Ultrasonic motor system

Abstract

To provide an ultrasonic motor system in which an ultrasonic motor favorably operates.SOLUTION: An ultrasonic motor system 1 includes: an ultrasonic motor 10; a sensor group 70 acquiring status information on the status of the ultrasonic motor 10; a motor drive circuit 60 configured to apply an A phase AC voltage and a B phase AC voltage to the ultrasonic motor based on a control command value so as to operate the ultrasonic motor 10; and a control unit 20. The control unit 20 acquires target information on the target status of the ultrasonic motor 10 and the status information, determines an optimal drive frequency and phase difference for the drive frequency and phase difference of the AC voltages, by using a learned model that is configured to output information on the optimal drive frequency and phase difference to bring the ultrasonic motor into the target status for the input of the target information and the status information based on the acquired target information and the status information, and outputs the control command value related to the optimal drive frequency and phase difference to the motor drive circuit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ultrasonic motor system. [Background technology]

[0002] Ultrasonic motors have many advantages, such as being small, producing high torque, being very quiet, and providing a large holding force when not energized. However, controlling them is relatively difficult because the motor itself has nonlinear characteristics and many parameters are involved in its operation. For this reason, various studies have been conducted on controlling ultrasonic motors. For example, Patent Document 1 discloses generating a control signal for controlling an ultrasonic motor using a trained model obtained by deep reinforcement learning. Furthermore, Patent Document 2 discloses utilizing the output of a neural network determined by executing a genetic algorithm to control an ultrasonic motor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2023 / 068370 [Patent Document 2] International Publication No. 2007 / 049412 Summary of the Invention [Problem to be solved by the invention]

[0004] SUMMARY OF THE INVENTION An object of the present invention is to improve the operation of an ultrasonic motor. [Means for solving the problem]

[0005] According to one aspect of the present invention, an ultrasonic motor system includes an ultrasonic motor, a sensor that acquires state information regarding the state of the ultrasonic motor, a motor drive circuit configured to apply an A-phase AC voltage and a B-phase AC voltage to the ultrasonic motor based on a control command value to operate the ultrasonic motor, and a control device configured to acquire target information and state information regarding a target state of the ultrasonic motor, and to determine an optimal drive frequency and phase difference using a trained model configured to output information regarding the optimal drive frequency and phase difference for putting the ultrasonic motor into the target state based on the acquired target information and state information, and to output a control command value regarding the optimal drive frequency and phase difference to the motor drive circuit. [Effects of the Invention]

[0006] According to the present invention, the operation of the ultrasonic motor can be improved. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram showing an outline of a configuration example of an ultrasonic motor system according to an embodiment. [Figure 2] FIG. 2 is a diagram showing an outline of a configuration example of a traveling wave type ultrasonic motor according to an embodiment. [Figure 3] FIG. 3 is a diagram showing an example of the relationship between the vibration amplitude and the drive frequency of the stator of the ultrasonic motor. [Figure 4] FIG. 4 is a flowchart showing an outline of an example of the operation of the control device in controlling the ultrasonic motor. [Figure 5] FIG. 5 is a functional block diagram illustrating an outline of a configuration example of a control device according to an embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of deep reinforcement learning. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment will be described with reference to the drawings. The embodiment relates to an ultrasonic motor system. The ultrasonic motor system includes an ultrasonic motor, and is configured to appropriately control the operation of the ultrasonic motor.

[0009] [System Configuration] 1 is a block diagram showing an outline of an example of the configuration of an ultrasonic motor system 1 according to this embodiment. The ultrasonic motor system 1 includes an ultrasonic motor 10, a control device 20, a motor drive circuit 60, and a group of sensors 70.

[0010] <Outline of the ultrasonic motor configuration> The ultrasonic motor 10 may be any type of ultrasonic motor that operates using ultrasonic vibrations, but in this embodiment, it is a rotary traveling wave ultrasonic motor, which is a form of vibration actuator. Figure 2 is a diagram showing an outline of an example of the configuration of the ultrasonic motor 10 according to this embodiment. Figure 2 shows the ultrasonic motor 10 in a cutaway state so that the structure of the ultrasonic motor 10 can be seen.

[0011] The ultrasonic motor 10 is constructed on a plate-shaped base 120, and its main parts are housed inside a cover 180 provided on the base 120. For the sake of explanation, only the rear half of the cover 180 is shown in FIG. 2. Also, for the sake of explanation, only the rear portions of the stator 130, rotor 140, bearing 160, disc spring 170, etc., which will be described later, are shown in FIG. 2 with the front portions cut away. All of these components have an approximate disk shape. The following components are provided in the space surrounded by the base 120 and the cover 180.

[0012] A stator 130 in the shape of an annular plate is fixed on the base 120. A shaft 150 is provided in the center of the stator 130, perpendicular to the base 120. The shaft 150 is rotatably supported by a bearing 160 fixed to a cover 180. A rotor 140 in the shape of an annular plate is fixed to the shaft 150. A contact portion 141 is provided on the outer ring portion of the rotor 140. The rotor 140 is pressed toward the stator 130 by a pressurizing member, such as a disc spring 170, and the contact portion 141 is in pressurized contact with a first surface 133 on the upper side of the stator 130.

[0013] Stator 130 has piezoelectric element 132 fixed to elastic body 131 made of, for example, a metal material. Elastic body 131 is provided on the rotor 140 side, and piezoelectric element 132 is provided on the opposite side. First surface 133 of elastic body 131 that comes into contact with rotor 140 has a comb-like uneven shape in which convex portions and concave portions that extend in the radial direction of annular elastic body 131 are repeatedly provided in the circumferential direction. When elastic body 131 vibrates, the comb-like shape of first surface 133 causes the tops of the convex portions that come into contact with contact portion 141 to undergo large displacement.

[0014] As will be described later, in order to generate a traveling wave with a wavelength λ in elastic body 131, piezoelectric element 132 has, for example, the following configuration. That is, in piezoelectric element 132, A-phase electrodes are provided in predetermined portions of the piezoelectric body, and B-phase electrodes are provided in other portions of the piezoelectric body. The piezoelectric body in the portions where the A-phase electrodes are provided is polarized so that the polarity changes alternately every length equivalent to 1 / 2λ in the circumferential direction. The piezoelectric body in the portions where the B-phase electrodes are provided is similarly polarized so that the polarity changes alternately every length equivalent to 1 / 2λ in the circumferential direction. A gap of a length equivalent to 1 / 4λ or 3 / 4λ is provided in the circumferential direction between the portions where the A-phase electrodes are provided and the portions where the B-phase electrodes are provided.

[0015] When an AC voltage is applied to the A-phase electrode and the B-phase electrode, adjacent sections of the piezoelectric element 132 are polarized in opposite directions, causing one section to expand and the other to contract. This expansion and contraction of the piezoelectric element 132 generates a bending vibration in the elastic body 131. At a predetermined frequency, the stator 130 enters a state close to resonance. When AC voltages with a phase difference of 90° are applied to the A-phase electrode and the B-phase electrode, respectively, the waves generated in the A-phase electrode and the B-phase electrode are combined, generating a traveling wave along the circumferential direction in the elastic body 131. At this time, the contact portion 141 of the rotor 140 is in pressure contact with the first surface 133 of the elastic body 131, so the rotor 140 rotates in the opposite direction to the generated traveling wave. When the rotor 140 rotates, the shaft 150 fixed to the rotor 140 rotates around its axis. In the ultrasonic motor 10, the shaft 150 serves as the output shaft, and the rotation of the shaft 150 is extracted as motor rotation.

[0016] <Outline of the configuration of the control device> As shown in Fig. 1, the control device 20 is a computer including various integrated circuits such as a processor 21, a memory 22, and a storage 23, an input interface (I / F) 24, an output interface (I / F) 25, and a bus line 26 connecting these. The control device 20 operates by these pieces of hardware working together. The specific configuration of the control device 20 may be any. For example, an SoC (System on a Chip) or the like may be used. Various programs and data are recorded in the control device 20, and the control device 20 operates using these programs and the like.

[0017] The control device 20 acquires target information, such as target values ​​for the operation of the ultrasonic motor 10, input from the outside via the input I / F 24. This target value may include values ​​such as the rotation speed, torque, and rotation position of the ultrasonic motor 10. The target information is information relating to the target state of the ultrasonic motor 10. The control device 20 determines a control command value that realizes the input target value. The control device 20 outputs the determined control command value via the output I / F 25. The control command value is transmitted to the motor drive circuit 60.

[0018] The control command value includes, for example, information related to the voltage, frequency, phase, etc. of the AC voltage applied to each of the A-phase electrodes and the B-phase electrodes of the ultrasonic motor 10. If the amplitude and frequency of the AC voltage applied to the A-phase electrodes are the same as those of the AC voltage applied to the B-phase electrodes, the control command value may include a single amplitude and frequency value without distinguishing between the A-phase and the B-phase. Regarding the phase, the control command value may include information related to the phase of each of the AC voltages applied to the A-phase electrodes and the B-phase electrodes, or may include information related to the phase and phase difference of either one of them, or may include information related to the phase difference between a separately prepared periodic reference signal and the AC voltage.

[0019] <Outline of the configuration of the motor drive circuit> The motor drive circuit 60 acquires a control command value from the control device 20. Based on this control command value, the motor drive circuit 60 generates a drive voltage for operating the ultrasonic motor 10 and outputs it to the ultrasonic motor 10. The drive voltage is an AC voltage applied to the A-phase electrodes and an AC voltage applied to the B-phase electrodes of the ultrasonic motor 10. The frequency of the AC voltage is, for example, a frequency corresponding to the ultrasonic waves. The ultrasonic motor 10 is operated by the power output from this motor drive circuit 60.

[0020] <Outline of the sensor group configuration> The sensor group 70 may include various sensors that acquire information about the state of the ultrasonic motor 10.

[0021] The sensor group 70 may include a voltage sensor 71 that acquires a feedback voltage of the ultrasonic motor 10. For example, a piezoelectric element may be provided in the elastic body 131 of the stator 130 of the ultrasonic motor 10, and the voltage generated by this piezoelectric element due to distortion of the elastic body 131 may be acquired as the feedback voltage. Information regarding the characteristics and vibration state of the stator 130 can be obtained from the feedback voltage. A voltage sensor may also be provided separately from this for acquiring the voltage input to the ultrasonic motor 10. The sensor group 70 may include a current sensor 72 that acquires the drive currents for the above-mentioned A phase and B phase that flow through the piezoelectric element 132 of the ultrasonic motor 10. The drive currents may include information regarding the vibration amplitude of the stator 130.

[0022] The sensor group 70 may include an encoder 73 for acquiring the rotation speed, rotation position, etc. of the ultrasonic motor 10. The sensor group 70 may include a temperature sensor 74 for acquiring the temperature of the ultrasonic motor 10. The operation of the ultrasonic motor 10 is dependent on the vibration of the stator 130 at a frequency close to the resonant frequency, and is therefore temperature dependent.

[0023] The sensor group 70 may include a calculator 75 that calculates information such as amplitude and phase based on signals related to voltage and current acquired by the voltage sensor 71 and the current sensor 72. The calculator 75 may calculate information such as the vibration amplitude of the stator 130 of the ultrasonic motor 10 and other information on the state of the ultrasonic motor 10 based on output signals from the various sensors. The function of the calculator 75 may be included in the control device 20.

[0024] The sensor group 70 may include all or some of these sensors, etc. Status information regarding the status of the ultrasonic motor 10, such as output signals of various sensors acquired by the sensor group 70 and signals that have undergone predetermined processing based on the output signals, is input to the control device 20 via the input I / F 24.

[0025] [Ultrasonic motor control] <overview> The following describes the control of the ultrasonic motor 10 in the ultrasonic motor system 1 according to this embodiment. As described above, the ultrasonic motor 10 rotates the rotor 140 by vibrating the stator 130 at a frequency near the resonant frequency.

[0026] FIG. 3 shows an example of a resonance curve of the stator 130. That is, FIG. 3 shows an example of the relationship between the vibration amplitude of the stator 130 and the frequency of the AC voltage applied to the stator 130, i.e., the drive frequency. As shown in FIG. 3, the vibration amplitude of the stator 130 changes depending on the drive frequency. In general, in an ultrasonic motor 10, the vibration amplitude of the stator 130 is adjusted by adjusting the drive frequency, thereby adjusting the rotation speed of the ultrasonic motor 10 to a target value. In this case, the drive frequency is generally changed so that the frequency changes at a constant rate.

[0027] 3, the vibration amplitude and drive frequency of the stator 130 exhibit strong hysteresis. For this reason, in general, when obtaining a vibration amplitude of 2.3 μm indicated by a circle at startup, the drive frequency is swept from a high frequency to a low frequency to reach 42 kHz. If the drive frequency is swept from a low frequency to a high frequency, the vibration amplitude indicated by a square will be 0.8 μm even if the drive frequency is set to 42 kHz, and an appropriate vibration amplitude cannot be obtained. In other words, the drive voltage V applied to the A-phase electrode of the piezoelectric element 132 of the ultrasonic motor 10 A and the driving voltage V applied to the B-phase electrode B and V A = V0sin(2πft) V B = V0sin(2πft + φ) At startup, the drive frequency f is changed over time from a high frequency to a low frequency.

[0028] Furthermore, when changing the rotation speed of the ultrasonic motor 10 after it has been started, the drive frequency is swept to change the vibration amplitude of the stator 130, thereby adjusting the rotation speed of the ultrasonic motor 10 to the desired value. To reverse the rotation of the ultrasonic motor 10, it is sufficient to invert the phase of only one of the drive voltages. To stop the rotation of the ultrasonic motor 10, it is sufficient to stop the application of the AC voltage. While it generally takes only about 1 ms at most to stop an ultrasonic motor, starting an ultrasonic motor can take as long as 50 ms depending on the conditions.

[0029] Generally, as described above, the rotation speed of the ultrasonic motor 10 is controlled by adjusting the drive frequency. In contrast, in the ultrasonic motor system 1 of this embodiment, the rotation speed of the ultrasonic motor 10 is controlled by adjusting the phase difference between the drive voltage applied to the A-phase electrode and the drive voltage applied to the B-phase electrode, in addition to adjusting the drive frequency. Furthermore, the phase of each drive voltage may be adjusted. That is, the drive voltage V applied to the A-phase electrode of the piezoelectric element 132 of the ultrasonic motor 10 of this embodiment A and the driving voltage V applied to the B-phase electrode B and V A = V0sin(2πft + θ) V B = V0sin(2πft + θ + α) The rotation speed of the ultrasonic motor 10 is controlled by adjusting the drive frequency f, the phase θ of the drive voltage, and the phase difference α of the drive voltage.

[0030] When the phase difference α of the drive voltage is ±90°, that is, when the drive voltage V applied to the A-phase electrode is A and the driving voltage V applied to the B-phase electrode BThe ultrasonic motor 10 is designed to generate traveling waves most efficiently when the phase difference α of the drive voltage is shifted by 90°. Therefore, the phase difference α of the drive voltage is generally set to ±90°. In contrast, shifting the phase difference α from ±90° reduces the amplitude of the generated traveling waves, and as a result, reduces the rotation of the ultrasonic motor 10. In this embodiment, the rotation speed of the ultrasonic motor 10 is also adjusted by changing the phase difference α of the drive voltage.

[0031] As is clear from the above equation, changing the phase θ of the drive voltage in the description of this embodiment means shifting the phase by a phase angle θ with respect to a periodically changing reference phase. A When the periodic reference signal of the drive frequency separately prepared for this is set to s = sin(2πft), the drive voltage V applied to the A-phase electrode is A = V0 sin(2πft + θ) has a phase difference θ with respect to a reference signal s, and changing the phase θ of the drive voltage means changing the phase difference θ with respect to the reference signal s. The inventors' studies confirmed that changing the combination of the drive frequency f and the phase θ of the drive voltage allows for more stable control of the rotation speed of the ultrasonic motor 10 than adjusting only the drive frequency f while fixing the phase θ of the drive voltage. Therefore, in this embodiment, the phase θ of the drive voltage may also be changed when adjusting the rotation speed of the ultrasonic motor 10. The phase and phase difference of the drive frequency and the drive voltage may be swept to change at a constant speed, adjusted to change at a variable rate, or adjusted to take discontinuous values.

[0032] Control Method The operation of the ultrasonic motor 10 according to this embodiment will be described below.

[0033] In step S101, the control device 20 externally acquires target values ​​for the operation of the ultrasonic motor 10. The target values ​​for the operation are, for example, values ​​related to the rotation speed of the ultrasonic motor 10, the torque output by the ultrasonic motor 10, the rotation position of the ultrasonic motor 10, etc. In other words, the control device 20 externally acquires target information related to the target state of the ultrasonic motor 10.

[0034] In step S102, the control device 20 acquires status information, such as the output of various necessary sensors, from the sensor group 70. The status information may include all or part of information such as the amplitude, frequency, and phase of the feedback voltage output from the ultrasonic motor 10, the amplitude, frequency, and phase of the A-phase and B-phase drive voltages input to the ultrasonic motor 10, the amplitude, frequency, and phase of the A-phase and B-phase drive currents flowing through the ultrasonic motor 10, the rotation direction, rotation speed, and rotation position of the ultrasonic motor 10, and the temperature of the ultrasonic motor 10. Furthermore, the load torque acting on the ultrasonic motor 10 may be determined based on this information, and this may be included in the status information.

[0035] In step S103, the control device 20 determines an optimum drive voltage that appropriately achieves the target value for the operation of the ultrasonic motor 10 related to the target information in the situation specified by the state information acquired from the sensor group 70. For example, the control device 20 determines the amplitude, frequency, phase (including the phase difference between the A phase and the B phase) and the like of the AC voltages to be applied to the A-phase electrodes and the B-phase electrodes, respectively.

[0036] In step S104, the control device 20 outputs a control command value related to the determined optimum drive voltage to the motor drive circuit 60. Having acquired the control command value, the motor drive circuit 60 outputs a corresponding drive voltage to the ultrasonic motor 10 based on the control command value, thereby operating the ultrasonic motor 10. As a result, the ultrasonic motor 10 operates based on the optimum control method.

[0037] In step S105, the control device 20 determines whether to end the operation based on whether the input of the target value for the operation has been stopped or not. If the target value for the operation has been input and the operation is not to be ended, the process returns to step S101. Thereafter, the above-described process is repeated. On the other hand, if the operation is to be ended, the series of operations ends.

[0038] Machine learning and the like are used to determine the optimal drive voltage in step S103 described above. In this embodiment, the input to the control device 20 includes operation target information and current state information. Furthermore, the output from the control device 20 includes a control command value. Here, the operation target information, current state information, and control command value each include many parameters. For this reason, it is difficult to identify the relationship between input and output where many parameters are related. In such a situation, the use of machine learning and the like is effective. In this embodiment, a trained model is installed in the control device 20.

[0039] 5 is a functional block diagram of the control device 20. As shown in this diagram, the control device 20 has a function as a pre-processing unit 31, a function as a trained model 32, and a function as a post-processing unit 33.

[0040] The preprocessing unit 31 adjusts various data acquired from the sensor group 70 and data related to target information for the operation of the ultrasonic motor 10 input from the outside into data in a format suitable for input to the trained model 32. The data acquired from the sensor group 70 may include data related to the amplitude, frequency, and phase of the feedback voltage output from the ultrasonic motor 10, the amplitude, frequency, and phase of the A-phase and B-phase AC voltages input to the ultrasonic motor 10, the amplitude, frequency, and phase of the A-phase and B-phase AC currents flowing through the ultrasonic motor 10, the rotation direction, rotation speed, and rotation position of the ultrasonic motor 10, the temperature of the ultrasonic motor 10, and the load torque applied to the ultrasonic motor 10. The data related to target information for the operation may include data related to target values ​​such as the rotation speed of the ultrasonic motor 10, the torque output by the ultrasonic motor 10, or the rotation position of the ultrasonic motor 10. The processing of the preprocessing unit 31 includes adjusting the data into a format similar to that of the data used to create the trained model 32.

[0041] The trained model 32 is configured to output control parameter values ​​in response to data input from the preprocessing unit 31. The input data also includes data related to target information for the operation of the ultrasonic motor 10. The control parameter values ​​are data related to the AC voltages to be applied to the A-phase electrodes and B-phase electrodes of the piezoelectric element 132 of the ultrasonic motor 10 in order to achieve the state of the ultrasonic motor 10 related to this target information. The control parameters include the amplitude, frequency, phase (including the phase difference between the A phase and the B phase) of the AC voltages to be applied to the A-phase electrodes and B-phase electrodes, respectively.

[0042] Based on the values ​​of the control parameters output by the trained model 32, the post-processing unit 33 creates a control command value for causing the motor drive circuit 60 to output an AC voltage having the values ​​of the control parameters. The created control command value is output to the motor drive circuit 60. Note that the trained model 32 may be configured to output a control command value in response to input data. In this case, the post-processing unit 33 may be simplified.

[0043] In the ultrasonic motor system 1 according to this embodiment, when target information on the state of the ultrasonic motor input from outside or state information acquired using the sensor group 70 is input to the control device 20 equipped with a trained model, a control command value is output at high speed from the control device 20. This control command value is input to the motor drive circuit 60, and the operation of the ultrasonic motor 10 can be controlled quickly and appropriately by the output of the motor drive circuit 60 based on the control command value.

[0044] The trained model may be created by any machine learning technique, including, but not limited to, deep reinforcement learning.

[0045] 6 is a diagram illustrating an example of deep reinforcement learning. In deep reinforcement learning, for example, a neural network 41 including an input layer, multiple intermediate layers, and an output layer is provided, and this neural network 41 is used by an agent 40 to determine its behavior.

[0046] In this deep reinforcement learning, target information relating to target values ​​of the operating state, such as target rotation speed, torque, and rotation position, and values ​​relating to state information obtained by various sensors in the sensor group 70 and processed by a calculator 75, are input to an input unit 42 corresponding to the pre-processing unit 31. The input unit 42 creates a state signal based on the target information and the state information. This state signal is input to the neural network 41 as a state.

[0047] The values ​​of control parameters such as the amplitude, frequency, and phase of the A-phase and B-phase AC voltages applied to the ultrasonic motor 10, or values ​​related to the corresponding control command values, can be used as actions.

[0048] For example, the reward may be a value related to the difference between a value related to the rotation speed of the ultrasonic motor 10, the torque output by the ultrasonic motor 10, the rotation position of the ultrasonic motor 10, etc. when the ultrasonic motor 10 is operated according to the control command value, and a target value of the operating state related to the target information. The input unit 42 inputs the reward based on the target information and the state information to the neural network 41. For example, the reward may be a value related to the smallness of the difference between the rotation speed of the ultrasonic motor 10 when the ultrasonic motor 10 is operated according to the control command value and the target rotation speed. In addition, processing such as subtracting the magnitude of the output fluctuation amount from the reward to stabilize the output or adding the entropy of the policy to encourage the search for learning data is performed.

[0049] For example, the trained model 32 created by the above-described deep reinforcement learning may be installed in the control device 20. Specifically, the network parameters of the neural network 41 obtained by the above-described deep reinforcement learning are introduced into the model installed in the control device 20, and the trained model 32 is installed in the control device 20.

[0050] This deep reinforcement learning is not limited to being performed using an actual ultrasonic motor 10. Deep reinforcement learning may also be performed using a simulation that uses, for example, an equivalent circuit model based on an LCR circuit. By performing machine learning using a simulation followed by machine learning using an actual ultrasonic motor 10, machine learning becomes faster and a highly reliable trained model can be quickly obtained.

[0051] The control device 20 may continue to re-learn the learned model while the ultrasonic motor 10 is operating. By continuing the learning, it is possible to deal with cases where the state of the hardware of the ultrasonic motor 10 changes, such as when the wear surface of the ultrasonic motor 10 changes, or when the environment in which the ultrasonic motor 10 is used changes.

[0052] [About ultrasonic motor systems] In the ultrasonic motor system 1 according to this embodiment, optimal control is performed by the control device 20 to bring the ultrasonic motor 10 into a target state as in the input target information when the ultrasonic motor 10 is operating. In particular, the control command value output by the control device 20 of this embodiment includes a value for changing the phase difference between the AC voltage for A phase and the AC voltage for B phase.

[0053] Conventionally, the operation of the ultrasonic motor 10 has been controlled solely by adjusting the drive frequency, because the operation of the ultrasonic motor 10 is a complex phenomenon involving many related parameters that can vary in a variety of ways depending on various conditions, making it difficult to control many parameters.

[0054] In contrast, the control device 20 of this embodiment is configured to be able to optimally control the operation of the ultrasonic motor 10 by incorporating a trained model 32 and using a large number of parameters including the phase difference. In this embodiment, by using a large number of parameters as state information indicating the current state of the ultrasonic motor 10, which is the input, and adjusting a large number of parameters of the AC voltage applied to the ultrasonic motor 10, which is the output, it is possible to optimally control the operation of the ultrasonic motor 10 and obtain high responsiveness and high stability regardless of the state of the ultrasonic motor 10.

[0055] It has become clear that control using phase difference is effective in controlling the torque of the ultrasonic motor 10. The ultrasonic motor 10, which excels in torque control using phase difference control, is expected to be applied to, for example, force feedback and haptic devices.

[0056] By using a large number of parameters as state information, it is possible to grasp the current state of the ultrasonic motor 10 more accurately and in detail, which may affect the control of the ultrasonic motor 10. By using a large number of parameters for the AC voltage applied to the piezoelectric element 132 to control the ultrasonic motor 10, the degree of freedom in operational control is improved. This makes it possible to achieve the above-mentioned optimal control. Similarly, the target state of the ultrasonic motor 10 is not limited to the rotation speed, but also includes torque, rotation position, etc., making it possible to perform various necessary controls.

[0057] High operational stability and high responsiveness are required in various usage situations of ultrasonic motors. For example, stability and response speed also affect the controllability of a positioning device. According to this embodiment, an ultrasonic motor system 1 that achieves high stability and high responsiveness can be realized.

[0058] The present invention has been described above by showing preferred embodiments, but it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

[0059] For example, the above-described technology is not limited to rotary traveling-wave ultrasonic motors, but can also be applied to linear traveling-wave ultrasonic motors. Furthermore, the above-described technology is similarly applicable not only to ultrasonic motors using vibrations of a circular plate as in the above-described embodiment, but also to rotary-mode ultrasonic motors using flexural vibrations of a cylinder. Furthermore, the above-described technology is similarly applicable not only to traveling-wave ultrasonic motors, but also to standing-wave ultrasonic motors. Standing-wave ultrasonic motors include linear ultrasonic motors and rotary ultrasonic motors. These include, for example, composite-mode ultrasonic motors, such as composite-vibrator ultrasonic motors that combine longitudinal and torsional piezoelectric elements. In composite-mode ultrasonic motors, controlling the phase difference to generate traveling waves in the above-described embodiment corresponds to controlling the phase difference between two vibration modes: longitudinal vibration and flexural vibration or torsional vibration. In other words, the ultrasonic motor may be any type of ultrasonic motor that utilizes ultrasonic vibration. [Explanation of symbols]

[0060] 1: Ultrasonic motor system 10: ultrasonic motor, 120: base, 130: stator, 131: elastic body, 132: piezoelectric element, 133: first surface, 140: rotor, 141: contact portion, 150: shaft, 160: bearing, 170: disc spring, 180: cover 20: control device, 21: processor, 22: memory, 23: storage, 24: input I / F, 25: output I / F, 26: bus line 31: Preprocessing section, 32: Trained model, 33: Postprocessing section 40: Agent, 41: Neural network, 42: Input section 60: Motor drive circuit 70: Sensor group, 71: Voltage sensor, 72: Current sensor, 73: Encoder, 74: Temperature sensor, 75: Calculator

Claims

1. an ultrasonic motor; a sensor for acquiring status information relating to the status of the ultrasonic motor; a motor drive circuit configured to apply an A-phase AC voltage and a B-phase AC voltage to the ultrasonic motor based on a control command value to operate the ultrasonic motor; a control device configured to acquire target information and state information relating to a target state of the ultrasonic motor, and to determine an optimal drive frequency and phase difference using a trained model configured to output information relating to an optimal drive frequency and phase difference for bringing the ultrasonic motor into the target state in response to input of the target information and state information, based on the acquired target information and state information, for a drive frequency that is the frequency of the AC voltage and a phase difference between the A-phase AC voltage and the B-phase AC voltage, and to output the control command value relating to the optimal drive frequency and phase difference to the motor drive circuit; An ultrasonic motor system comprising:

2. 2. The ultrasonic motor system according to claim 1, wherein the control device uses at least one of the amplitude and phase of the AC current flowing through the ultrasonic motor as the state information in order to bring the ultrasonic motor into the target state.

3. 3. The ultrasonic motor system according to claim 1, wherein the target state includes at least one of a torque output by the ultrasonic motor and a rotational position of the ultrasonic motor.

4. the trained model outputs, as an output for bringing the ultrasonic motor into the target state, information regarding at least one of an optimal amplitude and a phase of the AC voltage in addition to the optimal drive frequency and the phase difference; the control device is configured to output to the motor drive circuit the control command value related to at least one of an optimal amplitude and a phase of the AC voltage in addition to the optimal drive frequency and phase difference.

3. The ultrasonic motor system according to claim 1.

5. A control device that controls an A-phase AC voltage and a B-phase AC voltage to be applied to an ultrasonic motor to operate the ultrasonic motor, thereby controlling the operation of the ultrasonic motor, acquiring status information relating to a status of the ultrasonic motor and target information relating to a target status of the ultrasonic motor; determining an optimal drive frequency and phase difference between the A-phase AC voltage and the B-phase AC voltage based on the acquired target information and state information using a trained model configured to output information regarding the optimal drive frequency and phase difference for putting the ultrasonic motor into the target state in response to input of the target information and the state information; Outputting a control command value relating to the optimum drive frequency and phase difference The control device is configured as follows.

6. A control method for controlling an operation of an ultrasonic motor by controlling an A-phase AC voltage and a B-phase AC voltage applied to the ultrasonic motor to operate the ultrasonic motor, comprising: acquiring status information relating to a status of the ultrasonic motor and target information relating to a target status of the ultrasonic motor; determining an optimal drive frequency and phase difference between the A-phase AC voltage and the B-phase AC voltage based on the acquired target information and state information using a trained model configured to output information regarding the optimal drive frequency and phase difference for putting the ultrasonic motor into the target state in response to input of the target information and the state information; outputting a control command value relating to the optimum drive frequency and phase difference; A method for controlling an ultrasonic motor comprising:

7. A control program for causing a computer to control an A-phase AC voltage and a B-phase AC voltage to be applied to an ultrasonic motor to operate the ultrasonic motor, thereby controlling the operation of the ultrasonic motor, the program comprising: acquiring status information relating to a status of the ultrasonic motor and target information relating to a target status of the ultrasonic motor; determining an optimal drive frequency and phase difference between the A-phase AC voltage and the B-phase AC voltage based on the acquired target information and state information using a trained model configured to output information regarding the optimal drive frequency and phase difference for putting the ultrasonic motor into the target state in response to input of the target information and the state information; outputting a control command value relating to the optimum drive frequency and phase difference; A control program for executing the above.

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