detects contact between the first and second optical sensors 5A, 5B and the object W, control is performed to move the first and second optical sensors 5A, 5B slightly away from the object W so that they are not in contact, thereby allowing the print head 3 to move in a manner that traces the vicinity of the surface of the object W, as shown in Figure 20. With this method, the distance between the print head 3 and the object W can be made smaller and fluctuations in that distance can be suppressed, resulting in higher quality printing.

[0062] As described above, the robot system 1 of this embodiment has a force sensor 7 that detects contact with the target object W. Based on the detection results of the force sensor 7, it is possible to reduce fluctuations in the distance between the print head 3 and the target object W, enabling higher quality printing to be performed.

[0063] The second embodiment as described above can also achieve the same effects as the first embodiment described above.

[0064] <Third embodiment> FIG. 21 is an overall view of a robot system according to the third embodiment.

[0065] The robot system 1 according to this embodiment is similar to the robot system 1 according to the first embodiment, except that the target object W is transported by a conveyor 8. In the following description, the robot system 1 according to this embodiment will be described with a focus on the differences from the first embodiment, and a description of the similarities will be omitted. In the drawings of this embodiment, the same reference numerals are used to designate the same components as those in the above-described embodiment.

[0066] As shown in FIG. 21, the robot system 1 of the present embodiment 1 has a conveyor 8 that conveys the object W. In addition, a camera 81 is disposed directly above the conveyor 8. The control device 9 captures the object W flowing on the conveyor 8 with the camera 81, and detects the position of the object W on the conveyor 8 based on the image obtained thereby. In addition, the control device 9 predicts the time when the object W will arrive at the work area of ​​the robot 2 and the movement trajectory within the work area based on the position of the object W detected as described above and the conveying speed of the conveyor 8, and controls the drive of the robot 2 so that the print head 3 moves along the print trajectory Q relative to the object W based on the prediction. In this way, by conveying the object W using the conveyor 8, the supply of the object W into the work area of ​​the robot 2 becomes easy and smooth. Therefore, the cycle time of the printing work can be shortened.

[0067] As described above, the robot system 1 of this embodiment has a conveyor 8 that transports objects W, and uses the print head 3 to perform work on the objects W transported by the conveyor 8. This configuration makes it easy and smooth to supply the objects W into the work area of ​​the robot 2. This makes it possible to shorten the cycle time of work.

[0068] The third embodiment as described above can also achieve the same effects as the first embodiment described above.

[0069] Although the robot system and the position detection method of the present invention have been described above with reference to the illustrated embodiments, the present invention is not limited thereto, and the configurations and steps of each part can be replaced with any configurations and steps having similar functions. Any other configurations and steps may be added to the present invention. Furthermore, each embodiment may be appropriately combined. [Explanation of symbols]

[0070] 1...robot system, 2...robot, 21...base, 22...robot arm, 221...arm, 222...arm, 223...arm, 224...arm, 225...arm, 226...arm, 3...print head, 31...ink ejection hole, 4...moving stage, 40...base, 400...piezoelectric actuator, 41...first stage, 42...second stage, 45...first stage drive unit, 46...second stage drive unit, 5...optical sensor, 5A...first optical sensor, 5B...second optical sensor, 5C...third optical sensor, 5D...fourth optical sensor, 50...optical tracking sensor, 51...base, 521...lens member, 522...lens member, 53...light source, 5 4...imaging element, 55...processing circuit, 59...holding member, 6...contact portion, 7...force sensor, 8...conveyor, 81...camera, 9...control device, A...first direction, B...second direction, D...separation distance, F...plane, Gn...image, Gn-1...image, I...ink, J1...joint, J2...joint, J3...joint, J4...joint, J5...joint, J6...joint, L...light, O...center of rotation, P1...position, P2...position, P3...position, Pn...position and orientation, Pn-1...position and orientation, Q...printing trajectory, W...object, ΔLa...movement distance, ΔLb...movement distance, Δx...translation amount, Δx3...translation amount, Δxa...translation amount, Δxb...translation amount, Δy...translation amount, Δy3...translation amount, Δya...translation amount, Δyb...translation amount, Δθ...rotation amount

Claims

1. A robot arm; a tool attached to the robotic arm; and A plurality of optical sensors are arranged so that a relative positional relationship with the tool is constant, and detect an amount of translation with respect to the object; a control device that detects the translational and rotational amounts of the tool based on the translational amounts detected by the plurality of optical sensors, and detects the position of the tool from the translational and rotational amounts of the tool.

2. the optical sensor is an optical tracking sensor; A light source; a lens member that irradiates the object with light from the light source; an image sensor that receives the light reflected by the object; The robot system according to claim 1 , wherein a translational movement amount relative to the object is detected by comparing a plurality of images captured by the imaging element and calculating a movement amount of the images.

3. The robot system according to claim 2 , wherein the optical sensor irradiates the light onto the object from an oblique direction.

4. The robot system according to claim 1 , wherein the optical sensor has two detection axes perpendicular to each other.

5. The robot system of claim 1 , wherein the tool is disposed between the plurality of optical sensors.

6. the tool being a print head; The robot system according to claim 1 , wherein the robot system performs a printing operation on the object.

7. The robot system of claim 6 , wherein the control device corrects a printing trajectory of the print head based on a position of the print head.

8. The robot system according to claim 1 , further comprising a force sensor for detecting contact with the object.

9. A conveyor for conveying the object is provided, The robot system according to claim 1 , wherein the robot system performs an operation on the object transported by the conveyor using the tool.

10. a robot arm; a tool attached to the robot arm; and a plurality of optical sensors disposed so that a relative positional relationship between the tool and the robot arm is constant and configured to detect a translational amount relative to an object; A position detection method comprising the steps of detecting a translation amount and a rotation amount of the tool based on the translation amounts detected by a plurality of the optical sensors, and detecting a position of the tool from the translation amount and the rotation amount of the tool.

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