Linear output rotary motion actuator based on two-way shape memory alloy

Abstract

The invention discloses a linear output rotary motion actuator based on a two-way shape memory alloy, which comprises a cylindrical sleeve, a hollow cylindrical driven arm is coaxially arranged in the cylindrical sleeve, a shape memory alloy spring is arranged between the bottom of the driven arm and the bottom of the cylindrical sleeve, a cylindrical cam is arranged in the driven arm, and the cylindrical cam is arranged in the cylindrical sleeve. The cylindrical cam is matched with the two rollers, and the two rollers are installed on the two opposite sides of the driven arm respectively. By utilizing the characteristics that the two-way memory effect can memorize the shapes of an austenite phase and a martensite phase and can spontaneously deform along with the temperature, the defect that the one-way shape memory effect needs external force for auxiliary work is avoided; and the problems of poor control precision and high control difficulty caused by a nonlinear deformation rule of the shape memory alloy are solved through a cylindrical cam mechanism.

Description

Technical Field

[0001] The invention belongs to the technical field of shape memory alloy structures and relates to a linear output rotary motion actuator based on a two-way shape memory alloy. Background Art

[0002] Shape memory alloy is a special functional material that can undergo phase change with temperature changes after being deformed by external force and return to its original shape. During the phase change process, shape memory alloys can produce large recoverable deformation and recovery stress. Based on this feature, shape memory alloys are very suitable for making actuators. However, after each phase change and actuation of the shape memory alloy actuator with a one-way shape memory effect, an external force needs to be applied to it to deform it before the next actuation can be performed. This increases the difficulty of applying shape memory alloy actuators with a one-way shape memory effect, making it inconvenient to use them in application scenarios that require the actuator to work completely autonomously. At the same time, the law of deformation of shape memory alloy materials with temperature during the phase change process is nonlinear, which makes it difficult to accurately control the deformation of shape memory alloys. Summary of the invention

[0003] The purpose of the present invention is to provide a linear output rotary motion actuator based on a two-way shape memory alloy. The actuator utilizes the two-way memory effect to memorize the shapes in both the austenite phase and the martensite phase and can spontaneously deform with temperature. The cylindrical cam mechanism is used to solve the problems of poor control accuracy and difficulty in control caused by the nonlinear deformation law of shape memory alloys.

[0004] The technical solution adopted by the present invention is a linear output rotary motion actuator based on a two-way shape memory alloy, comprising a cylindrical sleeve, a hollow cylindrical follower arm is coaxially arranged inside the cylindrical sleeve, a shape memory alloy spring is arranged between the bottom of the follower arm and the bottom of the cylindrical sleeve, a cylindrical cam is arranged inside the follower arm, the cylindrical cam cooperates with two rollers, and the two rollers are respectively installed on opposite sides of the follower arm.

[0005] The present invention is also characterized in that:

[0006] A hole I is provided at the top center of the cylindrical sleeve, a support block is installed in the hole I, a hole VI is provided at the center of the support block, a cylindrical cam is arranged inside the cylindrical sleeve, and an output end of the cylindrical cam extends out of the hole VI.

[0007] A circle of rolling grooves is arranged on the outer wall of the cylindrical cam, and two rollers are hidden in the rolling grooves.

[0008] A hole IV and a hole V with the same shape and size and corresponding positions are respectively arranged on opposite sides of the upper part of the driven arm, and two rollers are respectively installed in the hole IV and the hole V.

[0009] An inner electrode sheet I is provided at the bottom of the cylindrical sleeve, and two claws A are provided on the surface of the electrode sheet I; an electrode sheet II is provided on the outer side of the bottom of the driven arm, and claws B are provided at both ends of the surface of the electrode sheet II, and the two ends of the shape memory alloy spring are respectively wound on the claws A and B.

[0010] The material of the shape memory alloy spring is nickel-titanium alloy and has a two-way memory effect.

[0011] A hole II is provided at the center of the bottom end of the cylindrical sleeve, and a hole VII is provided at the center of the electrode sheet I. The wire passes through the hole II and the hole VII to connect to the electrode sheets I and II to realize electrical conduction.

[0012] The design process of the rolling groove curve shape is as follows:

[0013] Step 1: Measure the temperature-corresponding deformation data of the shape memory alloy spring to obtain the temperature-deformation curve u of the austenite phase transformation stage. a =f a (T) and the temperature-deformation curve u of the martensitic phase transformation stage m =f m (T), where u a 、u m is the spring deformation, T is the temperature;

[0014] Step 2: Swap the temperature-deformation curve u a =f a (T) and u m =f m (T) is the independent variable and dependent variable, and the temperature is obtained by using the deformation to obtain the temperature function T a =g a (u a ) and T m =g m (u m ), the deformation of the shape memory alloy spring in the two phase change stages is equal to the maximum temperature, that is, u a max =u m max And T a_max =T m_max ,u a_max 、T a_max is the maximum deformation and temperature of the shape memory alloy spring in the austenite phase, u m_max 、T m_max The maximum deformation and temperature of the shape memory alloy spring in the martensite phase;

[0015] Step 3: Since the output mode of the actuator is linear, the output function d = k·T is obtained, where d is the output displacement and k is the proportional coefficient, which represents the proportional relationship between temperature and output displacement. a =g a (u a ) and T m =g m (u m ) into the output function d = k·T, and the output function d of the austenite phase and the martensite phase is obtained. a = k·g a (u a ) and d m = k·g m (u m ), at which point the actuator has a maximum output displacement d max The same, that is, d max =d a_max =d m_max , d a_max ,d m_max are the maximum output displacements of the actuator in the austenite phase and martensite phase stages, respectively. The deformation of the shape memory alloy spring is taken as the x-axis coordinate of the profile, and the actuator output displacement d is taken as the y-axis coordinate, that is, the profile equations of the austenite phase transformation stage and the martensite phase transformation stage in the two-dimensional plane coordinate system are obtained;

[0016] Step 4: Convert the profile equation in the two-dimensional plane coordinate system (x, y) to the cylindrical coordinate system (R, θ, z) to obtain the profile equation of the rolling groove on the cylindrical cam surface. The conversion relationship is z = x, R = y max / 2π,θ=2π·y(x) / y max ,y max It is the maximum value of the y-axis direction in the two-dimensional plane coordinate system (x, y);

[0017] The two rollers in the actuator undergo austenite transformation and martensite transformation respectively in one complete reciprocating motion of the driven arm, so there is y max =4·d max At the same time, θ should be calculated separately for each phase transformation stage. The surface profile equation of the cylindrical cam in the austenite phase transformation stage is:

[0018]

[0019] The profile equation of the martensitic phase transformation is:

[0020]

[0021] The beneficial effects of the present invention are as follows:

[0022] 1) The driving element used in the present invention is a nickel-titanium alloy spring with a two-way shape memory effect. Compared with shape memory alloy wire, the shape memory alloy spring has the characteristics of large driving force and large deformation range, and is controlled by heating by power on, so that the actuator has the advantages of large actuation range and convenient control.

[0023] 2) The present invention converts the nonlinear deformation law of the shape memory alloy itself into a linear rotation output, thereby improving the resolution of deformation controlled by temperature, thereby improving the control accuracy of the shape memory alloy actuator and reducing the control difficulty.

[0024] 3) The present invention realizes the linear output processing of the complete thermal cycle (including austenite phase transformation and martensite phase transformation) of the two-way shape memory alloy by designing the surface profile of the cylindrical cam. At the same time, it does not have the disadvantage of the one-way memory effect that cannot automatically restore the initial working state, and can output the required rotational motion any number of times. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall structure of the linear output rotary motion actuator based on the two-way shape memory alloy of the present invention;

[0026] Figure 2 It is a schematic diagram of the cylindrical sleeve structure of the linear output rotary motion actuator based on the two-way shape memory alloy of the present invention;

[0027] Figure 3 It is a schematic diagram of the cylindrical cam structure of the linear output rotary motion actuator based on the dual-path shape memory alloy of the present invention;

[0028] Figure 4 It is a schematic diagram of the structure of the driven arm of the linear output rotary motion actuator based on the two-way shape memory alloy of the present invention;

[0029] Figure 5 It is a schematic diagram of the support block structure of the linear output rotary motion actuator based on the two-way shape memory alloy of the present invention;

[0030] Figure 6 It is a schematic diagram of the roller structure of the linear output rotary motion actuator based on the two-way shape memory alloy of the present invention;

[0031] Figure 7 It is a schematic structural diagram of an electrode sheet I of a linear output rotary motion actuator based on a two-way shape memory alloy according to the present invention;

[0032] Figure 8 It is a schematic diagram of the structure of the electrode sheet II of the linear output rotary motion actuator based on the two-way shape memory alloy of the present invention.

[0033] In the figure, 1. cylindrical sleeve, 2. cylindrical cam, 3. follower arm, 4. support block, 5. roller, 6. shape memory alloy spring, 7. claw A, 8. claw B, 11. electrode sheet I, 12. hole I, 13. hole II, 21. rolling groove, 22. hole III, 31. electrode sheet II, 311. hole VII, 32. hole IV, 33. hole V, 41. hole VI, 51. roller pin, 52. roller wheel. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] Example 1

[0036] The present invention is based on a linear output rotary motion actuator of a two-way shape memory alloy, such as Figure 1 As shown, it includes a cylindrical sleeve 1, as Figure 2 As shown, a hole I12 is provided at the top center of the cylindrical sleeve 1, and the support block 4 is installed in the hole I12;

[0037] like Figure 3 As shown, the output end of the cylindrical cam 2 is provided with a hole III22, and the function of the hole III22 is to output rotational motion. For example, after the rope passes through the hole III22, the actuator can contract or relax the rope. The surface of the contour end of the cylindrical cam 2 is provided with a rolling groove 21;

[0038] Example 2

[0039] like Figure 4 As shown, holes IV32 and holes V33 of exactly the same shape, size and corresponding positions are respectively provided on opposite sides of the upper portion of the driven arm 3, and two identical rollers 5 are respectively installed in the holes IV32 and holes V33.

[0040] like Figure 5 As shown, a hole VI 41 is provided at the center of the support block 4, the cylindrical cam 2 is provided inside the cylindrical sleeve 1, the output end of the cylindrical cam 2 extends out from the hole VI 41, the follower arm 3 is provided inside the cylindrical sleeve 1, below the cylindrical cam 2, and the shape memory alloy spring 6 is a driving element of the actuator, provided between the bottom of the follower arm 3 and the bottom end of the cylindrical sleeve 1.

[0041] like Figure 6 As shown, the roller 5 is composed of a roller pin 51 and a roller wheel 52. Among the two rollers 5, the two roller pins 51 pass through the hole IV 32 and the hole V 33 respectively. The two roller wheels 52 are embedded in the rolling groove 21 on the surface of the cylindrical cam 2. The roller wheel 52 can only move in the rolling groove 21. The roller 5 as a whole is constrained by the roller wheel 52 and the follower arm 3. The follower arm 3 and the cylindrical cam 2 are connected through the roller 5, so that the reciprocating motion of the follower arm 3 along the axial direction of the cylindrical sleeve 1 can be converted into the rotational motion of the cylindrical cam 2.

[0042] Example 3

[0043] The electrode sheet I11 is arranged at the bottom of the inner cavity of the cylindrical sleeve 1. Figure 4 As shown, the electrode sheet II31 is arranged at the bottom end of the driven arm 3, as shown in FIG. Figure 7 As shown, the electrode sheet I11 is provided with a hole VII311 in the center, and the bottom end of the cylindrical sleeve 1 is provided with a hole II13 in the center. The wire passes through the hole II13 and the hole VII311 to connect to the electrode sheet I11 and the electrode sheet II31 to realize electrical connection. The surface of the electrode sheet I11 is provided with two claws A7, and the two claws A7 are respectively located on the opposite sides of the hole VII33; Figure 8 As shown, two claws B8 are provided on the surface of the electrode sheet II31, the upper end of the shape memory alloy spring 6 is wound around the two claws B8, and the lower end of the shape memory alloy spring 6 is wound around the two claws A7, so as to realize the fixed connection with the electrode sheet I11 and the electrode sheet II31.

[0044] The shape memory alloy spring 6 is made of nickel-titanium alloy and has a two-way memory effect. It stretches when the temperature rises to or above the austenite transformation start temperature, and starts to contract when the temperature drops to or below the martensite transformation start temperature.

[0045] The curve shape of the rolling groove 21 is the key to converting the nonlinear deformation law of the shape memory alloy spring 6 into a linear rotational motion. The curve shape of the rolling groove 21 is obtained by a profile design method, and the specific steps are as follows:

[0046] Step 1: According to the constitutive relationship of the shape memory alloy, or by experimentally measuring the temperature-corresponding deformation data of the shape memory alloy spring 6, the temperature-deformation curve u of the austenite phase transformation stage is obtained. a =f a (T) and the temperature-deformation curve u of the martensitic phase transformation stage m =f m (T), where u a 、u m is the spring deformation, T is the temperature;

[0047] Step 2: Swap the temperature-deformation curve u a =f a (T) and u m =f m (T) is the independent variable and dependent variable, and the temperature is obtained by using the deformation to obtain the temperature function T a =g a (u a ) and T m =g m (u m), it can be seen from the characteristics of shape memory alloy that the spring deformation and the maximum temperature in the two phase change stages are equal, that is, u a_max =u m_max And T a_max =T m_max ,u a_max 、T a_max is the maximum spring deformation and temperature in the austenite phase, u m_max 、T m_max is the maximum spring deformation and temperature in the martensite phase;

[0048] Step 3: Since the output mode of the actuator is linear, the output function d = k·T is obtained, where d is the output displacement and k is the proportional coefficient, which represents the proportional relationship between temperature and output displacement. a =g a (u a ) and T m =g m (u m ) into the output function d = k·T, and the output function d of the austenite phase and the martensite phase is obtained. a = k·g a (u a ) and d m = k·g m (u m ), at which point the actuator has a maximum output displacement d max The same, that is, d max =d a_max =d m_max , d a_max ,d m_max are the maximum output displacements of the actuator in the austenite phase and martensite phase stages respectively, the deformation of the shape memory alloy spring 6 is taken as the x-axis coordinate of the profile, and the actuator output displacement d is taken as the y-axis coordinate, that is, the profile equations of the austenite phase transformation stage and the martensite phase transformation stage in the two-dimensional plane coordinate system are obtained;

[0049] Step 4: Convert the profile equation in the two-dimensional plane coordinate system (x, y) to the cylindrical coordinate system (R, θ, z) (R is the radius, θ is the angle, and z is the z-axis coordinate) to obtain the profile equation of the rolling groove on the cylindrical cam surface. The conversion relationship is z = x, R = y max / 2π,θ=2π·y(x) / y max ,y maxis the maximum value of the y-axis direction in the two-dimensional plane coordinate system (x, y). In the cylindrical coordinate system (R, θ, z), the contour equations of the austenite phase transformation stage and the martensite phase transformation stage can be connected end to end to obtain the contour during the entire heating and cooling process. Because the two rollers in this actuator experience the austenite phase transformation stage and the martensite phase transformation stage respectively in a complete reciprocating motion of the driven arm, we have y max =4·d max At the same time, θ should be calculated separately for each phase transformation stage. The profile equation of the rolling groove 21 on the surface of the cylindrical cam 2 in the austenite phase transformation stage is:

[0050]

[0051] The profile equation of the rolling groove 21 on the surface of the cylindrical cam 2 in the martensitic phase transformation stage is:

[0052] R=4·d max 2π

[0053] θ=2π·k·g m (u m ) / 4·d max

[0054] z=u m

[0055] The specific working process of the linear output rotary motion actuator based on the two-way shape memory alloy of the present invention is: during the working process, the cylindrical cam 2 is allowed to continuously output the rotary motion in the same direction in a linear law. The control method is that the electrode sheet I11 and the electrode sheet II31 are in contact with the two ends of the shape memory alloy spring 6, and the shape memory alloy spring 6 is energized for a certain period of time to cause an austenite phase transformation to produce elongation deformation. When the shape memory alloy spring 6 is elongated, it pushes the driven arm 3 to move toward the top of the cylindrical sleeve 1. After the driven arm 3 moves, it drives the roller 5 to move in the rolling groove 21 on the surface of the cylindrical cam 2 (the moving range of the two rollers is the contour corresponding to the austenite phase transformation stage), thereby causing the cylindrical cam 2 to rotate and output linear rotary motion. After the shape memory alloy spring 6 is stretched to the maximum (austenite phase transformation is completely completed), the shape memory alloy spring 6 is gradually cooled down by cutting off the power supply to undergo martensite phase transformation, thereby generating contraction deformation, pulling the driven arm 3 to move toward the bottom end of the cylindrical sleeve 1. After the driven arm 3 moves, it drives the roller 5 to continue moving in the rolling groove 21 on the surface of the cylindrical cam 2 (the moving ranges of the two rollers are both the contours corresponding to the martensite phase transformation stage), thereby keeping the cylindrical cam 2 rotating and also outputting linear rotational motion.

[0056] The linear output rotary motion actuator of the present invention is based on a two-way shape memory alloy. The two-way memory effect can memorize the shapes in both the austenite phase and the martensite phase and can spontaneously deform with temperature, thereby avoiding the disadvantage that the one-way shape memory effect requires external force for auxiliary work, and solves the problems of poor control accuracy and great control difficulty caused by the nonlinear deformation law of the shape memory alloy through a cylindrical cam mechanism.

[0057] The linear output rotary motion actuator based on the two-way shape memory alloy of the present invention avoids the disadvantage that the one-way shape memory effect requires external force to assist the work, and can convert the nonlinear deformation law of the shape memory alloy into a rotary motion that is linear with the temperature change law. This greatly increases the control resolution and control accuracy of the actuation mode based on the shape memory alloy, reduces the control difficulty, and also has the characteristics of large driving force and reusability.

Claims

1. A linear output rotary motion actuator based on a two-way shape memory alloy, characterized in that: The invention comprises a cylindrical sleeve (1), a hollow cylindrical driven arm (3) is coaxially arranged inside the cylindrical sleeve (1), a shape memory alloy spring (6) is arranged between the bottom of the driven arm (3) and the bottom of the cylindrical sleeve (1), a cylindrical cam (2) is arranged inside the driven arm (3), the cylindrical cam (2) cooperates with two rollers (5), and the two rollers (5) are respectively installed on opposite sides of the driven arm (3).

2. The linear output rotary motion actuator based on a two-way shape memory alloy according to claim 1, characterized in that: A hole I (12) is provided at the center of the top of the cylindrical sleeve (1), the support block (4) is installed in the hole I (12), a hole VI (41) is provided at the center of the support block (4), the cylindrical cam (2) is arranged inside the cylindrical sleeve (1), and the output end of the cylindrical cam (2) extends out from the hole VI (41).

3. The linear output rotary motion actuator based on a two-way shape memory alloy according to claim 2, characterized in that: A circle of rolling grooves (21) are provided on the outer wall of the cylindrical cam (2), and two rollers (5) are hidden in the rolling grooves (21).

4. The linear output rotary motion actuator based on a two-way shape memory alloy according to claim 3, characterized in that: The upper opposite sides of the driven arm (3) are respectively provided with a hole IV (32) and a hole V (33) with the same shape and size and corresponding positions, and two rollers (5) are respectively installed in the hole IV (32) and the hole V (33).

5. The linear output rotary motion actuator based on a two-way shape memory alloy according to claim 3, characterized in that: The bottom of the cylindrical sleeve (1) is provided with an inner electrode sheet I (11), and the surface of the electrode sheet I (11) is provided with two claws A (7); the outer side of the bottom of the driven arm (3) is provided with an electrode sheet II (31), and the two ends of the surface of the electrode sheet II (31) are respectively provided with claws B (8), and the two ends of the shape memory alloy spring (6) are respectively wound around the claws A (7) and the claws B (8).

6. The linear output rotary motion actuator based on a two-way shape memory alloy according to claim 5, characterized in that: The shape memory alloy spring (6) is made of nickel-titanium alloy and has a two-way memory effect.

7. The linear output rotary motion actuator based on a two-way shape memory alloy according to claim 5, characterized in that: A hole II (13) is provided at the center of the bottom end of the cylindrical sleeve (1), and a hole VII (311) is provided at the center of the electrode sheet I (11). A wire passes through the hole II (13) and the hole VII (311) to connect to the electrode sheet I (11) and the electrode sheet II (31) to realize electrical conduction.

8. The linear output rotary motion actuator based on a two-way shape memory alloy according to claim 7, characterized in that: The design process of the curve shape of the rolling groove (21) is as follows: Step 1, measuring the temperature-corresponding deformation data of the shape memory alloy spring (6) to obtain the temperature-deformation curve u of the austenite phase transformation stage a =f a (T) and the temperature-deformation curve u of the martensitic phase transformation stage m =f m (T), where ua and um are spring deformations and T is temperature; Step 2: Swap the temperature-deformation curve u a =f a (T) and u m =f m (T) is the independent variable and dependent variable, and the temperature is obtained by using the deformation to obtain the temperature function T a =g a (u a ) and T m =g m (u m ), the deformation and the maximum temperature of the shape memory alloy spring (6) in the two phase change stages are equal, that is, u a_max =u m_max And T a_max =T m_max ,u a_max , T a_max is the maximum deformation and temperature of the shape memory alloy spring (6) in the austenite phase, u m_max , T m_max are the maximum deformation and the maximum temperature of the shape memory alloy spring (6) in the martensite phase; Step 3: Since the output mode of the actuator is linear, the output function d = k·T is obtained, where d is the output displacement and k is the proportional coefficient, which represents the proportional relationship between temperature and output displacement. a =g a (u a ) and T m =g m (u m ) into the output function d = k·T, and the output function d of the austenite phase and the martensite phase is obtained. a = k·g a (u a ) and d m = k·g m (u m ), at which point the actuator has a maximum output displacement d max The same, that is, d max =d a_max =d m_max , d a_max ,d m_max are the maximum output displacements of the actuator in the austenite phase and martensite phase stages respectively, the deformation of the shape memory alloy spring (6) is taken as the x-axis coordinate of the profile, and the actuator output displacement d is taken as the y-axis coordinate, that is, the profile equations of the austenite phase transformation stage and the martensite phase transformation stage in the two-dimensional plane coordinate system are obtained; Step 4, convert the profile equation in the two-dimensional plane coordinate system (x, y) into the cylindrical coordinate system (R, θ, z) to obtain the profile equation of the rolling groove (21) on the surface of the cylindrical cam (2). The conversion relationship is z = x, R = y max 2π,θ=2π·y(x)y max ,y max It is the maximum value of the y-axis direction in the two-dimensional plane coordinate system (x, y); The two rollers (5) in the actuator undergo austenite transformation and martensite transformation respectively during a complete reciprocating motion of the driven arm (3), so there is y max =4·d max At the same time, θ should be calculated separately for each phase transformation stage. In the austenite phase transformation stage, the profile equation of the rolling groove (21) on the surface of the cylindrical cam (2) is: During the martensitic phase transformation stage, the profile equation of the rolling groove (21) on the surface of the cylindrical cam (2) is:

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