SMA motor control method, related device and product

Abstract

The embodiment of the invention provides a control method of an SMA motor, a related device and a product, relates to the technical field of camera shooting, and aims to prolong the service life of the SMA motor. The SMA motor can drive the lens to move along the first direction and the second direction. The first direction is parallel to the lens focusing direction, and the second direction intersects with the first direction. The control method includes controlling the SMA motor to move a first travel value in a first direction. An instruction to instruct the SMA motor to move a second travel value in a second direction is received. If the first stroke value is equal to 0 and the second stroke value is larger than the first preset value, the SMA motor is controlled to move by the first preset value in the second direction. If the first stroke value is larger than 0 and the second stroke value is larger than a second preset value, the SMA motor is controlled to move by a second preset value in the second direction. The second preset value is smaller than the first preset value. According to the embodiment of the invention, on the basis of the focusing stroke of the motor, the optical anti-vibration stroke is limited, excessive driving of the SMA wire is avoided, and the service life of the motor is prolonged.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of camera technology, and in particular to a control method, related devices and products of an SMA motor. Background Art

[0002] Camera modules of various electronic devices are constantly updated to meet people's growing demand for camera quality of electronic devices. For example, electronic products such as smartphones and tablets need to consider the need for thinness and lightness of products, as well as the need to ensure camera quality. Obviously, it is difficult to take these needs into account by simply increasing the size of the sensor and the photosensitive area. For this reason, some electronic devices have introduced optical image stabilization (OIS) technology, which controls the movement of the lens to compensate for the shake of the device and the lens, thereby correcting the optical axis offset. This can avoid image blur caused by device shaking during the operation of the camera module, and effectively improve the camera quality of electronic devices.

[0003] Shape memory alloys (SMA) motors have many advantages such as large load capacity, small size, no magnetic interference and low cost, so they are widely used in camera modules of many electronic devices to control the lens, which can not only complete the automatic focus (AF) of the lens, but also achieve excellent optical image stabilization (OIS) compensation effect. However, SMA motors use extremely fine SMA wires to drive the lens, and SMA wires are easily affected by various factors such as materials and processes. After the SMA motor has been used for a period of time, the SMA wire is prone to breakage, causing the SMA motor to fail, affecting the normal optical image stabilization and focusing of the electronic equipment.

[0004] Therefore, how to extend the service life of the SMA motor in the camera module is a problem that needs to be solved urgently by technicians. Summary of the invention

[0005] The embodiments of the present application provide a control method, related devices and products of an SMA motor, the main purpose of which is to extend the service life of the SMA motor in a camera module.

[0006] In order to achieve the above purpose, the embodiment of the present application adopts the following technical solution:

[0007] In a first aspect, an embodiment of the present application provides a control method for a shape memory alloy SMA motor, wherein the SMA motor is configured to be able to drive a lens to move along a first direction and a second direction. The first direction is parallel to the focusing direction of the lens, and the second direction intersects with the first direction. The above control method includes: controlling the SMA motor to move a first stroke value along the first direction. Receiving an instruction instructing the SMA motor to move a second stroke value along the second direction. When the first stroke value is equal to 0 and the second stroke value is greater than a first preset value, the SMA motor is controlled to move the first preset value along the second direction. When the first stroke value is greater than 0 and the second stroke value is greater than the second preset value, the SMA motor is controlled to move the second preset value along the second direction. Wherein, the second preset value is less than the first preset value.

[0008] Through the above-mentioned embodiments, the SMA motor can drive the lens to move in a first direction parallel to the focusing direction of the lens to control the focus of the lens. The SMA motor can also drive the lens to move in a second direction intersecting with the focusing direction of the lens to control the lens to perform anti-shake compensation for the instantaneous displacement that occurs. In addition, the movement of the SMA motor is achieved by contracting a portion of the SMA wire in the SMA motor when it is powered on and stretching the remaining portion of the SMA when it is powered off. When the first stroke value of the SMA motor moving in the first direction is 0, the first preset value is the maximum distance that the SMA motor can move in the second direction and the SMA wire is not prone to fatigue failure, which can maximize the optical anti-shake compensation of the lens. When the first stroke value of the SMA motor moving along the first direction is greater than 0, the second preset value is the maximum distance that the SMA motor can move along the second direction. The second preset value is reduced compared to the first preset value, which can not only ensure the effect of optical image stabilization compensation for the lens, but also avoid excessive stress (such as contraction stress or tensile stress) on the SMA wire when the SMA motor moves along the first direction and the second direction, and avoid excessive deformation of the SMA wire (such as excessive contraction or stretching), thereby reducing the probability of SMA wire breakage and effectively extending the service life of the SMA motor in the camera module.

[0009] In combination with the first aspect, in a possible implementation, the SMA motor includes a first SMA wire and a second SMA wire. The step of controlling the SMA motor to move a first preset value along the second direction includes: transmitting a first current to the first SMA wire to control the first SMA wire to contract. Transmitting a second current to the second SMA wire to control the second SMA wire to contract until the SMA motor moves the first preset value along the second direction. Thus, by energizing at least two SMA wires in the SMA motor, the SMA motor can be controlled to move along the second direction.

[0010] The step of controlling the SMA motor to move the second preset value in the second direction includes: transmitting a third current to the first SMA wire to control the first SMA wire to contract. Transmitting a fourth current to the second SMA wire to control the second SMA wire to contract until the SMA motor moves the second preset value in the second direction. The first current is greater than the third current, or the second current is greater than the fourth current. In this implementation, when the first stroke value of the SMA motor moving in the first direction is greater than 0, the upper threshold of the current transmitted to at least one SMA wire is reduced. If the instantaneous displacement of the lens exceeds the second preset value, the current transmitted to at least one SMA wire is the lowered upper threshold of the current, so that the SMA motor can be controlled to move the second preset value in the second direction.

[0011] In combination with the first aspect, in a possible implementation, if the first stroke value is the first stroke sub-value, the second preset value is the first preset sub-value. If the first stroke value is the second stroke sub-value, the second preset value is the second preset sub-value. The first stroke sub-value is greater than the second stroke sub-value, and the first preset sub-value is less than the second preset sub-value. In this implementation, the corresponding second preset value can be determined according to the size of the first stroke value of the SMA motor moving along the first direction. As the first stroke value increases, the second preset value decreases accordingly, or there is a negative correlation between the second preset value and the first stroke value, so that when the SMA motor moves in both the first direction and the second direction, it can not only avoid excessive tensile stress on the SMA wire, but also ensure the effect of optical image stabilization compensation for the lens.

[0012] In combination with the first aspect, in a possible implementation, there is an inverse linear relationship between the second preset value and the first stroke value. Thus, the second preset value is changed linearly based on the change of the first stroke value, and further, under different first stroke values, the tensile stress on the SMA wire can be kept within a reasonable range, and the effect of optical image stabilization compensation for the lens can be guaranteed, thereby taking into account both the life of the SMA motor and the effect of optical image stabilization compensation for the lens.

[0013] In combination with the first aspect, in a possible implementation, the second preset value also includes a third preset sub-value. The first stroke value is equal to the focus stroke threshold, and the second stroke value is greater than the third preset sub-value, and the SMA motor is controlled to move the third preset sub-value along the second direction. The ratio between the third preset sub-value and the first preset value is not less than 40% and not greater than 70%. In this implementation, when the first stroke value reaches the maximum, the tensile stress on the SMA wire along the first direction is the maximum, and the third preset sub-value corresponding to the first stroke value is the minimum value of the second preset value. This implementation sets the minimum value of the second preset value to 40% to 70% of the first preset value, which can further take into account the life of the SMA motor and the effect of lens optical image stabilization compensation in extreme focusing conditions.

[0014] In combination with the first aspect, in a possible implementation, the first stroke value is greater than 0, and the second stroke value is greater than the second preset value. The above-mentioned step of controlling the SMA motor to move the second preset value along the second direction includes: when the first stroke value is greater than 0, determining the focus stroke interval in which the first stroke value is located. Determine the second preset value corresponding to the focus stroke interval. Determine whether the second stroke value is greater than the second preset value, and when the second stroke value is greater than the second preset value, control the SMA motor to move the second preset value along the second direction. In this implementation, when the first stroke value is greater than 0, determine the focus stroke interval, and find out the second preset value corresponding to the focus stroke interval from the preset correspondence between the focus stroke interval and the second preset value, and the second preset value can be used as the anti-shake stroke threshold under the current first stroke value, and control the SMA motor to move along the second direction The stroke does not exceed the second preset value, thereby taking into account the life of the SMA motor and the effect of lens optical image stabilization compensation.

[0015] In combination with the first aspect, in a possible implementation, the control method further includes: when the first stroke value is greater than 0 and the second stroke value is not greater than a second preset value, controlling the SMA motor to move the second stroke value along the second direction. In this implementation, the SMA motor is directly controlled to move the second stroke value along the second direction according to the received instruction, so that the instantaneous displacement value of the SMA motor can be directly anti-shake compensated, thereby improving the optical anti-shake compensation effect of the lens.

[0016] In combination with the first aspect, in a possible implementation, the SMA motor is further configured to be able to drive the lens to move along a third direction, and the third direction intersects with the first direction. After the step of controlling the SMA motor to move the first stroke value along the first direction, the control method further includes: receiving an instruction instructing the SMA motor to move the third stroke value along the third direction. The first stroke value is equal to 0, and the third stroke value is greater than the third preset value, and the SMA motor is controlled to move the third preset value along the third direction. The first stroke value is greater than 0, and the third stroke value is greater than the fourth preset value, and the SMA motor is controlled to move the fourth preset value along the third direction. The fourth preset value is less than the third preset value. In this implementation, the SMA motor can move along the second direction and the third direction for optical image stabilization compensation, and the anti-shake stroke thresholds of the SMA motor in the second direction and the third direction are related to the first stroke value of the SMA motor along the first direction, thereby not only improving the effect of optical image stabilization compensation of the lens, but also ensuring the service life of the SMA motor.

[0017] In a second aspect, an embodiment of the present application provides a controller for an SMA motor, wherein the SMA motor is configured to be able to drive the lens to move along a first direction and a second direction. The first direction is parallel to the focusing direction of the lens, and the second direction intersects with the first direction. The controller includes a first control module, a signal receiving module, and a second control module. The first control module is configured to control the SMA motor to move a first stroke value along the first direction. The signal receiving module is configured to receive an instruction instructing the SMA motor to move a second stroke value along the second direction. The second control module is configured to control the SMA motor to move a first preset value along the second direction when the first stroke value is equal to 0 and the second stroke value is greater than the first preset value. The second control module is also configured to control the SMA motor to move a second preset value along the second direction when the first stroke value is greater than 0 and the second stroke value is greater than the second preset value. The second preset value is less than the first preset value.

[0018] In a third aspect, an embodiment of the present application provides a camera module, which includes a lens, an SMA motor, and a controller of the SMA motor in any of the above embodiments.

[0019] In a fourth aspect, an embodiment of the present application provides an electronic device, which includes a controller of the SMA motor in any of the above embodiments or a camera module in any of the above embodiments.

[0020] In a fifth aspect, an embodiment of the present application provides an electronic device, the electronic device comprising a memory and a processor. The memory comprises instructions. When the processor executes the instructions, the electronic device implements the control method in any of the above embodiments.

[0021] In a sixth aspect, an embodiment of the present application provides a computer-readable storage medium, which includes a program or instruction. When the program or instruction runs on a computer, a control method as in any of the above embodiments is implemented.

[0022] In a seventh aspect, an embodiment of the present application provides a computer program product, which includes a computer program. When the computer program is executed by a processor, it implements the control method in any of the above embodiments.

[0023] The technical effects brought about by any design method in the second to seventh aspects, unless otherwise specified, can be referred to the technical effects brought about by different design methods in the first aspect, and will not be repeated here.

[0024] In an eighth aspect, an embodiment of the present application provides a method for testing an SMA wire, the method comprising: fixing one end of the SMA wire to be tested and connecting the other end to a free object. The SMA wire to be tested is alternated between a power-on state and a power-off state until the SMA wire to be tested breaks. The fatigue resistance of the SMA wire is positively correlated with the duration of alternation between the power-on state and the power-off state.

[0025] Through the above-mentioned embodiments, a free object can be used to alternately apply tensile stress to the SMA wire to be tested during the process of the SMA wire contracting when powered on and during the process of powering off and recovering. This not only simulates the scenario in which the SMA wire is subjected to tensile stress when the SMA motor is working, but also can quickly and effectively detect whether there are adverse factors in the SMA wire that may easily cause breakage, such as cracks, impurities, etc., thereby helping to improve the fatigue resistance of the SMA wire and extend the service life of the SMA wire and the SMA motor.

[0026] In conjunction with the eighth aspect, in a possible implementation, the free object has a preset weight, and the preset weight of the free object is positively correlated with the wire diameter of the SMA wire. Alternatively, the current value passing through the SMA wire to be tested in the power-on state is positively correlated with the wire diameter of the SMA wire to be tested. Therefore, the current value passing through the SMA wire to be tested in the power-on state and the preset weight of the free object can be reasonably determined according to the wire diameter of the SMA wire to be tested, which can not only simulate the actual use scenario of the SMA wire in the SMA motor, but also use the current value passing through the SMA wire to be tested in the power-on state and the setting of the weight of the free object to appropriately accelerate the test process of the SMA wire, and more quickly and effectively detect whether there are adverse factors in the SMA wire that are prone to breakage, thereby improving the test efficiency.

[0027] In a ninth aspect, an embodiment of the present application provides a method for testing an SMA wire, the method comprising: connecting one end of a first SMA wire to be tested to one end of a second SMA wire to be tested, fixing the other end of the first SMA wire to be tested, and fixing the other end of the second SMA wire to be tested. Alternately energize the first SMA wire to be tested and the second SMA wire to be tested until the first SMA wire to be tested or the second SMA wire to be tested breaks. When the first SMA wire to be tested is energized, the second SMA wire to be tested is subjected to the tensile stress applied by the first SMA wire to be tested. When the second SMA wire to be tested is energized, the first SMA wire to be tested is subjected to the tensile stress applied by the second SMA wire to be tested. Among them, the fatigue resistance of the SMA wire is positively correlated with the duration of alternating energization of the first SMA wire to be tested and the second SMA wire to be tested.

[0028] Through the above embodiment, one of the first SMA wire to be tested and the second SMA wire to be tested contracts when powered on and the other recovers when powered off, and the first SMA wire to be tested and the second SMA wire to be tested apply tensile stress to each other, which highly simulates the scenario in which the SMA wire is subjected to tensile stress when the SMA motor is working. It can also quickly and effectively detect whether there are adverse factors in the SMA wire that may easily cause breakage, such as cracks, impurities, etc., thereby helping to improve the fatigue resistance of the SMA wire and extend the service life of the SMA wire and the SMA motor.

[0029] In conjunction with the ninth aspect, in a possible implementation, when the first SMA wire to be tested is powered on, the length of the first SMA wire to be tested does not exceed the maximum recoverable deformation of the first SMA wire to be tested and the maximum recoverable deformation of the second SMA wire to be tested. Alternatively, when the second SMA wire to be tested is powered on, the length of the second SMA wire to be tested does not exceed the maximum recoverable deformation of the first SMA wire to be tested and the maximum recoverable deformation of the second SMA wire to be tested. Thus, the magnitude of the current of the first SMA wire to be tested and the second SMA wire to be tested can be determined based on the maximum recoverable deformation of the first SMA wire to be tested and the maximum recoverable deformation of the second SMA wire to be tested, thereby further improving the effectiveness of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 An exploded schematic diagram of an electronic device provided in an embodiment of the present application;

[0031] Figure 2 A schematic diagram of the structure of a camera module provided in an embodiment of the present application;

[0032] Figure 3 Some fracture diagrams of SMA wires provided in the embodiments of the present application;

[0033] Figure 4 A schematic diagram of fatigue life-strain energy density of an SMA wire provided in an embodiment of the present application;

[0034] Figure 5 A schematic diagram of a manufacturing process flow of an SMA wire provided in an embodiment of the present application;

[0035] Figure 6 A schematic diagram of a stroke threshold value of an SMA motor provided in an embodiment of the present application;

[0036] Figure 7 for Figure 6 A schematic diagram of a stroke value of an SMA motor provided by the illustrated embodiment;

[0037] Figure 8 A schematic diagram of the contraction strain of the SMA wire provided in an embodiment of the present application;

[0038] Fig. 9 A schematic diagram of the spatial range of movement of an SMA motor provided in an embodiment of the present application;

[0039] Fig.10 A schematic diagram of the plane range of movement of an SMA motor provided in an embodiment of the present application;

[0040] Fig.11 A flowchart of a method for controlling an SMA motor provided in an embodiment of the present application;

[0041] Fig.12 for Fig.11 A schematic diagram of a stroke value of the SMA motor in the illustrated embodiment;

[0042] Fig.13 for Fig.11 A schematic diagram of a stroke threshold of the SMA motor in the illustrated embodiment;

[0043] Fig.14 for Fig.11 A schematic diagram of a stroke relationship of the SMA motor in the illustrated embodiment;

[0044] Fig.15 A structural block diagram of a controller of an SMA motor provided in an embodiment of the present application;

[0045] Fig.16 A structural block diagram of an electronic device provided in an embodiment of the present application;

[0046] Fig.17 A schematic diagram of a test scenario for an SMA cable provided in an embodiment of the present application;

[0047] Fig.18 for Fig.17 A flow chart showing the steps of a method for testing an SMA wire in the illustrated embodiment;

[0048] Fig.19 A schematic diagram of another test scenario for the SMA wire provided in an embodiment of the present application;

[0049] Fig. 20 for Fig.19 A flow chart of the steps of a method for testing an SMA wire in the illustrated embodiment.

[0050] Description of reference numerals:

[0051] 1. Screen; 2. Middle frame; 3. Back shell; 4. Mainboard; 5. Camera module; 51. Lens; 52. SMA motor; 100. Electronic device; 6. Application processor; 7. Gyroscope sensor; 500. SMA motor controller; 501. First control module; 502. Signal receiving module; 503. Second control module; 504. Gyroscope filter module; 505. First processing module; 506. Second processing module; 521. SMA wire; 5211. First SMA wire to be tested; 5212. Second SMA wire to be tested; 601. Free object. DETAILED DESCRIPTION

[0052] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0053] Among them, in the description of the embodiments of the present application, unless otherwise specified, "multiple" refers to two or more than two. "At least one item" or similar expressions refer to any combination of these items, including any combination of single items or plural items. For example, at least one item of a, b and c can be represented by: a, b, c, ab, ac, bc or abc, where a, b, c can be single or multiple. "a and / or b" includes the following three combinations: only a, only b, and a combination of a and b.

[0054] In addition, in order to facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "first", "second" and the like are used to distinguish between the same items or similar items with substantially the same functions and effects. Those skilled in the art will understand that the words "first", "second" and the like do not limit the quantity and execution order, and the words "first", "second" and the like do not necessarily limit the difference. At the same time, in the embodiments of the present application, the words "exemplarily" or "for example" are used to indicate examples, illustrations or explanations.

[0055] When describing some embodiments, the expression "connected" and its derivatives are used. The term "connected" should be understood in a broad sense. For example, "connected" can be fixedly connected, detachably connected, or integrated; it can be directly connected or indirectly connected through an intermediate medium. In addition, the use of "based on" means openness and inclusiveness, because the process, step, calculation or other action "based on" one or more of the conditions or values ​​can be based on additional conditions or values ​​beyond the described values ​​in practice.

[0056] In addition, the architecture and scenarios described in the embodiments of the present application are intended to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided in the embodiments of the present application. A person of ordinary skill in the art can appreciate that with the evolution of the architecture and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0057] The embodiment of the present application provides an electronic device, which includes a camera module. The electronic device can be applied to various communication systems or communication protocols, such as: global system of mobile communication (GSM), code division multiple access (CDMA) system, wideband-C division multiple access wireless (WCDMA), general packet radio service (GPRS), long term evolution (LTE), etc.

[0058] The above-mentioned electronic devices include, but are not limited to, electronic devices in the fields of information technology (IT) and communication technology (CT), and can be applied to various scenarios. These electronic devices include, for example, consumer products, household products, vehicle-mounted products, wearable products, financial terminal products, communication products, and intelligent detection products. Exemplarily, the electronic device may include, but is not limited to, a mobile phone, a tablet computer (pad), a SLR camera, a camera, a digital camera, an intelligent wearable product (e.g., a smart watch, a smart bracelet), a smart TV, an extended reality (XR) device, an inertial navigation system (inertial navigation) device, an aerospace equipment, a smart door lock, a smart helmet, etc. The above-mentioned XR device is, for example, a virtual reality (VR) device, an augmented reality (AR) device, or a mixed reality (MR) device, a robot.

[0059] The embodiments of the present application do not limit the specific form of the above-mentioned electronic device.

[0060] Figure 1 An exploded schematic diagram of an electronic device provided in an embodiment of the present application.

[0061] For the convenience of explanation, the following is an example of the electronic device. Figure 1 The mobile phone shown is used as an example. Figure 1 , the electronic device 100 is a mobile phone. The electronic device 100 may include a screen 1, a middle frame 2, a rear shell 3, a mainboard 4 fixed on the middle frame 2, and a camera module 5. The mainboard 4 may be a printed circuit board (PCB).

[0062] Figure 1 The electronic device 100 is merely shown as an example of a possible design, and the actual shape, size, position and structure of each component are not limited to the actual shape, size, position and structure of each component. Figure 1 For example, in some examples, the camera module 5 can be arranged not only on one side of the rear shell 3 but also on one side of the screen 1 of the electronic device 100 .

[0063] Figure 2 A schematic diagram of the structure of a camera module provided in an embodiment of the present application.

[0064] like Figure 2 As shown, the embodiment of the present application provides a camera module 5, which includes a lens 51, an SMA motor 52 and a controller of the SMA motor. Exemplarily, the controller of the SMA motor can be a driver IC.

[0065] The SMA motor may include a plurality of shape memory alloy SMA wires 521. For example, the SMA motor may include, but is not limited to, four SMA wires 521, eight SMA wires 521 (e.g., Figure 2 shown).

[0066] In some optional embodiments, the controller of the SMA motor is configured to control the SMA motor to drive the lens to move along the focus direction of the lens (e.g., the first direction Z), and control the SMA motor to drive the lens to move along a direction intersecting the focus direction of the lens (e.g., the second direction X or the third direction Y). Exemplarily, the controller of the SMA motor is configured to control the SMA motor to drive the lens to move along the focus direction of the lens and in a direction perpendicular to the focus direction of the lens.

[0067] Thus, the SMA motor 5 can be used to control the lens to achieve focus and optical image stabilization compensation. For example, during the operation of the camera module, when the device where the SMA motor 52 is located shakes 100 μm in the second direction X, the SMA motor 52 can control the lens to move 100 μm in the opposite direction of the second direction X to achieve optical image stabilization compensation and reduce image blur caused by the shaking of the device.

[0068] Specifically, in some examples, a portion of the SMA wire 521 in the SMA motor 52 contracts when powered on, and the SMA motor 52 can be controlled to drive the lens 51 to move. The shape memory property of the SMA wire 521 can be used to achieve multiple controls.

[0069] Figure 3 Some schematic diagrams of the fracture of the SMA wire 521 provided in the embodiments of the present application.

[0070] However, when the SMA motor 52 is powered on and moving, the alternating tension on the SMA wire 521 can easily lead to the risk of fatigue fracture of the SMA wire 521. In particular, in order to improve the anti-shake speed and focusing speed, the SMA motor 52 generally uses an extremely thin SMA wire 521, such as an SMA wire 521 with a diameter of only 25 or 30 um. During the manufacturing process or use of this type of SMA motor 52, the SMA wire 521 is more likely to break. Judging from the position of the SMA wire 521 fracture, the fracture mainly includes root breakage (such as Figure 3 A1 in the figure) and the middle line is broken (as shown in Figure 3 (as shown in A2 in the figure).

[0071] Among them, the SMA wire 521 is fixed by pressing the claws, and the root wire breakage is mostly caused by improper pressing of the SMA wire 521 and the claws. For example, the downward pressure of the claws is too large, which crushes the SMA wire 521, reducing the fatigue resistance of the SMA wire 521. For another example, the wire outlet angle of the claws is too large, which causes the stress concentration at the root of the SMA wire 521, exceeding the fatigue resistance of the wire. Among them, fatigue resistance, also known as fatigue resistance, can refer to the ability of an object to withstand repeated stress.

[0072] In order to alleviate the problem of wire breakage at the root, in addition to optimizing the pressing process parameters, a C angle or R angle can be set at the wire outlet of the clamping claw, and glue with moderate hardness can be applied to protect the weak parts of the root of the metal wire and alleviate the problem of stress concentration.

[0073] The wire breakage in the middle is usually caused by factors such as unreasonable structural design of the SMA motor 52, unreasonable motion stroke design of the SMA motor 52, and poor material quality of the SMA wire 521. Among them, the unreasonable structural design of the SMA motor 52 means that the SMA wire 521 is pinched or stuck during the assembly process of the SMA motor 52 due to the design gap between the structural parts of the SMA motor 52. In order to prevent such failure, the structural parts around the SMA wire 521 can be designed into a concave-convex nested structure to prevent the metal wire from sliding into the gap.

[0074] The fatigue life of the SMA wire 521 is related to stress (load) and strain (contraction rate). Under constant stress conditions, as the contraction rate increases, the fatigue life of the SMA wire 521 decreases accordingly. Under constant strain conditions, as the load increases, the fatigue life of the SMA wire 521 decreases accordingly.

[0075] Figure 4 A schematic diagram of fatigue life-strain energy density of an SMA wire provided in an embodiment of the present application.

[0076] like Figure 4 As shown in the figure, if the fatigue life of SMA wire is predicted by the Smith-Watson-Topper (SWT) model, the fatigue life Nf of SMA wire is related to the strain energy density 2σ max Eα (unit: MJ / m 3 ) has a negative exponential function relationship.

[0077] like Figure 4 As shown, the strain energy density 2σ max The larger the Eα, the shorter the fatigue life Nf of the SMA wire. For example, under stresses of 80MPa and 175MPa, although the stress magnitudes are different, the regression of the above negative exponential function relationship can be achieved. This is because the strain energy density Nf is equal to the product of stress and strain.

[0078] The reason why the fatigue life of SMA wire 521 and strain energy density have the above functional relationship is that SMA wire 521 is not 100% pure from a microscopic point of view, but contains a certain amount of impurities. These impurities are called heterogeneous phase particles, which are generally carbides or oxides, and are formed during the smelting or high-temperature heat processing of SMA wire 521. Since the hardness of heterogeneous phase particles is generally significantly higher than that of the metal matrix of SMA wire 521, when SMA wire 521 contracts and is stressed, the interface between these heterogeneous phase particles and the metal matrix will become a stress or strain concentration point, causing microcracks to initiate at the concentration point. The microcracks will expand radially along the radial direction of SMA wire 521 until instantaneous fracture occurs. The greater the stress or strain, the faster the rate of microcrack expansion, and the shorter the fatigue life of the wire.

[0079] Figure 5 A schematic diagram of a manufacturing process flow of the SMA wire 521 provided in an embodiment of the present application.

[0080] like Figure 5 As shown, the production of the SMA wire 521 may specifically include the following steps:

[0081] Step S21, smelting.

[0082] Step S22: hot extrusion.

[0083] Step S23: rolling.

[0084] Step S24: wire drawing.

[0085] Step S25: interpass annealing.

[0086] Step S26, determining the final deformation amount.

[0087] Step S27: final heat-treatment.

[0088] Step S28: training.

[0089] Step S29, making a coating.

[0090] It can be seen that smelting, as the first process step in manufacturing the SMA wire 521, plays a crucial role in the material purity of the SMA wire 521. Although the smelting process of the SMA wire 521 is constantly improving, it is still difficult to reach a 100% pure level, so the presence of heterogeneous phase particles in the SMA wire 521 is often inevitable.

[0091] Figure 6 A schematic diagram of a stroke threshold of an SMA motor provided in an embodiment of the present application.

[0092] The present application embodiment provides a control method of an SMA motor, wherein the SMA motor 52 can be applied to a camera module 5. Figure 6 As shown, the control method mainly limits the movement of the SMA motor 52 along the second direction X or the third direction Y, or in other words, the movement of the SMA motor 52 along the second direction X or the third direction Y has an anti-shake stroke threshold (OIS limit) T1. The anti-shake stroke threshold T1 may be the maximum stroke value that the SMA motor 52 can move along the anti-shake direction. For example, the anti-shake stroke threshold T1 may be 100 μm, and the anti-shake direction may be a direction that intersects or is even perpendicular to the focusing direction of the lens 51.

[0093] like Figure 6 As shown, the initial position O may be the position of the SMA motor 52 when the camera module is not working or the SMA motor 52 is powered off. The far focal length position SF may be the position of the SMA motor 52 when the camera module is at the maximum focal length. The near focal length position SN may be the position of the SMA motor 52 when the camera module is at the minimum focal length.

[0094] AF1 and AF2 may be focus travel thresholds of the SMA motor 52 .

[0095] The second direction X and the third direction Y may be directions intersecting with or even perpendicular to the first direction Z, and the first direction Z may be a focusing direction of the lens 51 .

[0096] Through the above-mentioned embodiments, excessive movement of the SMA motor 52 in the anti-shake direction can be avoided to a certain extent, and the strain energy density on the SMA wire 521 can be reduced, thereby reducing the risk of the SMA wire 521 breaking. If the SMA motor 52 has a large stroke value in both the focus direction and the anti-shake direction, the contraction / extension amplitude of the SMA wire 521 is a superposition state in two directions, which will still increase the risk of the SMA wire 521 breaking and shorten the service life of the SMA motor 52. For example, Figure 6 As shown, the focus stroke value of the SMA motor 52 along the first direction Z is D1, the anti-shake stroke value of the SMA motor 52 along the second direction X is D2, and the actual stroke value of the SMA motor 52 is D3, D3 is the converted superposition value of D1 and D2, and D3 is greatly increased compared to D1 or D2, so that the SMA wire 521 needs to shrink more significantly, which can easily cause the SMA wire 521 to break and fail, thereby reducing the service life of the SMA motor 52 in the camera module 5.

[0097] Figure 7 for Figure 6 A schematic diagram of a stroke value of an SMA motor provided by the illustrated embodiment.

[0098] like Figure 7 As shown, at the same time t, the SMA motor 52 has a corresponding anti-shake stroke code value OIS-C and a focus stroke code value AF-C.

[0099] Among them, the anti-shake stroke code value OIS-C can be regarded as the stroke value of the SMA motor 52 for optical anti-shake compensation. For example, the anti-shake stroke code value OIS-C can be regarded as the first anti-shake stroke value OIS-A along the second direction X, or it can be the second anti-shake stroke value OIS-B along the third direction Y.

[0100] like Figure 7 As shown, the focus stroke code value AF-C can be regarded as the stroke value of the SMA motor 52 driving the lens 51 to focus. For example, the focus stroke code value AF-C can be regarded as the stroke value along the first direction Z.

[0101] In this embodiment, the anti-shake travel threshold range T1 of the SMA motor 52 is fixed.

[0102] The OIS-C is basically within the range of the anti-shake stroke threshold T1 of the SMA motor 52 , and the AF-C is basically within the range of the focus stroke threshold T2 of the SMA motor 52 .

[0103] Figure 8A schematic diagram of the contraction strain of the SMA wire provided in an embodiment of the present application.

[0104] Taking the eight-wire SMA motor as an example, the eight SMA wires are all oblique wires, and each SMA wire can participate in the movement of the SMA motor in the focusing direction and anti-shake direction by contracting.

[0105] like Figure 8 As shown, when the current value and the contraction strain of the SMA wire are fixed, as the AF stroke along the first direction Z increases, the OIS stroke along the second direction X or the second direction Y is continuously reduced.

[0106] like Figure 8 As shown in FIG. 1 , the length of the SMA wire after contraction is L*(1-R). Wherein, L is the length of the SMA wire in the power-off state, or the original wire length. R is the maximum contraction strain rate of the SMA wire, which can be artificially limited by setting the magnitude of the current flowing into the SMA wire.

[0107] Fig. 9 A schematic diagram of the spatial range of movement of an SMA motor provided in an embodiment of the present application.

[0108] like Fig. 9 As shown, for example, the SMA motor 52 is an eight-wire SMA motor. When the maximum contraction amount of each SMA wire 521 remains unchanged, from a spatial perspective, the envelope of the motion trajectory of the eight-wire SMA motor can form a symmetrical octahedral structure.

[0109] Fig.10 A schematic diagram of the plane range of movement of an SMA motor 52 provided in an embodiment of the present application.

[0110] like Fig.10 As shown, the above octahedral structure is projected onto the XZ plane or the YZ plane to form a rhombus.

[0111] In view of this, an embodiment of the present application provides a control method for a shape memory alloy SMA motor 52, wherein the SMA motor 52 is configured to be able to drive the lens 51 to move along a first direction and a second direction. The first direction is parallel to the focusing direction of the lens 51, and the second direction intersects with the first direction. For example, the second direction is perpendicular to the first direction. Thus, the SMA motor 52 can drive the lens 51 to move along a first direction parallel to the focusing direction of the lens 51 to control the focus of the lens 51. The SMA motor 52 can also drive the lens 51 to move along a second direction intersecting with the focusing direction of the lens 51 to control the lens 51 to perform anti-shake compensation for the instantaneous displacement that occurs.

[0112] Fig.11A flowchart of a method for controlling an SMA motor 52 provided in an embodiment of the present application.

[0113] like Fig.11 As shown, the above control method specifically includes the following steps:

[0114] Step S31 , controlling the SMA motor 52 to move a first stroke value along a first direction.

[0115] In some optional embodiments, a focus control signal may be received from an application processor (AP) 6, and the focus control signal may include an instruction to instruct the SMA motor 52 to move a first stroke value along a first direction. For example, if the lens 51 is required to focus at a near focus section, the application processor 6AP may send a focus control signal to a controller of the SMA motor 52, and the focus control signal may include an instruction to instruct the SMA motor 52 to move along the near focus direction of the lens 51.

[0116] Taking the electronic device 100 as a mobile phone as an example, the application processor 6AP can obtain a signal indicating focus through the screen touch sensor of the mobile phone, and thus generate a focus control signal. Taking the electronic device 100 as a camera as an example, the application processor 6AP can obtain a signal indicating focus through the focus case of the camera, and thus generate a focus control signal.

[0117] For example, the SMA motor 52 is controlled to move along the focusing direction of the lens 51 by a first stroke value of 180 μm.

[0118] In some optional embodiments, each time the lens 51 needs to be refocused, it can be restored to the initial position first, and the first stroke value can refer to the distance value between the initial position and the focus position. Exemplarily, the initial position of the lens 51 can refer to the position of the SMA motor 52 when it is powered off.

[0119] In some optional embodiments, the initial position of the lens 51 can be set at the medium-to-telephoto focal section of the lens 51, the first direction can be the direction from the medium-to-telephoto focal section of the lens 51 toward the telephoto focal section, and the first direction can also be the direction from the medium-to-telephoto focal section of the lens 51 toward the near focal section.

[0120] Step S32 , receiving an instruction instructing the SMA motor 52 to move a second stroke value along a second direction.

[0121] In some optional embodiments, taking the gyroscope sensor (gyroscope, Gyro) 7 provided in the electronic device 100 as an example, the gyroscope sensor 7 can monitor the shaking of the electronic device 100 in real time, and send the data of the displacement of the electronic device 100 to the controller of the SMA motor 52. Exemplarily, the data of the displacement of the electronic device 100 may include linear displacement data and angular displacement data. For example, the linear displacement data may include coordinate data in three directions of XYZ, and the angular displacement data may include the angle of deflection of the electronic device 100. For example, the XYZ coordinate values ​​of the linear displacement data are (2500μm, 0μm, 3000μm), respectively, wherein the 3000μm displacement in the direction parallel to the first direction Z can be compensated by the focusing algorithm, and the 2500μm displacement in the direction parallel to the second direction X needs to be compensated by optical image stabilization, for example, the SMA motor 52 is controlled to drive the lens 51 to move 100μm along the second direction X to achieve optical image stabilization compensation. For another example, the electronic device 100 is deflected by 30° in the horizontal direction and 15° in the vertical direction. The angular displacement data and the linear displacement data may also be fused and calculated, and the fused and calculated data may be compensated.

[0122] The displacement data of the electronic device 100 may be regarded as the displacement data of the SMA motor 52 , and the displacement data of the SMA motor 52 may be used to instruct the SMA motor 52 to move along the second direction, so as to perform anti-shake compensation on the displacement of the SMA motor 52 .

[0123] Step S33: the first stroke value is equal to 0, and the second stroke value is greater than the first preset value, and the SMA motor 52 is controlled to move along the second direction by the first preset value.

[0124] In some optional embodiments, the first preset value may be a stroke threshold of the SMA motor 52 moving along the second direction when the first stroke value is equal to 0. In other words, the first preset value may be an anti-shake stroke threshold of the SMA motor 52 when the first stroke value is equal to 0.

[0125] Exemplarily, the first stroke value is equal to 0, the second stroke value is 200 μm, and the first preset value is 100 μm.

[0126] The first preset value may be determined by a preset rated stroke of the SMA motor 52. For example, the first preset value may be 1 / 4 of a preset rated maximum stroke of the SMA motor 52.

[0127] In some optional embodiments, if the first stroke value is 0 and the second stroke value is not greater than the first preset value, the SMA motor 52 is controlled to move the second stroke value along the second direction. Thus, corresponding optical image stabilization compensation can be performed directly according to the instruction transmitted by the gyro sensor 7. For example, if the gyro sensor 7 indicates that the second stroke value of the SMA motor 52 moving along the second direction is 80 μm, the first preset value is 100 μm, and the second stroke value is not greater than the first preset value, the SMA motor 52 is controlled to move 80 μm along the second direction.

[0128] In the embodiment of the present application, step S33 may further include: when the first stroke value is greater than 0 and the second stroke value is greater than a second preset value, controlling the SMA motor 52 to move the second preset value along the second direction.

[0129] In some optional embodiments, the second preset value may be a stroke threshold of the SMA motor 52 moving along the second direction when the first stroke value is greater than 0. In other words, the second preset value may be an anti-shake stroke threshold of the SMA motor 52 when the first stroke value is greater than 0.

[0130] Exemplarily, the first stroke value is 180 μm, the second stroke value is 200 μm, and the second preset value is 80 μm.

[0131] In the embodiment of the present application, the second preset value is smaller than the first preset value. Exemplarily, the second preset value is 80 μm, and the first preset value is 100 μm.

[0132] Fig.12 for Fig.11 A schematic diagram of a stroke value of the SMA motor 52 in the illustrated embodiment.

[0133] like Fig.12 As shown, if the focus stroke value AF-C is greater than 0, the corresponding anti-shake stroke value OIS-C is smaller and does not exceed the second preset value P2. If the focus stroke value AF-C is 0 or close to 0, the corresponding anti-shake stroke value OIS-C is larger and does not exceed the first preset value P1.

[0134] In some optional embodiments, an instruction to instruct the SMA motor 52 to move a first stroke value along a first direction and an instruction to instruct the SMA motor 52 to move a second stroke value along a second direction may be received synchronously. Therefore, in some optional embodiments, the above steps S31 and S33 may be executed synchronously, or steps S31 and S35 may be executed synchronously, thereby synchronously achieving focus and anti-shake of the lens 51.

[0135] In some other optional embodiments, the above step S31 may be performed first, and then step S33 or step S35 may be performed, so that after the focusing of the lens 51 is completed, the optical image stabilization compensation of the lens 51 is performed.

[0136] Through the above embodiment, when the first stroke value of the SMA motor 52 moving along the first direction is 0, the first preset value P1 is the maximum distance that the SMA motor 52 can move along the second direction and the SMA wire 521 is not prone to fatigue failure, so that the lens 51 can be optically image-stabilized to the greatest extent. When the first stroke value of the SMA motor 52 moving along the first direction is greater than 0, the second preset value P2 is the maximum distance that the SMA motor 52 can move along the second direction. The second preset value P2 is reduced compared to the first preset value P1, which can not only ensure the effect of optical image-stabilization compensation for the lens 51, but also avoid excessive stress on the SMA wire 521 when the SMA motor 52 moves in both the first direction and the second direction, and also avoid excessive deformation of the SMA wire 521, effectively extending the service life of the SMA motor 52 in the camera module 5.

[0137] In some optional embodiments, step S34 may be further performed before the above step S33, and step S34 may specifically include:

[0138] Step S341: determine whether the first stroke value is equal to 0.

[0139] Step S342: when the first stroke value is equal to 0, determine whether the second stroke value is greater than a first preset value.

[0140] Step S343: when the first stroke value is greater than 0, determine whether the second stroke value is greater than a second preset value.

[0141] In some optional implementations, the above step S343 may further specifically include:

[0142] Step S3431: The first stroke value is greater than 0, and the focus stroke interval in which the first stroke value is located is determined.

[0143] In some examples, the focus stroke threshold is 500 μm, which is divided into five focus stroke intervals, namely (0, 100 μm], (100 μm, 200 μm], (200 μm, 300 μm], (300 μm, 400 μm], and (400 μm, 500 μm].

[0144] For example, if the first stroke value is 180 μm, the focus stroke interval of the first stroke value is (100 μm, 200 μm].

[0145] Step S3432: determine a second preset value corresponding to the focus travel interval.

[0146] Among them, a plurality of preset relationships between the focus travel interval and the second preset value may be pre-established, so as to obtain the second preset value corresponding to the focus travel interval by table lookup.

[0147] In some examples, as the value of the focus stroke interval increases, the second preset value may gradually decrease. Exemplarily, the preset relationship between the focus stroke interval and the second preset value is respectively the focus stroke interval (0, 100 μm] and the second preset value 90 μm, the focus stroke interval (100, 200] and the second preset value 80 μm, (200, 300] and the second preset value 70 μm, the focus stroke interval (300, 400] and the second preset value 60 μm, and the focus stroke interval (400, 500] and the second preset value 50 μm.

[0148] For example, the second preset value corresponding to the focus stroke interval (100 μm, 200 μm] is 80 μm.

[0149] Step S3433: determine whether the second stroke value is greater than the second preset value.

[0150] For example, the first stroke value is 180 μm, and the second stroke value is 200 μm, and the second stroke value is greater than the second preset value.

[0151] In some optional embodiments, in the above step S33, the first stroke value is 180 μm, the second stroke value is 200 μm, the second stroke value is greater than the second preset value, and the SMA motor 52 is controlled to move along the second direction to the second preset value 80 μm corresponding to the focus stroke interval (100 μm, 200 μm].

[0152] Through the above embodiment, when the first stroke value is greater than 0, the focus stroke interval is determined, and the second preset value corresponding to the focus stroke interval is found from the preset correspondence between the focus stroke interval and the second preset value. The second preset value can be used as the anti-shake stroke threshold under the current first stroke value, and the stroke of the SMA motor 52 moving along the second direction is controlled not to exceed the second preset value, thereby taking into account the life of the SMA motor 52 and the effect of the optical image stabilization compensation of the lens 51.

[0153] In some other optional implementations, in addition to obtaining the second preset value corresponding to the first stroke value by table lookup, a functional relationship between the first stroke value and the second preset value may be pre-established to directly determine the second preset value corresponding to the first stroke value.

[0154] In some optional embodiments, the SMA motor 52 includes a first SMA wire 521 and a second SMA wire 521. By transmitting current to the first SMA wire 521 and the second SMA wire 521, or in other words, transmitting current to at least two SMA wires 521 in the SMA motor 52, the SMA motor 52 can be controlled to drive the lens 51 to move.

[0155] In some optional implementations, the above step S35 may further specifically include:

[0156] Step S331 : The first stroke value is greater than 0, and the second stroke value is greater than a second preset value, transmitting a third current to the first SMA wire 521 to control the first SMA wire 521 to contract.

[0157] Step S332 : If the first stroke value is greater than 0 and the second stroke value is greater than the second preset value, a fourth current is transmitted to the second SMA wire 521 to control the second SMA wire 521 to contract until the SMA motor 52 moves the second preset value along the second direction.

[0158] In some examples, the execution order of step S331 and step S332 can be swapped, and step S331 and step S332 can also be executed synchronously.

[0159] Thus, by energizing at least two SMA wires 521 in the SMA motor 52 , the SMA motor 52 can be controlled to move by a second preset value along the second direction when the first stroke value is greater than 0 and the second stroke value is greater than a second preset value.

[0160] In some further optional implementations, the above step S33 may further specifically include:

[0161] Step S333 : The first stroke value is equal to 0, and the second stroke value is greater than the first preset value, transmitting a first current to the first SMA wire 521 to control the first SMA wire 521 to contract.

[0162] Step S334 : If the first stroke value is greater than 0 and the second stroke value is greater than the first preset value, a second current is transmitted to the second SMA wire 521 to control the second SMA wire 521 to contract until the SMA motor 52 moves the first preset value along the second direction.

[0163] In some examples, the execution order of step S333 and step S334 can be swapped, or step S333 and step S334 can be executed simultaneously.

[0164] Thus, by energizing at least two SMA wires 521 in the SMA motor 52 , the SMA motor 52 can be controlled to move the first preset value along the second direction when the first stroke value is equal to 0 and the second stroke value is greater than the first preset value.

[0165] In the above embodiments, the first current is greater than the third current, and / or the second current is greater than the fourth current.

[0166] Through the above embodiment, when the first stroke value of the SMA motor 52 moving along the first direction is greater than 0, compared with the case where the first stroke value of the SMA motor 52 moving along the first direction is equal to 0, the upper limit of the current threshold transmitted to the at least one SMA wire 521 is reduced, and if the instantaneous displacement of the lens 51 exceeds the second preset value, the current transmitted to the at least one SMA wire 521 is the reduced upper limit of the current threshold, so that the SMA motor 52 can be controlled to move along the second direction by the second preset value, and the second preset value is less than the first preset value.

[0167] In some optional embodiments, the first stroke value includes a first stroke sub-value and a second stroke sub-value. The second preset value includes a first preset sub-value and a second preset sub-value.

[0168] If the first stroke value is the first stroke sub-value, the second preset value is the first preset sub-value. If the first stroke value is the second stroke sub-value, the second preset value is the second preset sub-value. The first stroke sub-value is greater than the second stroke sub-value, and the first preset sub-value is less than the second preset sub-value.

[0169] The first stroke sub-value is greater than the second stroke sub-value, and the first preset sub-value is less than the second preset sub-value.

[0170] For example, the first stroke sub-value is 180 μm, the second stroke sub-value is 280 μm, the first preset sub-value is 80 μm, and the second preset sub-value is 70 μm.

[0171] Through the above embodiment, the corresponding second preset value can be determined according to the size of the first stroke value of the SMA motor 52 moving along the first direction. As the first stroke value increases, the second preset value decreases accordingly, or the second preset value has a negative correlation with the first stroke value, so that when the SMA motor 52 moves along both the first direction and the second direction, it can not only prevent the SMA wire 521 from being subjected to excessive tensile stress, but also ensure the effect of optical image stabilization compensation for the lens 51.

[0172] Fig.13 for Fig.11 A schematic diagram of a travel threshold of the SMA motor 52 in the illustrated embodiment.

[0173] like Fig.13 As shown, in some optional embodiments, there is an inverse linear relationship between the second preset value N1 and the first stroke value M1.

[0174] For example, the distance between the initial position O of the lens 51 and the far focal length position SF of the lens 51 may be unequal to the distance between the initial position O of the lens 51 and the near focal length position SN of the lens 51. Accordingly, when the focus stroke threshold changes, the second preset values ​​corresponding to the first stroke values ​​may also change.

[0175] In some examples, the first preset value is 100 μm. The distance between the initial position of the lens 51 and the near focus position of the lens 51 is the first focus stroke threshold, the first focus stroke threshold is 500 μm, when the first stroke value is 500 μm, the second preset value is 50 μm, and the second preset value is linearly negatively correlated with the first stroke value.

[0176] In some other examples, the first preset value is 100 μm. The distance between the initial position of the lens 51 and the telephoto position of the lens 51 is the second focus stroke threshold, the second focus stroke threshold is 200 μm, when the first stroke value is 200 μm, the second preset value is 80 μm, and the second preset value is linearly negatively correlated with the first stroke value.

[0177] Through this embodiment, the second preset value is changed linearly based on the change of the first stroke value. Further, under different first stroke values, the tensile stress on the SMA wire 521 can be kept within a reasonable range, and the optical image stabilization compensation effect of the lens 51 can be guaranteed, thereby taking into account both the life of the SMA motor 52 and the optical image stabilization compensation effect of the lens 51.

[0178] like Fig.13 As shown, the focal length of the lens 51 commonly used during shooting is the mid-to-long focal length O, and the mid-to-long focal length position of the lens 51 can be set to the position where the SMA motor 52 is in the off state. As a result, a larger anti-shake compensation can be obtained in most shooting scenes, achieving a better user experience. For camera close-focus use scenarios such as mobile phone code scanning and face unlocking, the stroke value of the SMA motor 52 along the focus direction is large. When the electronic device 100 is shaken violently, the stroke value of the SMA motor 52 for optical anti-shake compensation along the direction intersecting the focus direction is reduced, corresponding to the stroke value along the focus direction, thereby avoiding excessive contraction or excessive stretching of the SMA line 521 and extending the service life of the SMA motor 52. Compared with the use scenarios of the mid-to-long focal length and the far-to-long focal length of users shooting people, scenery, etc., in the camera close-focus use scenarios such as mobile phone code scanning and face unlocking, the quality requirements for shooting and imaging are lower, and the compensation effect of optical anti-shake is weakened, which has little effect on the user's experience. Therefore, the above embodiment can cleverly take into account the user's experience and the service life of the SMA motor 52.

[0179] Fig.14 for Fig.11A schematic diagram of the travel relationship of the SMA motor 52 in the illustrated embodiment.

[0180] like Fig.14 As shown, if the focus stroke is represented by a target code value in the focus direction, and the target code value in the focus direction uses the endpoint position of the near focus segment or the endpoint position of the far focus segment of the lens 51 as the zero point of the code value (for example, when the target code value in the focus direction is around 2000, it corresponds to the actual initial position of the lens 51), then the anti-shake stroke threshold and the target code value in the focus direction can present a linear relationship that first increases and then decreases.

[0181] In some optional embodiments, the second preset value also includes a third preset sub-value. The above step S33 also includes:

[0182] Step S335: if the first stroke value is equal to the focus stroke threshold and the second stroke value is greater than the third preset sub-value, the SMA motor 52 is controlled to move along the second direction by the third preset sub-value. The ratio between the third preset sub-value and the first preset value is not less than 40% and not greater than 70%.

[0183] Exemplarily, the ratio between the third preset sub-value and the first preset value may be, but is not limited to, one of the following: 40%, 50%, 55%, 60%, 70%. For example, the third preset sub-value is 50 μm, and the first preset value is 100 μm.

[0184] Through the above embodiment, when the first stroke value reaches the maximum, the tensile stress on the SMA wire 521 along the first direction is the maximum, and the third preset sub-value corresponding to the first stroke value is the minimum value of the second preset values. The above embodiment sets the minimum value of the second preset values ​​to 40% to 70% of the first preset value, which can further take into account the life of the SMA motor 52 and the optical image stabilization compensation effect of the lens 51 in extreme focusing conditions.

[0185] In some optional embodiments, the above control method may further include:

[0186] Step S35 , if the first stroke value is greater than 0 and the second stroke value is not greater than the second preset value, control the SMA motor 52 to move along the second direction by the second stroke value.

[0187] For example, if the first stroke value is 200 μm, the second stroke value is 30 μm, and the second preset value is 60 μm, the first stroke value is greater than 0 and the second stroke value is not greater than the second preset value, and the SMA motor 52 is controlled to move 30 μm along the second direction.

[0188] Through this embodiment, the SMA motor 52 is directly controlled to move the second stroke value along the second direction based on the received instruction, so that the instantaneous displacement value of the SMA motor 52 can be directly anti-shake compensated, thereby improving the optical anti-shake compensation effect of the lens 51.

[0189] In some optional embodiments, the SMA motor 52 is further configured to drive the lens 51 to move along a third direction, which intersects with the first direction. After the above step S31, the following steps may be further included:

[0190] Step S36 , receiving a command instructing the SMA motor 52 to move a third stroke value along a third direction.

[0191] Step S37: If the first stroke value is equal to 0 and the third stroke value is greater than the third preset value, the SMA motor 52 is controlled to move along the third direction by the third preset value. If the first stroke value is greater than 0 and the third stroke value is greater than the fourth preset value, the SMA motor 52 is controlled to move along the third direction by the fourth preset value. The fourth preset value is less than the third preset value.

[0192] The execution of the steps in the above embodiment may refer to the step of controlling the SMA motor 52 to move along the second direction, and thus the details are not repeated here.

[0193] In the embodiment of the present application, the above steps S36 to S37 and the above steps S32 to S33 can be executed simultaneously, or the execution order of the above steps S36 to S37 and the above steps S32 to S33 can be swapped.

[0194] Through the above embodiments, the SMA motor 52 can move along the second direction and the third direction to perform optical image stabilization compensation, and the anti-shake stroke thresholds of the SMA motor 52 in the second direction and the third direction are related to the first stroke value of the SMA motor 52 along the first direction, thereby not only improving the effect of optical image stabilization compensation of the lens 51, but also ensuring the service life of the SMA motor 52.

[0195] Fig.15 This is a structural block diagram of a controller of an SMA motor 52 provided in an embodiment of the present application.

[0196] The present application embodiment provides a controller of an SMA motor 52, wherein the SMA motor 52 is configured to drive a lens 51 to move along a first direction and a second direction. The first direction is parallel to a focusing direction of the lens 51, and the second direction intersects the first direction.

[0197] like Fig.15 As shown, the controller includes a first control module 501 , a signal receiving module 502 and a second control module 503 .

[0198] The first control module 501 is configured to control the SMA motor 52 to move a first stroke value along a first direction.

[0199] The signal receiving module 502 is configured to receive an instruction instructing the SMA motor 52 to move a second stroke value in a second direction.

[0200] The second control module 503 is configured to control the SMA motor 52 to move a first preset value along the second direction when the first stroke value is equal to 0 and the second stroke value is greater than the first preset value.

[0201] The second control module 503 is further configured to control the SMA motor 52 to move along the second direction by a second preset value when the first stroke value is greater than 0 and the second stroke value is greater than a second preset value. The second preset value is less than the first preset value.

[0202] Fig.16 A structural block diagram of an electronic device 100 provided in an embodiment of the present application.

[0203] like Fig.16 As shown, in some optional embodiments, the controller of the SMA motor 52 may further include a gyro filter module 504 , a first processing module 505 and a second processing module 506 .

[0204] In some optional embodiments, the gyro filter module 504 is used to receive the instruction from the gyro sensor 7 that the SMA motor 52 moves the second stroke value in the second direction. The gyro filter module 504 can also filter the instruction from the gyro sensor 7 that the SMA motor 52 moves the second stroke value in the second direction.

[0205] The second processing module 506 can be used to receive an instruction from the application processor 6 to instruct the SMA motor 52 to move the first stroke value along the first direction. The second processing module 506 can also be used to transmit the instruction from the application processor 6 to instruct the SMA motor 52 to move the first stroke value along the first direction to the gyroscope filter module 504. The second processing module 506 can also be used to process the instruction from the application processor 6 to instruct the SMA motor 52 to move the first stroke value along the first direction. For example, after determining that the SMA motor 52 can move the first stroke value along the first direction, the second processing module 506 transmits the processed instruction to the first control module 501. For example, the processed instruction can enable the first control module 501 to first control the SMA motor 52 to drive the lens 51 back to the initial position, and then move the lens 51 along the first direction by the first stroke value.

[0206] The first processing module 505 can also be used to receive the first stroke value and the second stroke value at the same time transmitted by the gyroscope filter module 504, and determine the stroke value of the SMA motor 52 along the second direction based on the first stroke value and the second stroke value, and transmit the control instruction to the second control module 503.

[0207] like Fig.16 As shown, an embodiment of the present application further provides an electronic device 100, which includes a controller of the SMA motor 52 in any of the above embodiments.

[0208] like Fig.16 As shown, the electronic device 100 may further include an application processor 6 and a gyro sensor 7 .

[0209] The embodiment of the present application also provides a camera module 5, which includes a controller of the SMA motor 52 in any of the above embodiments.

[0210] An embodiment of the present application further provides an electronic device 100, which includes the camera module 5 in any one of the above embodiments.

[0211] The embodiment of the present application also provides another electronic device 100, which includes a memory and a processor. The memory includes instructions. When the processor executes the instructions, the electronic device 100 implements the control method in any of the above embodiments.

[0212] An embodiment of the present application further provides a computer-readable storage medium, which includes a program or an instruction. When the program or the instruction is executed on a computer, the control method as in any of the above embodiments is implemented.

[0213] An embodiment of the present application further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the control method in any of the above embodiments is implemented.

[0214] Generally speaking, after the manufacturing process of the SMA wire 521 is determined, it is also necessary to collect the fatigue life data of the manufactured SMA wire 521, and then design the SMA motor 52 and the control logic of the SMA motor 52 based on the life times required for the SMA wire 521 in various usage scenarios to prevent the problem of excessive driving of the SMA wire 521 causing the SMA wire 521 to break and fail prematurely.

[0215] In the related art, the life monitoring method of the SMA wire 521 includes not only tracking the fatigue life in the later stage, but also the early stage detection mainly including the visual detection of the impurity particles of the SMA wire 521 by slicing and the visual detection of the longitudinal cracks on the surface of the SMA wire 521 .

[0216] The visual inspection of the impurity particles of the SMA wire 521 mainly includes observation through focused ion beam (FIB) slicing to visually inspect whether there are impurity particles in the longitudinal section of the SMA wire 521. The visual inspection of the surface longitudinal cracks of the SMA wire 521 requires removing the surface insulating coating of the SMA wire 521 and observing through a scanning electron microscope (SEM) or through FIB slicing.

[0217] Obviously, the above method is time-consuming and labor-intensive, and can only selectively detect a portion of the cross-section or surface of the SMA wire 521. Taking the longitudinal cracks on the surface as an example, they usually appear in sections within a range of hundreds of meters or even thousands of meters on the SMA wire 521. The above method is difficult to eliminate the early fracture risks in the SMA wire 521 one by one.

[0218] Therefore, it is urgent to solve the problem that the fatigue resistance of the SMA wire 521 cannot be tested in large quantities at an early stage.

[0219] Fig.17 A schematic diagram of a test scenario for the SMA wire 521 provided in an embodiment of the present application. Fig.18 A flowchart of a method for testing an SMA wire 521 provided in an embodiment of the present application.

[0220] like Fig.17 and Fig.18 As shown, in view of this, the embodiment of the present application also provides a testing method of the SMA wire 521, and the testing method specifically includes the following steps:

[0221] Step S61 , fixing one end of the SMA wire 521 to be tested and connecting the other end to the free object 601 .

[0222] The free object 601 may have a preset density and weight. For example, the material of the free object 601 may include at least one of iron and copper.

[0223] In some optional embodiments, the SMA wire 521 to be tested can be fixed by a metal clamp, and the SMA wire 521 to be tested can be fixedly connected to the free object 601 by another metal clamp. The two metal clamps are respectively connected to the positive and negative electrodes of the power supply through wires to form a power supply loop system.

[0224] For example, the weight of the free object 601 may be 50 g.

[0225] Step S62 , making the SMA wire 521 to be tested alternate between the power-on state and the power-off state until the SMA wire 521 to be tested is broken.

[0226] In some optional embodiments, by alternately controlling the opening and closing of the switch in the power loop system in the above step S61, the SMA wire 521 to be tested can be alternated between the power-on state and the power-off state. The SMA wire 521 to be tested contracts in the power-on state and recovers in the power-off state. Accordingly, the free object 601 can generate up and down reciprocating motion, thereby realizing the fatigue life test of the SMA wire 521.

[0227] In the embodiment of the present application, the fatigue resistance of the SMA wire 521 is positively correlated with the duration of alternation between the power-on state and the power-off state.

[0228] In some optional embodiments, the duration for which the test SMA wire 521 is powered on and the duration for which it is powered off may be the same or different.

[0229] For example, a test cycle of switching the SMA wire 521 on and off is 2 seconds, and the duty cycle of the SMA wire 521 being powered on is 0.4. In an alternating cycle, the duration of the powered on state may be 0.8 seconds, and the duration of the powered off state may be 1.2 seconds.

[0230] Through the above-mentioned embodiment, the free object 601 can be used to alternately apply tensile stress to the SMA wire 521 to be tested during the process of the SMA wire 521 being energized and contracted and during the process of being de-energized and recovered. This not only simulates the scenario in which the SMA wire 521 is subjected to tensile stress when the SMA motor 52 is in a working state, but also can quickly and effectively detect whether there are any adverse factors in the SMA wire 521 that may easily cause breakage, such as cracks, impurities, etc., thereby helping to improve the fatigue resistance of the SMA wire 521 and extend the service life of the SMA wire 521 and the SMA motor 52.

[0231] In some optional embodiments, the free object 601 has a preset weight, and the preset weight of the free object 601 is positively correlated with the diameter of the SMA wire 521. Alternatively, the current value passing through the SMA wire 521 to be tested in the energized state is positively correlated with the diameter of the SMA wire 521 to be tested.

[0232] Through the above embodiments, the current value passing through the SMA wire 521 to be tested in the power-on state and the preset weight of the free object 601 can be reasonably determined according to the wire diameter of the SMA wire 521 to be tested, which can not only simulate the actual use scenario of the SMA wire 521 in the SMA motor 52, but also use the current value passing through the SMA wire 521 to be tested in the power-on state and the setting of the weight of the free object 601 to appropriately accelerate the test process of the SMA wire 521, so as to more quickly and effectively detect whether there are adverse factors in the SMA wire 521 that may easily cause breakage, thereby improving the test efficiency.

[0233] Take the test of the SMA wire 521 with a diameter of 30 μm and a length of 200 mm as an example. The embodiment of the present application also provides an exemplary testing method, wherein the cross-sectional area of ​​the SMA wire 521 to be tested is approximately 706.9 mm2, the weight of the free object 601 is 50 g, the maximum tensile stress of the SMA wire 521 to be tested is approximately 707 MPa, the resistivity of the SMA wire 521 to be tested is 9.00E-04 Ω·m, the total resistance of the SMA wire 521 to be tested is approximately 254.6 Ω, and the material phase transition temperature of the SMA wire 521 to be tested is approximately 128.9°C. The test frequency of the on-off and off-power of the SMA wire 521 to be tested is 0.5, a test cycle of the on-off and off-power of the SMA wire 521 to be tested is 2s, the duty cycle of the power-on time of the SMA wire 521 to be tested is 0.4, the voltage applied at both ends of the SMA wire 521 to be tested is 25V, the peak current in the SMA wire 521 to be tested is approximately 98.2mA, the maximum contraction rate of the SMA wire 521 to be tested is 2.1%, and the maximum stroke value of the free object 601 is 4.2mm.

[0234] The duty cycle of the power-on time refers to the ratio between the duration of the power-on state and the duration of the cycle in a cycle of alternating between the power-on state and the power-off state.

[0235] Fig.19 A schematic diagram of another test scenario of the SMA wire 521 provided in an embodiment of the present application. Fig. 20 for Fig.19 A flow chart of the steps of a method for testing the SMA wire 521 in the illustrated embodiment.

[0236] like Fig.19 and Fig. 20 As shown, the embodiment of the present application also provides another testing method of the SMA wire 521, the testing method comprising:

[0237] Step S71 , connecting one end of the first SMA wire 5211 to be tested and one end of the second SMA wire 5212 to be tested, fixing the other end of the first SMA wire 5211 to be tested and fixing the other end of the second SMA wire 5212 to be tested.

[0238] In some optional embodiments, the distance between the fixed ends of the first SMA wire 5211 and the second SMA wire 5212 to be tested may be equal to the sum of the lengths of the first SMA wire 5211 and the second SMA wire 5212 to be tested in the power-off state.

[0239] Step S72 , alternately energize the first SMA wire 5211 to be tested and the second SMA wire 5212 to be tested until the first SMA wire 5211 to be tested or the second SMA wire 5212 to be tested is broken.

[0240] In the embodiment of the present application, when the first SMA wire 5211 to be tested is energized, the second SMA wire 5212 to be tested is subjected to the tensile stress applied by the first SMA wire 5211 to be tested.

[0241] In the embodiment of the present application, when the second SMA wire 5212 to be tested is powered on, the first SMA wire 5211 to be tested is subjected to the tensile stress applied by the second SMA wire 5212 to be tested. The fatigue resistance of the SMA wire 521 is positively correlated with the duration of the alternating power supply between the first SMA wire 5211 to be tested and the second SMA wire 5212 to be tested.

[0242] Through the above embodiment, one of the first SMA wire 5211 to be tested and the second SMA wire 5212 to be tested contracts when powered on and the other recovers when powered off, and the first SMA wire 5211 to be tested and the second SMA wire 5212 to be tested apply tensile stress to each other, which highly simulates the scenario in which the SMA wire 521 is subjected to tensile stress when the SMA motor 52 is in a working state, and can also quickly and effectively detect whether there are adverse factors in the SMA wire 521 that may easily cause breakage, such as cracks, impurities, etc., thereby helping to improve the fatigue resistance of the SMA wire 521 and extend the service life of the SMA wire 521 and the SMA motor 52.

[0243] In some optional embodiments, the current size of the above-mentioned SMA wire 521 to be tested (including the first SMA wire 5211 to be tested and the second SMA wire 5212 to be tested) in the power-on state can be positively correlated with the diameter of the SMA wire 521, and can also be positively correlated with the material phase change temperature of the SMA wire 521.

[0244] In some optional embodiments, the duty cycle of the energized time of the SMA wire 521 to be tested may be positively correlated with the diameter of the SMA wire 521 , and may also be positively correlated with the material phase transition temperature of the SMA wire 521 .

[0245] In some optional embodiments, when the first SMA wire 5211 to be tested is energized, the reduced length of the first SMA wire 5211 to be tested does not exceed the maximum recoverable deformation of the first SMA wire 5211 to be tested and the maximum recoverable deformation of the second SMA wire 5212 to be tested.

[0246] In some optional embodiments, when the second SMA wire 5212 to be tested is energized, the reduced length of the second SMA wire 5212 to be tested does not exceed the maximum recoverable deformation of the first SMA wire 5211 to be tested and the maximum recoverable deformation of the second SMA wire 5212 to be tested.

[0247] Through the above embodiment, the current passed through the first SMA wire 5211 and the second SMA wire 5212 can be determined based on the maximum recoverable deformation of the first SMA wire 5211 and the maximum recoverable deformation of the second SMA wire 5212, thereby further improving the effectiveness of the test.

[0248] The above description is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that any technician familiar with the technical field can think of within the technical scope disclosed in the present application should be covered within the protection scope of the present application.

Claims

1. A control method for a shape memory alloy SMA motor, characterized in that: The SMA motor is configured to drive the lens to move along a first direction and a second direction; the first direction is parallel to the focusing direction of the lens, and the second direction intersects with the first direction; The control method comprises: Controlling the SMA motor to move a first stroke value along the first direction; receiving an instruction instructing the SMA motor to move a second stroke value along the second direction; The first stroke value is equal to 0, and the second stroke value is greater than a first preset value, and the SMA motor is controlled to move the first preset value along the second direction; The first stroke value is greater than 0, and the second stroke value is greater than a second preset value, and the SMA motor is controlled to move along the second direction by the second preset value; the second preset value is less than the first preset value.

2. The control method of the SMA motor according to claim 1, characterized in that: The SMA motor includes a first SMA wire and a second SMA wire; The step of controlling the SMA motor to move the first preset value along the second direction comprises: transmitting a first current to the first SMA wire to control the first SMA wire to contract; transmitting a second current to the second SMA wire to control the second SMA wire to contract until the SMA motor moves along the second direction by the first preset value; The step of controlling the SMA motor to move the second preset value along the second direction comprises: transmitting a third current to the first SMA wire to control the first SMA wire to contract; transmitting a fourth current to the second SMA wire to control the second SMA wire to contract until the SMA motor moves along the second direction by the second preset value; The first current is greater than the third current, or the second current is greater than the fourth current.

3. The control method of the SMA motor according to claim 1 or 2, characterized in that: If the first stroke value is a first stroke sub-value, the second preset value is the first preset sub-value; if the first stroke value is a second stroke sub-value, the second preset value is the second preset sub-value; The first stroke sub-value is greater than the second stroke sub-value, and the first preset sub-value is less than the second preset sub-value.

4. The control method of the SMA motor according to any one of claims 1 to 3, characterized in that: There is an inverse linear relationship between the second preset value and the first stroke value.

5. The control method of the SMA motor according to any one of claims 1 to 4, characterized in that: The second preset value also includes a third preset sub-value; The first stroke value is equal to the focus stroke threshold, and the second stroke value is greater than the third preset sub-value, controlling the SMA motor to move the third preset sub-value along the second direction; A ratio between the third preset sub-value and the first preset value is not less than 40% and not more than 70%.

6. The control method of the SMA motor according to any one of claims 1 to 5, characterized in that: The first stroke value is greater than 0, and the second stroke value is greater than a second preset value, and the step of controlling the SMA motor to move the second preset value along the second direction comprises: The first stroke value is greater than 0, and a focus stroke interval in which the first stroke value is located is determined; Determining the second preset value corresponding to the focus travel interval; It is determined whether the second stroke value is greater than the second preset value. If the second stroke value is greater than the second preset value, the SMA motor is controlled to move along the second direction by the second preset value.

7. The control method of the SMA motor according to any one of claims 1 to 6, characterized in that: The control method further comprises: The first stroke value is greater than 0, and the second stroke value is not greater than the second preset value, and the SMA motor is controlled to move along the second direction by the second stroke value.

8. The control method of the SMA motor according to any one of claims 1 to 7, characterized in that: The SMA motor is further configured to drive the lens to move along a third direction; the third direction intersects with the first direction; After the step of controlling the SMA motor to move a first stroke value along the first direction, the control method further comprises: receiving an instruction instructing the SMA motor to move a third stroke value along the third direction; The first stroke value is equal to 0, and the third stroke value is greater than a third preset value, controlling the SMA motor to move along the third direction by the third preset value; The first stroke value is greater than 0, and the third stroke value is greater than a fourth preset value, and the SMA motor is controlled to move along the third direction by the fourth preset value; the fourth preset value is less than the third preset value.

9. A control device for an SMA motor, characterized in that: The SMA motor is configured to drive the lens to move along a first direction and a second direction; the first direction is parallel to the focusing direction of the lens, and the second direction intersects with the first direction; The control device comprises: A first control module, configured to control the SMA motor to move a first stroke value along the first direction; a signal receiving module configured to receive an instruction instructing the SMA motor to move a second stroke value along the second direction; The second control module is configured to control the SMA motor to move the first preset value along the second direction when the first stroke value is equal to 0 and the second stroke value is greater than the first preset value; the second control module is also configured to control the SMA motor to move the second preset value along the second direction when the first stroke value is greater than 0 and the second stroke value is greater than the second preset value; the second preset value is less than the first preset value.

10. A camera module, characterized in that: The invention comprises a lens, an SMA motor and a control device for the SMA motor as claimed in claim 9.

11. An electronic device, characterized in that: Includes a control device for the SMA motor as described in claim 9 or a camera module as described in claim 10.

12. An electronic device, characterized in that: include: Memory, including instructions; A processor, when the processor executes the instruction, enables the electronic device to implement the control method according to any one of claims 1 to 8.

13. A computer-readable storage medium, characterized in that: The method comprises a program or an instruction, and when the program or the instruction is executed on a computer, the control method according to any one of claims 1 to 8 is implemented.

14. A computer program product, characterized in that The invention comprises a computer program, and when the computer program is executed by a processor, the control method according to any one of claims 1 to 8 is implemented.

15. A method for testing an SMA wire, characterized in that: The test method includes: Fix one end of the SMA wire to be tested and connect the other end to a free object; Alternating the SMA wire to be tested between a powered-on state and a powered-off state until the SMA wire to be tested breaks; The anti-fatigue performance of the SMA wire is positively correlated with the duration of alternation between the power-on state and the power-off state.

16. The method for testing an SMA wire according to claim 15, characterized in that: The free object has a preset weight, and the preset weight of the free object is positively correlated with the wire diameter of the SMA wire; or, The current value passing through the SMA wire to be tested in the energized state is positively correlated with the wire diameter of the SMA wire to be tested.

17. A method for testing an SMA wire, characterized in that: The test method includes: Connecting one end of a first SMA wire to be tested to one end of a second SMA wire to be tested, fixing the other end of the first SMA wire to be tested, and fixing the other end of the second SMA wire to be tested; Alternately energizing the first SMA wire to be tested and the second SMA wire to be tested until the first SMA wire to be tested or the second SMA wire to be tested is broken; Among them, when the first SMA wire to be tested is energized, the second SMA wire to be tested is subjected to the tensile stress applied by the first SMA wire to be tested; or when the second SMA wire to be tested is energized, the first SMA wire to be tested is subjected to the tensile stress applied by the second SMA wire to be tested; the fatigue resistance of the SMA wire is positively correlated with the length of time that the first SMA wire to be tested and the second SMA wire to be tested are alternately energized.

18. The method for testing an SMA wire according to claim 17, characterized in that: When the first SMA wire to be tested is powered on, the shortened length of the first SMA wire to be tested does not exceed the maximum recoverable deformation of the first SMA wire to be tested and the maximum recoverable deformation of the second SMA wire to be tested; or, When the second SMA wire to be tested is powered on, the reduced length of the second SMA wire to be tested does not exceed the maximum recoverable deformation of the first SMA wire to be tested and the maximum recoverable deformation of the second SMA wire to be tested.

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