JP2021016074A - Control apparatus of actuator, control method, and imaging apparatus - Google Patents

Abstract

To provide a control apparatus enabling the operation of an actuator, which is suitable for noise suppression and controllability by switching a power conduction system in accordance with a control command value.SOLUTION: A control apparatus of an actuator, switches a first power conduction system having a relatively small distortion and a relatively large ripple current and a second power conduction system having a relatively large distortion and a relatively small ripple current to control an output of a signal of a PWM (pulse width modulation) waveform. A control part of the control apparatus selects the second power conduction system when a command value is zero (S411). The control part selects the first power conduction system when a driving amount corresponding to the command value is within a range of a blind sector near a zero cross excluding zero (S403), and selects the second power conduction system when the magnitude of the driving amount corresponding to the command value is within a range exceeding the blind sector (S404).SELECTED DRAWING: Figure 1

Description

The present invention relates to PWM (Pulse Width Modulation) control of an actuator.

An image pickup device having an image blur correction function is equipped with, for example, a camera shake correction mechanism (image plane vibration isolation mechanism) for moving an image sensor in parallel. Since the actuator is arranged in the vicinity of the image sensor, it is necessary to pay attention to the generation of magnetic noise in the mechanism portion that moves the image plane by utilizing the magnetic interaction. Generally, an actuator called a flat VCM (Voice Coil Motor) is used for the image plane vibration isolation mechanism, and magnetic noise may be generated.

The inverter disclosed in Patent Document 1 is capable of suppressing the generation of noise with high efficiency without current disturbance near the zero cross where the polarities are exchanged. A method is disclosed in which the upper arm and the lower arm of each leg are alternately turned on and off in a PWM method during a predetermined period including the zero cross, and only one arm of each leg is turned on and off except for the predetermined period.

Japanese Unexamined Patent Publication No. 2014-64363

According to Patent Document 1, by a method using only two potentials of V and −V in a predetermined period including zero cross, it is possible to control with a small influence of the dead time due to the dead time even when the actuator is driven minutely. However, when PWM control is performed by a method using only two potentials of V and −V, the magnetic noise becomes relatively large. In particular, there is a problem in using the method of Patent Document 1 when giving a control instruction to make the actuator stationary at the time of imaging like an imaging device. If the generation of magnetic noise is not suppressed, noise will be mixed in the image plane information when the signal is read from the image sensor.
An object of the present invention is to provide a control device capable of operating an actuator suitable for noise suppression and controllability by switching an energization method according to a control command value.

The device of the embodiment of the present invention is a control device that controls an actuator by pulse width modulation control, and is a first energization method having a relatively small distortion and a relatively large ripple current, and a relatively strain. It has a control means for outputting a control signal by switching between a second energization method having a large value and a relatively small ripple current, and a drive means for driving the actuator according to the control signal. The control means selects the first energization method at the first command value, and selects the second energization method at a second command value larger than the first command value.

According to the present invention, it is possible to provide a control device that enables operation of an actuator suitable for noise suppression and controllability by switching the energization method according to a control command value.

It is a flowchart explaining the determination of switching of the energization method in embodiment of this invention. It is a central sectional view (A) of the image pickup apparatus, and block diagram (B) which shows the electrical structure. It is an exploded perspective view of the image blur correction mechanism part. It is a figure explaining the generation of magnetic flux and the influence on an image sensor. It is a figure explaining the relationship between PWM control and striped noise. It is a figure explaining the drive circuit. It is a figure explaining the state of voltage and current in a plurality of energization methods. It is a figure explaining the waveform example and distortion in the forward / reverse energization. It is a figure explaining the waveform example and distortion by on-short energization. It is a flowchart explaining the determination of the switching of the energization method in 2nd Embodiment. It is a figure which shows the image blur correction mechanism part in the state rotated in the direction around an optical axis.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[First Embodiment]
A control device for controlling the actuator by pulse width modulation control will be described with reference to FIGS. 1 to 9. FIG. 1 is a flowchart for explaining the determination of switching of the energization method in the embodiment, and the details thereof will be described later. FIG. 2 is a diagram showing a configuration example of an imaging device.

FIG. 2A is a central sectional view schematically showing the image pickup apparatus 1. As an example of the image pickup apparatus 1, an interchangeable lens type camera used by attaching the lens unit 2 to the apparatus main body will be described. The lens unit 2 includes an imaging optical system 3 including a plurality of lenses and diaphragms. The optical axis of the imaging optical system 3 is indicated by the optical axis 4. The lens system control unit (hereinafter referred to as a lens control unit) 12 can communicate with the control unit in the device main body of the image pickup device 1 via the electrical contact 11.

The device main body of the image pickup device 1 is provided with an image pickup element 6, and a display device 9a is provided on the back surface thereof. The user can observe the subject with the electronic viewfinder (EVF) 9b. The main body of the device includes a blur correction unit 14 that corrects image blur of the captured image, and a blur detection unit 15 that detects the shake of the device due to camera shake or the like. The shutter mechanism 16 is arranged on the subject side with respect to the image sensor 6 and is used for controlling the exposure time.

FIG. 2B is a block diagram showing the main components of the imaging system. The imaging system includes an imaging unit, an image processing unit, a recording / reproducing unit, and a control unit. The image pickup unit includes an image pickup optical system 3, an image sensor 6, and a shutter mechanism unit 16. The recording / reproducing unit includes a storage unit 8 and a display unit 9 (FIG. 2A: display device 9a, EVF9b). The control unit includes a camera system control unit (hereinafter referred to as a camera control unit) 5, an operation detection unit 10, a lens control unit 12, a lens drive unit 13, a blur correction unit 14, and a blur detection unit 15.

The lens control unit 12 controls the drive of the focus lens, the image blur correction lens, the aperture, and the like via the lens drive unit 13. The image sensor 6 receives light from the subject via the image pickup optical system 3 and the shutter mechanism unit 16, and outputs an electric signal by photoelectric conversion. The image processing unit 7 acquires the image signal output by the image sensor 6 and executes development processing and the like. The image data after image processing is stored in the storage unit 8.

The blur detection unit 15 can detect rotation about the optical axis 4 as a central axis, and detects rotational blur of the imaging device in the pitch direction, yaw direction, and roll direction. For example, runout detection is performed using a gyro sensor or the like, and the runout detection signal is output to the camera control unit 5.

The camera control unit 5 controls the control of the image pickup apparatus 1 and the lens unit 2 according to the operation signal detected by the operation detection unit 10. The camera control unit 5 includes a CPU (Central Processing Unit), and the CPU executes a predetermined program to perform various processes in the imaging system.

The blur correction unit 14 corrects image blur according to a control command from the camera control unit 5. The blur correction unit 14 includes a mechanism unit that moves the image sensor 6 in the translational direction in a plane orthogonal to the optical axis 4 and rotates the image sensor 6 with the optical axis 4 as the central axis. The specific structure will be described later.

Next, the operation of the image pickup apparatus 1 will be described. The light from the subject is imaged on the image pickup surface of the image pickup device 6 via the image pickup optical system 3. The focus evaluation amount and the exposure amount are obtained from the output signal of the image sensor 6, and the optical adjustment process of the image pickup optical system 3 is executed based on the information. That is, the image sensor 6 is properly exposed, and the image sensor 6 corresponds to the subject image.

The shutter mechanism unit 16 controls the image sensor 6 to block light by moving the shutter curtain. The shutter mechanism unit 16 includes a light-shielding member (mechanical rear curtain), and the shutter mechanism unit 16 completes the exposure to the image sensor 6. In the image sensor 6, the processing of the electronic front curtain is performed prior to the traveling of the rear curtain of the shutter mechanism unit 16. This is a process of controlling the timing of exposure start by resetting the electric charge for each line. In the electronic front curtain mode, the exposure control is performed in synchronization with the charge reset operation of the image sensor 6 and the movement of the rear curtain of the shutter mechanism unit 16. Since the technology of the electronic front curtain is known, a detailed explanation thereof will be omitted.

The image processing unit 7 includes an A / D converter, a white balance adjustment circuit, a gamma correction circuit, an interpolation calculation circuit, and the like. For example, the image processing unit 7 performs color interpolation (demosizing) processing from the signal of the bayer array acquired from the image sensor 6 to generate color image data, and outputs the recording image data to the storage unit 8. Further, the image processing unit 7 compresses data such as still images, moving images, and sounds. The storage unit 8 includes a non-volatile memory and stores various data including image data. The camera control unit 5 performs a process of storing data in the storage unit 8 and a process of outputting the data read from the storage unit 8 to the display unit 9 and presenting the data to the user.

The camera control unit 5 controls image processing, image processing, recording / playback processing, and the like in response to user operation signals. For example, the operation detection unit 10 detects that the shutter release button is pressed. The first switch is turned on by half-pressing the shutter release button, which is referred to as S1 operation below. Further, when the user pushes the button all the way by pressing the shutter release button fully, the second switch is turned on, which is referred to as S2 operation below. When the camera control unit 5 receives a shooting instruction from the operation detection unit 10 by the S2 operation, it performs drive control of the image sensor 6, image processing, compression processing, and the like, and further displays image information and the like on the screen of the display unit 9. Take control. Further, the operation detection unit 10 detects the operation of the touch panel provided on the display device 9a on the back surface of the main body unit, and transmits the operation instruction of the user to the camera control unit 5.

Next, the operation of the imaging optical system 3 will be described. The camera control unit 5 is connected to the image processing unit 7 and calculates an appropriate focus position and aperture value based on the signal from the image sensor 6. That is, the camera control unit 5 measures the photometry and detects the focal state based on the output signal of the image sensor 6, and determines the exposure conditions (F value, shutter speed, etc.). The camera control unit 5 controls the exposure of the image sensor 6 by aperture control and shutter control. The camera control unit 5 transmits a command signal to the lens control unit 12 via the electrical contact 11. The lens control unit 12 controls the lens drive unit 13 according to a command signal from the camera control unit 5. For example, in a mode for correcting camera shake or the like, the lens driving unit 13 moves a correction lens (shift lens or the like) by a command signal from the camera control unit 5 to the lens control unit 12 based on a signal obtained from the image sensor 6. Image blur correction operation is performed.

By controlling the operation of each part of the imaging device 1 according to the user operation, it is possible to shoot still images and moving images. When the user instructs the shooting of a still image or a moving image using the operation member of the imaging device 1, the camera control unit 5 controls the shooting operation according to the operation signal from the operation detection unit 10. The camera control unit 5 calculates a target value based on the detection signal from the blur detection unit 15, and controls the drive of the blur correction unit 14. That is, the camera control unit 5 is responsible for generating the target value based on the detection signal of the blur detection unit 15 and driving control of the blur correction unit 14. At that time, the camera control unit 5 controls the image blur correction operation according to the shooting conditions, the exposure conditions, and the like.

Briefly explaining the flow of drive control of the blur correction unit 14, the user performs an S1 operation, and the operation detection unit 10 detects this to start a shooting preparation operation. Image blur correction is performed by the blur correction unit 14 in order to facilitate the composition determination of the user during the so-called composition-determining aiming operation. That is, the image sensor 6 is driven (moved or rotated) by the control of the blur correction unit 14 based on the detection signal of the blur detection unit 15. After that, the user performs an S2 operation, the operation detection unit 10 detects this, and a shooting operation (image recording operation) is started. At this time, the image sensor 6 is driven by the control of the blur correction unit 14 based on the detection signal of the blur detection unit 15 in order to suppress the image blur of the subject image acquired by the exposure operation. After a certain period of time has passed after the exposure, the image blur correction operation is stopped. Details of switching the energization method in this embodiment will be described later with reference to FIG.

A specific example of the blur correction unit 14 having the image plane vibration isolation mechanism will be described with reference to FIG. The blur correction unit 14 includes an image blur correction mechanism unit and a control circuit unit thereof. FIG. 3 is an exploded perspective view of the image blur correction mechanism unit. The electrical mechanism that controls the image blur correction mechanism is not shown. The vertical direction (Z-axis direction) of FIG. 3 is a direction parallel to the optical axis 4, and the X-axis direction and the Y-axis direction orthogonal to the Z-axis direction are defined. The image blur correction mechanism portion includes a fixed portion and a movable portion. Fixed parts that do not move are numbered in the 100s, and moving parts are numbered in the 200s. The balls 301 (three balls 301a to 301 in this embodiment) sandwiched between the fixed portion and the movable portion are rolling members.

First, the upper yoke 101, the lower yoke 108, and the base plate 110 that form the fixing portion will be described. The upper magnets 103a, 103b, 103c, 103d, 103e, and 103f are adhesively fixed to the upper yoke 101 in a state of being attracted to the upper yoke 101. The upper magnets 103a and 103b, 103c and 103d, 103e and 103f are adjacent to each other, respectively. The upper yoke 101 is fastened and fixed to the base plate 110 by using screws 102a, 102b, 102c.

The lower magnets 107a, 107b, 107c, 107d, 107e, and 107f are adhesively fixed to the lower yoke 108 in a state of being attracted to the lower yoke 108. The lower magnets 107a and 107b, 107c and 107d, 107e and 107f are adjacent to each other, respectively.

The base plate 110 is provided with a plurality of holes so as to avoid the lower magnets 107a to 107a, and the surface of the magnet is configured to protrude from each hole. The base plate 110 and the lower yoke 108 are fastened and fixed by screws 109a, 109b, 109c. Since the lower magnets 107a to 107 have a larger dimension in the thickness direction than the base plate 110, they are in a state of protruding from the hole portion of the base plate 110.

The upper yoke 101 and the upper magnets 103a to 103, and the lower yoke 108 and the lower magnets 107a to 107 form a magnetic circuit, forming a so-called closed magnetic path. The upper magnets 103a to 103a and the lower magnets 107a to 107 are magnetized in the optical axis direction (vertical direction in FIG. 3), and adjacent magnets (for example, the upper magnets 103a and 103b) are magnetized in different directions. ing. Further, the upper magnet and the lower magnet (for example, the upper magnet 103a and the lower magnet 107a) facing each other are magnetized in the same direction. By doing so, a strong magnetic flux density is generated in the optical axis direction between the upper yoke 101 and the lower yoke 108.

Since a strong suction force is generated between the upper yoke 101 and the lower yoke 108, the main spacers 105a, 105b, 105c and the auxiliary spacers 104a, 104b are configured to maintain an appropriate distance on the base plate 110. The appropriate spacing here means that the coils 205a to 205 and the flexible printed circuit board (hereinafter referred to as FPC) 201, which will be described later, are arranged between the upper magnets 103a to 103a and the lower magnets 107a to f, and an appropriate gap is provided. It is an interval that can secure. The main spacers 105a, 105b, 105c are provided with screw holes. The upper yoke 101 is fixed to the main spacers 105a, 105b, 105c by the screws 102a, 102b, 102c. Rubber is installed on the body of each main spacer to form a mechanical end (so-called stopper) for the movable part.

The movable frame 206 and the FPC 201 form a movable portion. The movable frame 206 is arranged between the upper yoke 101 and the base plate 110. The movable frame 206 is formed of magnesium die-cast or aluminum die-cast, and is lightweight and highly rigid. A plurality of recesses are formed in the movable frame 206, and the coils 205a, 205b, and 205c are accommodated, respectively. The movable frame 206 includes a printed circuit board 203. The printed circuit board 203 is electrically connected to an image pickup element 6, coils 205a, 205b, 205c (not shown) and a position detection element described later. The printed circuit board 203 sends and receives signals to and from an external circuit via a connector.

A position detection element such as a Hall element is mounted on the FPC 201, and its mounting positions 202a, 202b, and 202c are shown. The plurality of position detecting elements are mounted at mounting positions 202a, 202b, 202c on the opposite surface that cannot be seen in FIG.

The fixed portion rolling plates 106a, 106b, 106c are adhesively fixed to the base plate 110, and the movable portion rolling plates 204a, 204b, 204c are adhesively fixed to the movable frame 206. These rolling plates face each other and form rolling surfaces of the balls 301a, 301b, and 301c, respectively. That is, since the balls 301a to c are sandwiched between the fixed portion rolling plates 106a to c and the movable portion rolling plates 204a to c, respectively, the movable frame 206 is movably supported with respect to the base plate 110. To. Compared with the method of interposing the balls 301a to c between the base plate 110 and the movable frame 206 without using the fixed portion rolling plate and the moving portion rolling plate, the surface roughness is provided by providing the rolling plate separately. It becomes easy to design the sheath hardness and the like in a preferable state.

By passing a current through the coils 205a to 205 in the image blur correction mechanism portion having the above-described configuration, a force according to Fleming's left-hand rule is generated, and the movable portion can be moved. In the present embodiment, the position of the movable portion is detected by using the magnetic detection element so that the position can be detected by using the magnetic circuit described above. For example, since the Hall element is a small element, it can be arranged so as to be nested inside the windings of the coils 205a to 205c. In addition, feedback control can be performed by using the signal of the Hall element. Based on the signal value of the Hall element, it is possible to control the translational motion of the movable portion and the rotational motion around the optical axis 4 in a plane orthogonal to the optical axis 4.

To briefly explain the control of rotating the image blur correction mechanism about the optical axis, the Hall element signals at the mounting positions 202a and 202c are in opposite phase while the Hall element signals at the mounting positions 202a are kept constant. Drive control is performed so as to be. As a result, a rotational motion about the optical axis 4 can be generated.

It is the magnetic flux density in the optical axis direction that is detected at the mounting positions 202a, 202b, and 202c of the position detection element. The characteristics of a magnetic circuit including upper magnets 103a to 103f and lower magnets 107a to 107f are generally non-linear. Therefore, the magnetic flux densities detected at the mounting positions 202a, 202b, and 202c of the position detection element do not necessarily have a constant resolution in the entire drive range. That is, the detection resolution changes within the drive range. For example, the change in magnetic flux density has a steep position and a gentle position, and the steeper position has a higher detection resolution (the change in magnetic flux density with respect to the amount of movement is larger). In the magnetic circuit shown in FIG. 3, the change in magnetic flux density is the largest and the detection resolution is high at the boundary position of the magnet (for example, the boundary position between the upper magnets 103a and 103b). Since the details of the control method are well known, further description thereof will be omitted.

Leakage flux will be described with reference to FIG. FIG. 4 shows a state in which the image sensor 6 is attached to the blur correction unit 14, and FIG. 4A is a view when viewed from the optical axis direction. FIG. 4B is a cross-sectional view taken along the line AA of FIG. 4A. In FIG. 4, the reference numerals used in FIG. 3 will be used for description. The CMOS sensor 6a, the cover glass 6b, the sensor housing 6c, and the sensor holder 210 provided in the image sensor 6 are shown respectively. FIG. 4B schematically shows the leakage flux with arrows 31 and 32.

As shown in FIG. 4A, the image sensor 6 is fixed to the sensor holder 210 by a method such as adhesion, and then fixed to the movable frame 206. Therefore, when the movable frame 206 moves, the image sensor 6 also moves integrally. The magnetic flux is generated by the current flowing through the coil 205c (Coil 205c is illustrated in FIG. 4, but the same applies to other coils). Most of the magnetic flux is blocked by the upper yoke 101 and the lower yoke 108 made of a soft magnetic material. However, some magnetic flux reaches the CMOS sensor 6a by following the paths indicated by arrows 31 and 32. When the leakage flux that changes at the time of signal reading acts on the CMOS sensor 6a as described later, it causes striped noise.

Energization of the coil 205c is generally performed by a pulse width modulation (PWM) method, and the direction and amount of the current fluctuate in a constant cycle. As a result, a so-called ripple current is generated, and an unnecessary magnetic flux is generated. Noise is generated by this unnecessary magnetic flux.

With reference to FIG. 5, the relationship between the generation of ripple current due to energization in the PWM method and the striped noise generated in the image will be described. FIG. 5A is a diagram showing the relationship between voltage and current during energization. FIG. 5B is a diagram schematically showing the relationship between the ripple current and the striped noise.

The voltage waveform 41 shown on the upper side in FIG. 5A changes into a rectangular wave shape, and the pulse width changes at the timing 42 for switching the DUTY (duty ratio) of the PWM signal. The current waveform 43 shown on the lower side in FIG. 5A is a triangular wave, I1 represents the average current value before the switching timing 42, and I2 represents the average current value after the switching timing 42.

The frame 44 shown in FIG. 5B shows an area of the acquired image. The plurality of horizontal lines 45 in the frame 44 schematically represent the striped noise, and the arrow 46 indicates that the signals are sequentially read out.

In the PWM method, an arbitrary ratio is expressed by digitally controlling the control voltage and switching the DUTY in energization within a fixed cycle (PWM cycle). As an example, FIG. 5A shows a state in which + 50% energization is performed before the switching timing 42, and a state in which + 25% energization is performed after the switching timing 42. The voltage value is + V or 0. On the other hand, when energization is performed in the opposite direction, the voltage value changes so as to take a binary value of −V or 0 as described later, and the ratio changes.

The PWM frequency is set to a frequency sufficiently higher than the frequency corresponding to the mechanical response. For example, it is assumed that the image blur correction for camera shake is controlled up to about 100 Hz. In this case, the PWM frequency is set to 100 kHz or the like. As a result, the fluctuation of the PWM signal does not pose a problem in practical control, and only an average response is output. In the image blur correction mechanism unit described with reference to FIG. 3, high frequency components are sufficiently blocked by the effect of the mass of the movable frame 206. That is, it may be understood that the image blur correction mechanism unit is a mechanical LPF (low-pass filter). Therefore, the fluctuation at the PWM frequency is not observed as the movement of the movable frame 206 (actually acting is the driving force).

On the other hand, as shown by the current waveform 43 in FIG. 5 (A), the average current value changes from I1 to I2. When the resistance of the coil of the actuator is expressed as R, the PWM DUTY is determined as I1 = V × (PWM DUTY) / R. Specifically, in FIG. 5A, before the switching timing 42, DUTY = + 50%, and the current value is I1 = V / (2R). After the switching timing 42, DUTY = + 25%, which is the current value of I2 = V / (4R). An average current such as I1 and I2 is output as a current corresponding to the driving force of the movable frame 206. That is, the driving force acting on the movable frame 206 can be controlled by changing the DUTY.

As shown in FIG. 5A, the current waveform 43 fluctuates according to the PWM frequency and changes as a triangular wave. The current waveform 43 changes depending on the impedance (resistance value and inductance) of the coil. In general, the PWM frequency is sufficiently high that it is higher than the cutoff frequency determined by the impedance of the coil. In that case, a triangular wave as shown in FIG. 5A is obtained as a response. The amplitude of the triangular wave is determined by the impedance of the coil. The current generated by this triangular wave is called a ripple current. The ripple current contains many components of the PWM frequency. Since the ripple current is not a sine wave but a triangular wave, it includes harmonic components and the like, but the PWM frequency component is also large. Further, when a current flows through the coil, a corresponding magnetic flux is generated. Magnetic flux is also generated by the ripple current. As a result, a magnetic flux that changes with the PWM frequency is generated.

The striped noise of FIG. 5B schematically shows how the noise is generated when the information of the image is read out. The signals of the image sensor 6 are sequentially read out as shown by arrows 46. FIG. 5B shows a state of sequentially reading in the row direction. The reading cycle is not completely synchronized with the PWM cycle for controlling the image blur correction mechanism unit. Therefore, in FIG. 5B, the change in magnetic flux generated by the ripple current acting on each read row is shown schematically alternating with N, S, N, S, ....

When the magnetic flux acts on an electric circuit such as an amplifier at the time of signal reading, the reading potential may change. In particular, it is easily affected by the state of the image sensor (state in which the ISO sensitivity is high), which is called high sensitivity. FIG. 5B is schematically shown so that the image is dark when N and bright when S, and the image is read out with a horizontal striped level difference. This is referred to herein as striped noise. Note that FIG. 5B shows an example in which it becomes dark at N and bright at S, but this differs depending on the configuration of the electric circuit and the like. In short, the change in magnetic flux at the PWM frequency caused by the ripple current is observed as striped noise in the image.

With reference to FIG. 6, an example of an electric circuit for performing PWM control and a dead time in ON / OFF control of the switch elements constituting the electric circuit will be described. The circuit shown in FIG. 6 has a configuration generally called an H bridge. In FIG. 6, the motor 47 corresponds to the coil of the image blur correction mechanism unit. Arrows 48 and 49 indicate the direction of current flow. The H-bridge includes four switches SW1, SW2, SW3, and SW4. These switches are semiconductor switch elements such as FETs (Field Effect Transistors). FIG. 6A shows a state in which all the switches of the H bridge are opened to achieve high impedance. FIG. 6B shows a short circuit with respect to the ground. FIG. 6C shows a state in which a current flows in the directions of arrows 48 and 49, that is, in the direction from TER1 to TER2.

Since the motor 47 is arranged at the center of the H bridge shown in FIG. 6, a circuit having a shape like the letter H is formed. One set of switches SW1 and SW2 is controlled by one control signal Ctrl1, and the other set of switches SW3 and SW4 is controlled by one control signal Ctrl2. Each set of switches can only be turned on selectively. That is, SW1 and SW2, or SW3 and SW4 are controlled so as not to be turned ON at the same time. If SW1 and SW2, or SW3 and SW4 are turned on at the same time, the power supply terminal of the power supply voltage V and the GND are short-circuited, a large current flows, and there is a possibility of circuit destruction. Therefore, when the state in which SW1 is ON and SW2 is OFF is changed to the state in which SW1 is OFF and SW2 is ON, it is controlled so that there is always a time during which SW1 and SW2 are in the OFF state for a certain period of time. .. This time is called a dead time, and is a time during which the motor 47 cannot react in terms of control. The issues associated with the dead time will be described later with reference to FIGS. 8 and 9.

When the motor 47 is not energized, the switch is controlled as shown in FIG. 6 (A) or FIG. 6 (B). For example, in FIG. 6B, SW1 and SW3 are OFF, and SW2 and SW4 are ON. TER1 is an output line connecting the connection point between SW1 and SW2 and the motor 47, and TER2 is an output line connecting the connection point between SW3 and SW4 and the motor 47. In the case of FIG. 6B, TER1 and TER2 are in a short-circuited state. When a counter electromotive force is generated from the motor 47 (in the case of a rotary motor, the motor is rotating due to an inertial load or the like), the motor 47 is braked.

On the other hand, when the motor 47 is energized, SW1 is ON and SW4 is ON, for example, as shown in FIG. 6C. As described above, the switches in the set are turned on only alternately, so SW2 and SW3 are turned off. In the case of FIG. 6C, a current flows in the direction from TER1 to TER2 as shown by arrows 48 and 49. When a current flows in the opposite direction, SW2 and SW3 may be turned ON and SW1 and SW4 may be turned OFF.

As can be seen from FIG. 6, the voltage values applied to both ends of the motor 47 are in three states of + V, 0, and −V. By controlling Ctrl1 and Ctrl2, PWM control can be easily performed using the H-bridge circuit.

The relationship between the energization method and the ripple current will be described with reference to FIG. 7. There are a plurality of energization methods in the PWM method as follows.
-A method using two potentials, + V and -V (hereinafter referred to as forward and reverse energization).
-A method that uses three potentials, + V, 0, and -V (hereinafter referred to as on-short energization).

FIG. 7A is a diagram showing the relationship between voltage and current in the case of forward / reverse energization, and FIG. 7B is a diagram showing the relationship between voltage and current in the case of on-short energization. The upper part of each figure shows the time change of the voltage, and the lower part shows the time change of the current. In both FIGS. 7A and 7B, in order from the left, 0%, + 50%, + 100%, and -50% of current flow with respect to full energization (when V voltage is applied in a DC manner). The steady state of voltage and current in the case of is shown for the period of one cycle of PWM. The term "steady state" as used herein means that the state is stable, not a transient response. In addition, although the ripple current is actually small in the current waveform, the vertical axis of the ripple current is enlarged for easy understanding.

FIG. 7A shows voltage waveforms 51a, 51b, 51c, and 51d when DC currents are 0%, + 50%, + 100%, and -50% by forward / reverse energization, respectively. Further, the current waveforms 52a, 52b, 52c, and 52d when the DC-like current becomes 0%, + 50%, + 100%, and -50% by forward / reverse energization are shown, respectively. Arrows 53a, 53b, and 53d indicate the magnitudes of the ripple currents that occur when the DC currents are 0%, + 50%, and -50%, respectively, with forward and reverse energization.

In FIG. 7A, when no current is passed in a DC manner with forward / reverse energization, + V and −V voltages are applied to the motor at a ratio of 50% as shown by the waveform 51a. By doing this, no current flows on average. The current waveform 52a fluctuates around a current value of 0, and a triangular wave (magnitude of ripple current: see arrow 53a) is generated. Since + V and −V voltages are applied to the motor, the amplitude is maximized in terms of ripple current. That is, the amplitude of the ripple current indicated by the arrow 53a is larger than any other state, and the striped noise generated in the image is large.

When the DC current is + 50% in the forward / reverse energization, the voltage value is set to + V in 75% of the PWM cycle, and the voltage value is set to -V in 25% of the PWM cycle. Voltage waveform 51b). In the forward / reverse energization, when the DC current flows in the forward direction (+ direction), the ratio of + V increases, and the waveform changes from 51b to 51c. On the contrary, when it is increased in the negative direction (-direction), the ratio of −V increases, and when it is -50%, the voltage waveform becomes like 51d. The ripple current decreases accordingly, and when it is + 50% and -50%, the amplitudes are the quantities indicated by arrows 53b and 53d, respectively. When energization is performed at + 100%, the voltage is constant at + V, so that the voltage and current during the PWM cycle do not fluctuate and no ripple current is generated. Although energization at -100% is not shown, since the voltage is constant at −V, the voltage and current during the PWM cycle do not fluctuate and no ripple current is generated.

On the other hand, FIG. 7B shows voltage waveforms 54a, 54b, 54c, and 54d when the DC currents are 0%, + 50%, + 100%, and -50% by on-short energization, respectively. Further, the current waveforms 55a, 55b, 55c, and 55d when the DC-like current becomes 0%, + 50%, + 100%, and -50% by on-short energization are shown, respectively. Arrows 56b and 56d indicate the magnitude of the ripple current generated when the DC current is + 50% and -50% with on-short energization, respectively.

In FIG. 7B, when the current is not passed in a DC manner by on-short energization, it is in a so-called short-circuit state as shown by the voltage waveform 54a. That is, the voltage does not change from 0V. As shown in the current waveform 55a, no current flows on average. Since the voltage value is zero and constant, there is no fluctuation in the voltage and current during the PWM cycle, and no ripple current occurs.

In on-short energization, the ratio of + V increases when the current flowing in DC is increased in the + direction. At + 50%, the voltage value becomes + V at 50% of the PWM cycle, and the voltage value becomes zero at 50% of the time. As the current in the + direction is increased, the ratio of + V becomes even larger, and the waveform changes from 54b to 54c. On the contrary, when it is increased in the − direction, the ratio of −V increases, and at -50%, the waveform becomes 54d. The maximum ripple current is 50% in the on-short energization state, and the amplitudes at + 50% and -50% are the amounts indicated by arrows 56b and 56d, respectively. When energized at + 100%, the voltage value is constant at + V, so there is no fluctuation in the voltage and current during the PWM cycle, and no ripple current occurs. Although energization at -100% is not shown, since the voltage value is constant at −V, there is no fluctuation in the voltage and current during the PWM cycle, and no ripple current is generated.

As can be seen from the numerical calculation, the ripple current of forward / reverse energization is always larger than the ripple current of on-short energization regardless of the amount of DC (direct current) current. For example, in the case of + 50%, the amplitude shown by the arrow 53b in FIG. 7 (A) is larger than the amplitude shown by the arrow 56b in FIG. 7 (B). Further, the difference becomes larger as the amount of DC-like current decreases. For example, in the case of 0%, the amplitude of the ripple current is zero in FIG. 7 (B) with respect to the amount indicated by the arrow 53a in FIG. 7 (A), and the difference is very large. On the other hand, with respect to the image blur correction mechanism unit described with reference to FIG. 3, it is required to secure power for image blur correction, reduce power when holding its own weight, and the like. Therefore, the power for holding its own weight (which is the longest state of the image blur correction mechanism in terms of time) is kept small. That is, it is designed so that the DC current can be small. Therefore, the noise is large in the forward and reverse energization, and the noise is suppressed in the on-short energization.

Next, with reference to FIGS. 8 and 9, waveform distortion will be described for forward / reverse energization and on-short energization. FIG. 8 shows the case of forward / reverse energization, and FIG. 9 shows the case of on-short energization. FIG. 8A shows a command voltage when the DC current amount is zero, and shows a voltage waveform 71 in one PWM cycle. FIG. 8B shows the voltage across the actuator (coil) when the command voltage of FIG. 8A is received, and shows the voltage waveform 72 in one PWM cycle. FIG. 8C shows a command voltage when the DC-like current amount is slightly positive, and shows a voltage waveform 73 in one PWM cycle. FIG. 8D shows the voltage across the actuator when the command voltage of FIG. 8C is received, and shows the voltage waveform 74 in one PWM cycle.

In FIGS. 8A to 8D, the horizontal axis is the time axis and the vertical axis is the voltage axis. Each timing 61 to 67 shown on the time axis is as follows.
The timing 61 is the start timing of the PWM cycle. In FIG. 8, the PWM start timings are aligned by (A), (B), (C), and (D).
The timing 62 is a timing that is delayed from the timing 61 due to the dead time.
The timing 63 is a timing corresponding to the midpoint of the PWM cycle.
The timing 64 is a timing that is delayed from the timing 63 due to the dead time.
-Timing 65 is the timing of voltage switching after lengthening the + V time in order to pass a DC-like current.
The timing 66 is a timing that is delayed from the timing 65 due to the dead time.
-Timing 67 is the timing of the end of the PWM cycle.
8 (A) to 8 (D) show the waveform of one cycle of PWM, but this waveform is actually repeated. In FIG. 8E, the horizontal axis represents the target amount of DC-like drive current, and the vertical axis represents the response amount obtained by the energization method, and the relationship between the two is shown.

The voltage waveform 71 of FIG. 8A shows a command voltage when the DC current amount is zero in the forward / reverse energization. In this case, similarly to the voltage waveform 51a shown in FIG. 7A, the command is given with the voltage value set to + V for 50% of the time within the PWM cycle and the voltage value set to −V for the remaining 50% of the time. .. Therefore, + V is instructed between the timing 61 and the timing 63, and −V is instructed between the timing 63 and the timing 67.

The voltage across the actuator at the command voltage shown as the voltage waveform 71 is as shown in FIG. 8 (B). In this case, as described with reference to FIG. 6, in a general circuit that performs PWM drive control, an OFF time of the switch element, that is, a dead time is provided in order to prevent a short circuit state. The voltage waveform 72 of FIG. 8B schematically shows the voltage across the actuator when the dead time is taken into consideration. That is, + V is instructed at the timing 61, but the voltage across the coil is + V at the timing 62 because the rise of the signal is delayed due to the dead time. Similarly, when the change of the voltage from + V to −V is instructed at the timing 63, the voltage across the actuator is delayed due to the dead time, so that the voltage becomes −V at the timing 64. As a result, the response shown in waveform 72 is obtained.

Next, assume a case where the DC-like drive current amount is slightly changed to the positive side. In order to make the DC-like current a positive value by forward / reverse energization, the + V time may be lengthened. As shown in FIG. 8C, + V is instructed between the timing 61 and the timing 65, and −V is instructed between the timing 65 and the timing 67. That is, the + V time is longer in the voltage waveform 73 than in the voltage waveform 71 in FIG. 8 (A). The voltage across the actuator shown in FIG. 8D is as shown in the voltage waveform 74. In this case, since there is a dead time, it becomes + V at the timing 62, and it becomes OFF (0V) between the timing 65 and the timing 66 to prevent a short circuit. It is −V between timing 66 and timing 67. At this time, the relationship between the target amount of DC-like current and the response amount obtained as the voltage across the actuator is shown by graph line 75 in FIG. 8 (E). In the forward / reverse energization, an OFF (0V) section is generated by switching the voltage, but this reduces the time of both + V and −V, so the distortion is small. The distortion here means that there is a difference between the target amount and the response amount. The graph line 75 in FIG. 8 (E) is a substantially straight line passing through the origin, resulting in a small distortion. That is, the linearity is relatively high with respect to the response of the voltage across the actuator to the target amount of the drive current of the actuator.

Next, the case of on-short energization will be described with reference to FIG. 9 (A) to 9 (E) are views corresponding to FIGS. 8 (A) to 8 (E), although the energization method is different. The explanation of axis setting etc. is omitted. 9 (A), (B), (C), and (D) show voltage waveforms 91, 92, 93, and 94 in one PWM cycle, respectively. Each timing 81 to 85 shown on the time axis is as follows.
The timing 81 is the start timing of the PWM cycle. In FIG. 9, the PWM start timings are aligned with (A), (B), (C), and (D).
The timing 82 is a timing that is delayed from the timing 81 due to the dead time.
-Timing 83 is the timing of voltage switching after lengthening the + V time in order to pass a DC-like current.
The timing 84 is a timing that is delayed from the timing 83 due to the dead time.
-Timing 85 is the end timing of the PWM cycle.

FIG. 9A shows the command voltage when the DC current amount is zero in the on-short energization. The voltage waveform 91 is the same as the voltage waveform 54a shown in FIG. 7B, and zero is always indicated. FIG. 9B shows the voltage across the actuator at this time, and is shown as a voltage waveform 92 that is always zero.

Next, assume a case where the DC-like drive current amount is slightly changed to the positive side. In order to make the DC-like current a positive value by on-short energization, a certain amount of + V time may be set. As shown in FIG. 9C, + V is instructed between the timing 81 and the timing 83, and zero is instructed between the timing 83 and the timing 85. That is, as shown in the voltage waveform 93, a certain amount of + V time is given. The voltage across the actuator shown in FIG. 9D becomes + V at the timing 82 due to the dead time. On the other hand, the timing at which the voltage across the actuator shifts to zero is timing 83. From the timing 84, 0V is positively instructed to the actuator (regardless of the meaning of preventing a short circuit in the dead time).

In on-short energization, a combination of + V and 0 or −V and 0 is used, and one is 0. Therefore, the time of + V (or −V) and the time of 0V change non-linearly. For example, if the time of + V is extremely short and a time shorter than the dead time is specified, it does not become + V and remains 0. FIG. 9 (E) shows the relationship between the target amount of DC-like drive current and the response amount obtained as the voltage across the actuator in the on-short energization. Since the graph line 95 is a polygonal line and has a dead band 96 near the origin, the distortion is larger than that in FIG. 8 (E). That is, the linearity is relatively low with respect to the response of the voltage across the actuator to the target amount of the drive current of the actuator.

As described above, since there is a difference in waveform distortion between the forward / reverse energization described in FIG. 8 and the on-short energization described in FIG. 9, there is a difference in controllability. That is, from the viewpoint of controllability, forward / reverse energization with less distortion is superior.

As can be understood from the description using FIGS. 7 to 9, there are differences in distortion and ripple current depending on the energization method. Focusing on two energization methods, forward / reverse energization and on-short energization, it has the following features.
-Forward / reverse energization: The distortion is relatively small and the ripple current is relatively large.
-On-short energization: The distortion is relatively large and the ripple current is relatively small.
However, the energization method described here is an example, and is not limited to these energization methods if there is a relative difference.

The determination process of the energization method will be described with reference to FIG. In S400, PWM control is started by the generation of a drive command from a stationary state. In S401, the camera control unit 5 determines whether or not the generated drive command is a stationary command. If it is determined that the command is stationary, the process proceeds to S411, and if it is determined that the command is not stationary, the process proceeds to S402.

In S402, the camera control unit 5 determines whether or not the drive command is a minute drive command. The minute drive command is a drive command for a drive amount within a range in which the target drive amount corresponding to the command value corresponds to the dead zone 96 near the origin shown in FIG. 9 (E). If it is determined that the command is a minute drive, the process proceeds to S403, and if it is determined that the command is not a minute drive command, the process proceeds to S404.

In S403, the camera control unit 5 selects a forward / reverse energization method having good controllability and performs PWM control for minute drive. Further, in S404, the camera control unit 5 selects an on-short energization method excellent in noise suppression and performs PWM control for normal driving. Unlike static drive and minute drive, normal drive is a drive that targets a large drive amount that is not a dead zone near the origin. That is, the magnitude (absolute value) of the target current value corresponding to the command value is outside the dead zone. Further, in PWM control, the duty ratio, frequency and drive voltage of the drive signal are controlled based on the target drive amount by using each energization method.

Proceeding to S405 after S403 and S404, the camera control unit 5 detects the driving state of the actuator. In the detection of the driving state, for example, position detection by a hall sensor, current detection of a coil by a sense amplifier or a shunt resistor, or the like is performed. After the state is detected, the process proceeds to S406.

In S406, the camera control unit 5 determines whether or not the drive state has reached the target state. For example, in the case of position detection, whether or not to reach the target position is determined. When it is determined that the target state has been reached, the camera control unit 5 determines that the actuator may be stationary, and proceeds to the process of S407. On the other hand, if it is not determined that the target state has been reached, the camera control unit 5 determines to continue the drive control and proceeds to the process of S408.

In S407, the camera control unit 5 changes the drive command from a minute drive or normal drive command to a static drive command. That is, the stationary command is determined as the drive command. Further, in S408, the camera control unit 5 determines the difference to the target with respect to the detection result. When the camera control unit 5 determines that the difference to the target is within the range of the dead zone 96 near the origin, the process proceeds to S409, but when it is determined that the difference is not within the dead zone 96 near the origin, the camera control unit 5 proceeds. Proceed to process to S410.

In S409 and S410, the drive command is determined. In S409, the camera control unit 5 determines a minute drive command as a drive command. Further, in S410, the camera control unit 5 determines a command for normal drive. Each drive command is determined in S407, S409, and S410, and then returns to S401. After that, based on the drive command newly determined in S407, S409, and S410, the above-mentioned process is repeatedly executed until it is determined in S401 that the command is a static drive command.

When proceeding from S401 to S411, that is, when the command is for static drive, the camera control unit 5 selects the on-short energization method in S411. That is, in the case of static drive, PWM control for static drive is performed by the on-short energization method which is relatively excellent in noise suppression. In the next S412, the camera control unit 5 ends the drive control because the actuator is in the stationary state.

According to the present embodiment, by switching the energization method to the coil according to the control command value, it is possible to operate the actuator suitable for noise suppression and controllability. Although an example of position detection has been described as a method for detecting a driving state, the method is not limited to this. For example, in the case of coil current detection by a sense amplifier or shunt resistor, the actuator drive control can be performed by selecting the energization method according to the drive current value obtained from the detection result. Specifically, when the detection result does not reach the target drive current value, forward / reverse energization with excellent controllability is selected, and control is performed to bring the drive current value to the target current value. When the detected drive current value has reached the target current value, on-short energization is selected in order to suppress the amplitude of the drive current value. In this method, by switching the energization method to the coil according to the current detection result, it is possible to operate the actuator suitable for noise suppression and controllability.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the present embodiment, the determination process for switching the energization method is different from that in the first embodiment. Since other configurations are the same as those of the first embodiment, duplicate description will be omitted, and differences from the first embodiment will be described.

FIG. 10 is a flowchart illustrating a determination process for switching the energization method in the present embodiment. FIG. 11 shows a state in which the image blur correction mechanism portion of FIG. 4A is rotated in the direction around the optical axis. The drive directions of all the actuators mounted on the image blur correction mechanism are oblique to the ground.

A process of selecting an energization method during PWM control will be described with reference to FIG. Drive control is started in S1400, and posture detection of the image pickup apparatus 1 is performed in S1401. The posture detection of the image pickup apparatus 1 is performed by using the blur detection unit 15.

In S1402, the camera control unit 5 determines whether or not the drive direction of the actuator is horizontal with respect to the ground based on the posture detection information of the image pickup device 1 detected in S1401. In the state shown in FIG. 4A, the driving direction of the coil 205a is perpendicular to the ground, so the process proceeds to S1404. In the state shown in FIG. 11, the driving direction of the coil 205a is Since it is diagonal to the ground, the process proceeds to S1404. If the image pickup device 1 is rotated 90 degrees about the optical axis with respect to the state shown in FIG. 4A, the driving direction of the coil 205a is horizontal with respect to the ground. In this case, the process proceeds to S1403.

In S1403, the camera control unit 5 selects on-short energization as the energization method related to the PWM drive signal of the coil 205a. The reason is that when the drive direction is horizontal, it is not necessary to deal with the anti-gravity component, so that noise can be suppressed to a small level.

On the other hand, in S1404, the camera control unit 5 detects the position of the coil 205a. The method of position detection is as described above with reference to FIG. The reason for performing the position detection here is that the actuator whose drive direction is not horizontal with respect to the ground needs to be driven to a desired position in order to cope with the anti-gravity component. Next, the process proceeds to S1405.

In S1405, the camera control unit 5 determines whether or not the coil 205a can be driven to the target position. If it is determined that the drive to the target position has been performed, the process proceeds to S1406. If it is determined that the position of the actuator (corresponding to the position of the image sensor) has not reached the target position, the process proceeds to S1407.

In S1406, the camera control unit 5 selects on-short energization as the energization method. The reason is that it is not necessary to change the energizing current significantly when the vehicle can be driven to the target position, so it is sufficient to select a method that can suppress noise to a small extent.

In S1407, the camera control unit 5 selects forward / reverse energization as the energization method. In this case, since the position of the actuator has not reached the target position, it is necessary to drive the actuator, and forward / reverse energization with good controllability is selected.

After S1403, S1406, and S1407, the process proceeds to S1408. In S1408, the camera control unit 5 determines whether or not the energization method has been selected for all the actuators. For example, when the selection of the energization direction is completed only for the coil 205a, the process returns to S1402, and the energization method is sequentially selected for the coil 205b and the coil 205c. When the energization method has been selected for all the actuators (coils), the process proceeds to S1409.

In S1409, the camera control unit 5 performs PWM control. The PWM control signal is output to the coil 205a, the coil 205b, and the coil 205c by the selected energization method. In the next S1410, the camera control unit 5 determines whether or not to end the control shown in S1401 to S1409. This determination does not need to be determined in particular depending on the state of each member, and may be determined, for example, by whether or not the user has performed an imaging end operation of the imaging device 1. When continuing the control, the camera control unit 5 returns to the process of S1401. Further, when the control is terminated, the camera control unit 5 proceeds to S1411, and ends the selection of the energization method and the PWM control.

According to the present embodiment, by switching the energization method according to the posture of the image pickup apparatus and the drive control state of the actuator, it is possible to perform control in which a plurality of actuators are linked, which is suitable for noise suppression and controllability.
Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the gist thereof.

5 Camera system control unit 6 Image sensor 14 Blur correction unit 15 Blur detection unit

Claims (11)

A control device that controls the actuator by pulse width modulation control.
Control to output a control signal by switching between the first energization method with relatively small distortion and relatively large ripple current and the second energization method with relatively large distortion and relatively small ripple current. Means and
It has a driving means for driving the actuator according to the control signal.
The control means is characterized in that the first energization method is selected at the first command value, and the second energization method is selected at a second command value larger than the first command value. apparatus. The control device according to claim 1, wherein the control means selects the second energization method at a third command value of zero. The control device according to claim 1 or 2, wherein the target current value of the actuator corresponding to the first command value is within a dead zone larger than zero. It has a detecting means for detecting the state of the actuator, and has
The control device according to any one of claims 1 to 3, wherein the control means switches the energization method according to the state of the actuator detected by the detection means. When the detection means detects that the position of the actuator has reached the target position, the control means selects the second energization method, and the detection means sets the position of the actuator to the target position. The control device according to claim 4, wherein the first energization method is selected when it is detected that the condition has not been reached. The fourth aspect of claim 4, wherein the control means switches to the second energization method when the first energization method is selected and the position of the actuator has reached the target position. Control device. When the detection means detects whether the drive current value of the actuator has reached the target current value, the control means selects the second energization method, and the detection means selects the drive current of the actuator. The control device according to claim 4, wherein when the value does not reach the target current value, the first energization method is selected. A posture detecting means for detecting the posture of the device including the control device is provided.
The control means is characterized in that when the posture detecting means detects that the driving direction of the actuator is horizontal with respect to the ground, the second energization method is selected for the actuator. The control device according to any one of claims 1 to 7. Any of claims 1 to 8, wherein in the first energization method having relatively small distortion, the linearity is relatively high with respect to the response of the voltage across the actuator to the target amount of the drive current of the actuator. The control device according to item 1. The control device according to any one of claims 1 to 9,
It is equipped with a correction means for correcting image blur by moving the image sensor.
The control device is an image pickup device characterized in that the position of the image pickup element is controlled by controlling an actuator included in the correction means. It is a control method executed by a control device that controls an actuator by pulse width modulation control.
The control means switches between the first energization method with relatively small distortion and relatively large ripple current and the second energization method with relatively large distortion and relatively small ripple current to switch the control signal. The output control process and
The driving means has a step of driving the actuator according to the control signal.
In the control step, the control means selects the first energization method at the first command value and selects the second energization method at the second command value larger than the first command value. A control method characterized by.

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