Printing method and robot system

Abstract

To provide a printing method and a robot system which can detect the position of a printing head without providing a pattern for image recognition on an object, and enable highly precise printing.SOLUTION: A printing method, which relatively moves an object and a printing head arranged in a robot arm along a printing track, using a robot having a robot body having the robot arm, the printing head, and an optical sensor which has an imaging element for imaging the object and has a constant relative positional relation between the printing head and the optical sensor, and thereby performs printing work on the object, moves the printing head along the printing track, compares two images which have been imaged by the imaging element and have different imaging timings and thereby detects an actual position of the printing head, and corrects the position of the printing head, on the basis of deviation of the actual position to the printing track.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a printing method and a robotic system. [Background technology]

[0002] The printing system described in Patent Document 1 prints on an object by ejecting ink toward the object while moving a robot equipped with a print head attached to its tip along a print track. 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, the print head trajectory is deviated by vibration, making it difficult to perform high-precision printing. Also, for example, if the target object does not have a pattern for image processing, it is difficult to detect the deviation in the trajectory. [Means for solving the problem]

[0005] The printing method of the present invention uses a robot having a robot body equipped with a robot arm, a print head arranged on the robot arm, and an optical sensor equipped with an image pickup element for picking up an image of an object and having a constant relative positional relationship with the print head, A printing method for performing a printing operation on an object by relatively moving the object and the print head along a printing trajectory, comprising: The print head is moved along the print track, and an actual position of the print head is detected by comparing two images captured by the image sensor at different image capturing timings; The position of the print head is corrected based on the deviation of the actual position relative to the print trajectory.

[0006] The robot system of the present invention includes: a robot body having a robot arm; A tool disposed on the robot arm and performing an operation on an object; an optical sensor including an image sensor for capturing an image of the object and having a constant relative positional relationship with the tool; The control device moves the object and the tool relatively along a work trajectory, detects the actual position of the tool by comparing two images captured by the imaging element at different timings, and corrects the position of the tool based on the deviation of the actual position with respect to the work trajectory. [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] 5A and 5B are schematic diagrams for explaining a method for detecting the position of a print head. [Figure 7] 11 is a flowchart illustrating a printing method. [Figure 8] 1A and 1B are schematic diagrams for explaining problems with optical sensors. [Figure 9]FIG. 11 is a diagram showing the relationship between translation amounts Δx and Δy. [Figure 10] FIG. 11 is a diagram showing the relationship between translation amounts Δx and Δy. [Figure 11] FIG. 13 is a diagram showing a method for measuring the inclination θ. [Figure 12] FIG. 13 is a diagram showing a method for measuring the inclination θ. [Figure 13] FIG. 2 is a block diagram showing a circuit for generating an error signal. [Figure 14] FIG. 2 is a block diagram showing a circuit for generating a vibration signal. [Figure 15] FIG. 2 is a block diagram showing a circuit for generating a vibration signal. [Figure 16] FIG. 2 is a block diagram showing a circuit for generating a vibration signal. [Figure 17] 10 is a flowchart illustrating a modified example of a printing method. [Figure 18] FIG. 11 is an overall view of a robot system according to a second embodiment. [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. 2 is a schematic diagram showing a printing operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a printing method and a robot system according to the present invention will be described in detail based on 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 a method for detecting the position of a print head. FIG. 7 is a flowchart for explaining a printing method. FIG. 8 is a schematic diagram for explaining a problem with an optical sensor. FIG. 9 and FIG. 10 are diagrams showing the relationship between translation amounts Δx and Δy, respectively. FIG. 11 and FIG. 12 are diagrams showing a method for measuring an inclination θ, respectively. FIG. 13 is a block diagram showing a circuit for generating an error signal. FIG. 14 to FIG. 16 are block diagrams showing circuits for generating a vibration signal, respectively. FIG. 17 is a flowchart for explaining a modified example of a printing method.

[0010] The robot system 1 shown in Fig. 1 is applied to a printing system that performs a printing operation on an object W. The robot system 1 has a robot 10. The robot 10 has a robot body 2, a print head 3 as a tool attached to the tip of the robot body 2, a moving stage 4 arranged between the robot body 2 and the print head 3, an optical sensor 5 arranged on the print head 3, and a control device 9 that controls the driving of the robot 10.

[0011] <Robot body 2> The robot body 2 is a six-axis vertical articulated robot having six drive shafts, and includes a base 21 fixed to a mounting table, a floor, or the like, 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 as a drive source and an encoder for detecting the amount of rotation of the joint is installed in each of the joints J1, J2, J3, J4, J5, and J6.

[0012] However, the configuration of the robot body 2 is not particularly limited. For example, the number of arms provided on the robot arm 22 is not limited to six. The robot body 2 may be a dual-arm robot, a horizontally articulated robot (SCARA robot), or the like. The robot body 2 may be self-propelled without being fixed to a stand, floor, or the like.

[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] <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.

[0015] 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.

[0016] 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 caused by 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 precisely 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 body 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 body 2, such as responsiveness and vibration damping, can be effectively suppressed.

[0017] 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.

[0018] <Optical sensor 5> 3, the optical sensor 5 is disposed on the second stage 42 of the moving stage 4 together with the print head 3 described above. Therefore, the relative positional relationship between the print head 3 and the optical sensor 5 is kept constant. The position of the print head 3 is detected based on the output of the optical sensor 5.

[0019] 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.

[0020] 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.

[0021] 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 irregularities on the surface of the object W. The processing circuit 55 then compares the image Gn 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. That is, the processing circuit 55 detects the amount of movement of the image Gn relative to the image Gn-1 by comparing the brightness information of the image Gn and the image Gn-1. Based on the detection result, the processing circuit 55 then detects the translational amounts Δx, Δy 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.

[0022] In particular, as in this embodiment, by irradiating light L onto object W from an oblique direction, that is, from a direction inclined with respect to the normal to the printing surface of object W, the light and dark areas become more clearly apparent, and the translational amounts Δx and Δy can be detected more accurately.

[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] <Control device 9> The control device 9 controls the driving of the robot body 2, print head 3, optical sensor 5, and 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 external devices. 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.

[0026] The control device 9 also uses the optical tracking sensor 50 to detect the position of the print head 3 as follows. As described above, the relative positional relationship between the optical tracking sensor 50 and the print head 3 is constant. Therefore, as shown in FIG. 6, the control device 9 regards the translation amount Δx detected by the optical tracking sensor 50 as the movement amount Δx3 in the direction along the x-axis of the print head 3 as it is, and regards the translation amount Δy as the movement amount Δy3 in the direction along the y-axis of the print head 3 as it is. The control device 9 then detects the position Pn of the print head 3 by adding the movement amounts Δx3 and Δy3 of the print head 3 detected this time to the position Pn-1 of the print head 3 detected last time. The control device 9 repeats the above-mentioned process each time the optical tracking sensor 50 transmits new translation amounts Δx and Δy, and updates the latest position of the print head 3. The control device 9 can also detect the trajectory of the print head 3 by connecting the repeatedly detected positions of the print head 3 in a chronological order.

[0027] The above describes the configuration of the robot system 1. Next, a method for printing on an object W using the robot system 1 will be described. The printing method includes a pre-measurement step S1 and a printing step S2, as shown in Fig. 7. Each of these steps S1 and S2 will be described in detail below.

[0028] In the printing method using the robot system 1, the print trajectory Q is composed only of the translational motion of the print head 3 and does not substantially include the rotational motion of the print head 3. As described above, the optical tracking sensor 50 can detect only the translational motion amounts Δx and Δy relative to the object W, and cannot detect the rotational motion amount Δθ relative to the object W. Therefore, as shown in FIG. 8, if the print trajectory Q includes a rotational motion, a deviation occurs between the position of the print head 3 detected based on the translational motion amounts Δx and Δy and the actual position of the print head 3 (hereinafter, also simply referred to as the "actual position"). Therefore, by configuring the print trajectory Q only with the translational motion of the print head 3, it is possible to suppress the deviation between the position of the print head 3 detected based on the translational motion amounts Δx and Δy and the actual position of the print head 3. As a result, even if an inexpensive optical tracking sensor 50 is used, the position of the print head 3 can be detected with high accuracy, and high-precision printing can be performed. In this embodiment, a case will be described in which the print trajectory Q is set along the x-axis.

[0029] <Pre-measurement step S1> In this embodiment, since the print trajectory Q is set to be aligned with the x-axis, the print head 3 does not move in the y-axis direction while moving along the print trajectory Q, as shown by the solid line L1 in FIG. 9. However, for example, due to the mounting accuracy of the optical tracking sensor 50 or a setting error of the print trajectory Q, the x-axis may be tilted with respect to the print trajectory Q as shown in FIG. 10. In other words, the tilt of the x-axis with respect to the print trajectory Q may deviate from the design value. When the x-axis is tilted with respect to the print trajectory Q, the optical tracking sensor 50 continues to move in the y-axis direction while moving along the print trajectory Q. Therefore, as shown by the solid line L2 in the figure, the translation amount Δy continues to increase even though the print head 3 is moving along the print trajectory Q, and the position of the print head 3 detected from the translation amounts Δx and Δy accordingly deviates from the actual position of the print head 3.

[0030] Vibrations occurring in the print head 3 also cause the actual position of the print head 3 to deviate from the print trajectory Q. Note that the solid line L2 in Figure 10 shows the state in which the positional deviation of the optical tracking sensor 50 and the vibrations occurring in the print head 3 are superimposed.

[0031] Therefore, in a pre-measurement step S1, the control device 9 measures the inclination of the x-axis with respect to the print trajectory Q before the printing operation. Specifically, the control device 9 first moves the print head 3 along the print trajectory Q under the same conditions as the actual printing operation except that the ink I is not ejected from the print head 3, and measures the trajectory of the print head 3 based on the translation amounts Δx and Δy output from the optical tracking sensor 50. Next, as shown in FIG. 11, the control device 9 approximates the trajectory measured using the least squares method to a linear function f1, and stores the inclination of the approximated linear function f1 as the inclination θ of the x-axis with respect to the print trajectory Q. Alternatively, as shown in FIG. 12, the control device 9 finds a linear function f2 that makes the distance D1 from the start point of the print trajectory Q in the y-axis direction equal to the distance D2 from the end point of the print trajectory Q in the y-axis direction, and stores the inclination of the found linear function f2 as the inclination θ of the x-axis with respect to the print trajectory Q. However, the calculation direction of the inclination θ is not particularly limited.

[0032] 13, the control device 9 corrects the translational amounts Δx, Δy detected by the optical tracking sensor 50 with the tilt θ, and detects the actual position of the print head 3 based on the corrected values. In this way, by correcting the translational amounts Δx, Δy with the tilt θ, the tilt of the x-axis with respect to the print trajectory Q can be canceled, and the actual position of the print head 3 can be detected with high accuracy. In this way, with the robot system 1, even if a pattern for image recognition is not provided on the target object W, the actual position of the print head 3 can be detected with high accuracy.

[0033] Furthermore, the control device 9 compares the actual position of the print head 3 with the print trajectory Q, i.e., the target value, and generates an error signal that represents the amount of deviation of the actual position of the print head 3 with respect to the print trajectory Q. The error signal includes a movement direction error signal that represents the deviation in the direction along the print trajectory Q, and an orthogonal direction error signal that represents the deviation in the direction perpendicular to the print trajectory Q.

[0034] Next, the control device 9 extracts the vibration component from the error signal generated as described above, and generates a correction signal used to correct the position of the print head 3.

[0035] Specifically, the control device 9 first generates a vibration signal from which noise has been removed by extracting a predetermined frequency component from the error signal. The vibration signal includes a moving direction vibration signal obtained by extracting a predetermined frequency component from the moving direction error signal, and an orthogonal direction vibration signal obtained by extracting a predetermined frequency component from the orthogonal direction error signal. In this embodiment, frequency components less than 3 Hz are considered to be low-frequency noise, frequency components between 3 Hz and 50 Hz are considered to be vibration components, and frequency components over 50 Hz are considered to be high-frequency noise. However, which frequency bands are considered to be noise and which frequency bands are considered to be vibration components are not particularly limited, and can be appropriately set according to the characteristics of the device to be used.

[0036] The method of generating a vibration signal from an error signal is not particularly limited, and for example, as shown in FIG. 14, a method of passing the error signal through a low-pass filter LPF can be used. In this case, a low-pass filter LPF that passes frequency signals of less than 3 Hz is used to remove the passed frequency signals from the error signal, thereby obtaining a vibration signal from which low-frequency noise has been cut. In addition, as shown in FIG. 15, a method of passing the error signal through a high-pass filter HPF can be used. In this case, a vibration signal from which low-frequency noise has been cut can be obtained by using a high-pass filter HPF that passes frequency signals of 3 Hz or more. In addition, as shown in FIG. 16, for example, the error signal is expressed in the frequency domain by Fourier transform (FFT), and then frequency components from 3 Hz to 50 Hz are extracted using a band-pass filter BPF, and finally, the signal is returned to the time domain representation by inverse Fourier transform (IFFT), thereby obtaining a vibration signal from which low-frequency noise and high-frequency noise have been cut.

[0037] Next, the control device 9 generates an inverse phase signal of the vibration signal, and sets this as a correction signal. The correction signal includes a moving direction correction signal, which is an inverse phase signal of the moving direction vibration signal, and an orthogonal direction correction signal, which is an inverse phase signal of the orthogonal direction vibration signal.

[0038] <Printing step S2> In the printing step S2, the robot arm 22 is driven to move the print head 3 along the print trajectory Q, while the moving stage 4 is driven based on the correction signal to correct the position of the print head 3. In other words, the robot arm 22 is driven to move the print head 3 along the print trajectory Q, while the moving stage 4 is driven to cancel vibrations of the print head 3.

[0039] According to this method, the deviation of the actual position of the print head 3 from the print trajectory Q can be kept small, and preferably the actual position of the print head 3 can be made to coincide with the print trajectory Q. This allows for highly accurate printing. In particular, by canceling the vibration of the print head 3 by driving the moving stage 4, the responsiveness to the correction signal is improved compared to the case where the vibration of the print head 3 is cancelled by driving the robot arm 22. Therefore, the vibration of the print head 3 can be cancelled with higher accuracy, allowing for highly accurate printing. However, the moving stage 4 may be omitted and the vibration of the print head 3 may be cancelled by driving the robot arm 22.

[0040] The printing method using the robot system 1 has been described above, but the printing method is not particularly limited. For example, in the above-mentioned method, a correction signal is generated prior to the printing step S2, and in the printing step S2, the position of the print head 3 is corrected using the correction signal generated in advance, but the present invention is not limited to this, and it is also possible to detect the deviation of the print head 3 from the print trajectory Q in real time during the printing step S2, and feedback-control the moving stage 4 based on the detection result.

[0041] Even in such a case, the printing method has a pre-measurement step S1 and a printing step S2, as shown in FIG. 17. In the pre-measurement step S1, the inclination θ is measured and stored. In the printing step S2, the control device 9 moves the print head 3 along the print trajectory Q, and detects the actual position of the print head 3 based on the translation amounts Δx, Δy and the inclination θ detected by the optical tracking sensor 50 at a set period during that time. Furthermore, the control device 9 generates a correction signal based on the deviation of the actual position with respect to the print trajectory Q, and feedback controls the drive of the moving stage 4 using the generated correction signal. In this way, the deviation of the print head 3 with respect to the print trajectory Q is detected in real time, and the vibration of the print head 3 can be accurately canceled by feedback controlling the moving stage 4 so that the deviation becomes small, preferably zero, and printing can be performed with high accuracy. Note that the method of measuring the inclination θ and the method of generating the correction signal can be appropriately used according to the above-mentioned methods, but the method shown in FIG. 16 cannot be used.

[0042] The robot system 1 and the printing method using the robot system 1 have been described above. As described above, this printing method uses a robot 10 having a robot body 2 equipped with a robot arm 22, a print head 3 arranged on the robot arm 22, and an optical sensor 5 equipped with an image sensor 54 for capturing an image of an object W and having a constant relative positional relationship with the print head 3, and performs printing on the object W by moving the object W and the print head 3 relatively along a print track Q. The print head 3 is moved along the print track Q, and two images captured by the image sensor 54 at different image capturing times are compared to detect the actual position of the print head 3, and the position of the print head 3 is corrected based on the deviation of the actual position relative to the print track Q. According to this configuration, the position of the print head 3 is detected based on two images captured of the object W, so that the position of the print head 3 can be detected with high accuracy even if the object W does not have a pattern for image recognition. In addition, by correcting the position of the print head 3 based on the detection result, the deviation of the print head 3 relative to the print track Q can also be suppressed. Therefore, printing can be performed with high accuracy.

[0043] As described above, the optical sensor 5 is an optical tracking sensor 50 that 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 position of the print head 3 by comparing brightness information of the two images. With this configuration, the position of the print head 3 can be detected with high accuracy.

[0044] As described above, the optical sensor 5 irradiates the object W with light L from an oblique direction. 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, allowing the position of the print head 3 to be detected with high accuracy.

[0045] Furthermore, as described above, the print trajectory Q is made up of the translational motion of the print head 3. This makes it possible to detect the position of the print head 3 with high accuracy even if the optical sensor 5 can only detect the translational motion of the print head 3.

[0046] Furthermore, as described above, the robot 10 is disposed between the robot arm 22 and the print head 3, has a moving stage 4 that displaces the print head 3, and corrects the position of the print head 3 by driving the moving stage 4. This improves responsiveness compared to when the position of the print head 3 is corrected by driving the robot arm 22, and allows the position of the print head 3 to be corrected with greater accuracy.

[0047] As described above, the robot system 1 includes the robot main body 2 equipped with the robot arm 22, the print head 3 disposed on the robot arm 22 as a tool for performing work on the object W, the optical sensor 5 equipped with an image sensor 54 for capturing an image of the object W and having a constant relative positional relationship with the print head 3, and the control device 9 that moves the object W and the print head 3 relatively along a print track Q, which is a work track, detects the actual position of the print head 3 by comparing two images captured by the image sensor 54 at different image capturing times, and corrects the position of the print head 3 based on the deviation of the actual position with respect to the print track Q. With this configuration, the position of the print head 3 can be detected based on two images captured of the object W. Therefore, the position of the print head 3 can be detected with high accuracy.

[0048] As described above, the tool is the print head 3 and the work is printing. This makes it possible to perform printing work with high accuracy.

[0049] <Second embodiment> Fig. 18 is an overall view of a robot system according to the second embodiment. Fig. 19 to Fig. 21 are schematic views showing the state of a printing operation.

[0050] The robot system 1 according to this embodiment is similar to the robot system 1 according to the first embodiment, except that the robot 10 has a force sensor 7. 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.

[0051] As shown in Fig. 18, in the robot system 1 of this embodiment, the optical tracking sensor 50 is provided so as to protrude toward the target object W side beyond the print head 3. In addition, a force sensor 7 is disposed between the robot main body 2 and the moving stage 4. The force sensor 7 has three detection axes that are mutually perpendicular, and can independently detect translational forces (axial forces) along each detection axis and rotational forces (torques) about each detection axis. In such a robot system 1, the force sensor 7 is used to detect contact between the optical tracking sensor 50 and the target object W.

[0052] According to this configuration, by feeding back the detection result of the force sensor 7, as shown in FIG. 19, the print head 3 can be moved along the print trajectory Q while the optical tracking sensor 50 is lightly brought into contact with the object W with a predetermined force. According to this method, the distance between the optical tracking sensor 50 and the object W can be kept constant. This reduces detection errors of the optical tracking sensor 50 caused by fluctuations in the distance between the optical tracking sensor 50 and the object W, and allows the translation amounts Δx and Δy to be detected with higher accuracy. In addition, since the distance between the print head 3 and the object W can be kept constant, printing can be performed with higher accuracy.

[0053] In the above example, the optical tracking sensor 50 is brought into contact with the object W, but the present invention is not limited thereto. For example, as shown in FIG. 20, a contact portion 6 for contacting the object W may be separately arranged and brought into contact with the object W. For example, by carrying out printing while bringing the contact portion 6 into 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 has not yet dried can be suppressed. Therefore, printing can be carried out with higher accuracy. 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.

[0054] Furthermore, when the force sensor 7 detects contact between the optical tracking sensor 50 and the object W, control is performed to move the optical tracking sensor 50 slightly away from the object W so that they are not in contact, and the print head 3 can be moved so as to trace the vicinity of the surface of the object W, as shown in Figure 21. According to 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, allowing for more accurate printing.

[0055] As described above, in the robot system 1 of this embodiment, the robot 10 has a force sensor 7 that detects contact with the target object W, and corrects the position of the print head 3 based on the detection results of the force sensor 7. This makes it possible to reduce fluctuations in the distance between the print head 3 and the target object W, enabling printing to be performed with higher accuracy.

[0056] Although the printing method and robot system of the present invention have been described above with reference to the illustrated embodiment, the present invention is not limited thereto, and the configuration and steps of each part can be replaced with any configuration or step having a similar function. For example, the configuration and steps can be replaced with conveyor tracking, adhesive application, polishing, welding, or other steps, and any tool can be used in place of the print head. In addition, any other configuration or step may be added to the present invention. Furthermore, each embodiment may be combined as appropriate. [Explanation of symbols]

[0057] 1...robot system, 10...robot, 2...robot body, 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, 50...optical tracking sensor, 51...base, 521...lens member, 522...lens member, 53...light source, 54... Image sensor, 55...processing circuit, 59...holding member, 6...contact portion, 7...force sensor, 9...control device, A...first direction, B...second direction, D1...separation distance, D2...separation distance, Gn...image, Gn-1...image, I...ink, J1...joint, J2...joint, J3...joint, J4...joint, J5...joint, J6...joint, L...light, L1...solid line, L2...solid line, Pn...position, Pn-1...position, Q...printing trajectory, S1...pre-measurement step, S2...printing step, W...object, f1...linear function, f2...linear function, Δx...translation amount, Δx3...movement amount, Δy...translation amount, Δy3...movement amount, Δθ...rotation amount, θ...tilt

Claims

1. A robot having a robot body with a robot arm, a print head arranged on the robot arm, and an optical sensor having an image pickup element for picking up an image of an object and having a constant relative positional relationship with the print head is used, A printing method for performing a printing operation on an object by relatively moving the object and the print head along a printing trajectory, comprising: moving the print head along the print track, and detecting an actual position of the print head by comparing two images captured by the image sensor at different image capturing times; and correcting the position of the print head based on the deviation of the actual position relative to the print trajectory.

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; The imaging element receives the light reflected by the object, 2. The printing method according to claim 1, wherein the amount of movement of the print head is detected by comparing brightness information of the two images.

3. The printing method according to claim 2 , wherein the optical sensor irradiates the object with the light from an oblique direction.

4. 3. The method of claim 2, wherein the print trajectory comprises a translational movement of the print head.

5. the robot has a force sensor that detects contact with the object; The printing method according to claim 1 , further comprising the step of correcting the position of the print head based on the detection result of the force sensor.

6. the robot has a moving stage disposed between the robot arm and the print head for displacing the print head; The printing method according to claim 1 , further comprising the step of correcting the position of the print head by driving the moving stage.

7. A robot body having a robot arm; A tool disposed on the robot arm and performing an operation on an object; an optical sensor including an image sensor for capturing an image of the object and having a constant relative positional relationship with the tool; a control device that moves the object and the tool relatively along a work trajectory, detects an actual position of the tool by comparing two images captured by the imaging element at different timings, and corrects the position of the tool based on a deviation of the actual position relative to the work trajectory.

8. the tool being a print head; The robot system according to claim 7 , wherein the task is printing.

Images