DRIVING APPARATUS OF VIBRATION-TYPE ACTUATOR, METHOD OF CONTROLLING DRIVING VIBRATION-TYPE ACTUATOR, AND IMAGE PICKUP APPARATUS
A driving apparatus of a vibration-type actuator includes a driving circuit configured to drive a vibration unit including a plurality of vibrators, a detection unit configured to detect a sum of power consumption consumed by the plurality of vibrators, and a driving frequency setting unit configured to set a driving frequency within a frequency range depending on the sum of power consumption detected by the detection unit.
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1. Field of the Invention
An aspect of the present disclosure relates to a driving apparatus of a vibration-type actuator, a method of controlling driving a vibration-type actuator, and an image pickup apparatus, and more specifically, to a driving apparatus of a vibration-type actuator configured to, for example, generate a vibration wave in an ultrasonic vibrator thereby relatively moving a driven element in contact with the ultrasonic vibrator by frictional force, a method of controlling driving such a vibration-type actuator, and an image pickup apparatus including such a driving apparatus.
2. Description of the Related Art
A camera, a video camera, and other devices are commercially available which use a vibration-type actuator configured to apply an AC signal to an electric-mechanical energy conversion element (hereinafter referred to as an electromechanical transducer) thereby causing a vibrating element to generate a driving force.
A detailed description of the structure and the drive principle of the vibration-type actuator of the above-described type may be found, for example, in Japanese Patent Laid-Open No. 2004-320846, and thus a further description thereof is omitted. Note that the vibrator includes a vibration generation part including an elastic element and a piezoelectric element bonded together, the vibration-type actuator includes a driving force generation part that generates a driving force to move the pressed-into-contact driven element relatively with respect to the vibrator, and a vibration-type motor apparatus includes at least one driving force generation part. By applying the driving force to the driven element, the driven element is caused to have a rotary or linear motion.
In the above-described vibration-type motor apparatus using a plurality of vibrators, to drive the vibration-type motor apparatus with the optimum frequency using the related technique, the phase difference between the driving voltage and the voltage of the vibration detecting unit is detected for each of vibrators. Subsequently, a plurality of signal processing circuits are necessary, which results in an increase in a total circuit complexity. To achieve the operation using only one phase detection unit (detector) and one signal processing circuit, it may be necessary, for example, to select a vibrator that exhibits an abrupt reduction in speed at the highest driving frequency of all vibrators. Hereinafter, such a driving frequency blow which an abrupt reduction in speed occurs refers to as a critical driving frequency. Even when it is possible to identify which one of vibrators has the highest critical driving frequency, to avoid the abrupt reduction in speed, it is necessary to have a large margin in operation conditions taking into account a difference among the vibrators in terms of characteristic of a phase difference between the driving voltage and the detected voltage.
In view of the above, embodiments of the invention relate to a driving apparatus of a vibration-type actuator capable of operating within a particular frequency range thereby suppressing an abrupt reduction in speed due to an overload or a difference in characteristic among vibrators, a method of controlling driving a vibration-type actuator, and an image pickup apparatus including such a driving apparatus.
According to an embodiment, a driving apparatus of a vibration-type actuator includes a driving circuit configured to drive a vibration unit including a plurality of vibrators, a detector configured to detect a sum of power consumption consumed by the plurality of vibrators, and a driving frequency setting unit configured to set a driving frequency within a frequency range depending on the sum of power consumption detected by the detector. According to an embodiment, a method of controlling driving a vibration-type actuator includes detecting a sum of power consumption consumed by a plurality of vibrators, and controlling a driving frequency within a frequency range based on the detected sum of power consumption.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
The present invention is described below with reference to embodiments.
First EmbodimentIn a first embodiment, a vibration-type actuator includes a plurality of vibrators disposed on a circumference of a circle thereby to drive a ring-shaped driven element to be rotated. An example of a driving apparatus configured to drive such a vibration-type actuator and an example of a method of controlling driving such a vibration-type actuator are described below with reference to figures. In the present embodiment, the driving apparatus of the vibration-type actuator includes a vibration unit including a plurality of vibrators each configured to vibrate in response to applying a voltage to an electromechanical transducer fixed to an elastic element. The driving apparatus also includes a driven element that is pressed against the vibrators of the vibration unit such that the driven element is driven via friction and is moved relatively with respect to the vibration unit. More specifically, as illustrated in
The impedance elements are circuit elements adapted to provide proper impedance matching with the piezoelectric elements of the vibrator such that voltages are increased to values that allows more electric power to be supplied to the piezoelectric elements. Reference numeral 16 denotes a DC power supply such as a stabilized power supply, a battery, or the like. To drive a plurality of vibrators, instead of providing as many switching circuits as there are vibrators, the embodiment illustrated in
Reference numeral 15 denotes a position detection unit (detector) configured to detect a rotational position of a rotation unit including, for example, a photointerupter and a slit plate. The position and speed information of the rotation unit obtained as a result of the detection performed by the position detection unit 15 are transferred to the microcomputer unit 10, and microcomputer unit control the motor according to the position and speed information of the rotation unit. Reference numeral 17 denotes an electric power detection unit serving as a unit to detect the sum of power consumption consumed by the plurality of vibrators and the driving circuit. More specifically, when the vibration-type motor apparatus is driven by the switching circuit 12, the total electric power applied to the three vibrators is detected, and a detected value thereof is sent to the microcomputer unit 10. Note that the detected electric power is given by the product of a voltage and a current, and thus, if the power supply voltage is constant, the value of the electric power may be detected by monitoring only the current value. In the present example, the single driving circuit is used to drive the plurality of vibrators, and thus the electric power detection unit 17 detects the sum of power consumption consumed by the driving circuit. Note that the electric power detection unit may be configured in other manners as long as the electric power detection unit is capable of detecting the sum of power consumption consumed by the plurality of vibrators. For example, in a case where driving circuits are provided separately for the respective vibrators, the electric power detection unit may be configured to detect the sum of power consumption of these driving circuits.
In a case where it is determined that detected electric power Pi≧P_Lim, if the frequency of the driving voltage is further reduced from the current value, the result is an increase in electric power. Therefore, the microcomputer unit (driving frequency setting unit) 10 sets the driving frequency to be fixed at the current value or to a higher value (that is, a value equal to the current value plus α) (F-18). In a case where the driving frequency is fixed at a value obtained at a moment when the detected electric power Pi exceeds P_Lim, then there is a possibility that the electric power overshoots, which may cause the detected electric power Pi to be further increased above P_Lim. To handle such a situation, the frequency may be set to be higher by α than the above-described critical frequency so that Pi≧P_Lim does not occur even when an overshoot occurs. Alternatively, the driving frequency setting unit 10 repeatedly sets the driving frequency to be lower than the previously detected driving frequency until the detected electric power Pi becomes equal to P_Lim. By performing the process from F-16 to F-18, it becomes possible to prevent the sum of electric power from exceeding a particular (predetermined) value. Furthermore, because the value of P_Lim is set to be lower than a critical value of electric power corresponding to a frequency below which an abrupt reduction in speed occurs as described above, the process from F-16 to F-18 makes it possible to suppress the abrupt reduction in the driving speed thereby ensuring that the driving is performed within a predetermined range of frequency. On the other hand, in a case where the detected electric power is smaller than P_Lim, the control frequency f_dr1 is set to f_dr, and the driving is performed. The position is then detected, and a determination is performed as to whether a target position has been reached (F-19, F-20). In a case where the target position is not reached, the processing flow returns to F-14 to repeat the controlling of the motor. When the target position is reached, the motor is stopped (F-21).
In the present embodiment, as described above, the sum of electric power of the three vibrators is detected as a function of the frequency, and the frequency is controlled such that the electric power does not exceed the predetermined limit P_Lim thereby preventing the electric power from becoming too large. Furthermore, it becomes possible to control the driving frequency not to go within a frequency range in which an abrupt reduction in speed occurs. The limit of the electric power P_Lim may be set in advance to a value that allows any of the three vibrator not to have too large input electric power taking into account difference in resonance frequency among the three vibrators. Although three vibrators are provided in the present embodiment, the embodiment may be applied to any plural number of vibrators.
Second EmbodimentNext, with reference to
In the algorithm illustrated in
In a third embodiment described below, the sign of the rate of change of the sum of detected power consumption with respect to the frequency is detected, and the driving frequency is controlled such that the driving frequency is not lower than the frequency at which the above-described sign changed from a negative value to a positive value, and at the starting, the frequency is set to a starting value at which the rate of change of the sum of detected power consumption with the respect to the frequency tends to increase, and the frequency is swept to a value at which the driving speed and the power consumption increase.
As described above, the vibration motor including the plurality of vibrator may be driven such that the sum of electric power is detected, and the driving frequency is determined based on the value of electric power, the rate of change, and the sign of the rate of change. This ensures that the vibration motor is driven in a frequency range within which the desired performance is obtained regardless of whether the vibrators have different characteristics. A vibration-type motor including a plurality of vibrators capable of driving a driven element has an advantage that it is small in size and may be easily installed. Because of its advantages, the vibration-type motor is used in a wide variety of apparatuses such as a camera, a video camera, and so on. In such a vibration-type motor, use of the detected sum of electric power in controlling driving of a plurality of vibrators makes it possible to realize a driving circuit having a simple configuration and being capable of stably driving the vibration-type motor.
Fourth EmbodimentIn a fourth embodiment, as described below with reference to
In the example illustrated in
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2012-257877 filed Nov. 26, 2012, which is hereby incorporated by reference herein in its entirety.
Claims
1. A driving apparatus of a vibration-type actuator, comprising:
- a driving circuit configured to drive a vibration unit including a plurality of vibrators;
- a detector configured to detect a sum of power consumption consumed by the plurality of vibrators; and
- a driving frequency setting unit configured to set a driving frequency within a frequency range based on the sum of power consumption detected by the detector.
2. The driving apparatus of the vibration-type actuator according to claim 1, wherein the driving frequency setting unit sets the driving frequency such that in a case where the sum of power consumption detected by the detector is greater than a value, the driving frequency is fixed or the driving frequency is set to a value greater than a frequency at which the sum of power consumption increases across the value.
3. The driving apparatus of the vibration-type actuator according to claim 1, wherein the driving frequency setting unit sets the driving frequency such that in a case where a rate of change of the sum of power consumption detected by the detector with respect to the driving frequency is greater than a value, the driving frequency is fixed or set to a value greater than a frequency at which the rate of change increases across the value.
4. The driving apparatus of the vibration-type actuator according to claim 3, wherein the driving frequency setting unit sets the driving frequency such that in a case where a sign of the rate of change of the sum of power consumption detected by the detector with respect to the driving frequency changes from positive to negative, the driving frequency is fixed or the driving frequency is set to a value greater than a frequency at which the sign of the rate of change changes from positive to negative.
5. The driving apparatus of the vibration-type actuator according to claim 3, wherein the driving frequency setting unit sets a start frequency to a value at which the rate of change of the sum of power consumption detected by the detector with respect to the driving frequency increases, and the driving frequency setting unit sweeps the driving frequency to a value at which a driving speed and the power consumption increase.
6. The driving apparatus of the vibration-type actuator according to claim 1, wherein the driving frequency setting unit sets a frequency of a driving signal within the frequency range to suppress an abrupt reduction in the driving speed or an increase in electric power beyond a value.
7. The driving apparatus of the vibration-type actuator according to claim 1, wherein the detector that detects the sum of power consumption consumed by the plurality of vibrators is an unit configured to detect power consumption of the driving circuit.
8. The driving apparatus of the vibration-type actuator according to claim 1, wherein the driving frequency setting unit sets the driving frequency to be less than a previous value of the driving frequency in response to detecting the sum of power consumption by the detector until the sum of power consumption detected by the detector exceeds a value.
9. The driving apparatus of the vibration-type actuator according to claim 1, wherein the driving frequency setting unit sets the driving frequency to be less than a previous value of the driving frequency in response to detecting a rate of change of the sum of power consumption by the detector with respect to the driving frequency until the rate of change of the sum of power consumption detected by the detector exceeds a value.
10. The driving apparatus of the vibration-type actuator according to claim 1, wherein the vibration-type actuator comprising:
- a vibration unit including a plurality of vibrators each including an electromechanical transducer and each configured to vibrate in response to an application of a voltage, and
- a driven element pressed against the plurality of vibrators such that the driven element is driven via friction and the driven element moves relatively with respect to the vibration unit.
11. An image pickup apparatus comprising:
- a vibration-type actuator; and
- the driving apparatus of the vibration-type actuator according to claim 1.
12. A method of controlling driving of a vibration-type actuator, comprising:
- detecting a sum of power consumption consumed by a plurality of vibrators; and
- controlling a driving frequency within a frequency range based on the detected sum of power consumption.
13. The method of controlling driving of the vibration-type actuator according to claim 12, wherein the controlling of the driving frequency includes, in a case where the detected sum of power consumption is greater than a value, fixing the driving frequency or controlling the driving frequency to be greater than a frequency of a driving voltage at which the sum of power consumption increases across the value.
14. The method of controlling driving of the vibration-type actuator according to claim 12, wherein the controlling of the driving frequency includes, in a case where a rate of change of the detected sum of power consumption with respect to the driving frequency is greater than a value, fixing the driving frequency or controlling the driving frequency to be greater than a frequency of a driving voltage at which the rate of change of the sum of power consumption increases across the value.
15. The method of controlling driving of the vibration-type actuator according to claim 12, wherein the controlling of the driving frequency includes, in a case where a sign of the rate of change of the detected sum of power consumption with respect to the driving frequency changes from positive to negative, fixing the driving frequency or controlling the driving frequency to be greater than a frequency of a driving voltage at which the sign of the rate of change changes from positive to negative.
16. The method of controlling driving of the vibration-type actuator according to claim 12, wherein the controlling of the driving frequency comprising:
- setting a start frequency to a value at which a rate of change of the detected sum of power consumption with respect to the driving frequency increases, and
- sweeping the driving frequency to a value at which a driving speed and the power consumption increase.
17. The method of controlling driving of the vibration-type actuator according to claim 12, wherein the controlling of the driving frequency includes setting a frequency of a driving signal within the frequency range to suppress an abrupt reduction in a driving speed or an increase in electric power beyond a value.
18. The method of controlling driving of the vibration-type actuator according to claim 12, wherein the detecting of the sum of power consumption consumed by the plurality of vibrators includes detecting power consumption of a driving circuit.
19. The method of controlling driving of the vibration-type actuator according to claim 12, wherein the controlling of the driving frequency includes controlling the driving frequency to be less than a previous value of the driving frequency until the detected sum of power consumption exceeds a value.
20. The method of controlling driving of the vibration-type actuator according to claim 12, wherein the controlling of the driving frequency includes controlling the driving frequency to be less than a previous value of the driving frequency until a rate of change of the detected sum of power consumption with respect to the driving frequency exceeds a value.
21. The method of controlling driving of the vibration-type actuator according to claim 12, wherein the vibration-type actuator comprising:
- a vibration unit including a plurality of vibrators each including an electromechanical transducer and each configured to vibrate in response to an application of a voltage to the electromechanical transducer, and
- a driven element pressed against the plurality of vibrator so as to be driven via friction.
Type: Application
Filed: Nov 21, 2013
Publication Date: May 29, 2014
Applicant: CANON KABUSHIKI KAISHA (Tokyo)
Inventor: Akio Atsuta (Yokosuka-shi)
Application Number: 14/086,868