A micro-rotation mechanism based on shape memory alloy

Abstract

The present invention discloses a micro-rotation mechanism based on shape memory alloy, which is mainly composed of a fixed sleeve and a rotating shaft, and is characterized in that: the outer surface of the rotating shaft is respectively provided with a first wire and a second wire along the circumferential direction, the first end of the first wire and the first end of the second wire are respectively fixed on the rotating shaft and the distance between the two fixed points is less than 5% of the circumference of the rotating shaft, the first wire and the second wire are respectively rotated around the rotating shaft in reverse, and are respectively led out and fixed through the fixed sleeve, so that the first wire and the second wire are in a pulling state; the first wire is a shape memory alloy wire working in a shape memory state, and the second wire is a shape memory alloy wire in a superelastic state; a constant current power supply is connected between the two ends of the first wire. The present invention is suitable for completing a small range of rotation in a narrow space, and can be applied in medical surgery, micro-mechanism control, etc.; it is convenient to control the specific position of the rotation, and there is no working noise.

Description

Technical Field

[0001] The invention relates to a rotation driving mechanism, in particular to a micro rotation mechanism for realizing small-range rotation in a small space. Background Art

[0002] A rotating mechanism is a device that enables the driven mechanism to complete a certain rotation or twisting action, and rotate from a first position relative to a fixed object to a second position. Rotating mechanisms are used in many occasions. For example, the rotation of a robotic arm is generally controlled by a servo motor to control the rotation of the joint gears, and the amplitude of the rotation is generally determined by the coaxial photoelectric encoder installed on the servo motor; for another example, the angle adjustment of a surveillance camera, the motor rotates to drive the gear mechanism to rotate the camera's viewing angle to obtain the desired surveillance image; another example is a prosthetic limb for the disabled, in order to help people who have lost their arms complete their arm movements, the rotation of the joints is also driven by the motor to drive the gear rotation mechanism, and ultimately help complete the required action.

[0003] The advantages of this type of motor-driven rotating mechanism are high speed and great power, but the disadvantages are complex structure, large installation space required, and troublesome installation. It is impossible to complete the control task in a small space, and there will be a certain amount of noise.

[0004] In some applications, such as medical surgery and micro-mechanism control, the available installation space for the rotating mechanism is only a few millimeters. To complete a small range of rotation in such a narrow space, the existing motor drive method is usually difficult to achieve. Therefore, it is necessary to find a new micro-rotating mechanism. Summary of the invention

[0005] The purpose of the present invention is to provide a micro-rotation mechanism based on shape memory alloy, which can realize rotation drive in a small space through structural design.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a micro-rotation mechanism based on shape memory alloy, mainly composed of a fixed sleeve and a rotating shaft, the outer surface of the rotating shaft is respectively provided with a first wire and a second wire along the circumferential direction, the first end of the first wire and the first end of the second wire are respectively fixed on the rotating shaft and the distance between the two fixed points is less than 5% of the circumference of the rotating shaft, the first wire and the second wire are respectively rotated around the rotating shaft in reverse directions, and are respectively led out and fixed through the fixed sleeve, so that the first wire and the second wire are in a pulling state; the first wire is a shape memory alloy wire working in a shape memory state, and the second wire is a shape memory alloy wire in a superelastic state; a constant current power supply is connected between the two ends of the first wire.

[0007] In the above technical scheme, shape memory alloy is used to make the first wire and the second wire in different states respectively. Shape memory alloy is a new type of functional material, and the most commonly used one is Ni-Ti alloy, which is smelted and heat treated according to a certain ratio. At a certain temperature, it is deformed, heated, and cooled within a specified range according to the required requirements. It can reflect the characteristics of various shape changes and shape recovery, which are usually called shape memory effect and superelasticity. The actual internal structure is the transformation change between martensite and austenite. When heated to the characteristic temperature, that is, the end temperature of the austenite phase transformation, it can be restored to the state before stretching and output force and displacement to the outside. Superelasticity refers to the linear elasticity characteristics within a certain tension range when the current temperature is greater than the end temperature point of the austenite transformation. The present invention uses a shape memory alloy wire in a shape memory state as the first wire and a shape memory alloy wire in a superelastic state as the second wire. The two are arranged in reverse to form a pulling state. The alloy in the shape memory state overcomes the wire shaft in the elastic state and rotates clockwise, and the wire in the elastic state overcomes the alloy shaft in the shape memory state and rotates counterclockwise. The shape memory state is an active control wire, and the control of the rotation axis is achieved by controlling the shape memory state wire.

[0008] A further technical solution is that a voltage measuring module is connected between the two ends of the first wire, and a control module is provided. The output of the voltage measuring module is connected to the input of the control module. The current resistance value of the first wire is obtained according to the detected voltage value, and the rotation position is controlled by controlling the output current value of the constant current power supply.

[0009] In a preferred technical solution, a circumferentially arranged mounting groove is provided on the surface of the rotating shaft, the first wire and the second wire are respectively located in the mounting groove, and the surfaces of the first wire and the second wire are respectively coated with an insulating layer. This ensures that the wire is in the mounting groove and will not deviate during the stretching and contraction process.

[0010] In a further technical solution, the rotating shaft is a conductive rotating shaft, the fixed sleeve is an insulating sleeve, the first wire and the rotating shaft are electrically connected at a fixed point, one end of the constant current power supply is electrically connected to the rotating shaft, and is connected to the other end of the constant current power supply via the rotating shaft, the first end of the first wire, the first wire, and the second end of the first wire to form a current loop. The rotating shaft is used to output current, which facilitates circuit connection.

[0011] According to a further technical solution, the rotating shaft is a cylindrical structure with a step, and the inner hole of the fixed sleeve has a step that matches the shape and size of the rotating shaft, which limits the rotating shaft in the axial direction so that only relative rotation occurs between the rotating shaft and the fixed sleeve.

[0012] In the above technical solution, the length of the first wire is not less than 8 times the circumference of the rotating shaft, and the length of the second wire is not less than 8 times the circumference of the rotating shaft.

[0013] In the above technical solution, two axially arranged wire lead-out grooves are provided on the inner wall of the fixed sleeve, and the first wire and the second wire are respectively led out through the wire lead-out grooves; the first wire and the second wire can slide between the corresponding wire lead-out groove bodies, and the tail ends of the first wire and the second wire are respectively fixedly connected to the fixed sleeve.

[0014] Alternatively, the fixing sleeve is provided with two axially arranged wire lead-out holes, and the first wire and the second wire are respectively led out through the wire lead-out holes; the first wire and the second wire can slide between the corresponding wire lead-out holes, and the tail end of the first wire and the tail end of the second wire are respectively fixedly connected to the fixing sleeve.

[0015] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0016] 1. The present invention creatively adopts two states of shape memory alloy wire to form a pulling force, thereby realizing the rotation drive of small-sized components. It is suitable for completing a small-range rotation mechanism in a narrow space with a diameter of several mm, and can be used in medical surgery, micro-mechanism control, etc.;

[0017] 2. By utilizing the linear relationship between the resistance and displacement of the shape memory alloy, the present invention can conveniently control the specific position of the rotation without the need for an additional position sensor;

[0018] 3. Since no motor is used, the rotating mechanism of the present invention has no working noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of an embodiment of the present invention;

[0020] Figure 2 yes Figure 1 A schematic diagram of the structure observed through the fixed sleeve;

[0021] Figure 3 yes Figure 2 Schematic diagram of the dorsal direction;

[0022] Figure 4 It is a schematic diagram of the working principle of the embodiment;

[0023] Figure 5 It is the resistance-displacement characteristic diagram of shape memory alloy wire.

[0024] Wherein: 1. fixed sleeve; 2. rotating shaft; 3. first wire; 4. second wire; 5. constant current power supply; 6. wire lead-out slot / hole. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0026] Example 1: See Figures 1 to 3 As shown, a micro-rotation mechanism based on shape memory alloy is mainly composed of a fixing sleeve 1 and a rotating shaft 2. The surface of the rotating shaft 2 is provided with circumferentially arranged mounting grooves, and the first wire 3 and the second wire 4 are respectively arranged in the grooves. The first end of the first wire 3 and the first end of the second wire 4 are respectively fixed on the rotating shaft and the distance between the two fixed points is less than 5% of the circumference of the rotating shaft. The first wire 3 and the second wire 4 are respectively rotated around the rotating shaft 2 in the opposite direction, and are respectively led out and fixed through the fixing sleeve 1, so that the first wire 3 and the second wire 4 are in a pulling state; the first wire 3 is a shape memory alloy wire working in a shape memory state, and the second wire 4 is a shape memory alloy wire in a superelastic state. The surfaces of the first wire and the second wire are respectively coated with insulating layers; a constant current power supply 5 is connected between the two ends of the first wire 3.

[0027] In this embodiment, the rotating shaft is a conductive rotating shaft with a step (for example, a metal rotating shaft can be used), the fixed sleeve is an insulating sleeve, the inner hole of the fixed sleeve has a step that matches the shape and size of the rotating shaft, and the rotating shaft is limited in the axial direction, so that only relative rotation occurs between the rotating shaft and the fixed sleeve. The first wire and the rotating shaft are electrically connected at a fixed point, one end of the constant current power supply is electrically connected to the rotating shaft, and is connected to the other end of the constant current power supply through the rotating shaft, the first end of the first wire, the first wire, and the second end of the first wire to form a current loop. The output current of the rotating shaft is used to facilitate circuit connection.

[0028] Since the length contraction of general shape memory alloys is 4-6%, a certain length is required to complete the contraction and rotation. Therefore, in this embodiment, two axially arranged wire lead-out grooves / holes 6 are provided on the inner wall of the fixed sleeve 1. The first wire 3 and the second wire 4 are respectively led out through one of the wire lead-out grooves / holes 6, and can be telescopically slid in the wire lead-out grooves / holes. The tail ends of the first wire 3 and the second wire 4 are fixedly connected to the fixed sleeve 1. As a result, the retractable length of the first wire and the second wire becomes longer, and the rotatable angle of the rotating shaft becomes larger. In this embodiment, the length of the retractable part of the first wire and the second wire is 10 times the circumference of the rotating shaft, so that the rotation angle of the rotating shaft can reach 180 degrees. Among them, the wire lead-out groove / hole 6 can be a groove on the inner wall or a hole on the wall of the fixed sleeve according to the structural setting of the fixed sleeve, or, for a step structure, it can be a section of a slot body and a section of a through hole connected.

[0029] Figure 4: is a schematic diagram of the working principle of this embodiment. In this embodiment, a constant current power supply and a voltage measuring module are respectively connected between the rotating shaft and the second end of the first wire, and an MCU with an analog-to-digital conversion function is provided as a control module (the voltage measuring module and the control module can be implemented by an integrated circuit as needed). The output of the voltage measuring module is connected to the input of the control module, and the current resistance value of the first wire is obtained according to the detected voltage value, and the rotation position is controlled by controlling the output current value of the constant current power supply.

[0030] See attached Figure 5 As shown in the figure, the resistance-displacement characteristics of the shape memory alloy wire material indicate that there is a specific linear relationship between the resistance and length deformation displacement of the shape memory alloy wire material, so the current wire expansion and contraction amount can be obtained by measuring the resistance change value of the current wire material, thereby obtaining the current rotation position and realizing precise position control. The wire material obtains energy and generates heat, reflecting the shape memory effect. At the same time, the voltage at both ends of the wire material is sent to a microprocessor with an analog-to-digital conversion function to measure the voltage, obtain the current wire material resistance value, obtain the position value of the unit shaft, and then control the constant current source to control the final rotation position.

Claims

1. A micro-rotation mechanism based on shape memory alloy, mainly composed of a fixed sleeve and a rotating shaft, characterized in that: The outer surface of the rotating shaft is provided with a first wire and a second wire respectively along the circumferential direction, the first end of the first wire and the first end of the second wire are respectively fixed on the rotating shaft and the distance between the two fixed points is less than 5% of the circumference of the rotating shaft, the first wire and the second wire are respectively rotated around the rotating shaft in reverse directions, and are respectively led out and fixed through the fixing sleeve, so that the first wire and the second wire are in a pulling state; the first wire is a shape memory alloy wire working in a shape memory state, and the second wire is a shape memory alloy wire in a superelastic state; a constant current power supply is connected between the two ends of the first wire; A voltage measuring module is connected between the two ends of the first wire, and a control module is provided, the output of the voltage measuring module is connected to the input end of the control module, the current resistance value of the first wire is obtained according to the detected voltage value, and the rotation position is controlled by controlling the output current value of the constant current power supply; The rotating shaft is a cylindrical structure with steps, and the inner hole of the fixed sleeve has a step that matches the shape and size of the rotating shaft, which limits the rotating shaft in the axial direction so that only relative rotation occurs between the rotating shaft and the fixed sleeve.

2. The micro-rotation mechanism based on shape memory alloy according to claim 1, characterized in that: A circumferentially arranged mounting groove is provided on the surface of the rotating shaft, the first wire and the second wire are respectively located in the mounting groove, and the surfaces of the first wire and the second wire are respectively covered with an insulating layer.

3. The micro-rotation mechanism based on shape memory alloy according to claim 2, characterized in that: The rotating shaft is a conductive rotating shaft, the fixed sleeve is an insulating sleeve, the first wire and the rotating shaft are electrically connected at a fixed point, one end of the constant current power supply is electrically connected to the rotating shaft, and is connected to the other end of the constant current power supply through the rotating shaft, the first end of the first wire, the first wire, and the second end of the first wire to form a current loop.

4. The micro-rotation mechanism based on shape memory alloy according to claim 1, characterized in that: The length of the first wire is not less than 8 times the circumference of the rotating shaft, and the length of the second wire is not less than 8 times the circumference of the rotating shaft.

5. The micro-rotation mechanism based on shape memory alloy according to claim 1, characterized in that: Two axially arranged wire lead-out grooves are provided on the inner wall of the fixed sleeve, and the first wire and the second wire are respectively led out through the wire lead-out grooves; the first wire and the second wire can slide between the corresponding wire lead-out groove bodies, and the tail end of the first wire and the tail end of the second wire are respectively fixedly connected to the fixed sleeve.

6. The micro-rotation mechanism based on shape memory alloy according to claim 1, characterized in that: The fixing sleeve is provided with two axially arranged wire lead-out holes, through which the first wire and the second wire are respectively led out; the first wire and the second wire can slide between the corresponding wire lead-out holes, and the tail end of the first wire and the tail end of the second wire are respectively fixedly connected to the fixing sleeve.

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