Control method of piezoelectric drive device, control method of robot, and robot

Abstract

Provided are a control method of a piezoelectric drive device, a control method of a robot, and a robot, which can minimize the influence of external force and accurately control minute movement. A control method of a piezoelectric drive device, which has a vibration section provided with a piezoelectric element and a transmission section that transmits vibration of the vibration section to a driven body, makes the vibration section vibrate and the transmission section perform elliptical motion by combining longitudinal vibration and bending vibration to make the piezoelectric element vibrate, and moves the driven body by the elliptical motion, in which the control method of the piezoelectric drive device switches a drive algorithm of the piezoelectric drive device between a first drive mode in which a feed amplitude, which is an amplitude of the bending vibration, is fixed, and a second drive mode in which the feed amplitude and a split amplitude, which is an amplitude of the longitudinal vibration, are changed, according to external force received by the driven body.

Description

Technical Field

[0001] This invention relates to a control method for a piezoelectric drive device, a control method for a robot, and a robot. Background Technology

[0002] For example, Patent Document 1 describes a driving method for an ultrasonic actuator (piezoelectric drive device) that generates longitudinal and bending vibrations to induce approximately elliptical vibrations in a friction contact element, and uses the frictional force of these elliptical vibrations as a thrust to move a driven body. The driving method for this ultrasonic actuator described in Patent Document 1 is characterized in that, for the purpose of suppressing the falling of the driven body due to gravity, bending vibration is excited after longitudinal vibration is excited during startup.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2008-172853

[0004] However, the ultrasonic actuator driving method described in Patent Document 1 has the following problem: although it may be possible to suppress the falling of the driven body caused by the influence of gravity, it is difficult to control the small amount of movement of the driven body depending on the magnitude or direction of the external force applied to the driven body, such as gravity. Summary of the Invention

[0005] In the control method of the piezoelectric drive device of the present invention, the piezoelectric drive device includes: a vibration section having a piezoelectric element; and a transmission section that transmits the vibration of the vibration section to a driven body. The piezoelectric drive device causes the vibration section to vibrate and the transmission section to perform elliptical motion by energizing the piezoelectric element, and moves the driven body by the elliptical motion. In the control method of the piezoelectric drive device, the drive algorithm of the piezoelectric drive device is switched according to a first drive mode and a second drive mode in response to the external force on the driven body. The first drive mode is a mode in which the feed amplitude, which is the amplitude of the bending vibration, is fixed while the separate amplitude, which is the amplitude of the longitudinal vibration, is varied. The second drive mode is a mode in which the feed amplitude and the separate amplitude are varied together.

[0006] In the robot control method of the present invention, the robot has a piezoelectric drive device and a movable part. The piezoelectric drive device has: a vibration part having a piezoelectric element; and a transmission part that transmits the vibration of the vibration part to the driven body. The piezoelectric drive device combines longitudinal vibration and bending vibration by energizing the piezoelectric element to make the vibration part vibrate and the transmission part perform elliptical motion, and the driven body is moved by the elliptical motion. The movable part is driven by the piezoelectric drive device. In the robot control method, the drive algorithm of the piezoelectric drive device is switched according to a first drive mode and a second drive mode in response to the external force on the driven body. The first drive mode is a mode in which the feed amplitude, which is the amplitude of the bending vibration, is fixed while the separate amplitude, which is the amplitude of the longitudinal vibration, is varied. The second drive mode is a mode in which the feed amplitude and the separate amplitude are varied together.

[0007] The robot of the present invention has a piezoelectric drive device, a movable part, and a control device. The piezoelectric drive device has: a vibration part having a piezoelectric element; and a transmission part that transmits the vibration of the vibration part to a driven body. The piezoelectric drive device combines longitudinal vibration and bending vibration by energizing the piezoelectric element, causing the vibration part to vibrate and the transmission part to perform elliptical motion, and the driven body to move by the elliptical motion. The movable part is driven by the piezoelectric drive device, and the control device controls the drive of the piezoelectric drive device. Corresponding to the external force on the driven body, the control device switches the drive algorithm of the piezoelectric drive device according to a first drive mode and a second drive mode. The first drive mode is a mode in which the feed amplitude, which is the amplitude of the bending vibration, is fixed while the separate amplitude, which is the amplitude of the longitudinal vibration, varies. The second drive mode is a mode in which the feed amplitude and the separate amplitude vary together. Attached Figure Description

[0008] Figure 1 This is a diagram illustrating the robot according to the first embodiment.

[0009] Figure 2 This is a diagram showing a piezoelectric drive device.

[0010] Figure 3 This is a diagram showing a modified example of a piezoelectric drive device.

[0011] Figure 4 This is a diagram showing the drive signals of a piezoelectric actuator.

[0012] Figure 5 This is a diagram showing the vibration state of a piezoelectric actuator.

[0013] Figure 6This is a diagram showing the vibration state of a piezoelectric actuator.

[0014] Figure 7 This is a block diagram showing the configuration of the control device.

[0015] Figure 8 This is a diagram illustrating an example of a robot being affected by external forces.

[0016] Figure 9 This is a diagram illustrating an example of a robot being affected by external forces.

[0017] Figure 10 This is a diagram illustrating an example of a robot being affected by external forces.

[0018] Figure 11 This is a diagram showing the first driving mode.

[0019] Figure 12 This is a diagram illustrating the second driving mode.

[0020] Figure 13 This is a flowchart illustrating the control method of a piezoelectric drive device.

[0021] Figure 14 This is a diagram illustrating the robot involved in the second embodiment.

[0022] Figure 15 This is a diagram illustrating the robot according to the third embodiment.

[0023] Explanation of reference numerals in the attached figures

[0024] 1…robot, 2…first component, 3…second component, 4…control device, 41…drive signal generation unit, 42…drive algorithm selection unit, 43…movement amount detection unit, 44…movement direction detection unit, 5…piezoelectric drive device, 5A…piezoelectric drive device, 5B…piezoelectric drive device, 5C…piezoelectric drive device, 5D…piezoelectric drive device, 5E…piezoelectric drive device, 5F…piezoelectric drive device, 5G…piezoelectric drive device, 5H…piezoelectric drive device, 5I…piezoelectric drive device, 5J…piezoelectric drive device, 5K…piezoelectric drive device, 5L…piezoelectric drive device, 5M…piezoelectric drive device, 5 1…piezoelectric actuator, 51A…piezoelectric element, 51B…piezoelectric element, 51C…piezoelectric element, 51D…piezoelectric element, 51E…piezoelectric element, 51F…piezoelectric element, 51G…piezoelectric element, 511…vibrating part, 512…support part, 513…beam part, 514…transmission part, 52…rotor, 53…force application member, 531…holding part, 532…base, 533…spring assembly, 534…spring assembly, 54…encoder, 55…slider, 6…robot, 60…base, 61…first arm, 611…first direct motion part, 612…first rotating part, 62…second arm, 621…the… 622…Second rotating part, 63…Third arm, 631…Arm part, 632…Third rotating part, 64…Fourth arm, 641…Arm part, 642…Fourth rotating part, 65…End effector, 7…Robot, 70…Base, 71…First arm, 72…Second arm, 73…Third arm, 74…Fourth arm, 75…Fifth arm, 76…Sixth arm, 77…End effector (workbench), 771…Base part, 772…Table part, A1…Arrow, A2…Arrow, B1…Arrow, B2…Arrow, C…Wiring, D…Separation distance, Dm1…First drive mode, Dm2…Second drive mode Formula, F1…force, F2…force, F3…force, Jr…direct drive axis, Jr1…first direct drive axis, Jr2…second direct drive axis, Jθ…rotation axis, Jθ1…first rotation axis, Jθ2…second rotation axis, Jθ3…third rotation axis, Jθ4…fourth rotation axis, S1…step, S2…step, S3…step, S4…step, S5…step, S6…step, S7…step, S8…step, S9…step, S10…step, S11…step, S12…step, V1…drive signal, V2…drive signal, V3…drive signal, W…workpiece, W1…feed amplitude, W2…separation amplitude. Detailed Implementation

[0025] Hereinafter, the control method of the piezoelectric drive device, the control method of the robot, and the robot of the present invention will be described in detail based on the embodiments shown in the accompanying drawings.

[0026] <First Implementation>

[0027] Figure 1 This is a diagram illustrating the robot according to the first embodiment. Figure 2 This is a diagram showing a piezoelectric drive device. Figure 3 This is a diagram showing a modified example of a piezoelectric drive device. Figure 4 This is a diagram showing the drive signals of a piezoelectric actuator. Figure 5 and Figure 6 These are diagrams showing the vibration state of the piezoelectric actuator. Figure 7 This is a block diagram showing the configuration of the control device. Figures 8 to 10 These are diagrams illustrating an example of a robot being affected by external forces. Figure 11 This is a diagram showing the first driving mode. Figure 12 This is a diagram illustrating the second driving mode. Figure 13 This is a flowchart illustrating the control method of a piezoelectric drive device.

[0028] Figure 1 The robot 1 shown includes: a first component 2; a second component 3 as a movable part; a piezoelectric drive device 5 that causes the second component 3 to rotate relative to the first component 2 about a rotation axis Jθ; and a control device 4 that controls the drive of the piezoelectric drive device 5. It should be noted that the first component 2 and the second component 3 can be used as part of a robot arm as described in the second and third embodiments below.

[0029] like Figure 2 As shown, the piezoelectric drive device 5 includes: a piezoelectric actuator 51; a rotor 52, which, as a driven part, receives a driving force from the piezoelectric actuator 51 and rotates about a rotation axis Jθ; a force-applying member 53, which presses the piezoelectric actuator 51 against the rotor 52; and an encoder 54, which serves as a displacement detection sensor for detecting the displacement of the rotor 52. Furthermore, the piezoelectric actuator 51 is fixed to a first member 2 via the force-applying member 53, and the rotor 52 is fixed to a second member 3. Therefore, when the piezoelectric actuator 51 is driven, the second member 3, fixed to the rotor 52, rotates relative to the first member 2 about the rotation axis Jθ.

[0030] According to this piezoelectric drive device 5, the driving force from the piezoelectric actuator 51 is directly transmitted to the rotor 52. Therefore, there is no need for a relay mechanism to relay and transmit the driving force, which simplifies and miniaturizes the device. In addition, the decrease in movement accuracy caused by backlash or insufficient rigidity, which is a problem in relay mechanisms such as reducers, is essentially eliminated, resulting in a robot 1 with excellent driving accuracy. In particular, the rotary (rotary type) piezoelectric drive device 5 is suitable for rotating and moving the second component 3.

[0031] However, the piezoelectric drive device 5 is not limited to a rotary type; for example, it can also be... Figure 3This is a linear (direct-acting) type. In the illustrated piezoelectric drive device 5, a slider 55, which is a driven body capable of moving along the linear axis Jr, is used. The slider 55 is fixed to the second member 3. Therefore, when the piezoelectric actuator 51 is driven, the second member 3 fixed to the slider 55 moves relative to the first member 2 along the linear axis Jr.

[0032] Thus, the direct-acting (linear) piezoelectric drive device 5 becomes a device suitable for making the second component 3 move directly.

[0033] It should be noted that as a displacement detection sensor, there are no particular limitations if it can perform its function. For example, it can also use various inertial sensors such as accelerometers and angular velocity sensors, laser displacement gauges, image measuring instruments, etc.

[0034] like Figure 2 As shown, the piezoelectric actuator 51 has a vibrating part 511; a support part 512 that supports the vibrating part 511; a beam part 513 that connects the vibrating part 511 to the support part 512; and a transmission part 514 that is protruding and disposed at the front end of the vibrating part 511 to transmit the vibration of the vibrating part 511 to the rotor 52.

[0035] The vibrating part 511 is plate-shaped, forming a rectangle with the longitudinal direction of the paper as its long side. Furthermore, the vibrating part 511 includes piezoelectric elements 51A to 51F for driving and a detection piezoelectric element 51G for detecting the vibration of the vibrating part 511. Piezoelectric elements 51C and 51D are arranged in the center of the vibrating part 511 along its long side. Additionally, piezoelectric elements 51A and 51B are arranged on one side of piezoelectric elements 51C and 51D along their long side, and piezoelectric elements 51E and 51F are arranged on the other side. These piezoelectric elements 51A to 51F extend and retract along the long side of the vibrating part 511 when energized.

[0036] A detection piezoelectric element 51G is disposed between piezoelectric elements 51C and 51D. The piezoelectric element 51G is subjected to an external force corresponding to the vibration of the vibrating part 511, and outputs a detection signal corresponding to the external force. Therefore, the piezoelectric drive device 5 can detect the vibration state of the vibrating part 511 based on the detection signal output from the piezoelectric element 51G.

[0037] A transmission section 514 is provided at the front end of the vibrating section 511, and its front end contacts the rotor 52. Therefore, the vibration of the vibrating section 511 is transmitted to the rotor 52 via the transmission section 514. The support section 512 is the part that supports the vibrating section 511, and is U-shaped, surrounding both sides and the base end side of the vibrating section 511. In addition, the beam section 513 connects the vibrating section 511 to the support section 512 while allowing the vibrating section 511 to vibrate.

[0038] The force-applying member 53 applies force to the piezoelectric actuator 51 toward the rotor 52, pressing the transmission part 514 onto the rotor 52. Thus, the vibration of the vibration part 511 is efficiently transmitted to the rotor 52 via the transmission part 514. Furthermore, when the piezoelectric drive device 5 is not driven, applying brakes to the rotor 52 can prevent unexpected rotation of the rotor 52. The force-applying member 53 includes: a holding part 531, a holding support part 512; a base 532 fixed to the first member 2; and spring assemblies 533 and 534 connecting the holding part 531 to the base 532. This force-applying member 53 is fixed even when the spring assemblies 533 and 534 are deformed, and the restoring force of the spring assemblies 533 and 534 presses the piezoelectric actuator 51 onto the rotor 52.

[0039] This piezoelectric drive device 5 is driven as shown below. For example, when... Figure 4 When the driving signal V1 is applied to piezoelectric elements 51A and 51F, the driving signal V2 is applied to piezoelectric elements 51C and 51D, and the driving signal V3 is applied to piezoelectric elements 51B and 51E, as shown... Figure 5 As shown, the vibrating part 511 performs longitudinal vibration (expanding and contracting in the long side direction) and bending vibration (bending in the short side direction). These vibrations are combined, and the front end of the transmission part 514 performs an elliptical motion, tracing an elliptical orbit counterclockwise, as indicated by arrow A1. As a result, the rotor 52 is ejected and rotates clockwise, as indicated by arrow B1. Conversely, when switching drive signals V1 and V3, that is, when drive signal V1 is applied to piezoelectric elements 51B and 51E, and drive signal V3 is applied to piezoelectric elements 51A and 51F, as... Figure 6 As shown, the front end of the transmission unit 514 moves in an elliptical motion, which traces an elliptical orbit clockwise, as indicated by arrow A2, while the rotor 52 rotates counterclockwise, as indicated by arrow B2.

[0040] It should be noted that the longitudinal vibration and bending vibration of the vibration part 511, which forms the basis of the elliptical motion of the transmission part 514, are excited by applying a drive signal V2 to the piezoelectric elements 51C and 51D, and the bending vibration is excited by applying drive signals V1 and V3 to the piezoelectric elements 51A, 51B, 51E and 51F.

[0041] The control device 4 is, for example, a computer, having a processor for processing information, a memory connected to the processor in a communicative manner, and an external interface. Furthermore, the memory stores programs that can be executed by the processor, which reads and executes the programs stored in the memory. This control device 4 receives instructions from a host computer (not shown) and, based on these instructions, controls the drive of the piezoelectric drive device 5, causing the second component 3 to move to the target position.

[0042] like Figure 7 As shown, the control device 4 includes a drive signal generation unit 41, a drive algorithm selection unit 42, a movement amount detection unit 43 for detecting the movement amount of the second component 3, and a movement direction detection unit 44 for detecting the movement direction of the second component 3.

[0043] The movement detection unit 43 detects the movement of the second component 3, i.e., the rotation around the rotation axis Jθ, based on the output signal of the encoder 54. The movement direction detection unit 44 detects the movement direction of the second component 3, i.e., the rotation direction around the rotation axis Jθ (arrows B1 / B2), based on the output signal of the encoder 54.

[0044] The drive algorithm selection unit 42 selects the drive algorithm for the piezoelectric actuator 51 based on the detection results of the movement amount detection unit 43 and the movement direction detection unit 44. The drive algorithm is selected from the first drive mode Dm1 and the second drive mode Dm2, as described below. The drive signal generation unit 41 generates drive signals V1, V2, and V3 based on the drive algorithm selected by the drive algorithm selection unit 42 and instructions from a host computer (not shown), and applies the generated drive signals V1, V2, and V3 to the piezoelectric actuator 51. According to this method, the actual rotation amount and rotation direction detected by the encoder 54 are fed back, thus enabling precise control of the movement of the second component 3.

[0045] The above provides a brief overview of the structure of robot 1. Next, the control method for the piezoelectric drive device 5 will be explained. The control method for the piezoelectric drive device 5 switches the drive algorithm accordingly to the external force F acting on robot 1. This minimizes the influence of the external force F and allows for precise control of the robot 1's minute movements. It should be noted that while the external force F is not particularly limited, examples include a force F1 applied to the second member 3 in the opposite direction to the rotation direction, a force F2 applied in the same direction as the rotation direction, and a force F3 acting as gravity applied to the second member 3 in the vertical direction.

[0046] Figure 8 Examples of the effects of forces F1 and F2 are shown. Figure 8In this configuration, the rotation axis Jθ is along the vertical direction. Furthermore, the wiring C, used for supplying power, communication, etc., to the second component 3, is routed from the first component 2 to the second component 3. Therefore, depending on the posture of the second component 3, forces F1 or F2, which act as restoring forces (forces to restore the wiring C to its natural state) due to deformation, twisting, etc., are generated in the second component 3. These forces F1 and F2 can sometimes affect the rotation of the second component 3. Specifically, because force F1 opposes the driving force of the piezoelectric drive device 5, the second component 3 may sometimes move to the opposite side of the target (force F1 > driving force), remain stationary (force F1 = driving force), or move less than the target (force F1 < driving force). Conversely, because force F2 is applied to the driving force of the piezoelectric drive device 5, the movement of the second component 3 may sometimes be greater than the target. Due to the application of forces F1 and F2 in this way, the rotational characteristics of the second component 3 change, making it difficult to perform precise control of the minute movements of the second component 3.

[0047] exist Figure 9 and Figure 10 The example shown is an example of the effect of force F3. Figure 9 , Figure 10 In the diagram, the lower side of the paper is the vertical lower side, and the rotation axis Jθ is along the horizontal direction. Therefore, depending on the orientation of the second component 3, the force F3 can sometimes affect the rotation of the second component 3. Specifically, in Figure 9 In the case shown, because force F3 opposes the driving force of the piezoelectric drive device 5, the second component 3 sometimes moves to the side opposite to the target direction, or remains stationary, or moves less than the target. Conversely, in Figure 10 In the case shown, because force F3 is applied to the driving force of the piezoelectric drive device 5, the amount of movement of the second component 3 is sometimes greater than the target. Due to the application of force F3 in this way, the rotational characteristics of the second component 3 change, making it difficult to perform precise control of the minute movements of the second component 3.

[0048] As described above, the positional accuracy of the second component 3 may decrease due to the influence of the external force F. Therefore, as mentioned earlier, in this embodiment, by switching the drive algorithm in accordance with the external force F experienced by the robot 1, the influence of the external force F can be minimized, and the minute movements of the robot 1 can be controlled with good precision.

[0049] First, the drive algorithm pre-set for robot 1 will be explained. In this embodiment, the drive algorithm is set as follows: Figure 11 The first driving mode Dm1, which sets the feed amplitude W1, which is the amplitude of bending vibration, to a fixed value while increasing the separation amplitude W2, which is the amplitude of longitudinal vibration, is shown. Figure 12The second driving mode Dm2 is shown, which increases the feed amplitude W1 and the separation amplitude W2 simultaneously. It should be noted that in this embodiment, the feed amplitude W1 is controlled by the voltage values ​​of the driving signals V1 and V3, and the separation amplitude W2 is controlled by the voltage value of the driving signal V2. However, the control method of amplitudes W1 and W2 is not limited to this. For example, they can also be controlled by frequency or phase.

[0050] It should be noted that, as will be understood from the following description, "setting the feed amplitude W1 to a fixed value" means setting the voltage values ​​of the drive signals V1 and V3 that control the bending vibration to a fixed state, but the actual amplitude is not necessarily limited to a fixed state. In addition, the term "fixed" includes not only the case where it does not change over time, but also the case where there may be minor changes in the circuit configuration.

[0051] Figure 11 The first drive mode Dm1 shown sets the feed amplitude W1 to a fixed value and only gradually increases the separation amplitude W2. Therefore, it is easy to generate the minimum required driving force. Consequently, it is difficult for the rotor 52 to experience sudden and large movements due to excessive driving force, and stopping accuracy is also good. On the other hand, because the driving force is increased little by little to generate the minimum required driving force, it is easily affected by external force F at the beginning of the drive. Figure 12 The second drive mode Dm2, as shown, gradually increases both the feed amplitude W1 and the separation amplitude W2. Therefore, although it is initially susceptible to the influence of the external force F, the rate of increase in driving force is higher than in the first drive mode Dm1, making it less susceptible to the influence of the external force F thereafter. On the other hand, compared to the first drive mode Dm1, the feed amplitude W1 increases at a faster rate, so depending on the rotational speed of the rotor 52, the stopping accuracy may decrease due to excessive driving force. By switching between these two drive modes, Dm1 and Dm2, with their different characteristics and the corresponding external force F, it is less susceptible to the influence of the external force F, enabling high-precision micro-motion control.

[0052] In addition, such as Figure 11 , Figure 12As shown, in the first drive mode Dm1 and the second drive mode Dm2, the piezoelectric actuator 51 is excited to induce bending vibration and then longitudinal vibration. According to this method, the first drive mode Dm1 and the second drive mode Dm2 are less susceptible to the influence of external force F. Specifically, the state in which the piezoelectric actuator 51 induces bending vibration is such that the transmission section 514 is pressed against the rotor 52 by the force-applying member 53. Therefore, bending deformation of the vibration section 511 is not allowed, and in fact, bending vibration does not occur in the vibration section 511. This state is analogous to a car, where one simultaneously presses the accelerator and the brake, preventing the car from starting. When the piezoelectric actuator 51 induces longitudinal vibration in this state, simultaneously with the transmission section 514 separating from the rotor 52 through longitudinal vibration, the suppressed bending vibration is released, generating elliptical motion of the transmission section 514. In other words, the time delay from the separation of the transmission unit 514 from the rotor 52 to the generation of driving force is very short (essentially zero). Therefore, the rotor 52 will not be in a free state and is difficult to be affected by external force F.

[0053] It should be noted that, in contrast, when longitudinal vibration is excited followed by bending vibration, the transmission part 514 separates from the rotor 52 before the force delivered to the rotor 52 is generated. This state is equivalent to disengaging the brakes without pressing the accelerator when comparing it to a car. Therefore, the rotor 52 becomes free and may move unexpectedly due to the influence of the external force F, making it difficult to control the robot 1's minute movements.

[0054] The following is based on Figure 13 The control method for the piezoelectric drive device 5 will be explained below, but this control is performed by the control device 4. In the control method for the piezoelectric drive device 5, firstly, as step S1, the drive algorithm of the piezoelectric actuator 51 is set to a first drive mode Dm1. Secondly, the piezoelectric actuator 51 is driven using the set drive mode, here the first drive mode Dm1. The reason for using the first drive mode Dm1 first is, as mentioned earlier, that the second component 3 has higher precision in minute movements compared to the second drive mode Dm2. It is optimal if the drive can be performed without problems using the first drive mode Dm1.

[0055] Next, as step S3, it is determined whether the drive algorithm is the first drive mode Dm1. Since the drive algorithm is the first drive mode Dm1, as step S4, it is determined whether a movement (rotation) exceeding a predetermined value in the opposite direction to the movement direction of the second component 3 has occurred, based on the output signal of the encoder 54. Therefore, it is possible to determine the external force F (in the opposite direction to the movement direction). Figure 8 The force F1 shown in the figure or Figure 9The effect of force F3 on the piezoelectric drive device 5 is shown in the figure. This determination is based on the output signal of encoder 54, making the determination easy and accurate.

[0056] If the amount of movement of the second component 3 in the opposite direction exceeds a predetermined value, as step S5, the drive of the piezoelectric drive device 5 is stopped. The reason is that the external force F (force F1 or F3) applied to the robot 1 is large, and the driving force of the first drive mode Dm1 is insufficient to move the second component 3 to the target position.

[0057] Next, as step S6, the driving algorithm is switched from the first driving mode Dm1 to the second driving mode Dm2, and the process returns to step S2 to drive the piezoelectric actuator 51 in the set driving mode, which is the second driving mode Dm2 in this case. That is, when the influence of the external force F is greater than the reference value, the driving algorithm is switched to the second driving mode Dm2, and the driving of the piezoelectric actuator 51 is restarted. This results in a larger driving force than the first driving mode Dm1, thus increasing the likelihood that the second component 3 can move to the target position against the external force F. Next, as step S3, it is determined whether the driving algorithm is the first driving mode Dm1. Here, since the driving algorithm is the second driving mode Dm2, as step S7, it is determined whether the second component 3 has reached the target position based on the output signal of the encoder 54.

[0058] Here, returning to step S4, if the movement of the second component 3 in the opposite direction is less than a predetermined value, then as step S8, it is determined based on the output signal of the encoder 54 whether a movement (rotation) of the second component 3 in the moving direction exceeding a predetermined value has occurred. Thus, the external force F in the moving direction can be determined. Figure 8 The force F2 shown in the figure or Figure 10 The influence of the force F3 shown in the diagram on the driving of the piezoelectric drive device 5 is determined through steps S4 and S8. In other words, the influence of the external force F on the driving of the piezoelectric drive device 5 can be determined. If the second member 3 moves more than a predetermined value in the moving direction, the driving of the piezoelectric drive device 5 is stopped as step S9. This is because the external force F applied to the robot 1 becomes too large, making it difficult to move the second member 3 to the target position using the second drive mode Dm2. On the other hand, if the amount of movement of the second member 3 in the moving direction is less than a predetermined value, the process proceeds to step S7.

[0059] In step S7, if the second component 3 reaches the target position, step S10 stops the piezoelectric drive device 5. Thus, the movement of the second component 3 towards the target position ends normally. On the other hand, if the second component 3 has not reached the target position, step S11 determines whether the feed amplitude W1 and the separation amplitude W2 have both reached their upper limits. It is considered that the second component 3 has not reached the target position because, due to the influence of the external force F in the opposite direction, the second component 3 has not moved in the moving direction, or its moving speed has decreased. Therefore, if the feed amplitude W1 and the separation amplitude W2 have not both reached their upper limits, step S11 is repeatedly performed until the feed amplitude W1 and the separation amplitude W2 reach their upper limits together, that is, until the driving force of the piezoelectric drive device 5 reaches its maximum. On the other hand, if the feed amplitude W1 and the separation amplitude W2 have both reached their upper limits, it is anticipated that there will be no further increase in driving force, so the process proceeds to step S9, where the drive of the piezoelectric drive device 5 is stopped. Furthermore, after stopping the piezoelectric drive device 5 in step S9, step S12 is performed to notify the user of an error and to inform them that the operation has stopped due to an abnormality.

[0060] According to this control method, the piezoelectric drive device 5 is driven by either a first drive mode Dm1 or a second drive mode Dm2, both capable of excellent micro-motion control. Therefore, excellent micro-motion control can be achieved regardless of the presence or absence of an external force F, enabling the second component 3 to move towards the target position with greater precision. Furthermore, if it is determined that the second component 3 cannot be moved to the target position using the first drive mode Dm1 due to the influence of the external force F, the drive algorithm is immediately switched to the second drive mode Dm2, which can exert a greater driving force than the first drive mode Dm1, thus also being less susceptible to the influence of force F. Therefore, according to this control method, the influence of the external force F can be minimized, and the micro-motions of the robot 1 can be controlled with high precision.

[0061] The control method of the piezoelectric drive device 5 has been described above. In this control method, as previously described, the piezoelectric drive device 5 includes: a vibration section 511 equipped with piezoelectric elements 51A to 51F; and a transmission section 514 that transmits the vibration of the vibration section 511 to the rotor 52, which is the driven body. The piezoelectric drive device 5 vibrates the vibration section 511 by energizing the piezoelectric elements 51A to 51F, combining longitudinal and bending vibrations, causing the transmission section 514 to perform elliptical motion, which in turn moves the rotor 52. In the control method of the piezoelectric drive device 5, the drive algorithm is switched according to a first drive mode Dm1, which sets the feed amplitude W1 (as the amplitude of bending vibration) to a fixed value while varying the separation amplitude W2 (as the amplitude of longitudinal vibration), and a second drive mode Dm2, which varies both the feed amplitude W1 and the separation amplitude W2. According to this control method, the influence of external force F can be minimized as much as possible, and the minute movements of the piezoelectric drive device 5 can be controlled with good precision.

[0062] Furthermore, as described above, the control method for the piezoelectric drive device 5 includes: step S2, driving the piezoelectric actuator 51 in a first drive mode Dm1; and step S4, determining the influence of the external force F, and based on the determination result, maintaining the drive algorithm in the first drive mode Dm1 or switching to the second drive mode Dm2. Thus, a preferred drive mode can be selected, and the influence of the external force F can be minimized as much as possible.

[0063] Furthermore, as mentioned earlier, when the influence of the external force F is greater than the reference value, the driving algorithm is switched to the second driving mode Dm2. This results in a greater driving force than the first driving mode Dm1, thus increasing the likelihood of moving the second component 3 to the target position against the external force F.

[0064] Furthermore, as mentioned earlier, the influence of the external force F is determined based on the output signal of the encoder 54 that detects the displacement of the rotor 52. This makes the determination easy and accurate.

[0065] Furthermore, as mentioned earlier, in the first drive mode Dm1 and the second drive mode Dm2, longitudinal vibration is excited after bending vibration. This makes it less susceptible to the influence of external force F, enabling more precise micro-movement control.

[0066] Furthermore, as mentioned earlier, the driven body is a rotor 52 that rotates. This makes it easy to rotate the second component 3, which is the moved body.

[0067] Alternatively, as mentioned earlier, the driven body can also be a linearly moving slider 55. This facilitates the linear movement of the second component 3, which is the moved body.

[0068] Furthermore, as mentioned earlier, the external force F is the restoring force F1 and F2 based on the wiring C. Since various mechanical devices that can be used with the piezoelectric drive device 5 have wiring C, it becomes a highly versatile control method.

[0069] Furthermore, as mentioned earlier, the external force F is the force F3 that acts as gravity. Except in special environments, force F3 is usually applied to various mechanical devices that can use piezoelectric drive devices 5, thus making it a highly versatile control method.

[0070] Furthermore, as mentioned above, in the control method of robot 1, robot 1 includes: a piezoelectric drive device 5 having a vibration section 511 with piezoelectric elements 51A to 51F, and a transmission section 514 that transmits the vibration of the vibration section 511 to the rotor 52, which is a driven body. The piezoelectric drive device 5, by energizing the piezoelectric elements 51A to 51F, combines longitudinal vibration and bending vibration to cause the vibration section 511 to vibrate, and causes the transmission section 514 to perform elliptical motion, thereby moving the rotor 52; and a second member 3, which is a movable part driven by the piezoelectric drive device 5. In the control method of robot 1, in response to the external force F received by the rotor 52, the drive algorithm is switched according to a first drive mode Dm1 in which the feed amplitude W1, which is the amplitude of bending vibration, is fixed while the separation amplitude W2, which is the amplitude of longitudinal vibration, is varied, and a second drive mode Dm2 in which the feed amplitude W1 and the separation amplitude W2 are varied together. According to this control method, the influence of external force F can be minimized as much as possible, and the minute movements of robot 1 can be controlled with good precision.

[0071] Additionally, as described above, the robot 1 includes: a piezoelectric drive device 5, which has a vibrating section 511 equipped with piezoelectric elements 51A to 51F, and a transmission section 514 that transmits the vibration of the vibrating section 511 to the rotor 52, which is the driven body. The piezoelectric drive device 5, by energizing the piezoelectric elements 51A to 51F, combines longitudinal and bending vibrations to cause the vibrating section 511 to vibrate, causing the transmission section 514 to perform elliptical motion, thereby moving the rotor 52; a second component 3, which is a movable part driven by the piezoelectric drive device 5; and a control device 4, which controls the drive of the piezoelectric drive device 5. Furthermore, the control device 4, in response to the external force F acting on the rotor 52, switches the drive algorithm between a first drive mode Dm1, which sets the feed amplitude W1 (as the amplitude of bending vibration) to a fixed value while varying the separation amplitude W2 (as the amplitude of longitudinal vibration), and a second drive mode Dm2, which varies both the feed amplitude W1 and the separation amplitude W2. According to this control method, the influence of external force F can be minimized as much as possible, and the minute movements of robot 1 can be controlled with good precision.

[0072] <Second Implementation>

[0073] Figure 14 This is a diagram illustrating the robot involved in the second embodiment.

[0074] Figure 14 The robot 6 shown is a horizontal articulated robot (SCARA robot). Although the application of robot 6 is not particularly limited, it can be used for feeding, unloading, conveying, and assembling objects such as precision equipment or its components.

[0075] The robot 6 has: a base 60 fixed to the ground, etc.; a first arm 61 connected to the base 60; a second arm 62 connected to the first arm 61; a third arm 63 connected to the second arm 62; a fourth arm 64 connected to the third arm 63; and an end effector 65 connected to the fourth arm 64.

[0076] Furthermore, the first arm 61 moves relative to the base 60 along the first linear axis Jr1 and rotates about a first rotational axis Jθ1 parallel to the first linear axis Jr1. The second arm 62 moves relative to the first arm 61 along the second linear axis Jr2 orthogonal to the first linear axis Jr1 and rotates about a second rotational axis Jθ2 parallel to the first rotational axis Jθ1. The third arm 63 rotates relative to the second arm 62 about a third rotational axis Jθ3 orthogonal to the second rotational axis Jθ2. The fourth arm 64 rotates relative to the third arm 63 about a fourth rotational axis Jθ4 orthogonal to the third rotational axis Jθ3. The robot 6 moves the end effector 65 to the target position and orientation by combining the movements about these four rotational axes Jθ1, Jθ2, Jθ3, and Jθ4 with the movements along the two linear axes Jr1 and Jr2.

[0077] The first arm 61 has: a first direct motion part 611 connected to the base 60 and movable relative to the base 60 in the direction of a first direct motion axis Jr1; and a first rotation part 612 connected to the first direct motion part 611 and rotating relative to the first direct motion part 611 about a first rotation axis Jθ1.

[0078] The second arm 62 has: a long, linearly moving portion 621 connected to the first rotating portion 612, which moves relative to the first rotating portion 612 in the direction of the second linearly moving axis Jr2; and a second rotating portion 622 connected to the front end of the second linearly moving portion 621, which rotates relative to the second linearly moving portion 621 about the second rotating axis Jθ2. It should be noted that the second linearly moving axis Jr2 is orthogonal to the first rotating axis Jθ1, and rotates about the first rotating axis Jθ1 as the first rotating portion 612 rotates about the first rotating axis Jθ1. Furthermore, the second rotating axis Jθ2 is parallel to the first rotating axis Jθ1, and the separation distance D between the second linearly moving portion 621 and the first rotating axis Jθ1 changes as the second linearly moving portion 621 moves in the direction of the second linearly moving axis Jr2.

[0079] The third arm 63 has: an arm portion 631 connected to the second rotating portion 622; and a third rotating portion 632 connected to the arm portion 631 and capable of rotating about a third rotating axis Jθ3. The arm portion 631 is formed into a generally L-shape, bent at approximately a right angle along its length, with its base end connected to the second rotating portion 622 and its front end connected to the third rotating portion 632. It should be noted that the third rotating axis Jθ3 is orthogonal to the second rotating axis Jθ2, and rotates about the second rotating axis Jθ2 as the second rotating portion 622 rotates about the second rotating axis Jθ2.

[0080] The fourth arm 64 has: an arm portion 641 connected to the third rotating portion 632; and a fourth rotating portion 642 connected to the arm portion 641, capable of rotating about a fourth rotating axis Jθ4. The arm portion 641 is formed into a roughly L-shape, bent at approximately a right angle along its length, with its base end connected to the third rotating portion 632 and its front end connected to the fourth rotating portion 642. It should be noted that the fourth rotating axis Jθ4 is orthogonal to the third rotating axis Jθ3, and rotates about the third rotating axis Jθ3 as the third rotating portion 632 rotates about the third rotating axis Jθ3.

[0081] The end effector 65 is connected to the fourth rotating part 642. The end effector 65 is a mechanism for causing the robot 6 to perform a specified task. For example, it can be any configuration such as a mechanism for holding the workpiece W, a mechanism for adsorbing the workpiece W, a mechanism for applying adhesive to the workpiece W, etc.

[0082] The robot 6 also includes: a piezoelectric drive device 5A for moving the first linear actuator 611 relative to the base 60 in the direction of the first linear actuator axis Jr1; a piezoelectric drive device 5B for rotating the first rotating actuator 612 relative to the first linear actuator 611 about the first rotating axis Jθ1; a piezoelectric drive device 5C for moving the second linear actuator 621 relative to the first rotating actuator 612 in the direction of the second linear actuator axis Jr2; a piezoelectric drive device 5D for rotating the second rotating actuator 622 relative to the second linear actuator 621 about the second rotating axis Jθ2; a piezoelectric drive device 5E for rotating the third rotating actuator 632 relative to the second rotating actuator 622 about the third rotating axis Jθ3; a piezoelectric drive device 5F for rotating the fourth rotating actuator 642 relative to the third rotating actuator 632 about the fourth rotating axis Jθ4; and a control device 4 for independently controlling these piezoelectric drive devices 5A to 5F.

[0083] Among them, piezoelectric drive devices 5A and 5C are composed of Figure 3 The direct-acting piezoelectric drive device 5 shown in the figure is composed of piezoelectric drive devices 5B, 5D, 5E, and 5F. Figure 2 The rotary piezoelectric drive device 5 shown in the figure is composed of [the following].

[0084] It should be noted that, although not shown in the diagram, in the piezoelectric drive device 5A, the direct-acting shaft Jr coincides with the first direct-acting shaft Jr1. One of the piezoelectric actuator 51 and the slider 55 is fixed to the base 60, and the other is fixed to the first direct-acting part 611. Therefore, the first arm 61 moves relative to the base 60 in the direction of the first direct-acting shaft Jr1 by the drive of the piezoelectric drive device 5A. Furthermore, in the piezoelectric drive device 5B, the rotating shaft Jθ coincides with the first rotating shaft Jθ1. One of the piezoelectric actuator 51 and the rotor 52 is fixed to the first direct-acting part 611, and the other is fixed to the first rotating part 612. Therefore, the first rotating part 612 rotates relative to the first direct-acting part 611 about the first rotating shaft Jθ1 by the drive of the piezoelectric drive device 5B.

[0085] Furthermore, in the piezoelectric drive device 5C, the direct-acting shaft Jr coincides with the second direct-acting shaft Jr2. One of the piezoelectric actuator 51 and the slider 55 is fixed to the first rotating part 612, and the other is fixed to the second direct-acting part 621. Therefore, the second direct-acting part 621 moves relative to the first rotating part 612 in the direction of the second direct-acting shaft Jr2 by the drive of the piezoelectric drive device 5C. In addition, in the piezoelectric drive device 5D, the rotating shaft Jθ coincides with the second rotating shaft Jθ2. One of the piezoelectric actuator 51 and the rotor 52 is fixed to the second direct-acting part 621, and the other is fixed to the second rotating part 622. Therefore, the second rotating part 622 rotates relative to the second direct-acting part 621 about the second rotating shaft Jθ2 by the drive of the piezoelectric drive device 5D.

[0086] Furthermore, in the piezoelectric drive device 5E, the rotation axis Jθ coincides with the third rotation axis Jθ3. One of the piezoelectric actuator 51 and the rotor 52 is fixed to the arm portion 631, and the other is fixed to the third rotating portion 632. Therefore, the third rotating portion 632 rotates relative to the arm portion 631 about the third rotation axis Jθ3 by the drive of the piezoelectric drive device 5E. In the piezoelectric drive device 5F, the rotation axis Jθ coincides with the fourth rotation axis Jθ4. One of the piezoelectric actuator 51 and the rotor 52 is fixed to the arm portion 641, and the other is fixed to the fourth rotating portion 642. Therefore, the fourth rotating portion 642 rotates relative to the arm portion 641 about the fourth rotation axis Jθ4 by the drive of the piezoelectric drive device 5F.

[0087] The above describes robot 6. In this robot 6, at least one of the piezoelectric drive devices 5A to 5F can be applied to the control method described in the first embodiment (hereinafter also referred to as "this control method"). That is, the drive algorithm can be switched between a first drive mode Dm1 and a second drive mode Dm2 in response to the external force F acting on the rotor 52 or the slider 55. This minimizes the influence of the external force F and allows for precise control of the small movements of robot 6. It should be noted that the choice of which piezoelectric drive device 5A to 5F to use this control method can be appropriately determined based on factors such as the robot 6's orientation, movement trajectory, and wiring configuration.

[0088] The second embodiment described above achieves the same effects as the first embodiment. It should be noted that for joints that do not use this control method, a device combining a drive device other than a piezoelectric drive device, such as an electromagnetic motor and a reducer, can also be used.

[0089] <Third Implementation Method>

[0090] Figure 15 This is a diagram illustrating the robot according to the third embodiment.

[0091] Figure 15 The robot 7 shown is a 6-axis robot with 6 drive axes. Robot 7 includes: a base 70 fixed to the ground, etc.; a first arm 71 rotatably connected to the base 70; a second arm 72 rotatably connected to the first arm 71; a third arm 73 rotatably connected to the second arm 72; a fourth arm 74 rotatably connected to the third arm 73; a fifth arm 75 rotatably connected to the fourth arm 74; a sixth arm 76 rotatably connected to the fifth arm 75; and an end effector 77, serving as a worktable located at the front end of the sixth arm 76. Furthermore, the end effector 77 includes: a base portion 771 fixed to the sixth arm 76; and a platform portion 772 that moves linearly relative to the base portion 771.

[0092] In addition, the robot 7 includes: a piezoelectric drive device 5G that rotates the first arm 71 relative to the base 70; a piezoelectric drive device 5H that rotates the second arm 72 relative to the first arm 71; a piezoelectric drive device 5I that rotates the third arm 73 relative to the second arm 72; a piezoelectric drive device 5J that rotates the fourth arm 74 relative to the third arm 73; a piezoelectric drive device 5K that rotates the fifth arm 75 relative to the fourth arm 74; a piezoelectric drive device 5L that rotates the sixth arm 76 relative to the fifth arm 75; a piezoelectric drive device 5M that causes the platform 772 to move linearly relative to the base 771; and a control device 4 that independently controls these piezoelectric drive devices 5G to 5M.

[0093] Among them, the piezoelectric drive devices 5G to 5L are composed of Figure 2 The rotary piezoelectric drive device 5 shown in the figure is composed of piezoelectric drive device 5M consisting of Figure 3 The direct-acting piezoelectric drive device 5 shown in the figure is configured.

[0094] The above describes robot 7. In this robot 7, this control method can be applied to at least one of the piezoelectric drive devices 5G to 5M. That is, in response to the external force F acting on the rotor 52 or the slider 55, the drive algorithm can be switched between a first drive mode Dm1 and a second drive mode Dm2. This minimizes the influence of the external force F and allows for precise control of the robot 7's minute movements. It should be noted that, for example, the choice of which piezoelectric drive device 5G to 5M to use this control method can be appropriately determined based on the robot 7's orientation, motion path, wiring configuration, etc.

[0095] The same effects as the first embodiment described above can be achieved through this third embodiment. It should be noted that for joints that do not use this control method, a device combining a drive device other than a piezoelectric drive device, such as an electromagnetic motor and a reducer, can also be used.

[0096] The control method for the piezoelectric drive device, the control method for the robot, and the robot of the present invention have been described above based on the illustrated embodiments. However, the present invention is not limited thereto, and the configuration of each part can be replaced with any configuration having the same function. Furthermore, other arbitrary configurations can be added to the present invention. Additionally, the control method for the piezoelectric drive device can also be applied to any machine other than a robot.

Claims

1. A control method for a piezoelectric drive device, characterized in that, The piezoelectric drive device includes: a vibrating part equipped with a piezoelectric element; and a transmission part that transmits the vibration of the vibrating part to a driven body. The piezoelectric drive device causes the vibrating part to vibrate and the transmission part to perform elliptical motion by combining longitudinal and bending vibrations through energizing the piezoelectric element, thereby moving the driven body through the elliptical motion. In the control method of the piezoelectric drive device, Corresponding to the external force acting on the driven body, the drive algorithm of the piezoelectric drive device is switched according to a first drive mode and a second drive mode. The first drive mode is a mode in which the feed amplitude, which is the amplitude of the bending vibration, is fixed while the separation amplitude, which is the amplitude of the longitudinal vibration, is varied. The second drive mode is a mode in which the feed amplitude and the separation amplitude are varied together. The control method of the piezoelectric drive device has the following characteristics: The steps of driving the piezoelectric actuator in the first driving mode; as well as The step of determining the influence of the external force and, based on the determination result, maintaining the driving algorithm in the first driving mode or switching it to the second driving mode. If the influence of the external force is greater than the reference value, the driving algorithm will be switched to the second driving mode. The influence of the external force is determined based on the output signal of the encoder that detects the displacement of the driven body.

2. The control method for the piezoelectric drive device according to claim 1, characterized in that, In the first driving mode and the second driving mode, the longitudinal vibration is excited after the bending vibration is excited.

3. The control method for the piezoelectric drive device according to claim 1, characterized in that, The driven body is a rotor that rotates.

4. The control method for the piezoelectric drive device according to claim 1, characterized in that, The driven body is a linearly moving slider.

5. The control method for the piezoelectric drive device according to claim 1, characterized in that, The external force is a force based on the restoring force of the wiring in the piezoelectric drive device.

6. The control method for the piezoelectric drive device according to claim 1, characterized in that, The external force mentioned is gravity.

7. A method for controlling a robot, characterized in that, The robot has a piezoelectric drive device and a movable part. The piezoelectric drive device includes: a vibrating part with a piezoelectric element; and a transmission part that transmits the vibration of the vibrating part to a driven body. The piezoelectric drive device combines longitudinal and bending vibrations by energizing the piezoelectric element, causing the vibrating part to vibrate and the transmission part to perform elliptical motion. The driven body is moved by the elliptical motion. The movable part is driven by the piezoelectric drive device. In the robot control method, Corresponding to the external force acting on the driven body, the drive algorithm of the piezoelectric drive device is switched according to a first drive mode and a second drive mode. The first drive mode is a mode in which the feed amplitude, which is the amplitude of the bending vibration, is fixed while the separation amplitude, which is the amplitude of the longitudinal vibration, is varied. The second drive mode is a mode in which the feed amplitude and the separation amplitude are varied together. The robot control method has the following characteristics: The steps of driving the piezoelectric actuator in the first driving mode; as well as The step of determining the influence of the external force and, based on the determination result, maintaining the driving algorithm in the first driving mode or switching it to the second driving mode. If the influence of the external force is greater than the reference value, the driving algorithm will be switched to the second driving mode. The influence of the external force is determined based on the output signal of the encoder that detects the displacement of the driven body.

8. A robot, characterized in that, It has a piezoelectric drive, a movable part, and a control device. The piezoelectric drive device includes: a vibrating part, which has a piezoelectric element; The piezoelectric drive device transmits the vibration of the vibrating part to the driven body by energizing the piezoelectric element to combine longitudinal and bending vibrations, causing the vibrating part to vibrate and the transmission part to perform elliptical motion, thereby moving the driven body through the elliptical motion. The movable part is driven by the piezoelectric drive device. The control device controls the drive of the piezoelectric drive device. Corresponding to the external force acting on the driven body, the control device switches the drive algorithm of the piezoelectric drive device according to a first drive mode and a second drive mode. The first drive mode is a mode in which the feed amplitude, which is the amplitude of the bending vibration, is fixed while the separation amplitude, which is the amplitude of the longitudinal vibration, is varied. The second drive mode is a mode in which the feed amplitude and the separation amplitude are varied together. The control device drives the piezoelectric actuator in the first drive mode. The control device determines the influence of the external force, and based on the determination result, maintains the driving algorithm in the first driving mode or switches it to the second driving mode. If the influence of the external force is greater than the reference value, the driving algorithm will be switched to the second driving mode. The influence of the external force is determined based on the output signal of the encoder that detects the displacement of the driven body.

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