JP2006187099A - Controller for vibration type actuator and apparatus equipped with same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for vibration type actuators capable of causing the driving speed of a vibration type actuator to reach a target speed without stopping the driving of the vibration type actuator. <P>SOLUTION: The controller includes: a detecting means (3, 5) that detects the driving speed of a vibration type actuator; and a controlling means (6) that controls the driving of a vibration type actuator. When a driving speed detected by the detecting means has not reached the target speed, the controlling means varies the frequency of a frequency signal so that the detected driving speed reaches the target speed in a range of frequency higher than a predetermined frequency. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a control device for a vibration actuator that relatively drives a vibrating body that excites vibration and a contact body that contacts the vibrating body.

  In a conventional vibration type motor control device, driving of the vibration type motor is started by applying a frequency signal having a predetermined frequency higher than the resonance frequency of the vibrating body to the electro-mechanical energy conversion element. Then, the driving speed of the vibration type motor is increased by gradually decreasing the frequency from a predetermined frequency (see, for example, Patent Document 1).

Here, the speed at which the frequency is changed is uniquely set in advance so that the target drive speed can be obtained at a desired time. That is, the frequency is changed based on a preset pattern.
JP 06-327273 A (paragraph number 0012, FIG. 2 etc.)

  In the above-described vibration type motor control device, when an external load is applied to the vibration type motor, and the frequency is changed in a preset pattern, the following problems will occur. May occur.

  That is, before the drive speed of the vibration type motor reaches the target speed, the frequency of the frequency signal input to the vibration type motor reaches the lower limit value of the frequency range used for drive control of the vibration type motor. In this case, so-called control step-out occurs, and the drive of the vibration type motor stops.

  The present invention is a control device for a vibration type actuator that relatively drives a vibrating body whose vibration is excited by application of a frequency signal to an electro-mechanical energy conversion element and a contact body that contacts the vibrating body. , Detecting means for detecting the driving speed of the vibration type actuator, and control means for controlling the driving of the vibration type actuator. When the drive speed detected by the detection means has not reached the target speed, the control means has the detected drive speed reach the target speed in a region on a higher frequency side than a predetermined frequency. Thus, the frequency of the frequency signal is changed.

  According to the present invention, the driving speed of the vibration actuator can be reached to the target speed without stopping the driving of the vibration actuator.

  Examples of the present invention will be described below.

  FIG. 1 is a diagram illustrating a schematic configuration of a vibration type motor control apparatus that is Embodiment 1 of the present invention.

  The vibration motor 1 has a rotating shaft 2, and a rotary encoder 3 is attached to one end side of the rotating shaft 2. As shown in FIG. 2, the vibration type motor 1 includes a vibrating body having a piezoelectric element 11 and an elastic member 12 as electro-mechanical energy conversion elements, and a contact body 13 that contacts the elastic member. The contact body 13 is in pressure contact with the elastic member 12 by receiving an urging force of an urging member 14 (for example, a disc spring or a coil spring).

  In the configuration of the vibration type motor 1 described above, when a frequency signal (periodically changing signal, alternating signal, etc.) having different phases is applied to the piezoelectric element 11, a progressive vibration wave (progressive wave) travels to the elastic member 12. Wave) is generated, and the contact body 13 is rotated by friction between the elastic member 12 and the contact body 13. The rotating shaft 2 also rotates together with the contact body 13, and this rotational force is transmitted to the driven member 7 via a power transmission mechanism (not shown).

  Here, the vibrating body can be constituted by only the piezoelectric element, or the vibrating body can be rotated with respect to the contact body. The vibration type motor 1 can be of any type such as a rod type or an annular type.

  Further, as the driven member 7, for example, a driving unit of an electric pan head device for turning a mounted TV camera or the like, an electric stage for performing a linear operation in a semiconductor manufacturing apparatus, a photographing lens in a photographing optical system, and There is a drive unit that moves in the direction and a photosensitive drum in the image forming apparatus.

  The drive control circuit (control means) 6 outputs a command signal related to the frequency of the frequency signal applied to the piezoelectric element 11 to the drive voltage generation circuit 4. The drive voltage generation circuit 4 receives a command signal from the drive control circuit 6 and applies a frequency signal having a frequency corresponding to the command signal to the piezoelectric element 11.

  The rotary encoder 3 outputs a pulse signal according to the rotation of the vibration type motor 1 (rotating shaft 2). The pulse counting circuit 5 counts the pulse signal output from the rotary encoder 3 and outputs the count value to the drive control circuit 6. Thereby, the drive control circuit 6 can detect the rotational speed of the vibration type motor 1.

  FIG. 8 shows the relationship between the rotational speed of the vibration type motor 1 and the frequency of the frequency signal. The drive control circuit 6 performs control to increase or decrease the frequency of the frequency signal so that a predetermined rotation speed is obtained.

  FIG. 3 is a diagram showing the relationship between the rotational speed of the vibration type motor 1 and time. FIG. 4 is a diagram showing the relationship between the frequency of the frequency signal applied to the piezoelectric element 11 and time.

  Here, the vibration type motor 1 may be subjected to a load more than expected from the outside. That is, the rotation (rotation speed) of the vibration type motor 1 may be suppressed by an external load.

  In this case, even if a frequency signal having a frequency corresponding to the target speed is applied to the piezoelectric element 11, the rotational speed of the vibration motor 1 does not reach the target speed. That is, even if a frequency (FIG. 4) corresponding to the target speed indicated by the dotted line in FIG. 3 is applied, the actual rotational speed may be as indicated by the solid line in FIG.

  When the frequency is changed (decreased) in the predetermined pattern shown in FIG. 4 in a state where the actual rotational speed does not follow the target speed as described above, the frequency reaches the lower limit value of the control frequency at timing ts. .

  Here, the lower limit value of the control frequency is the lower limit value of the frequency range used when drive control of the vibration type motor 1 is performed. Specifically, as the above lower limit value, as shown in FIG. 8, a value near the resonance frequency of the vibrating body (frequency at which the rotation speed becomes a peak value) and higher than the resonance frequency is set. Can do.

  As shown in FIG. 8, when the frequency of the frequency signal applied to the piezoelectric element 11 is made lower than the frequency f1 at the start of driving the vibration type motor 1, the rotational speed increases, but the resonance frequency of the vibrating body is increased. In the region on the lower frequency side, the rotational speed is extremely reduced. A vibration type motor generally has the characteristics shown in FIG.

  For this reason, when drive control of the vibration type motor 1 is performed, a lower limit value of the frequency is set. When the lower limit value is not reached, it is determined that the control is out of step and the drive of the vibration type motor 1 is stopped. It is supposed to let you.

  Therefore, as shown in FIG. 4, when the frequency of the frequency signal applied to the piezoelectric element 11 reaches the lower limit at timing ts, the driving of the vibration type motor 1 is stopped and rotated as shown in FIG. The speed becomes zero. That is, the driving of the vibration type motor 1 is stopped before the rotational speed of the vibration type motor 1 reaches the final target speed v1.

  In the present embodiment, it is possible to suppress the drive of the vibration type motor 1 from stopping before the rotational speed of the vibration type motor 1 reaches the target speed v1, and to stably start the vibration type motor 1. is there.

  Hereinafter, the control operation in the present embodiment will be specifically described with reference to the flowchart shown in FIG. This control operation is performed by the drive control circuit 6.

  In step S <b> 1 of FIG. 7, the drive of the vibration type motor 1 is started by applying a frequency signal having a frequency f <b> 1 to the piezoelectric element 11 of the vibration type motor 1 via the drive voltage generation circuit 4. In step S2, the frequency is changed with the first pattern shown in FIG. That is, the frequency is gradually reduced from the frequency f1 toward the lower limit side.

  In step S <b> 3, the rotational speed of the vibration type motor 1 is detected based on the output of the pulse counting circuit 5. Here, the operation of detecting the rotation speed can be performed every predetermined cycle, or can be always performed based on the output of the pulse counting circuit 5.

  In step S4, it is determined whether or not the detected rotational speed has reached the target speed, that is, whether or not the actual rotational speed follows the target speed.

  Here, when the detected rotational speed has reached the target speed, the process returns to step S2, and the frequency is changed based on the first pattern. On the other hand, if the target speed has not been reached, the process proceeds to step S5.

  In step S5, a frequency signal having a frequency f1 is applied to the piezoelectric element 11 of the vibration type motor 1, and the frequency is changed in the second pattern shown in FIG. Here, the frequency change rate (frequency change amount per unit time) in the second pattern is smaller than the frequency change rate in the first pattern. That is, the slope of the second pattern shown in FIG. 6 is gentler than the slope of the first pattern shown in FIG.

  By changing from the first pattern to the second pattern in this way, the frequency of the frequency signal applied to the piezoelectric element 11 does not reach the lower limit value as shown in FIGS. The rotational speed can be reached to the final target speed v1. After the rotational speed of the vibration type motor 1 reaches the target speed v1, the frequency is changed according to the desired rotational speed.

  As described above, when the actual rotation speed of the vibration type motor 1 does not reach the target speed, the actual rotation speed reaches the final target speed v1 by changing the pattern for changing the frequency. It is possible to suppress the frequency from reaching the lower limit before. Thereby, the control step-out that stops the driving of the vibration type motor 1 as described above can be suppressed, and the vibration type motor 1 can be stably started.

  In this embodiment, when the actual rotational speed does not reach the target speed, the frequency of the frequency signal applied to the piezoelectric element 11 is returned to the frequency f1 at the start of driving, and then the frequency is set in the second pattern. It is changing. However, the frequency may be changed based on the second pattern from the frequency when it is determined that the actual rotational speed has not reached the target speed.

  Further, when the frequency is changed based on the second pattern and the actual rotational speed does not reach the target speed, the pattern for changing the frequency may be further changed. Specifically, the frequency can be changed based on a third pattern having a frequency change rate smaller than that of the second pattern.

  Furthermore, each time a plurality of patterns having different frequency change rates are prepared and it is determined that the actual rotational speed has not reached the target speed, the pattern of the change rate is changed from the pattern having the higher frequency change rate. You may make it switch to the pattern of a small side gradually.

  In the above description, the frequency is lowered while changing the frequency change rate until the actual rotational speed reaches the target speed, but the frequency is kept constant for a predetermined time. You can also. For example, in the state where the frequency is changed based on the first pattern (FIG. 4), when it is determined that the actual rotational speed has not reached the target speed, the frequency is kept constant for a predetermined time. Then, the frequency can be changed based on the second pattern (FIG. 6).

The figure which shows the structure of the control apparatus of a vibration type motor in Example 1 of this invention. Sectional drawing of a vibration type motor. The figure which shows the relationship between the rotational speed of a vibration type motor, and drive time. The figure which shows the relationship between the frequency of a frequency signal, and drive time. The figure which shows the rotational speed of a vibration type motor, and the relationship of time. The figure which shows the relationship between the frequency of a frequency signal, and drive time. 3 is a flowchart showing a control operation in the first embodiment. The figure which shows the drive characteristic of a vibration type motor.

Explanation of symbols

1: Vibration type motor 3: Rotary encoder 5: Pulse counting circuit 6: Drive control circuit

Claims (4)

A control device for a vibration type actuator that relatively drives a vibration body whose vibration is excited by application of a frequency signal to an electromechanical energy conversion element and a contact body that contacts the vibration body,
Detecting means for detecting a driving speed of the vibration type actuator;
Control means for controlling the drive of the vibration type actuator,
When the drive speed detected by the detection means has not reached the target speed, the control means has the detected drive speed reach the target speed in a region on a higher frequency side than a predetermined frequency. As described above, the vibration actuator control apparatus is characterized by changing the frequency of the frequency signal.   The control means is a case where the frequency is changed in a first pattern, and when the detected driving speed does not reach the target speed, the frequency is higher than that in the first pattern. A control device for a vibration type actuator, wherein the frequency is changed with a second pattern having a small change rate.   An apparatus comprising the vibration type actuator control device according to claim 1. A control method of a vibration type actuator that relatively drives a vibration body whose vibration is excited by application of a frequency signal to an electromechanical energy conversion element and a contact body that contacts the vibration body,
A first step of detecting a driving speed of the vibration actuator;
A second step of changing the frequency of the frequency signal in a first pattern;
When the frequency is changed in the first pattern, and the driving speed detected in the first step does not reach the target speed, the frequency is higher than that in the first pattern. And a third step of changing the frequency with a second pattern having a small change rate.

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