WO2012005072A1

WO2012005072A1 - Shape-memory alloy actuator control device and optical component drive unit

Info

Publication number: WO2012005072A1
Application number: PCT/JP2011/062802
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: 2010-07-09
Filing date: 2011-06-03
Publication date: 2012-01-12

Abstract

Disclosed is an actuator control device using a wire-shaped shape-memory alloy (SMA), which energizes an SMA actuator (3), and variably sets the value of current applied to the SMA actuator (3) in accordance with the wire diameter of the SMA, to satisfy predetermined energization reference conditions. The information of the wire diameter may be preliminarily stored in the device, or can be obtained on the basis of the energization for inspection within the device. The determined current to be applied is used as a criteria, and the current to be applied to the SMA is controlled to change the current in accordance with the value of an operation command sent to the actuator. Thus, the control can be optimized to improve the response, regardless of the wire diameter of the SMA.

Description

Shape memory alloy actuator controller and optical component drive unit

The present invention relates to an actuator control device using a shape memory alloy and an optical component drive unit using the same.

Many micro-camera units (MCUs) built in cellular phones are currently being produced, but in recent years, with the progress of higher image quality, the auto focus (AF) function is indispensable in order to demand image quality and user convenience. It's getting on. On the other hand, there is a very strong demand for small size and low price for MCUs as parts of mobile phones.

In addition, Ni-Ti and other shape memory alloys (Shape Memory Alloy: SMA) are known as actuators based on deformation due to temperature changes as the driving principle. Therefore, it is considered promising for applications such as the above-mentioned MCU AF.

In this application, there is a method in which the SMA wire is energized to generate Joule heat and heated. However, if the SMA wire diameter is different, the heat capacity, the heat radiation efficiency and the generated Joule heat are different. The response speed of deformation of the memory alloy is different, and particularly when feedback control is performed, the settling time may be adversely affected.

In order to prevent this, for example, as an actuator for a micro camera, the disclosure of the range of the wire diameter for ensuring responsiveness of 10 Hz or more (Patent Document 1) and the devising of the cross-sectional shape of the SMA wire can reduce heat dissipation. There has been proposed a technique (Patent Document 2) that changes and improves responsiveness.

On the other hand, in the push-pull arrangement in which two wire-like SMA wires are connected to both ends of the movable part for image blur correction, etc., the bias voltage applied to the SMA is adjusted according to the cross-sectional area of the SMA. Has been proposed (Patent Document 3).

JP 2006-336617 A JP 2007-139965 A JP 2006-329146 A

However, in Patent Technology 1, in order to optimize the responsiveness, the energization amount and the gain of feedback control are optimally designed according to the specific wire diameter in the wire to be used. As a result, a deviation occurs from the ideal optimum control. Further, even if the shape is devised as in Patent Document 2, the cause of variation still remains.

Patent Document 3 adjusts the bias voltage for the purpose of preventing overheating / insufficiency of SMA caused by variations in the SMA cross-sectional area in the push-pull arrangement, and optimizes control response in an excessive state. It is not a thing.

The present invention has been made in view of such circumstances, and even when the SMA wire diameter varies, the responsiveness of the actuator is improved by the stable optimum control, and the speed of stabilization is increased. It is an object of the present invention to provide a shape memory alloy actuator control device that can be used.

In order to solve the above problems, a shape memory alloy actuator control device according to a first aspect is a shape memory alloy actuator control device that controls an actuator using a shape restoring force due to a temperature change of a wire-like shape memory alloy. In addition, the energization unit for energizing the shape memory alloy and the value of the energization current to the shape memory alloy for satisfying a predetermined energization reference condition are variably set according to the wire diameter of the shape memory alloy An energization control unit that performs energization control on the shape memory alloy by giving the energization unit a control signal that changes in accordance with an operation command value to the actuator, using the current setting unit as a reference, It is characterized by providing.

The shape memory alloy actuator control device according to the second aspect is the shape memory alloy actuator control device according to the first aspect, wherein the current setting unit controls the energization unit to inspect the shape memory alloy. An inspection energization control unit for energizing and an inspection processing unit for determining a value of the energization current based on a result of the inspection energization to the shape memory alloy, and the energization control unit in the actual drive of the actuator The value of the energization current determined by the inspection energization is used.

The shape memory alloy actuator control device according to a third aspect is the shape memory alloy actuator control device according to the second aspect, wherein the inspection energization applies a current smaller than a current range in actual driving of the actuator to the shape. The test processing unit determines the value of the energization current based on the energization result with the small current.

The shape memory alloy actuator control device according to a fourth aspect is the shape memory alloy actuator control device according to the second or third aspect, wherein the inspection processing unit detects the shape memory alloy detected by the inspection energization. The value of the energization current is determined based on the resistance value of the shape memory alloy, and the resistance value of the shape memory alloy correlates with the wire diameter of the shape memory alloy. It is determined as a value reflecting the diameter of the memory alloy.

A shape memory alloy actuator control device according to a fifth aspect is the shape memory alloy actuator control device according to any one of the second to fourth aspects, wherein the temperature specification for specifying the temperature of the shape memory alloy or its surroundings And a temperature compensation unit that performs temperature compensation when determining the value of the energization current by changing the energization reference condition according to the temperature identified by the temperature identification unit. And

A shape memory alloy actuator control device according to a sixth aspect is the shape memory alloy actuator control device according to the fifth aspect, wherein the temperature specifying unit is a temperature sensor disposed in the vicinity of the shape memory alloy. And the temperature compensation unit performs the temperature compensation according to a temperature detected by the temperature sensor.

The shape memory alloy actuator control device according to a seventh aspect is the shape memory alloy actuator control device according to the fifth aspect, wherein the temperature specifying unit uses the resistance value of the shape memory alloy as a substitute index of the temperature. A resistance value detection unit for detecting, and performing the temperature compensation when determining the value of the energization current by changing the energization reference condition using the resistance value as a substitute index of the temperature. To do.

The shape memory alloy actuator control device according to an eighth aspect is the shape memory alloy actuator control device according to the first aspect, wherein the current setting unit is configured to store wire diameter information corresponding to the wire diameter of the shape memory alloy. A wire diameter information storage unit that stores a value, and a current value determination unit that determines a value of the energization current based on the value of the wire diameter information.

The shape memory alloy actuator control device according to a ninth aspect is the shape memory alloy actuator control device according to the eighth aspect, wherein the wire diameter information is a wire diameter of the shape memory alloy measured in advance, The current value determination unit includes a conversion unit that converts the value of the wire diameter stored in the wire diameter information storage unit into the value of the energization current.

The shape memory alloy actuator control device according to a tenth aspect is the shape memory alloy actuator control device according to the eighth aspect, wherein the wire diameter information storage unit stores a resistance value of the shape memory alloy, The current value determination unit includes a conversion unit that converts the resistance value into a value of the energization current, and determines the value of the energization current based on a conversion result of the conversion unit.

The shape memory alloy actuator control device according to an eleventh aspect is the shape memory alloy actuator control device according to the tenth aspect, wherein the wire diameter information storage unit measures the resistance value of the shape memory alloy. The temperature is stored together with the resistance value, and the conversion unit performs temperature compensation when determining the value of the energizing current by converting the combination of the resistance value and the temperature into the value of the energizing current. It is characterized by that.

A shape memory alloy actuator control device according to a twelfth aspect is the shape memory alloy actuator control device according to any one of the first to eleventh aspects, wherein the resistance value is a value representing the resistance of the shape memory alloy. A resistance value detection unit that detects the resistance value, a comparison unit that compares the resistance value detected by the resistance value detection unit and a target resistance value as a value representing the target resistance value, and the energization control unit includes: When the shape memory alloy is deformed into a desired shape, the shape memory alloy is reduced so that a difference between the resistance value signal obtained by the resistance value detection unit and the target resistance value signal is reduced. The average energization current is controlled.

A shape memory alloy actuator control device according to a thirteenth aspect is a shape memory alloy actuator control device according to any one of the first to twelfth aspects, wherein the energization control unit is configured to control the shape memory alloy by a PWM method. Conducting control is performed to change at least one of a pulse amplitude and a pulse width to the shape memory alloy.

An optical component driving unit according to a fourteenth aspect includes an actuator that drives a predetermined optical component using a shape restoring force due to a temperature change of a wire-shaped shape memory alloy, and any one of the first to thirteenth aspects. And a shape memory alloy actuator control device according to the above.

According to the shape memory alloy actuator control device according to the first to fourteenth aspects, the energization conditions can be variably set according to the SMA wire diameter, and energization control according to the wire diameter becomes possible. Even if the wire diameter of the SMA varies, the responsiveness of the actuator is improved by stable optimum control, and the static stabilization speed is also increased.

According to the shape memory alloy actuator control device according to the second to fourth aspects, in order to determine the energization current based on the result of the inspection energization performed at an appropriate time such as immediately after the start, There is no need to measure the diameter and store it in the device.

According to the shape memory alloy actuator control apparatus according to the third aspect, since the value of the energization current is determined by the inspection energization of the current smaller than the current range in the actual drive of the actuator, a significant temperature change is caused. Therefore, it is possible to determine the energization current stably reflecting the wire diameter of the shape memory alloy.

According to the shape memory alloy actuator control device according to the fourth aspect, the resistance value of the shape memory alloy is detected, and the value of the energization current is determined using the correlation between the resistance value and the wire diameter. There is a clear correlation between the resistance value and the wire diameter. For this reason, the value of the energization current can be accurately determined through electrical measurement without actually measuring the wire diameter itself of the shape memory alloy.

According to the shape memory alloy actuator control device according to the fifth to seventh and eleventh aspects, the energization current can be determined more appropriately by performing temperature compensation.

According to the shape memory alloy actuator control apparatus according to the eighth to tenth aspects, the wire diameter (or information correlated with the wire diameter) measured at the manufacturing factory or the like as the wire diameter information is previously stored in the apparatus as the wire diameter information. Since it is stored, it can be read and used when the actuator is driven, and the internal processing for determining the energization current can be simplified to shorten the control time.

According to the shape memory alloy actuator control device according to the thirteenth aspect, by applying the configuration for determining the energization current according to the wire diameter to the PWM drive type shape memory alloy actuator control device, the power supply voltage is reduced. Thus, the effect of reducing power consumption can be increased.

FIG. 1 is a plan view schematically showing an essential part of a lens driving system using an SMA driving device according to an embodiment of the present invention. FIG. 2 is a side view showing the operation of the lens driving system of FIG. FIG. 3 is a diagram for explaining that the driving response of the SMA lens driving unit varies depending on the SMA wire diameter. FIG. 4 is a graph showing the temperature dependence of the resistance value and the amount of expansion / contraction of SMA as a characteristic curve. FIG. 5 is a diagram showing the temperature dependence of the resistance value and lens displacement of SMA as a characteristic curve. FIG. 6 is a graph showing the lens displacement dependence of the resistance value of SMA as a characteristic curve. FIG. 7 is a block diagram showing the configuration of the SMA actuator control apparatus according to one embodiment. FIG. 8 is a diagram illustrating an SMA energization waveform. FIG. 9 is a diagram for explaining the correlation between the SMA wire diameter and its physical characteristics. FIG. 10 is a flowchart for explaining the operation of the SMA actuator control apparatus according to the embodiment. FIG. 11 is a block diagram showing the configuration of the SMA actuator control device according to one embodiment. FIG. 12 is a flowchart for explaining the operation of the SMA actuator controller according to the embodiment. FIG. 13 is a diagram showing an example of a temperature / target voltage table for temperature compensation. FIG. 14 is a diagram showing an example of a setting table for energization parameters corresponding to the wire diameter and temperature. FIG. 15 is a diagram showing an example of a table for temperature estimation by resistance detection. FIG. 16 is a diagram showing an example of a table for temperature estimation by resistance detection. FIG. 17 is a diagram showing a table example for temperature estimation by resistance detection.

<1. Overview and Configuration of Lens Drive Unit (Optical Component Drive Unit) Mechanism>
FIG. 1 and FIG. 2 are diagrams schematically showing a main part of a mechanism in a lens driving unit (optical component driving unit) 100 configured using the SMA actuator control device according to the embodiment of the present invention. Among these, FIG. 1 is a plan view (lens opening surface) viewed from the lens side, and FIG. 2 is a side view viewed from the direction of arrow A in FIG. 2A shows a state before driving, and FIG. 2B shows a state after driving.

The lens driving unit 100 is used in a small camera system or the like incorporated in a mobile phone, and performs an AF operation using an actuator using an SMA (SMA actuator) as a driving source.

In a specific configuration, the lens driving unit 100 mainly includes a lens unit 1 (driven object), a lever member 2 that moves the lens unit 1 in the optical axis AX direction (first axis direction), an SMA actuator 3, A base member 4, a top plate 5, parallel plate springs 6 a and 6 b, a bias spring 7, and the like are provided, and the lens unit 1 and the like are assembled to the base member 4. The top plate 5 and the

parallel leaf springs

6a and 6b are omitted in FIG. 1 for convenience.

The base member 4 is fixed to a member (for example, a mobile phone frame or a mount substrate) to which the lens driving unit 100 is attached, and is a non-moving member constituting the bottom side of the lens driving unit 100. The base member 4 is formed in a square plate shape in plan view, and is entirely made of a resin material or the like.

The lens unit 1 has a cylindrical shape, and includes an imaging lens 10, a lens driving frame 12 that holds the imaging lens 10, and a lens barrel 14 that stores the lens driving frame 12.

The imaging lens 10 includes an objective lens, a focus lens, a zoom lens, and the like, and constitutes an imaging optical system for a subject image with respect to an imaging element (not shown). The lens driving frame 12 is a so-called ball frame, and moves in the optical axis AX direction together with the lens barrel 14. A pair of support portions 16 project from the outer peripheral edge portion of the lens drive frame 12 at the distal end on the object side with an angular difference of 180 ° in the circumferential direction.

The lens unit 1 is disposed on the base member 4 in a state of being inserted into an opening formed in the top plate 5. Specifically, the pair of support portions 16 are arranged so as to be positioned in the vicinity of the pair of diagonals of the base member 4 (see FIG. 1).

Parallel plate springs 6a and 6b are fixed to the base member 4 and the top plate 5, respectively, and the lens unit 1 is fixed to the parallel plate springs 6a and 6b. Accordingly, the lens unit 1 is supported so as to be displaceable with respect to the base member 4 and the like, and the degree of freedom of displacement is restricted in a direction along the optical axis AX. Note that the top plate 5 may be fixed to the base member 4 via a support column (not shown) or may be a structure integrated with the base member 4.

The lever member 2 applies a driving force in the direction of the optical axis AX to the lens unit 1 by engaging with the lens unit 1 via the support portion 16.

The lever member 2 is disposed on the side of the lens unit 1, specifically, at one corner other than the corner where the support portion 16 of the lens unit 1 is located, which is the corner of the base member 4. . The lever member 2 is supported so as to be swingable about an axis that is orthogonal to the optical axis AX and extends in the direction in which the pair of support portions 16 are arranged (the vertical direction in FIG. 1).

As shown in FIG. 2A, the lever member 2 has an arm portion 21 and an inverted L-shape in a side view having an arm portion 21 and an extending portion 22 extending from the base end portion of the arm portion 21 in the optical axis AX direction. The bent portion serving as the boundary between the arm portion 21 and the extended portion 22 is supported on the base member 4 by being supported by the tip of the support leg 8 erected on the base member 4. ing.

The shape of the tip of the support leg 8 (hereinafter referred to as the lever support portion 8a) is a substantially cylindrical shape extending in a direction orthogonal to the optical axis AX direction (a direction orthogonal to the paper surface of FIG. 2A). Thus, the lever member 2 is supported so as to be swingable about an axis orthogonal to the optical axis AX direction with the lever support portion 8a as a fulcrum.

The arm portion 21 is formed in an arc shape in plan view. Specifically, as shown in FIG. 1, the lens unit 1 is bifurcated from the extended portion 22 to both sides of the lens unit 1 and extends evenly in the vicinity of the outer peripheral surface of the lens unit 1. Is formed so as to surround. The tips (both ends) of the arm portion 21 reach the positions of the support portions 16 of the lens unit 1, respectively. Then, the SMA actuator 3 is bridged over the extended portion 22, and a direction perpendicular to the optical axis AX direction (second axis direction: left-right direction in FIG. 2A) at this bridge position (referred to as the displacement input portion 2a). When the moving force F1 (see FIG. 2B) is input, the lever member 2 swings. Along with this swinging, the tip of the arm portion 21 (referred to as the displacement output portion 2b) is displaced in the optical axis AX direction, and the displacement output portion 2b engages with each support portion 16 to cause the lens unit 1 to move in the optical axis AX direction. A driving force is applied.

The SMA actuator 3 applies a moving force F1 (see FIG. 2 (b)) to the lever member 2, and is composed of, for example, an SMA wire such as a Ni—Ti alloy, and is a linear actuator having a substantially circular cross section. is there. In this specification, the SMA actuator 3 and the SMA wire constituting the SMA actuator 3 are also simply referred to as “SMA3”.

The SMA actuator 3 expands when given a predetermined tension in a state where the elastic modulus is low (martensite phase) at a low temperature. When heat is applied in this extended state, the SMA actuator 3 undergoes phase transformation and has a high elastic modulus (austenite). Phase: parent phase) and return to its original length from its extended state (recover shape).

In the present embodiment, a configuration is adopted in which the SMA actuator 3 is energized and heated to perform the above-described phase transformation (details will be described later). That is, since the SMA actuator 3 is a conductor having a predetermined resistance value, Joule heat is generated by energizing the SMA actuator 3 itself, and transformation from the martensite phase to the austenite phase is performed by self-heating based on the Joule heat. It is supposed to be configured. For this reason, the first electrode 30 a and the second electrode 30 b for energization heating are fixed to both ends of the SMA actuator 3. These

electrodes

30 a and 30 b are fixed to predetermined electrode fixing portions provided on the base member 4.

As shown in FIG. 1, the SMA actuator 3 is bridged between the

electrodes

30a and 30b with a portion engaging with the extending portion 22 of the lever member 2 as a turning point. With this configuration, when the SMA actuator 3 is energized and heated via the

electrodes

30a and 30b and is operated (shrinks), a movement force F1 (see FIG. 2B) is applied to the lever member 2, and this movement force F1. As a result, the lever member 2 swings.

The

electrodes

30a and 30b are arranged in the vicinity of the support portion 16 of the lens unit 1 in the base member 4, respectively. The lengths of the SMA actuator 3 from the

electrodes

30a and 30b to the turn-back point are set to be equal to each other, so that the amount of expansion / contraction of the SMA actuator 3 on both sides of the displacement input portion 2a becomes equal. Rubbing between the lever member 2 and the SMA actuator 3 is prevented. Further, a V-groove 21a (corresponding to the displacement input portion 2a) is formed in the extended portion 22, and the SMA actuator 3 is bridged so as to be fitted into the V-groove 21a, whereby the lever member 2 is On the other hand, the SMA actuator 3 is stably suspended.

In the lens moving device described above, when the SMA actuator 3 that is not energized and heated is stopped (expanded), the lens unit 1 is pressed toward the base member 4 by the pressing force of the bias spring 7, whereby the lens unit 1 is moved to the home. The position is held (see FIG. 2A). On the other hand, when the SMA actuator 3 is actuated (contracted), the actuating force applies a moving force F1 to the displacement input portion 2a of the lever member 2 to cause the lever member 2 to oscillate, and this oscillation causes the displacement output portion 2b to move to the optical axis. It moves in the AX direction (see FIG. 2B). As a result, a driving force toward the objective side is applied to the lens unit 1, and the lens unit 1 moves against the pressing force of the bias spring 7. At this time, the amount of displacement of the lens unit 1 is adjusted by controlling the energizing current to the SMA actuator 3 and adjusting the amount of the moving force F1.

When the energization to the SMA actuator 3 is stopped (or the voltage is reduced to a predetermined value) and the SMA actuator 3 is cooled and returned to the martensite phase, the moving force F1 disappears, and the pressing force of the bias spring 7 The lens unit 1 returns to the home position along the optical axis AX direction. In this way, the lens unit 1 can be displaced along the optical axis AX direction by turning on and off the SMA actuator 3, and the moving force F1 can be controlled by controlling the current supplied to the SMA actuators 3a and 3b. The amount of displacement of the lens unit 1 can be adjusted by adjusting the amount of force.

Thus, according to the lens driving unit, the lens unit 1 can be favorably moved along the optical axis AX in accordance with the operation of the SMA actuator 3.

In the lens driving unit 100 of this embodiment, the temperature sensor 107 for detecting the temperature of the SMA actuator 3 itself or in the vicinity thereof is attached to the base member 4 so as to face the SMA actuator 3. A method of using the temperature information obtained by the temperature sensor 107 will be described later.

<1-1. General properties and assumptions of SMA>
As a preparation for explaining the details of the SMA actuator control apparatus 101 in this embodiment, the general properties of the physical characteristics of the SMA that are the premise of this embodiment and the circumstances that accompany it will be described.

3 to 6 are diagrams showing general properties of physical properties of the linear SMA having a substantially circular cross section. Among these, FIG. 3 is a diagram for explaining the characteristics of the drive response when the wire diameters (that is, the diameters of the cross sections) are different, and FIG. 3A shows the drive response when performing constant current drive. FIG. 3B shows drive response in step drive (servo).

When the SMA actuator is driven at a constant current, a constant current is continuously supplied from the start of current application, and the temperature of the SMA itself increases with time due to heat generated by the energization. However, as shown in FIG. 3A, when the wire diameters are different, for example, when three wire diameters D1, D2 and D3 having a relationship of wire diameter D1 <wire diameter D2 <wire diameter D3 are considered. The response when starting to supply a constant current from the zero current state is higher as the wire diameter is smaller, and the displacement responsiveness is increased as the wire diameter increases in the order of the wire diameter D1, the wire diameter D2, and the wire diameter D3. Go down. Thus, even if the current value is constant, the responsiveness differs because the volume, surface area, and electrical resistance value of SMA differ when the wire diameter is different.

Considering the wire diameter dependence of the SMA temperature change when the calorific value of the entire SMA is constant, first, the volume (heat capacity) of the SMA increases in proportion to the square of the wire diameter D. Become. The amount of heat released from the SMA to the outside increases in proportion to the surface area of the SMA, but the surface area is proportional to the wire diameter D. Further, the generated Joule heat is (the square of current I) × (resistance R), but the resistance R becomes smaller in proportion to the square of the wire diameter D.

Therefore, the temperature rise due to energization (joule heat / heat capacity) is inversely proportional to the fourth power of the wire diameter D, and the heat radiation from the surface is proportional to the wire diameter D. Then, even if the currents flowing through the SMA are the same value, if the wire diameter D is small, the effect of the temperature increase due to energization becomes large, greatly exceeding the heat dissipation. That is, the smaller the wire diameter D, the greater the Joule heat and the smaller the heat capacity, and the more likely the temperature rises. On the other hand, the heat accumulated in the SMA is less likely to dissipate because the surface area decreases. As a result, the smaller the SMA wire diameter (that is, the thinner the wire), the shorter the time required for temperature change and the faster the response speed. These properties are shown in FIG.

In addition, when constant current drive is performed, it takes a long time for the displacement of the driven object (lens) to settle, and the displacement also changes depending on conditions such as the ambient temperature. It is preferable to do. As is well known, the servo control is a method in which the amount of energization is feedback controlled and information is moved to a target displacement while acquiring information on the current displacement. Here, there is a method of providing a displacement sensor in order to obtain information on the deformation of the SMA. However, in the embodiment of the present invention, the resistance value of the SMA itself correlates with the deformation amount (expansion / contraction amount) of the SMA. The resistance value of SMA is detected by using this, and the resistance value is used as displacement information of SMA.

About this,
DR correlation: Correlation between “wire diameter-resistance value” (resistance value increases as wire diameter decreases),
RT correlation: Correlation between "resistance value-temperature" (resistance value decreases with increasing temperature in the temperature range where SMA contracts),
TX correlation: Correlation between “temperature-SMA expansion / contraction amount” (the higher the temperature, the larger the expansion / contraction amount),
Among them, if RT correlation and TX correlation are combined, the correlation of “resistance value−SMA expansion / contraction amount (lens displacement)” as shown in FIG. 6 can be specified. Therefore, by measuring the resistance value of SMA, the expansion / contraction of SMA The amount (lens displacement due to expansion and contraction of SMA) is obtained.

The amount of current supplied to the SMA by feedback control is determined by comparing the target displacement with the current displacement. In the case of proportional control, which is a simple control method, the energization amount is determined so as to be proportional to the difference between the target displacement and the current displacement. That is, the energization amount is calculated by multiplying the difference amount between the target displacement and the current displacement by a constant (gain).

Therefore, in order to optimize the response of the actuator, it is important to set an optimum gain in consideration of the response of SMA3. In general, if the gain is too low, the displacement speed becomes slow, and it takes a long time to reach the target displacement. If the gain is too high, the displacement speed increases, but overshoot occurs due to excessive response due to the phase delay of the feedback loop, and it takes a long time to settle to the target displacement. Therefore, a change in response due to the SMA wire diameter becomes a problem when performing this gain setting.

FIG. 3 (b) shows response characteristics when the target displacement P2 is step-driven from a state where the target displacement P1 is settled. Similar to FIG. 3A, in FIG. 3B, three cases of different wire diameters D1 <wire diameter D1 <wire diameter D2 <wire diameter D3 are considered. In this case, even if the gain is set so that the response at the wire diameter D2 is optimized, the response becomes slow at the thicker wire diameter D3, and the response becomes too high at the thinner wire diameter D1, resulting in overshoot. Will occur.

FIG. 4 is a diagram showing the relationship between the temperature-resistance value and the temperature-stretching amount of the SMA wire. These correspond to the RT correlation and TX correlation described above. A general characteristic curve is shown when the temperature is changed in a state where Ni-Ti SMA is stretched by applying a tension of about 200 MPa. In the process where the temperature changes from a low temperature region to a high temperature, the resistance value increases like the general metal below the As point, and the strain changes as the crystal phase starts to transform to the austenite phase near the As point. That is, the length of the wire contracts. When the temperature is further increased, the transformation does not shrink due to the complete transformation to the austenite phase near the Af point. In the process from As to Af, the resistance value decreases due to the crystal phase change and deformation. Further, in a temperature region exceeding Af, the resistance value increases with increasing temperature like a general metal.

Next, in the process of changing from the high temperature region to the low temperature, the resistance value and strain follow the same trajectory as the temperature increasing process at a temperature higher than the Ms point, but the crystal phase transforms into a martensite phase near the Ms point. The strain is stretched by the tension and starts to return to its original state. When the temperature is further lowered, transformation to the martensite phase is completed almost completely near the Mf point, and the original stretched state is restored. Further, in the process of Ms to Mf, the resistance value increases, and in the temperature region lower than Mf, the same trajectory as when the temperature rises is reversed. Although the transformation temperature varies depending on the composition ratio of Ni-Ti, when used as an energized actuator, for example, those with As: 80 ° C, Af: 85 ° C, Ms: 65 ° C, Mf: 60 ° C are used. .

FIG. 5 is a diagram illustrating the relationship between the temperature-resistance value and the temperature-lens displacement of the SMA used for driving the AF lens in the lens driving unit 100 of the embodiment. FIG. 5 shows a curve that does not include the high temperature side of the characteristic curve of FIG. 4, and shows a range that is actually used as a product. In the process of increasing the temperature from the low temperature region, the resistance value becomes maximum (hereinafter referred to as “maximum resistance value Rmax”) in the vicinity of the transformation to the austenite phase. The wire starts to shrink from here, but the lens does not move immediately because of the slack of the wire and the elastic deformation of each part. The resistance value at which the temperature increases and the actuator displacement starts to change is referred to as “displacement resistance value Rinf”.

Next, the lens starts to extend in the macro direction from the infinite end. As the temperature rises, the resistance value decreases as the lens moves in the macro direction. The resistance value when reaching the macro end is referred to as “macro end resistance value Rmcr”. On the contrary, in the process of lowering the temperature, the resistance value increases as the lens moves in an infinite direction.

Also, the resistance value (referred to as “radiation resistance value Rstart”) in a completely radiated state before energization varies depending on the ambient temperature (environment temperature or room temperature). Therefore, when calculating the wire diameter based on the resistance value in the heat dissipation state, it is desirable to perform correction based on the ambient temperature.

FIG. 6 is a characteristic curve of SMA resistance value-lens displacement used in the lens driving system 100. Here, the temperature rise process and the temperature decrease process have the same trajectory and the hysteresis disappears. For example, in Ni-Ti-Cu SMA in which Ni in Ni-Ti is replaced with Cu by a few percent, this hysteresis can be made very small. It has been known. As shown in FIG. 6, the resistance value R accompanying the lens displacement in the movable range of the lens is a range of “displacement resistance value Rinf <resistance value R <macro-edge resistance value Rmcr”, and in this range, the resistance value of the SMA. -Lens displacement has a substantially linear characteristic.

Based on the above background, the wire diameter information is used indirectly (first embodiment) or directly (second embodiment), and the energization parameter (typically feedback gain in the case of servo control) is used as the wire diameter. It is a characteristic matter of each embodiment corresponding to the technical idea of the present invention to realize the optimum control even if there is a variation in the wire diameter by setting the variable accordingly.

In the following, the details of each embodiment will be described.

<2. First Embodiment>
<2-1. Outline of SMA Actuator Control Device 101>
The SMA actuator control device based on the technical idea of the present invention described above controls the actuator using the shape restoring force due to the temperature change of the wire-like SMA 3. Specifically, energization to the SMA 3 is controlled by a PWM (pulse width modulation) method, and the value of the energization parameter to the SMA 3 for satisfying a predetermined energization reference condition can be varied according to the wire diameter D of the SMA 3. Set. Based on the set energization parameter, the control signal is changed according to the operation command value to the actuator, and energization control to the SMA 3 is performed.

FIG. 7 is a block diagram showing the configuration of the SMA actuator control apparatus 101 according to the first embodiment. The SMA actuator control apparatus 101 includes the mechanism system shown in FIGS. 1 and 2 in the lens driving system 100. It corresponds to a control system for controlling. As shown in FIG. 7, the SMA actuator 3 can be energized by the variable current source 106 from the power supply line PL side between the power supply line PL that supplies the power supply voltage V and the ground line GL. Here, the SMA actuator 3 corresponds to the SMA actuator 3 of the lens driving unit 100 shown in FIGS.

Both ends of the SMA actuator 3 is connected to the resistance value detecting section 102, the resistance value detecting section 102, Ohm's law by, detecting the resistance value R _SMA from the voltage V across the known current value I and the SMA actuator 3. Since the current value I becomes a substitute index in the one-to-one relationship with the voltage V across if known resistance value R _SMA, to detect the voltage V across, it a physical detecting the resistance value R _SMA Or mathematically equivalent. That is, the physical quantity detected by the resistance value detection unit 102 is not limited to the absolute resistance value _RSMA , but may be another quantity that serves as a substitute index for the resistance value _RSMA . More generally, a value representing the resistance value SMA (resistance expression value) may be detected by having a one-to-one relationship with the resistance value SMA. For this reason, the “resistance value” detected by the resistance value detection unit 102 of the present invention is used in a sense including not only the resistance value itself but also a resistance expression value such as a voltage.

Resistance R _SMA of the SMA actuator detected by the resistance value detecting section 102 is input to one input terminal of the comparator 103, the other input terminal of the comparator 103 target resistance Rp from the controller 104 Entered. Here, the resistance value R is detected instead of providing the displacement sensor by utilizing the above-described relationship between the SMA resistance value and the lens displacement (see FIG. 6). The comparison between the actual resistance value obtained by this detection and the target resistance value indirectly compares the current lens displacement value with the target lens displacement value. That is, the comparison unit 103 outputs the result of comparing the input values of the actually measured resistance value _RSMA and the target resistance value Rp to the energization control calculation unit 105. The ON / OFF control of the variable current source 106 for performing the PWM drive is possible according to the output result of the energization control calculation unit 105 (difference between the actually measured resistance value _RSMA and the target resistance value Rp).

Corresponding to the fact that the amount detected by the resistance value detection unit 102 is not limited to the resistance value _RSMA itself, but generally may be a “resistance value” including a resistance expression value, the target resistance value Rp is also generally May be a value expressing the target resistance value Rp by having a one-to-one relationship with the target resistance value Rp (a “target resistance value” including the target resistance expression value). Therefore, one of the signals input to each input terminal of the comparison unit 103 is a “resistance value” signal output from the resistance value detection unit 102, and the other is a “target resistance value” signal. Become.

<2-2. Driving current control to SMA>
Next, the energization waveform of SMA will be described. In this embodiment, the lens is driven by PWM control. Generally, a PWM waveform has two values, a peak value of a pulse (pulse amplitude) and a duty ratio (ratio of ON time per cycle of a pulse train). It depends on the parameters. The lens displacement drive in this embodiment is realized by changing the duty ratio and thereby increasing or decreasing the average energization amount to the SMA. The current value (pulse amplitude value) at the time of generating such a pulse train is obtained. Set in advance according to the wire diameter.

That is, as the initial setting when the power is turned on, “current setting” according to the wire diameter is once performed, and thereafter “duty ratio control” according to the target displacement of the lens for the AF operation is performed. For convenience, the latter will be described in order.

1. Duty ratio control In the example of the PWM waveform of FIG. 8, the duty ratio DA in the heat dissipation state A and the duty ratio DB in the heating state B are in a relationship of “duty ratio DA <duty ratio DB”. Further, the variable current source is set to have a constant current output, and the applied current Ip is constant. Therefore, the time average current (energization amount) is determined by the duty ratio, and the heating amount by energization is (state A) <(state B), so the SMA temperature is (state A) <(state B).

If the SMA temperature is within the movable range of the actuator, the SMA resistance value _RSMA is (state A)> (state B), and the current Ip is constant, so that the SMA terminal voltage is “ Voltage VA> voltage VB ”. Since the current Ip is a known value set in the variable current source, the SMA resistance value _RSMA is detected from the terminal voltages VA and VB in any state such as the heat dissipation state A and the heating state B by Ohm's law. be able to.

In this way, the resistance value _RSMA of the _SMA is detected and compared with the target resistance value Rp, feedback control is performed to increase or decrease the energization amount based on the duty ratio, thereby controlling the displacement of the actuator to the target position.

However, “the current Ip is constant” here means “constant without depending on the target displacement (command value) of the lens in the AF control”, and “the current Ip is variable according to the wire diameter D”. This is consistent with the following content:

2. Current value setting (initial setting by inspection energization)
On the other hand, when the current Ip for performing the duty ratio control is determined in advance according to the wire diameter D, the current adjustment signal SI (see FIG. 7) is adjusted with the duty ratio being constant. The current adjustment signal SI is a signal that specifies the value of the current Ip.

Since the average energization amount (current conversion) per unit time to the SMA 3 is the product: Ip × Dp (Dp is the duty ratio), the average energization is performed regardless of which of the current Ip value and the duty ratio Dp is changed. In this embodiment, the drive control to the target displacement is performed by duty ratio control, while the value of the current Ip, that is, the pulse amplitude is adjusted according to the wire diameter.

On the other hand, when setting the current Ip according to the wire diameter D in this embodiment, information (wire diameter information) related to the wire diameter D unique to the product of the lens driving unit 100 is required. What should be solved in the present invention is the setting of an appropriate control parameter according to the variation of the wire diameter D, so the “specification value (design value) of the wire diameter D” cannot be used as the wire diameter information. In the manufacturing process of each lens driving unit 100, data obtained by actually measuring the SMA wire diameter D inherent to the unit is used, or when the user uses the lens driving unit 100, the lens driving unit 100 There are two modes of the configuration in which the automatic setting reflecting the information of the wire diameter D is automatically performed within the 100.

This first embodiment employs the latter, and as will be described in detail later, a physical quantity having a specific relationship (correlation) with the wire diameter D is automatically measured in the lens driving unit, and based on the measurement result, “ “Set current Ip according to wire diameter D”.

Therefore, in the memory 108 built in the controller 104 in FIG. 7 in the first embodiment, a conversion table or a conversion formula (hereinafter referred to as “conversion information”) determined in advance based on the mutual relationship of physical quantities in FIG. (Generic name) is stored. The control circuit is configured to detect the resistance value RSMA of the _SMA 3 as a physical quantity corresponding to the wire diameter, and to feed it back to the energization amount to the _{SMA 3} . The significance and specific usage of the conversion information will be described later.

The temperature sensor 107 measures the temperature (environment temperature) of the SMA 3 or its surroundings, and the temperature value detected by the temperature sensor 107 is used for temperature compensation described later.

<2-3. Correlation between SMA3 wire diameter and its physical properties>
FIG. 9 is a block diagram for explaining the correlation between the wire diameter D of the SMA 3 and its physical characteristics. Here, the wire diameter of the SMA 3 is “wire diameter D”, the temperature of the SMA 3 detected by the temperature sensor 107 is “temperature T”, the resistance value of the SMA 3 is “resistance R”, and the voltage of the SMA 3 as the energization reference condition is “ Assuming that the current to the SMA 3 at which the voltage Vp ”and the terminal voltage of the SMA 3 become the voltage Vp is“ current Ip ”, the physical relationship between these factors is shown in FIG.

The gain of the feedback loop of PWM control depends on the current Ip. That is, when the duty ratio of the PWM waveform is changed in accordance with the difference between the target displacement and the current displacement, the larger the current Ip, the larger the amount of heat generation of the SMA 3 is, which corresponds to the larger gain of the feedback loop. Therefore, adjusting the gain according to the wire diameter D means that the magnitude of the current Ip is variably set according to the wire diameter D.

Specifically, by determining the value of the current Ip in each SMA actuator control device 101 so that the terminal voltage V of the SMA 3 becomes a predetermined value Vp, the influence of the wire diameter D can be set to the gain of the feedback loop of the PWM control. Can be imported automatically.

For example, when the wire diameter D is small, as shown in the step drive graph in FIG. 3, the response tends to be hypersensitive, but the resistance R increases as the wire diameter D decreases. Therefore, the current value Ip at which the terminal voltage V of the SMA 3 becomes the predetermined value Vp is determined as a smaller current value when the wire diameter D is small than when the wire diameter D is large. As a result, when the wire diameter D is small, the gain becomes small, and a sensitive response is suppressed. The reverse is true when the linear D is large.

Next, consider the effect of temperature T. If the resistivity ρ of SMA3 is a function dependent on temperature, it is written as resistivity ρ (T), and if the shape factor of SMA3 is a function dependent on the wire diameter D, it is written as shape factor F (D). As shown in FIG. 9, the resistance value R of the SMA can be expressed by the following equation (1) using the resistivity ρ (T) and the shape factor F (D).

R = ρ (T) / F (D) (1)
The “shape factor” mentioned here is a factor that generally changes according to the geometric shape and size of the SMA, but in this embodiment, the linear SMA 3 having a substantially circular cross section is used. Is the wire diameter D of SMA.

As shown in the equation (1), the resistance R is not only small when the wire diameter D is large and large when the wire diameter D is small, but is also restricted by the resistivity ρ, that is, the temperature T. . Therefore, the resistance R detected by the resistance value detection unit 102 reflects not only the wire diameter D but also the value of the temperature T.

Therefore, it is preferable to consider the influence of the temperature T in determining the current value Ip. Specifically, in the process of determining the current value Ip unique to the SMA actuator control apparatus 101, temperature compensation is performed in consideration of temperature information when determining the current value Ip. The specific method will be described later.

Based on the above principle, the current adjustment signal SI is generated by the controller 104 so as to set the determined current I = Ip (energization parameter) in the variable current source 106, and actual PWM control is performed.

<2-4. Basic Operation of SMA Actuator Control Device 101>
Hereinafter, the operation of the SMA actuator control device 101 in the lens driving unit 100 will be described with reference to the flowchart of FIG. 10, taking the case where the lens driving unit 100 is incorporated in a mobile phone as an example. The following functions are realized by executing a program installed in advance in the microcomputer in the controller 104, but these functions may be realized by a dedicated hardware configuration.

First, in response to an initial operation in which the user turns on the power supply of the mobile phone or the camera mode, the power supply to the SMA actuator control device 101 is turned on, this operation flow is started, and the process proceeds to step S1.

After the power is turned on, “inspection energization” is first performed on the SMA 3. The “inspection energization” referred to here is an energization process for acquiring information related to the wire diameter D of the SMA 3 in order to determine the current value Ip of the PWM pulse train in accordance with the wire diameter D of the SMA 3. Specifically, in step S1, an initial current value I0 is set in the current adjustment signal SI (FIG. 7), and a minimum duty ratio D0 is set in the energization control calculation unit 105. Since the pulse cycle (frequency) is fixed in PWM control, setting the minimum duty ratio D0 is equivalent to setting the minimum pulse width Pw0.

The initial current value I0 and the minimum duty ratio D0 are stored in the memory 108 in advance, and are common values that do not depend on the wire diameter D of each SMA actuator controller 101. This minimum duty waveform is set by setting the minimum duty ratio D0 to a value in a range corresponding to about 2 to 3%, for example, by converting it to an ON / OFF period ratio, so that only a very short time is required within the pulse repetition period. The waveform is set to turn on the current. The initial current value I0 is also set to a current value smaller than the current range (design range set as the current Ip) when the SMA 3 is actually driven by PWM control.

The reason why the initial current value I0 and the minimum duty ratio D0 are made small in this way is that the heat generation of the SMA 3 is small in the energization of inspection, and the resistance value of the temperature-resistance value characteristic curve of FIG. The SMA 3 is intended to operate in a low temperature region RL that increases monotonically. This is because, in the low temperature region RL, the temperature-resistance value characteristic curve has no hysteresis and is a linear characteristic curve, so that the repetitive loop described later for obtaining the wire diameter information has high convergence. . This also has the advantage of suppressing the power consumption of the mobile phone due to the energization of inspection.

The minimum duty ratio D0 (and therefore the minimum pulse width Pw0) set in step S1 is always constant before the PWM drive for actual photographing is started (up to the step S7).

In step S2, a current waveform having the initial current value I0 and the minimum duty ratio D0 set in step S1 is supplied to SMA3.

In step S3, the target voltage Vp of SMA3 is determined. Details are as follows.

In step S4 and later described below, a current value Ip is obtained such that the terminal voltage V of the SMA 3 detected by the resistance value detection unit 102 matches the predetermined voltage Vp. This is equivalent to specifying the current value Ip according to the value of the resistance R of the SMA 3. However, since the resistance R of the SMA 3 is also affected by the temperature T, temperature compensation is performed in consideration of the influence of the temperature T during the energization of the inspection in selecting what voltage value is used as the voltage Vp.

Specifically, for each of various values of temperature T (T = T1, T2, T3,...), The target voltage Vp of SMA3 such that the relationship between the resistance value R of SMA3 and the wire diameter D is substantially the same. The value of (Vp = V1, V2, V3...) Is experimentally obtained in advance, and the correlation data is stored in the memory 108 in a table format (see FIG. 13). Hereinafter, such a table is referred to as a “temperature / target voltage table”. This is because the relationship between the resistance R and the wire diameter D is quantitatively different when the temperature T is different in the above-described equation (1), and the difference is expressed in a table format. .

When the numerical relationship in the temperature / target voltage table is expressed by an approximate expression, information specifying the conversion expression (approximation function) is stored in the memory 108, and the temperature variable of the conversion expression is the temperature T.sub.T. And the value of the target voltage Vp may be obtained. Hereinafter, such a conversion formula and the temperature / target voltage table are collectively referred to as “T / V correspondence information”.

Then, the value of the target voltage Vp corresponding to the temperature T detected by the temperature sensor 107 is read from the temperature / target voltage table, and is set as the value of the target voltage Vp (step S3 in FIG. 10).

In the energization of the inspection, only the minute current I0 is allowed to flow through the SMA 3. Therefore, the temperature of the SMA 3 is maintained approximately equal to the environmental temperature, and the temperature T detected by the temperature sensor 107 approximates both the temperature of the SMA 3 and the environmental temperature. Give it. Further, during the period of energization of inspection, the SMA 3 also maintains the resistance value R in the almost complete heat dissipation state. Therefore, the temperature of the SMA 3 does not change suddenly during the energization of the inspection, and the resistance R of the SMA 3 shows a good correlation with the wire diameter D of the SMA 3 by the above temperature compensation.

In this way, the value of the target voltage Vp as the energization reference condition in PWM control is determined in a form including temperature compensation.

The next steps S4 to S6 are processes for determining the value of the energization parameter (optimum current Ip) based on the energization reference condition (target voltage Vp) thus determined. As shown in step S2, energization to the SMA 3 is performed with the initial current value I0 and the minimum duty ratio D0. Of these, the initial current value I0 is set as an initial value, but the minimum duty ratio D0 is set. Is unchanged over the period of steps S4 to S6.

First, in step S4, the resistance value detection unit 102 detects the SMA terminal voltage V.

In step S5, the controller 104 determines whether or not the SMA terminal voltage V detected in step S4 is smaller than the value of the target voltage Vp determined in step S3. If the SMA terminal voltage V is smaller than the target voltage Vp (determination reference value), the process proceeds to step S6. If the SMA terminal voltage V indicates a value equal to or higher than the target voltage Vp, the process proceeds to step S7.

In step S6, a current value larger than the current applied in step S3 by a predetermined increment is set, and by returning to step S4, inspection energization to SMA3 is continued. If the predetermined increase width of the current here is set to be sufficiently small, the current value increases in small increments every time step S6 is passed.

When it is determined in step S5 that the SMA terminal voltage V is equal to or higher than the target voltage Vp, the SMA terminal voltage V substantially satisfies the energization reference condition (voltage V = target voltage Vp). Then, the value of the energization parameter (current Ip) at that time is set as the PWM current value in actual driving of the actuator (step S7).

As described above, the value of the energization parameter (current Ip) is determined on the basis of the resistance value R of the SMA 3 detected by the resistance value detection unit 102 through the inspection energization from step S1 to step S5. Therefore, when the resistance value R of the SMA 3 is correlated with the wire diameter D of the SMA, it means that the value of the energization parameter (current Ip) is determined as a value reflecting the wire diameter D of the SMA 3 (FIG. 9). In other words, the PWM current value Ip is determined according to the variation in the wire diameter D from the inspection energization from step S1 to step S5.

In step S8, the current value Ip is set in the variable current source 106, and a control signal that changes in accordance with the lens displacement operation command value is given to the energization control calculation unit 105, and the PWM drive energization of the SMA actuator 3 is performed. Is started. The duty ratio of the PWM pulse train changes according to the operation command value to the SMA actuator 3, but the current value Ip is kept constant. In step S9, such servo control is continued based on a command from a host microcomputer (not shown).

In step S10, if the PWM current driving is continued, the process returns to step S9, and if the PWM current driving is interrupted, the operation flow is ended.

The above configuration and operation can be generally expressed as a set of function implementation units as follows.

First, the variable current source 106 functions as an energization unit that energizes the SMA 3.

By executing the program of steps S1 to S7 (FIG. 10) in the controller 104, the assembly of the elements 102 to 108 in FIG. 7 sets the value of the energization current to the SMA 3 for satisfying a predetermined energization standard condition. It is determined according to the wire diameter D of the SMA 3 and functions as a current setting unit that sets the value of the energization current in the memory 108.

The value of the energization current set in the memory 108 is variable according to the wire diameter D of the SMA 3, and the value of the energization current is a basis for generating the current adjustment signal SI in actual control.

The assembly of the elements 102 to 106 and 108 in FIG. 7 is a control signal (FIG. 7) that changes in accordance with the operation command value to the actuator with reference to the energizing current set as described above in the actual control stage. 7, the current adjustment signal SI and the ON / OFF signal) is supplied to the variable current source 106 serving as an energization unit, and functions as an energization control unit that controls energization of the SMA.

More specifically, in the actuator actual control after the value of the energization current is determined, the resistance value detection unit 102 functions as a resistance value detection unit that detects a resistance value as a value representing the resistance of the SMA 3. The comparison unit 103 functions as a comparison unit that compares the resistance value detected by the resistance value detection unit with the target resistance value as a value representing the target resistance value.

When the SMA is deformed into a desired shape, the energization control unit sets the average energization current to the SMA so that the difference between the resistance value signal and the target resistance value signal corresponding to the SMA operation command value is small. The feedback control to be controlled is executed based on the output signal of the comparison unit 103.

In particular, in this embodiment, in the functional stage as the current setting unit, the controller 104 executes the program of steps S1 and S2 in FIG. 10 and uses the energization control calculation unit 105 while also using the variable current source 106 (energization unit). To function as a test energization control unit that performs test energization to the SMA 3.

The controller 104 repeats step S6 of FIG. 10 and executes the program of steps S5 and S7 to operate the elements 102 to 106 and 108, and based on the result of the inspection energization to the SMA 3 obtained from the comparison unit 103. Thus, it functions as an inspection processing unit that determines the value of the energization current.

The above energization control unit uses the value of the energization current determined by the inspection energization in the actual driving of the actuator.

The inspection processing unit is a unit that determines the value of the energization current based on the resistance value of the SMA detected by the inspection energization, and the resistance value of the SMA 3 correlates with the wire diameter of the shape memory alloy. Thus, the value of the energization current is determined as a value reflecting the wire diameter D of the SMA 3.

The temperature sensor 107 is used as a temperature specifying unit that specifies the temperature of the SMA 3 or its surroundings. Then, the controller 104 executes a program for determining the target voltage Vp in step S3, thereby changing the energization reference condition according to the temperature specified by the temperature specifying unit, and temperature compensation when determining the value of the energization current. It functions as a temperature compensation unit that performs

As described above, according to the SMA actuator control apparatus 101 according to the first embodiment, the current setting unit variably sets the energization parameter (current Ip) according to the wire diameter D, so that the wire diameter is changed in the energization control unit. Since energization control according to D is possible, even if the wire diameter D of the SMA varies, the responsiveness of the actuator is improved by stable optimum control, and the static stabilization is also speeded up.

Also, the energization parameter can be determined internally by the inspection processing unit based on the result of the inspection energization executed by the inspection energization control unit at an appropriate time such as immediately after startup. For this reason, the process of measuring the wire diameter D in advance and storing it in the memory 108 in the manufacturing process of the apparatus can be omitted.

Since temperature compensation by the temperature compensation unit is also possible based on the T / V correspondence information, the current setting unit can more appropriately determine the energization parameter regardless of the temperature during the energization of the inspection.

<3. Second Embodiment>
<3-1. Outline and Configuration of SMA Actuator Control Device 101A>
FIG. 11 is a block diagram of an SMA actuator control apparatus 101A according to the second embodiment of the present invention. This SMA actuator control device 101A is also used in combination with the mechanism part of the lens driving unit 100 shown in FIGS. 1 and 2, and can be incorporated in a mobile phone or the like.

In the second embodiment, the current setting unit stores in advance the value of the wire diameter information corresponding to the wire diameter D of the SMA by the wire diameter information storage unit, and based on the value of the wire diameter information by the current value determination unit. This is different from the first embodiment in that the value of the energization parameter is determined. Further, in the second embodiment, compared with the first embodiment, the hardware is the same as the configuration of FIG. 7, and the functions are almost the same. Therefore, in the SMA actuator control apparatus 101A of FIG. 11 according to the second embodiment, the same parts as those of the SMA actuator control apparatus 101 according to the first embodiment are denoted by the same reference numerals and the following description is omitted. In addition, only differences from the SMA actuator control apparatus 101 according to the first embodiment will be mainly described.

Referring to FIG. 11, controller 104 includes a memory 108A. In the memory 108A, as wire diameter information,
(1) The value of the wire diameter D measured in advance at the manufacturing factory, and
(2) As illustrated in FIG. 14, the correspondence relationship between the value of the wire diameter D and the energization parameter Ip is expressed, and a table or conversion formula (when converting the wire diameter D into the energization parameter Ip ( (Hereinafter collectively referred to as “D / I correspondence information”) is stored in the memory 108 in advance.

Among these pieces of wire diameter information, the value of the wire diameter D is unique to the SMA actuator control device 101. On the other hand, the D / I correspondence information is information common to each SMA actuator control device 101. That is, although the wire diameter D varies depending on the product of the control device 101, the D / I correspondence information on what current value Ip is set according to the value of the wire diameter D is common to each control device 101. Prepared and stored as a thing.

On the other hand, the wire diameter D is measured at the manufacturing factory of the SMA actuator control device 101, and the value of the energization parameter (current value Ip) specific to the control device 101 is determined at the factory accordingly. There is a method of storing only the current value Ip, but if the common D / I correspondence information and the individual wire diameter D are stored as in the second embodiment, for example, When new D / I correspondence information with higher accuracy is developed, the new D / I correspondence information can be upgraded and stored in the memory 108A as firmware.

<3-2. Basic Operation of SMA Actuator Control Device 101A>
FIG. 12 is a flowchart showing processing operations in the SMA actuator control apparatus 101A. Hereinafter, the processing operation will be described with reference to the flowchart of FIG.

In response to the user turning on the camera mode of the mobile phone, the power supply to the SMA actuator control device 101 is turned on, and this operation flow is started.

In step ST1, the value of the wire diameter information corresponding to the wire diameter D measured in advance of SMA is read from the memory 108A and acquired.

In step ST2, the value of the wire diameter D acquired in step ST1 is converted into the value of the energization parameter Ip using the D / I correspondence information. The conversion unit directly converts the wire diameter D of the SMA 3 stored in advance into the energization parameter (optimum current Ip).

Subsequent steps ST3 to ST5 are the same as steps S8 to S10 in the first embodiment.

Of the function realization unit according to the second embodiment, the part different from the function realization unit in the first embodiment is as follows.

The current setting unit includes a memory 108 as a wire diameter information storage unit that stores a value of wire diameter information corresponding to the wire diameter D of the SMA 3.

The controller 104 functions as a current value determination unit that determines the value of the energization current based on the value of the wire diameter information by executing the program steps of steps ST1 and ST2 of FIG.

Then, the controller 104 functions as a conversion unit that converts the value of the wire diameter into the value of the energization current using the table of FIG. 14 stored in advance in the memory 108, which functions as a current value determination unit. Part of

As described above, also in the SMA actuator control apparatus 101A according to the second embodiment, the energization control according to the wire diameter D can be performed by setting the energization parameter (current Ip) variably according to the wire diameter D. Therefore, even if the wire diameter D of the SMA varies, the responsiveness of the actuator is improved by the stable optimum control, and the stabilization speed is increased.

In the second embodiment, since the wire diameter D measured at the manufacturing factory or the like is stored in advance in the apparatus as the wire diameter information, it can be read and used when the actuator is driven. It is possible to shorten the control time by simplifying the internal processing for determining the energization parameter.

On the contrary, compared with the second embodiment, in the first embodiment, it is not necessary to measure and store the wire diameter D in advance for each SMA actuator control device 101. Therefore, the manufacturing process of the SMA actuator control device 101 is as follows. This is simpler than the SMA actuator control apparatus 101A of the second embodiment.

<4. Modification>
<4-1. First Modification>
As mentioned above, although embodiment of this invention has been described, this invention is not limited to the said embodiment, A various deformation | transformation is possible.

The temperature compensation by the temperature compensation unit described in the first embodiment can be realized without providing a temperature sensor in the temperature specifying unit. In this case, the actual measurement of the temperature SMA3 or its surrounding temperature T is substituted with the actual measurement of the resistance value R of the SMA3.

For example, as shown in FIG. 15, the resistance value R of the SMA 3 corresponding to each set of values of the temperature T is experimentally determined in advance, and the table 108 is stored in the memory 108 of the SMA actuator controller 101. Alternatively, it is stored as a conversion formula (hereinafter “T / R correspondence information”).

Although the resistance R depends on the temperature T and the wire diameter D, since the value of the wire diameter D itself is not stored in the aspect as in the first embodiment, the wire diameter when the T / R correspondence information is created. As D, for example, a wire diameter as a design value of SMA3 is assumed. Then, when the SMA actuator control device 101 is activated, a predetermined minute current is passed through the SMA 3, the SMA terminal voltage V at that time is detected, and the value of the resistance R of the SMA 3 is calculated by R = V / I. And the value of the temperature T corresponding to the value of the resistance R is estimated using the T / R correspondence information.

Similar to the first embodiment of FIG. 13, the current setting unit can store the resistance value R for each temperature T in the memory in the same manner as in the first embodiment, so that the current setting unit responds to the specified temperature T. The resistance value R is selected, and the current Ip corresponding to the resistance value R is determined by inspection energization by the inspection energization control unit.

That is, in this modification, the resistance value detection unit detects the resistance value R of the SMA 3 as a substitute index of the temperature T, and the temperature compensation unit changes the energization reference condition using the resistance value R, thereby This means that temperature compensation is performed when determining the value.

In other words, in this modification, the temperature specifying unit used when performing the temperature compensation when determining the value of the energization current detects the resistance value detection unit 102 and the resistance value of the SMA 3 as a temperature substitute index. It is functioning as a resistance value detection unit.

Thus, temperature compensation without using a temperature sensor is also possible.

<4-2. Second Modification>
In the second embodiment, the value of the wire diameter D itself is stored by the wire diameter information storage unit, but may be a value of another physical quantity that reflects the wire diameter D. For example, the resistance R of the SMA 3 may be measured in advance at a device manufacturing factory and used as a substitute index for the wire diameter D. At this time, a correspondence table (FIG. 16) listing appropriate current values Ip corresponding to various values of the resistance R is created in advance by the wire diameter information storage unit and stored in the memory 108A. The conversion unit in the determination unit uses the correspondence table to convert the current Ip as the energization parameter.

In this case, the controller 104 functions as a conversion unit that performs this conversion in the program step for converting the resistance value of the SMA 3 into the value of the energizing current while using the table of FIG. 16 stored in the memory 108 in advance. This constitutes a part of the current value determination unit.

In this case, temperature compensation is also possible. That is, the wire diameter information storage unit also measures the SMA 3 or the temperature T around it when the resistance R of the SMA 3 is measured in advance at the device manufacturing factory. Then, the values of the resistance R and the temperature T are stored in the memory 108A.

In this case, in the memory 105A, as shown in FIG. 17, a correspondence table (generally “TR / I” which lists values of appropriate currents Ip corresponding to respective sets of values of the resistance R and the temperature T). Correspondence information ") is created and stored in advance. Then, the value of the current Ip corresponding to the resistance R and the temperature T is read and set as an energization parameter. Here, since the information of the temperature T at the time of measuring the resistance R is obtained, the resistance R is a substitute index of the wire diameter D.

When viewed as a function implementation unit, the controller 104 uses the table of FIG. 17 stored in advance in the memory 108 by the wire diameter information storage unit, and sets the resistance value and temperature by the conversion unit in the current value determination unit. Is converted into a value of the energizing current, thereby functioning as a part for performing temperature compensation when determining the value of the energizing current.

<4-3. Other variations>
In each of the above embodiments, the energization control unit adjusts the energization current according to the wire diameter D of the SMA by adjusting the current value Ip (that is, the pulse amplitude). It may be performed by adjusting (duty ratio).

In the above embodiment, the servo control (feedback control) using the PWM control is described as an example. However, the present invention is not limited to this, and a continuous current (non-pulse type current) is applied to the SMA to generate heat. The present invention can also be applied to the case of the system and the open control system. Among these, in the case of the continuous current method, since there is no concept of the duty ratio as in the case of PWM control, the continuous current value (continuous current reference value) corresponding to the current value Ip in the above embodiment is set to SMA. Adjust according to the wire diameter D.

The current setting unit in the above embodiment determines the energization current Ip based only on the wire diameter D. Although the influence on the control is small, other variation factors such as SMA initial tension and bias spring force There are also variations in elastic properties. Therefore, in addition to the linear D, depending on the variation value for each individual regarding these elastic characteristics (more generally, characteristic quantities including various mechanical characteristic quantities that define the responsiveness of the SMA), The energization current may be determined.

The inspection energization by the inspection energization control unit in the first embodiment may be performed only at the initial setting when the camera unit incorporating the SMA actuator control device 101 is activated for the first time, or is performed at each activation of the camera unit. Also good. Further, in the maintenance mode, it may be executed even in response to a predetermined operation at an arbitrary time.

The SMA actuator control device of the present invention can be applied not only to a lens drive unit but also to a drive unit of various optical components such as a minute mirror and a minute prism.

The method for determining the target voltage Vp in the first embodiment is not limited to the above method. For example, a correspondence table listing appropriate resistances R and temperatures T corresponding to the value of the wire diameter D, or a conversion formula (hereinafter referred to as “D / RT correspondence information”), and a wire diameter D A table or conversion equation (hereinafter referred to as “D / Vp correspondence information”) that can be used when converting the voltage to the target voltage Vp is created and stored in the memory 108 in advance. Then, based on the temperature T of the SMA specified by the temperature specifying unit and the resistance R detected by the resistance value detecting unit by inspection energization, the wire diameter D is estimated from the D / RT correspondence information, and the estimated line The target voltage Vp may be determined from the diameter D from the D / Vp correspondence information.

DESCRIPTION OF SYMBOLS 1 Lens unit 2 Lever member 2a Displacement input part 2b Displacement output part 3 Shape memory alloy (SMA) actuator 4

Base member

6a, 6b Parallel leaf spring 8 Support leg 8a Lever support part 10 Imaging lens 100

Lens drive unit

101, 101A SMA actuator Control device 102 Resistance value detection unit 103 Comparison unit 104 Controller 105 Energization control calculation unit 106 Variable current source 107 Temperature sensor

Claims

A shape memory alloy actuator controller for controlling an actuator using a shape restoring force due to a temperature change of a wire shape memory alloy,
An energization section for energizing the shape memory alloy;
A current setting unit that variably sets a value of an energization current to the shape memory alloy for satisfying a predetermined energization reference condition according to a wire diameter of the shape memory alloy;
An energization control unit that controls the energization of the shape memory alloy by giving the energization unit a control signal that changes according to an operation command value to the actuator with respect to the energization current;
A shape memory alloy actuator control device comprising:
The shape memory alloy actuator control device according to claim 1,
The current setting unit is
An inspection energization control unit that controls the energization unit to perform inspection energization to the shape memory alloy;
Based on the result of the inspection energization to the shape memory alloy, an inspection processing unit that determines the value of the energization current,
With
The shape memory alloy actuator control device, wherein the energization control unit uses the value of the energization current determined by the inspection energization in actual driving of the actuator.
The shape memory alloy actuator control device according to claim 2,
The inspection energization is performed by flowing a current smaller than the current range in actual driving of the actuator through the shape memory alloy,
The shape memory alloy actuator control device, wherein the inspection processing unit determines the value of the energization current based on the energization result with the small current.
The shape memory alloy actuator control device according to claim 2 or 3,
The inspection processing unit is a unit that determines a value of the energization current based on a resistance value of the shape memory alloy detected by the inspection energization,
The resistance value of the shape memory alloy is correlated with the wire diameter of the shape memory alloy, whereby the value of the energizing current is determined as a value reflecting the wire diameter of the shape memory alloy. Shape memory alloy actuator controller.
A shape memory alloy actuator control device according to any one of claims 2 to 4,
A temperature specifying part for specifying the shape memory alloy or its surrounding temperature;
A temperature compensation unit that performs temperature compensation when determining the value of the energization current by changing the energization reference condition according to the temperature identified by the temperature identification unit;
The shape memory alloy actuator control device further comprising:
The shape memory alloy actuator control device according to claim 5,
The temperature specifying unit is
A temperature sensor disposed in the vicinity of the shape memory alloy;
With
The shape memory alloy actuator controller according to claim 1, wherein the temperature compensation unit performs the temperature compensation according to a temperature detected by the temperature sensor.
The shape memory alloy actuator control device according to claim 5,
The temperature specifying unit is
A resistance value detecting unit for detecting a resistance value of the shape memory alloy as a substitute index of the temperature;
With
A shape memory alloy actuator control device that performs temperature compensation when determining the value of the energization current by changing the energization reference condition using the resistance value as a substitute index of the temperature.
The shape memory alloy actuator control device according to claim 1,
The current setting unit is
A wire diameter information storage unit for storing a value of wire diameter information corresponding to the wire diameter of the shape memory alloy;
Based on the value of the wire diameter information, a current value determination unit that determines the value of the energization current;
A shape memory alloy actuator control device comprising:
The shape memory alloy actuator control device according to claim 8,
The wire diameter information is a wire diameter of the shape memory alloy measured in advance,
The current value determining unit
A conversion unit for converting the value of the wire diameter stored in the wire diameter information storage unit into the value of the energization current;
A shape memory alloy actuator control device comprising:
The shape memory alloy actuator control device according to claim 8,
The wire diameter information storage unit stores a resistance value of the shape memory alloy,
The current value determining unit
A conversion unit that converts the resistance value into a value of the energization current;
With
A shape memory alloy actuator control device that determines the value of the energization current based on a conversion result of the conversion unit.
The shape memory alloy actuator control device according to claim 10,
The wire diameter information storage unit stores the temperature when the resistance value of the shape memory alloy is measured together with the resistance value,
A shape memory alloy actuator control characterized in that the conversion unit performs temperature compensation when determining the value of the energizing current by converting the set of the resistance value and the temperature into the value of the energizing current. apparatus.
A shape memory alloy actuator control device according to any one of claims 1 to 11,
A resistance value detection unit for detecting a resistance value as a value representing the resistance of the shape memory alloy;
A comparison unit that compares the resistance value detected by the resistance value detection unit with a target resistance value as a value representing the target resistance value;
With
The energization control unit
When the shape memory alloy is deformed into a desired shape, the shape memory alloy is reduced so that a difference between the resistance value signal obtained by the resistance value detection unit and the target resistance value signal is reduced. A shape memory alloy actuator controller that controls an average energization current.
A shape memory alloy actuator control device according to any one of claims 1 to 12,
The shape memory alloy actuator control device, wherein the power supply control unit performs current control of the shape memory alloy by a PWM method, and changes at least one of a pulse amplitude and a pulse width to the shape memory alloy.
An actuator that drives a predetermined optical component using a shape restoring force due to a temperature change of a wire-shaped shape memory alloy;
A shape memory alloy actuator control device according to any one of claims 1 to 13,
An optical component driving unit comprising: