WO2011108209A1

WO2011108209A1 - Position control device, position control method, driving device and imaging device

Info

Publication number: WO2011108209A1
Application number: PCT/JP2011/000910
Authority: WO
Inventors: 泰啓本多
Original assignee: コニカミノルタオプト株式会社
Priority date: 2010-03-05
Filing date: 2011-02-18
Publication date: 2011-09-09
Also published as: JPWO2011108209A1

Abstract

Disclosed are a position control device, a position control method, a driving device and an imaging device in which the position of a movable part displaced by use of a shape memory alloy is controlled. The standard operation for controlling the position of said movable part involves detecting as the initial resistance value the resistance value of the aforementioned shape memory alloy (S1), and setting the target resistance value corresponding to the target displacement position of the aforementioned movable part to a value less than the aforementioned initial resistance value (S2). Consequently, the position control device, position control method, driving device and imaging device are capable of controlling the position of a movable part on the basis of the resistance value of a shape memory alloy by a simple configuration.

Description

POSITION CONTROL DEVICE, POSITION CONTROL METHOD, DRIVE DEVICE, AND IMAGING DEVICE

The present invention relates to a position control apparatus and a position control method for controlling the position of a movable part that is preferably used for, for example, a shape memory alloy actuator that moves a movable part using a shape memory alloy in a bias application method. Then, the present invention relates to a drive device and an imaging device that include this position control device.

In recent years, image quality has been improved, such as a dramatic increase in the number of pixels in an image sensor mounted on a mobile phone with a camera. In accordance with this, there is a demand for higher performance of the lens unit constituting the imaging optical system. More specifically, the autofocus type that is a fixed focus type is required to have high performance, and the zoom function is also required to be an optical zoom instead of or in addition to the digital zoom. Here, an actuator for moving the lens in the direction of the optical axis is required for both autofocus and optical zoom.

Therefore, as such an actuator, shape memory alloy (Shape Memory Alloy)
A material using Alloy (hereinafter sometimes referred to as “SMA”) is known. This shape memory alloy has a crystal structure called an austenite phase (high temperature phase) on the higher temperature side than the transformation temperature, and a crystal structure called martensite phase (low temperature phase) on the lower temperature side. A general metal material does not return to the shape before deformation when a predetermined external force is applied. However, SMA does not return to its martensite phase when it is deformed by applying a predetermined external force in a martensitic phase state. It transforms from the site phase to the austenite phase, and its shape recovers to its original shape before deformation.

More specifically, in the bias application method, as the temperature increases, the resistance value of the SMA also increases, and the resistance value reaches the maximum resistance value Rmax at a predetermined temperature TRmax. The resistance value becomes the minimum resistance value Rmin at a predetermined temperature TRmin, and thereafter, the resistance value starts to increase again and the resistance value increases (TRmax <TRmin, Rmax> Rmin). In particular, in the range from the maximum resistance value Rmax to the minimum resistance value Rmin, the resistance value of the SMA is substantially proportional to the temperature.

An actuator (shape memory alloy actuator) using SMA drives a driven body by utilizing this characteristic. A bias applying type actuator using SMA generates a contraction force by energizing and heating the SMA and uses the contraction force as a driving force for the lens, and is generally easy to reduce in size and weight. In addition, there is an advantage that a relatively large ability can be obtained. For example, since the electrical resistance value of the SMA wire processed into a linear shape is approximately proportional to the length of the SMA wire in the temperature range from the predetermined temperature TRmin to the predetermined temperature TRmax, the SMA wire is controlled by controlling the resistance value. It is possible to control the position of a driven body such as a lens without changing the length of the lens and the need for a position sensor or the like.

However, as described above, in the region from the predetermined temperature TRmax to the predetermined temperature TRmin where the crystal phase of SMA transforms, and other regions (a temperature region higher than the predetermined temperature TRmin or a temperature region lower than the predetermined temperature TRmax). Since the change direction of the SMA resistance value with respect to temperature is different, position control cannot be performed with a simple algorithm. In view of such circumstances, for example, techniques described in Patent Document 1 and Patent Document 2 have been proposed.

The position control device disclosed in Patent Document 1 includes an actuator that operates based on a displacement of a shape memory alloy body, a drive unit that heats and cools the shape memory alloy body, and a deviation between the displacement of the actuator and a target value of the displacement. A means for operating the driving means based on the above, a resistance detecting means for detecting the resistance value R of the shape memory alloy body, and a maximum resistance value Rmax and a minimum resistance value Rmin of the shape memory alloy body before starting position control. Storage means for obtaining and storing, and displacement calculation means for calculating the displacement of the actuator based on the output of the resistance detection means and information stored in the storage means. With this configuration, the resistance value of the shape memory alloy can be controlled to take a value between the maximum resistance value Rmax and the minimum resistance value Rmin.

Patent Document 2 discloses a technique for controlling the SMA actuator by detecting the maximum resistance value Rmax of the SMA and decreasing the resistance value of the SMA from the maximum resistance value Rmax to the target resistance value. .

However, in the shape memory alloy actuator control device described in Patent Literature 1 and Patent Literature 2, the control system includes a detection circuit for detecting the maximum resistance value Rmax and the minimum resistance value Rmin, a determination algorithm, a false detection avoidance circuit, and the like. There is a possibility that the configuration of the above becomes complicated.

Japanese Patent No. 2769351 International Publication No. 2008/099156 Pamphlet

The present invention has been made in view of the above circumstances, and an object thereof is to provide a position control device and a position control method capable of position control based on the resistance value of SMA with a simpler configuration. is there. Another object of the present invention is to provide a driving device and an imaging device including these position control device and this shape memory alloy actuator.

In the position control device, the position control method, the drive device, and the imaging device according to the present invention, the position of the movable part to be moved is controlled by using the shape memory alloy. As a preparatory operation for controlling the position of the movable part, the resistance value of the shape memory alloy is detected as an initial resistance value, and the target resistance value corresponding to the target displacement position of the movable part is set to a value smaller than the initial resistance value. Is done. Therefore, such a position control device, a position control method, a driving device, and an imaging device can control the position of the movable portion based on the resistance value of the shape memory alloy with a simpler configuration.

The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

It is a front view of the autofocus lens drive mechanism in the imaging device according to the embodiment. It is a side view for demonstrating the operation | movement of FIG. It is a block diagram which shows the electric constitution of the drive device concerning embodiment. It is a graph which shows the temperature-resistance value characteristic of SMA. It is a graph which shows the temperature-resistance value characteristic of SMA in the SMA actuator concerning embodiment. It is a graph which shows the displacement-resistance value characteristic of SMA in the SMA actuator concerning embodiment. It is a graph for demonstrating control by the conventional position control apparatus. It is a graph for demonstrating control by the position control apparatus concerning embodiment. It is a graph for demonstrating the initial control by the position control apparatus concerning embodiment. It is a graph for demonstrating the reference position control by the position control apparatus concerning embodiment. It is a graph for demonstrating the initial control and the reference | standard position control by the position control apparatus concerning embodiment. It is a flowchart for demonstrating the initial control and reference | standard position control by the position control apparatus concerning embodiment. It is a graph which shows the ambient temperature-resistance value characteristic of SMA. It is a graph for demonstrating the initial control by the position control apparatus concerning embodiment in high temperature environment. It is a graph for demonstrating the reference position control by the position control apparatus concerning embodiment in high temperature environment. It is a graph for demonstrating the initial control and the reference | standard position control by the position control apparatus concerning embodiment in high temperature environment.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted suitably. Further, in this specification, when referring generically, it is indicated by a reference symbol without a suffix, and when referring to an individual configuration, it is indicated by a reference symbol with a suffix.

FIG. 1 is a front view (viewed from the lens opening surface) of the autofocus lens driving mechanism 1 in the imaging apparatus according to the embodiment. FIG. 2 is a side view for explaining the operation. FIG. 2A shows a case where the SMA is expanded, and FIG. 2B shows a case where the SMA is contracted.

1 and 2, the imaging apparatus according to the present embodiment includes a shape memory alloy actuator 11 that moves a movable part using a shape memory alloy, a lens 2 that moves according to the movement of the movable part, and a movable part. A position control device 31 (see FIG. 3) that controls the position, and an image sensor 25 (imaging device) that connects to the position control device 31 and captures an optical image of a subject formed by an imaging optical system including a lens (see FIG. 3). 3).

The drive mechanism 1 for the autofocus lens in the imaging apparatus according to the embodiment performs focusing by displacing the lens 2 in the axis AX direction (front-rear direction). The lens 2 is attached to the lens driving frame 3 and constitutes a lens barrel 4. On the outer peripheral surface of the lens barrel 4, a pair of projecting portions 5 projecting in the radial direction is formed at the front end, and the projecting portions 5 are hooked on the arm portion 12 of the shape memory alloy actuator 11, and the lens barrel 4 ( The lens 2) is displaced in the axis AX direction (front-rear direction).

The lens barrel 4 is mounted on the base portion 6, and the front and rear ends of the lens driving frame 3 are integrated with the base portion 6 by a pair of link members 7 via a lateral surface outer wall (not shown). It is supported by the upper base 8 and can be displaced in a parallel state in the direction of the axis AX. A bias spring 10 is interposed between the front end of the lens driving frame 3 and the front cover 9.

The shape memory alloy (SMA) actuator 11 includes an arm portion 12, a lever 13, and a support leg 14, and an SMA 15 made of a shape memory alloy (SMA) wire. In this embodiment, the arm part 12, the lever 13, and the support leg 14 correspond to an example of a movable part. The arm portion 12 is formed in a substantially “<” shape (substantially “C” shape, substantially “V” shape) when viewed from the front (lens opening) side, and the protruding portions 5 are hooked at both ends thereof. The central portion is fixed to one end of the lever 13. A central portion of the lever 13 is supported by a fulcrum 14a of the support leg 14 so as to be swingable and displaceable. A notch 13a is formed at the other end, and an SMA 15 is wound around the notch 13a. Since the SMA 15 is wound around the notch 13a in this way, the displacement of the SMA 15 is prevented even when the lens barrel 4 is displaced in the axis AX direction. Both ends of the SMA 15 are stretched by a pair of electrodes 16 erected on the base portion 6. The SMA 15 is installed in a state in which it is subjected to a tensile deformation rather than the memory shape by an appropriate bias force due to the biasing force of the bias spring 10.

Therefore, while the SMA 15 is not energized between the electrodes 16, the SMA 15 expands by naturally radiating heat to the surroundings, becomes a martensite phase (low temperature phase), the tension of the SMA 15 decreases, and the elastic force of the bias spring 10 Thus, as shown in FIG. 2A, the lens 2 provided in the lens barrel 4 is in the home position (infinite end) pressed against the base portion 6 and can cope with an impact or the like. On the other hand, energization is performed between the electrodes 16 in pulses, and as the duty increases (the energization amount increases), the SMA 15 contracts by generating Joule heat, and tension is generated in the SMA 15. As shown in FIG. 2B, the lever 13 swings in the direction of the arrow 18 against the elastic force of the bias spring 10 and is provided in the lens barrel 4 via the arm portion 12 and the protruding portion 5. The lens 2 thus pushed is pushed in the direction of the front cover 9 of the arrow 19, and in the state where the duty is highest, the SMA 15 becomes an austenite phase (high temperature phase), and the sweep end which is the maximum extension position of the lens 2 Reach (macro edge). When the temperature is increased, the SMA 15 is deformed in the shrinking direction and its resistance value is decreased due to the crystal phase transformation of the SMA 15. The lens barrel 4 starts to move from the infinite end when the stress of the SMA 15 due to contraction increases and exceeds the stress of the bias spring.

Further, in the lever 13 and the arm portion 12 that are L-shaped in a side view (FIG. 2), the vicinity of the bending point is supported by the fulcrum 14a, and the distance from the arm portion 12 to the point where the protruding portion 5 is engaged is 13 is formed to be longer than the distance to the point where the SMA 15 is engaged, so that the displacement of the SMA 15 can be enlarged and the lens barrel 4 can be displaced.

FIG. 3 is a block diagram illustrating an electrical configuration of the position control device according to the embodiment. In FIG. 3, the position control device 31 includes a drive circuit 27 that energizes the SMA 15, a resistance value detection unit 32 that detects the resistance value of the SMA 15, and a target of the movable unit (the arm unit 12, the lever 13, and the support leg 14). A control unit 21 that sets a target resistance value corresponding to the displacement position and controls the amount of current (e.g., current value) applied to the shape memory alloy by the drive circuit 27 so that the resistance value matches the target resistance value; Prepare. The position control device 31 uses the resistance value of the SMA 15 as a parameter related to the expansion and contraction of the SMA 15, that is, a parameter for detecting the position of the lens barrel 4.

The control unit 21 controls the energization current value for the SMA 15 by causing the resistance value detection unit 32 to detect the resistance value of the SMA 15 as an initial resistance value and setting the target resistance value to a value smaller than the initial resistance value at startup. Then, the first control (initial control) for starting the transformation of the SMA 15 from the low temperature phase to the high temperature phase is performed. At the time of starting, a mode in which a photographing mode is selected at the time of start-up of an electronic device provided with the position control device 31 or at an electronic device provided with an imaging device that drives the lens 2 by the position control device 31 For example, at the time of activation, or at the time of activation of the lens immediately before driving the lens in the zoom operation or autofocus operation in the photographing mode. Therefore, at the time of start-up, this is an example of performing a preparatory operation for controlling the position of the movable part, and the first control energizes the SMA 15 of the position control device 31 to move the movable part to the actual target position. This is a control as a preparatory operation before the operation.

After the initial control, the control unit 21 sets a value obtained by adding the optimum differential resistance value stored in advance to the initial resistance value as a target resistance value, controls the energization current value for the SMA 15, and sets the reference for starting the movable unit. The second control (reference position control) for moving to the position (infinite end) is performed.

More specifically, the controller 21 is set by the controller 34 that sets the target resistance value, and the resistance value (detected resistance value) between the electrodes 16 of the SMA 15 detected by the resistance value detector 32. A comparison unit 33 that compares the target resistance value and sets a drive current value corresponding to the comparison result, and a drive control calculation unit 26 that outputs the drive current value set by the comparison unit 33 to the drive circuit 27 as a drive signal. With.

The detection result of the image sensor 25 is also input to the controller 34. The controller 34 determines the focus point when the contrast is high and an edge is detected from the output of the image sensor 25. Therefore, the controller 34 is also a detection unit that detects that the lens barrel 4 has reached the target displacement position.

The resistance value between the electrodes 16 of the SMA 15 is detected by the resistance value detection unit 32, and the detection result and the target resistance value given from the controller 34 are compared by the comparison unit 33, and the drive current value corresponding to the comparison result Is set, and the drive current value is output to the drive control calculation unit 26.

More specifically, the comparison unit 33 increases the drive current value (increases the temperature) when determining that the detected resistance value> the target resistance value, and determines that the detected resistance value <the target resistance value. When the drive current value is decreased (temperature is decreased) and it is determined that the detected resistance value = the target resistance value, the drive current value is not changed (the temperature is maintained). In the present embodiment, the control unit 21 controls the resistance value of the SMA 15 to match the target resistance value by using such a simple algorithm by using the range of the linear characteristic of the SMA 15.

Furthermore, the controller 34 incorporates a storage unit. This storage unit is a constant used in initial control and reference position control, and as shown in FIG. 6, the resistance value of the SMA 15 is approximately proportional to the lens displacement in the range of the lens displacement from the infinite end to the macro end. The relational expression to be stored is stored in advance.

The drive control calculation unit 26 creates a drive signal having a duty corresponding to the drive current value, and controls the energization current value to the SMA 15 via the drive circuit 27 that energizes the SMA 15. The drive circuit 27 includes a switching element such as a transistor, for example. When a drive signal is input to the control terminal from the drive control calculation unit 26, the switching is operated, and the drive current flowing from the drive circuit 27 to the SMA 15 is The duty is changed according to the target position. Therefore, the resistance value detection unit 32 can obtain the resistance value from the known constant current value during the ON duty period and the voltage between the electrodes 16 of the SMA 15. Alternatively, during the OFF duty period in which the drive circuit 27 is OFF and no drive current flows, the resistance value detection unit 32 itself causes a known search current to flow, and the resistance value is calculated from the voltage between the electrodes 16 of the SMA 15. Can be sought.

In summary, the servo control of the position control device 31 is as follows.

<Servo control>
When detection resistance value> target value, increase in energization amount to SMA 15 (temperature rise)
When detection resistance value <target value, decrease in energization amount to SMA 15 (temperature decrease)
When the detected resistance value is equal to the target value, the energization amount does not change to the SMA 15 (temperature maintenance)

Hereinafter, the operation of the position control device 31 will be described with reference to FIGS. 4 to 16.

When the position control device 31 is activated (for example, at the start of energization after power-on or the like), the resistance value detection unit 32 detects the initial resistance value Rstart, and the controller 34 stores the first value stored in advance from the initial resistance value Rstart. A value obtained by subtracting the predetermined value is set as a target resistance value in initial control (hereinafter referred to as a first target value Rtgt1), and the position control device 31 starts the first control (hereinafter referred to as initial control).

According to such a configuration, as the preparatory operation for controlling the position of the movable part, the target resistance value Rtgt1 is set to a value smaller than the initial resistance value Rstart, and the SMA 15 starts to transform from the low temperature phase to the high temperature phase. The device 31 can control the position of the SMA 15 by utilizing the property that the resistance value of the SMA 15 changes linearly with respect to the displacement without detecting the maximum resistance value Rmax of the SMA 15.

FIG. 4 is a graph showing the temperature-resistance value characteristics of SMA. The horizontal axis indicates the temperature of the SMA, and the vertical axis indicates the electrical resistance of the SMA. An example of this is Ni—Ti or Ni—Ti—Cu.

As shown by the solid line in FIG. 4, the SMA 15 used in the present embodiment has a crystalline phase called a martensite phase (low temperature phase) at a temperature below a certain level, and the wire is elongated. As the temperature is increased, one of the hysteresis loops is traced, and abrupt contraction starts from a specific temperature (As point), and the resistance value decreases according to the amount of displacement in the contraction direction. When the temperature is raised above a specific temperature (Af point), the contraction of the wire ends and a crystalline phase called an austenite phase (high temperature phase) is reached (temperature rise process). When the temperature is lowered from this state, the other side of the hysteresis loop is followed, and the temperature suddenly extends from a specific temperature (Ms point), and the amount of displacement in the contraction direction decreases. When the temperature is lowered below a specific temperature (Mf point), the elongation ends and returns to the martensite phase (temperature lowering process). The SMA 15 generally has hysteresis as shown in FIG. 4 in the temperature-resistance characteristic, and there is a relationship of Mf point <As point and Ms point <Af point.

FIG. 5 is a graph showing the temperature-resistance value characteristics of the SMA in the SMA actuator according to the embodiment. The horizontal axis indicates the temperature of SMA, and the vertical axis indicates the electrical resistance of SMA.

In the present embodiment, the resistance value of the SMA 15 changes from the initial resistance value Rstart at the start of energization to the maximum resistance value Rmax at the As point as the temperature rises due to energization, and the lens 2 starts to move from the infinite end to the macro end. It is used within a range in which the resistance value at the time (hereinafter, infinite end resistance value Rinf) is changed to the resistance value (hereinafter, macro resistance value Rmcr) when the lens 2 is at the macro end. Since the lens 2 is not extended beyond the macro end by the mechanism shown in FIGS. 1 and 2, the curve in FIG. 4 is shown as the operation of the lens 2 from the infinite end to the macro end in FIG.

FIG. 6 is a graph showing the displacement-resistance value characteristics of SMA in the SMA actuator according to the embodiment. The horizontal axis indicates the displacement of the lens, and the vertical axis indicates the resistance value of SMA.

When the operation of FIG. 5 is represented by the relationship between the displacement and the resistance value, as shown in FIG. 6, in the temperature rising process, the resistance value changes in order from the initial resistance value Rstart to the maximum resistance value Rmax to the infinite end resistance value Rinf. In the process, the displacement of the lens 2 is zero (the lens barrel 4 does not move), and in the process of sequentially changing from the infinite end resistance value Rinf to the macro resistance value Rmcr, the displacement of the lens 2 is reduced as the resistance value decreases. , Increase (the barrel 4 moves toward the macro end). In the temperature lowering process, the displacement of the lens 2 decreases in the process of changing in order from the macro resistance value Rmcr to the infinite end resistance value Rinf (the barrel 4 moves toward the infinite end direction), and the infinite end resistance value Rinf to maximum In the process of sequentially changing from the resistance value Rmax to the initial resistance value Rstart, the displacement of the lens 2 is zero. In the displacement-resistance characteristic curve of the lens 2 in FIG. 6, it is assumed that there is almost no hysteresis in the temperature increasing process and the temperature decreasing process. This is because the hysteresis becomes very small and can be ignored by appropriately processing the Ni-Ti-Cu SMA 15. Thus, by performing an appropriate process on the SMA 15, the performance of displacement control using the resistance value as an index can be improved. Furthermore, if a wire material having a sufficiently high temperature at the As point is used with respect to the upper limit of the operating temperature range of the SMA 15, the SMA 15 does not transform from the low temperature phase with respect to the ambient temperature. Therefore, there is no need to consider hysteresis.

FIG. 7 is a graph for explaining control by a conventional position control device. FIG. 7A is a schematic graph for explaining a change in electrical resistance accompanying a temperature change of SMA. The horizontal axis indicates the temperature of SMA, and the vertical axis indicates the electrical resistance of SMA. FIG. 7B is a schematic graph for explaining the relationship between the electrical resistance of the SMA and the displacement of the lens. The horizontal axis indicates the temperature of SMA, and the vertical axis indicates the electrical resistance of SMA.

Here, conventional position control will be described. If the initial resistance value Rstart is smaller than the first target value Rtgt1, the property that the resistance value of the SMA 15 linearly changes in its displacement cannot be used without detecting the maximum resistance value Rmax of the SMA 15. The reason is described below. For example, the first target value Rtgt1 is set to the infinite end resistance value Rinf. In this case, at the time of start-up, the SMA 15 is in the state P0 (initial resistance value Rstart) in FIG. 7 and the initial resistance value Rstart <the first target value Rtgt1. Trying to lower the temperature, but at the start of energization, the temperature of the SMA 15 is not raised again (it is in a state of being completely radiated naturally), so that the temperature does not further drop and does not move from the state P0. Defects occur. Thus, when the initial resistance value Rstart at the time of activation is a value smaller than the first target value Rtgt1, an operation failure occurs in which the SMA 15 does not move from the state at the time of activation.

Therefore, in the present embodiment, by setting the first target value Rtgt1 to be a value smaller than the initial resistance value Rstart, the operation is performed as described below so that such a malfunction does not occur.

FIG. 8 is a graph for explaining control by the position control apparatus according to the embodiment. FIG. 8A is a schematic graph for explaining a change in electrical resistance accompanying a temperature change of SMA. The horizontal axis indicates the temperature of SMA, and the vertical axis indicates the electrical resistance of SMA. FIG. 8B is a schematic graph for explaining the relationship between the electrical resistance of the SMA and the displacement of the lens. The horizontal axis shows the displacement of the lens, and the vertical axis shows the electrical resistance of SMA.

In this embodiment, at the time of start-up, a resistance value smaller than the initial resistance value Rstart is set as the first target value Rtgt1, and initial control is started. According to this setting, since the initial resistance value Rstart> the first target value Rtgt1, the energization amount to the SMA 15 increases and the temperature rise of the SMA 15 starts. 8A and 8B, the temperature of the SMA 15 rises from the state P0 to the state P1, and the displacement of the SMA 15 changes from the infinite end to the displacement X1. .

FIG. 9 is a graph for explaining the initial control by the position control device according to the embodiment. FIG. 9A is a schematic graph showing an example of the operation of the SMA according to the present embodiment. The horizontal axis represents time, and the vertical axis represents SMA electrical resistance. FIG. 9B is a schematic graph showing the displacement of the lens according to the present embodiment. The horizontal axis shows the displacement of the lens, and the vertical axis shows the electrical resistance of SMA.

The controller 34 sets the first target value Rtgt1 based on the initial resistance value Rstart detected at the time of activation (hereinafter, time t0). According to the present embodiment, since the initial resistance value Rstart> the first target value Rtgt1, the energization amount to the SMA 15 is increased to raise the temperature. As the temperature rises, the resistance value of the SMA 15 increases to the maximum resistance value Rmax and decreases from the maximum resistance value Rmax. The resistance value of the SMA 15 becomes the infinite end resistance value Rinf at time tinf, the lens barrel 4 starts to move from the infinite end, and the displacement increases. The temperature of the SMA 15 is further increased from the time tinf until the resistance value reaches the first target value Rtgt1, and the state P1 of FIG. 8 is reached at the time t1, and the displacement becomes X1. And after it will be in the state P1, the position control apparatus 31 will maintain the energization amount to SMA15.

FIG. 10 is a graph for explaining the reference position control by the position control device according to the present embodiment. FIG. 10A is a schematic graph for explaining a change in electrical resistance accompanying a temperature change of SMA. The horizontal axis indicates the temperature of SMA, and the vertical axis indicates the electrical resistance of SMA. FIG. 10B is a schematic graph for explaining the relationship between the electrical resistance of the SMA and the displacement of the lens. The horizontal axis shows the displacement of the lens, and the vertical axis shows the electrical resistance of SMA. The state P1 'is a state at the start of the reference position control, but is the same state as the state P1 as long as the state after the initial control is maintained.

In the present embodiment, the target resistance value in the reference position control (hereinafter referred to as the second target value Rtgt2) is larger than the first target value Rtgt1 (state P1 ′). However, the lens 2 can be moved to the reference position (infinite end) even if the endless end, which is the reference position to wait for moving to the target displacement position, has been exceeded.

The second target value Rtgt2 is a value obtained by adding the differential resistance value Rbak stored in advance to the initial resistance value Rstart. Further, it is assumed that the infinite end resistance value Rinf <the second target value Rtgt2 <the maximum resistance value Rmax. As shown in FIG. 10, since the detected resistance value is the first target value Rtgt1 in the state P1 ′, the detected resistance value <the second target value Rtgt2, and the amount of current supplied to the SMA 15 is reduced to start the temperature decrease. . Accordingly, the temperature of the SMA 15 decreases from the state P1 'to the state P2 along the path indicated by the wavy arrow in FIG. 10, and the displacement of the lens 2 becomes an infinite end in the state P2.

According to such a configuration, even after the initial control, the lens 2 can be moved to the reference position even if the position of the lens 2 has gone too far from the reference position, which is a position that should be on standby for moving to the target displacement position. .

FIG. 11 is a graph for explaining the initial control and the reference position control by the position control device according to the present embodiment. FIG. 11A is a schematic graph showing an example of the operation of the SMA according to the present embodiment. The horizontal axis represents time, and the vertical axis represents SMA electrical resistance. FIG. 11B is a schematic graph showing the operation of the lens according to the present embodiment. The horizontal axis indicates time, and the vertical axis indicates lens displacement.

The position control device 31 sets the second target value Rtgt2 from time t1 'and starts servo control, and detects the resistance value in the state P1'. Since the detected resistance value is smaller than the second target value Rtgt2, the energization amount is decreased to lower the temperature (increase the resistance value), reach the infinite end resistance value Rinf at time tinf, and the displacement of the lens 2 is The lens 2 becomes infinite and stops. Further, the temperature is lowered until the resistance value increases to the second target value Rtgt2, and the state P2 of FIG. 10 is reached at time t2, but the displacement in the state P2 is an infinite end. And after it will be in the state P2, that state is maintained. The above is the control operation from the state P1 'to the reference position control end state P2.

In the state P2, since the resistance value is larger than that at the infinite end, if the target resistance value is decreased stepwise thereafter, the displacement increases gradually from the infinite end toward the macro end. By sequentially evaluating the contrast of the image input from the image sensor 25 while operating in this manner, a so-called autofocus scanning operation can be performed.

FIG. 12 is a flowchart for explaining the initial control and the reference position control by the position control device according to the present embodiment. The flow is executed when the position control device 31 is activated. Steps S1 to S3 are initial control, and steps S4 to S5 are reference position control.

In step S1, the resistance value detection unit 32 detects the initial resistance value Rstart, and in step S2, the controller 24 sets the first target value Rtgt1 to a value obtained by subtracting a previously stored value α from the initial resistance value Rstart. The predetermined value α may be a value that is larger than the detection error of the resistance value, and may be a very small value. In step S <b> 3, the control unit 21 starts servo control, and ends servo control when the first target value Rtgt <b> 1 reaches “initial resistance value Rstart−α”.

Subsequently, in step S4, the controller 24 sets the second target value Rtgt2 to a value obtained by adding the differential resistance value Rbak stored in advance to the initial resistance value Rstart. A method for selecting the differential resistance value Rbak will be described later. In step S5, the control unit 21 starts servo control, and ends servo control when the second target value Rtgt2 reaches “initial resistance value Rstart + differential resistance value Rbak”.

Hereinafter, a method for selecting the differential resistance value Rbak will be described. FIG. 13 is a graph showing the ambient temperature-resistance value characteristics of SMA. The horizontal axis indicates the ambient temperature of the SMA, and the vertical axis indicates the electrical resistance of the SMA. In the figure, Tmin, Tmax, and Tinf are the lower limit temperature, upper limit temperature, and infinite end temperature of the operating temperature range, respectively, and the corresponding lower limit resistance value, upper limit resistance value, and infinite end resistance value of SMA are R (Tmin), R (Tmax), and Rinf. Therefore, the initial resistance value Rstart is lower limit temperature resistance value R (Tmin) <initial resistance value Rstart <upper limit temperature resistance value R (Tmax).

The differential resistance value Rbak may be selected so as to satisfy both of the following conditions.

Differential resistance value Rbak> Infinite end resistance value Rinf−R (Tmin) (1)
Differential resistance value Rbak <maximum resistance value Rmax−infinite end resistance value Rinf (2)

(1) is a condition that guarantees that the lens displacement returns to the infinite end at the lower limit of the temperature range of the differential resistance value Rbak. More specifically, the equation (1) is obtained by modifying the equation using the lower limit temperature resistance value R (Tmin) <initial resistance value Rstart and the second target value Rtgt2 = initial resistance value Rstart + differential resistance value Rbak. Second target value Rtgt2> Infinite end resistance value Rinf−Lower limit temperature resistance value R (Tmin) + Initial resistance value Rstart, that is, second target value Rtgt2> Infinite end resistance value Rinf. That is, by selecting the differential resistance value Rbak that satisfies the equation (1), it is guaranteed that the displacement of the lens returns to the infinite end.

Equation (2) is a condition that guarantees that the SMA 15 does not return to the low temperature phase at the upper limit of the temperature range of the differential resistance value Rbak. More specifically, by changing the equation using the second target value Rtgt2 = the initial resistance value Rstart + the differential resistance value Rbak, the equation (2) becomes the second target value Rtgt2 <the maximum resistance value Rmax + the initial resistance value Rstart−. The infinite end resistance value Rinf. In the range from the lower limit temperature Tmin to the temperature Tinf where the ambient temperature is the same as the resistance value at the infinite end, the initial resistance value Rstart <the infinite end resistance value Rinf. That is, by selecting the differential resistance value Rbak that satisfies the equation (2), the second target value Rtgt2 does not exceed the maximum resistance value Rmax, so that it is guaranteed that the SMA 15 does not return to the low temperature phase. On the other hand, in a temperature range (in a high temperature environment) higher than the temperature Tinf where the ambient temperature becomes the same as the resistance value at the infinite end, the initial resistance value Rstart> the infinite end resistance value Rinf, and the SMA 15 is in the initial state as will be described later. Since the process returns to P0, the autofocus lens can be scanned from the infinite end, so that the problem of malfunction does not occur.

In actual design, the differential resistance value Rbak value is a set value having a sufficient margin in consideration of solid variations of the infinite end resistance value Rinf−R (Tmin) and the maximum resistance value Rmax−infinite end resistance value Rinf. . Further, the differential resistance value Rbak value may be a value considering the detection error of the resistance value.

Hereinafter, the initial control and the reference position control by the position control device 31 in a high temperature environment will be described with reference to FIGS.

FIG. 14 is a graph for explaining the initial control by the position control device according to the present embodiment in a high-temperature environment. FIG. 14A is a schematic graph for explaining a change in electrical resistance accompanying a temperature change of SMA. The horizontal axis indicates the temperature of SMA, and the vertical axis indicates the electrical resistance of SMA. FIG. 14B is a schematic graph for explaining the relationship between the electrical resistance of the SMA and the displacement of the lens. The horizontal axis shows the displacement of the lens, and the vertical axis shows the electrical resistance of SMA.

As described above, the initial resistance value Rstart> the infinite end resistance value Rinf. Therefore, the first target value Rtgt1 for the initial control is smaller than the initial resistance value Rstart, but larger than the infinite end resistance value Rinf. By the initial control, the SMA 15 changes from the initial state P0 to the state P1 along a path indicated by a broken-line arrow in the drawing. However, in the state P1, the displacement of the lens 2 remains at the infinite end, and the lens 2 does not start to move.

FIG. 15 is a graph for explaining the reference position control by the position control device according to the present embodiment in a high temperature environment. FIG. 15A is a schematic graph for explaining a change in electrical resistance accompanying a temperature change of SMA. The horizontal axis indicates the temperature of SMA, and the vertical axis indicates the electrical resistance of SMA. FIG. 15B is a schematic graph for explaining the relationship between the electrical resistance of the SMA and the displacement of the lens. The horizontal axis shows the displacement of the lens, and the vertical axis shows the electrical resistance of SMA. The state P1 'is a state at the start of the reference position control, but is the same as P1 if the initial control end state is maintained.

In the reference position control, the controller 34 sets the second target value Rtgt2. Second target value Rtgt2 = initial resistance value Rstart + differential resistance value Rbak. Further, it is assumed that the initial resistance value Rstart <the maximum resistance value Rmax <the second target value Rtgt2.

In the state P1 ', since the detection resistance value <the second target value Rtgt2, the energization amount is decreased and the temperature decrease is started. Therefore, the temperature decreases from the state P1 'to the state P2 along the path indicated by the broken-line arrow in the figure, and returns to the vicinity of the initial P0. The displacement of the lens 2 remains at the infinite end.

FIG. 16 is a graph for explaining the initial control and the reference position control by the position control device according to the present embodiment under a high temperature environment. FIG. 16A is a schematic graph showing an example of the operation of the SMA according to the embodiment of the present invention. The horizontal axis represents time, and the vertical axis represents SMA electrical resistance. FIG. 16B is a schematic graph showing the operation of the lens according to the embodiment of the present invention. The horizontal axis indicates time, and the vertical axis indicates lens displacement.

When the position control device 31 sets the first target value Rtgt1 at the time t0 and starts the servo control, the SMA 15 reaches the first target value Rtgt1 at the time t1 via the maximum resistance value Rmax due to the temperature rise due to the increase in energization. Time t1 corresponds to the state P1. Next, the position control device sets the second target value Rtgt2 at time t1 'and starts servo control. Due to the temperature drop due to the decrease in energization, the position controller again passes through the maximum resistance value Rmax and reaches the initial resistance value Rstart at time t2. Time t2 corresponds to state P2. Through this process, the displacement of the lens 2 remains at the infinite end, and the lens 2 does not move from the infinite end.

In the state P2, since the resistance value is larger than that at the infinite end, the target value is then reduced stepwise, and if it becomes smaller than the initial resistance value Rstart, servo control is performed so that the detected resistance value becomes the target value due to increased energization. The At time t2, the displacement remains 0 because it has not yet reached the infinite end. Furthermore, if the target resistance value is decreased stepwise, the displacement increases stepwise from the infinite end toward the macro end.

Thus, by selecting the differential resistance value Rbak that satisfies the equations (1) and (2) regardless of the ambient temperature, the displacement of the lens 2 is at the infinite end after the reference position control. Focus operation becomes possible.

In this other embodiment, the controller 34 further stores the relationship between the initial resistance value Rstart and the ambient temperature as shown in FIG. 13 and the relationship between the ambient temperature and the differential resistance value Rbak, and the resistance value of the SMA 15. The ambient temperature is obtained from the initial resistance value Rstart based on the relationship between the ambient temperature and the ambient temperature, the differential resistance value Rbak is obtained based on the relationship between the obtained ambient temperature and the differential resistance value Rbak, and the obtained differential resistance value Rbak. The reference position control may be performed using.

According to such a configuration, it becomes possible to change the value of the differential resistance value Rbak according to the obtained ambient temperature of the SMA 15, and the movement start delay in the autofocus scanning operation is less. The relationship between the ambient temperature and the differential resistance value Rbak is as follows. In a temperature range (in a high temperature environment) greater than the temperature Tinf where the ambient temperature is the same as the resistance value at the infinite end (under a high temperature environment), the differential resistance value Rbak may be a value greater than the resistance value detection error. In a temperature range lower than the temperature Tinf where the ambient temperature is the same as the resistance value at the infinite end, the differential resistance value may satisfy the expressions (1) and (2).

Furthermore, in this other embodiment, as shown by the broken line in FIG. 3, the temperature detector 23 further detects the ambient temperature of the SMA 15, and the controller 34 preliminarily shows the relationship between the ambient temperature and the differential resistance value Rbak. The differential resistance value Rbak is obtained from the ambient temperature detected by the temperature detection unit 23 based on the relationship between the ambient temperature and the differential resistance value Rbak, and the reference position control is performed using the obtained differential resistance value Rbak.

The temperature detection unit 23 includes a temperature sensor such as a thermistor, a thermocouple, and a thin film resistor. For example, the lever 13 is provided at a portion of the notch 13a around which the SMA 15 is wound.

According to such a configuration, the value of the differential resistance value Rbak can be changed depending on the detected ambient temperature of the SMA 15, and the movement start delay in the autofocus scanning operation is less.

This specification discloses various modes of technology as described above, and the main technologies are summarized below.

A position control device according to one aspect is used for a shape memory alloy actuator that moves a movable portion using a shape memory alloy, and is a position control device that controls the position of the movable portion, and energizes the shape memory alloy. A drive unit to perform, a resistance value detection unit to detect a resistance value of the shape memory alloy, and a target resistance value corresponding to a target displacement position of the movable unit, so that the resistance value matches the target resistance value And a control unit that controls the amount of current applied to the shape memory alloy by the drive unit, and the control unit provides the resistance value detection unit with the shape memory alloy as a preparatory operation for controlling the position of the movable unit. The resistance value of the shape memory alloy is detected as an initial resistance value, and the target resistance value is set to a value smaller than the initial resistance value. Performing a first control to start the transformation to the high temperature phase.

According to this configuration, as the preparatory operation for controlling the position of the movable part, the target resistance value is set to a value smaller than the initial resistance value, and the shape memory alloy starts to transform from the low temperature phase to the high temperature phase. The position of the shape memory alloy can be controlled by utilizing the property that the resistance value of the shape memory alloy changes linearly with the displacement without detecting the maximum resistance value Rmax of the shape memory alloy.

In another aspect, the above-described position control device preferably further includes a storage unit that stores a predetermined differential resistance value that is set in advance, and the control unit is configured to perform the target resistance after the first control. The value is set to a value obtained by adding the differential resistance value to the initial resistance value, and second control is performed to control the energization amount for the shape memory alloy, thereby moving the movable portion to a reference position.

According to this configuration, after the first control, the position control device moves the movable part to the reference position even if the position of the movable part has exceeded the reference position, which is a position to be on standby for moving to the target displacement position. Can be made.

In another aspect, the above-described position control device preferably further includes a temperature detection unit that detects an ambient temperature of the shape memory alloy actuator, and the storage unit includes the ambient temperature and the differential resistance value. The control unit obtains the differential resistance value from the ambient temperature detected by the temperature detection unit based on the relationship between the ambient temperature and the differential resistance value. Second control is performed with the differential resistance value.

According to this configuration, the optimum differential resistance value corresponding to the ambient temperature can be set, so that the position control device can move the movable part to the target displacement position in a shorter time.

In another aspect, in the above-described position control device, preferably, the storage unit includes a relationship between the resistance value of the shape memory alloy actuator and the ambient temperature, and the relationship between the ambient temperature and the differential resistance value. Further storing a relationship, the control unit obtains the ambient temperature from the initial resistance value based on the relationship between the resistance value of the shape memory alloy and the ambient temperature, from the obtained ambient temperature, the ambient temperature and the The differential resistance value is obtained based on the relationship with the differential resistance value, and second control is performed using the obtained differential resistance value.

According to this configuration, since the optimum differential resistance value corresponding to the estimated ambient temperature can be set without providing the temperature detection unit, the position control device can move the movable unit to the target displacement position in a shorter time. Can be moved to.

Further, a position control method according to another aspect is a position control method for controlling a position of the movable part, which is used for a shape memory alloy actuator that moves a movable part using a shape memory alloy, the movable part Detecting the resistance value of the shape memory alloy as an initial resistance value, and setting the target resistance value corresponding to the target displacement position of the movable part to a value smaller than the initial resistance value. And a step of starting the transformation of the shape memory alloy from a low temperature phase to a high temperature phase by controlling the amount of current applied to the shape memory alloy with the set target resistance value.

In another aspect, in the above-described position control method, preferably, the target resistance value is set to the initial resistance value after the step of storing a predetermined differential resistance value determined in advance and the step of starting the transformation. A step of setting the difference resistance value to a value added, and a step of controlling the energization amount to the shape memory alloy with the set target resistance value to move the movable part to a reference position at the time of activation. And further comprising.

According to this configuration, in the position control method, after the step of starting the transformation, even if the position of the movable portion exceeds the reference position that is a position to be on standby for moving to the target displacement position, the position of the movable portion is set to the reference position. Can be moved to.

Further, a driving device according to another aspect includes a shape memory alloy actuator that moves a movable portion using a shape memory alloy, and a position control device that controls a position of the movable portion, and the position control device includes: One of the position control devices described above.

According to this configuration, a driving device including any one of the above-described position control devices is provided, and a driving device capable of controlling the position of the movable portion based on the resistance value of the shape memory alloy without including a position sensor is provided. Is done.

An imaging apparatus according to another aspect includes a shape memory alloy actuator that moves a movable portion using a shape memory alloy, a lens that moves according to the movement of the movable portion, and an imaging optical system that includes the lens. An image pickup device that picks up an optical image of the imaged subject, and a position control device that controls the position of the movable portion, and the position control device is one of the above-described position control devices, and the lens The first control is performed as a preparatory operation for moving.

According to such a configuration, an imaging device including any of the above-described position control devices is provided, and an imaging device capable of controlling the lens position based on the resistance value of the shape memory alloy without including a position sensor. Provided.

This application is based on Japanese Patent Application No. 2010-48819 filed on Mar. 5, 2010, the contents of which are included in this application.

In order to express the present invention, the present invention has been properly and fully described through the embodiments with reference to the drawings. However, those skilled in the art can easily change and / or improve the above-described embodiments. It should be recognized that this is possible. Therefore, unless the modifications or improvements implemented by those skilled in the art are at a level that departs from the scope of the claims recited in the claims, the modifications or improvements are not covered by the claims. To be construed as inclusive.

According to the present invention, a position control device, a position control method, a drive device, and an imaging device can be provided.

Claims

In a position memory device that is used in a shape memory alloy actuator that moves a movable part using a shape memory alloy and controls the position of the movable part,
A drive unit for energizing the shape memory alloy;
A resistance value detection unit for detecting the resistance value of the shape memory alloy;
A control unit configured to set a target resistance value corresponding to a target displacement position of the movable unit, and to control an energization amount to the shape memory alloy by the driving unit so that the resistance value matches the target resistance value; Prepared,
The control unit causes the resistance value detection unit to detect a resistance value of the shape memory alloy as an initial resistance value as a preparatory operation for controlling the position of the movable part, and the target resistance value is a value smaller than the initial resistance value. The position control device is characterized in that the first control for starting the transformation of the shape memory alloy from the low temperature phase to the high temperature phase is performed by controlling the energization amount to the shape memory alloy.
A storage unit for storing a predetermined differential resistance value determined in advance;
After the first control, the control unit sets the target resistance value to a value obtained by adding the differential resistance value to the initial resistance value, and performs second control for controlling the energization amount to the shape memory alloy. The position control device according to claim 1, wherein the movable unit is moved to a reference position.
A temperature detection unit for detecting an ambient temperature of the shape memory alloy actuator;
The storage unit further stores a relationship between the ambient temperature and the differential resistance value,
The control unit obtains the differential resistance value based on the relationship between the ambient temperature and the differential resistance value from the ambient temperature detected by the temperature detection unit, and calculates the differential resistance value based on the obtained differential resistance value. The position control device according to claim 2, wherein two controls are performed.
The storage unit further stores the relationship between the resistance value of the shape memory alloy actuator and the ambient temperature, and the relationship between the ambient temperature and the differential resistance value,
The control unit obtains the ambient temperature from the initial resistance value based on the relationship between the resistance value of the shape memory alloy and the ambient temperature, and determines the ambient temperature and the differential resistance value from the obtained ambient temperature. The position control device according to claim 2, wherein the differential resistance value is obtained based on the relationship, and the second control is performed using the obtained differential resistance value.
In a position control method for controlling the position of the movable part used in a shape memory alloy actuator that moves the movable part using a shape memory alloy,
As a preparation for controlling the position of the movable part, a step of detecting the resistance value of the shape memory alloy as an initial resistance value, and the target resistance value corresponding to the target displacement position of the movable part is smaller than the initial resistance value. And a step of controlling the amount of current applied to the shape memory alloy with the set target resistance value and starting transformation of the shape memory alloy from a low temperature phase to a high temperature phase. A characteristic position control method.
Storing a predetermined differential resistance value determined in advance;
After the step of starting the transformation, setting the target resistance value as a value obtained by adding the differential resistance value to the initial resistance value, and the energization amount to the shape memory alloy with the set target resistance value The position control method according to claim 5, further comprising: controlling the movable portion to move the movable portion to a reference position.
A shape memory alloy actuator that moves the movable part using a shape memory alloy; and
A position control device for controlling the position of the movable part,
The drive device according to any one of claims 1 to 4, wherein the position control device is the position control device according to any one of claims 1 to 4.
A shape memory alloy actuator that moves the movable part using a shape memory alloy; and
A lens that moves according to the movement of the movable part;
An image sensor that captures an optical image of a subject imaged by an imaging optical system including the lens;
A position control device for controlling the position of the movable part,
The image pickup apparatus according to any one of claims 1 to 4, wherein the position control apparatus performs the first control as a preparatory operation for moving the lens.