Differential magnetic control inchworm linear actuator and driving method

Abstract

The application discloses a differential magnetic control shape memory alloy inchworm linear driver and a driving method. Two magnetic control shape memory alloy driving elements with the same shape size and magnetic control characteristics are adopted, the displacement of the magnetic control shape memory alloy driver is borne through a piezoelectric ceramic block, and inchworm crawling is realized through differential driving with another piezoelectric ceramic block. Through the application of the application, the output energy density and response frequency of the precision driver are effectively improved, the precision driver is resistant to shock and impact, and the reliability is high.

Description

Technical Field

[0001] This invention relates to a differential magnetically controlled shape memory alloy inchworm linear actuator and driving method, belonging to the field of precision drive technology. Background Technology

[0002] High-power-density, wide-bandwidth, long-stroke precision drives are an important area of ​​research. Smart materials, with their high energy density and fast response frequency, are expected to become key materials for next-generation drives. In particular, magnetron-controlled shape memory alloys combine the advantages of large deformation and high response frequency.

[0003] Magnetically controlled shape memory alloys (MCUs) are functional materials driven by magnetic fields. Discovered around 2000, they undergo a martensitic phase transformation upon cooling, exhibiting all the properties of traditional temperature-controlled shape memory alloys. Furthermore, the martensitic variants in MCUs can be rearranged under the influence of an applied magnetic field, displaying macroscopic strain similar to magnetostriction. Therefore, MCUs not only possess the large strain and high driving force characteristics of ordinary temperature-controlled shape memory alloys but also exhibit the high response frequency of supermagnetic-strictive materials, showing immense application potential.

[0004] The deformation of smart materials is generally less than millimeters. To achieve large-scale actuation, smart material actuators designed based on the inchworm principle employ a cyclic stepping method to continuously accumulate deformation and achieve a larger output stroke. According to the guiding layout, inchworm actuators can be divided into two main categories: crawling and propulsion. The crawling inchworm actuator's displacement output mechanism (mover) generally consists of clamping mechanisms on both sides and a central driving element. When moving to the right: the left clamp tightens, the right clamp relaxes; the driving element extends, and the mover moves forward one step; the right clamp tightens, the left clamp relaxes; the driving element returns to its original length, the left clamp tightens, the right clamp relaxes, and the initial state is restored. The basic stepping principle of the propulsion inchworm actuator is similar to that of the crawling type, but the difference is that in the crawling actuator, the driving element is a mover, while in the propulsion actuator, the driving element is a stator. The driving element pushes an output rod (spindle) to output displacement.

[0005] An inchworm actuator typically consists of a driving element, a flexible hinge, a clamping mechanism, and a base guide rail. The driving element and the clamping mechanism are two key design elements: (a) In the design of the driving element, for smart materials with reciprocating driving capabilities, such as piezoelectric ceramics, the reset of the driving element after deformation can be achieved by changing the sign of the external electric field. For smart materials without reciprocating driving capabilities, such as magnetostrictive materials, temperature-controlled shape memory alloys, and magnetostrictive shape memory alloys, a restoring spring is generally required to achieve the reset of the driving element after deformation. However, the spring mechanism has a slow recovery speed and is only suitable for applications where dynamic performance requirements are not high. (b) In the design of the clamping mechanism, there are generally two design schemes: active clamping and passive clamping. Active clamping relies on friction between the clamping surface and the guide rail surface for clamping force. It is simple in structure and has a fast response, but the clamping force is small. Passive clamping relies on wedge self-locking, providing stable clamping and generating a larger clamping force, but it has a slow response, is difficult to self-lock, and only supports unidirectional drive. Given the requirements for fast response, high output force, and compact structure in drive mechanisms, existing design methods for drive components and clamping mechanisms are insufficient. Breakthroughs in high-frequency reciprocating drive and high-output clamping design are urgently needed. Summary of the Invention

[0006] The problem solved by this invention is to overcome the shortcomings of the prior art and propose a differential magnetically controlled shape memory alloy inchworm linear actuator and driving method. By using an interference fit and a clearance fit between the piezoelectric ceramic block and the magnetic flux element, the piezoelectric ceramic block carries the displacement driven by the magnetically controlled shape memory alloy, enabling the actuator to perform inchworm crawling, thereby improving the output energy density, response frequency, and reliability.

[0007] The present invention solves the above-mentioned technical problem through the following technical solution:

[0008] A differentially magnetically controlled shape memory alloy linear actuator for inchworms includes a stator and a mover;

[0009] The stator is a magnetic flux element, including a first magnetic flux module and a second magnetic flux module;

[0010] The mover is placed between the first magnetic flux module and the second magnetic flux module and can move up and down relative to the first magnetic flux module and the second magnetic flux module; the mover achieves linear motion by switching between clearance fit and interference fit with the two magnetic flux modules.

[0011] Preferably, the mover includes an excitation coil, a magnetic shielding frame, a permanent magnet, a magnetically controlled shape memory alloy element, a piezoelectric ceramic block, and an output shaft;

[0012] The first excitation coil group and the second excitation coil group are wound on the first magnetic flux module and the second magnetic flux module respectively, generating an alternating magnetic field with opposite directions at the same time.

[0013] The magnetic shielding frame is fixed between the first excitation coil group and the second excitation coil group;

[0014] The upper surface of the first magnetically controlled shape memory alloy element is fixed to the upper surface inside the magnetically shielded frame, and the lower surface of the second magnetically controlled shape memory alloy element is fixed to the lower surface inside the magnetically shielded frame.

[0015] The lower surface of the first permanent magnet is fixed to the upper surface of the magnetic shielding frame, and the upper surface of the second permanent magnet is fixed to the lower surface of the magnetic shielding frame. The magnetic poles of the two permanent magnets face the same direction after installation.

[0016] The first piezoelectric ceramic block is fixed between the two magnetized shape memory alloy elements, and the upper surface of the second piezoelectric ceramic block is fixed to the lower surface of the second permanent magnet.

[0017] The lower surface of the output shaft is fixed to the upper surface of the first permanent magnet.

[0018] Preferably, the two magnetic flux elements only have contact with the two piezoelectric ceramic blocks in the mover; by supplying power to the piezoelectric ceramic blocks, the switch between clearance fit and interference fit between the piezoelectric ceramic and the magnetic flux elements can be realized.

[0019] Preferably, it also includes a controller to control the power supply and disconnection of the first excitation coil group, the second excitation coil group, the first piezoelectric ceramic block, and the second piezoelectric ceramic block.

[0020] Preferably, the first excitation coil group and the second excitation coil group are connected in series, and the winding directions of the two coil groups around the magnetic flux element are opposite.

[0021] Preferably, the first excitation coil group and the second excitation coil group are connected in parallel, and when power is supplied, the two coil groups are wound in the same direction.

[0022] Preferably, the ratio of the single-sided distance between each piezoelectric ceramic block and the magnetic flux element to the distance between the two magnetic flux elements is no greater than 1:1000.

[0023] Preferably, the inchworm linear actuators can be used in combination, depending on the required linear drive power.

[0024] Preferably, the second piezoelectric ceramic block is fixed between the lower surface of the first permanent magnet and the upper surface of the magnetic shielding frame.

[0025] A driving method for a linear actuator of an inchworm using a differentially magnetically controlled shape memory alloy includes:

[0026] Power is supplied to the two excitation coil groups and the second piezoelectric ceramic block, so that the second piezoelectric ceramic block is interference-fitted with the magnetic flux element, and the two magneto-controlled shape memory alloy elements push the first piezoelectric ceramic block to move downward.

[0027] After energizing the first piezoelectric ceramic block to make it interference fit with the magnetic flux element, de-energize the second piezoelectric ceramic block.

[0028] After the magnetic field direction of the two excitation coil groups changes, the two magnetically controlled shape memory alloy elements use the reaction force of pushing the first piezoelectric ceramic block to drive the two excitation coil groups, the magnetic shielding frame, the two permanent magnets, the two magnetically controlled shape memory alloy elements, the two piezoelectric ceramic blocks, and the output shaft to move upward.

[0029] When the output shaft has moved upward, power is supplied to the second piezoelectric ceramic block, so that the second piezoelectric ceramic block and the magnetic flux element are interference-fitted. Then the power is cut off to the first piezoelectric ceramic block, so that the first piezoelectric ceramic block and the magnetic flux element are clearance-fitted, thereby realizing the displacement superposition of the magnetically controlled shape memory alloy element.

[0030] The advantages of this invention compared to the prior art are:

[0031] (1) The present invention has a high output energy density, which is 40 times that of traditional piezoelectric ceramic materials and 3 times that of magnetostrictive materials. The deformation per unit time and per unit force is 5 to 10 times greater than that of traditional piezoelectric ceramics and magnetostrictive materials. At the same time, the present invention has high sensitivity and a response frequency of up to 1000 Hz.

[0032] (2) Except for the relative translation between the stator and the mover, all the mover components of this invention are fixedly connected, without rotation or multi-link mechanical structures, making it shock resistant, impact resistant and highly reliable.

[0033] (3) The present invention utilizes the material’s own expansion and contraction characteristics, combined with the tolerance zone, to achieve displacement accumulation. Attached Figure Description

[0034] Figure 1 This is a structural diagram of a differential magnetically controlled shape memory alloy inchworm linear actuator according to an embodiment of the present invention. Specific implementation methods

[0035] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] This invention proposes a differential magnetically controlled shape memory alloy (MCU) linear actuator for inchworms, consisting of a stator and a mover, wherein the mover employs differential drive. The differential MCU actuator uses two MCU driving elements with identical shape, size, and magnetic control characteristics. The inchworm linear actuator uses a piezoelectric ceramic block to support the displacement of the MCU actuator, and the inchworm crawls through differential drive with the other piezoelectric ceramic block.

[0037] The inchworm linear actuator includes a magnetic flux element, an excitation coil, a magnetic shielding frame, a permanent magnet, a magnetically controlled shape memory alloy element, a piezoelectric ceramic block, and an output shaft. The excitation coil, magnetic shielding frame, permanent magnet, magnetically controlled shape memory alloy element, piezoelectric ceramic block, and output shaft are fixedly connected to form a single unit, capable of vertical movement relative to the magnetic flux element. Only the piezoelectric ceramic block, powered by electricity, can switch between clearance fit and interference fit with the magnetic flux element. The single-sided mounting distance between the piezoelectric ceramic block and the magnetic flux element is 0.02mm~0.05mm, depending on the required drive power provided by the actuator. Generally, the ratio of the single-sided mounting distance between the piezoelectric ceramic block and the magnetic flux element to the distance between the two magnetic flux elements is no greater than 1:1000.

[0038] The magnetic flux element is fixed and only has contact with the piezoelectric ceramic block. The piezoelectric ceramic block switches between clearance fit and interference fit with the magnetic flux element via power supply. Figure 1 As shown, the two magnetic flux elements are the first magnetic flux module 101 and the second magnetic flux module 102, respectively.

[0039] The excitation coils are wound around the magnetic flux elements. The first excitation coil 201 and the second excitation coil 201 are wound around the first magnetic flux module 101 and the second magnetic flux module 102, respectively. They can move up and down along the magnetic flux elements, generating an alternating magnetic field with opposite directions at any given time. This magnetic field superimposes on the permanent magnet's own magnetic field, causing the magnitudes of the magnetic fields passing through the first and second magnetically controlled shape memory alloy elements 501 and 502 to differ and alternate, thus pushing the first piezoelectric ceramic block 601 to move up and down. The first and second excitation coils 201 can be connected in series or in parallel. When connected in series, the winding directions of the two coils must be opposite; when connected in parallel, the winding directions of the two coils must be the same. In practical applications, regardless of the number of turns in the two coils, they need to generate opposite magnetic fields to cancel or superimpose the magnetic field of the nearest permanent magnet. When the magnetic field strength of the upper and lower permanent magnets is the same, the maximum magnetic field strength of the two sets of coils is the same. If the magnetic field strength of the two permanent magnets is different, the maximum magnetic field strength of the two sets of coils can be different. The cost is that the dimensions of the two shape memory alloys will be inconsistent, and the shapes of the two piezoelectric ceramics will be inconsistent.

[0040] The magnetic shielding frame 300 has the characteristic of blocking the passage of magnetic fields. It is fixed between the two excitation coils so that magnetic field lines will not pass through the middle, thus blocking the magnetic field.

[0041] The permanent magnet can generate a fixed magnetic field and is fixedly connected to the magnetic shielding frame 300. The N-pole of the first permanent magnet 401 and the second permanent magnet 402 are connected to the first magnetic flux module 101, and the S-pole is connected to the second magnetic flux module 102. The lower surface of the first permanent magnet 401 is fixedly connected to the upper surface of the magnetic shielding frame 300, and the upper surface of the second permanent magnet 402 is fixedly connected to the lower surface of the magnetic shielding frame 300.

[0042] The magnetically controlled shape memory alloy element has enhanced lateral magnetic field, longitudinal elongation characteristics, high output energy density, high response frequency, and high deformation rate. The magnetically controlled shape memory alloy element is divided into a first magnetically controlled shape memory alloy element 501 and a second magnetically controlled shape memory alloy element B502. The upper surface of the first magnetically controlled shape memory alloy element 501 is fixed to the upper surface inside the magnetically shielding frame 300, and the lower surface of the second magnetically controlled shape memory alloy element 502 is fixed to the lower surface inside the magnetically shielding frame 300.

[0043] The piezoelectric ceramic block is divided into a first piezoelectric ceramic block 601 and a second piezoelectric ceramic block 602, both exhibiting lateral expansion and contraction characteristics after being energized. The first piezoelectric ceramic block 601 is fixedly connected between the magnetron-controlled shape memory alloy elements 500, and the upper surface of the second piezoelectric ceramic block 602 is fixedly connected to the lower surface of the magnetic shielding frame 300. In practical applications, the second piezoelectric ceramic block 602 can also be placed on the lower surface of the first permanent magnet 401 and the upper surface of the magnetic shielding frame 300.

[0044] The lower surface of the output shaft 700 is fixedly connected to the upper surface of the first permanent magnet 401.

[0045] The driving principle of this inchworm linear actuator is as follows: the excitation coil generates an alternating magnetic field, which is superimposed on the magnetic field of the permanent magnet itself, causing the magnetic field passing through the magnetically controlled shape memory alloy element 501 and the magnetically controlled shape memory alloy element 502 to be inconsistent in magnitude and alternate, thus driving the piezoelectric ceramic block to move up and down.

[0046] Specific driving methods include:

[0047] Power is supplied to the two excitation coil groups and the second piezoelectric ceramic block 602, so that the second piezoelectric ceramic block 602 is interference-fitted with the two magnetic flux elements, and the two magnetized shape memory alloy elements push the first piezoelectric ceramic block 601 to move downward.

[0048] Power on the first piezoelectric ceramic block 601 to make the piezoelectric ceramic block 601 and the two magnetic flux elements interference fit, and then de-power the second piezoelectric ceramic block 602.

[0049] After the magnetic field direction of the two excitation coils changes, the two magnetically controlled shape memory alloy elements use the reaction force of pushing the first piezoelectric ceramic block to drive the whole formed by the two excitation coils, the magnetic isolation frame 300, the two permanent magnets, the two magnetically controlled shape memory alloy elements, the two piezoelectric ceramic blocks, and the output shaft 700 to move upward.

[0050] When the upward movement is complete, power is supplied to the second piezoelectric ceramic block 602 so that the second piezoelectric ceramic block 602 is interference-fitted with the two magnetic flux elements. Then the power is de-energized to the first piezoelectric ceramic block 601 so that the first piezoelectric ceramic block 601 is gap-fitted with the two magnetic flux elements, thereby realizing the superposition of displacements of the two magnetically controlled shape memory alloy elements.

[0051] The embodiments described above are merely preferred embodiments of the present invention. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A differentially magnetically controlled shape memory alloy linear actuator for inchworms, characterized in that, Including stator and mover; The stator is a magnetic flux element, including a first magnetic flux module and a second magnetic flux module; The mover is placed between the first magnetic flux module and the second magnetic flux module, and can move up and down relative to the first magnetic flux module and the second magnetic flux module; the mover achieves linear motion by switching between clearance fit and interference fit with the two magnetic flux modules. The mover includes an excitation coil, a magnetic shielding frame, a permanent magnet, a magnetically controlled shape memory alloy element, a piezoelectric ceramic block, and an output shaft; The first excitation coil group and the second excitation coil group are wound on the first magnetic flux module and the second magnetic flux module respectively, generating an alternating magnetic field with opposite directions at the same time. The magnetic shielding frame is fixed between the first excitation coil group and the second excitation coil group; The upper surface of the first magnetically controlled shape memory alloy element is fixed to the upper surface inside the magnetically shielded frame, and the lower surface of the second magnetically controlled shape memory alloy element is fixed to the lower surface inside the magnetically shielded frame. The lower surface of the first permanent magnet is fixed to the upper surface of the magnetic shielding frame, and the upper surface of the second permanent magnet is fixed to the lower surface of the magnetic shielding frame. The magnetic poles of the two permanent magnets face the same direction after installation. The first piezoelectric ceramic block is fixed between the two magnetized shape memory alloy elements, and the upper surface of the second piezoelectric ceramic block is fixed to the lower surface of the second permanent magnet. The lower surface of the output shaft is fixed to the upper surface of the first permanent magnet.

2. The differential magnetically controlled shape memory alloy inchworm linear actuator according to claim 1, characterized in that, The two magnetic flux elements are in contact only with the two piezoelectric ceramic blocks in the mover; by supplying power to the piezoelectric ceramic blocks, the gap fit and interference fit between the piezoelectric ceramic and the magnetic flux elements can be switched.

3. The differential magnetically controlled shape memory alloy inchworm linear actuator according to claim 1, characterized in that, It also includes a controller to control the power supply and disconnection of the first excitation coil group, the second excitation coil group, the first piezoelectric ceramic block, and the second piezoelectric ceramic block.

4. The differential magnetically controlled shape memory alloy inchworm linear actuator according to claim 1, characterized in that, The first excitation coil group and the second excitation coil group are connected in series, and the winding directions of the two coil groups around the magnetic flux element are opposite.

5. A differential magnetically controlled shape memory alloy inchworm linear actuator according to claim 1, characterized in that, The first excitation coil group and the second excitation coil group are connected in parallel. When power is supplied, the two coil groups are wound in the same direction.

6. A differential magnetically controlled shape memory alloy inchworm linear actuator according to claim 1, characterized in that, The ratio of the single-sided distance between each piezoelectric ceramic block and the magnetic flux element to the distance between the two magnetic flux elements is no greater than 1:1000.

7. A driving method for a differentially magnetically controlled shape memory alloy inchworm linear actuator, employing the differentially magnetically controlled shape memory alloy inchworm linear actuator as described in claim 1, characterized in that... include: Power is supplied to the two excitation coil groups and the second piezoelectric ceramic block, so that the second piezoelectric ceramic block is interference-fitted with the magnetic flux element, and the two magneto-controlled shape memory alloy elements push the first piezoelectric ceramic block to move downward. After energizing the first piezoelectric ceramic block to make it interference fit with the magnetic flux element, de-energize the second piezoelectric ceramic block. After the magnetic field direction of the two excitation coil groups changes, the two magnetically controlled shape memory alloy elements use the reaction force of pushing the first piezoelectric ceramic block to drive the two excitation coil groups, the magnetic shielding frame, the two permanent magnets, the two magnetically controlled shape memory alloy elements, the two piezoelectric ceramic blocks, and the output shaft to move upward. When the output shaft has moved upward, power is supplied to the second piezoelectric ceramic block, so that the second piezoelectric ceramic block and the magnetic flux element are interference-fitted. Then the power is cut off to the first piezoelectric ceramic block, so that the first piezoelectric ceramic block and the magnetic flux element are clearance-fitted, thereby realizing the displacement superposition of the magnetically controlled shape memory alloy element.

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