JP2008079396A - Drive controller of vibration actuator, lens barrel and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the drive controller of a vibration actuator for shortening the drive time to a target position while enhancing stop position precision. <P>SOLUTION: The drive controller of a vibration actuator comprises a section 1a storing the relation of the drive speed of a vibration actuator 7 and the brake distance until the vibration actuator stops after driving is stopped, sections 1 and 9 for detecting the driving speed of the vibration actuator, and sections 1 and 3 performing drive control of the vibration actuator for based on a brake distance stored in the storage section and corresponding to a drive speed detected at the detecting section, and a residual driving amount for driving the vibration actuator for to a target position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a drive control device for a vibration actuator such as an ultrasonic motor, and a lens barrel and a camera including a vibration actuator that is driven and controlled by the drive control device.

  In general, an ultrasonic motor is used in an autofocus drive mechanism of a camera. This ultrasonic motor includes a stator having a piezoelectric element and a rotor driven by the stator, and is driven by supplying a drive signal to the piezoelectric element, and the rotor is stopped by stopping the supply ( Patent Document 1).

  In the drive control performed by the ultrasonic motor, the speed is rapidly increased, and when it reaches a predetermined speed, it is driven to the vicinity of the target position while maintaining this speed, and when it reaches the vicinity of the target position, the remaining drive amount to the target position In general, the speed is gradually decreased based on (a driving amount indicating how far the target position must be driven before reaching the target position).

However, in the conventional drive control, if the deceleration control from the vicinity of the target position is not properly performed, the target position may overrun and stop, or a situation may occur where the target position stops before the target position. There was a problem that it was not possible to stop at a target position with high accuracy in a short time.
JP 2003-304691 A

  The present invention has been made in view of the above circumstances, and provides a drive control device, a lens barrel, and a camera for a vibration actuator capable of reducing the drive time to the target position and improving the stop position accuracy. With the goal.

  The drive control device for a vibration actuator according to claim 1 of the present invention that achieves the above object is a relationship between a drive speed of the vibration actuator and a braking distance after the drive is stopped until the vibration actuator stops (for example, 6 (see FIG. 6), a speed detector (see, for example, encoder 9 in FIG. 1) for detecting the driving speed of the vibration actuator, and the speed detector. A drive control unit that drives and controls the vibration actuator based on the braking distance stored in the storage unit corresponding to the detected drive speed and the remaining drive amount for driving the vibration actuator to the target position ( For example, MCU 1 and phase circuit 3 in FIG. 1) are provided.

  An example of the vibration actuator is an ultrasonic motor. The driving speed includes a rotational speed.

  3. The vibration actuator drive control device according to claim 2, wherein the control unit compares the braking distance with the remaining drive amount, and drives the vibration actuator when the braking distance is smaller than the remaining drive amount. And when the said braking distance is more than the said remaining drive amount, the drive of the said vibration actuator is stopped (for example, refer the flowchart of FIG. 3).

  According to a third aspect of the present invention, the vibration actuator drive control device stores the relationship between the drive speed of the vibration actuator and the braking distance until the vibration actuator stops after the drive is stopped (see, for example, FIG. 6). A storage unit (see, for example, the storage unit 1a in FIG. 1), a setting unit (see, for example, MCU1 and VCO2 in FIG. 1) for setting a driving speed for driving the vibration actuator to a target position, and a target position of the vibration actuator. A control unit (see, for example, the MCU 1 and the phase circuit 3 in FIG. 1) that stops driving the vibration actuator when the distance becomes a braking distance stored in the storage unit corresponding to the set driving speed; It is provided with.

  According to a fourth aspect of the present invention, in the drive control device for a vibration actuator, when the control unit stops before the vibration actuator reaches the target position, the vibration actuator is driven again.

  According to a fifth aspect of the present invention, there is provided a lens barrel according to any one of the first to fourth aspects, a vibration actuator driven and controlled by the drive control apparatus, and a lens driven by the vibration actuator. And.

  A camera according to claim 6 is the drive control device according to any one of claims 1 to 4, a vibration actuator driven and controlled by the drive control device, a lens driven by the vibration actuator, It is provided with.

  According to the vibration actuator drive control device of the present invention, control is performed based on the braking distance and the remaining drive amount, so that it is possible to shorten the drive time to the target position and improve the stop position accuracy.

  Embodiments of a drive control device for a vibration actuator according to the present invention will be described below with reference to FIGS.

  FIG. 1 is a block diagram showing an embodiment of a drive control apparatus for a vibration actuator of the present invention, and FIG. 2 is a block diagram of a camera equipped with the drive control apparatus of FIG. In FIG. 2, a lens barrel 20 is detachably attached to the camera body 30. The lens barrel 20 includes a photographing lens 21, a drive control device 10, and an ultrasonic motor 7. The ultrasonic motor 7 is driven and controlled by the drive control device 10, and the ultrasonic motor is driven, whereby the photographing lens 21. Are driven in the direction of the optical axis, and focusing is performed.

  As shown in FIG. 1, the drive control device 10 includes an MCU 1, a voltage controlled oscillator (VCO) 2, a phase circuit 3, vibrating body excitation circuits 4 and 5, a high voltage power source 6, an encoder 9, and a storage unit 1a. The ultrasonic motor 7 is driven and controlled.

  The MCU 1 includes a DA (digital / analog) output unit, and controls the ultrasonic motor 7 and other actuators in the lens barrel 20 according to an instruction rotation speed, a rotation direction, and a target position which are input data (not shown). And so on. The MCU 1 determines the rotational speed to reach the target position in accordance with input data (not shown), and from the determined target rotational speed and the current rotational speed of the ultrasonic motor 7 that is an output from the speed detector 8. An operation amount is obtained, and DA output is performed on the VCO 2 based on the operation amount. The DA output value is, for example, in the range of 0V to 4V, and the rotational speed of the ultrasonic motor 7 can be changed by the DA output value. Increasing the DA output value increases the rotational speed of the ultrasonic motor, and decreasing the DA output value decreases the rotational speed of the ultrasonic motor. Further, the MCU 1 instructs the phase circuit 3 to indicate the rotation direction of the ultrasonic motor 7 and the permission signal for permitting the driving of the ultrasonic motor 7 (see FIGS. 4B and 5B). Motor drive signal).

  The storage unit 1a uses, as a database, the relationship between the number of rotations (rotational speed, driving speed) of the ultrasonic motor 7 as shown in FIG. 6 and the braking distance until the ultrasonic motor 7 stops after driving is stopped. Store the corresponding data in response to a request from the MCU 1.

  The VCO 2 generates a frequency four times the driving frequency of the ultrasonic motor 7 and changes the generated frequency according to the DA output value of the MCU 1. For example, the frequency generated when the DA output value from the MCU 1 is 0 V is a high frequency, and the frequency decreases as the DA output value increases. The frequency range corresponding to the range of the DA output value is set to be a frequency range sufficient for performing speed control of the ultrasonic motor 7 based on the frequency / rotational speed characteristics of the ultrasonic motor 7.

  The phase circuit 3 generates two drive signals Sa and Sb having a frequency equal to the drive frequency of the ultrasonic motor 7 based on the frequency generated by the VCO 2. The phase of the drive signal Sb differs from the drive signal Sa by 90 ° or 270 ° according to the direction signal from the MCU 1. Two drive signals Sa and Sb having different phases are input to the vibrator excitation circuits 4 and 5, respectively. The phase circuit 3 does not output the drive signals Sa and Sb unless receiving the permission signal from the MCU 1.

  The vibrating body excitation circuits 4 and 5 amplify the drive signals Sa and Sb from the phase circuit 3 to high voltage voltages that can drive the ultrasonic motor 7 and apply them to the input electrodes 7 a and 7 b of the ultrasonic motor 7.

  The high-voltage power supply 6 is a DCDC converter (not shown), boosts the power supply voltage to a high voltage that can drive the ultrasonic motor 7, and supplies power to the vibrator excitation circuits 4 and 5.

  The ultrasonic motor 7 includes a piezoelectric body that is an electromechanical transducer, and is a vibration actuator that uses the vibration of the piezoelectric body as a driving force, and has two input electrodes 7a and 7b for applying a high-frequency voltage to the piezoelectric body. . When two high-frequency voltages having different phases are applied from the vibrating body excitation circuits 4 and 5 to the input electrodes 7a and 7b, the piezoelectric body is excited to drive a rotor (not shown).

  The encoder 9 outputs a pulse signal for each predetermined rotation amount of the ultrasonic motor 7. The MCU 1 receives and counts the pulse signal from the encoder 9 and calculates the rotational speed of the ultrasonic motor 7 from the number of input pulse signals per predetermined time. That is, in the present embodiment, the rotational speed of the ultrasonic motor 7 is detected by counting with the encoder 9 and the MCU 1.

  The MCU 1 detects the rotational speed of the ultrasonic motor 7 in this way, and reads the braking distance corresponding to the detection result (rotational speed) from the storage unit 1a. The MCU 1 further counts the pulse signal input from the encoder 9 to obtain the movement amount up to the present, and obtains the remaining drive amount to the target position. Then, the braking distance is compared with the remaining drive amount, and a permission signal that instructs the phase circuit 3 to drive the ultrasonic motor 7 is output (the motor drive signal is turned on) or the permission signal is output. Is stopped (the motor drive signal is turned off).

  FIG. 3 is a flowchart showing an operation procedure in the MCU 1 when drive control (position control) is performed by the drive control apparatus 10 of the present embodiment.

  As described above, data regarding the target position is input to the MCU 1. First, in step S101, the MCU 1 obtains the current rotational speed of the ultrasonic motor 7 from the count value of the pulse signal input from the encoder 9 within a predetermined time.

  In step S102, the braking distance corresponding to the calculated rotation speed is read from the storage unit 1a. Further, the number of pulse signals output from the encoder 9 from the start of driving to the present time is counted to determine the remaining drive amount up to the target position. Then, the braking distance is compared with the remaining drive amount. If the braking distance is greater (YES), the process proceeds to step S103, and if the braking distance is smaller (NO), the process proceeds to step S104.

  In step S103, if the driving is continued as it is, the target position may be overrun. Therefore, the output of the permission signal to the phase circuit 3 is temporarily stopped so that the driving of the ultrasonic motor 7 is stopped (the motor driving signal is turned OFF). State). As a result, the supply of the drive signals Sa and Sb to the ultrasonic motor 7 is stopped, but the ultrasonic motor 7 does not stop immediately but continues to move with inertia. Further, in step S104, if the driving is stopped at the present time, it may stop before the target position and reach the target position. Therefore, the permission signal is continuously output to the phase circuit 3 so that the driving of the ultrasonic motor 7 is continued. As a result, the supply of the drive signals Sa and Sb to the ultrasonic motor 7 continues and the ultrasonic motor 7 continues to drive. And it transfers to step S105 from step S103, S104.

  In step S105, the pulse signal output from the encoder 9 is counted to determine whether or not the target position has been reached. If not reached (NO), the process returns to step S101 and the above-described operation is repeated. If it has reached (YES), the process proceeds to step S106, the supply of the drive signals Sa and Sb to the ultrasonic motor 7 is stopped, and the position control is ended.

  4 (a), 4 (b), 5 (a), and 5 (b) illustrate the contents of position control according to the flowchart of FIG. 3, and FIG. 4 (a) shows the change in the number of revolutions over time. FIG. 4B is a time chart showing a temporal change of a permission signal (motor drive signal) for permitting driving of the ultrasonic motor 7. In the figure, the horizontal axis represents the time axis, and the vertical axis represents the rotation speed of the ultrasonic motor 7 and the level of the permission signal (motor drive signal) (motor ON, motor OFF).

  In the cases shown in FIGS. 4A and 4B, the drive signals Sa and Sb are supplied to the ultrasonic motor 7 when the position control is started (the motor drive signal is turned on). Then, when the rotation speed reaches a certain rotation speed, the operation shifts to steady operation. Thereafter, the supply of the drive signals Sa and Sb to the ultrasonic motor 7 is stopped when the remaining drive amount to the target position becomes smaller than the braking distance corresponding to the rotation speed in the steady operation (the motor drive signal is changed). OFF state). As a result, the rotational speed decreases (decelerates). Then, when the braking distance corresponding to the decreased rotational speed becomes smaller than the remaining drive amount to the target position, the drive signals Sa and Sb are supplied to the ultrasonic motor 7 again (the motor drive signal is turned on). To do). This operation is repeated a plurality of times, finally reaching the target position and the ultrasonic motor 7 is stopped.

  The dotted line in FIG. 4A represents that the rotational speed (rotational speed) indicating the boundary of whether or not the ultrasonic motor 7 is overrun changes with time, and this boundary rotational speed (rotational speed). ), The supply of the drive signals Sa and Sb is stopped (the motor drive signal is turned off), and if it falls below the boundary rotational speed, the drive may stop before the target position. The supply of the signals Sa and Sb (the motor drive signal is turned on) is resumed.

  In the case shown in FIGS. 4A and 4B described above, the supply and stop of the drive signals Sa and Sb are repeated a plurality of times, so that the control becomes complicated.

  In the cases shown in FIGS. 5A and 5B, the supply and stop of the drive signals Sa and Sb are limited to one time, thereby avoiding complicated control.

  In this case, the number of revolutions in the vicinity of the target position is set in advance. In addition, a target rotational speed curve that decreases to the set rotational speed as it approaches the target position is set in advance, and the frequencies of the drive signals Sa and Sb are changed according to the target rotational speed curve. After the steady operation, the frequency of the drive signals Sa and Sb is sequentially increased from a predetermined time point to decrease the rotational speed. Then, the speed decreases to the set rotational speed, the supply of the drive signals Sa and Sb is stopped before the braking distance expected at this rotational speed (the motor drive state is turned off), and the ultrasonic motor 7 is actually After waiting for the stop, it is determined whether or not the target position has been reached. If the target position has not been reached, the drive signals Sa and Sb are supplied to the ultrasonic motor 7 again (the motor drive signal is turned on). As a result, it is possible to reach the target position in a short time and with high position accuracy without repeating the supply and stop of the supply of the drive signals Sa and Sb a plurality of times.

  Whether or not the ultrasonic motor 7 has actually stopped is checked based on whether or not there is a change in position between control cycles. If there is no change in position, the vehicle has actually stopped.

  In the camera 30 (see FIG. 2) equipped with the ultrasonic motor 7 and the drive control device 10 of the above-described embodiment in the lens barrel 20, the lens 21 can be driven and controlled with high accuracy in a short time during autofocus. It becomes possible.

  The drive control device for the vibration actuator of the present invention is not limited to the above-described embodiment. In short, the braking distance may be used for drive control.

  Moreover, although the case where the drive control apparatus of the vibration actuator of the present invention is applied to the lens barrel 20 and the camera 30 is shown, the present invention is not limited to this.

It is a block diagram showing one embodiment of a drive control device of a vibration actuator of the present invention. FIG. 2 is a schematic side view in which a lens barrel equipped with the drive control device shown in FIG. 1 and a camera equipped with the lens barrel are partially cut away. It is a flowchart which shows the control content of the drive control apparatus of FIG. The control content of the flowchart of FIG. 3 is illustrated by way of illustration, in which FIG. (A) is a graph showing a temporal change in the number of revolutions, and (b) in FIG. 3 is a temporal change of a permission signal permitting driving. It is a time chart. The control content of the flowchart of FIG. 3 is shown in another illustration, in which FIG. (A) is a graph showing a temporal change in the number of revolutions, and (b) in FIG. 3 is a temporal change in a permission signal for permitting driving. It is a time chart showing. It is a graph showing the relationship between the rotation speed (rotation speed, drive speed) of an ultrasonic motor, and the braking distance until the ultrasonic motor stops after driving stops.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 MCU 1a Memory | storage part 2 VCO 3 Phase circuit 4, 5 Vibrating body excitation circuit 6 High voltage power supply 7 Ultrasonic motor (vibration actuator)
9 Encoder 10 Drive control device 20 Lens barrel 21 Lens 30 Camera

Claims (6)

A storage unit that stores a relationship between a driving speed of the vibration actuator and a braking distance until the vibration actuator stops after driving is stopped;
A speed detector for detecting a driving speed of the vibration actuator;
Drive control of the vibration actuator based on the braking distance stored in the storage unit corresponding to the drive speed detected by the speed detection unit and the remaining drive amount for driving the vibration actuator to the target position A control unit,
A drive control device for a vibration actuator, comprising: In the drive control apparatus of the vibration actuator according to claim 1,
The control unit compares the braking distance with the remaining drive amount, and drives the vibration actuator when the braking distance is smaller than the remaining drive amount, and when the braking distance is equal to or greater than the remaining drive amount. A drive control device for a vibration actuator, wherein the drive of the vibration actuator is stopped. A storage unit that stores a relationship between a driving speed of the vibration actuator and a braking distance until the vibration actuator stops after driving is stopped;
A setting unit for setting a driving speed for driving the vibration actuator to a target position;
A control unit that stops driving the vibration actuator when the distance to the target position of the vibration actuator becomes a braking distance stored in the storage unit corresponding to the set driving speed;
A drive control device for a vibration actuator, comprising: In the drive control apparatus of the vibration actuator according to claim 3,
When the vibration actuator stops before the vibration actuator reaches the target position, the control unit drives the vibration actuator again. The vibration actuator drive control device according to any one of claims 1 to 4,
A vibration actuator driven and controlled by the drive control device;
A lens driven by the vibration actuator;
A lens barrel characterized by comprising: The vibration actuator drive control device according to any one of claims 1 to 4,
A vibration actuator driven and controlled by the drive control device;
A lens driven by the vibration actuator;
A camera characterized by comprising

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