Control devices and robots

Abstract

The present invention provides a control device and robot capable of stopping a contact object at a target stop position quickly and accurately. [Solution] A drive device having a vibrating body and a contact body in contact with the vibrating body, wherein the control device causes the vibrating body to vibrate in order to move the vibrating body and the contact body relative to each other, the period from the start of the relative movement until the contact body reaches a target stop position includes a first period and a second period following the first period, wherein the drive of the vibrating body is controlled based on the difference between a first target position located before the target stop position and the current position and the actual speed of the relative movement, and the drive of the vibrating body is controlled based on the difference between a second target position located closer to the target stop position than the first target position and the current position and an arbitrarily set virtual speed of the relative movement.

Description

Technical Field

[0001] The present invention relates to a control device and a robot.

Background Art

[0002] Patent Document 1 describes a vibrating body including a piezoelectric element, a contact body in contact with the vibrating body, and a drive control unit that controls driving of the vibrating body. The drive control unit drives the vibrating body with an alternating current signal, and a relative movement unit that relatively moves the contact body with respect to the vibrating body is described. Further, the drive control unit controls the pulse duty of the signal to be converted into an alternating current signal based on the difference between the target stop position, which is the final stop position of the contact body, and the current position of the contact body and the actual speed of the contact body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the final stage of positioning, that is, near the target stop position, the actual speed of the contact body significantly decreases. Therefore, in the method of relatively moving the contact body by friction with the vibrating body, unevenness occurs easily in the speed of the moving body. Therefore, when trying to bring the contact body closer to the target stop position based on the actual speed, reciprocating movement across the target stop position, stopping in front, etc. are likely to occur, and it is difficult to stop at the target stop position in a short time.

Means for Solving the Problems

[0005] The control device of the present invention is a control device that relatively moves a vibrating body and a contact body by vibrating the vibrating body in a driving device having the vibrating body and the contact body in contact with the vibrating body, The period from the start of the relative movement until the contact body reaches the target stopping position includes a first period and a second period following the first period. During the first period, the drive of the vibrating body is controlled based on the difference between the first target position located before the target stopping position and the current position, and the actual speed of the relative movement. During the second period, the drive of the vibrating body is controlled based on the difference between the current position and the second target position, which is located closer to the target stop position than the first target position, and an arbitrarily set virtual velocity of the relative movement.

[0006] The robot of the present invention has a movable stage comprising a vibrating body, a contact body in contact with the vibrating body, and a control device that causes the vibrating body and the contact body to move relative to each other by vibrating the vibrating body. The period from the start of the relative movement until the contact body reaches the target stopping position includes a first period and a second period following the first period. During the first period, the control device controls the drive of the vibrating body based on the difference between the current position and a first target position located before the target stop position, and the actual speed of the relative movement. During the second period, the control device controls the drive of the vibrating body based on the difference between the current position and a second target position located closer to the target stop position than the first target position, and an arbitrarily set virtual speed of the relative movement. [Brief explanation of the drawing]

[0007] [Figure 1] This is a plan view of the drive device according to the first embodiment. [Figure 2] This figure shows an example of a drive signal applied to a piezoelectric actuator. [Figure 3] This is a plan view showing the operating state of a piezoelectric actuator. [Figure 4] This is a block diagram showing the configuration of the control device. [Figure 5] This graph shows an example of a slider movement plan. [Figure 6]This graph shows an example of a location profile created by transforming a travel plan. [Figure 7] This is a block diagram showing a control method for a piezoelectric actuator during the first period. [Figure 8] This graph shows one example of a method for determining the virtual speed Vi. [Figure 9] Block diagram showing the control method for a piezoelectric actuator during the second period. [Figure 10] This is a block diagram showing a control method for a piezoelectric actuator during the third period. [Figure 11] This block diagram shows a method for controlling a piezoelectric actuator during the second period when the speed Ve1 is higher than the expected range. [Figure 12] This block diagram shows a method for controlling a piezoelectric actuator during the second period when the speed Ve1 is lower than the expected range. [Figure 13] This graph shows an example of a position profile according to the third embodiment. [Figure 14] This block diagram shows the control method for the piezoelectric actuator 3 during the second period. [Figure 15] This is a side view showing a robot according to the fourth embodiment. [Figure 16] This is a plan view showing the movable stage. [Modes for carrying out the invention]

[0008] The control device and robot of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

[0009] <First Embodiment> FIG. 1 is a plan view of a drive device according to the first embodiment. FIG. 2 is a diagram showing an example of a drive signal applied to a piezoelectric actuator. FIG. 3 is a plan view showing the driving state of the piezoelectric actuator. FIG. 4 is a block diagram showing the configuration of the control device. FIG. 5 is a graph showing an example of a movement plan of the slider. FIG. 6 is a graph showing an example of a position profile created by converting the movement plan. FIG. 7 is a block diagram showing a control method of the piezoelectric actuator in the first period. FIG. 8 is a graph showing an example of a method for determining the virtual speed Vi. FIG. 9 is a block diagram showing a control method of the piezoelectric actuator in the second period. FIG. 10 is a block diagram showing a control method of the piezoelectric actuator in the third period.

[0010] In the following, as shown in FIGS. 1 and 3, three axes orthogonal to each other are defined as the X-axis, Y-axis, and 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. Also, the arrow side of each axis is also referred to as the "plus side", and the side opposite to the arrow is also referred to as the "minus side". Further, the plus side in the Z-axis direction is also referred to as "up", the minus side is also referred to as "down", the plus side in the X-axis direction is also referred to as "tip", and the minus side is also referred to as "base end".

[0011] The drive device 1 shown in FIG. 1 includes a slider 2 as a contact body that linearly moves in the X-axis direction, a piezoelectric actuator 3 as a vibrating body that moves the slider 2 in the X-axis direction, an encoder 4 that detects the position of the slider 2, and a control device 5 that controls the driving of the piezoelectric actuator 3. However, the configuration of the drive device 1 is not particularly limited. For example, a plurality of piezoelectric actuators 3 may be arranged with respect to the slider 2, and the slider 2 may be slid by driving the plurality of piezoelectric actuators 3. Also, the contact body may not be a slider like the slider 2, but may be a rotating body such as a rotor that rotates around the Z-axis, for example.

[0012] The piezoelectric actuator 3 includes a vibrating portion 31, a support portion 32 that supports the vibrating portion 31, a pair of beam portions 33 that connect the vibrating portion 31 and the support portion 32, and a convex portion 34 disposed at the tip of the vibrating portion 31.

[0013] Also, the vibrating portion 31 is rectangular with the longitudinal direction along the X-axis in a plan view from the Z-axis direction. The vibrating portion 31 undergoes a S-shaped bending vibration in the Y-axis direction while undergoing a telescopic vibration in the X-axis direction. Further, the vibrating portion 31 has a piezoelectric element 30 for vibrating the vibrating portion 31 as described above. The piezoelectric element 30 includes piezoelectric elements 3A and 3B that cause the vibrating portion 31 to undergo a telescopic vibration in the X-axis direction, and piezoelectric elements 3C, 3D, 3E, and 3F that cause the vibrating portion 31 to undergo a S-shaped bending vibration in the Y-axis direction. Among these, the piezoelectric elements 3A and 3B are arranged side by side in the X-axis direction at the central portion of the vibrating portion 31. And the piezoelectric elements 3C and 3D are arranged side by side in the X-axis direction on the positive side in the Y-axis direction of the piezoelectric elements 3A and 3B. Conversely, the piezoelectric elements 3E and 3F are arranged side by side in the X-axis direction on the negative side in the Y-axis direction of the piezoelectric elements 3A and 3B. These piezoelectric elements 3A to 3F each expand and contract in the X-axis direction by energization. However, the number and arrangement of the piezoelectric element 30 are not particularly limited.

[0014] The convex portion 34 is provided at the tip of the vibrating portion 31. And the tip of the convex portion 34 is pressed against the slider 2 by a biasing member (not shown). Also, the support portion 32 is U-shaped surrounding three sides, i.e., both sides and the rear side, of the vibrating portion 31. Further, the pair of beam portions 33 connect the vibrating portion 31 and the support portion 32.

[0015] In a piezoelectric actuator 3 with this configuration, for example, when the drive signal V1 shown in Figure 2 is applied to piezoelectric elements 3A and 3B, the drive signal V2 is applied to piezoelectric elements 3C and 3F, and the drive signal V3 is applied to piezoelectric elements 3D and 3E, the vibrating part 31 vibrates by expanding and contracting in the X-axis direction while bending in an inverted S-shape in the Y-axis direction, as shown in Figure 3. These vibrations are combined, causing the tip of the convex part 34 to repeatedly contact and separate from the slider 2, moving in an elliptical orbit counterclockwise as indicated by the arrow. As a result, the slider 2 is pushed out and moves to the positive side in the Y-axis direction. Conversely, when the waveforms of the drive signals V2 and V3 are switched, the tip of the convex part 34 moves in the opposite direction in an elliptical motion, and the slider 2 moves to the negative side in the Y-axis direction. The speed V of the slider 2 can be controlled by the amplitude of the drive signals V2 and V3. Specifically, the larger the amplitude of the drive signals V2 and V3, the faster the speed V of slider 2 becomes, and the smaller the amplitude of the drive signals V2 and V3, the slower the speed V of slider 2 becomes.

[0016] The piezoelectric actuator 3 has been described above, but its configuration is not particularly limited. For example, multiple piezoelectric actuators 3 may be stacked to form a single piezoelectric actuator 3. This results in a piezoelectric actuator 3 that can exert a greater driving force. Furthermore, the vibrating body is not limited to the piezoelectric actuator 3.

[0017] As shown in Figure 4, the control device 5 includes a position command generation unit 51, a position control unit 52, a speed control unit 53, a PWM (Pulse Width Modulation) signal generation unit 54, and a drive signal generation unit 55. The control device 5 controls the speed V of the slider 2 so that the slider 2 reaches the target position in each control cycle. The speed V of the slider 2 depends on the amplitudes of the drive signals V2 and V3, and is hardly dependent on the amplitude of the drive signal V1. Therefore, the control device 5 controls the speed V of the slider 2 by controlling the amplitudes of the drive signals V2 and V3 while keeping the amplitude of the drive signal V1 constant. However, the method of controlling the speed V is not particularly limited. Such a control device 5 is, for example, composed of a computer and includes a processor that processes information, a memory that is communicably connected to the processor, and an external interface. The memory also stores a program that can be executed by the processor, and the processor reads and executes the program stored in the memory, thereby performing the functions of each of the above parts.

[0018] The control device 5 first obtains the target stopping position Pe, which is the destination of the slider 2, that is, the travel distance L1, which is the total travel distance of the slider 2 from the starting position Ps to the target stopping position Pe, and the travel time T1, which is the total travel time from the starting position Ps to the target stopping position Pe, from a host computer or the like (not shown).

[0019] The control device 5 then sets a movement plan for the slider 2 from the starting position Ps to the target stopping position Pe, for example, as shown in Figure 5, based on the preset maximum speed Vmax of the slider 2 and the acquired information. In Figure 5, the horizontal axis is time, the vertical axis is the speed V of the slider 2, and the area of ​​the hatched part is the movement distance L1. The movement plan shown in Figure 5 includes an acceleration period to accelerate the slider 2 to the maximum speed Vmax, a constant speed period to maintain the slider 2 at the maximum speed Vmax, and a deceleration period to decelerate the slider 2 and stop it at the target stopping position Pe, but the movement plan is not limited to this. For example, if the movement distance of the slider 2 is short, the constant speed period may be omitted, and deceleration may start before the slider 2 accelerates to the maximum speed Vmax.

[0020] Next, as shown in Figure 5, the control device 5 divides the period D from when the slider 2 starts moving from the starting position Ps until it reaches the target stopping position Pe into three periods: a first period D1, a second period D2 following the first period D1, and a third period D3 following the second period D2. The first period D1 is set as a period when the speed V of the slider 2 is sufficiently fast and the movement of the slider 2 is stable. On the other hand, the second and third periods D2 and D3 are set as periods when the speed V of the slider 2 is slow and the movement of the slider 2 is likely to become unstable.

[0021] The method for determining the first period D1 is not particularly limited. For example, it may be determined based on at least one of (a) the speed V of the slider 2, i.e., the relative speed of movement between the piezoelectric actuator 3 and the slider 2, (b) the distance L of the slider 2 from the starting position Ps, and (c) the time T of the slider 2's movement from the starting time.

[0022] In the case of the method for determining the first period D1 based on the above (a), for example, the period from when the slider 2 starts to move until the speed V reaches A1% of the maximum speed Vmax during the deceleration period can be defined as the first period D1. According to such a method, the first period D1 can be easily and appropriately determined. A1 can be arbitrarily set by the user. For example, it is preferably set to 1% or more and 20% or less, more preferably set to 5% or more and 15% or less, and even more preferably set to about 10%. According to such values, it is possible to ensure that the first period D1 is sufficiently long while avoiding the period when the movement of the slider 2 becomes unstable.

[0023] As another method for determining the first period D1 based on the above (a), for example, the period from when the slider 2 starts to move until the speed V reaches A2 mm / s during the deceleration period can be defined as the first period D1. That is, in this method, the first period D1 is determined using the absolute value of the speed V instead of the relative value with respect to the maximum speed Vmax as described above. However, A2 < Vmax. According to such a method, the first period D1 can be easily and appropriately determined. A2 can be arbitrarily set by the user. For example, it is preferably set to 10 mm / s or more and 100 mm / s or less, more preferably set to 20 mm / s or more and 50 mm / s or less, and even more preferably set to about 30 mm / s. According to such values, it is possible to ensure that the first period D1 is sufficiently long while avoiding the period when the movement of the slider 2 becomes unstable.

[0024] In the case of the method for determining the first period D1 based on the above (b), for example, the period from when the slider 2 starts moving until the moving distance L of the slider 2 becomes A3% of the total moving distance, which is the moving distance L1, can be defined as the first period D1. According to such a method, the first period D1 can be easily and appropriately determined. A3 can be arbitrarily set by the user. For example, it is preferably set to 80% or more and 95% or less, more preferably set to 85% or more and 95% or less, and even more preferably set to about 90%. According to such numerical values, it is possible to ensure that the first period D1 is sufficiently long while avoiding the period during which the movement of the slider 2 becomes unstable.

[0025] Also, as another method for determining the first period D1 based on the above (b), for example, the period from when the slider 2 starts moving until the moving distance L1 of the slider 2 becomes A4 mm can be defined as the first period D1. That is, in this method, the absolute value of the moving distance L is used to determine the first period D1 instead of the relative value with respect to the moving distance L1, which is the total moving distance as described above. However, A4 < L1. According to such a method, the first period D1 can be easily and appropriately determined. A4 can be arbitrarily set by the user. For example, it is preferably set to 10 mm or more and 100 mm or less, more preferably set to 20 mm or more and 80 mm or less, and even more preferably set to about 50 mm. According to such numerical values, it is possible to ensure that the first period D1 is sufficiently long while avoiding the period during which the movement of the slider 2 becomes unstable.

[0026] In the case of the method for determining the first period D1 based on the above (c), for example, the period from when the slider 2 starts moving until the moving time T of the slider 2 becomes A5% of the total moving time which is the moving time T1 can be set as the first period D1. According to such a method, the first period D1 can be easily and appropriately determined. A5 can be arbitrarily set by the user, but for example, it is preferably set to 80% or more and 95% or less, more preferably set to 85% or more and 95% or less, and even more preferably set to about 90%. According to such numerical values, the first period D1 can be ensured to be sufficiently long while avoiding the period during which the movement of the slider 2 becomes unstable.

[0027] Also, as another method for determining the first period D1 based on the above (c), for example, the period from when the slider 2 starts moving until the moving time T of the slider 2 becomes A6 seconds can be set as the first period D1. That is, in this method, the first period D1 is determined using the absolute value of the moving time T instead of the relative value with the moving time T1 which is the total moving time as described above. However, A6 < T1. According to such a method, the first period D1 can be easily and appropriately determined. A6 can be arbitrarily set by the user, but for example, (T1 - A6) is preferably set to 0.1 seconds or more and 1.0 seconds or less, more preferably set to 0.3 seconds or more and 0.7 seconds or less, and even more preferably set to about 0.5 seconds.

[0028] The method for determining the first period D1 has been described above. Note that the first period D1 may be determined by combining two or more of the above (a), (b), and (c). For example, by combining (a) and (b), the period until the speed V becomes A1% or less of the maximum speed Vmax and the moving distance L of the slider 2 becomes A3% or less of the moving distance L1 may be set as the first period D1.

[0029] Next, the method for determining the second period D2 will be described. The method for determining the second period D2 is not particularly limited. Similar to the method for determining the first period D1 described above, for example, it can be determined based on at least one of (a) the speed V of the slider 2, (b) the moving distance L of the slider 2, and (c) the moving time T of the slider 2.

[0030] In the case of the method for determining the second period D2 based on the above (a), for example, from the end of the first period D1 until the speed V reaches B1% of the maximum speed Vmax, the period can be set as the second period D2. However, B1 < A1. B1 can be arbitrarily set by the user. According to such a method, the second period D2 can be easily and appropriately determined.

[0031] Also, as another method for determining the second period D2 based on the above (a), for example, from the end of the first period D1 until the speed V reaches B2 mm / s, the period can be set as the second period D2. However, B2 < A2. B2 can be arbitrarily set by the user. According to such a method, the second period D2 can be easily and appropriately determined.

[0032] In the case of the method for determining the second period D2 based on the above (b), for example, from the end of the first period D1 until the moving distance L of the slider 2 reaches B3% of the moving distance L1, the period can be set as the second period D2. However, A3 < B3 < 100. B3 can be arbitrarily set by the user. According to such a method, the second period D2 can be easily and appropriately determined.

[0033] Also, as another method for determining the second period D2 based on the above (b), for example, from the end of the first period D1 until the moving distance L of the slider 2 reaches B4 mm, the period can be set as the second period D2. However, A4 < B4 < L1. B4 can be arbitrarily set by the user. According to such a method, the second period D2 can be easily and appropriately determined.

[0034] In the case of the method for determining the second period D2 based on the above (c), for example, from the end of the first period D1 until the moving time T of the slider 2 becomes B5% of the moving time T1, the period can be set as the second period D2. However, A5 < B5 < 100. B5 can be arbitrarily set by the user. According to such a method, the second period D2 can be easily and appropriately determined.

[0035] Also, as another method for determining the second period D2 based on the above (c), for example, from the end of the first period D1 until the moving time T of the slider 2 becomes B6 seconds, the period can be set as the second period D2. However, A6 < B6 < T1. B6 can be arbitrarily set by the user. According to such a method, the second period D2 can be easily and appropriately determined.

[0036] The method for determining the second period D2 has been described above. Similar to the method for determining the first period D1, the second period D2 may be determined by combining two or more of the above (a), (b), and (c).

[0037] Next, the method for determining the third period D3 will be described. The method for determining the third period D3 is not particularly limited. For example, from the end of the second period D2 until the slider 2 reaches the target stop position Pe, the period can be set as the third period D3. According to such a method, the third period D3 can be easily and appropriately determined.

[0038] The method for determining the first, second, and third periods D1, D2, and D3 has been explained above. Next, the control device 5 converts the movement plan shown in Figure 5 into a position profile shown in Figure 6. Then, using the converted position profile, the control device 5 determines the first, second, and third periods D1, D2, and D3 based on (b) above, that is, based on the movement distance L of the slider 2. In the illustrated example, the end of the first period D1 is set to a movement distance L = L1 - 50 mm, and the end of the second period D2 is set to a movement distance L = L1 - 5 mm, but this is not limited to this. Furthermore, the first, second, and third periods D1, D2, and D3 may also be determined by (a) or (c) above, or by other methods.

[0039] Furthermore, the control device 5 determines the target position P of the slider 2 for each control cycle based on the converted graph. Hereinafter, the set target positions P located within the first period D1 will also be referred to as the "first target position P1," and those located within the second period D2 will also be referred to as the "second target position P2." Therefore, the first and second target positions P1 and P2 are located in front of the target stop position Pe, and furthermore, the second target position P2 is located closer to the target stop position Pe than the first target position P1.

[0040] Then, during the first period D1, the control device 5 controls the drive of the piezoelectric actuator 3 as follows: During the first period D1, the control device 5 controls the drive of the piezoelectric actuator 3 based on the difference between the first target position P1 and the current position of the slider 2, and the speed V of the slider 2.

[0041] Specifically, as shown in Figure 7, the position command generation unit 51 identifies the first target position P1 for each control cycle from the first target position P1 determined as described above, and generates a position command 901 that defines the identified first target position P1. The first target position P1 is updated every control cycle. The position control unit 52 first calculates the position deviation 903 by subtracting the position 902 of the slider 2 detected by the encoder 4 from the position command 901. Next, the position control unit 52 calculates the speed command 904 by multiplying the position deviation 903 by the position loop proportional gain Kpp.

[0042] The speed control unit 53 is composed of proportional-integral control and determines a voltage command 907 that matches the speed V of slider 2, which is obtained by differentiating the position 902 of slider 2 with respect to the speed command 904. Specifically, the speed control unit 53 first obtains the speed loop command 906 by subtracting the speed V from the speed command 904. Next, the speed control unit 53 obtains the voltage command 907 by adding an integral term, which is obtained by multiplying the integral value of the speed loop command 906 by the speed loop integral gain Kvi, to the proportional term obtained by multiplying the speed loop command 906 by the speed loop proportional gain Kvp.

[0043] The PWM signal generation unit 54 generates a pulse width command with a duty cycle corresponding to the voltage command 907. The pulse width command includes a pulse signal Pd1 for drive signal V1, a pulse signal Pd2 for drive signal V2, and a pulse signal Pd3 for drive signal V3. The drive signal generation unit 55 generates sinusoidal drive signals V1, V2, and V3 from the pulse signals Pd1, Pd2, and Pd3, and applies them to the piezoelectric actuator 3. As a result, the piezoelectric actuator 3 vibrates as described above, and the slider 2 moves along the planned movement.

[0044] Duty refers to the ratio of Low to High pulse widths and can be changed within the range of 0% to 50%. The closer the Duty of pulse signals Pd1, Pd2, and Pd3 is to 0%, the smaller the amplitude of drive signals V1, V2, and V3 becomes. Conversely, the closer the Duty of pulse signals Pd1, Pd2, and Pd3 is to 50%, the larger the amplitude of drive signals V1, V2, and V3 becomes. Therefore, the closer the Duty of pulse signals Pd2 and Pd3 is to 0%, the slower the speed V of slider 2 becomes. Conversely, the closer the Duty of pulse signals Pd2 and Pd3 is to 50%, the faster the speed V of slider 2 becomes. For pulse signal Pd2, for example, the Duty can be fixed at 50% to maintain a constant voltage value.

[0045] Thus, during the first period D1, the control device 5 controls the movement of the slider 2 based on the position deviation 903, which is the difference between the first target position P1 and the current position 902 of the slider 2, and the speed V of the slider 2, which is the actual relative speed of the slider 2 and the piezoelectric actuator 3. During the first period D1, the speed V is sufficiently fast, so fluctuations in speed V are unlikely to occur. Therefore, during the first period D1, by controlling the drive of the piezoelectric actuator 3 using the speed V, which is the actual speed of the slider 2, the slider 2 can be moved stably and efficiently toward the target stop position Pe.

[0046] Furthermore, during the second period D2, the control device 5 controls the driving of the piezoelectric actuator 3 as follows: During the second period D2, the control device 5 controls the driving of the piezoelectric actuator 3 based on the difference between the second target position P2 and the current position of the slider 2 and an arbitrarily set virtual speed Vi of the slider 2.

[0047] Specifically, as shown in Figure 8, the control device 5 first virtually gradually decreases the speed V at the end of the first period D1, generating a virtual speed transition line G that becomes 0 (zero) at the end of the second period D2. Based on the generated virtual speed transition line G, the control device 5 determines the virtual speed Vi of the slider 2 for each control cycle. In the illustrated example, the virtual speed transition line G is composed of an S-shaped cubic curve, suppressing the abrupt change in speed V at the timing of switching from the first period D1 to the second period D2 and from the second period D2 to the third period D3. As a result, the movement of the slider 2 becomes smooth. However, the virtual speed transition line G is not particularly limited and may be, for example, a quadratic curve or a straight line.

[0048] As shown in Figure 9, the position command generation unit 51 identifies the second target position P2 for the corresponding control cycle from the predetermined second target position P2 for each control cycle, and generates a position command 901 that defines the identified second target position P2. In other words, the second target position P2 is updated every control cycle. The position control unit 52 first calculates the position deviation 903 by subtracting the position 902 of the slider 2 from the position command 901. Next, the position control unit 52 calculates the speed command 904 by multiplying the position deviation 903 by the position loop proportional gain Kpp. The speed control unit 53 first calculates the speed loop command 906 by subtracting the virtual speed Vi for the corresponding control cycle from the speed command 904. In other words, here, instead of feeding back the actual speed V of the slider 2, the virtual speed Vi determined based on the virtual speed transition line G is fed back. Then, pulse signals Pd1, Pd2, and Pd3 are generated in the same manner as in the first period D1 described above, and these are applied to the piezoelectric actuator 3.

[0049] Thus, in the second period D2, the piezoelectric actuator 3 is controlled based on the position deviation 903, which is the difference between the second target position P2 and the current position of the slider 2, and the arbitrarily set virtual speed Vi of the slider 2. The second period D2 is a period close to the target stop position Pe, and the speed V of the slider 2 is slow, making it prone to fluctuations in speed V. In other words, there is a risk that the speed V will fluctuate significantly with each control cycle. Therefore, if speed V is fed back, the movement of the slider 2 is likely to become unstable due to fluctuations in speed V. Thus, in the second period D2, when the speed V is slow, the movement of the slider 2 can be stabilized by using a virtually determined and stable virtual speed Vi instead of the unstable speed V. As a result, the slider 2 can be moved toward the target stop position Pe in a shorter time and with greater precision.

[0050] Furthermore, during the third period D3, the control device 5 controls the drive of the piezoelectric actuator 3 as follows: During the third period D3, the control device 5 sets the virtual speed Vi to 0 (zero) and controls the drive of the piezoelectric actuator 3 based on the difference between the target stop position Pe and the current position of the slider 2 until the slider 2 stops at the target stop position Pe. In other words, the drive of the piezoelectric actuator 3 is controlled solely by position control, without speed control.

[0051] Specifically, as shown in Figure 10, the position command generation unit 51 generates a position command 901 that defines the target stop position Pe for each control cycle. The position control unit 52 first calculates the position deviation 903 by subtracting the position 902 of the slider 2 from the position command 901. Next, the position control unit 52 calculates the speed command 904 by multiplying the position deviation 903 by the position loop proportional gain Kpp. The speed control unit 53 first calculates the speed loop command 906 by subtracting the virtual speed Vi (=0) from the speed command 904. In other words, here, instead of feeding back the actual speed V of the slider 2, the virtual speed Vi (=0) is fed back. Then, pulse signals Pd1, Pd2, and Pd3 are generated in the same manner as in the first period D1 described above and applied to the piezoelectric actuator 3.

[0052] Thus, in the third period D3, the virtual speed Vi is set to 0 (zero), and the drive of the piezoelectric actuator 3 is controlled based on the difference between the target stop position Pe and the current position of the slider 2 until the slider 2 stops at the target stop position Pe. In other words, the control device 5 controls the drive of the piezoelectric actuator 3 using only position control, without speed control. The third period D3 is the period immediately before reaching the target stop position Pe, and the speed V of the slider 2 is slow, making it prone to fluctuations in speed V. That is, there is a risk that the speed V will fluctuate significantly with each control cycle. Therefore, if speed V is fed back, the movement of the slider 2 is likely to become unstable due to fluctuations in speed V. Thus, in the third period D3, when the speed V is slow, the movement of the slider 2 can be stabilized by using a virtual speed Vi set to 0 (zero) instead of the unstable speed V. As a result, back-and-forth movement across the target stop position Pe is less likely to occur, and the slider 2 can be stopped at the target stop position Pe in a shorter time and with greater precision. Furthermore, the phrase "stopping slider 2 at the target stopping position Pe" includes not only the case where the actual stopping position of slider 2 coincides with the target stopping position Pe, but also the case where there is an acceptable margin of error between them.

[0053] The drive device 1 has been described above. The control device 5 of such a drive device 1 is a control device 5 that moves the piezoelectric actuator 3 and the slider 2 relative to each other by vibrating the piezoelectric actuator 3 in a drive device 1 having a piezoelectric actuator 3 which is a vibrating body and a slider 2 which is a contact body that is in contact with the piezoelectric actuator 3. The period D from the start of relative movement until the slider 2 reaches the target stop position Pe includes a first period D1 and a second period D2 following the first period D1. In the first period D1, the drive of the piezoelectric actuator 3 is controlled based on the difference between a first target position P1 located before the target stop position Pe and the current position of the slider 2, and the speed V which is the actual speed of relative movement. In the second period D2, the drive of the piezoelectric actuator 3 is controlled based on the difference between a second target position P2 located closer to the target stop position Pe than the first target position P1 and the current position of the slider 2, and the virtual speed Vi which is an arbitrarily set virtual speed of relative movement. With this configuration, the movement of the slider 2 near the target stopping position Pe is stabilized, and back-and-forth movement across the target stopping position Pe is less likely to occur. Therefore, the slider 2 can be stopped at the target stopping position Pe in a shorter time and with greater precision.

[0054] Furthermore, as mentioned above, the first target position P1 is determined for each control cycle. With this configuration, the slider 2 can be moved more reliably toward the target stop position Pe.

[0055] Furthermore, as mentioned above, the second target position P2 is located between the first target position P1 and the target stop position Pe, and is determined for each control cycle. With this configuration, the slider 2 can be moved toward the target stop position Pe more reliably.

[0056] Furthermore, as mentioned above, period D further includes a third period D3 following the second period D2, and in the third period D3, the control device 5 controls the driving of the piezoelectric actuator 3 based on the difference between the target stop position Pe and the current position of the slider 2. With this configuration, the movement of the slider 2 near the target stop position Pe is stabilized, and back-and-forth movement across the target stop position Pe is less likely to occur. As a result, the slider 2 can be stopped at the target stop position Pe in a shorter time and with greater precision.

[0057] Furthermore, the first period D1 is determined based on at least one of the relative movement speed V, the distance traveled L to the target stopping position Pe, and the travel time T to the target stopping position Pe. With this configuration, the first period D1 can be easily and appropriately determined.

[0058] <Second Embodiment> Figure 11 is a block diagram showing the control method of the piezoelectric actuator during the second period when the speed Ve1 is higher than the assumed range. Figure 12 is a block diagram showing the control method of the piezoelectric actuator during the second period when the speed Ve1 is lower than the assumed range.

[0059] The drive device 1 of this embodiment is the same as that of the first embodiment described above, except that the control method of the piezoelectric actuator 3 in the second period D2 is different. In the following description, this embodiment will be described mainly in terms of the differences from the first embodiment described above, and similar matters will not be described. Also, in the figures of this embodiment, the same reference numerals are used for components that are the same as those in the previously described embodiment.

[0060] In the first embodiment described above, the control device 5 changes the control method of the piezoelectric actuator 3 in the second period D2 according to the actual speed V of the slider 2 at the end of the first period D1. Specifically, the control device 5 determines whether the speed Ve1 at the end of the first period D1 is within a preset assumed range. If the speed Ve1 is within the assumed range, the control device 5 controls the driving of the piezoelectric actuator 3 in the same manner as in the first embodiment described above. Conversely, if the speed Ve1 is higher than the assumed range, the control device 5 controls the driving of the piezoelectric actuator 3 by setting the virtual speed Vi for each control cycle to the same value as the speed Ve1, as shown in Figure 11. On the other hand, if the speed Ve1 is lower than the assumed range, the control device 5 controls the driving of the piezoelectric actuator 3 by setting the virtual speed Vi for each control cycle to 0 (zero), as shown in Figure 12. In this way, by varying the control method of the piezoelectric actuator 3 in the second period D2 according to the speed V at the end of the first period D1, the movement of the slider 2 becomes more stable, and the slider 2 can be stopped at the target stop position Pe in a shorter time.

[0061] This second embodiment can also achieve the same effects as the first embodiment described above.

[0062] <Third Embodiment> Figure 13 is a graph showing an example of a position profile according to the third embodiment. Figure 14 is a block diagram showing the control method of the piezoelectric actuator 3 during the second period.

[0063] The drive device 1 of this embodiment is the same as that of the first embodiment described above, except that the control method of the piezoelectric actuator 3 does not have a third period D3. In the following description, this embodiment will be described mainly in terms of the differences from the first embodiment described above, and similar matters will not be described. Also, in the figures of this embodiment, the same reference numerals are used for components that are the same as those in the previously described embodiment.

[0064] In this embodiment, as shown in Figure 13, the control device 5 divides period D into a first period D1 and a second period D2. In the first period D1, the control device 5 controls the drive of the piezoelectric actuator 3 in the same manner as in the first embodiment described above. On the other hand, in the second period D2, as shown in Figure 14, the control device 5 sets the virtual speed Vi to 0 (zero) and controls the drive of the piezoelectric actuator 3 based on the difference between the target stop position Pe and the current position 902 of the slider 2 until the slider 2 stops at the target stop position Pe. In other words, the second target position P2 is set as the target stop position Pe, and the drive of the piezoelectric actuator 3 is controlled in the same manner as in the third period D3 of the first embodiment described above. This method is effective, for example, when the first period D1 can be set to be longer than in the first embodiment described above, that is, when speed unevenness of the slider 2 at low speeds is less likely to occur compared to the first embodiment described above. With this method, the movement of the slider 2 is stable even at low speeds, and the slider 2 can be stopped at the target stop position Pe in a shorter time.

[0065] As described above, in the control device 5 of this embodiment, the second target position P2 is the target stop position Pe. With this configuration, the movement of the slider 2 is stable even at low speeds, and the slider 2 can be stopped at the target stop position Pe in a shorter time.

[0066] This third embodiment can also achieve the same effects as the first embodiment described above.

[0067] <Fourth Embodiment> Figure 15 is a side view showing the robot according to the fourth embodiment. Figure 16 is a plan view showing the movable stage.

[0068] The robot 1000 shown in Figure 15 can perform tasks such as supplying, removing, transporting, and assembling precision equipment and its constituent parts. The robot 1000 is a 6-axis robot and includes a base 1010 fixed to the floor or ceiling, an arm 1020 rotatably connected to the base 1010, an arm 1030 rotatably connected to the arm 1020, an arm 1040 rotatably connected to the arm 1030, an arm 1050 rotatably connected to the arm 1040, an arm 1060 rotatably connected to the arm 1050, an arm 1070 rotatably connected to the arm 1060, and a movable stage 2000 mounted on the arm 1070.

[0069] For the sake of clarity, in the following explanation, the three mutually orthogonal axes will be referred to as the x-axis, y-axis, and z-axis, with the direction along the x-axis also being called the x-axis direction, the direction along the y-axis being called the y-axis direction, and the direction along the z-axis being called the z-axis direction. Note that the coordinate system composed of these x-axis, y-axis, and z-axis is different from the coordinate system composed of the X-axis, Y-axis, and Z-axis mentioned earlier.

[0070] The movable stage 2000 shown in Figure 16 includes a base 2100, a first movable part 2200 that moves in the x-axis direction relative to the base 2100, and a second movable part 2300 that moves in the y-axis direction relative to the first movable part 2200. The first movable part 2200 and the second movable part 2300 are each composed of a drive unit 1. In the following, to distinguish between the two drive units 1, the drive unit 1 that constitutes the first movable part 2200 will have "a" appended to the end of its reference numeral, and the drive unit 1 that constitutes the second movable part 2300 will have "b" appended to the end of its reference numeral.

[0071] The drive device 1a includes a stage-shaped slider 2a that moves linearly in the x-axis direction relative to the base 2100, a piezoelectric actuator 3a that moves the slider 2a in the x-axis direction, an encoder 4a that detects the position of the slider 2a, and a control device 5a that controls the driving of the piezoelectric actuator 3a. The control device 5a controls the driving of the piezoelectric actuator 3a in the same manner as in the first to third embodiments described above.

[0072] The drive device 1b includes a stage-shaped slider 2b that moves linearly in the y-axis direction relative to the slider 2a, a piezoelectric actuator 3b that moves the slider 2b in the y-axis direction, an encoder 4b that detects the position of the slider 2b, and a control device 5b that controls the driving of the piezoelectric actuator 3b. The control device 5b controls the driving of the piezoelectric actuator 3b in the same manner as in the first to third embodiments described above.

[0073] With such a movable stage 2000, sliders 2a and 2b can be stopped quickly and accurately at the target stopping position Pe.

[0074] As described above, the robot 1000 has a movable stage 2000 which includes a piezoelectric actuator 3 which is a vibrating body, a slider 2 which is a contact body in contact with the piezoelectric actuator 3, and a control device 5 which vibrates the piezoelectric actuator 3 to move the piezoelectric actuator 3 and the slider 2 relative to each other. The period D from the start of relative movement until the slider 2 reaches the target stop position Pe includes a first period D1 and a second period D2 following the first period D1. In the first period D1, the control device 5 controls the driving of the piezoelectric actuator 3 based on the difference between a first target position P1 located before the target stop position Pe and the current position of the slider 2, and the velocity V which is the actual relative movement velocity. In the second period D2, the control device 5 controls the driving of the piezoelectric actuator 3 based on the difference between a second target position P2 located closer to the target stop position Pe than the first target position P1 and the current position of the slider 2, and the virtual velocity Vi which is an arbitrarily set virtual relative movement velocity. With this configuration, the movement of the slider 2 near the target stopping position Pe is stabilized, and back-and-forth movement across the target stopping position Pe is less likely to occur. Therefore, the slider 2 can be stopped at the target stopping position Pe in a shorter time and with greater precision.

[0075] Although the control device and robot of the present invention have been described above based on the illustrated embodiments, the present invention is not limited thereto, and the configuration of each part can be replaced with any configuration having a similar function. Furthermore, other arbitrary configurations may be added to the present invention. Also, each embodiment may be combined as appropriate. [Explanation of Symbols]

[0076] 1...Drive unit, 1a...Drive unit, 1b...Drive unit, 2...Slider, 2a...Slider, 2b...Slider, 3...Piezoelectric actuator, 3A...Piezoelectric element, 3B...Piezoelectric element, 3C...Piezoelectric element, 3D...Piezoelectric element, 3E...Piezoelectric element, 3F...Piezoelectric element, 3a...Piezoelectric actuator, 3b...Piezoelectric actuator, 30...Piezoelectric element, 31...Vibrating part, 32...Support part, 33...Beam part, 34...Convex part, 4...Encoder, 4a...Encoder, 4b...Encoder, 5...Control device, 5a...Control device, 5b...Control device, 51...Position command generation unit, 52...Position control unit, 53...Speed ​​control unit, 54...PWM signal generation unit, 55...Drive signal generation unit, 901...Position command, 902...Position, 903...Position deviation, 904...Speed ​​command, 906...Speed ​​loop command, 9 07...Voltage command, 1000...Robot, 1010...Base, 1020...Arm, 1030...Arm, 1040...Arm, 1050...Arm, 1060...Arm, 1070...Arm, 2000...Movable stage, 2100...Base, 2200...First movable part, 2300...Second movable part, D...Period, D1...First period, D2...Second period, D3...Third period, G...Virtual velocity transition Line, L... Distance traveled, L1... Distance traveled, P... Target position, P1... First target position, P2... Second target position, Pd1... Pulse signal, Pd2... Pulse signal, Pd3... Pulse signal, Pe... Target stop position, Ps... Start position, T... Travel time, T1... Travel time, V... Speed, V1... Drive signal, V2... Drive signal, V3... Drive signal, Ve1... Speed, Vi... Virtual speed, Vmax... Maximum speed

Claims

1. A drive device having a vibrating body and a contact body in contact with the vibrating body, wherein a control device causes the vibrating body to vibrate in order to move the vibrating body and the contact body relative to each other, The period from the start of the relative movement until the contact body reaches the target stopping position includes a first period and a second period following the first period. During the first period, the drive of the vibrating body is controlled based on the difference between the first target position located before the target stopping position and the current position, and the actual speed of the relative movement. The control device is characterized in that, during the second period, it controls the driving of the vibrating body based on the difference between the current position and a second target position located closer to the target stop position than the first target position, and an arbitrarily set virtual velocity of the relative movement.

2. The control method according to claim 1, wherein the first target position is determined for each control cycle.

3. The control device according to claim 1, wherein the second target position is the target stop position.

4. The control method according to claim 1, wherein the second target position is located between the first target position and the target stop position and is determined for each control cycle.

5. The aforementioned period further includes a third period following the second period, The control device according to claim 4, which controls the driving of the vibrating body based on the difference between the target stop position and the current position during the third period.

6. The control device according to claim 1, wherein the first period is determined based on at least one of the speed of the relative movement, the distance traveled to the target stop position, and the time traveled to the target stop position.

7. The first target position is a target position determined for each control cycle, and is determined based on at least one of the relative movement speed, the distance traveled to the target stop position, and the travel time to the target stop position. The second target position is located between the first target position and the target stop position, and is a target position determined for each control cycle. The aforementioned period further includes a third period following the second period, The control device according to claim 1, wherein in the third period, the speed of the relative movement is set to 0 (zero), and the drive of the vibrating body is controlled based on the difference between the target stopping position and the current position.

8. The movable stage comprises a vibrating body, a contact body in contact with the vibrating body, and a control device that causes the vibrating body to vibrate, thereby causing the vibrating body and the contact body to move relative to each other. The period from the start of the relative movement until the contact body reaches the target stopping position includes a first period and a second period following the first period. The robot is characterized in that, during the first period, the control device controls the drive of the vibrating body based on the difference between the current position and a first target position located before the target stop position and the actual speed of the relative movement, and during the second period, the control device controls the drive of the vibrating body based on the difference between the current position and a second target position located closer to the target stop position than the first target position and an arbitrarily set virtual speed of the relative movement.

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