Control method of robot and robot

Abstract

The present invention provides a control method for a robot and a robot, which are not easily affected by gravity and can suppress the position deviation of the end effector caused by gravity. The robot includes: a first component; a second component connected to the first component; a driving device that rotates or slides the second component relative to the first component; and an end effector connected to the second component, wherein the posture of the end effector changes due to the driving of the driving device. The control method of the robot detects a gravity influence amount representing the degree of influence of gravity received by the end effector based on an output signal from an inertial sensor disposed on the end effector, determines a driving algorithm of the driving device from a plurality of driving modes based on the detected gravity influence amount, and drives the driving device by the determined driving algorithm.

Description

Technical Field

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

[0002] For example, Patent Document 1 discloses a robot having a first arm, a second arm, a piezoelectric actuator that rotates the second arm relative to the first arm, and an inclination angle sensor disposed at the tip of the second arm. In this robot, the deflection and torsion of the second arm are measured based on the output of the inclination angle sensor, and the drive signal of the piezoelectric actuator is corrected based on the measured values to suppress the position deviation of the second arm.

[0003] Patent Document 1: Japanese Patent Laid-Open No. 7-178689

[0004] In the robot described in Patent Document 1, since the inclination angle sensor is disposed on the second arm, the position deviation of the second arm can be suppressed with high precision. However, the position deviation of the end effector connected to the tip of the second arm cannot be suppressed with high precision. Summary of the Invention

[0005] In the control method of the robot of the present invention, the robot includes: a first component; a second component connected to the first component; a drive device that rotates or slides the second component relative to the first component; and an end effector connected to the second component, the attitude of the end effector changing due to the drive of the drive device. The control method of the robot detects a gravity influence amount indicating the degree of influence of gravity on the end effector based on an output signal from an inertial sensor disposed on the end effector, determines a drive algorithm of the drive device from a plurality of drive modes based on the detected gravity influence amount, and drives the drive device by the determined drive algorithm.

[0006] The robot of the present invention includes: a first component; a second component connected to the first component; a drive device that rotates or slides the second component relative to the first component; an end effector connected to the second component; and a control device that controls the drive of the drive device. The control device detects a gravity influence amount indicating the degree of influence of gravity on the end effector based on an output signal from an inertial sensor disposed on the end effector, determines a drive algorithm of the drive device from a plurality of drive modes based on the detected gravity influence amount, and drives the drive device by the determined drive algorithm. Brief Description of the Drawings

[0007] Figure 1 It is a diagram showing a robot according to a first embodiment.

[0008] Figure 2 It is a diagram showing a piezoelectric driving device.

[0009] Figure 3 It is a diagram showing the driving signal of a piezoelectric actuator.

[0010] Figure 4 It is a diagram showing the vibration state of a piezoelectric actuator.

[0011] Figure 5 It is a diagram showing the vibration state of a piezoelectric actuator.

[0012] Figure 6 It is a block diagram showing the structure of a control device.

[0013] Figure 7 It is a diagram showing an attitude that is not easily affected by gravity.

[0014] Figure 8 It is a diagram showing an attitude that is easily affected by gravity.

[0015] Figure 9 It is a diagram showing an attitude that is easily affected by gravity.

[0016] Figure 10 It is a diagram showing the first driving mode.

[0017] Figure 11 It is a diagram showing the first driving mode.

[0018] Figure 12 It is a diagram showing the first driving mode.

[0019] Figure 13 It is a flowchart showing the control method of a robot.

[0020] Figure 14 It is a diagram showing a driving example where the gravity influence amount is "low".

[0021] Figure 15 It is a diagram showing a driving example where the gravity influence amount is "medium".

[0022] Figure 16 It is a diagram showing a driving example where the gravity influence amount is "high".

[0023] Figure 17 It is a diagram showing the second driving mode for the control method of the robot according to the second embodiment.

[0024] Figure 18 It is a flowchart showing the control method of a robot.

[0025] Figure 19 It is a diagram showing the robot according to the third embodiment.

[0026] Explanation of Reference Numerals

[0027] 1... Robot; 10... Base; 11... First arm; 111... First linear motion part; 112... First rotating part; 12... Second arm; 121... Second linear motion part; 122... Second rotating part; 13... Third arm; 131... Arm part; 132... Third rotating part; 14... Fourth arm; 141... Arm part; 142... Fourth rotating part; 15... End effector; 150... Base part; 151... Claw part; 152... Claw part; 2A... Piezoelectric drive device; 2B... Piezoelectric drive device; 2C... Piezoelectric drive device; 2D... Piezoelectric drive device; 2E... Piezoelectric drive device; 2F... Piezoelectric drive device; 2G... Piezoelectric drive device; 2H... Piezoelectric drive device; 21... Piezoelectric actuator; 21A... Piezoelectric element; 21B... Piezoelectric element; 21C... Piezoelectric element; 21D... Piezoelectric element; 21E... Piezoelectric element; 21F... Piezoelectric element; 21G... Piezoelectric element; 211... Vibration part; 212... Support part; 213... Beam part; 214... Transmission part; 22... Rotor; 23... Biasing member; 231... Holding part; 232... Base; 233... Spring group; 234... Spring group; 24... Encoder; 3... Control device; 3A... Control part; 3B... Control part; 3C... Control part; 3D... Control part; 3E... Control part; 3F... Control part; 3G... Control part; 31... Drive signal generation part; 32... Drive algorithm selection part; 33... Attitude detection part; 4... Inertial sensor; 41... Acceleration sensor; A1... Arrow; A2... Arrow; B1... Arrow; B2... Arrow; D... Separation distance; Dm1... First drive mode; Dm11... Mode; Dm12... Mode; Dm13... Mode; Dm2... Second drive mode; G... Gravity; H... Horizontal direction; Jr1... First linear axis; Jr2... Second linear axis; Jr3... Third linear axis; Jθ1... First rotation axis; Jθ2... Second rotation axis; Jθ3... Third rotation axis; Jθ4... Fourth rotation axis; RA... Robot arm; S1... Step; S2... Step; S3... Step; S4... Step; S5... Step; S6... Step; S7... Step; ST... Workbench; V... Vertical direction; V1... Drive signal; V2... Drive signal; V3... Drive signal; W... Workpiece; W1... Feed amplitude; W2... Separation amplitude. Detailed Embodiment

[0028] Hereinafter, a control method and a robot of the present invention will be described in detail based on the embodiments shown in the drawings.

[0029] <First Embodiment>

[0030] Figure 1 is a view showing the robot according to the first embodiment. Figure 2 is a view showing the piezoelectric drive device.Figure 3 is a diagram showing a drive signal for a piezoelectric actuator. Figure 4 and Figure 5 are diagrams showing the vibration states of the piezoelectric actuator, respectively. Figure 6 is a block diagram showing the structure of the control device. Figure 7 is a diagram showing an attitude that is not easily affected by gravity. Figure 8 and Figure 9 are diagrams showing attitudes that are easily affected by gravity, respectively. Figures 10 to 12 are diagrams showing the first drive mode, respectively. Figure 13 is a flowchart showing a control method for the robot. Figure 14 is a diagram showing a drive example where the amount of gravity influence is "low". Figure 15 is a diagram showing a drive example where the amount of gravity influence is "medium". Figure 16 is a diagram showing a drive example where the amount of gravity influence is "high".

[0031] Figure 1 The robot 1 shown is a horizontal multi-joint robot (SCARA robot). The use of the robot 1 is not particularly limited, and examples include feeding, removing, transporting, and assembling of objects such as precision equipment and components constituting the precision equipment.

[0032] The robot 1 includes a base 10 fixed to the floor or the like, a robotic arm RA connected to the base 10, and an end effector 15 connected to the robotic arm RA. In addition, the robotic arm RA includes a first arm 11 connected to the base 10, a second arm 12 connected to the first arm 11, a third arm 13 connected to the second arm 12, and a fourth arm 14 connected to the third arm 13, and the end effector 15 is connected to the fourth arm 14.

[0033] In addition, the first arm 11 moves in the direction of the first linear motion axis Jr1 with respect to the base 10 and rotates about a first rotation axis Jθ1 parallel to the first linear motion axis Jr1. The second arm 12 moves in the direction of the second linear motion axis Jr2 orthogonal to the first linear motion axis Jr1 with respect to the first arm 11 and rotates about a second rotation axis Jθ2 parallel to the first rotation axis Jθ1. The third arm 13 rotates about a third rotation axis Jθ3 orthogonal to the second rotation axis Jθ2 with respect to the second arm 12. The fourth arm 14 rotates about a fourth rotation axis Jθ4 orthogonal to the third rotation axis Jθ3 with respect to the third arm 13. By combining the movements about these four rotation axes Jθ1, Jθ2, Jθ3, Jθ4 and the movements in the two linear motion axes Jr1, Jr2 directions, the robot 1 sets the end effector 15 to a target position and attitude.

[0034] The first arm 11 has a first linear motion part 111 connected to the base 10 and movable relative to the base 10 in the direction of the first linear motion axis Jr1, and a first rotating part 112 connected to the first linear motion part 111 and rotatable relative to the first linear motion part 111 about the first rotation axis Jθ1. It should be noted that in the present embodiment, the first linear motion axis Jr1 and the first rotation axis Jθ1 are respectively along the vertical direction. However, the orientations of these axes Jr1 and Jθ1 are not particularly limited.

[0035] The second arm 12 has a long second linear motion part 121 connected to the first rotating part 112 and movable relative to the first rotating part 112 in the direction of the second linear motion axis Jr2, and a second rotating part 122 connected to the front end of the second linear motion part 121 and rotatable relative to the second linear motion part 121 about the second rotation axis Jθ2. It should be noted that the second linear motion axis Jr2 is orthogonal to the first rotation axis Jθ1 and rotates about the first rotation axis Jθ1 as the first rotating part 112 rotates about the first rotation axis Jθ1. In addition, the second rotation axis Jθ2 is parallel to the first rotation axis Jθ1, and the separation distance D from the first rotation axis Jθ1 changes as the second linear motion part 121 moves in the direction of the second linear motion axis Jr2.

[0036] The third arm 13 has an arm part 131 connected to the second rotating part 122 and a third rotating part 132 rotatably connected to the arm part 131 about the third rotation axis Jθ3. The arm part 131 is in a substantially L shape bent at a right angle in the middle thereof, and the base end is connected to the second rotating part 122 and the front end is connected to the third rotating part 132. It should be noted that the third rotation axis Jθ3 is orthogonal to the second rotation axis Jθ2 and rotates about the second rotation axis Jθ2 as the second rotating part 122 rotates about the second rotation axis Jθ2.

[0037] The fourth arm 14 has an arm part 141 as a first component connected to the third rotating part 132 and a fourth rotating part 142 as a second component rotatably connected to the arm part 141 about the fourth rotation axis Jθ4. The arm part 141 is in a substantially L shape bent at a right angle in the middle thereof, and the base end is connected to the third rotating part 132 and the front end is connected to the fourth rotating part 142. It should be noted that the fourth rotation axis Jθ4 is orthogonal to the third rotation axis Jθ3 and rotates about the third rotation axis Jθ3 as the third rotating part 132 rotates about the third rotation axis Jθ3.

[0038] The robotic arm RA has been described above, but the structure of the robotic arm RA is not particularly limited. For example, it may also be a six-axis robotic arm having six rotation axes.

[0039] The end effector 15 is connected to the fourth rotating part 142. The end effector 15 is a mechanism for causing the robot 1 to perform a predetermined operation. For example, it can be any structure such as a mechanism for gripping the workpiece W, a mechanism for adsorbing the workpiece W, a mechanism for applying an adhesive to the workpiece W, etc. In the illustrated structure, it has a base 150 connected to the fourth rotating part 142, and a pair of claw parts 151, 152 connected to the base 150, and grips or releases the workpiece W by opening and closing the pair of claw parts 151, 152.

[0040] The robot 1 also has an inertial sensor 4 disposed at the base 150 of the end effector 15. And in the robot 1, the attitude of the end effector 15 is detected based on the output signal of the inertial sensor 4. In the present embodiment, an acceleration sensor 41 is used as the inertial sensor 4. In addition, the acceleration sensor 41 is a three-axis acceleration sensor capable of independently detecting the acceleration in each axis direction of the mutually orthogonal X-axis, Y-axis, and Z-axis. Thereby, the attitude of the end effector 15 can be detected with high precision. However, as the inertial sensor 4, there is no particular limitation as long as it can detect the attitude of the end effector 15. For example, an angular velocity sensor can also be used.

[0041] The robot 1 also has: a piezoelectric driving device 2A that moves the first linear motion part 111 relative to the base 10 in the first linear motion axis Jr1 direction; a piezoelectric driving device 2B that rotates the first rotating part 112 relative to the first linear motion part 111 around the first rotation axis Jθ1; a piezoelectric driving device 2C that moves the second linear motion part 121 relative to the first rotating part 112 in the second linear motion axis Jr2 direction; a piezoelectric driving device 2D that rotates the second rotating part 122 relative to the second linear motion part 121 around the second rotation axis Jθ2; a piezoelectric driving device 2E that rotates the third rotating part 132 relative to the second rotating part 122 around the third rotation axis Jθ3; a piezoelectric driving device 2F that rotates the fourth rotating part 142 relative to the third rotating part 132 around the fourth rotation axis Jθ4; a piezoelectric driving device 2G that drives the pair of claw parts 151, 152 to open and close; and a control device 3 that independently controls these respective piezoelectric driving devices 2A to 2G.

[0042] Among these piezoelectric driving devices 2A to 2G, at least for the piezoelectric driving device 2F that controls the driving of the fourth rotating part 142 located at the foremost end side of the robot arm RA, the following characteristic control method is used to control its driving. Therefore, for the sake of convenience in explanation hereinafter, the piezoelectric driving device 2F is taken as an example for explanation, and the explanations for the other piezoelectric driving devices 2A to 2E, 2G are omitted.

[0043] As Figure 2As shown, the piezoelectric drive device 2F as a drive device is a rotary type piezoelectric drive device. The piezoelectric drive device 2F includes a piezoelectric actuator 21, a rotor 22 as a driven body that rotates around a rotation axis Jθ4 under the driving force from the piezoelectric actuator 21, a biasing member 23 that presses the piezoelectric actuator 21 against the rotor 22, and an encoder 24 that detects the rotation amount of the rotor 22. Further, the piezoelectric actuator 21 is fixed to the arm portion 141 via the biasing member 23, and the rotor 22 is fixed to the fourth rotating portion 142. Therefore, when the piezoelectric actuator 21 is driven, the fourth rotating portion 142 rotates around the rotation axis Jθ4 relative to the arm portion 141. Thus, according to the rotary type piezoelectric drive device, it becomes a device suitable for rotating and moving the fourth rotating portion 142. It should be noted that the piezoelectric actuator 21 may be fixed to the fourth rotating portion 142 via the biasing member 23, and the rotor 22 may be fixed to the arm portion 141.

[0044] According to the piezoelectric drive device 2F, the driving force from the piezoelectric actuator 21 is directly transmitted to the rotor 22. Therefore, there is no need for a relay mechanism for relaying the driving force, and simplification and miniaturization of the device can be achieved. In addition, problems such as gaps and reduction in movement accuracy due to insufficient rigidity in a reduction gear or the like substantially disappear, and the robot 1 having excellent driving accuracy is obtained. The piezoelectric drive devices 2B, 2D, 2E, 2G are the same as the piezoelectric drive device 2F and use a rotary type piezoelectric drive device, and the piezoelectric drive devices 2A, 2C use a linear type piezoelectric drive device, and in this linear type piezoelectric drive device, a slider that linearly moves is used instead of the rotor 22.

[0045] The piezoelectric actuator 21 includes a vibrating portion 211, a supporting portion 212 that supports the vibrating portion 211, a beam portion 213 that connects the vibrating portion 211 and the supporting portion 212, and a protruding transmission portion 214 that is disposed at the front end portion of the vibrating portion 211 and transmits the vibration of the vibrating portion 211 to the rotor 22.

[0046] The vibrating portion 211 is plate-shaped and has a rectangular shape with the longitudinal direction of the paper surface as the length. Further, the vibrating portion 211 includes piezoelectric elements 21A to 21F for driving, and a piezoelectric element 21G for detecting the vibration of the vibrating portion 211. At the central portion of the vibrating portion 211, the piezoelectric elements 21C, 21D are arranged in the length direction. Further, on one side of the piezoelectric elements 21C, 21D, the piezoelectric elements 21A, 21B are arranged in the length direction, and on the other side of the piezoelectric elements 21C, 21D, the piezoelectric elements 21E, 21F are arranged in the length direction. These piezoelectric elements 21A to 21F respectively expand and contract in the length direction of the vibrating portion 211 when energized.

[0047] The piezoelectric element 21G for detection is disposed between the piezoelectric elements 21C and 21D. The piezoelectric element 21G receives an external force corresponding to the vibration of the vibrating portion 211 and outputs a detection signal corresponding to the received external force. Accordingly, the vibration state of the vibrating portion 211 can be detected based on the detection signal output from the piezoelectric element 21G.

[0048] The transmission portion 214 is provided at the front end portion of the vibrating portion 211, and its front end contacts the rotor 22. Accordingly, the vibration of the vibrating portion 211 is transmitted to the rotor 22 via the transmission portion 214. The support portion 212 is a portion that supports the vibrating portion 211 and is U-shaped so as to surround both side portions and the base end side of the vibrating portion 211. Further, in a state where the vibration of the vibrating portion 211 is allowed, the beam portion 213 connects the vibrating portion 211 and the support portion 212.

[0049] The biasing member 23 biases the piezoelectric actuator 21 toward the rotor 22, thereby pressing the transmission portion 214 against the rotor 22. Thereby, the vibration of the vibrating portion 211 is efficiently transmitted to the rotor 22 via the transmission portion 214. Further, when the piezoelectric drive device 2F is not driven, braking is applied to the rotor 22 to maintain the attitude of the fourth rotating portion 142. The biasing member 23 has a holding portion 231 that holds the support portion 212, a base 232 fixed to the arm portion 141, and spring groups 233 and 234 that connect the holding portion 231 and the base 232. The biasing member 23 is fixed in a state where the spring groups 233 and 234 are deformed, and presses the piezoelectric actuator 21 against the rotor 22 by the restoring force of the spring groups 233 and 234.

[0050] The piezoelectric drive device 2F is driven in the following manner. For example, when the drive signal V1 shown in Figure 3 is applied to the piezoelectric elements 21A and 21F, the drive signal V2 is applied to the piezoelectric elements 21C and 21D, and the drive signal V3 is applied to the piezoelectric elements 21B and 21E, as shown in Figure 4 the vibrating portion 211 performs longitudinal vibration that expands and contracts in its longitudinal direction and bending vibration that bends in the width direction. After these vibrations are combined, the front end of the transmission portion 214 performs elliptical motion that depicts an elliptical orbit counterclockwise as indicated by the arrow A1. Thereby, the rotor 22 is sent out and rotates clockwise as indicated by the arrow B1. On the other hand, when the drive signals V1 and V3 are switched, that is, when the drive signal V1 is applied to the piezoelectric elements 21B and 21E and the drive signal V3 is applied to the piezoelectric elements 21A and 21F, as shown in Figure 5 the front end of the transmission portion 214 performs elliptical motion that depicts an elliptical orbit clockwise as indicated by the arrow A2, and the rotor 22 rotates counterclockwise as indicated by the arrow B2.

[0051] It should be noted that in the longitudinal vibration and bending vibration of the vibration unit 211, which is the basis of the elliptical motion of the transmission unit 214, the longitudinal vibration is excited by applying the drive signal V2 to the piezoelectric elements 21C and 21D, and the bending vibration is excited by applying the drive signals V1, V3 to the piezoelectric elements 21A, 21B, 21E, and 21F.

[0052] The control device 3 is constituted by, for example, a computer, and has a processor for processing information, a memory communicably connected to the processor, and an external interface. In addition, a program executable by the processor is stored in the memory, and the processor reads and executes the program stored in the memory. Such a control device 3 receives an instruction from a main computer (not shown), and based on this instruction, independently controls the driving of each of the piezoelectric drive devices 2A to 2G so that the end effector 15 assumes a target position and posture.

[0053] As Figure 6 shown, the control device 3 has control units 3A, 3B, 3C, 3D, 3E, 3F, 3G for controlling the piezoelectric drive devices 2A, 2B, 2C, 2D, 2E, 2F, 2G. In particular, the control unit 3F for controlling the driving of the piezoelectric drive device 2F has a drive signal generation unit 31, a drive algorithm selection unit 32, and a posture detection unit 33 for detecting the posture of the end effector 15 and the like. The posture detection unit 33 detects the posture of the end effector 15 based on the output signal of the acceleration sensor 41. In addition, the posture detection unit 33 detects at least the degree of influence of the gravity G applied to the piezoelectric drive device 2F (hereinafter referred to as the gravity influence amount) based on the detected posture. It should be noted that in the present embodiment, in addition to the detected posture, the weights of the end effector 15 and the workpiece W held by the end effector 15 are also considered to detect the gravity influence amount. Thereby, a more accurate gravity influence amount can be detected. It should be noted that as a method for detecting the gravity influence amount, as long as it is a method based on the output signal of the acceleration sensor 41, there is no particular limitation.

[0054] The drive algorithm selection unit 32 selects the drive algorithm of the piezoelectric actuator 21 based on the detection results of the posture detection unit 33, that is, the posture of the end effector 15, the gravity influence amount, and the target position of the end effector 15. As will be described later, the drive algorithm is selected from the first drive mode Dm1 and the second drive mode Dm2. The drive signal generation unit 31 generates the drive signals V1, V2, V3 based on the drive algorithm selected by the drive algorithm selection unit 32 and an instruction from a main computer (not shown), and applies the generated drive signals V1, V2, V3 to the piezoelectric actuator 21. According to such a method, since the actual rotation amount and rotation direction detected by the encoder 24 are feedback-controlled, the movement of the end effector 15 can be controlled with high precision.

[0055] The above briefly described the structure of the robot 1. Next, a control method for the piezoelectric driving device 2F will be described. In the control method of the piezoelectric driving device 2F, the optimal driving algorithm is selected based on the posture of the end effector 15, the gravity influence amount, and the target position of the end effector 15, and the selected driving algorithm is used to control the driving of the piezoelectric driving device 2F. Thereby, the influence of the gravity G on the piezoelectric driving device 2F can be minimized as much as possible, and the minute movement of the robot 1 can be controlled with high precision.

[0056] Before describing the control method, a situation where the piezoelectric driving device 2F is not easily affected by the gravity G and a situation where it is easily affected by the gravity G will be briefly described. Figure 7 An example showing that it is not easily affected by the gravity G Figure 8 An example showing that it is easily affected by the gravity G.

[0057] In Figure 7 , the fourth rotation axis Jθ4 is along the vertical direction V. In this case, in the operation of rotating the end effector 15 around the fourth rotation axis Jθ4, regardless of the current position and the target position of the end effector 15, the gravity influence amount received by the piezoelectric driving device 2F is constant. In contrast, in Figure 8 , the fourth rotation axis Jθ4 is along the horizontal direction H. In this case, the gravity influence amount received by the piezoelectric driving device 2F varies according to the posture of the end effector 15. For example, as shown by the solid line, the gravity influence amount is the smallest when the end effector 15 faces the vertical direction, and as shown by the dashed line, the gravity influence amount is the largest when the end effector 15 faces the horizontal direction.

[0058] In addition, in the example of Figure 8 , the gravity influence amount received by the piezoelectric driving device 2F also varies according to the rotation direction of the end effector 15. For example, as shown by the single dotted line in Figure 9 , when it is desired to rotate the end effector 15 90° upward (counterclockwise) from the current position, the gravity G overcomes the driving force of the piezoelectric driving device 2F. On the contrary, when it is desired to rotate the end effector 15 90° downward (clockwise) from the current position, the gravity G adds to the driving force of the piezoelectric driving device 2F. Thus, in the example of Figure 8 , the gravity influence amount varies according to the current position and the target position of the end effector 15, and accordingly, the driving of the piezoelectric driving device 2F is likely to become unstable. Therefore, it is not easy to perform minute movement control of the end effector 15 with high precision.

[0059] As described above, the position accuracy of the end effector 15 may decrease according to the amount of gravitational influence. Therefore, as described above, in the present embodiment, the optimal drive algorithm is selected based on the attitude of the end effector 15, the amount of gravitational influence, and the target position of the end effector 15, and the selected drive algorithm is used to control the drive of the piezoelectric drive device 2F.

[0060] Next, the drive algorithms preset in the robot 1 will be described. In the present embodiment, as the drive algorithm, as Figures 10 to 12 shown, a first drive mode Dm1 is set. In the first drive mode Dm1, the feed amplitude W1, which is the amplitude of the bending vibration, is made constant, and the separation amplitude W2, which is the amplitude of the longitudinal vibration, is increased. And, as the first drive mode Dm1, a plurality of modes Dm11, Dm12, Dm13 with different feed amplitudes W1 are set. That is, in the present embodiment, three drive modes are set as the drive algorithm.

[0061] According to the first drive mode Dm1, it is easy to generate the required minimum driving force. Therefore, the rotor 22 is not likely to make a sudden and large movement due to excessive driving force, and the stop accuracy is also good. On the contrary, in order to generate the required minimum driving force, the driving force is increased little by little, so it is easily affected by the gravity G at the initial stage of driving. Therefore, in the present embodiment, by selecting a drive mode that has the best degree of influence on the gravity G, that is, a driving force that can achieve an appropriate amount of movement without succumbing to the gravity G, a driving method that is not easily affected by the gravity G and has excellent stop accuracy is provided.

[0062] However, the drive mode set as the drive algorithm is not particularly limited, as long as at least two different drive modes are set.

[0063] In the present embodiment, the feed amplitude W1 is controlled according to the voltage values of the drive signals V1, V3, and the separation amplitude W2 is controlled according to the voltage value of the drive signal V2. Thereby, the control of the amplitudes W1, W2 becomes easy. However, the control method of the amplitudes W1, W2 is not limited thereto. For example, it may also be controlled according to the frequencies and phases of the drive signals V1, V2, V3. In addition, as will be described later, "making the feed amplitude W1 constant" means a state in which the voltage values of the drive signals V1, V3 that control the bending vibration are constant, and the actual amplitude is not necessarily in a constant state. In addition, the above "constant" means not only the case where there is no change over time, but also includes cases where, for example, minute changes that may occur in the circuit structure occur.

[0064] In addition, as Figures 10 to 12As shown, in the first driving mode Dm1, after the piezoelectric actuator 21 is excited to generate bending vibration, longitudinal vibration is excited. Thus, the first driving mode Dm1 is less susceptible to the influence of gravity G. Specifically, in the state where the piezoelectric actuator 21 is excited to generate bending vibration, the transmission part 214 is held in a state of being pressed against the rotor 22 by the force-applying member 23. Therefore, bending deformation of the vibrating part 211 is not allowed, and actually the vibrating part 211 does not generate bending vibration. When this state is compared to a car, it is equivalent to the state of stepping on the brake hard while stepping on the accelerator, preventing the car from starting. In this state, when the piezoelectric actuator 21 is excited to generate longitudinal vibration, the transmission part 214 separates from the rotor 22 due to the longitudinal vibration, and at the same time, the suppressed bending vibration is released, generating an elliptical motion of the transmission part 214. That is, since the time lag from the separation of the transmission part 214 from the rotor 22 to the generation of the driving force is very short (substantially zero), the rotor 22 does not become a free state and is less susceptible to the influence of gravity G.

[0065] In contrast, when longitudinal vibration is excited and then bending vibration is excited, the transmission part 214 separates from the rotor 22 before generating a force to send out the rotor 22. When this state is compared to a car, it is equivalent to the neutral state of not stepping on the accelerator and releasing the brake. Therefore, the rotor 22 becomes a free state and may accidentally move due to the influence of gravity G, resulting in a decrease in the accuracy of the minute movement of the end effector 15.

[0066] Hereinafter, based on Figure 13 A control method for the piezoelectric driving device 2F will be described, which is executed by the control unit 3F of the control device 3. In the control method of the piezoelectric driving device 2F, first, as step S1, the attitude of the end effector 15 is detected based on the output signal of the acceleration sensor 41. Next, as step S2, the gravity influence amount is detected based on the attitude detected in step S1 and the like. It should be noted that in the present embodiment, since three driving modes Dm11, Dm12, and Dm13 are set as driving algorithms, the gravity influence amount is correspondingly classified into three stages of "low", "medium", and "high".

[0067] Next, as step S3, it is determined which classification of "low", "medium", or "high" the gravity influence amount detected in step S2 is. Next, as step S4, based on the classification of the gravity influence amount determined in step S3 and the rotation direction (CW / CCW) of the end effector 15, one is selected from the driving modes Dm11, Dm12, and Dm13 and set as the driving algorithm. For example, as Figure 14 shown, in the case where the gravity influence amount is "low", such as when the end effector 15 rotates counterclockwise from the 9 o'clock position, the driving mode Dm11 with the smallest driving force is selected, as Figure 15As shown, in a case where the amount of gravity influence is "medium", such as when the end effector 15 is rotated counterclockwise from the 4:30 position, the drive mode Dm12 with a medium driving force is selected. As Figure 16 shown, in a case where the amount of gravity influence is "high", such as when the end effector 15 is rotated counterclockwise from the 3 o'clock position, the drive mode Dm13 with the maximum driving force is selected.

[0068] Next, as step S5, the piezoelectric actuator 21 is driven by the set drive algorithm to move the end effector 15 to the target position. Next, as step S6, it is determined whether the end effector 15 has reached the target position. If the determination result is "not reached", the process returns to step S1, and steps S1 to S6 are repeated until the determination result is "reached". Thus, since the drive mode can be switched in real time based on the attitude of the end effector 15 and the amount of gravity influence that change with time, excellent micro-movement accuracy can be achieved. Then, when the determination result is "reached", as step S7, the drive of the piezoelectric drive device 2F is stopped. Thus, the movement of the end effector 15 to the target position is normally completed. According to such a control method, it is not easily affected by the gravity G, and the position deviation of the end effector 15 can be effectively suppressed.

[0069] The robot 1 and the control method of the robot 1 according to the present embodiment have been described above. As described above, the control method of the robot 1 includes: an arm part 141 as a first component; a fourth rotating part 142 as a second component connected to the arm part 141; a piezoelectric drive device 2F as a drive device that rotates or slides the fourth rotating part 142 relative to the arm part 141; and an end effector 15 connected to the fourth rotating part 142. The control method of the robot 1 in which the attitude of the end effector 15 changes due to the drive of the piezoelectric drive device 2F detects the amount of gravity influence indicating the degree of influence of the gravity G received by the end effector 15 based on the output signal from the inertial sensor 4 disposed on the end effector 15, and determines the drive algorithm of the piezoelectric drive device 2F from a plurality of drive modes Dm11, Dm12, Dm13 based on the detected amount of gravity influence, and drives the piezoelectric drive device 2F by the determined drive algorithm. Thus, the drive of the piezoelectric drive device 2F is not easily affected by the gravity G, and the position deviation of the end effector 15 caused by the gravity G can be effectively suppressed.

[0070] In addition, as described above, the drive algorithm is determined based on the amount of gravity influence and the moving direction of the end effector 15 to the target position. Thus, the optimal drive algorithm can be determined.

[0071] In addition, as described above, the piezoelectric drive device 2F causes the fourth rotating portion 142 to rotate about the fourth rotation axis Jθ4 serving as the rotation axis. When viewed from above along the fourth rotation axis Jθ4, the center of gravity of the end effector 15 is separated from the fourth rotation axis Jθ4. Thus, the drive of the piezoelectric drive device 2F is liable to be affected by the gravity G, making the above control method exhibit its effect more significantly.

[0072] In addition, as described above, the drive device is the piezoelectric drive device 2F, and the piezoelectric drive device 2F includes: a vibration portion 211 disposed on one of the arm portion 141 and the fourth rotating portion 142 and including piezoelectric elements 21A to 21F; a rotor 22 as a driven body disposed on the other of the arm portion 141 and the fourth rotating portion 142; and a transmission portion 214 that transmits the vibration of the vibration portion 211 to the rotor 22. By applying power to the piezoelectric elements 21A to 21F, a longitudinal vibration and a bending vibration are synthesized to vibrate the vibration portion 211 and cause the transmission portion 214 to perform an elliptical motion, thereby moving the rotor 22 by the elliptical motion. According to the piezoelectric drive device 2F, the driving force from the piezoelectric actuator 21 is directly transmitted to the rotor 22. Therefore, there is no need for a relay mechanism for relaying and transmitting the driving force, and simplification and miniaturization of the device can be achieved. In addition, a reduction in movement accuracy caused by gaps and insufficient rigidity, which are problems in a relay mechanism such as a speed reducer, substantially disappears, and the robot 1 having excellent driving accuracy is obtained.

[0073] In addition, as described above, there is a first drive mode Dm1 as the drive mode. In the first drive mode Dm1, while the feed amplitude W1, which is the amplitude of the bending vibration, is made constant, the separation amplitude W2, which is the amplitude of the longitudinal vibration, is increased, and a plurality of first drive modes Dm1 with different feed amplitudes W1 are set. According to such a first drive mode Dm1, fine movement control of the fourth rotating portion 142 becomes easy.

[0074] In addition, as described above, in the first drive mode Dm1, the longitudinal vibration is excited after the bending vibration is excited. Thereby, the influence of the gravity G can be further reduced, and the position shift of the end effector 15 can be more effectively suppressed.

[0075] In addition, as described above, the robot 1 includes: an arm 141 as a first component; a fourth rotating part 142 as a second component, connected to the arm 141; a piezoelectric drive device 2F as a drive device, which rotates or slides the fourth rotating part 142 relative to the arm 141; an end effector 15, connected to the fourth rotating part 142; and a control device 3, which controls the drive of the piezoelectric drive device 2F. Further, the control device 3 detects a gravity influence amount indicating the degree of influence of the gravity G received by the end effector 15 based on an output signal from an inertial sensor 4 disposed on the end effector 15, and determines a drive algorithm for the piezoelectric drive device 2F from a plurality of drive modes Dm11, Dm12, Dm13 based on the detected gravity influence amount, and drives the piezoelectric drive device 2F by the determined drive algorithm. Thereby, the drive of the piezoelectric drive device 2F is not easily affected by the gravity G, and the position deviation of the end effector 15 caused by the gravity G can be effectively suppressed.

[0076] <Second Embodiment>

[0077] Figure 17 It is a diagram showing a second drive mode used in the control method of the robot according to the second embodiment. Figure 18 It is a flowchart showing the control method of the robot.

[0078] The robot 1 of this embodiment is the same as the robot 1 of the above-described first embodiment except that the drive modes included in the drive algorithm are different. Therefore, in the following description, this embodiment will be described centering on the differences from the above-described first embodiment, and the description of the same matters will be omitted. In addition, in the drawings of this embodiment, the same reference numerals are assigned to the same structures as those in the above-described embodiment.

[0079] In this embodiment, as the drive algorithm, the first drive mode Dm1 shown in the above-described first embodiment Figure 10 and, as shown in Figure 17 a second drive mode Dm2 in which the feed amplitude W1 is increased and the separation amplitude W2 is increased at the same time are set.

[0080] The first driving mode Dm1 keeps the feeding amplitude W1 constant and only gradually increases the separating amplitude W2. Therefore, it is easy to generate the required minimum driving force. As a result, the rotor 22 is not likely to make a sudden and large movement due to excessive driving force, and the stopping accuracy is also good. On the contrary, since the driving force is increased little by little to generate the required minimum driving force, it is vulnerable to the influence of gravity G at the initial stage of driving. On the other hand, the second driving mode Dm2 gradually increases both the feeding amplitude W1 and the separating amplitude W2. Therefore, although it is vulnerable to the influence of gravity G just after driving, since the rising degree of the driving force is higher than that of the first driving mode Dm1, it is less vulnerable to the influence of gravity G than the first driving mode Dm1 later. On the contrary, since the increasing speed of the feeding amplitude W1 is faster than that of the first driving mode Dm1, the stopping accuracy may be reduced due to excessive driving force according to the rotational speed of the rotor 22, etc. Thus, by switching between the first driving mode Dm1 and the second driving mode Dm2 with opposite characteristics according to the gravity influence amount, it is less vulnerable to the influence of gravity G.

[0081] Next, based on Figure 18 A control method for the piezoelectric driving device 2F will be described. In the control method of the piezoelectric driving device 2F, first, as step S1, the attitude of the end effector 15 is detected based on the output signal of the acceleration sensor 41. Next, as step S2, the gravity influence amount is detected based on the attitude detected in step S1, etc. It should be noted that in the present embodiment, since two driving modes Dm1 and Dm2 are set as the driving algorithms, the gravity influence amount is correspondingly classified into two stages of "low" and "high".

[0082] Next, as step S3, it is determined which classification of "low" or "high" the gravity influence amount detected in step S2 is. Next, as step S4, one of the first driving mode Dm1 and the second driving mode Dm2 is selected based on the classification of the gravity influence amount determined in step S3 and the rotational direction (CW / CCW) of the end effector 15, and is set as the driving algorithm. Specifically, when the gravity influence amount is "low", the first driving mode Dm1 with a small driving force and high micro-movement accuracy is selected, and when the gravity influence amount is "high", the second driving mode Dm2 with a large driving force is selected.

[0083] Next, as step S5, the piezoelectric actuator 21 is driven by a set driving algorithm to move the end effector 15 to the target position. Next, as step S6, it is determined whether the end effector 15 has reached the target position. If the determination result is "not reached", the process returns to step S1, and steps S1 to S6 are repeated until the determination result is "reached". Thus, since the driving mode can be switched in real time based on the attitude of the end effector 15 and the gravity influence amount that change with time, excellent fine movement accuracy can be achieved. Then, when the determination result is "reached", as step S7, the driving of the piezoelectric driving device 2F is stopped. Thus, the movement of the end effector 15 to the target position is normally completed. According to such a control method, it is not easily affected by the gravity G, and the position deviation of the end effector 15 can be effectively suppressed.

[0084] As described above, in the control method of the robot 1 according to the present embodiment, the driving modes include: a first driving mode Dm1 in which the feed amplitude W1, which is the amplitude of the bending vibration, is kept constant while the separation amplitude W2, which is the amplitude of the longitudinal vibration, is increased; and a second driving mode Dm2 in which both the feed amplitude W1 and the separation amplitude W2 are increased. The first driving mode Dm1 easily generates the required minimum driving force. On the other hand, since the driving force is increased little by little, it is easily affected by the gravity G at the initial stage of driving. In contrast, the second driving mode Dm2 is not easily affected by the gravity G. On the other hand, the stop accuracy may be reduced due to excessive driving force. Thus, by setting the first driving mode Dm1 that is easily affected by the gravity G but has high fine movement accuracy, and the second driving mode Dm2 that is not easily affected by the gravity G but has poor fine movement accuracy, the selection of the driving mode corresponding to the gravity influence amount can be performed better. Therefore, the position deviation of the end effector 15 can be effectively suppressed.

[0085] According to the second embodiment described above, the same effects as those of the first embodiment can also be achieved.

[0086] <Third Embodiment>

[0087] Figure 19 It is a diagram showing the robot according to the third embodiment.

[0088] The robot 1 of the present embodiment is the same as the robot 1 of the first embodiment except for the structure of the robotic arm RA. Therefore, in the following description, the present embodiment will be described centering on the differences from the first embodiment, and the same matters will be omitted. In addition, in the drawings of the present embodiment, the same reference numerals are given to the same structures as those of the above embodiments.

[0089] In the present embodiment, based on the above-described first embodiment, the robotic arm RA further includes: a workbench ST as a second component, connected to a fourth rotating portion 142 as a first component; and a piezoelectric driving device 2H as a driving device, which moves the workbench ST relative to the fourth rotating portion 142 in a third linear motion axis Jr3 direction orthogonal to the fourth rotation axis Jθ4. Moreover, an end effector 15 is disposed on the workbench ST. In this case, the piezoelectric driving device 2H is not affected by the gravity G when the third linear motion axis Jr3 faces the horizontal direction, but is affected by the gravity G when the third linear motion axis Jr3 is inclined with respect to the horizontal direction, particularly when it faces the vertical direction. Therefore, by applying the control method of the piezoelectric driving device 2F described in the above embodiment to the control of the piezoelectric driving device 2H in the present embodiment, the driving of the piezoelectric driving device 2H is not easily affected by the gravity G, and the position deviation of the end effector 15 caused by the gravity G can be effectively suppressed.

[0090] According to the third embodiment described above, the same effects as those of the first embodiment can also be achieved.

[0091] As described above, the control method of the robot and the robot of the present invention have been described based on the illustrated embodiments. However, the present invention is not limited thereto, and the structure of each part can be replaced with any structure having the same function. Additionally, any other arbitrary structure can be added to the present invention.

[0092] Moreover, in the above embodiment, a structure using a piezoelectric driving device as a driving device has been described. However, the present invention is not limited thereto, and a driving device other than the piezoelectric driving device can also be used. For example, a driving device combining an electromagnetic motor and a speed reducer can be used.

Claims

1. A control method for a robot, characterized in that: The robot has: A first component; A second component connected to the first component; A driving device that rotates or slides the second component relative to the first component; And An end effector connected to the second component, The attitude of the end effector changes by the driving of the driving device, The control method of the robot detects a gravity influence amount representing the degree of influence of gravity received by the end effector based on an output signal from an inertial sensor disposed on the end effector, and determines a driving algorithm of the driving device from a plurality of driving modes based on the detected gravity influence amount, and drives the driving device by the determined driving algorithm. The driving device has: A vibration part disposed on one of the first component and the second component and having a piezoelectric element; A driven body disposed on the other of the first component and the second component; And A transmission part that transmits the vibration of the vibration part to the driven body, By applying power to the piezoelectric element, a longitudinal vibration and a bending vibration are synthesized, the vibration part vibrates and the transmission part performs an elliptical motion, so that the driven body moves through the elliptical motion. The control method of the robot has a first driving mode as the driving mode, and the first driving mode makes the feed amplitude, which is the amplitude of the bending vibration, constant and increases the separation amplitude, which is the amplitude of the longitudinal vibration. A plurality of the first driving modes are set in such a way that the feed amplitudes are different.

2. The control method for a robot according to claim 1, characterized in that: The driving algorithm is determined based on the gravity influence amount and the moving direction of the end effector to the target position.

3. The control method for a robot according to claim 1 or 2, characterized in that: The driving device rotates the second component around a rotation axis, When viewed from above along the rotation axis, the center of gravity of the end effector is separated from the rotation axis.

4. The control method for a robot according to claim 1, characterized in that: In the first driving mode, the bending vibration is excited and then the longitudinal vibration is excited.

5. The control method for a robot according to claim 1, characterized in that: The control method of the robot further has a second driving mode that increases both the feed amplitude and the separation amplitude.

6. A robot, characterized in that, Having: A first component; A second component connected to the first component; A driving device that rotates or slides the second component relative to the first component; An end effector connected to the second component; And A control device that controls the driving of the driving device, The control device detects a gravity influence amount representing the degree of influence of gravity received by the end effector based on an output signal from an inertial sensor disposed on the end effector, and determines a driving algorithm of the driving device from a plurality of driving modes based on the detected gravity influence amount, and drives the driving device by the determined driving algorithm. The driving device has: A vibrating section, which is disposed on one of the first member and the second member and includes a piezoelectric element; A driven body, which is disposed on the other of the first member and the second member; And A transmission section, which transmits the vibration of the vibrating section to the driven body, By applying an electric current to the piezoelectric element to synthesize a longitudinal vibration and a bending vibration, causing the vibrating section to vibrate and causing the transmission section to perform an elliptical motion, thereby moving the driven body by the elliptical motion, The robot has a first driving mode as the driving mode, and the first driving mode makes a feed amplitude, which is an amplitude of the bending vibration, constant and increases a separation amplitude, which is an amplitude of the longitudinal vibration, A plurality of the first driving modes are set in such a manner that the feed amplitudes are different.

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