Control device for a vibration motor and driving device

Abstract

The present application provides a control device of a vibration motor and a driving device. The control device of the vibration motor includes a driving signal generation unit configured to generate a driving signal of the vibration motor, and a boost circuit configured to boost the driving signal. The driving signal generation unit changes a duty cycle of the driving signal based on a driving frequency of the vibration motor or a current flowing through the vibration motor.

Description

Technical Field

[0001] This invention relates to control and drive devices for vibration motors. Background Technology

[0002] It is conventionally known that when using an amplifier equipped with a resonant circuit to drive a vibration-type motor such as an ultrasonic motor, the voltage and / or current waveforms are distorted according to the drive frequency, resulting in decreased drive performance and power efficiency. Japanese Patent Application Laid-Open No. 2000-70851 discloses a method for converting the drive waveform of an ultrasonic motor into a sine wave using a drive circuit equipped with an analog filter and a linear amplifier to improve harmonic distortion caused by a boost circuit. JP 2000-184759 discloses a method for improving the distortion of the drive voltage waveform of an ultrasonic motor by adjusting the pulse width using a switching circuit to improve harmonic distortion caused by a boost circuit.

[0003] The method disclosed in JP 2000-70851 is effective in improving the distortion of the drive waveform, but the use of analog filters and linear amplifiers is disadvantageous in terms of power consumption (power efficiency). The method disclosed in JP2000-184759 can improve the distortion of the voltage waveform, but cannot improve the distortion of the current waveform. Summary of the Invention

[0004] This invention provides a control device and a drive device for a vibration motor, each of which can improve drive performance and reduce power efficiency.

[0005] According to one aspect of the present invention, a control device for a vibration-type motor includes: a drive signal generation unit configured to generate a drive signal for the vibration-type motor; and a boost circuit configured to boost the drive signal. The drive signal generation unit changes the duty cycle of the drive signal based on the drive frequency of the vibration-type motor. A drive device having the above-described control device also constitutes another aspect of the present invention.

[0006] A control device for a vibration motor, the control device comprising: a drive signal generation unit configured to generate a drive signal for the vibration motor; and a boost circuit configured to boost the drive signal. The drive signal generation unit changes the duty cycle of the drive signal based on the current flowing through the vibration motor.

[0007] A driving device includes: a vibration motor; a driven member driven by the vibration motor; a drive signal generation unit configured to generate a drive signal for the vibration motor; and a boost circuit configured to boost the drive signal, wherein the boosted drive signal is applied to the vibration motor. The drive signal generation unit changes the duty cycle of the drive signal based on the drive frequency of the vibration motor.

[0008] A driving device includes: a vibration motor; a driven member driven by the vibration motor; a drive signal generation unit configured to generate a drive signal for the vibration motor; and a boost circuit configured to boost the drive signal, wherein the boosted drive signal is applied to the vibration motor. The drive signal generation unit changes the duty cycle of the drive signal based on the current flowing through the vibration motor.

[0009] Further features of the invention will become apparent from the following description of typical embodiments with reference to the accompanying drawings. Attached Figure Description

[0010] Figure 1 This is a block diagram of a control device for a vibration motor according to various embodiments.

[0011] Figure 2 This is a detailed diagram of the control device for the vibration type motor according to the first embodiment.

[0012] Figure 3 This is an exemplary input / output relationship of the H-bridge circuit according to the first embodiment.

[0013] Figure 4 This is a flowchart illustrating a method for determining the duty cycle according to a first embodiment.

[0014] Figure 5 This is an exemplary result obtained by step response measurement in the first embodiment.

[0015] Figure 6 The relationship between the drive frequency and duty cycle in the first embodiment is shown.

[0016] Figures 7A to 7C An example of reducing current distortion by changing the duty cycle is shown in the first embodiment.

[0017] Figure 8 This is a detailed diagram of the control device for the vibration motor according to the second embodiment.

[0018] Figure 9 This is a flowchart illustrating a method for determining the duty cycle according to a second embodiment.

[0019] Figures 10A to 10C Examples of a reference current waveform and an actual measured current waveform according to the second embodiment are shown. Specific Implementation

[0020] A detailed description of embodiments of the present invention will now be given with reference to the accompanying drawings.

[0021] First Embodiment

[0022] Now for reference Figures 1 to 7C This section will describe a control device for a vibration-type motor (ultrasonic motor) according to a first embodiment of the present invention. This embodiment will discuss a method for measuring the characteristics of a boost circuit using a step response and for determining an appropriate duty cycle based on the characteristics of the boost circuit.

[0023] Figure 1 This is a block diagram of a control device 100 for a vibration type motor. A drive signal generation unit 101 generates a frequency signal (drive signal) for driving piezoelectric elements 222a and 222b in the vibration type motor 103. Boost circuits 102a and 102b boost the voltage applied to the piezoelectric elements 222a and 222b (the frequency signal generated by the drive signal generation unit 101) to the voltage required for actuator operation. The vibration type motor 103 has piezoelectric elements 222a and 222b and functions as an actuator by applying a frequency signal to these piezoelectric elements to cause them to vibrate. The structure and vibration mode of the vibration type motor 103 can, for example, use the same known technology as that of vibration type motors described in JP 2016-218349 and JP 2017-060279, and their description will be omitted.

[0024] This embodiment will discuss a boost method that combines the following two boost methods: a boost method using a transformer, and a boost method using the resonance between the capacitive components of an inductive element and a piezoelectric element.

[0025] Figure 2 This is a detailed diagram of the control device 100 for the vibration motor. The drive signal generation unit 101 includes a control signal generation unit 200, a circuit characteristic storage unit (memory) 201, and H-bridge circuits 210a and 210b. The control signal generation unit 200 generates the frequency signal required to drive the vibration motor 103 based on control commands. The circuit characteristic storage unit 201 stores circuit characteristics such as the resonant period of the boost circuits 102a and 102b.

[0026] Figure 3The illustration shows an example of the input / output (I / O) relationship of the H-bridge circuit 210a. When input A, a square wave signal with a duty cycle of 25%, is input to the first input terminal of the H-bridge circuit 210a, and input / A, a square wave signal with a duty cycle of 25%, is input to the second input terminal, a drive signal as an output is generated. The signals input to the first input terminal and the signals input to the second input terminal are signals whose phases are offset by 180 degrees from each other. The time period during which the input signal becomes a High period is called the Ton time 301, and the time period during which the input signal becomes a Low period is called the Toff time 302.

[0027] The boost circuit 102a includes an inductor 220a, a transformer 221a, and a piezoelectric element 222a for the vibratory motor 103. The boost circuit 102a uses the transformer 221a to boost the signal output from the drive signal generation unit 101, and utilizes the resonance between the inductor 220a and the piezoelectric element 222a to apply the frequency signal required to drive the vibratory motor 103. The control command unit 230 issues a drive speed command to control the vibratory motor 103. The boost circuit 102b has an inductor 220b, a transformer 221b, and a piezoelectric element 222b, and operates in the same manner as the boost circuit 102a.

[0028] Figure 4 This is a flowchart illustrating a method for determining the duty cycle according to this embodiment. First, in step S11, a step response is measured to measure the characteristics (resonance characteristics) of the boost circuits 102a and 102b. Figure 5 This is an illustrative result of the step response measurement. When the step input waveform 501 is input to the boost circuits 102a and 102b, the step response waveform 502 is obtained.

[0029] The periodic signal applied to the piezoelectric elements 222a and 222b as a vibration motor is typically a repetition of the first wave of the step response waveform 502. The time period from the start of the measurement until the peak voltage of the first wave is set to High 503. This time period corresponds to approximately half of the resonant period 504 of the step response waveform. Since the step response measurement method is known, its description will be omitted. The step response measurement method can be performed using external devices such as an oscilloscope, or information processing equipment such as a microcomputer equipped with measurement circuitry (not shown) and a control signal generation unit. Although... Figure 5 The voltage waveform is shown, but the current waveform can be measured.

[0030] Next, in Figure 4In step S12, the measured High 503 is stored in the circuit characteristic storage unit 201. In the actual driving of the vibration motor 103, in step S13, the drive signal generation unit 101 determines the drive frequency f and phase difference Θ according to the control command from the control command unit 230. Next, in step S14, the drive signal generation unit 101 determines the duty cycle for the drive frequency f as follows:

[0031] Duty cycle [%] = Thigh [sec] × drive frequency f [Hz] × 100.

[0032] Next, in step S15, the control signal generation unit 200 outputs a frequency signal (drive signal) having a determined drive frequency f, phase difference Θ, and duty cycle. In this embodiment, the drive signal generation unit 101 obtains the duty cycle by calculation, but the invention is not limited to this embodiment, and the Ton time 301 can be fixed at High 503. Steps S11 and S12 are performed, for example, during factory adjustments or power-on, and may not be performed every time.

[0033] Figure 6 This illustrates the relationship between the drive frequency and duty cycle in this embodiment, as well as an exemplary duty cycle selected by the control signal generation unit 200 when the resonant period 504 is, for example, 7.6 μsec.

[0034] Figure 7A and 7B This illustration shows an example of reducing current distortion by changing the duty cycle according to this embodiment, and how to do so in response to a speed command from the control command unit 230. Figure 6 The diagram shows the secondary current waveforms of transformers 221a and 221b observed when the drive frequency and duty cycle are changed. Figure 7A An example is shown when the drive frequency is 92MHz, and Figure 7B An example is shown when the drive frequency is 88MHz. Figure 7C The example is a comparison with a duty cycle of 34.96% (which is the value when the drive frequency is 92MHz) and a drive frequency of 88MHz, and the distortion of the current waveform is greater than that in this embodiment.

[0035] This embodiment describes an example of storing the resonant periods of boost circuits 102a and 102b in the circuit characteristic storage unit 201 and calculating the duty cycle using the control signal generation unit 200, but the duty cycle can be adjusted based on the driving frequency.

[0036] This embodiment measures the resonant characteristics of boost circuits 102a and 102b using step response measurements, but another measurement method or previously calculated theoretical values ​​can be used. Since the resonant characteristics can change depending on temperature, the duty cycle can be adjusted after temperature correction using a temperature corrector. Higher frequencies can be used to generate the input waveform in a pseudo-manner, and this embodiment is widely applicable to frequencies used to drive vibration-type motors.

[0037] Therefore, the control device uses a boost circuit to generate the drive waveform of the vibratory motor and appropriately adjusts the duty cycle of the drive signal of the vibratory motor. That is, the drive signal generation unit changes the duty cycle of the drive signal based on the drive frequency of the vibratory motor. When the drive frequency is a first drive frequency, the drive signal generation unit can set the duty cycle to a first duty cycle; when the drive frequency is a second drive frequency higher than the first drive frequency, it can set the duty cycle to a second duty cycle higher than the first duty cycle. The drive signal generation unit can set the duty cycle to reduce or minimize current distortion in the current waveform of the vibratory motor. The drive signal generation unit can set the duty cycle to make the current waveform of the vibratory motor closer to a sine wave. The drive signal generation unit can determine the duty cycle based on a time period corresponding to half the resonant period of the boost circuit. The control device for the vibratory motor may also include a memory (circuit characteristic storage unit 201) for storing the time period corresponding to half the resonant period, and the drive signal generation unit determines the duty cycle based on the time period corresponding to half the resonant period (High 503) and the drive frequency. In this embodiment, the drive signal corresponds to the frequency signal used to drive the piezoelectric elements in the vibration motor. This improves current distortion in the piezoelectric elements 222a and 222b, and also improves power efficiency.

[0038] Second Embodiment

[0039] Now for reference Figures 8 to 10C The following will describe a control device for a vibration motor according to a second embodiment of the present invention. This embodiment improves current distortion by using a current detection circuit to detect the current flowing through the vibration motor, reducing the duty cycle when the current obtained by the current detection circuit is greater than a sine wave, and increasing the duty cycle when the current obtained by the current detection circuit is less than a sine wave.

[0040] Figure 8This is a detailed diagram of the control device 100a for the vibration motor according to this embodiment. The drive signal generation unit 101a includes a control signal generation unit 200, a reference current waveform storage unit 702, a comparison unit 703, and H-bridge circuits 210a and 210b. The control signal generation unit 200 generates the frequency signal (drive signal) required to drive the vibration motor 103 based on control commands. The boost circuit 102a includes an inductor 220a, a transformer 221a, and a piezoelectric element 222a for the vibration motor 103.

[0041] The boost circuit 102a boosts the signal output from the drive signal generation unit 101a via the transformer 221a, and applies the frequency signal of the voltage required to drive the vibration motor 103 using the resonance between the inductor 220a and the piezoelectric element 222a. The boost circuit 102b includes the inductor 220b, the transformer 221b, and the piezoelectric element 222b, and has the same function as the boost circuit 102a. Current detection units 701a and 701b detect the current flowing through the vibration motor 103. The comparison unit 703 compares the current detected by the current detection units 701a and 701b (measured current) with the reference current stored in the reference current waveform storage unit 702. The control command unit 230 issues a drive speed command to control the vibration motor 103.

[0042] Figure 9 This is a flowchart illustrating the method for determining the duty cycle according to this embodiment. First, in step S21, a simulation is performed to calculate the theoretical current waveforms of the boost circuits 102a and 102b. Since the method for solving the circuit is known, its description will be omitted. Next, in step S22, the simulation result from step S21 is stored as a reference current (reference current waveform) in the reference current waveform storage unit 702. Next, in step S23, the drive signal generation unit 101a sets the initial value of the duty cycle. Next, in step S24, when driving the vibration motor 103, the drive signal generation unit 101a determines the drive frequency f and phase difference Θ based on the control command from the control command unit 230. Next, in step S25, the drive signal generation unit 101a outputs a frequency signal (drive signal) for driving the vibration motor 103.

[0043] Next, in step S26, the drive signal generation unit 101a adjusts the duty cycle based on the result of driving the vibration motor 103 using the frequency signal output in step S25. In this embodiment, the comparison unit 703 observes, for example, a current waveform of one cycle (the current waveform detected by the current detection units 701a and 701b (the actual measured current waveform)) and determines whether the current waveform is greater than a reference current waveform. If the current waveform of one cycle is greater than the reference current waveform, the process proceeds to step S27. In step S27, the drive signal generation unit 101a decreases the duty cycle. For example, when the duty cycle decreases by 0.1%, the duty cycle of the next cycle becomes 49.9%. On the other hand, if the current waveform of one cycle in step S26 is less than the reference current waveform, the process proceeds to step S28. In step S28, the drive signal generation unit 101a increases the duty cycle. For example, when the duty cycle increases by 0.1%, the duty cycle of the next cycle becomes 50.1%. The criteria for judgment can be, for example, by comparing the magnitude obtained by integrating over a period, or by comparing each sample.

[0044] Figures 10A to 10C Examples of reference current waveforms and actual measured current waveforms are shown. Figures 10A to 10C Examples are shown of the reference current waveform stored in the reference current waveform storage unit 702 and the current waveform measured by the current detection units 701a and 701b, which are compared with each other by the comparison unit 703. The dashed line indicates the reference current waveform, and the solid line indicates the measured current waveform. Figure 10A and Figure 10B An example is shown where the measured current waveform is larger than the reference current waveform. Figure 10C An example is shown where the measured current waveform is smaller than the reference current waveform. Figure 10A An example is shown where the measured current waveform is consistently larger than the reference current waveform, and Figure 10B This illustrates an example where the measured current waveform is smaller than the reference current waveform for a portion of the time period.

[0045] In this embodiment, two current detection units 701a and 701b are used. The measurement results at the two measurement points of the vibration motor 103 are the same, but the measurement results at these two measurement points may be different. In this case, the average value of the two measurement results can be used, or one of the measurement results can be preferred. This embodiment uses two current detection units, but the measurement result at one measurement point can be used by using only one current detection unit.

[0046] Therefore, the control device uses a boost circuit to generate the drive waveform of the vibratory motor and a current detection unit to appropriately adjust the duty cycle of the drive signal of the vibratory motor. That is, the drive signal generation unit changes the duty cycle of the drive signal based on the current flowing through the vibratory motor. The control device for the vibratory motor may include: a current detection unit for detecting the current flowing through the vibratory motor; and a comparison unit for comparing the current detected by the current detection unit with a reference current. The drive signal generation unit can determine the duty cycle based on the comparison result between the current detected by the comparison unit and the reference current. The drive signal generation unit can decrease the duty cycle when the current is greater than the reference current and increase the duty cycle when the current is less than the reference current. This improves the current distortion of the piezoelectric elements 222a and 222b and enhances power efficiency.

[0047] The control device for the vibratory motor according to various embodiments appropriately adjusts the duty cycle based on the drive frequency and current value of the drive signal of the vibratory motor, thereby improving the current distortion of the piezoelectric element. Therefore, the various embodiments can provide a control device for the vibratory motor that can improve the reduction of drive performance and power efficiency.

[0048] The control device for the vibration type motor according to the various embodiments is applicable to various drive devices. Exemplary drive devices including the control device for the vibration type motor, the vibration type motor, and the driven member to be driven by the vibration type motor are optical devices such as lens devices having a lens as a driven member or camera devices including an image direction changing member as a driven member, and industrial devices such as table devices including a worktable with a movable object mounted as a driven member or a robot arm including an arm or finger as a driven member.

[0049] Other embodiments

[0050] The embodiments of the present invention can also be implemented by providing software (programs) that perform the functions of the above embodiments to a system or device via a network or various storage media, and the computer or central processing unit (CPU) or microprocessor unit (MPU) of the system or device reads out and executes the program.

[0051] Although the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims is to be interpreted in the broadest sense to include all such modifications, equivalent structures, and functions.

Claims

1. A control device of a vibration-type motor, the control device comprising: a drive signal generation unit configured to generate a drive signal of the vibration-type motor; and a step-up circuit configured to step up the drive signal, characterized in that the drive signal generation unit sets a duty ratio to a first duty ratio in a case where a drive frequency of the vibration-type motor is a first drive frequency, and sets the duty ratio to a second duty ratio higher than the first duty ratio in a case where the drive frequency is a second drive frequency higher than the first drive frequency, and a current distortion of a current waveform of the vibration-type motor is smaller when the duty ratio is set to the second duty ratio than when the duty ratio is set to the first duty ratio at the second drive frequency.

2. The control apparatus of a vibration-type motor according to claim 1, characterized by The drive signal generation unit sets the duty ratio so that a current waveform of the vibration-type motor is closer to a sine wave.

3. The control apparatus of a vibration-type motor according to claim 1, wherein The drive signal generation unit determines the duty ratio based on a period corresponding to half of a resonance period of the step-up circuit.

4. The control device of the vibration-type motor according to claim 3, further comprising a memory configured to store the period corresponding to half of the resonance period, characterized in that The drive signal generation unit determines the duty ratio based on the period and the drive frequency.

5. The control apparatus of a vibration-type motor according to claim 1, wherein The drive signal corresponds to a frequency signal supplied to a piezoelectric element in the vibration-type motor.

6. The control apparatus of a vibration-type motor according to any one of claims 1 to 5, characterized by The control device applies the drive signal stepped up by the step-up circuit to the vibration-type motor.

7. A control device of a vibration-type motor, the control device comprising: a drive signal generation unit configured to generate a drive signal of the vibration-type motor; a current detection unit configured to detect a current flowing through the vibration-type motor; a comparison unit configured to compare the current detected by the current detection unit with a reference current; and a step-up circuit configured to step up the drive signal, characterized in that the drive signal generation unit decreases a predetermined duty ratio of the drive signal to a first duty ratio in a case where the current is greater than the reference current, the drive signal generation unit increases the predetermined duty ratio to a second duty ratio in a case where the current is smaller than the reference current, a current distortion of a current waveform of the vibration-type motor is smaller when the duty ratio is set to the first duty ratio than when the duty ratio is set to the predetermined duty ratio in a case where the current is greater than the reference current, and a current distortion of the current waveform is smaller when the duty ratio is set to the second duty ratio than when the duty ratio is the predetermined duty ratio in a case where the current is smaller than the reference current.

8. The control apparatus of a vibration-type motor according to claim 7, wherein The control device applies the drive signal stepped up by the step-up circuit to the vibration-type.

9. A drive device comprising: a vibration-type motor; a driven member driven by the vibration-type motor; A drive signal generation unit is configured to generate a drive signal for the vibration motor. as well as A boost circuit is configured to boost the drive signal, and the boosted drive signal is applied to the vibration motor. Its features are, The drive signal generation unit sets the duty cycle to a first duty cycle when the drive frequency of the vibration motor is a first drive frequency, and sets the duty cycle to a second duty cycle higher than the first duty cycle when the drive frequency is a second drive frequency higher than the first drive frequency. At the second driving frequency, when the duty cycle is set to the second duty cycle, the current distortion of the current waveform of the vibrating motor is less than the current distortion of the current waveform of the vibrating motor when the duty cycle is set to the first duty cycle.

10. The drive apparatus according to claim 9, characterized by The driving device is a lens device, and the driven component is a lens.

11. The drive apparatus according to claim 9, characterized by The driving device is a camera device, and the driven component is a camera direction changing component.

12. A driving device, comprising: Vibration motor; The driven component is driven by the vibration-type motor; A drive signal generation unit is configured to generate a drive signal for the vibration motor. A current detection unit is configured to detect the current flowing through the vibrating motor; A comparison unit is configured to compare the current detected by the current detection unit with a reference current; as well as A boost circuit is configured to boost the drive signal, and the boosted drive signal is applied to the vibration motor. Its features are, If the current is greater than the reference current, the drive signal generation unit reduces the predetermined duty cycle of the drive signal to a first duty cycle. If the current is less than the reference current, the drive signal generation unit increases the predetermined duty cycle to a second duty cycle. When the current is greater than the reference current, and the duty cycle is set to the first duty cycle, the current distortion of the current waveform of the vibrating motor is less than the current distortion of the current waveform of the vibrating motor when the duty cycle is set to the predetermined duty cycle. When the current is less than the reference current, the current distortion of the current waveform is less when the duty cycle is set to the second duty cycle than when the duty cycle is set to the predetermined duty cycle.

13. The drive apparatus according to claim 12, characterized by The driving device is a lens device, and the driven component is a lens.

14. The drive apparatus according to claim 12, characterized by The driving device is a camera device, and the driven component is a camera direction changing component.

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