Method for controlling a drive system, method for controlling a robot system, drive system and robot system

Abstract

The present invention provides a control method for a drive system, a control method for a robot system, a drive system, and a robot system that can effectively suppress positional displacement of a driven object. [Solution] A control method for a drive system comprising a piezoelectric drive device having a vibrating body and a driven body that moves in a first direction relative to the vibrating body by vibrating the vibrating body, wherein the vibrating body or the driven body receives an external force in the first direction, the method comprising: a drive start step of starting the vibration of the vibrating body; and a work start step of starting position correction control to correct the position of the driven body, and after the position of the driven body has been corrected to a target position by the position correction control, starting the movement of the driven body while maintaining the position correction control.

Description

[Technical Field]

[0001] The present invention relates to a drive system control method, a robot system control method, a drive system, and a robot system. [Background Art]

[0002] The piezoelectric driving device described in Patent Document 1 includes a driven member and a piezoelectric vibrating body that drives the driven member. The piezoelectric vibrating body includes a vibrating portion and a contact disposed at a tip end of the vibrating portion, and the contact is pressed against the driven member. Therefore, when the piezoelectric driving device is stopped, the driven member is braked by a frictional force generated by contact with the piezoelectric vibrating body. On the other hand, during driving, vibration of the vibrating portion is transmitted to the driven member via the contact, and the driven member moves relative to the piezoelectric vibrating body. [Prior Art Literature] [Patent Literature]

[0003] [Patent Literature 1] Japanese Unexamined Patent Application Publication No. 2019-30092 [Summary of Invention] [Problem to be Solved by Invention]

[0004] In such a piezoelectric driving device, the braking force applied to the driven member may weaken immediately after driving is started (immediately after the vibrating portion starts vibrating). This is caused by insufficient growth of the vibration of the vibrating portion. When the braking force weakens, the driven member may unintentionally displace relative to the piezoelectric vibrating body due to an external force such as its own weight, which may cause position deviation. [Means for Solving Problem]

[0005] The present invention provides a control method for a drive system comprising a piezoelectric drive device having a vibrating body and a driven body that moves in a first direction relative to the vibrating body by vibrating the vibrating body, wherein the vibrating body or the driven body receives an external force in the first direction. A drive start step in which the vibration of the vibrating body is initiated, The process includes a step of starting position correction control to correct the position of the driven object, and after the position of the driven object has been corrected to the target position by the position correction control, starting the movement of the driven object while maintaining the position correction control.

[0006] The control method for a robot system of the present invention comprises a moving stage comprising a piezoelectric drive device having a vibrating body and a driven body that moves in a first direction relative to the vibrating body by vibrating the vibrating body, and a stage that is displaced by the drive of the piezoelectric drive device, A control method for a robot system comprising a robot arm that holds the aforementioned moving stage, After moving the moving stage so that the first direction is perpendicular to the external force, the movement of the driven body is started.

[0007] The present invention provides a drive system comprising a vibrating body, a driven body that moves in a first direction relative to the vibrating body by vibrating the vibrating body, and a control device that controls the driving of the vibrating body, wherein the vibrating body or the driven body receives an external force in the first direction, and the drive system is further provided with a piezoelectric drive device. After the vibration of the vibrating body begins, the control device starts position correction control to correct the position of the driven body, corrects the position of the driven body to the target position using the position correction control, and then starts the movement of the driven body while maintaining the position correction control.

[0008] The robot system of the present invention comprises a moving stage comprising a piezoelectric drive device having a vibrating body and a driven body that moves in a first direction relative to the vibrating body by vibrating the vibrating body, and a stage that is displaced by the drive of the piezoelectric drive device, The robot arm holding the moving stage comprises After moving the moving stage so that the first direction is perpendicular to the external force, the movement of the driven body is started. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an overall configuration diagram of the robot system according to the first embodiment. [Figure 2] Figure 2 shows an example of a printed track. [Figure 3] Figure 3 is a plan view of the moving stage. [Figure 4] Figure 4 is a plan view showing the first piezoelectric drive device. [Figure 5] Figure 5 is a plan view showing a piezoelectric actuator. [Figure 6] Figure 6 is a plan view showing the second piezoelectric drive device. [Figure 7] Figure 7 shows an example of the drive voltage applied to the piezoelectric actuator. [Figure 8] Figure 8 is a plan view showing the state of the piezoelectric actuator when the drive voltage shown in Figure 7 is applied. [Figure 9] Figure 9 shows an example of the drive voltage applied to the piezoelectric actuator. [Figure 10] Figure 10 is a plan view showing the state of the piezoelectric actuator when the drive voltage shown in Figure 9 is applied. [Figure 11] Figure 11 is a graph showing the relationship between thrust and drive frequency. [Figure 12] Figure 12 is a graph showing the changes in thrust and holding force during downsweep control. [Figure 13] Figure 13 is a flowchart illustrating the control method of the robot system. [Figure 14] Figure 14 shows an example of the position and orientation of the print head when printing begins. [Figure 15]FIG. 15 is a diagram for explaining a control method of a robot system according to a second embodiment. Mode for Carrying Out the Invention

[0010] A detailed description is given below based on the drive system control method, robot system control method, drive system, and robot system of the present invention.

[0011] <First Embodiment> FIG. 1 is an overall configuration diagram of a robot system according to a first embodiment. FIG. 2 is a diagram showing an example of a print trajectory. FIG. 3 is a plan view of a moving stage. FIG. 4 is a plan view showing a first piezoelectric drive device. FIG. 5 is a plan view showing a piezoelectric actuator. FIG. 6 is a plan view showing a second piezoelectric drive device. FIG. 7 is an example of a drive voltage applied to the piezoelectric actuator. FIG. 8 is a plan view showing a state of the piezoelectric actuator when the drive voltage shown in FIG. 7 is applied. FIG. 9 is an example of a drive voltage applied to the piezoelectric actuator. FIG. 10 is a plan view showing a state of the piezoelectric actuator when the drive voltage shown in FIG. 9 is applied. FIG. 11 is a graph showing the relationship between thrust and drive frequency. FIG. 12 is a graph showing changes in thrust and holding force during downsweep control. FIG. 13 is a flowchart for explaining a control method of the robot system. FIG. 14 is a diagram showing an example of the position and posture of a print head when starting printing.

[0012] A robot system 10 as the drive system 1 shown in FIG. 1 includes a robot 2 and a control device 9 that controls driving of the robot 2. The robot 2 is a vertical articulated robot (6-axis robot) that performs inkjet printing on an object W. Such a robot 2 includes a robot main body 3 provided with a base 31 and a robot arm 32, a moving stage 4 disposed at a distal end of the robot arm 32, a print head 8 as a tool disposed on the moving stage 4, and an inertia sensor 7 disposed on the print head 8.

[0013] In such a robot system 10, as shown in FIG. 2, printing on an object W is performed by ejecting ink I from the print head 8 at a predetermined timing while moving the print head 8 along the printing trajectory Q using the robot main body 3 and the moving stage 4. However, the work performed by the robot 2 is not limited to printing work, and may be, for example, work such as feeding, removing, transporting, and assembling precision instruments and components constituting the same. Then, a tool arranged on the moving stage 4 may be appropriately selected according to the work content.

[0014] First, the robot main body 3 will be described. As shown in FIG. 1, the base 31 is fixed to a floor or the like. The robot arm 32 includes a first arm 321 rotatably connected to the base 31, a second arm 322 rotatably connected to the first arm 321, a third arm 323 rotatably connected to the second arm 322, a fourth arm 324 rotatably connected to the third arm 323, a fifth arm 325 rotatably connected to the fourth arm 324, and a sixth arm 326 rotatably connected to the fifth arm 325.

[0015] Further, the robot main body 3 includes a first arm driving mechanism 331 that rotates the first arm 321 relative to the base 31, a second arm driving mechanism 332 that rotates the second arm 322 relative to the first arm 321, a third arm driving mechanism 333 that rotates the third arm 323 relative to the second arm 322, a fourth arm driving mechanism 334 that rotates the fourth arm 324 relative to the third arm 323, a fifth arm driving mechanism 335 that rotates the fifth arm 325 relative to the fourth arm 324, and a sixth arm driving mechanism 336 that rotates the sixth arm 326 relative to the fifth arm 325. These first to sixth arm driving mechanisms 331 to 336 each include, for example, a motor M as a driving source, a speed reducer T that decelerates the rotation of the motor M to increase torque and outputs the same, and an encoder E that detects the rotation amount of the motor M. By independently driving the first to sixth arms 321 to 326 respectively by these first to sixth arm driving mechanisms 331 to 336, the distal end of the robot arm 32 can be set to a predetermined position and posture.

[0016] The robot body 3 has been described above, but the configuration of the robot body 3 is not particularly limited. For example, the robot body 3 may be able to move on its own by attaching the base 31 to a transport vehicle such as an AGV (Automatic Guided Vehicle). Also, the number of arms that the robot arm 32 has may be five or fewer, or seven or more. Furthermore, the robot body 3 is not limited to a vertical articulated robot, but may be a horizontal articulated robot (SCARA robot), for example.

[0017] Next, we will describe the moving stage 4. The moving stage 4 is fixed to the sixth arm 326. For the sake of explanation, in the following, we will define the X and Y axes as two mutually orthogonal axes relative to the moving stage 4. The direction along the X axis will also be referred to as the "X-axis direction," and the direction along the Y axis will be referred to as the "Y-axis direction."

[0018] As shown in Figure 3, the moving stage 4 includes a base 40 fixed to the sixth arm 326, a first stage 41 which is movable in the X-axis direction relative to the base 40, a second stage 42 which is movable in the Y-axis direction relative to the first stage 41, a first piezoelectric drive device 5 which moves the first stage 41 in the X-axis direction relative to the base 40, and a second piezoelectric drive device 6 which moves the second stage 42 in the Y-axis direction relative to the first stage 41. The movement of the first stage 41 in directions other than the X-axis direction is restricted by a guide, and the movement of the second stage 42 in directions other than the Y-axis direction is restricted by a guide.

[0019] Furthermore, as shown in Figure 4, the first piezoelectric drive device 5 includes a piezoelectric actuator 51 as a vibrating body located on the base 40, a slider 52 as a driven body located on the first stage 41 and moving in the X-axis direction as a first direction relative to the piezoelectric actuator 51, a position detection device 53 for detecting the position of the slider 52, and a biasing member 54 for biasing the piezoelectric actuator 51 toward the slider 52. However, the configuration of the first piezoelectric drive device 5 is not particularly limited, and for example, the piezoelectric actuator 51 may be located on the first stage 41 and the slider 52 may be located on the base 40.

[0020] The slider 52 is integrally formed with the first stage 41. In other words, a part of the first stage 41 also serves as the slider 52. However, it is not limited to this, and the slider 52 may be constructed separately from the first stage 41 and fixed to the first stage 41 with screws, adhesive, or the like.

[0021] As shown in Figure 5, the piezoelectric actuator 51 includes a vibrating part 511, a support part 512 that supports the vibrating part 511, a beam part 513 that connects the vibrating part 511 and the support part 512, and a convex contact element 514 positioned at the tip of the vibrating part 511. Of these, the vibrating part 511, the support part 512, and the beam part 513 are integrally formed from a silicon substrate or the like. In contrast, the contact element 514 is made of a hard material such as ceramics and is fixed to the vibrating part 511 with adhesive or the like.

[0022] The vibrating section 511 is equipped with first piezoelectric elements P11 and P12 for causing the vibrating section 511 to expand and contract in the Y-axis direction, and second piezoelectric elements P21, P22, P23, and P24 for causing the vibrating section 511 to bend and contract in an S-shape in the X-axis direction. Of these, the first piezoelectric elements P11 and P12 are arranged in the center of the vibrating section 511, aligned in the Y-axis direction. The second piezoelectric elements P21 and P22 are arranged in the Y-axis direction on the positive X-axis side of the first piezoelectric elements P11 and P12, and the second piezoelectric elements P23 and P24 are arranged in the Y-axis direction on the negative X-axis side. These first and second piezoelectric elements P11, P12, and P21-P24 each expand and contract in the Y-axis direction when energized. However, the number and arrangement of the first and second piezoelectric elements are not particularly limited, as long as the vibrating section 511 can generate both expansion and contraction vibration and bending vibration.

[0023] As shown in Figure 4, the biasing member 54 has a base portion 541 fixed to the base 40 by screws or the like, an actuator holding portion 542 fixed to the support portion 512 by adhesive or the like and holding the piezoelectric actuator 51, and a plurality of leaf springs 543 connecting the base portion 541 and the actuator holding portion 542. These base portion 541, actuator holding portion 542 and leaf springs 543 are integrally formed from a silicon substrate or the like. This biasing member 54 is fixed to the base 40 with the leaf springs 543 elastically deformed in the Y-axis direction, and the elastic force (restoring force) of the leaf springs 543 presses the contact element 514 against the side surface of the slider 52.

[0024] The position detection device 53 is an encoder, and may be an incremental encoder that detects the amount of movement of the slider 52 when it moves, or an absolute encoder that detects the absolute position of the slider 52 from the origin regardless of whether the slider 52 moves or not. As shown in Figure 4, the position detection device 53 has a scale 531 installed on the main surface of the slider 52 and an optical element 532 positioned opposite the scale 531. The scale 531 is composed of a predetermined pattern, specifically a pattern in which parts with high and low light reflectivity are arranged alternately. On the other hand, the optical element 532 has a light-emitting element 532a that irradiates light toward the pattern of the scale 531 and a light-receiving element 532b that receives the light reflected by the scale 531. The position detection device 53 can detect the amount of movement, movement speed, absolute position, etc. of the slider 52 based on the light-receiving result of the light-receiving element 532b. However, the configuration of the position detection device 53 is not particularly limited as long as it can perform its function. For example, the position detection device 53 may be configured to detect the amount of movement, speed of movement, absolute position, etc., of the slider 52 by template matching using an image sensor.

[0025] As shown in Figure 6, the second piezoelectric drive device 6 includes a piezoelectric actuator 61 located on the first stage 41, a slider 62 located on the second stage 42 as a driven object that moves in the Y-axis direction as a first direction relative to the piezoelectric actuator 61, a position detection device 63 for detecting the position of the slider 62, and a biasing member 64 for biasing the piezoelectric actuator 61 toward the slider 62. Since such a second piezoelectric drive device 6 has the same configuration as the first piezoelectric drive device 5 described above, a detailed explanation will be omitted. The configuration of the second piezoelectric drive device 6 is not particularly limited, and, similar to the first piezoelectric drive device 5, for example, the piezoelectric actuator 61 may be located on the second stage 42 and the slider 62 may be located on the first stage 41.

[0026] The movement stage 4 has been described above, but the configuration of the movement stage 4 is not particularly limited. For example, either the first stage 41 or the second stage 42 may be omitted. Furthermore, a third stage that moves in the Z-axis direction relative to the second stage 42, a fourth stage that rotates around the Z-axis relative to the second stage 42, etc. may be added, or these may be replaced with the first and second stages as appropriate. In other words, it may be a configuration having at least one of the first to fourth stages. Also, the first piezoelectric drive device 5 is not particularly limited as long as it can move the slider 52 in the X-axis direction by the vibration of the piezoelectric actuator 51. Similarly, the second piezoelectric drive device 6 is not particularly limited as long as it can move the slider 62 in the Y-axis direction by the vibration of the piezoelectric actuator 61. Furthermore, the configuration of the piezoelectric actuators 51 and 61 is not particularly limited as long as they can perform similar functions.

[0027] Next, the print head 8 will be described. As shown in Figure 3, the print head 8 is located in the second stage 42. The print head 8 is a piezo-driven inkjet head and has a plurality of nozzles 81 formed on its tip surface. Each nozzle is connected to a separate ink chamber, and each ink chamber has a piezoelectric element for vibrating its outer wall. An ink ejection voltage is applied to the piezoelectric element at a predetermined timing for each ink chamber, causing the piezoelectric element to vibrate, which in turn ejects ink I from the corresponding nozzle 81. Therefore, by moving the print head 8 along the printing trajectory Q and ejecting ink I from each nozzle 81 at a predetermined timing to hit the target object W, a predetermined pattern can be printed on the target object W.

[0028] However, the configuration of the print head 8 is not particularly limited. For example, a configuration capable of multi-color printing may be made by arranging multiple print heads 8 in a row along the print trajectory Q. Specifically, for example, full-color printing may be made by arranging a print head 8 that ejects black ink I, a print head 8 that ejects cyan ink I, a print head 8 that ejects magenta ink I, and a print head 8 that ejects yellow ink I along the print trajectory Q. Furthermore, the print head 8 is not limited to a piezo-driven inkjet head. For example, it may be an inkjet head of the thermal type that utilizes the film boiling phenomenon of ink I, a bubble ejection type that generates bubbles in the ink I by applying heat and ejects the ink I, or an electrostatic actuator type that ejects ink I by displacing and vibrating a diaphragm with electrostatic force.

[0029] Next, the inertial sensor 7 will be described. The inertial sensor 7 is placed on the print head 8 and detects vibrations of the print head 8. Note that "vibration" refers to unwanted displacements other than the displacement along the print trajectory Q of the print head 8. The inertial sensor 7 is not particularly limited as long as it can detect vibrations, but for example, a three-axis angular velocity sensor that detects angular velocity around three mutually orthogonal axes can be used.

[0030] Next, the control device 9 will be described. The control device 9 is, for example, composed of a computer and includes a processor that processes information, a memory that is communicatively connected to the processor, and an external interface. The memory stores programs that can be executed by the processor, and the processor reads and executes the programs stored in the memory. In this embodiment, the control device 9 is located inside the base 31, but the location of the control device 9 is not limited to this, and it may be located outside the base 31 and connected to the robot 2 by wire or wireless. Furthermore, the control device 9 may be composed of multiple devices.

[0031] As shown in Figure 1, such a control device 9 includes a robot arm control unit 91 that controls the driving of the robot arm 32, a moving stage control unit 92 that controls the driving of the moving stage 4, and a print head control unit 93 that controls the driving of the print head 8.

[0032] The robot arm control unit 91 receives commands from a host computer (not shown) for the first to sixth arm drive mechanisms and controls the motor drive by feeding back the encoder output to these commands. Through this feedback control, the robot arm control unit 91 moves the first to sixth arms 321 to 326 independently, bringing the end effector of the robot arm 32 to a predetermined position and orientation.

[0033] During printing, the moving stage control unit 92 detects vibrations of the print head 8 based on the output of the inertial sensor 7 and controls the drive of the moving stage 4 so that the detected vibrations are canceled.

[0034] The print head control unit 93 receives commands from a host computer (not shown) for each piezoelectric element located in each ink chamber and controls its drive according to these commands. Through this control, the print head control unit 93 causes each piezoelectric element to vibrate independently, ejecting ink I from the nozzle 81 of the corresponding ink chamber at a predetermined timing.

[0035] During the printing operation on the target object W, the control device 9 moves the print head 8 along a preset printing trajectory Q by controlling the drive of the robot arm 32 via the robot arm control unit 91, while simultaneously ejecting ink I from each nozzle 81 at predetermined timings via the print head control unit 93. As a result, the ink I lands on predetermined locations on the target object W, printing a predetermined pattern onto the target object W. Furthermore, the control device 9, via the moving stage control unit 92, detects vibrations of the print head 8 based on the output of the inertia sensor 7 while the print head 8 is moving along the printing trajectory Q, and controls the drive of the moving stage 4 so that the detected vibrations are canceled. Specifically, it controls the drive of the first and second piezoelectric drive devices 5 and 6 so that vibrations with the opposite phase to the detected vibrations are applied to the print head 8. This suppresses vibrations of the print head 8 during printing, enabling higher quality printing.

[0036] However, the method of printing is not particularly limited. For example, the print head 8 may be moved along the printing trajectory Q by driving only the moving stage 4 while the robot arm 32 is stopped, and ink I may be ejected from the print head 8. The moving stage 4 is small and lightweight because it is driven by the first and second piezoelectric drive units 5 and 6, and the amount of movement and speed of movement of the first and second stages 41 and 42 can be controlled finely and with high precision. Furthermore, because it has low inertia, the direction of movement can be changed quickly. Therefore, vibration of the print head 8 can be effectively suppressed compared to when the print head 8 is moved along the printing trajectory Q by driving the robot arm 32. In this case, however, because the range of motion of the moving stage 4 is small, the print head 8 may not be able to move the entire range of the printing trajectory Q with a single drive of the moving stage 4. In such cases, for example, the robot arm 32 can be driven to position the print head 8 in a predetermined location and orientation, and then, with the robot arm 32 stopped, only the moving stage 4 can be driven to move the print head 8 along the print trajectory Q. This process can be repeated multiple times to move the print head 8 along the print trajectory Q.

[0037] The configuration of the robot system 10 has been described above. Next, the operation of the first and second piezoelectric drive devices 5 and 6 in the robot system 10 will be described. Since the operation of the first and second piezoelectric drive devices 5 and 6 is similar to that of the first piezoelectric drive device 5, the operation of the first piezoelectric drive device 5 will be described as representative, and the operation of the second piezoelectric drive device 6 will be omitted.

[0038] When the piezoelectric actuator 51 is not driven, the contact 514 is pressed against the slider 52. As a result, the frictional force (holding force) generated between them holds the slider 52 in place. In other words, in this state, the first stage 41 is braked and stopped.

[0039] In this stopped state, when the moving stage control unit 92 applies the drive voltages V1, V2, and V3 shown in Figure 7 to the first and second piezoelectric elements P11, P12, and P21-P24, as shown in Figure 8, the vibrating part 511 vibrates by expanding and contracting in the Y-axis direction and by bending in an inverted S-shape in the X-axis direction. These vibrations are combined, causing the contactor 514 to move in an elliptical motion, tracing an elliptical orbit counterclockwise as indicated by the arrow. As a result, the slider 52 is fed out and the first stage 41 moves linearly toward the positive side in the X-axis direction.

[0040] Conversely, when the moving stage control unit 92 applies the drive voltages V1, V2, and V3 shown in Figure 9 to the first and second piezoelectric elements P11, P12, and P21-P24, as shown in Figure 10, the vibrating section 511 vibrates by expanding and contracting in the Y-axis direction while bending in an S-shape in the X-axis direction. These vibrations are combined, causing the contactor 514 to move in an elliptical motion, tracing an elliptical orbit clockwise as indicated by the arrow. As a result, the slider 52 is fed out and the first stage 41 moves linearly to the negative side in the X-axis direction.

[0041] The drive frequencies fd, which are the frequencies of the respective drive voltages V1, V2, and V3, are set to a frequency f2 that is slightly higher than the resonant frequency fr of the piezoelectric actuator 51, or more specifically, a frequency f2 that is slightly higher than the resonant frequency fr. This allows the piezoelectric actuator 51 to be driven resonantly, enabling efficient movement of the slider 52.

[0042] Furthermore, the movement speed of the slider 52 can be changed by changing the magnitude of each drive voltage V1, V2, and V3. Specifically, the larger the drive voltages V1, V2, and V3, the larger the elliptical motion of the contact 514, and the higher the movement speed of the slider 52. Conversely, the smaller the drive voltages V1, V2, and V3, the smaller the elliptical motion of the contact 514, and the lower the movement speed of the slider 52. However, there are no particular limitations on how the movement speed of the slider 52 can be changed. For example, the movement speed of the slider 52 can be changed by changing the drive frequency fd, which is the frequency of each drive voltage V1, V2, and V3. Specifically, the closer the drive frequency fd is to the resonant frequency fr of the piezoelectric actuator 51, the larger the elliptical motion of the contact 514 becomes, and the higher the movement speed of the slider 52. Conversely, the further the drive frequency fd is from the resonant frequency fr, the smaller the elliptical motion of the contact 514 becomes, and the lower the movement speed of the slider 52.

[0043] In the first piezoelectric drive device 5, the contact 514 is pressed against the slider 52, resulting in a low Q value for the piezoelectric actuator 51. Therefore, even if the drive voltages V1, V2, and V3 at the drive frequency fd (=frequency f2) are suddenly applied when starting the piezoelectric actuator 51, there is a risk that the piezoelectric actuator 51 will not oscillate and will not start.

[0044] Therefore, in the present embodiment, as shown in FIG. 11, driving is started by setting the driving frequency fd to frequency f1 which is higher than frequency f2 (a frequency farther from the resonance frequency fr than frequency f2). Then, "down-sweep control" is performed, in which the driving frequency fd is gradually down-swept from frequency f1 at a predetermined sweep rate to approach the resonance frequency fr, and the down-sweep control is terminated when the driving frequency fd reaches a predetermined frequency f2 (fr<f2<f1). According to this method, since the resonance of the piezoelectric actuator 51 can be gradually grown, the piezoelectric actuator 51 can be started more reliably and stably.

[0045] After the down-sweep control is completed, "voltage speed control" is executed to control the moving speed of the slider 52 by controlling the magnitudes of driving voltages V1, V2 and V3 while maintaining the driving frequency fd=f2. As described above, instead of the voltage speed control, "frequency speed control" for controlling the moving speed of the slider 52 by controlling the driving frequency fd may be executed.

[0046] The operation of the first piezoelectric driving device 5 has been described above. The same applies to the operation of the second piezoelectric driving device 5. Next, a control method for the robot system 10 will be described based on a printing operation on an object W.

[0047] As described above, for the first and second piezoelectric driving devices 5 and 6, starting driving by down-sweep control can stably start the piezoelectric actuators 51 and 61, but on the other hand, the following problem occurs. As shown in FIG. 12, during down-sweep control, along with the growth of resonance, the holding force (the aforementioned frictional force), which is the force with which the piezoelectric actuators 51 and 61 hold the sliders 52 and 62, decreases over time, and conversely, the thrust, which is the force with which the piezoelectric actuators 51 and 61 push out the sliders 52 and 62, increases over time. Therefore, as indicated by hatching in FIG. 12, a state where both the holding force and the thrust are insufficient occurs during the down-sweep control.

[0048] When both holding force and thrust are insufficient, sliders 52 and 62 become unstable and susceptible to external forces. For example, if the X-axis direction of movement of slider 52 includes a vertical component, especially if it coincides with the vertical direction, during downsweep control, the piezoelectric actuator 51 may not be able to hold slider 52, and gravity may cause slider 52 to shift downward in the vertical direction. Similarly, if the Y-axis direction of movement of slider 62 includes a vertical component, especially if it coincides with the vertical direction, during downsweep control, the piezoelectric actuator 61 may not be able to hold slider 62, and gravity may cause slider 62 to shift downward in the vertical direction. Such misalignment of sliders 52 and 62 manifests as misalignment of the print head 8 relative to the print trajectory Q. Therefore, if printing is started with misalignment of sliders 52 and 62, the print head 8 will deviate from the print trajectory Q, resulting in a decrease in print quality.

[0049] Therefore, in this embodiment, the positions of sliders 52 and 62 are corrected before starting the printing operation, and the printing operation is started after the position correction is completed. By using this method, deviation of the print head 8 from the printing trajectory Q is suppressed, enabling high-quality printing. The control method will be described in detail below.

[0050] The control method for the robot system 10, as shown in Figure 13, includes a work preparation step S1 in which the print head 8 is positioned and positioned to a predetermined location; a drive start step S2 in which the drive of the moving stage 4 is started; and a work start step S3 in which position correction control of the moving stage 4 is started, and after the position of the moving stage 4 is corrected by the position correction control, the drive of the moving stage 4 is started while maintaining the position correction control.

[0051] In the preparation step S1, first, in step S11, the control device 9 drives the robot arm 32 to position the print head 8 in a predetermined position and orientation. Specifically, the print head 8 is positioned in a predetermined orientation at the starting position Qs of the print trajectory Q. As shown in Figure 14, in this embodiment, the print head 8 faces the object W, and the X-axis is aligned vertically and the Y-axis is aligned horizontally.

[0052] In the drive start step S2, first, as step S21, the control device 9 starts driving the piezoelectric actuators 51 and 61 using the downsweep control described above. In the downsweep control, the drive voltage V1 is applied only to the first piezoelectric elements P11 and P12 for stretching vibration, and the drive voltages V2 and V3 are not applied to the second piezoelectric elements P21 to P24 for bending vibration. This method effectively suppresses the movement of the sliders 52 and 62 during the downsweep control.

[0053] Next, in step S22, the control device 9 determines whether the downsweep control has ended and whether the piezoelectric actuators 51 and 61 have been activated. "Activated" means that sufficient resonance has grown and the sliders 52 and 62 can be moved stably under desired conditions. While there are no particular limitations on the method for determining activation, in this embodiment, it is determined based on the drive frequency fd. Specifically, if the drive frequency fd reaches the target frequency f2, it is determined that the piezoelectric actuators 51 and 61 have been activated; if the drive frequency fd has not reached frequency f2, it is determined that the piezoelectric actuator 51 has not been activated. Alternatively, for example, activation may be determined when a predetermined time has elapsed since the start of the downsweep control.

[0054] During the drive initiation step S2 described above, the force with which the piezoelectric actuators 51 and 61 hold the sliders 52 and 62 decreases, and there is a risk that the sliders 52 and 62 may be unintentionally displaced due to external forces such as gravity. As shown in Figure 14, in this embodiment, the X-axis is aligned vertically and the Y-axis is aligned horizontally. Therefore, the slider 52 is particularly prone to being displaced downward in the vertical direction due to the influence of gravity.

[0055] In the work commencement step S3, first, as step S31, the control device 9 starts position correction control of sliders 52 and 62. Position correction control is a control that moves slider 52 in the X-axis direction by driving piezoelectric actuator 51 and matches the actual position of slider 52 detected based on the output of position detection device 53 to the target position. Similarly, it is a control that moves slider 62 in the Y-axis direction by driving piezoelectric actuator 61 and matches the actual position of slider 62 detected based on the output of position detection device 63 to the target position. Next, as step S32, the control device 9 determines whether the pre-work position correction has been completed. There is no particular limit to the method for determining whether the position correction has been completed, but in this embodiment, if the actual positions of sliders 52 and 62 each coincide with the target position, it is determined that the position correction has been completed, and if at least one does not coincide, it is determined that the position correction has not been completed. Note that "coincidence" includes not only cases where both coincide perfectly, but also cases where the deviation between them is within a preset allowable range.

[0056] If the control device 9 determines in step S32 that the position correction control is complete, in step S33, based on a command from a host computer (not shown), it moves the robot arm 32 to move the print head 8 along the print trajectory Q, and prints on the target object W by ejecting ink I from each nozzle 81 at predetermined timings. At this time, the control device 9 continues the position correction control started in step S31, detects vibrations of the print head 8 based on the output of the inertial sensor 7, and controls the drive of the moving stage 4, i.e., the first and second piezoelectric drive devices 5 and 6, so that the detected vibrations are canceled.

[0057] Then, in step S34, the control device 9 determines whether printing is complete, and if printing is complete, it terminates the printing operation. With this method, since the printing operation is performed after the position correction of sliders 52 and 62 is completed, deviation of the print head 8 from the print trajectory Q can be effectively suppressed. As a result, high print quality can be achieved.

[0058] The robot system 10 has been described above. As previously mentioned, the control method for such a robot system 10 is a control method for a drive system comprising a piezoelectric actuator 51 as a vibrating body and a slider 52 as a driven body that moves in the X-axis direction, which is a first direction relative to the piezoelectric actuator 51, by vibrating the piezoelectric actuator 51, and a first piezoelectric drive device 5 as a piezoelectric drive device that receives an external force in the X-axis direction on the piezoelectric actuator 51 or the slider 52, and includes a drive start step S2 in which the vibration of the piezoelectric actuator 51 is started, and a work start step S3 in which position correction control is started to correct the position of the slider 52, and after the position of the slider 52 is corrected to the target position by the position correction control, the movement of the slider 52 is started while maintaining the position correction control.

[0059] Furthermore, the control method for such a robot system 10 is a control method for a drive system comprising a piezoelectric actuator 61 as a vibrating body and a slider 62 as a driven body that moves in the Y-axis direction, which is a first direction relative to the piezoelectric actuator 61, by vibrating the piezoelectric actuator 61, and a second piezoelectric drive device 6 as a piezoelectric drive device that receives an external force in the Y-axis direction on the piezoelectric actuator 61 or the slider 62, and includes a drive start step S2 in which the vibration of the piezoelectric actuator 61 is started, and a work start step S3 in which position correction control is started to correct the position of the slider 62, and after the position of the slider 62 is corrected to the target position by the position correction control, the movement of the slider 62 is started while maintaining the position correction control.

[0060] With this control method, the sliders 52 and 62 are moved (printing operation) only after their position correction is complete, effectively suppressing misalignment of the sliders 52 and 62. As a result, the robot system 10 is capable of highly accurate operation.

[0061] In this embodiment, as described above, the piezoelectric actuator 51 is located on the base 40 and the slider 52 is located on the first stage 41 which is displaced relative to the base 40, so the slider 52 is subjected to the external force. Conversely, if the piezoelectric actuator 51 is located on the first stage 41 and the slider 52 is located on the base 40, then the piezoelectric actuator 51 is subjected to the external force. Similarly, if the piezoelectric actuator 61 is located on the first stage 41 and the slider 62 is located on the second stage 42 which is displaced relative to the first stage 41, then the slider 62 is subjected to the external force. Conversely, if the piezoelectric actuator 61 is located on the second stage 42 and the slider 62 is located on the first stage 41, then the piezoelectric actuator 61 is subjected to the external force.

[0062] Furthermore, as mentioned above, the X-axis direction includes a vertical component. In particular, in this embodiment, the X-axis direction coincides with the vertical direction. With this configuration, the slider 52 is easily displaced by gravity during the drive start step S2. If the Y-axis direction includes a vertical component, the slider 62 is easily displaced by gravity during the drive start step S2. Also, if both the X-axis direction and the Y-axis direction each include a vertical component, both sliders 52 and 62 are easily displaced by gravity during the drive start step S2. Therefore, the effect of the control method in this embodiment becomes more pronounced.

[0063] Furthermore, as mentioned above, the first piezoelectric drive unit 5 has a position detection device 53 that detects the position of the slider 52, and performs position correction control based on the detection result of the position detection device 53. The same applies to the second piezoelectric drive unit 6. With this method, position correction control can be performed with high accuracy.

[0064] As mentioned above, the piezoelectric actuator 51 includes a vibrating section 511, first piezoelectric elements P11 and P12 that cause the vibrating section 511 to expand and contract, and second piezoelectric elements P21 to P24 that cause the vibrating section 511 to contract. In the drive start step S2, the first piezoelectric elements P11 and P12 are driven, and in the work start step S3, the first piezoelectric elements P11 and P12 and the second piezoelectric elements P21 to P24 are driven. The same applies to the piezoelectric actuator 61. With this method, the feeding of the slider 52 by the piezoelectric actuator 51 can be suppressed in the drive start step S2.

[0065] As mentioned above, the robot system 10 comprises a moving stage 4 having a first piezoelectric drive device 5, a first stage 41 which is displaced by the drive of the first piezoelectric drive device 5, a second piezoelectric drive device 6, and a second stage 42 which is displaced by the drive of the second piezoelectric drive device 6, and a robot arm 32 which holds the moving stage 4. With this configuration, the first stage 41 and the second stage 42 can be driven with high precision.

[0066] Furthermore, as mentioned above, the robot system 10 has a print head 8 held on the moving stage 4, and prints on the object W by ejecting ink I from the print head 8 toward the object W while the slider 52 is moving. With this configuration, the robot system 10 can print on the object W.

[0067] Furthermore, as described above, the robot system 10 as the drive system 1 includes a piezoelectric actuator 51 as a vibrating body, a slider 52 as a driven body that moves in the X-axis direction, which is a first direction relative to the piezoelectric actuator 51, by vibrating the piezoelectric actuator 51, and a control device 9 that controls the driving of the piezoelectric actuator 51. The drive system includes a first piezoelectric drive device 5 as a piezoelectric drive device that receives an external force in the X-axis direction on the piezoelectric actuator 51 or the slider 52. After the control device 9 starts vibrating the piezoelectric actuator 51, it starts position correction control to correct the position of the slider 52, corrects the position of the slider 52 to the target position by the position correction control, and then starts moving the slider 52 while maintaining the position correction control.

[0068] Furthermore, as described above, such a robot system 10 includes a piezoelectric actuator 61 as a vibrating body, a slider 62 as a driven body that moves in the Y-axis direction, which is a first direction relative to the piezoelectric actuator 61, by vibrating the piezoelectric actuator 61, and a control device 9 that controls the driving of the piezoelectric actuator 61. The system also includes a second piezoelectric drive device 6 as a piezoelectric drive device that receives an external force in the X-axis direction on the piezoelectric actuator 61 or the slider 62. The control device 9 starts position correction control to correct the position of the slider 62 after starting vibration of the piezoelectric actuator 61, corrects the position of the slider 62 to the target position by position correction control, and then starts moving the slider 62 while maintaining position correction control.

[0069] With this configuration, the sliders 52 and 62 are moved (printing) only after their position correction is complete, effectively suppressing any misalignment of the sliders 52 and 62. This results in a robot system 10 capable of highly accurate operation.

[0070] As mentioned above, the robot system 10 is a robot system comprising a moving stage 4 which includes a first piezoelectric drive device 5 and a first stage 41 which is displaced by the drive of the first piezoelectric drive device 5, a second piezoelectric drive device 6 and a second stage 42 which is displaced by the drive of the second piezoelectric drive device 6, and a robot arm 32 which holds the moving stage 4. With this configuration, the first stage 41 and the second stage 42 can be driven with high precision.

[0071] <Second Embodiment> Figure 15 is a diagram illustrating the control method of the robot system according to the second embodiment.

[0072] This embodiment is the same as the first embodiment described above, except that the control method of the robot system 10 is different. In the following description, this embodiment will be described mainly in terms of the differences from the first embodiment described above, and similar matters will be omitted from the description. Also, in the figures of this embodiment, the same reference numerals are used for components that are the same as in the previously described embodiment.

[0073] In the first embodiment described above, high-quality printing is achieved by correcting for positional misalignment of sliders 52 and 62 due to gravity before starting the printing process. In contrast, this embodiment is characterized by performing the printing process with sliders 52 and 62 in a position unaffected by gravity. With this configuration, high-quality printing can be achieved, similar to the first embodiment described above.

[0074] In the control method of the robot system 10 of this embodiment, the control device 9 moves the robot arm 32 to move the moving stage 4 in a direction perpendicular to the external force such as gravity. Note that "perpendicular" includes cases where the moving stage 5 is slightly deviated from the external force by an angle of, for example, within 5°. As an example, as shown in Figure 15, the control device 9 moves the robot arm 32 to set the posture of the moving stage 4 so that the X-axis and Y-axis directions are aligned with the horizontal direction. This substantially prevents the displacement of the sliders 52 and 62 due to gravity, as in the first embodiment described above. Note that "the X-axis direction (Y-axis direction) is aligned with the horizontal direction" includes not only cases where the X-axis direction (Y-axis direction) coincides with the horizontal direction, but also cases where the X-axis direction (Y-axis direction) is slightly deviated from the horizontal direction by an angle of, for example, within 5°.

[0075] Next, the control device 9 moves the robot arm 32 to move the print head 8 along the print trajectory Q while maintaining the posture of the moving stage 4, and prints on the target object W by ejecting ink I from each nozzle 81 at predetermined timings. At this time, the control device 9 also detects vibrations of the print head 8 based on the output of the inertial sensor 7 and controls the drive of the moving stage 4, that is, the first and second piezoelectric drive devices 5 and 6, so that the detected vibrations are canceled.

[0076] With this control method, the orientation of the moving stage 4 is maintained in a position where the sliders 52 and 62 do not substantially shift due to gravity. Therefore, the displacement of the sliders 52 and 62 due to gravity, as in the first embodiment described above, can be effectively suppressed. Consequently, high-quality printing becomes possible.

[0077] As described above, the control method for the robot system 10 of this embodiment is a control method for a robot system comprising: first and second piezoelectric drive devices 5 and 6 as piezoelectric drive devices, which include piezoelectric actuators 51 and 61 as vibrating bodies and sliders 52 and 62 as driven bodies that move in the X and Y axis directions, which are first directions relative to the piezoelectric actuators 51 and 61 by vibrating the piezoelectric actuators 51 and 61; a moving stage 4 comprising first and second stages 41 and 42 as stages that are displaced by the driving of the first and second piezoelectric drive devices 5 and 6; and a robot arm 32 that holds the moving stage 4. The method involves moving the moving stage 4 so that the X and Y axis directions are perpendicular to the external force, and then starting the movement of the sliders 52 and 62. With such a control method, displacement of the sliders 52 and 62 can be effectively suppressed. As a result, the robot system 10 is capable of driving with high precision.

[0078] Furthermore, the control method for the robot system 10 includes a horizontal component in the X-axis and Y-axis directions of the sliders 52 and 62 of the moving stage 4. With this configuration, the moving stage 4 assumes a posture in which the sliders 52 and 62 are less likely to be displaced by gravity before moving the sliders 52 and 62. Therefore, the effect of the control method of this embodiment becomes more pronounced.

[0079] As mentioned above, the robot system 10 includes first and second piezoelectric drive devices 5 and 6, which are piezoelectric drive devices equipped with piezoelectric actuators 51 and 61 as vibrating bodies and sliders 52 and 62 as driven bodies that move in the X and Y axis directions, which are first directions relative to the piezoelectric actuators 51 and 61 by vibrating the piezoelectric actuators 51 and 61; a moving stage 4 equipped with first and second stages 41 and 42 as stages that are displaced by the driving of the first and second piezoelectric drive devices 5 and 6; and a robot arm 32 that holds the moving stage 4. The robot system 10 starts moving the sliders 52 and 62 after moving the moving stage 4 so that the X and Y axis directions are perpendicular to the external force. With this configuration, displacement of the sliders 52 and 62 can be effectively suppressed. As a result, the robot system 10 is capable of driving with high precision.

[0080] Furthermore, the X-axis and Y-axis directions of the sliders 52 and 62 of the robot system 10 include a horizontal component. With this configuration, the moving stage 4 moves the sliders 52 and 62 after it has assumed a posture in which the sliders 52 and 62 are less likely to be displaced by gravity. Therefore, the effect of the control method of this embodiment becomes more pronounced.

[0081] The second embodiment described above can also achieve the same effects as the first embodiment described above.

[0082] The control method for the drive system, the control method for the robot system, the drive system, and the robot system of the present invention have been described above based on the illustrated embodiments. However, the present invention is not limited thereto, and the configurations and processes of each part can be replaced with any configurations and processes having similar functions. Furthermore, other arbitrary configurations and processes may be added to the present invention. In addition, each embodiment may be combined as appropriate.

[0083] For example, in the embodiment described above, the drive system is applied to a robot system, but the drive system is not particularly limited as long as it has a piezoelectric drive device. [Explanation of Symbols]

[0084] 1…Drive system, 2…Robot, 3…Robot body, 4…Moving stage, 5…First piezoelectric drive unit, 6…Second piezoelectric drive unit, 7…Inertial sensor, 8…Print head, 9…Control device, 10…Robot system, 31…Base, 32…Robot arm, 40…Base, 41…First stage, 42…Second stage, 51…Piezoelectric actuator, 52…Slider, 53…Position detection device, 54…Biasing member, 61…Piezoelectric actuator, 62… Slider, 63...Position detection device, 64...Biasing member, 81...Nozzle, 91...Robot arm control unit, 92...Moving stage control unit, 93...Print head control unit, 321...First arm, 322...Second arm, 323...Third arm, 324...Fourth arm, 325...Fifth arm, 326...Sixth arm, 331...First arm drive mechanism, 332...Second arm drive mechanism, 333...Third arm drive mechanism, 334...Fourth arm drive mechanism, 335...Fifth arm 336…Sixth arm drive mechanism, 511…Vibrating part, 512…Support part, 513…Beam part, 514…Contactor, 531…Scale, 532…Optical element, 532a…Light-emitting element, 532b…Light-receiving element, 541…Base part, 542…Actuator holding part, 543…Leaf spring, E…Encoder, I…Ink, M…Motor, P11…First piezoelectric element, P12…First piezoelectric element, P21…Second piezoelectric element, P22…Second piezoelectric element, P23…Second piezoelectric P24...Second piezoelectric element, Q...Printed track, Qs...Starting position, S1...Work preparation step, S11...Step, S2...Drive start step, S21...Step, S22...Step, S3...Work start step, S31...Step, S32...Step, S33...Step, S34...Step, T...Gear reducer, V1...Drive voltage, V2...Drive voltage, V3...Drive voltage, W...Object, f1...Frequency, f2...Frequency, fd...Drive frequency, fr...Resonant frequency

Claims

1. A control method for a drive system comprising a piezoelectric drive device having a vibrating body and a driven body that moves in a first direction relative to the vibrating body by vibrating the vibrating body, wherein the vibrating body or the driven body receives an external force in the first direction, A drive start step in which the vibration of the vibrating body is initiated, A control method for a drive system, characterized by including a work start step of starting position correction control to correct the position of the driven body, and after the position of the driven body has been corrected to a target position by the position correction control, starting the movement of the driven body while maintaining the position correction control.

2. The control method for a drive system according to claim 1, wherein the first direction includes a vertical component.

3. The piezoelectric drive device has a position detection device for detecting the position, A control method for a drive system according to claim 1, which performs the position correction control based on the detection result of the position detection device.

4. The vibrating body comprises a vibrating part and A first piezoelectric element that causes the vibrating part to expand and contract, It has a second piezoelectric element that causes the vibrating part to bend and vibrate, In the drive start step, the first piezoelectric element is driven, The control method for the drive system according to claim 1, wherein the first piezoelectric element and the second piezoelectric element are driven in the aforementioned work commencement step.

5. The drive system comprises a movable stage comprising a piezoelectric drive device and a stage that is displaced by the drive of the piezoelectric drive device, A control method for a drive system according to claim 1, comprising a robot arm that holds the aforementioned moving stage.

6. The robot system has a print head held on the moving stage, A control method for a drive system according to claim 5, wherein printing is performed on an object by ejecting ink from the print head toward the object while the driven object is moving.

7. A moving stage comprising a piezoelectric drive device having a vibrating body and a driven body that moves in a first direction relative to the vibrating body by vibrating the vibrating body, and a stage that is displaced by the drive of the piezoelectric drive device, A control method for a robot system comprising a robot arm that holds the aforementioned moving stage, A method for controlling a robot system, characterized in that the moving stage is moved so that the first direction is perpendicular to the external force, and then the movement of the driven body is started.

8. The control method for a drive system according to claim 7, wherein the first direction includes a horizontal component.

9. A drive system comprising a piezoelectric drive device having a vibrating body, a driven body that moves in a first direction relative to the vibrating body by vibrating the vibrating body, and a control device that controls the driving of the vibrating body, wherein the vibrating body or the driven body receives an external force in the first direction, The control device starts the vibration of the vibrating body, then starts position correction control to correct the position of the driven body, and after correcting the position of the driven body to the target position by the position correction control, starts the movement of the driven body while maintaining the position correction control.

10. The drive system comprises a movable stage comprising a piezoelectric drive device and a stage that is displaced by the drive of the piezoelectric drive device, The drive system according to claim 9, comprising a robot arm that holds the aforementioned moving stage.

11. A moving stage comprising a piezoelectric drive device having a vibrating body and a driven body that moves in a first direction relative to the vibrating body by vibrating the vibrating body, and a stage that is displaced by the drive of the piezoelectric drive device, The robot arm holding the moving stage comprises A robot system characterized in that the movement stage is moved so that the first direction is perpendicular to the external force, and then the movement of the driven body is started.

12. The robot system according to claim 11, wherein the first direction includes a horizontal component.

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