JP2008083119A - Drive controller of vibration actuator, lens barrel and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stop the drive of a vibration actuator by detecting abnormality before a failure occurs. <P>SOLUTION: The drive controller of the vibration actuator is provided with: speed detecting means 1 and 9 for detecting the driving speed of the vibration actuator 7; and a control means 1 for controlling the drive of the drive actuator, based on the speed error between the target driving speed of the vibration actuator and the driving speed detected by the speed detecting means. The control means performs control for stopping the drive of the drive actuator, when it is judged that an integrated value obtained by integrating the speed error over time exceeds a predetermined value or when it is judged that the integrated value does not reach about the target driving speed within a predetermined time. <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 driven and controlled by the drive control device.

  An ultrasonic motor is used for an autofocus mechanism mounted on a lens barrel of a camera. This ultrasonic motor includes a stator having a piezoelectric body and a moving element. When a voltage having a frequency in the ultrasonic region is applied to the piezoelectric body, the stator vibrates, and the moving element is rotated by the vibration. Driven.

  Usually, the autofocus mechanism is equipped with a ring-shaped holder in the lens so as to be movable in the direction of the optical axis, the lens is fixed to the holder, and the holder ( Lens) is moved in the optical axis direction.

  In the lens barrel as described above, there has been proposed an apparatus that detects the operating state of the ultrasonic motor and determines whether the continuous operation of the ultrasonic motor is permitted or not based on the detected operating state (see Patent Document 1). .

  However, the above technique can cope with the deterioration of the ultrasonic motor, but may not be able to cope with the case where the lens cannot be moved smoothly due to a physical influence from the outside.

  For example, when the above-described holder that can move in the optical axis direction is provided at the tip of the lens barrel, physical influences from the outside during autofocusing (for example, the operator's hand or clothing) The holder (lens) may not move even when the ultrasonic motor is driven. If the operator continues the operation without noticing this, the ultrasonic motor continues to drive, and in the worst case, the ultrasonic motor may break down.

JP-A-9-308270

  The present invention provides a drive control device for a vibration actuator that can detect an abnormality and stop driving before failure occurs, and a lens barrel and a camera including a vibration actuator that is driven and controlled by the drive control device. The purpose is to do.

  In order to achieve the above object, a vibration actuator drive control device according to claim 1 of the present invention is detected by a speed detection means for detecting a drive speed of the vibration actuator, a target drive speed of the vibration actuator, and the speed detection means. Control means for controlling the drive of the drive actuator based on a speed error with respect to the determined drive speed, and the control means determines that an integrated value obtained by integrating the speed error with time has exceeded a predetermined value. Or when it is determined that the vicinity of the target drive speed is not reached within a predetermined time, control for stopping driving of the drive actuator is performed.

  According to a second aspect of the present invention, there is provided a drive control device for a vibration actuator, a speed detection means for detecting a drive speed of the vibration actuator, and a control means for controlling the drive of the drive actuator based on a target drive speed of the vibration actuator. And the control means determines that a predetermined time has elapsed since the speed detection means detects that the vibration actuator is in a stopped state, or reaches the target drive speed within a predetermined time. When it is determined not to perform the control, the driving actuator is controlled to stop driving.

  According to a third aspect of the present invention, there is provided a vibration actuator drive control device comprising: a speed detection unit that detects a drive speed of the vibration actuator; a target drive speed of the vibration actuator; and a drive speed detected by the speed detection unit. Control means for controlling the drive of the drive actuator based on the speed error between, when the control means determines that the integrated value obtained by integrating the speed error over time exceeds a predetermined value, or the target When it is determined that the vicinity of the driving speed is not reached within a predetermined time, or when it is determined that the predetermined time has elapsed since the speed detecting means detects that the vibration actuator is stopped, the driving of the driving actuator It is characterized by performing control to stop the operation.

  According to a fourth aspect of the present invention, there is provided the vibration actuator drive control device, wherein when the control means makes a drive request for the vibration actuator after a stop of the vibration actuator or when a predetermined time has elapsed, Actuator re-drive control is performed.

  A lens barrel according to a fifth aspect of the present invention is a vibration actuator drive control device according to any one of the first to fourth aspects, a vibration actuator driven by the drive control device, and the vibration actuator. And a lens driven by.

  A camera according to a sixth aspect of the present invention is a drive control device for the vibration actuator according to any one of the first to fourth aspects, a vibration actuator driven by the drive control device, and a drive by the vibration actuator. And a lens to be provided.

  According to the present invention, it is possible to detect an abnormality and stop driving the vibration actuator before failure occurs.

  A vibration actuator drive control device according to an embodiment of the present invention, and a lens barrel and a camera including a vibration actuator driven and controlled by the drive control device 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. FIG. 3 is a control block diagram showing the control content of the drive control device of FIG. 1, and FIG. 4 is a flowchart showing the operation content of the drive control device 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 apparatus 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 supply 6, and an encoder 9. The ultrasonic motor 7 is driven and controlled.

  The MCU 1 includes a DA (digital / analog) converter 1a (see FIG. 3). It is a control part which controls other actuators. The MCU 1 determines the rotational speed to reach the target position according to input data (not shown), and the current rotational speed of the ultrasonic motor determined based on the determined target rotational speed and the output from the encoder 9. The operation amount is obtained from the above, and DA output is performed from the DA converter 1a to the VCO 2 based on the operation amount. For example, by changing the DA output value in the range of 0V to 4V, the rotational speed of the ultrasonic motor 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 outputs a direction signal for instructing the rotation direction of the ultrasonic motor 7 to the phase circuit 3 and a permission signal for permitting the driving of the ultrasonic motor 7.

  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. Depending on the direction signal from the MCU1, the phase of the drive signal Sb differs from the drive signal Sa by 90 ° or 270 °. The two drive signals Sa and Sb 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 capable of driving the ultrasonic motor 7 and apply them to the input electrodes 7a and 7b of the ultrasonic motor 7, respectively. .

  The high-voltage power supply 6 boosts the power supply voltage to a high voltage capable of driving the ultrasonic motor 7 by a DCDC converter (not shown) and supplies the vibration body excitation circuits 4 and 5 with power.

  The ultrasonic motor 7 is a vibration actuator that includes a piezoelectric body that is an electromechanical conversion element and uses the vibration of the piezoelectric body as a driving force, and includes two input electrodes 7a for applying a high-frequency voltage to the piezoelectric body. 7b. 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 (moving element) (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 operation of the further MCU 1 will be described using the control block diagram of FIG. Since the input from the encoder 9 to the MCU 1 corresponds to the moving amount of the ultrasonic motor 7, the MCU 1 obtains the rotational speed by differentiating this. Then, a difference (speed error) between the target speed input to the MCU 1 and the rotational speed detected by the encoder 9 is obtained. Then, an operation amount (control output) is obtained based on the speed error, and the operation amount (control output) is converted into an analog signal (DA output) by the DA converter 1a and output to the VCO 2 to thereby output the ultrasonic motor 7. Feedback control of speed. This feedback control is performed by PI (proportional integral) control or PID (proportional integral derivative) control. Here, the PI control will be described.

The operation amount (control output) output from the MCU 1 is
Control output = target rotation speed + P x speed error + I x Σ (speed error)
It is represented by In the equation, P is a proportional gain, and I is an integral gain.

  FIG. 5 is a graph showing a control state of the ultrasonic motor 7 by the drive control device of the present embodiment. FIG. 5A shows the rotational speed of the ultrasonic motor 7 that changes with the passage of time, FIG. 5B shows the speed error that changes with the passage of time, and FIG. The control output which changes with progress is shown.

  As shown in FIG. 5A, the actual rotational speed of the ultrasonic motor 7 rises from zero (0) with respect to the set target rotational speed, gradually approaches the target rotational speed, and finally reaches the target rotational speed. It corresponds to the rotation speed. The speed error at this time is maximum when the rotational speed of the ultrasonic motor 7 is zero (0) as shown in FIG. 5B, and gradually approaches zero. The control output is the sum of the “target rotational speed” term, the “P × speed error” term, and the “I × Σ (speed error)” term, as shown in the above formula. As shown in FIG. 5 (c), when the rotational speed of the ultrasonic motor 7 is zero (0), the maximum value is obtained, and gradually becomes a substantially constant value.

  Of the control output, the term “target rotational speed” is constant (see the dotted line in FIG. 5C), but the term “P × speed error” is proportional to the speed error with time. It approaches zero (see the dashed line in FIG. 5C). On the other hand, the term “I × Σ (speed error)” is obtained by integrating the speed error and increases gradually with time (see the two-dot chain line in FIG. 5C). ).

The MCU 1 performs control to stop the driving of the ultrasonic motor 7 in the following cases (1), (2), and (3). That is, the output of the permission signal is stopped, and the supply of the drive signals Sa and Sb to the input electrodes 7a and 7b of the ultrasonic motor 7 is stopped.
(1) When it is determined that the integrated value obtained by integrating the speed error with time has exceeded a predetermined value (see the two-dot chain line (1) in FIG. 6C)
(2) When it is determined that a predetermined time has elapsed since the ultrasonic motor is determined to be stopped based on the signal from the encoder 9 (see (2) in FIG. 6A).
(3) When it is determined that the vicinity of the target rotational speed (for example, within the range of (target rotational speed × 0.7) to (target rotational speed × 1.2)) does not reach within the predetermined time (FIG. 6A (See (3) in))
FIG. 6 is a diagram showing changes in rotational speed, speed error, and control output when the above-described (1), (2), and (3) occur. FIG. 6A shows the time change of the rotational speed of the ultrasonic motor 7 as in FIG. 5A, and shows that when the ultrasonic motor 7 stops, the rotational speed rapidly decreases. . FIG. 6B shows the time variation of the speed error similarly to FIG. 5B, and shows that when the rotational speed of the ultrasonic motor 7 rapidly decreases and stops, the speed error increases rapidly. Yes. FIG. 6C shows the time change of the control output as in FIG. 5C, and when the rotational speed of the ultrasonic motor 7 rapidly decreases and stops, the integrated value of the speed error increases rapidly. Is shown.

  Hereinafter, the operation of the drive control apparatus 10 of the present embodiment will be described using the flowchart of FIG. First, when an ultrasonic motor drive command is input to the MCU 1 (step S100), the MCU 1 outputs a permission signal to drive the ultrasonic motor. Then, the MCU 1 controls the ultrasonic motor 7 so that the speed error between the target rotational speed and the actual rotational speed detected by the encoder 9 is made as small as possible so that the actual rotational speed approaches the target rotational speed. Then, PI control (or PID control) is performed (step S101).

  Next, in steps S102, S103, and S104, the driving state of the ultrasonic motor 7 is monitored. In step S102, it is determined whether or not an integrated value obtained by integrating the speed error with time has exceeded a predetermined value. In step S103, based on the signal from the encoder 9, it is determined whether or not a predetermined time has elapsed since it was determined that the ultrasonic motor is in a stopped state. In step S104, it is determined whether or not the vicinity of the target rotational speed is reached within a predetermined time. If both determinations are No, it can be determined that there is no abnormality in the driving state of the ultrasonic motor 7, so that the process proceeds to step S105 to determine whether or not to continue driving the ultrasonic motor 7, When continuing (in the case of Yes), it returns to step S102 and repeats the same operation | movement. When not continuing (in the case of No), the ultrasonic motor 7 is stopped (step S106). That is, the output of the permission signal is stopped.

  If it is determined No in at least one of step S102, step S103, and step S104, it can be determined that the drive state of the ultrasonic motor 7 is abnormal. Is controlled to pause (step S107). That is, the output of the permission signal is temporarily stopped. Next, in step S108, it is determined whether or not a predetermined time has elapsed since the ultrasonic motor 7 stopped, and the pause state is maintained until the predetermined time elapses (in the case of No). When the time has elapsed (in the case of Yes), the process proceeds to step S109, the permission signal is output again, and the ultrasonic motor 7 is restarted. Thereafter, the process proceeds to step S105 and the above-described operation is repeated.

  In step S108, it is determined whether or not a predetermined time has elapsed since the ultrasonic motor 7 stopped. Instead, it is determined whether or not there is a drive request for the ultrasonic motor 7, and there is a drive request. In this case, the process may proceed to step S109 to perform restart control of the ultrasonic motor 7.

  According to the drive control apparatus 10 of the present embodiment as described above, (1) when the integrated value obtained by integrating the speed error with time exceeds a predetermined value, (2) it is determined that the ultrasonic motor is in a stopped state. When a predetermined time has elapsed since then, (3) when the vicinity of the target rotational speed is not reached within the predetermined time, these are determined to be abnormal operation of the ultrasonic motor 7 and the ultrasonic motor 7 is stopped. Therefore, even if the operator is not aware of these operational abnormalities, the ultrasonic motor 7 is automatically paused and there is no possibility of failure.

  Further, since the ultrasonic motor 7 is re-driven after a predetermined time has elapsed after the temporary stop, there is no troublesome restarting operation and the operability is excellent.

  In FIG. 4, (1) when the integrated value obtained by integrating the speed error over time exceeds a predetermined value, (2) when a predetermined time has elapsed since it was determined that the ultrasonic motor is in a stopped state, (3) Although any one of the cases where the target rotational speed does not reach the target rotational speed within the predetermined time corresponds to the case where the ultrasonic motor 7 is temporarily stopped, the present invention is not limited to this. For example, the ultrasonic motor 7 may be temporarily stopped when any one of (1) and (2) described above is satisfied. Further, the ultrasonic motor 7 may be temporarily stopped when any one of (1) and (3) is applicable, or when any one of (2) and (3) is applicable. The sonic motor 7 may be temporarily stopped.

  Furthermore, the ultrasonic motor 7 may be temporarily stopped when both of (1) and (2) are applicable. Further, the ultrasonic motor 7 may be temporarily stopped when both of (1) and (3) are applicable, or the ultrasonic motor 7 is turned on when both of (2) and (3) are applicable. The ultrasonic motor 7 may be temporarily stopped when it corresponds to any of (1), (2), and (3). As described above, when the abnormal operation of the ultrasonic motor 7 is determined on the condition that any of a plurality of causes is applicable, the risk of erroneous determination can be reduced as much as possible.

It is a block diagram showing one embodiment of a drive control device of a vibration actuator of the present invention. It is a block diagram of the camera equipped with the drive control apparatus of FIG. It is a control block diagram which shows the control content of the drive control apparatus of FIG. It is a flowchart which shows the operation | movement content of the drive control apparatus of FIG. FIG. 5A is a graph showing a control state of the ultrasonic motor 7 by the drive control device of FIG. 1, FIG. 5A is a graph showing the rotational speed of the ultrasonic motor 7 that changes with time, and FIG. FIG. 5C is a graph showing the control output that changes with the passage of time. FIG. 5C is a graph showing the speed error that changes with the passage of time. FIG. 6 is a diagram showing changes in the rotational speed, speed error, and control output of the ultrasonic motor 7 when an abnormal state occurs in the drive control device of FIG. 1, and FIG. FIG. 6B is a graph showing the rotational speed of the sonic motor 7, FIG. 6B is a graph showing the speed error that changes with time, and FIG. 6C is a graph showing the control output that changes with time.

Explanation of symbols

1 MCU
2 VCO
3 Phase circuits 4 and 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)

Speed detecting means for detecting the driving speed of the vibration actuator;
Control means for controlling the drive of the drive actuator based on a speed error between the target drive speed of the vibration actuator and the drive speed detected by the speed detection means;
When the control means determines that the integrated value obtained by integrating the speed error over time exceeds a predetermined value, or determines that the speed error does not reach the target driving speed within a predetermined time, the driving means drives the drive actuator. And a vibration actuator drive control device. Speed detecting means for detecting the driving speed of the vibration actuator;
Control means for controlling the drive of the drive actuator based on the target drive speed of the vibration actuator,
The control means determines that a predetermined time has elapsed since the speed detection means has detected that the vibration actuator is in a stopped state, or has determined that the vicinity of the target drive speed has not been reached within a predetermined time. A drive control device for the vibration actuator, wherein the drive actuator is controlled to stop driving. Speed detecting means for detecting the driving speed of the vibration actuator;
Control means for controlling the drive of the drive actuator based on a speed error between the target drive speed of the vibration actuator and the drive speed detected by the speed detection means;
The control means determines that the integrated value obtained by integrating the speed error over time has exceeded a predetermined value, or determines that the vicinity of the target drive speed does not reach within a predetermined time, or the speed detection means A drive control device for a vibration actuator, wherein when it is determined that a predetermined time has elapsed since it was detected that the vibration actuator is in a stopped state, the drive control of the drive actuator is stopped. In the drive control apparatus of the vibration actuator as described in any one of Claim 1 to 3,
The drive means for the vibration actuator, wherein the control means performs re-drive control of the vibration actuator when a request for driving the vibration actuator is made after a stop of the vibration actuator or when a predetermined time has elapsed. . A drive control device for a vibration actuator according to any one of claims 1 to 4,
A vibration actuator driven by the drive control device;
A lens barrel comprising: a lens driven by the vibration actuator. A drive control device for a vibration actuator according to any one of claims 1 to 4,
A vibration actuator driven by the drive control device;
And a lens driven by the vibration actuator.

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