Drive device control method and robot system

Abstract

The invention relates to a control method of a driving device and a robot system, and provides a control method of a piezoelectric driving part capable of performing stable starting and a robot system. A control method for a drive device having an ultrasonic actuator and a driven body driven by receiving a driving force from the ultrasonic actuator includes: an activation step of activating the ultrasonic actuator in a first driving mode; a drive mode switching step of switching the drive mode of the ultrasonic actuator to a second drive mode different from the first drive mode when the driven body does not reach a desired drive state at the time of startup; and a drive mode recovery step of switching the drive mode of the ultrasonic actuator from the second drive mode to the first drive mode when the driven body reaches the desired drive state.

Description

Technical Field

[0001] The invention relates to a control method of a driving device and a robot system. Background Art

[0002] For example, the micro-motion mechanism described in Patent Document 1 includes a fixed platform, a guide mounted on the fixed platform, a moving body moving along the guide, a sliding member fixed to the moving body, and an ultrasonic actuator pressed against the sliding member. In such a micro-motion mechanism, the sliding member is sent out by driving the ultrasonic actuator, so that the moving body moves along the guide.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2009-27865

[0004] However, if foreign matter such as dust adheres to the sliding surface of the sliding member or the sliding member and the ultrasonic actuator are stuck due to not being driven for a long time, the start of operation may become unstable or the operation may not start and stable activation may not be possible. Summary of the invention

[0005] The control method of the driving device of the present invention is a control method of the driving device having an ultrasonic actuator and a driven body that receives a driving force from the ultrasonic actuator and is driven, comprising: a starting step of starting the ultrasonic actuator in a first driving mode; a driving mode switching step of switching the driving mode of the ultrasonic actuator to a second driving mode different from the first driving mode when the driven body does not reach the desired driving state at the time of the starting; and a driving mode recovery step of switching the driving mode of the ultrasonic actuator from the second driving mode to the first driving mode when the driven body reaches the desired driving state.

[0006] The robot system of the present invention comprises: a robot having a mechanical arm; a mobile workbench mounted on the mechanical arm and equipped with a driving device; and a tool mounted on the mobile workbench, the driving device comprising: an ultrasonic actuator; a driven body driven by receiving a driving force from the ultrasonic actuator; and a control device controlling the driving of the ultrasonic actuator, the control device starting the ultrasonic actuator in a first driving mode, and when the driven body does not reach a desired driving state at the time of the starting, the control device switches the driving mode of the ultrasonic actuator to a second driving mode different from the first driving mode, and when the driven body reaches the desired driving state, the drive mode of the ultrasonic actuator is switched from the second driving mode to the first driving mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1It is a plan view showing the driving device according to the first embodiment.

[0008] Figure 2 is a top view of the ultrasonic actuator.

[0009] Figure 3 This is an exploded perspective view of the piezoelectric drive unit.

[0010] Figure 4 It is a diagram showing the driving voltage applied to the ultrasonic actuator.

[0011] Figure 5 It is a plan view showing the driving state of the ultrasonic actuator.

[0012] Figure 6 This is a top view showing a state where foreign matter is attached to the slider.

[0013] Figure 7 This is a graph showing the relationship between driving voltage and thrust.

[0014] Figure 8 This is a flowchart showing a method for controlling the drive device.

[0015] Fig. 9 This is a graph showing the relationship between driving frequency and thrust.

[0016] Fig.10 It is a plan view for explaining a control method of a drive device according to a fifth embodiment.

[0017] Fig.11 It is a plan view for explaining a control method of a drive device according to a fifth embodiment.

[0018] Fig.12 It is a plan view for explaining a control method of a drive device according to a fifth embodiment.

[0019] Fig.13 This is a flowchart for explaining a control method of a drive device.

[0020] Fig.14 It is a plan view showing a robot system according to a sixth embodiment.

[0021] Description of Reference Numerals

[0022] 1…driving device; 2…slider; 3…piezoelectric driving portion; 4…ultrasonic actuator; 4A…piezoelectric element; 4B…piezoelectric element; 4C…piezoelectric element; 4D…piezoelectric element; 4E…piezoelectric element; 4F…piezoelectric element; 40…piezoelectric element; 41…vibrating portion; 42…supporting portion; 43…connecting portion; 44…convex portion; 48…piezoelectric element layer; 49…substrate; 6…force applying member; 61…supporting portion; 62…base; 63…plate spring portion; 8…encoder; 9…control device; 1000…robot system; 1100…machine person; 1110…base; 1120…robot arm; 1121…first arm; 1122…second arm; 1123…third arm; 1124…fourth arm; 1125…fifth arm; 1126…sixth arm; 1131…first arm rotation mechanism; 1132…second arm rotation mechanism; 1133…third arm rotation mechanism; 1134…fourth arm rotation mechanism; 1135…fifth arm rotation mechanism; 1136…sixth arm rotation mechanism; 1200…movable workbench; 1210…base; 1220…first workbench; 1230… Second workbench; 1240… first workbench moving mechanism; 1250… second workbench moving mechanism; 1300… tool; 1310… inkjet head; 1400… control unit; Q… foreign matter; S1… starting step; S101… step; S102… step; S103… step; S11… step; S12… step; S13… step; S2… driving mode switching step; S201… step; S202… step; S203… step; S204… step; S21… step; S22… step; S23… step; S24 …step; S25…step; S26…step; S27…step; S28…step; S29…step; S3…drive mode recovery step; Sv…variable range; U…first direction; V…second direction; V1…drive voltage; V2…drive voltage; V3…drive voltage; Va…first voltage value; Vb…second voltage value; Vc…third voltage value; Vmax…voltage value; Vmin…voltage value; f…drive frequency; f1…first frequency; f2…second frequency; f3…third frequency; fr…resonance frequency; θ…phase difference. DETAILED DESCRIPTION

[0023] Hereinafter, a control method of a drive device and a robot system of the present invention will be described in detail based on preferred embodiments shown in the drawings.

[0024] <First Embodiment>

[0025] Figure 1 It is a plan view showing the driving device according to the first embodiment. Figure 2 is a top view of the ultrasonic actuator. Figure 3 This is an exploded perspective view of the piezoelectric drive unit. Figure 4It is a diagram showing the driving voltage applied to the ultrasonic actuator. Figure 5 It is a plan view showing the driving state of the ultrasonic actuator. Figure 6 This is a top view showing a state where foreign matter is attached to the slider. Figure 7 This is a graph showing the relationship between driving voltage and thrust. Figure 8 This is a flowchart showing a method for controlling the drive device.

[0026] It should be noted that, hereinafter, three axes orthogonal to each other are set as the X-axis, the Y-axis, and the Z-axis, the direction along the X-axis is also referred to as the X-axis direction, the direction along the Y-axis is also referred to as the Y-axis direction, and the direction along the Z-axis is also referred to as the Z-axis direction. In addition, the arrow side of each axis is also referred to as the "positive side", and the side opposite to the arrow is also referred to as the "negative side". In addition, the positive side in the Z-axis direction is also referred to as the "upper", and its negative side is also referred to as the "lower", the positive side in the X-axis direction is also referred to as the "front end", and its negative side is also referred to as the "base end".

[0027] Figure 1 The driving device 1 shown has a slider 2 as a driven body that moves linearly in the Y-axis direction, and a piezoelectric driving unit 3 that abuts against the slider 2. In addition, the piezoelectric driving unit 3 has an ultrasonic actuator 4 that abuts against the slider 2, a force applying member 6 that presses the ultrasonic actuator 4 against the slider 2, an encoder 8 that detects the movement amount of the slider 2, and a control device 9 that controls the driving of the ultrasonic actuator 4.

[0028] However, the structure of the driving device 1 is not particularly limited. For example, a plurality of piezoelectric driving units 3 may be provided on the slider 2, and the slider 2 may be linearly moved by driving the plurality of piezoelectric driving units 3. In addition, the driven body may not move linearly like the slider 2, but may rotate like a rotor.

[0029] In addition, if Figure 2 As shown, the ultrasonic actuator 4 includes a vibrating portion 41 , a supporting portion 42 supporting the vibrating portion 41 , a connecting portion 43 connecting the vibrating portion 41 and the supporting portion 42 , and a convex portion 44 protruding from the front end of the vibrating portion 41 and transmitting the vibration of the vibrating portion 41 to the slider 2 .

[0030] The vibration part 41 is a plate-shaped part extending in the XY plane including the X-axis and the Y-axis with the Z-axis direction as the thickness direction. In addition, the vibration part 41 is a rectangle with the X-axis direction as the expansion direction as the long side when viewed from above. In addition, the vibration part 41 is bent and vibrated in an S-shape by expanding and contracting in the X-axis direction while bending in the Y-axis direction. However, the shape of the vibration part 41 is not particularly limited as long as it can exert its function.

[0031] In addition, the vibration part 41 has a driving piezoelectric element 40 that causes the vibration part 41 to perform bending vibration. The piezoelectric element 40 has piezoelectric elements 4A and 4B as first piezoelectric elements, and piezoelectric elements 4C, 4D, 4E, and 4F as second piezoelectric elements. In the center of the vibration part 41, the piezoelectric elements 4A and 4B are arranged in the X-axis direction. In addition, on the positive side of the piezoelectric elements 4A and 4B in the Y-axis direction, the piezoelectric elements 4C and 4D are arranged in the X-axis direction, and on the negative side of the Y-axis direction, the piezoelectric elements 4E and 4F are arranged in the X-axis direction. These piezoelectric elements 4A to 4F expand and contract in the X-axis direction by energizing each other.

[0032] In addition, among the piezoelectric elements 4A to 4F, the piezoelectric elements 4A and 4B are piezoelectric elements for causing the vibration part 41 to perform expansion and contraction vibration in the X-axis direction, and the piezoelectric elements 4C, 4D, 4E, and 4F are piezoelectric elements for causing the vibration part 41 to perform bending vibration in the Y-axis direction. However, the number and arrangement of the piezoelectric elements for driving are not particularly limited.

[0033] like Figure 3 As shown, the vibration part 41 is configured by sandwiching a piezoelectric element layer 48 including the piezoelectric element 40 between a pair of substrates 49, 49. Each substrate 49 is, for example, a silicon substrate.

[0034] In addition, the piezoelectric element 40 is a structure in which a piezoelectric body is sandwiched between a pair of electrodes. The material constituting the piezoelectric body is not particularly limited, and for example, piezoelectric ceramics such as lead zirconate titanate (PZT), barium titanate, lead titanate, potassium niobate, lithium niobate, lithium tantalate, sodium tungstate, zinc oxide, barium strontium titanate (BST), strontium bismuth tantalate (SBT), lead metaniobate, and scandium lead niobate can be used. In addition, as the piezoelectric body, in addition to the above-mentioned piezoelectric ceramics, polyvinylidene fluoride, quartz, etc. can also be used.

[0035] In addition, as the formation method of piezoelectric body, there is no particular limitation, and it can be formed by bulk material, or it can be formed by sol-gel method or sputtering method. In the present embodiment, the piezoelectric body is formed by sol-gel method. Thus, for example, compared with the situation formed by bulk material, a thin piezoelectric body can be obtained, and the thinning of ultrasonic actuator 4 can be realized.

[0036] The convex portion 44 is provided at the front end of the vibration portion 41 and protrudes from the vibration portion 41 toward the positive side in the X-axis direction. In addition, the front end of the convex portion 44 is semicircular and rounded. Figure 1As shown in FIG. 1 , the front end of the protrusion 44 is pressed against the side surface of the slider 2 by the force applying member 6. Therefore, the vibration of the vibrating portion 41 is transmitted to the slider 2 via the protrusion 44. The material constituting the protrusion 44 is not particularly limited, but various ceramics such as zirconium oxide, aluminum oxide, and titanium dioxide can be cited, for example. Thus, the protrusion 44 has excellent durability. However, the structure of the protrusion 44 is not particularly limited.

[0037] The support portion 42 supports the vibration portion 41. Figure 2 As shown in FIG. 4 , the support portion 42 is a U-shape surrounding three sides of the vibration portion 41. Figure 3 As shown, the support portion 42 is formed by sandwiching a spacer having substantially the same thickness as the piezoelectric element layer 48 between a pair of substrates 49, 49. However, the structure of the support portion 42 is not particularly limited as long as the function thereof can be achieved.

[0038] In addition, if Figure 2 As shown, the connection portion 43 connects the portion of the vibrating portion 41 that becomes a node of bending vibration, that is, the central portion in the X-axis direction, to the supporting portion 42. However, the configuration of the connection portion 43 is not particularly limited as long as it can exert its function.

[0039] The ultrasonic actuator 4 as described above is urged toward the slider 2 by the urging member 6, so that the convex portion 44 is pressed against the slider 2. Figure 3 As shown, a pair of the urging members 6 are provided so as to sandwich the ultrasonic actuator 4 from above and below. Each urging member 6 includes a support portion 61 for supporting the ultrasonic actuator 4, a base 62 for fixing the piezoelectric drive unit 3 to the workbench, and a plurality of plate-like spring portions 63 connecting the support portion 61 and the base 62. In the urging member 6 having such a configuration, by fixing the plate-like spring portion 63 to the workbench in a state where the plate-like spring portion 63 is elastically deformed, the convex portion 44 can be pressed against the slider 2 by utilizing the elasticity (restoring force) of the plate-like spring portion 63.

[0040] The force-applying member 6 is a silicon substrate. Thus, a force-applying member 6 having sufficient mechanical strength and elasticity can be obtained. In addition, the force-applying member 6 can be manufactured with high processing accuracy by using a silicon wafer process. In addition, the difference in thermal expansion coefficient with the ultrasonic actuator 4 becomes smaller, and thermal stress can be reduced. Therefore, the bending, deformation, etc. of the ultrasonic actuator 4 can be suppressed. However, the constituent material of the force-applying member 6 is not particularly limited.

[0041] The control device 9 is composed of a computer, for example, and has a processor for processing information, a memory connected to the processor in a communicative manner, and an external interface. In addition, the memory stores a program that can be executed by the processor, and the processor reads and executes the program stored in the memory. Such a control device 9 receives an instruction (hereinafter also referred to as a "drive instruction") from a host computer not shown in the figure, and controls the drive of the ultrasonic actuator 4 while feeding back the output of the encoder 8 to the instruction.

[0042] For example, when Figure 4 When the driving voltage V1 is applied to the piezoelectric elements 4A and 4B, the driving voltage V2 is applied to the piezoelectric elements 4C and 4F, and the driving voltage V3 is applied to the piezoelectric elements 4D and 4E, as shown in FIG. Figure 5 As shown, the vibrating portion 41 performs expansion and contraction vibration in the X-axis direction and bending vibration in the Y-axis direction in an inverted S shape, and these vibrations are synthesized to make the front end of the convex portion 44 perform an elliptical motion that describes an elliptical orbit in the counterclockwise direction as shown by the arrow. As a result, the slider 2 is sent out and moves linearly to the positive side of the Y-axis direction. In addition, when the waveforms of the driving voltages V2 and V3 are switched, the slider 2 moves linearly to the negative side of the Y-axis direction.

[0043] The above is a description of the structure of the drive device 1. Next, a description is given of a control method of the drive device 1. Figure 6 As shown, when foreign matter Q such as dust or dirt adheres to the surface of the slider 2, when the ultrasonic actuator 4 is started, the convex portion 44 will be caught by the foreign matter Q, causing the slider 2 to start to become unstable. In addition, for example, when the stop state continues for a long period of time and causes the convex portion 44 to be fixed to the slider 2, the slider 2 also starts to become unstable. In such a case, the drive device 1 determines that an abnormality has occurred and stops the drive of the ultrasonic actuator 4 urgently (hereinafter also referred to as "error stop"). It should be noted that the above-mentioned "starting to become unstable" also includes the situation where the convex portion 44 cannot pass over the foreign matter Q and the slider 2 does not start to move, or the situation where the movement stops immediately even if it starts.

[0044] Therefore, the drive device 1 of this embodiment has a drive mode that attempts to release the unstable initial movement of the slider 2 at startup due to foreign matter Q or the like. According to such a configuration, the occurrence of an erroneous stop at startup can be suppressed. This will be described in detail below.

[0045] The control device 9 has a first drive mode and a second drive mode as drive modes for driving the ultrasonic actuator 4. Among them, the first drive mode is a normal drive mode, and the ultrasonic actuator 4 is first started in the first drive mode. In contrast, the second drive mode is a drive mode used when the drive of the slider 2 is unstable and does not reach the desired drive state when the ultrasonic actuator 4 is started in the first drive mode. In the following, for the sake of convenience, the situation where the slider 2 reaches the desired drive state when started in the first drive mode is also referred to as a "normal state", and the situation where the desired drive state is not reached is also referred to as an "abnormal state". That is, the second drive mode is a drive mode for eliminating the abnormal state and achieving the normal state.

[0046] The above-mentioned "desired driving state" refers to a state in which the slider 2 reaches a desired moving speed, for example, a moving speed of the slider 2 assumed when driven in the first driving mode, or a threshold value set based on the moving speed. Alternatively, it refers to a state in which the slider 2 reaches a desired moving distance, for example, a moving distance of the slider 2 assumed when driven in the first driving mode, or a threshold value set based on the moving distance. In particular, in this embodiment, it is referred to as a state that satisfies both of these. Thus, an abnormal state can be simply and accurately determined. The moving speed and moving distance of the slider 2 can be obtained based on the output of the encoder 8.

[0047] Here, by Figure 7 As can be seen from the graph shown, the greater the driving voltages V2 and V3, which are voltages for controlling the amplitude of the bending vibration, the greater the force (hereinafter also referred to as "thrust") of the slider 2. In contrast, since the driving voltage V1 is a voltage for controlling the amplitude of the stretching vibration, the thrust hardly changes even if the driving voltage V1 is changed. Therefore, in the present embodiment, the first and second driving modes both control the thrust by setting the driving voltage V1 constant and changing the driving voltages V2 and V3.

[0048] In the first driving mode, the thrust is adjusted by changing the driving voltages V2 and V3 within the variable range Sv from the voltage value Vmin to the voltage value Vmax, thereby increasing or decreasing the moving speed of the slider 2. Here, by setting the variable range Sv to be relatively low, overheating of the ultrasonic actuator 4 caused by overpower can be suppressed. Therefore, failure and shortening of the life of the ultrasonic actuator 4 can be suppressed, and long-term, stable driving can be performed.

[0049] In contrast, in the second driving mode, the driving voltages V2 and V3 are set higher than the variable range Sv of the first driving mode. Therefore, a higher thrust than that in the first driving mode can be obtained, and even if a foreign object Q is attached to the slider 2, the convex portion 44 can easily pass over the foreign object Q, and the convex portion 44 is also less likely to be caught by the foreign object Q. Therefore, the possibility of the slider 2 starting to move smoothly increases. In other words, the possibility of being able to resolve the abnormal state and transfer to the normal state increases, and the occurrence of erroneous stop can be more effectively suppressed.

[0050] In particular, in the second driving mode of the present embodiment, there is a first voltage value Va, a second voltage value Vb greater than the first voltage value Va, and a third voltage value Vc greater than the second voltage value Vb. In addition, in the second driving mode, first, the ultrasonic actuator 4 is driven with the first voltage value Va to try to resolve the abnormal state. If the abnormal state is not resolved by the first voltage value Va, the ultrasonic actuator 4 is driven with the second voltage value Vb to try to resolve the abnormal state again. If the abnormal state is not resolved by the second voltage value Vb, the ultrasonic actuator 4 is driven with the third voltage value Vc to try to resolve the abnormal state again. In this way, by gradually increasing the driving voltages V2 and V3 in the order of Va→Vb→Vc, it is possible to suppress the application of excessive driving voltages V2 and V3 to the ultrasonic actuator 4 that are greater than the magnitude that can resolve the abnormal state, thereby effectively suppressing the overheating of the ultrasonic actuator 4. In addition, even if the driving voltage V1 that does not affect the thrust is not changed, the overheating of the ultrasonic actuator 4 can be effectively suppressed. In addition, it is also possible to suppress the runaway of the slider 2.

[0051] However, the second driving mode is not particularly limited, and the driving voltages V2 and V3 may be fixed to any one of the first voltage value Va, the second voltage value Vb, and the third voltage value Vc. In addition, the driving voltages V2 and V3 may be continuously increased from the first voltage value Va to the third voltage value Vc.

[0052] The following is based on Figure 8 The flowchart shown in FIG. 1 specifically describes the control method of the driving device 1. The control method of the driving device 1 includes: a starting step S1, starting the ultrasonic actuator 4 in the first driving mode; a driving mode switching step S2, switching the driving mode of the ultrasonic actuator 4 to the second driving mode when the slider 2 does not reach the desired driving state at the time of starting; and a driving mode recovery step S3, switching the driving mode of the ultrasonic actuator 4 to the first driving mode when the slider 2 reaches the desired driving state.

[0053] 《Start Step S1》

[0054] In the start-up step S1, as step S11, the control device 9 first starts the ultrasonic actuator 4 in the first drive mode to start the movement of the slider 2. Then, as step S12, the control device 9 detects the moving speed and moving distance of the slider 2 based on the output of the encoder 8. There is no particular limitation on the detection method of the moving speed, but for example, the slider 2 can be moved a predetermined distance, and the moving speed can be detected based on the time taken for the movement. In addition, there is no particular limitation on the detection method of the moving distance, but the slider 2 can be driven for a predetermined time and detected as the distance moved during the time. Then, as step S13, the control device 9 determines whether the slider 2 is in a normal state or an abnormal state based on the detected moving speed and moving distance. When the slider 2 is in a normal state, the control device 9 directly continues the drive in the first drive mode. On the contrary, when the slider 2 is in an abnormal state, the control device 9 transfers to the drive mode switching step S2.

[0055] 《Drive mode switching step S2》

[0056] In the drive mode switching step S2, as step S21, the control device 9 first switches the drive mode of the ultrasonic actuator 4 from the first drive mode to the second drive mode, and sets the drive voltages V2 and V3 to the first voltage value Va. As a result, a thrust greater than that in the first drive mode is generated, and an attempt is made to change the slider 2 from an abnormal state to a normal state. Then, as step S22, the control device 9 detects the moving speed and moving distance of the slider 2 based on the output of the encoder 8. Then, as step S23, the control device 9 determines whether the slider 2 is in a normal state or an abnormal state based on the detected moving speed and moving distance. When the slider 2 is in a normal state, the control device 9 transfers to the drive mode recovery step S3.

[0057] On the contrary, when the slider 2 is still in the abnormal state, as step S24, the control device 9 sets the drive voltages V2 and V3 to the second voltage value Vb. Thus, the thrust is further increased, and the slider 2 is attempted to be changed from the abnormal state to the normal state. Then, as step S25, the control device 9 detects the moving speed and moving distance of the slider 2 based on the output of the encoder 8. Then, as step S26, the control device 9 determines whether the slider 2 is in the normal state or the abnormal state based on the detected moving speed and moving distance. When the slider 2 is in the normal state, the control device 9 transfers to the drive mode recovery step S3.

[0058] On the contrary, when the slider 2 is still in an abnormal state, as step S27, the control device 9 sets the drive voltages V2 and V3 to the third voltage value Vc. Thus, the thrust is further increased, and the slider 2 is attempted to be changed from an abnormal state to a normal state. Next, as step S28, the control device 9 detects the moving speed and moving distance of the slider 2 based on the output of the encoder 8. Next, as step S29, the control device 9 determines whether the slider 2 is in a normal state or an abnormal state based on the detected moving speed and moving distance. When the slider 2 is in a normal state, the control device 9 transfers to the drive mode recovery step S3. On the contrary, when the slider 2 is still in an abnormal state, since the drive voltages V2 and V3 cannot be increased to a degree above this, the control device 9 stops the ultrasonic actuator 4 due to an error.

[0059] 《Drive mode recovery step S3》

[0060] In the drive mode recovery step S3, the control device 9 switches the drive mode of the ultrasonic actuator 4 from the second drive mode to the first drive mode. As a result, the drive voltages V2 and V3 can be suppressed, thereby effectively suppressing overheating of the ultrasonic actuator 4. It should be noted that since the moving speed of the slider 2 is high enough when switching to the first drive mode, the slider 2 will not return to the abnormal state again by switching to the first drive mode. According to the control method as described above, even if the slider 2 is in an abnormal state in the startup step S1, it is possible to try to resolve the abnormal state and return to a normal state, so the occurrence of an erroneous stop during startup can be suppressed.

[0061] The control method of the driving device 1 is described in detail above. As described above, the control method of the driving device 1 is a control method of the driving device 1 having an ultrasonic actuator 4 and a slider 2 as a driven body that receives a driving force from the ultrasonic actuator 4 and is driven, and includes: a starting step S1, starting the ultrasonic actuator 4 in a first driving mode; a driving mode switching step S2, when the slider 2 does not reach the desired driving state at the time of starting, switching the driving mode of the ultrasonic actuator 4 to a second driving mode different from the first driving mode; and a driving mode recovery step S3, when the slider 2 reaches the desired driving state, switching the driving mode of the ultrasonic actuator 4 from the second driving mode to the first driving mode. Thus, even if the slider 2 is in an abnormal state in the starting step S1, it is possible to try to resolve the abnormal state and return to a normal state, thereby suppressing the occurrence of an erroneous stop at the time of starting.

[0062] In addition, as described above, the desired driving state refers to the state in which the slider 2 reaches the desired moving distance or moving speed. Thus, the abnormal state can be easily and accurately determined.

[0063] In addition, as mentioned above, the driving voltages V2 and V3 of the second driving mode are greater than the driving voltages V2 and V3 of the first driving mode in the starting step S1. As a result, a higher thrust than that in the starting step S1 can be obtained, and the possibility of the abnormal state being resolved and returning to the normal state is increased. Therefore, the occurrence of erroneous stop can be more effectively suppressed.

[0064] As described above, the variable range Sv of the driving voltages V2 and V3 in the second driving mode is larger than that in the first driving mode. Therefore, the driving voltages V2 and V3 in the second driving mode can be made larger than the driving voltages V2 and V3 in the start step S1 more reliably.

[0065] In addition, as described above, the ultrasonic actuator 4 includes a vibration part 41, piezoelectric elements 4A and 4B as first piezoelectric elements for causing the vibration part 41 to perform stretching vibration, and piezoelectric elements 4C, 4D, 4E and 4F as second piezoelectric elements for causing the vibration part 41 to perform bending vibration. Furthermore, the driving voltages V2 and V3 of the piezoelectric elements 4C, 4D, 4E and 4F in the second driving mode are greater than the driving voltages V2 and V3 of the piezoelectric elements 4C, 4D, 4E and 4F in the first driving mode in the start step S1. Thus, the thrust generated in the second driving mode can be made greater than the thrust generated in the first driving mode by simple control.

[0066] <Second Embodiment>

[0067] The drive device 1 of this embodiment is the same as the drive device 1 of the first embodiment except that the control method thereof is different. It should be noted that in the following description, the drive device 1 of this embodiment is described mainly with respect to the differences from the first embodiment, and the description of the same matters is omitted.

[0068] In the aforementioned first embodiment, the driving voltages V2 and V3 of the second driving mode are made larger than the driving voltages V2 and V3 of the first driving mode to increase the thrust of the second driving mode, thereby attempting to resolve the abnormal state. In contrast, in the present embodiment, the driving voltage V1 of the second driving mode is made larger than the driving voltage V1 of the first driving mode to increase the amplitude of the stretching vibration of the convex portion 44 in the second driving mode, thereby attempting to resolve the abnormal state by making it easier for the convex portion 44 to pass over the foreign matter Q.

[0069] Specifically, the larger the driving voltage V1 is, the larger the amplitude of the stretching vibration of the convex portion 44 is. Therefore, the driving voltage V1 of the second driving mode is set higher than the driving voltage V1 of the first driving mode. Thus, in the second driving mode, the convex portion 44 vibrates more in the X-axis direction than in the first driving mode, so that the convex portion 44 easily passes over the foreign matter Q. Therefore, the possibility of the abnormal state being resolved and becoming a normal state increases, and the occurrence of an erroneous stop during startup can be more effectively suppressed.

[0070] It should be noted that, in the driving mode switching step S2, as in the aforementioned first embodiment, there is a first voltage value, a second voltage value greater than the first voltage value, and a third voltage value greater than the second voltage value. And, first, the ultrasonic actuator 4 is driven with the first voltage value to try to resolve the abnormal state. In the case where the abnormal state is not resolved by the first voltage value, the ultrasonic actuator 4 is driven with the second voltage value to try to resolve the abnormal state again. In the case where the abnormal state is not resolved by the second voltage value, the ultrasonic actuator 4 is driven with the third voltage value to try to resolve the abnormal state again. In this way, by gradually increasing the driving voltage V1, it is possible to suppress the application of an excess driving voltage V1 to the ultrasonic actuator 4 that is greater than the magnitude that can resolve the abnormal state, thereby effectively suppressing overheating of the ultrasonic actuator 4. In addition, even if the driving voltages V2 and V3 are not changed, overheating of the ultrasonic actuator 4 can be effectively suppressed.

[0071] However, the second driving mode is not particularly limited, and may be fixed to any one of the first voltage value, the second voltage value, and the third voltage value. In addition, the driving voltage V1 may be continuously increased from the first voltage value to the third voltage value.

[0072] According to the second embodiment as described above, it is possible to achieve the same effects as those of the first embodiment described above.

[0073] <Third Embodiment>

[0074] Fig. 9 This is a graph showing the relationship between driving frequency and thrust.

[0075] The drive device 1 of this embodiment is the same as the drive device 1 of the first embodiment except that the control method thereof is different. It should be noted that in the following description, the drive device 1 of this embodiment is described with the focus on the differences from the first embodiment, and the description of the same matters is omitted. In addition, in the drawings of this embodiment, the same reference numerals are used for the same configurations as those of the above-mentioned embodiment.

[0076] In this embodiment, the frequency of the driving voltages V1, V2, and V3 in the second driving mode is changed from the frequency of the driving voltages V1, V2, and V3 in the first driving mode to attempt to transition from an abnormal state to a normal state. A specific description is given below, but for ease of description, the frequency of the driving voltages V1, V2, and V3 is referred to as "driving frequency f".

[0077] like Fig. 9 As shown, the thrust is maximum when the driving frequency f is consistent with the resonance frequency fr of the ultrasonic actuator 4. In addition, the thrust drops sharply on the low frequency side of the resonance frequency fr, and the thrust drops slowly on the high frequency side of the resonance frequency fr. Therefore, in the first driving mode, the driving frequency f is set near the resonance frequency fr and closer to the high frequency side than the resonance frequency fr. As a result, the movement speed of the slider 2 changes slowly relative to the driving frequency f, and the movement speed of the slider 2 can be controlled with high precision. In addition, a sufficient margin is set between the driving frequency f and the resonance frequency fr so that even if the resonance frequency fr changes during driving, the relationship of the resonance frequency fr < the driving frequency f is maintained.

[0078] In contrast, in the second drive mode, the drive frequency f is lower than that in the first drive mode and closer to the resonance frequency fr. This generates a greater thrust than in the first drive mode, increases the possibility of the abnormal state being resolved and returning to the normal state, and can more effectively suppress the occurrence of erroneous stops during startup.

[0079] In particular, in the drive mode switching step S2, there is a first frequency f1, a second frequency f2 closer to the resonance frequency fr than the first frequency f1, and a third frequency f3 closer to the resonance frequency fr than the second frequency f2. And, first, the ultrasonic actuator 4 is driven at the first frequency f1 to try to resolve the abnormal state. In the case where the abnormal state is not resolved by the first frequency f1, the ultrasonic actuator 4 is driven at the second frequency f2 to try to resolve the abnormal state again. In the case where the abnormal state is not resolved by the second frequency f2, the ultrasonic actuator 4 is driven at the third frequency f3 to try to resolve the abnormal state again. In this way, by gradually making the drive frequency f close to the resonance frequency fr, it is possible to suppress the slider 2 from losing control.

[0080] However, the second driving mode is not particularly limited, and the driving frequency f may be fixed to any one of the first frequency f1, the second frequency f2, and the third frequency f3. In addition, the driving frequency f may be continuously changed from the first frequency f1 to the third frequency f3.

[0081] As described above, in the control method of the driving device 1 of the present embodiment, in the second driving mode, the driving frequency f of the ultrasonic actuator 4 is changed to a frequency close to the resonance frequency fr of the ultrasonic actuator 4. As a result, a thrust greater than that in the first driving mode is generated, and the possibility of the slider 2 returning to the normal state from the abnormal state increases. Therefore, the occurrence of an erroneous stop can be more effectively suppressed.

[0082] According to the third embodiment, the same effects as those of the first embodiment can be achieved.

[0083] <Fourth Embodiment>

[0084] The drive device 1 of this embodiment is the same as the drive device 1 of the first embodiment except that the control method thereof is different. It should be noted that in the following description, the drive device 1 of this embodiment is described mainly with respect to the differences from the first embodiment, and the description of the same matters is omitted.

[0085] In this embodiment, the phase difference of the driving voltages V1, V2, and V3 in the second driving mode is changed from the phase difference of the driving voltages V1, V2, and V3 in the first driving mode to attempt to shift from the abnormal state to the normal state. Specifically, while the phase difference of the driving voltages V2 and V3 is fixed to about 180°, the phase difference θ (refer to Figure 4 ) changes. By changing the phase difference θ, the elliptical orbit of the convex portion 44 changes, so that when the slider 2 starts to move, the convex portion 44 is less likely to be caught by the foreign matter Q and there is a possibility that it is easy to pass over. Therefore, the possibility of relieving the abnormal state and returning to the normal state increases, and the occurrence of erroneous stop can be more effectively suppressed.

[0086] As described above, in the control method of the driving device 1 of the present embodiment, the ultrasonic actuator 4 has a vibrating portion 41, piezoelectric elements 4A and 4B that make the vibrating portion 41 perform stretching vibration, and piezoelectric elements 4C, 4D, 4E, and 4F that make the vibrating portion 41 perform bending vibration. In addition, in the second driving mode, the phase difference θ between the driving voltage V1 of the piezoelectric elements 4A and 4B and the driving voltage V2 and V3 of the piezoelectric elements 4C, 4D, 4E, and 4F is changed. In this way, by changing the phase difference θ, the elliptical orbit of the convex portion 44 changes, so that the convex portion 44 is difficult to be stuck by the foreign matter Q when the slider 2 starts to move, and there is a possibility that it is easy to pass over. Therefore, the possibility of the abnormal state being resolved and becoming the normal state is increased, and the occurrence of erroneous stop can be more effectively suppressed.

[0087] According to the fourth embodiment, it is possible to achieve the same effects as those of the first embodiment described above.

[0088] <Fifth Embodiment>

[0089] Figures 10 to 12 Each of them is a plan view for explaining a control method of a drive device according to the fifth embodiment. Fig.13 This is a flowchart for explaining a control method of a drive device.

[0090] The drive device 1 of this embodiment is the same as the drive device 1 of the first embodiment except that the control method thereof is different. It should be noted that in the following description, the drive device 1 of this embodiment is described with the focus on the differences from the first embodiment, and the description of the same matters is omitted. In addition, in the drawings of this embodiment, the same reference numerals are used for the same configurations as those of the above-mentioned embodiment.

[0091] For example, Fig.10 As shown, even if the ultrasonic actuator 4 is driven in a state where the protrusion 44 is in contact with the foreign matter Q attached to the slider 2, in order to send the slider 2 to the positive side in the Y-axis direction, there is a situation where the momentum of the slider 2 is insufficient and the protrusion 44 cannot pass over the foreign matter Q, resulting in the slider 2 not starting to move.

[0092] Therefore, in this embodiment, if Fig.11 As shown in FIG. 1 , the slider 2 is temporarily moved to the side opposite to the moving direction in the start step S1, that is, the negative side in the Y-axis direction, so that the convex portion 44 and the foreign matter Q are sufficiently separated. Fig.12 As shown in FIG. 1 , the slider 2 is sent to the positive side in the Y-axis direction. As a result, the moving speed of the slider 2 is sufficiently increased before the convex portion 44 contacts the foreign matter Q, and the convex portion 44 easily passes over the foreign matter Q due to the momentum. Therefore, the possibility of relieving the abnormal state and returning to the normal state increases, and the occurrence of erroneous stop can be more effectively suppressed.

[0093] The following is based on Fig.13 The flowchart shown in FIG. 1 specifically describes the control method of the drive device 1. The control method of the drive device 1 is the same as the first embodiment described above, and includes a start-up step S1, a drive mode switching step S2, and a drive mode recovery step S3.

[0094] 《Start Step S1》

[0095] In the start-up step S1, as step S101, the control device 9 first starts the ultrasonic actuator 4 in the first drive mode to start the movement of the slider 2. Then, as step S102, the control device 9 detects the moving speed and moving distance of the slider 2 based on the output of the encoder 8. Then, as step S103, the control device 9 determines whether the slider 2 is in a normal state or an abnormal state based on the detected moving speed and moving distance. When the slider 2 is in a normal state, the control device 9 directly continues the drive in the first drive mode. On the contrary, when the slider 2 is in an abnormal state, the control device 9 transfers to the drive mode switching step S2.

[0096] 《Drive mode switching step S2》

[0097] In the drive mode switching step S2, the control device 9 switches the drive mode of the ultrasonic actuator 4 from the first drive mode to the second drive mode. In the second drive mode, first, as step S201, the slider 2 is moved in the opposite direction to the start step S1. Then, as step S202, the slider 2 is moved in the same direction as the start step S1. Then, as step S203, the control device 9 detects the moving speed and moving distance of the slider 2 based on the output of the encoder 8. Then, as step S204, the control device 9 determines whether the slider 2 is in a normal state or an abnormal state based on the detected moving speed and moving distance. When the slider 2 is in a normal state, the control device 9 transfers to the drive mode recovery step S3.

[0098] On the contrary, when the slider 2 is still in the abnormal state, the movement amount in the opposite direction is increased compared with the last time, and steps S201 to S204 are repeated a predetermined number of times. Then, when the abnormal state is not resolved after repeating the predetermined number of times, the process stops due to an error.

[0099] 《Drive mode recovery step S3》

[0100] In the drive mode restoring step S3 , the control device 9 switches the drive mode of the ultrasonic actuator 4 from the second drive mode to the first drive mode.

[0101] As described above, in the second drive mode of the present embodiment, after the ultrasonic actuator 4 is driven so as to move the slider 2 in the direction opposite to the moving direction in the start step S1, the ultrasonic actuator 4 is driven so as to move the slider 2 in the same direction as the moving direction in the start step S1. Thus, in the drive mode switching step S2, the moving speed of the slider 2 can be sufficiently increased before the convex portion 44 contacts the foreign matter Q, and the convex portion 44 can easily pass over the foreign matter Q due to the momentum. Therefore, the possibility of the abnormal state being resolved and returning to the normal state increases, and the occurrence of an erroneous stop can be more effectively suppressed.

[0102] According to the fifth embodiment, the same effects as those of the first embodiment can be achieved.

[0103] <Sixth Implementation Method>

[0104] Fig.14 It is a plan view showing a robot system according to a sixth embodiment.

[0105] Fig.14 The robot system 1000 shown has a robot 1100, a mobile workbench 1200 mounted on the robot 1100, a tool 1300 mounted on the mobile workbench 1200, and a control unit 1400 for controlling their drive, and is capable of performing operations such as supplying, unloading, conveying and assembling precision equipment and parts constituting the precision equipment.

[0106] The robot 1100 is a six-axis robot with six joints, and includes a base 1110 fixed to a floor or a ceiling, and a robot arm 1120 connected to the base 1110. The robot arm 1120 includes a first arm 1121 rotatably connected to the base 1110, a second arm 1122 rotatably connected to the first arm 1121, a third arm 1123 rotatably connected to the second arm 1122, a fourth arm 1124 rotatably connected to the third arm 1123, a fifth arm 1125 rotatably connected to the fourth arm 1124, and a sixth arm 1126 rotatably connected to the fifth arm 1125. The sixth arm 1126 is provided with a hand connection portion, and the mobile workbench 1200 is mounted on the hand connection portion.

[0107] In addition, the robot 1100 has: a first arm rotation mechanism 1131, which is arranged at the joint portion between the base 1110 and the first arm 1121, so that the first arm 1121 rotates relative to the base 1110; a second arm rotation mechanism 1132, which is arranged at the joint portion between the first arm 1121 and the second arm 1122, so that the second arm 1122 rotates relative to the first arm 1121; a third arm rotation mechanism 1133, which is arranged at the joint portion between the second arm 1122 and the third arm 1123, so that the third arm 1123 rotates relative to the second arm 1121. 22 rotation; the fourth arm rotation mechanism 1134 is arranged at the joint between the third arm 1123 and the fourth arm 1124, so that the fourth arm 1124 rotates relative to the third arm 1123; the fifth arm rotation mechanism 1135 is arranged at the joint between the fourth arm 1124 and the fifth arm 1125, so that the fifth arm 1125 rotates relative to the fourth arm 1124; and the sixth arm rotation mechanism 1136 is arranged at the joint between the fifth arm 1125 and the sixth arm 1126, so that the sixth arm 1126 rotates relative to the fifth arm 1125.

[0108] Furthermore, a driving device 1 is mounted as a power source in a part or all of the first to sixth arm rotation mechanisms 1131 to 1136, and the target arms 1121 to 1126 are rotated by the driving of the driving device 1. Therefore, the robot 1100 can enjoy the effect of the driving device 1 described above, thereby being able to exert high reliability. However, this is not limited to this, and the driving device 1 may not be mounted in any of the first to sixth arm rotation mechanisms 1131 to 1136.

[0109] The movable workbench 1200 comprises: a base 1210 connected to the hand connection part of the sixth arm 1126; a first workbench 1220, which moves in a first direction U relative to the base 1210; a second workbench 1230, which moves in a second direction V orthogonal to the first direction U relative to the first workbench 1220; a first workbench moving mechanism 1240, which moves the first workbench 1220 in the first direction U relative to the base 1210; and a second workbench moving mechanism 1250, which moves the second workbench 1230 in the second direction V relative to the first workbench 1220.

[0110] Furthermore, a driving device 1 is mounted as a power source on one or both of the first and second workbench moving mechanisms 1240 and 1250, and the workbench 1220 and 1230 of the object are moved by the drive of the piezoelectric driving unit 3. As a result, the effect of the driving device 1 can be enjoyed, so that high reliability can be exerted. For example, when the driving device 1 is mounted on the first workbench moving mechanism 1240, the ultrasonic actuator 4 is fixed to the base 1210, the slider 2 is fixed to the first workbench 1220, and the control device 9 performs the same control as the first embodiment described above. In addition, when the driving device 1 is mounted on the second workbench moving mechanism 1250, the ultrasonic actuator 4 is fixed to the first workbench 1220, the slider 2 is fixed to the second workbench 1230, and the control device 9 performs the same control as the first embodiment described above.

[0111] In addition, a tool 1300 is mounted on the second workbench 1230. The tool 1300 is not particularly limited and varies depending on the content of the target operation, but in this embodiment, it is an inkjet head 1310. In the robot system 1000, the inkjet head 1310 ejects ink to perform a printing operation on the object. As described above, the movable workbench 1200 is interposed between the robot 1100 and the inkjet head 1310. Therefore, for example, when the robot 1100 is stopped, the inkjet head 1310 can be moved by the movable workbench 1200. Thus, a stable printing operation can be performed.

[0112] As described above, the robot system 1000 of the present embodiment includes: a robot 1100 having a robot arm 1120; a mobile workbench 1200 mounted on the robot arm 1120 and equipped with a driving device 1; and a tool 1300 mounted on the mobile workbench 1200. In addition, the driving device 1 includes: an ultrasonic actuator 4; a slider 2 driven by receiving a driving force from the ultrasonic actuator 4; and a control device 9 for controlling the driving of the ultrasonic actuator 4. Furthermore, the control device 9 starts the ultrasonic actuator 4 in a first driving mode, and when the slider 2 does not reach a desired driving state at the time of starting, the driving mode of the ultrasonic actuator 4 is switched to a second driving mode different from the first driving mode, and when the slider 2 reaches a desired driving state, the driving mode of the ultrasonic actuator 4 is switched from the second driving mode to the first driving mode. According to such a configuration, the effect of the piezoelectric driving unit 3 described above can be enjoyed, and the robot system 1000 can be realized with high reliability.

[0113] According to the sixth embodiment, it is possible to achieve the same effects as those of the first embodiment.

[0114] The control method of the drive device and the robot system of the present invention are described above based on the illustrated embodiments, but the present invention is not limited thereto, and the configuration of each part can be replaced with any configuration or process having the same function. In addition, other arbitrary configurations or processes may be added to the present invention. In addition, the various embodiments may be appropriately combined. In addition, in the aforementioned embodiments, the configuration of applying the drive device to the robot system is described, but the drive device can also be applied to various electronic devices that require driving force, such as printers, projectors, etc.

Claims

1. A control method for a driving device, characterized in that: The driving device comprises: an ultrasonic actuator; and a driven body, which is driven by receiving a driving force from the ultrasonic actuator. The control method of the driving device comprises: A starting step of starting the ultrasonic actuator in a first driving mode; a driving mode switching step, in which, when the driven object does not reach a desired driving state at the time of the startup, the driving mode of the ultrasonic actuator is switched to a second driving mode different from the first driving mode; and The driving mode restoring step switches the driving mode of the ultrasonic actuator from the second driving mode to the first driving mode when the driven object reaches the desired driving state.

2. The control method of the driving device according to claim 1, characterized in that: The desired driving state is a state in which the driven object reaches a desired moving distance or moving speed.

3. The control method of the driving device according to claim 1, characterized in that: The driving voltage of the second driving mode is greater than the driving voltage of the first driving mode in the startup step.

4. The control method of the driving device according to claim 3, characterized in that: The driving voltage in the second driving mode has a larger variable range than the driving voltage in the first driving mode.

5. The control method of the driving device according to claim 3 or 4, characterized in that: The ultrasonic actuator includes a vibrating portion, a first piezoelectric element for causing the vibrating portion to perform stretching vibration, and a second piezoelectric element for causing the vibrating portion to perform bending vibration. A driving voltage of the second piezoelectric element in the second driving mode is higher than a driving voltage of the second piezoelectric element in the first driving mode in the startup step.

6. The control method of the driving device according to claim 1, characterized in that: In the second driving mode, the driving frequency of the ultrasonic actuator is changed to be close to the resonance frequency of the ultrasonic actuator.

7. The control method of the driving device according to claim 1, characterized in that: The ultrasonic actuator includes a vibrating portion, a first piezoelectric element for causing the vibrating portion to perform stretching vibration, and a second piezoelectric element for causing the vibrating portion to perform bending vibration. In the second driving mode, a phase difference between a driving voltage of the first piezoelectric element and a driving voltage of the second piezoelectric element is changed.

8. The control method of the driving device according to claim 1, characterized in that: In the second driving mode, after the ultrasonic actuator is driven to move the driven body in a direction opposite to the moving direction in the starting step, the ultrasonic actuator is driven to move the driven body in the same direction as the moving direction in the starting step.

9. A robot system, characterized in that: have: A robot, having a mechanical arm; A mobile workbench, mounted on the mechanical arm, and equipped with a driving device; and A tool, mounted on the mobile workbench, The driving device comprises: an ultrasonic actuator; a driven body that receives a driving force from the ultrasonic actuator and is driven; and a control device that controls the driving of the ultrasonic actuator. The control device activates the ultrasonic actuator in a first driving mode, When the driven object does not reach a desired driving state at the time of the startup, the driving mode of the ultrasonic actuator is switched to a second driving mode different from the first driving mode, When the driven object reaches the desired driving state, the driving mode of the ultrasonic actuator is switched from the second driving mode to the first driving mode.

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