JP2010011716A - Vibrating motor controller and optical instrument using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a speed control method of a vibrating motor, which performs speed control with less influence of environmental conditions, load condition, or individual difference. <P>SOLUTION: The vibrating motor controller is provide with: a speed control means for controlling rotation speed by modifying phase difference, frequency, or amplitude of frequency signal for drive to be applied to a vibrating motor; a vibration detecting means for detecting vibration generated in the vibrating body; a phase difference detecting means for detecting the phase difference between the vibration detecting means and the frequency signal for drive. Either of the speed control is executed based on the signal from the phase difference detecting means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vibration type motor control device that controls the operation of a vibration type motor and an optical apparatus using the same. The optical apparatus is, for example, a photographing apparatus such as a still camera or a video camera, and an interchangeable lens that can be attached to and detached from the camera body.

  As a vibration type motor, as shown in FIG. 9, a vibrator in which a piezoelectric body 302 (electrostrictive element), which is an electromechanical energy conversion element, is joined to a vibrator 301 formed in an annular shape such as metal, and a vibrator is applied to the vibrator surface. There is one constituted by a contact body 303 that is in pressure contact.

  A vibration motor applies two-phase frequency voltages with different phases to a piezoelectric body to excite the surface of the vibration body to form a vibration wave (progressive vibration wave) in an out-of-plane vibration mode. As described above, the contact body that is in pressure contact with the surface and the vibrator are relatively moved. One method for controlling the speed of the vibration type motor is to change the frequency of the frequency voltage applied to the piezoelectric body. As shown in FIG. 9A, the relationship between the frequency and the speed is such that the resonance frequency (fr) is the fastest, and the speed decreases as the frequency moves away from the resonance frequency. This is because the diameter of the elliptical orbit drawn by the mass point on the surface of the vibration elastic body increases as the resonance frequency is approached. This frequency-speed characteristic has a characteristic that the speed change is more gradual and stable on the high frequency side than the resonance frequency on the low frequency side, and the frequency range higher than the resonance frequency is used for ease of control. Is being controlled. In addition, the speed decreases as the frequency is increased in the frequency region higher than the resonance frequency, but is stopped by the contact pressure between the elastic body and the contact body at a predetermined frequency (fm), and the driving force is lost. To do.

  As another speed control method for the vibration type motor, there is a method for changing the amplitude of the frequency voltage applied to the piezoelectric body. As shown in FIG. 9B, the relationship between the amplitude and the speed is a characteristic that the speed increases when the amplitude of the frequency voltage is increased, and the speed decreases when the frequency voltage is decreased. This is because when the amplitude of the frequency voltage is increased, the excitation force of the vibrator increases and the diameter of the elliptical orbit drawn by the mass point on the surface of the vibration elastic body increases. Similarly to the case of frequency control, when the amplitude of the frequency voltage is lowered to a predetermined amplitude (Vm), the vibration type motor is restrained by the contact pressure between the elastic body and the contact body and loses the driving force and stops.

  Furthermore, as another speed control method, there is a method of changing the phase difference of the frequency voltage applied to the piezoelectric body. As shown in FIG. 9C, the relationship between the phase difference and the speed is the fastest in each moving direction (rotation direction) when the phase difference is 90 deg or -90 deg, and the speed decreases as the phase difference moves away from ± 90 deg. I will do it. This is because the elliptical shape changes due to the amplitude ratio change between the amplitude in the moving direction and the amplitude in the moving direction and the vertical direction. The characteristic indicated by the solid line in FIG. 9C is a characteristic when the frequency is the resonance frequency (fr), and the characteristic indicated by the broken line is higher than the resonance frequency shown in FIG. This is the characteristic when the frequency (f0) is lower than fm. At either frequency, the driving of the vibration type motor becomes unstable when the phase difference deviates from ± 90, and stops at a predetermined phase difference. However, the lowest controllable speed when the frequency is higher than the resonance frequency (f0) is lower than when the frequency is the resonance frequency (fr). When f0 is a certain value or more, the minimum controllable speed is lower than the minimum speed controllable by frequency or amplitude.

  Based on such control characteristics of the vibration type motor, a control method that combines control by frequency or amplitude and control by phase difference has been proposed for the purpose of performing speed control widely from a high speed range to a low speed range.

  In Patent Document 1, the purpose is to reduce the rotational speed immediately before the vibration type motor stops by phase difference control. When the deviation between the drive position and the target drive position becomes smaller than a predetermined value, phase control is performed from frequency control. A method of switching to is proposed.

Patent Document 2 proposes a method of performing speed reduction control by frequency control and switching to phase difference control when a predetermined frequency is reached for the purpose of performing speed control widely from a high speed range to a low speed range. Patent Document 2 also proposes a method of switching to phase difference control when the speed is reduced by frequency control and a predetermined speed is reached.
JP-A-4-75479 Japanese Patent Laid-Open No. 10-210775

  As described above, in order to reduce the controllable speed by the phase difference control, it is necessary to set the frequency of the driving frequency voltage to a frequency higher than the resonance frequency by a certain level. In addition, the characteristics of vibration-type motors vary depending on environmental conditions such as temperature and load conditions, and also vary due to individual differences. Therefore, it is important to switch to phase difference control in consideration of these characteristic changes and variations. .

  The switching methods of Patent Document 1 and Patent Document 2 switch from frequency control to phase difference control based on the deviation, frequency, or speed between the drive position and the target drive position. It is easily affected by the surrounding environment, load conditions, and individual differences.

  In view of the above problems, the present invention proposes a speed control method that is not easily affected by characteristics, variations, and the like of vibration type motors. It is another object of the present invention to provide a vibration type motor control apparatus having the speed control method and an optical apparatus using the vibration type motor control apparatus.

In order to achieve the above-mentioned object, the present invention applies vibrations that generate a driving force by applying two-phase driving frequency signals having different phases to a vibrating body provided with a piezoelectric body to excite the vibrating body. Type motor, vibration detection means for detecting the vibration state of the vibrating body, phase difference detection means for detecting a phase difference between the signal from the vibration detection means and the driving frequency signal, and two phases having different phases A frequency changing means for changing the frequency of the driving frequency signal and a phase difference changing means for changing the phase difference between the two driving frequency signals having different phases, and controlling the rotational speed of the vibration type motor. A vibration type motor control device comprising: a speed control means that:
If the phase difference detected by the phase difference detecting means is on the phase difference side corresponding to the resonance frequency of the vibration type motor with respect to the first predetermined value, the rotational speed is controlled by the frequency changing means, When the phase difference is not on the side corresponding to the resonance frequency, the rotational speed is controlled by the phase difference changing means.

  According to the present invention, in the speed control of the vibration type motor, either the frequency or the phase difference of the driving frequency signal is determined based on the phase difference between the signal indicating the vibration state of the vibration type motor generated in the piezoelectric body and the driving frequency signal. The speed is controlled by changing the above. As a result, it is possible to perform speed control that is not easily affected by the characteristics and variations of the vibration type motor.

  FIG. 11 is a block diagram of a camera system that can be used in the present invention and can be cited as an optical apparatus (photographing device) having a camera body and an interchangeable lens that is detachable from the camera body.

  In FIG. 11, 201 is a camera body, and 202 is an interchangeable lens. The camera main body 201 includes an electric circuit unit 203 and a power source 210. The electric circuit unit 203 includes a photometry unit 204, a distance measurement unit 205, a shutter 206, a feeding charge system 207, a camera main body CPU 208, communication. Means 209 are included. The photometry unit 204 measures the amount of light that has passed through the interchangeable lens, and the distance measurement unit 205 measures the distance from the film surface to the subject. The shutter 206 exposes the film for an appropriate time. The feeding charge system 207 performs film winding and rewinding. The camera body CPU 208 controls the camera, and the communication unit 209 performs serial communication with the lens.

  The interchangeable lens 202 includes a focusing lens 211, a zooming lens 212, a diaphragm 213, a zoom position detection brush 214, an encoder 215, and an electric circuit unit 217. Here, the focusing lens 211 and the zooming lens 212 are optical elements. The zoom position detection brush 214 detects the position of the zooming lens 212, and the encoder 215 detects the position of the focusing lens 211.

  The electrical circuit unit 217 includes a communication unit 218, an in-lens CPU 219, a lens drive control unit 220, a vibration type motor 221, an aperture control unit 222 for performing aperture drive control, and an aperture drive motor 223. The communication means 218 performs serial communication with the camera, and the in-lens CPU 219 performs control within the interchangeable lens. The lens drive control unit 220 drives and controls the focusing lens by a vibration type motor 221 that is a lens driving motor. The aperture control unit 222 controls the driving of the aperture by the aperture driving motor 223. In the present invention, a vibration type motor is used as the lens driving motor 221, and a control algorithm for the vibration type motor is built in the in-lens CPU 219.

  FIG. 1 shows a vibration type motor control system that can be used in the present invention. 1 corresponds to the in-lens CPU 219, the lens drive controller 220, and the lens drive motor 221 of FIG.

  Reference numeral 1 denotes a microcomputer (hereinafter referred to as a microcomputer) for controlling a vibration type motor, 2 a power source (battery), 3 a regulator, which supplies the output voltage to the microcomputer 1 and at the same time a reference power source for phase difference detecting means described later Also used as In the present invention, the microcomputer 1 functions as speed control means, and is incorporated as a part of the in-lens CPU 219 in FIG. However, the microcomputer 1 may perform all control within the lens as the in-lens CPU 219 itself.

  Reference numeral 4 denotes a step-up DCDC converter which is a power supply circuit applied to the vibration type motor. The DCDC converter 4 is configured so that operation / non-operation can be controlled by the microcomputer 1.

  A voltage controlled oscillator (VCO) 5 generates a frequency voltage based on a frequency data signal (FDATA) input from the microcomputer 1. The frequency voltage is output to the frequency divider / phaser 6, and the frequency divider / phaser applies the frequency voltage to the vibration type motor based on the frequency voltage. In other words, the present invention functions as frequency changing means for changing the frequency of the two-phase driving frequency signals having different phases applied to the vibration type motor. In this embodiment, the frequency data signal (FDATA) is 8-bit data, and the frequency is maximum when FDATA = H00, and the frequency is minimum when FDATA = HFF. It is assumed that the frequency when FDATA = H00 is sufficiently larger than the resonance frequency of the vibration type motor.

  The frequency divider / phaser 6 is a two-phase rectangle having a phase difference corresponding to the phase difference data signal based on the frequency voltage of the VCO 5, a predetermined clock signal, and the phase difference data signal (PDATA) input from the microcomputer 1. Wave signals (A phase, B phase) are output to the vibration type motor. In other words, in the present invention, it functions as a phase difference changing means for changing the phase difference between two-phase driving frequency signals having different phases applied to the vibration type motor. The phase difference between the two-phase rectangular wave signals (A phase and B phase) is referred to as a drive phase difference θk, and is distinguished from a phase difference for detecting a vibration state described later. In this embodiment, the phase difference data signal (PDATA) is 8-bit data. When PDATA = H00, the driving phase difference is 0 deg (same phase), and when PDATA = H80, the driving phase difference is 180 deg (reverse phase). Shall. The frequency divider / phaser 6 is permitted / prohibited to output two rectangular wave signals (A phase and B phase) in response to an output permission signal (OUT-EN) input from the microcomputer 1.

  7 is an A-phase side inverter, and 8 is a B-phase side inverter. Reference numeral 9 denotes an NPN transistor for supplying power on the A phase side, 10 denotes an NPN transistor for supplying power on the B phase side, 11 denotes an NPN transistor on the A phase side, and 12 denotes an NPN transistor on the B phase side. The A-phase signal of the frequency divider / phase shifter 6 is input to the A-phase side inverter 7 and the A-phase side NPN transistor 11, and the output of the inverter 7 is connected to the base of the NPN transistor 9 to the A-phase side of the vibration type motor. The power is sinked / sourced. Similarly, the B-phase signal of the frequency divider / phaser 6 is input to the B-phase side inverter 8 and the B-phase side NPN transistor 12, and the output of the inverter 8 is connected to the base of the NPN transistor 10 to connect the B-phase of the vibration type motor. The power is sinked / sourced to the side.

  13 is an A phase side coil, 14 is a B phase side coil, 15 is an A phase side capacitor, and 16 is a B phase side capacitor. A boosted voltage corresponding to the frequency applied by connecting the A-phase side coil 13 and the A-phase side capacitor 15 in series with the power source is applied to the A-phase of the vibration type motor. Similarly, a boosted voltage corresponding to the frequency applied by connecting the B-phase side coil 14 and the B-phase side capacitor 16 in series with the power supply is applied to the B-phase of the vibration type motor.

  Reference numeral 17 denotes an A phase side electrode of the vibration type motor, 18 denotes a B phase side electrode of the vibration type motor, 19 denotes an S phase side electrode (vibration detecting means) of the vibration type motor, 20 denotes a piezoelectric body, and 21 denotes a GND electrode.

  Reference numeral 22 denotes a voltage dividing circuit for halving the output voltage of the regulator 3, and forms a threshold voltage of the comparator.

  Reference numerals 23 and 24 are B-phase voltage level shift resistors, 25 and 26 are B-phase voltage high-pass filters, 27 and 28 are S-phase voltage level-shift resistors, and 29 and 30 are S-phase voltage high-pass filters. Each filter is configured.

  Reference numeral 31 denotes a B-phase comparator which shifts the level to the voltage of the regulator 3 and simultaneously shapes the waveform of the B-phase voltage. Reference numeral 32 denotes an S-phase comparator that shifts the level to the voltage of the regulator 3 and simultaneously shapes the waveform of the S-phase voltage.

  In other words, in the present invention, the microcomputer 1, the resistors 27 and 28, the high-pass filters 29 and 30, and the comparator 32 have a phase difference (vibration level) between the drive voltage to the B-phase side electrode 18 and the output voltage from the S-phase side electrode 19. The phase difference detecting means for detecting the phase difference θs) is configured.

  FIG. 2 is a conceptual diagram of a method for detecting the vibration phase difference θs. A voltage waveform (B) of the B-phase side electrode 18, a voltage waveform (S) of the S-phase side electrode 19, and a waveform obtained by converting each signal into a digital signal (Cb, Cs) through the comparators 31 and 32 are shown. Yes. Each comparator output signal (Cb, Cs) is input to the microcomputer 1 and the period from when Cb becomes H to when Cs becomes H is measured using a timer function built in the microcomputer to obtain the vibration phase difference θs. .

  Reference numeral 33 denotes an encoder that detects the rotation amount and rotation speed of the vibration type motor. The encoder 33 is a known optical encoder that is configured by, for example, a pulse rotating plate rotating in synchronization with the rotation of the vibration type motor and having a plurality of slits in the radial direction and a photo interrupter. The optical encoder changes the signal when the light projected from the LED of the photo interrupter reaches the light receiving element or is blocked. Reference numeral 34 denotes a detection circuit of the encoder 33, which amplifies a weak output signal of the photo interrupter to generate a waveform and inputs the waveform to the microcomputer 1 as a pulse signal. The amount of rotation is detected by counting the change of the pulse signal by the count function built in the microcomputer 1, and the speed is detected by measuring the pulse width of the pulse signal by the timer function built in the microcomputer 1.

  Next, the vibration type motor will be described with reference to FIG. A vibration type motor (not shown) is composed of a rotor and a stator, and FIG. 3 is a view showing an arrangement state of electro-mechanical energy conversion elements such as piezoelectric bodies (electrostrictive elements) arranged on the surface of the stator.

  A1 and B1 in FIG. 3 are first and second electrostrictive element groups arranged on the stator in the illustrated phase and polarization relationship, respectively. S1 is an electrostrictive element for a sensor arranged at a position where the phase of 45 deg is shifted from the first electrostrictive element group B1. Each of the electrostrictive elements as the electro-mechanical energy conversion elements may be a single element attached to the vibrating body or may be integrally polarized.

  The A-phase side electrode 17, the B-phase side electrode 18, and the S-phase side electrode 19 shown in FIG. 1 are respectively a first electrostrictive element group A1, a second electrostrictive element group B1, and a sensor electrostrictive element S1. Electrode. Progressive vibration waves are formed on the surface of the stator by applying two-phase frequency voltages (drive frequency signals) having different phases to the A-phase side electrode 17 and the B-phase side electrode 18.

  When the vibration wave is formed on the vibrating body, the sensor electrostrictive element S1 outputs a frequency voltage according to the state of the vibration wave, and this is detected by the S-phase side electrode 19. The vibration type motor has a characteristic in which there is a vibration phase difference between the drive voltage to the B-phase side electrode 18 and the output voltage from the S-phase side electrode 19. This vibration phase difference characteristic is determined by the positional relationship between the electrostrictive element group B1 to which the frequency signal is applied by the B-phase side electrode 18 and the sensor electrostrictive element S1. In the case of the present embodiment, the resonance state is shown when the vibration phase difference is deviated by 45 deg during forward rotation, and the resonance state is shown when it is deviated by 135 deg during reverse rotation. Further, the vibration phase difference increases as the resonance state shifts.

  FIG. 4A is a diagram showing frequency-vibration phase difference characteristics and frequency-rotational speed characteristics of the vibration motor during normal rotation. The horizontal axis represents the drive frequency f, and the vertical axis 1 represents the vibration phase difference θs. The vertical axis 2 indicates the rotational speed N. In the figure, the frequency f is higher on the right side, the vibration phase difference θs is lower on the lower side, and the rotational speed N is higher on the upper side. A vibration type motor can be driven at the highest efficiency and at a high speed when driven at a resonance frequency at which resonance occurs. However, when the drive signal frequency is slightly shifted from the resonance frequency to the low frequency side as shown in the figure, the rotational speed of the vibration type motor suddenly decreases or stops. In order to prevent such a rapid decrease in rotational speed and stop, a control method is used that controls the drive signal frequency f so as not to oscillate below the resonance frequency based on the vibration phase difference θs. That is, the detected vibration phase difference θs is compared with a preset second reference phase difference (θsl: 45 ° <θsl <θs0 is satisfied). Therefore, when the phase is on the phase difference side corresponding to the resonance frequency from θsl (in the drawing, θsl or less), processing such as changing the drive signal frequency to a higher frequency side than the resonance frequency side is performed.

  The frequency-rotational speed characteristics shown in FIG. 4A are characteristics when the drive phase difference is 90 deg. The vibration type motor starts to move at a certain frequency fm (startup frequency) by scanning the drive frequency from higher to lower, and the rotational speed increases by scanning further at the lower frequency. However, this characteristic changes depending on environmental conditions such as temperature and load conditions, and further varies due to individual differences. The vibration phase difference θs is not easily affected by variations in the frequency-rotational speed characteristic caused by these conditions, and a certain value corresponds to a certain part of the frequency-rotational speed characteristic curve that is approximately the same. The present invention uses this characteristic to perform control switching of speed control that is not easily affected by the above-described variations. FIG. 4B shows drive phase difference-rotational speed characteristics, where the horizontal axis indicates the drive phase difference θk and the vertical axis indicates the rotational speed N. The drive phase difference-rotational speed characteristic shown in FIG. 4B is a characteristic when the drive frequency is set to a frequency sufficiently higher than the resonance frequency shown in FIG. 4A and lower than fm (f0). is there. When the drive phase difference is set to 90 deg, the rotation speed becomes maximum (N0). When the drive phase difference is reduced from 90 deg, the rotation speed is reduced and stops at a predetermined drive phase difference. The rotation speed Nθmin at the time of the stop is lower than the rotation speed Nfmin at the frequency fm in FIG.

  Next, a control example of the vibration type motor according to the present invention will be shown. The vibration type motor control device is first instructed by a target rotation speed for driving from a control system for the entire device on which the vibration type motor and elements driven by the vibration type motor are mounted.

  For example, in a camera system including an interchangeable lens and a camera body to which the interchangeable lens can be attached and detached, a command signal for target rotation speed is transmitted from the CPU of the camera body to the CPU of the vibration type motor control device in the interchangeable lens.

  The vibration type motor control device has a function of causing the rotational speed to reach the target rotational speed and maintaining the target rotational speed. The present invention relates to switching of speed control (frequency control, phase difference control) in such a speed control method of a vibration type motor.

  In the present embodiment, the vibration state of the vibration type motor is detected at any time during driving of the vibration type motor, and the vibration phase difference θs from the driving frequency signal applied to the vibration type motor is detected. Based on the detected phase difference, speed control is performed by changing either the frequency or the phase difference by the speed control means. Details will be described below.

  In driving the vibration motor, first, a target rotational speed (T-SPD) and a driving amount (FOPC) are instructed from inside or outside the microcomputer. The microcomputer 1 starts to control the vibration type motor using this instruction as a trigger. The target rotational speed (T-SPD) is information for controlling the vibration type motor at a predetermined rotational speed, and is information corresponding to the pulse width of the aforementioned pulse signal. The driving amount (FOPC) is information corresponding to the count value of the pulse signal.

  Control from the start of driving to the end of driving will be described using an example in which the vibration type motor is driven in the forward direction with reference to FIGS.

<Figure 5>
[STEP1]
The microcomputer 1 generates a voltage necessary for operating the DCDC converter 4 to drive the vibration type motor. The frequency data (FDATA) is set to H00 to be the maximum frequency, the phase difference data (PDATA) is set to H00, and the drive phase difference θk is set to 0 deg. In addition, after reading the current pulse count value and saving it as FPC0, the output permission signal (OUT-EN) is set to H, thereby permitting the output of two rectangular wave signals (A phase and B phase) and vibrating motor Start driving.

[STEP2]
It is determined whether a pulse signal is input from the encoder 33. By this determination, the timing at the start of motor driving and the timing of the speed control instruction during driving are detected. If a pulse signal is input, the process proceeds to [STEP 3], and if there is no input, the process proceeds to [STEP 13].

[STEP3]
Since it is determined in [STEP 2] that a pulse signal has been input, the pulse count value indicating the current position has changed. Therefore, a pulse count value FPC indicating the current position is acquired. In the case of the first pulse signal input after the start of driving, it is determined that the vibration type motor has started, and the start flag is set to 1. It is assumed that the activation flag is cleared to 0 in the drive start process.

[STEP4]
Since the pulse signal is input in [STEP 2], the pulse width measurement value (R-SPD) is read. R-SPD represents the current rotational speed.

[STEP5]
The value of the pulse width measurement timer is reset and restarted so that the pulse width measurement value can be obtained when the next pulse signal is input.

[STEP6]
Set the target rotation speed.

  It is determined whether FOPC- (FPC-FPC0), which is the remaining drive amount to the target stop position, is equal to or less than the deceleration pulse, and if it is equal to or less than the deceleration pulse, a new T-SPD is used to change the target rotational speed. get. Here, the deceleration pulse is a drive amount for starting a predetermined deceleration, and T-SPD is read from a predetermined remaining drive amount-target rotational speed data table and set. As a result, when the speed is less than or equal to the deceleration pulse, the target rotational speed is updated so as to gradually decelerate and stop.

[STEP7]
The R-SPD representing the current rotational speed acquired in [STEP 4] is compared with the T-SPD representing the target rotational speed. If the R-SPD is larger, the process proceeds to [STEP 9], otherwise the process proceeds to [STEP 8]. Here, since R-SPD and T-SPD are data of pulse width, the fact that R-SPD is larger means that the current speed is slower than the target rotational speed.

[STEP8]
The rotational speed R-SPD is compared with the target rotational speed T-SPD. If the R-SPD is smaller, the process proceeds to [STEP 10], and otherwise, the process returns to [STEP 2].

[STEP9]
Since it is determined that it is slower than the target rotation speed, a speed-up process is performed to increase the speed of the vibration type motor. This speed-up process is a feature of the present embodiment and will be described later with reference to FIG.

[STEP 10]
Since it is determined that the speed is higher than the target rotation speed, a speed reduction process is performed to reduce the speed of the vibration type motor. This speed reduction process is a feature of the present embodiment and will be described later with reference to FIG.

[STEP 11]
It is determined whether or not the remaining drive amount FOPC- (FPC-FPC0) is zero. If 0, proceed to [STEP 12], and if there is still a remaining drive amount, return to [STEP 2].

[STEP 12]
Since the target position has been reached, the output permission signal (OUT-EN) is set to L to prohibit the output of two rectangular wave signals (A phase and B phase), and the drive of the vibration type motor is stopped. Further, the DCDC converter 4 is stopped.

[STEP 13]
This is processing when it is determined in [STEP 2] that there is no input of a pulse signal, and it is determined whether or not the vibration type motor has already been activated. If the activation flag is 0, the process proceeds to [STEP 9] and the speed increase process is performed. If the activation flag is 1, the process proceeds to [STEP 14].

[STEP14]
R-TIM, which is the current value of the pulse width measurement timer, is read. This R-TIM represents the time from the previous pulse input to the present time.

[STEP 15]
R-TIM and UP-TIM are compared, and if R-TIM is smaller than UP-TIM, this process is terminated. This is a process for preventing the speed from becoming too slow despite stopping.

<Fig. 6>
[STEP21]
It is determined whether or not PDATA = H40 (θk = 90 deg). If PDATA = H40, it can be determined that the frequency control is being performed, and thus the process proceeds to [STEP 22]. If PDATA <H40, it is determined that the phase difference control is being performed, and the process proceeds to [STEP 23].

[STEP22]
Set PDATA = PDATA + ΔPUP, and proceed to [STEP 11].

  In [STEP 1], PDATA is set to the initial value H00, and the driving phase difference θk is set to 0 deg to start driving. Therefore, in order to drive in the normal rotation direction and increase the speed, it is necessary to increase PDATA and bring the drive phase difference θk close to 90 deg. ΔPUP is a constant that determines the degree of acceleration and may be a fixed value, but may be changed according to a speed deviation or the like. If PDATA> H40 as a result of this processing (PDATA = PDATA + ΔPUP), PDATA = H40 is set.

[STEP23]
Set FDATA = FDATA + ΔFUP and proceed to [STEP 11].

  In [STEP22], when the driving phase difference θk is increased to 90 deg (PDATA = H40), and further speed up is required, in order to increase the speed, FDATA is increased and the frequency f is decreased to the resonance frequency. It needs to be close. ΔFUP is a constant that determines the degree of acceleration, and may be a fixed value, but may be changed according to a speed deviation or the like.

<Fig. 7>
[STEP 31]
It is determined whether or not PDATA = H40 (θk = 90 deg). If PDATA = H40, it can be determined that speed control equal to or higher than the rotational speed that can be controlled by phase difference control, that is, frequency control is being performed, and the process proceeds to [STEP 32]. In the case of PDATA <H40, it can be determined that the phase difference control is being performed, and thus the process proceeds to [STEP 35].

[STEP 32]
A measured value (θs) of a vibration phase difference that is a phase difference between the drive voltage to the B-phase side electrode 18 and the output voltage from the S-phase side electrode 19 is read.

[STEP33]
Speed control switching processing is performed.

  It is determined whether θs <θs0. Here, θs0 is a phase difference value (phase difference of the first reference) as a reference for speed control switching as shown in FIG. 4A, and the corresponding frequency value f0 is fm <f0 <fr. Meet.

  When θs <θs0, θs is on the phase difference (45 ° in this embodiment) side corresponding to the resonance frequency fr. That is, the drive signal frequency f corresponding to θs is a value lower than f0 and closer to the resonance frequency fr. Therefore, it is determined that the speed reduction process should be performed by frequency control, and the process proceeds to [STEP 34].

  When θs ≧ θs0, θs is not the phase difference side corresponding to the resonance frequency fr. That is, the drive signal frequency f corresponding to θs is higher than f0 and farther from the resonance frequency fr. Therefore, it is determined that the speed reduction process should be performed by switching to the phase difference control, and the process proceeds to [STEP 35].

[STEP34]
Set FDATA = FDATA−ΔFDN, and proceed to [STEP 11].

  In order to decrease the speed by frequency control, it is necessary to decrease FDATA, increase the drive signal frequency f, and move away from the resonance frequency. Note that ΔFDN is a constant that determines the degree of deceleration, and may be a fixed value, but may be changed according to a speed deviation or the like. For example, when ΔFDN is set in a proportional relationship with the value of the speed deviation, when the current rotation speed approaches the target rotation speed, the speed change is performed gently. By doing this, it is possible to control the vibration type motor more smoothly than when ΔFDN is set to a fixed value.

[STEP 35]
Switch to phase difference control to perform speed down processing.

  Set PDATA = PDATA−ΔPDN, and proceed to [STEP 11].

  In order to reduce the speed by the phase difference control, it is necessary to reduce PDATA and bring the drive phase difference θk close to 0 deg. ΔPDN is a constant for determining the degree of deceleration and may be a fixed value, but may be changed according to a speed deviation or the like. For example, when ΔPDN is set in correspondence with the value of the speed deviation in a proportional relationship, when the current rotational speed is close to the target rotational speed, the speed is gradually changed. By doing this, it is possible to control the vibration type motor more smoothly than when ΔFDN is set to a fixed value.

  Next, the operation of the above embodiment will be described with reference to FIG. In the example described, the target rotational speed is set to a speed corresponding to the rotational speed Np larger than the rotational speed N0 shown in FIG.

  The horizontal axis of (a)-(d) of Drawing 8 shows time. The vertical axis of (a) is the drive phase difference θk, and the upward direction indicates a large phase difference. The vertical axis of (b) is the drive signal frequency f, and the upward direction indicates a high frequency. (C) is the vibration phase difference θs, and the upward direction indicates a large phase difference. (D) is the rotational speed N, and the upward direction indicates a high rotational speed.

  Driving is started by setting the driving signal frequency f to the maximum frequency and the driving phase difference θk to 0 deg. First, the vibration type motor is accelerated by making the driving phase difference θk approach 90 deg. The drive phase difference θk becomes 90 deg at the timing A in FIG. 8, and the subsequent acceleration is performed by lowering the drive signal frequency f. Since the target rotational speed Np is reached at the timing B in FIG. 8, the decrease in the drive signal frequency f is stopped, and thereafter the operation of the drive signal frequency f is not performed unless there is a change in the rotational speed due to load fluctuation or the like. The timing C in FIG. 8 is the timing when the remaining drive amount reaches a predetermined amount, and thereafter the target rotational speed is decreased. Along with this, the drive signal frequency f is increased to reduce the speed. The timing D in FIG. 8 is the timing when the vibration phase difference θs becomes θs0, and the subsequent deceleration is performed by reducing the drive phase difference θk. The timing E in FIG. 8 is the timing when the remaining drive amount becomes 0, and the drive of the vibration type motor is stopped.

  As described above, the speed control is executed by changing either the frequency or the phase difference based on the vibration phase difference between the drive frequency voltage and the output voltage from the sensor electrostrictive element. This makes it possible to perform stable speed control that is less affected by environmental conditions, load conditions, and individual differences.

  Conventionally, the driving frequency is set at a predetermined interval on the lower frequency side than fm in consideration of environmental conditions, load conditions, and individual differences so as not to exceed the frequency fm in FIG. It was necessary to provide a reference value for control switching. However, by the stable operation of the reference value of the present invention, the predetermined interval can be further narrowed, and phase difference control having a slower controllable speed can be realized.

  In the present embodiment, the vibration state of the vibration type motor is detected using the amplitude of the output voltage (vibration amplitude Vs) from the S-phase side electrode 19 instead of the vibration phase difference θs. The vibration amplitude Vs can be detected by using a known amplitude detection circuit as the amplitude detection means in the circuit of FIG. 1 instead of the phase difference detection means.

  FIG. 10A is a diagram showing frequency-vibration amplitude characteristics and frequency-rotational speed characteristics. The horizontal axis represents the driving frequency f, the vertical axis 1 represents the vibration amplitude Vs, and the vertical axis 2 represents the rotational speed N. ing. The frequency-rotational speed characteristic is a characteristic when the drive phase difference is 90 deg. Like the vibration phase difference θs, the vibration amplitude Vs is not easily affected by variations in the frequency-rotational speed characteristics caused by conditions such as the environment and individual differences, and a certain value is a part of a frequency-rotational speed characteristic curve having approximately the same value. It corresponds.

  That is, by replacing the vibration phase difference θs with the vibration amplitude Vs in the first embodiment and performing similar control, the same effect as in the first embodiment can be expected. Specifically, vibration amplitude data (Vs) is acquired at a step corresponding to [STEP 32], and Vs> Vs0? At a step corresponding to [STEP 33]? Perform conditional branching. Here, Vs0 is an amplitude value serving as a reference for speed control switching (a first reference amplitude). The difference between the direction of the vibration phase difference θs and the condition branch inequality sign is that the vibration amplitude is monotonically decreasing with respect to the frequency in the vicinity of Vs0 as shown in FIG.

  As described above, speed control is executed by changing either the amplitude or the phase difference based on the vibration phase difference between the drive frequency voltage and the output voltage from the sensor electrostrictive element. This makes it possible to perform stable speed control that is less affected by environmental conditions, load conditions, and individual differences.

  Further, phase difference control having a slower controllable speed can be realized as in the first embodiment.

  In the above-described two embodiments, an example in which the frequency and the phase difference are switched is described as a method for controlling the rotational speed of the vibration type motor. However, the present invention can also be applied to a speed control method for switching the amplitude and the phase difference using the above-described amplitude control (FIG. 9B) instead of the frequency control. In this case, the VCO 5 functions as an amplitude changing unit.

Vibration type motor control system diagram according to the present invention Conceptual diagram of vibration phase difference detection Piezoelectric arrangement diagram Rotational speed characteristic diagram of vibration type motor in first embodiment Control flow chart of vibration type motor Control flow chart in speed-up processing of vibration type motor Control flow chart in speed reduction processing of vibration type motor Each parameter characteristic diagram in the speed control according to the present invention Rotational speed characteristics diagram for each parameter of vibration type motor Rotational speed characteristic diagram of vibration type motor in the second embodiment Camera system to which the present invention is applied

Explanation of symbols

1 Microcomputer 5 VCO
6 Divider / Phaser 31 B Phase Signal Comparator 32 S Phase Signal Comparator 33 Encoder 34 Detection Circuit

Claims (6)

A vibration type motor that generates a driving force by applying two-phase driving frequency signals having different phases to a vibrating body provided with a piezoelectric body to excite the vibrating body;
Vibration detecting means for detecting a vibration state of the vibrating body;
Phase difference detecting means for detecting a phase difference between the signal from the vibration detecting means and the driving frequency signal;
Frequency changing means for changing the frequency of the two-phase driving frequency signals having different phases;
Phase difference changing means for changing the phase difference between the two-phase driving frequency signals having different phases;
In a vibration type motor control device comprising: a speed control means for controlling the rotational speed of the vibration type motor;
The speed control means is
When it is determined that the phase difference detected by the phase difference detection means is on the phase difference side corresponding to the resonance frequency of the vibration type motor with respect to the first reference phase difference, the frequency change means A vibration type motor control device that controls a rotational speed and controls the rotational speed by the phase difference changing means when it is determined that the phase difference is not on the phase difference side corresponding to the resonance frequency.   The speed control unit is configured to detect a phase difference detected by the phase difference detection unit with respect to a second reference phase difference between the first reference phase difference and the phase difference corresponding to the resonance frequency. 2. The vibration type motor according to claim 1, wherein when it is determined that the phase difference side corresponds to the resonance frequency, the frequency of the driving frequency signal is changed to a frequency that is not the resonance frequency side. Control device. A vibration type motor that generates a driving force by applying two-phase driving frequency signals having different phases to a vibrating body provided with a piezoelectric body to excite the vibrating body;
Vibration detecting means for detecting a vibration state of the vibrating body;
Phase difference detecting means for detecting a phase difference between the signal from the vibration detecting means and the driving frequency signal;
Amplitude changing means for changing the amplitude of the two-phase driving frequency signals having different phases;
Phase difference changing means for changing the phase difference between the two-phase driving frequency signals having different phases;
In a vibration type motor control device comprising: a speed control means for controlling the rotational speed of the vibration type motor;
The speed control means is
When it is determined that the phase difference detected by the phase difference detection means is on the phase difference side corresponding to the resonance frequency of the vibration type motor with respect to the first reference phase difference, the amplitude change means A vibration type motor control device that controls a rotation speed and controls the rotation speed by the phase difference changing means when it is determined that the phase difference is not on the phase difference side corresponding to the resonance frequency. The vibration type motor control device according to any one of claims 1 to 3,
An optical element driven by the vibration type motor;
An optical apparatus comprising:   The optical apparatus according to claim 4, wherein the optical apparatus is an interchangeable lens that can be attached to and detached from a camera body.   The optical apparatus according to claim 4, wherein the optical apparatus is a photographing apparatus.

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