JP4578815B2 - Control system and electronic device using piezoelectric actuator - Google Patents

Description

  The present invention relates to a method of controlling a piezoelectric actuator that changes the speed or acceleration of deformation of a piezoelectric element, transmits only a force in one direction to the moving body, and drives the moving body, and an electronic apparatus using the same.

  In recent years, electronic devices have been miniaturized, and actuators used there have also been required to be miniaturized. As a typical example of this actuator, there is a system in which the operating member is driven through a reduction gear train by the rotational force of an electromagnetic motor, and the DC motor and stepping motor used there are being miniaturized.

On the other hand, actuators based on a new principle have been actively developed, and expectations are also high for those using piezoelectric elements with a large generated force. For example, the inertia of the working member generated when a frictional force is generated between the working member and the shaft that guides the working member so as to be movable in one direction, and the piezoelectric element provided at the tip of the shaft is periodically deformed. A method of operating the operating member by force has been developed (see, for example, Non-Patent Document 1). Further, such an actuator has been tried to be applied to a zoom mechanism and an autofocus mechanism of a camera.
Ryuichi Yoshida, Yasuhiro Okamoto, Journal of Precision Engineering, Vol. 68, NO. 5,2002

  However, the electromagnetic motor is not only difficult to miniaturize, but if the motor is miniaturized, the torque becomes extremely weak. Therefore, a reduction gear train is required, and it is difficult to reduce the size of the mechanism itself.

  In addition, the actuator that frictionally drives the moving body using the driving force generated by the deformation of the piezoelectric element can be easily reduced in size, but a position sensor is required when positioning control is performed in the same way as a DC motor. In order to perform accurate positioning control, a large and expensive sensor and drive circuit are required. This limited the degree of freedom in designing the mechanism and could be an obstacle to mounting on equipment.

  Also, in the case of a stepping motor, there is a limit to the step angle, and the step angle has become large especially when miniaturized.

A first aspect of the present invention to solve the above problems, the mobile by varying the acceleration or velocity of the first direction of displacement of the piezoelectric element, the second direction of displacement of the piezoelectric element and the acceleration or velocity A piezoelectric actuator that applies a driving force to the body; a drive circuit that outputs a drive pulse to the piezoelectric element; and a position sensor that obtains position information of an operating body that operates in conjunction with the operation of the moving body or the operation of the moving body; A control system comprising a control circuit for controlling a drive pulse output from the drive circuit based on position information of the position sensor, wherein drive data obtained in advance after receiving the position information of the position sensor The driving body or the operating body is positioned by outputting a driving signal having a predetermined number of pulses for driving the moving body within a range smaller than the resolution of the position sensor. The control system using a piezoelectric actuator for positioning a position.

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According to a second aspect of the present invention, there is provided an electronic apparatus including a control system using the piezoelectric actuator according to the first aspect.

  According to the present invention, a highly accurate and reliable control system can be realized even if the resolution of the position sensor is rough. In particular, since a small and inexpensive position sensor can be used, and the control circuit can be small and simple, the control system including the piezoelectric actuator can be downsized.

  In particular, the drive data used when outputting the drive signal for a predetermined number of pulses after receiving the position information of the position sensor is determined by performing the preceding operation when the piezoelectric actuator is in a standby state. It is possible to compensate for fluctuations in the movement distance with respect to the drive pulse due to fluctuations due to changes in the friction state over time, external environments such as temperature and humidity, or fluctuations in the load operated by the moving body. This advance operation is performed at the same time as checking the origin position of the moving body or operating body when the control system becomes ready for use by turning on the power, etc. No action is required. The drive data is appropriately updated based on the operation of the actuator, so that the reliability of the data is increased.

Further, the drive signal output by the predetermined number of pulses is different from the drive signal output to the piezoelectric element before that. In other words, when fine positioning is performed, the speed is reduced or the driving signal is set so that the moving amount of the moving body per pulse of the driving signal is reduced, so that the total moving time is short and highly accurate positioning is possible. It becomes possible.

  Since the piezoelectric actuator of this control system can drive the piezoelectric element in a non-resonant state, the current consumption is small, the drive circuit is simple and easy to downsize, and the electronic equipment equipped with this control system is small. And low power consumption can be realized.

  The control system of the present invention includes a piezoelectric actuator that applies a driving force to a moving body by differentiating acceleration or speed of displacement in the first direction of the piezoelectric element and acceleration or speed of displacement in the second direction of the piezoelectric element. A driving circuit that outputs a driving pulse to the piezoelectric element, a position sensor that obtains position information of the moving body that operates in conjunction with the operation of the moving body or the movement of the moving body, and a driving circuit that is based on the position information of the position sensor. A control system composed of a control circuit for controlling output drive pulses, and after receiving position information of a position sensor, outputs a drive signal for a predetermined number of pulses based on drive data obtained in advance. A control system using a piezoelectric actuator characterized by positioning a moving body or an operating body at a predetermined position.

  Here, the drive data is determined by performing a preceding operation when the piezoelectric actuator enters a standby state. In particular, the preceding operation is performed at the same time as confirming the origin position of the moving body or the operating body when the control system becomes ready for use by turning on the power or the like. The drive data is updated as appropriate based on the operation of the actuator.

Further, the driving signal output by a predetermined number of pulses is different from the driving signal output to the piezoelectric element before that, thereby enabling high-speed and high-precision positioning.
(Embodiment 1)
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a piezoelectric actuator 100 used in the control system of the present invention. One end of a bimorph 1 composed of a piezoelectric element is fixed to the fixing member 3. The disc-shaped moving body 2 has a central shaft 2a and is rotatably supported by a bearing (not shown). One end of the fixing member 3 is provided with a bearing portion 3a having a hole, and is supported so as to be rotatable about a shaft (not shown). The piezoelectric element 1 and the moving body 2 are in pressure contact with the other end 3b of the solid member 3 by a pressure member 4 made of a leaf spring. As shown in FIG. 1, a friction member 5 such as an engineering plastic such as engineering plastics or alumina having excellent wear resistance is joined to the contact portion of the moving body 3 of the piezoelectric element 1. good.

Next, the driving principle of the piezoelectric actuator 100 used in the control system of the present invention will be described with reference to FIGS. The bimorph 1 composed of piezoelectric elements is formed by, for example, superposing and joining piezoelectric elements 1a and 1b polarized in a tangential direction (direction of an arrow in FIG. 2) perpendicular to the radial direction of the rotating body 2. Electrodes (not shown) are provided on the bonding surface and the other surface of the piezoelectric elements 1a and 1b. Here, when the lead 22b connected to the electrode on the bonding surface of the piezoelectric elements 1a and 1b is set to GND and a voltage is applied to the lead 22a that short-circuits the electrode on the other surface of the piezoelectric elements 1a and 1b by the drive circuit, Since one piezoelectric element extends and one piezoelectric element contracts, the piezoelectric element 1 exhibits a bending displacement as a whole. When the polarity of the voltage is changed, the direction of deformation is also reversed. Here, the operation of rapidly deforming from the state of FIG. 1B to the state of FIG. 1C and the act of gently deforming from the state of FIG. 1C to the state of FIG. 1B are alternately performed. If it carries out, slip will arise between the moving body 2 and the piezoelectric element 1 in the former operation | movement, and since the moving body 2 will also rotate with the deformation | transformation of the piezoelectric element 1 in the latter operation | movement, the moving body 2 will move to one direction. . Actually, even if sliding and movement coexist in both operations, the moving body 2 can be moved in one direction as a result if the ratios are different.

In order to cause the piezoelectric element 1 to perform such a drive, the speed of deformation of the piezoelectric element 1 is changed by changing the speed at which the voltage is increased and the speed at which the voltage is decreased while using a drive pulse having an alternating voltage as a drive signal. , Acceleration varies depending on the first direction, which is the direction of deformation, and the second direction, which is the opposite direction to the first direction. For example, the rotation direction of the moving body 2 can be changed by applying the drive pulse shown in FIG. 2B or FIG. 2C between the leads 22a and 22b. Here, a drive pulse of only + polarity is applied, but a drive pulse that alternately repeats + and -polarities may be applied. In this case, the piezoelectric element 1 is displaced to the left and right with the state shown in FIG.

  In this way, the amount of movement of the moving body 2 caused by the deformation of the piezoelectric element 1 in the first direction and the amount of movement of the moving body 2 caused by the second direction (the direction opposite to the first direction) are made different. Such a driving pulse is not limited to that shown in FIG. Appropriate ones may be adopted according to required output specifications and circuit configurations. Moreover, you may use what comprised the unimorph using elastic members, such as a piezoelectric element and a metal, instead of a bimorph element. Since a large displacement can be obtained by using the bending deformation of the piezoelectric element 1 as in this embodiment, the piezoelectric element 1 can be driven at a low voltage.

  In the present embodiment, the piezoelectric element is polarized in a tangential direction orthogonal to the radial direction of the moving body. However, even if the polarization direction and the method of applying voltage are different, as a result, the radial direction of the moving body Any configuration may be used as long as the deformation is generated in the tangential direction orthogonal to the line. Next, the configuration of the control system of the present invention will be described with reference to FIG. This control system is interlocked with the piezoelectric actuator 100 composed of the piezoelectric element 1 that applies a driving force to the moving body 2, the drive circuit 7 that outputs a driving pulse to the piezoelectric element 1, and the operation of the moving body 2 or the operation of the moving body 2. The position sensor 14 that obtains the position information of the operating body 12 (not shown) that operates and the control circuit 8 that controls the drive pulse output from the drive circuit 7 based on the position information of the position sensor 14.

  A configuration in which the control system of the present invention is applied to an electronic device will be described with reference to FIG. This drive mechanism is provided on the rotational center axis of the moving body 9, the piezoelectric element 1 that is in pressure contact with the movable body 9 by a pressure mechanism (not shown), the fixing member 3 that supports the piezoelectric element 1, and the movable body 9. An output shaft 10 that rotates integrally with the body 9, and a bearing 16 that guides the rotation of the output shaft 10 and the moving body 9 with the moving body 9 and shaft portions 10 a and 10 b provided integrally with the output shaft 10. , 11, and an operating body 12 having a female screw portion 12 a that engages with the external thread portion 10 c provided on the side surface of the output shaft 10, and a hole-shaped guide portion 12 b provided on the operating body 12. A guide shaft 15, a slit plate 14 a provided on the output shaft 10, a light emitting portion, a position sensor 14 comprising a light receiving portion, a light receiving portion, a projecting portion 13 a attached to the operating body 12, a light receiving portion, Consists of a detection element 13b composed of a light emitting unit Consisting point position detecting element 13.

  When the movable body 9 rotates with the operation of the piezoelectric element 1, the output shaft 10 also rotates together, and the operating body 12 operates in the direction of the rotation center axis of the output shaft 10. By changing the rotation direction of the moving body 9, the operating direction of the operating body 12 changes. The position of the operating body 12 can be confirmed by the position sensor 14 and the origin position detecting element 13. First, the position information of the control circuit 8 is adjusted to the origin (counter value 0) by moving the operating body 12 to a position where the projecting portion 13a can detect, that is, the origin position. Thereafter, the position of the working body 12 can be known from the relationship between the number of pulses of the position sensor (the amount of rotation of the moving body 9) and the amount of movement of the working body 12.

For example, if the lens 24 is joined to the hole 12c provided in the operating body 12, a zoom mechanism, an autofocus mechanism, or the like of the camera can be realized. By adopting such a structure, a reduction mechanism is provided in which the moving amount of the operating body 12 is small with respect to the moving angle of the moving body 9, so that highly accurate positioning is possible and the resolution of the position sensor 14 is relatively high. Coarse is enough. And the driving force of the operating body 12 also increases. In addition, it is possible to realize a highly reliable electronic device in which the operating body 12 is difficult to move against external impacts and vibrations.

  Next, a method for controlling the piezoelectric actuator 100 of the present invention will be described. Since the piezoelectric actuator 100 can basically rotate the moving body 9 by the same amount for each drive pulse, the positioning control may be performed without using the position sensor 14, but the piezoelectric element 1 and the moving body The amount of movement per pulse may fluctuate due to changes in the frictional state with respect to 9 and the influence of the environment such as temperature and humidity, fluctuations in the driving voltage depending on the battery usage state, and the like. Accordingly, the approximate position is confirmed using the position sensor 14 and the movement amount per drive pulse stored in the control circuit 8 in advance for an area smaller than the resolution of the position sensor 14 ( The required number of pulses is calculated based on the drive data), and a command is sent to the drive circuit 7 to output only the required number of pulses. For example, if the moving position of the moving body 9 is between 8 and 9 pulses as position information obtained from the position sensor 14, it is necessary to move the remaining distance from the time when 8 pulses are detected. It outputs to the piezoelectric element 1 by the number of driving pulses. By doing in this way, even if the resolution of the position sensor 14 is rough, highly accurate and reliable positioning is possible.

  The drive data may be stored at the manufacturing stage, but is preferably determined by performing a preceding operation when the piezoelectric actuator 100 is in a standby state. This is done when confirming the position, so that the electronic device is not made useless. For example, in the case of a digital camera, this standby state occurs when the power is turned on or the photographing mode is set. By doing so, it is not affected by changes in the frictional state that differ at the stage of use, environmental influences such as temperature and humidity, and fluctuations in drive voltage due to battery usage. Further, as the drive data, for example, a pulse necessary for easily moving a certain distance may be measured. However, a drive pulse necessary for movement at each interval (pulse) of the position information of the position sensor 14 may be 9 is measured over the entire circumference of the moving body 12 or the entire moving distance of the operating body 12, it is possible to compensate for the difference in the required driving pulse due to the moving position caused by frictional irregularities. Further, if data based on the moving direction is also measured, for example, in the case of a camera, the influence of the posture difference can be compensated.

  By the way, the drive data may be measured and updated during the operation of the actuator, as well as in the standby state. For example, the number of pulses to be output may be determined based on data during operation.

  The driving pulse output by the predetermined number of pulses is different from the driving signal output to the piezoelectric element before that, that is, until the last position information is obtained from the position sensor 14, thereby enabling high-speed and high-precision positioning. Is possible. As shown in FIG. 5, the behavior of the moving body 9 varies depending on the drive pulse. That is, as shown in FIG. 5 (a), when the operation and stop are repeated for each drive pulse, and when continuously operating without stopping as shown in FIG. 5 (b). Divided. In general, when the frequency of the drive pulse increases, the behavior as shown in FIG. In this case, although the speed of the moving body 9 is increased, not only the moving body 7 is not instantaneously stopped when the driving pulse is stopped, but also the moving distance for each driving pulse is difficult to specify. That is, since the value obtained by dividing a certain distance by the number of driving pulses necessary for continuous operation does not coincide with the moving distance when only one pulse is added, the reliability of the driving data is lowered. Incidentally, an ultrasonic motor using a resonance phenomenon of a vibrating body is also close to this state. Therefore, within the range in which the position information is obtained from the position sensor 14, the movement of FIG. 5B is performed at high speed, and when applying a predetermined pulse, the operation of FIG. Performs fine movement. The timing for performing the fine movement operation may be within the range where the position information is obtained from the position sensor 14, and may be determined as appropriate according to the characteristics of the entire control system, the required specifications, and the like.

By the way, as long as the piezoelectric actuator 100 is based on the operation principle of the present invention, the form thereof may be a linear type, or the one shown in Non-Patent Document 1. In addition, the same effect can be obtained with a non-resonant ultrasonic motor that can be operated at a constant interval by repeatedly operating and stopping for each drive pulse.

  Further, the position sensor 14 may be a linear sensor or may be attached to an operating body. Moreover, you may be an electronic device which works with the mobile body 9 itself.

  If the operating body of the piezoelectric actuator of the present invention is provided with, for example, a lens, it can be applied to electronic devices such as a zoom mechanism and an autofocus mechanism of a camera.

It is a figure which shows the structure of the piezoelectric actuator concerning Embodiment 1 of this invention. It is a figure which shows the structure and drive signal of a piezoelectric actuator which concern on Embodiment 1 of this invention. It is a figure which shows the structure of the control system concerning Embodiment 1 of this invention. It is the figure which applied the control system concerning Embodiment 1 of the present invention to electronic equipment. It is a figure which shows the behavior of the piezoelectric actuator concerning Embodiment 1 of this invention.

DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Moving body 3 Fixed member 4 Pressurizing member 5 Friction member 7 Drive circuit 8 Control circuit 9 Moving body 12 Working body 14 Position sensor

Claims (4)

A piezoelectric actuator that applies a driving force to the moving body by differentiating the acceleration or speed of displacement of the piezoelectric element in the first direction and the acceleration or speed of displacement of the piezoelectric element in the second direction;
A drive circuit for outputting a drive pulse to the piezoelectric element;
A position sensor for obtaining position information of an operating body that operates in conjunction with the operation of the moving body or the operation of the moving body;
A control system comprising a control circuit for controlling a drive pulse output from the drive circuit based on position information of the position sensor;
After receiving the position information of the position sensor, by outputting a driving signal having a predetermined number of pulses for driving the moving body in a range smaller than the resolution of the position sensor based on driving data obtained in advance. A control system using a piezoelectric actuator, wherein a movable body or the operating body is positioned at a predetermined position, and the drive data is updated by performing a preceding operation when the piezoelectric actuator enters a standby state . 2. The control system using a piezoelectric actuator according to claim 1, wherein the preceding operation is performed when an origin position of the moving body or the operating body is confirmed . 3. The control system using a piezoelectric actuator according to claim 1, wherein the drive signal output by the predetermined number of pulses is different from the drive signal output to the piezoelectric element before that . An electronic apparatus using a control system using the piezoelectric actuator according to claim 1.

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