Patent Application
20240229779
This application is a U.S. Nonprovisional application and claims priority to Indian Application No. 202211060660, filed on Oct. 21, 2022, which is incorporated herein by reference in its entirety.
The present invention generally relates to linear bi-directional actuators utilizing smart materials.
More particularly the present discloser specifically relates to the bi-directional linear actuator that employs the Shape Memory Alloy (SMA) material to provide the controlled stroke length displacement in reiteratively large number of cycles during the operation of the mechanical system. This invention provides forward and backword-controlled motion by the plurality of segments of the SMA elements with the plurality of rigid strip(s) arranged together in specific antagonistic configurations across the main stroke transmitting lever. The SMA material exhibits the Shape Memory Effect (SME) property while phase conversion at specific transformation temperatures. The SME property enables it to retain its predetermined shape that causes strain recovery along with a large tensile force which is suitable for driving an external mechanical actuation. Further, the invention includes a plurality of sub-modules consisting of SMA elements and rigid strip(s) with an electrical heating module. The compact design of the embodiments is achieved by the series cascading configuration of the part-modules. There are two design configurations such as the ‘straight’ and the ‘cross’ configuration of the segments of the SMA elements that deliver large stroke displacement in an additive manner. The operation of the discloser is controlled by any external logical programmable command and control signals applied from a standard external controller.
Actuators are an important and critical component that are widely used in almost all modern automation systems including industries, automobiles, defence, machineries, instruments, in computer peripherals such as disks and printers, and many other places where motion with actuation force is required. Commonly available linear actuators include diverse types of linear actuators such as hydraulic, pneumatic, piezoelectric, and electromagnetic actuators. These are available in different shape, size, output stroke displacement and force, and mostly operate by AC and/or DC power source. The widespread adaptation of electromagnetic actuators offers several limitations due to their complex mechanical design, attachment of gear assembly and rotation conversion mechanism to linear and angular motion, vibration, bulky and accommodation at the end application. In recent years, SMA based actuator systems have gained much popularity due to their remarkable properties such as high force-to-weight ratio, high strain recovery capability, large recovery force generation, lightweight, simpler mechanical design, compact size, exhibiting sizeable electrical resistance, good elasticity, and long fatigue life, thereby making SMA based actuator systems a highly appropriate choice for modern applications.
U.S. Pat. No. 6,762,515 B2, this patent describes the linear actuator wherein long stroke and actuation force is provide the by the SMA wire material, and the long stroke is achieved by stroke amplification of the multiple SMA wire elements connected thru the multiple bars or rods (sub-modules) in serial mechanical connection. In this and other SMA driven actuator system understood that the requirement of restoring force is necessary for resetting(extending) the SMA wire in cooled state after contraction due to heated state. Many stated priors are designed used common spring assembly like helical or leaf spring to exert the required restoring force. This and other patents and publications have been used one side active SMA wires for forward stroke and return the stroke by resetting spring. These springs produced restoring force varies linearly with displacement, (F=k*x), and restoring force is maximum when the stroke at maximum and this kind of restoring mechanism limited the useful life of the SMA actuator.
U.S. Pat. No. 6,832,477 B2, this embodiment SMA wire is used as the actuation elements in the forward direction due to heating and in the cooling state resetting of the SMA wire elements to their original length by the Intrinsic Return Means (IRM) not by any external resetting helical or leaf spring. The IRM means nothing, but the same SMA wire has been exhibiting the reversible shape memory effect which is also known as two-way shape memory effect of the material. The reversible shape memory effect of the material has shown limited strain recovery and resetting force and life span of shape memory effect is limited in cyclic manner.
US 2007/0175213 A1, this application seeks to provide a controller for improving the speed of the actuation of SMA actuator. The controller is regulating the heating current to the SMA actuator based on the intrinsic resistance variation of the SMA actuator. The controller generates control signals according to the monitored resistance variation of the SMA material.
EP patent no. 1300532 A1 of latch assembly describes the application of shape memory alloy wire for unlatching the sticker from latch assembly. Here SMA actuator is an integral part and housed inside of the latch assembly. SMA wire is mounted in returning spring biased arrangement to the pivotally moving pawl mechanism. SMA actuator energized by electrically which caused the contraction and rotated the pawl at the safety position to open and close the door. This invention relates to operation of the latch assembly but not shown the lock-unlock the striker.
EP patent no. 1279784 A1 motor vehicle door lock describes the application of the shape memory alloy actuator for releasing the striker from the door lock. Here SMA actuator is an integral part and housed inside of the lock assembly and provide the rotatory movement to catch element through release lever. The contraction force by SMA is used for movement of release lever for releasing the sticker from catch elements. This invention is related to the operation of the lock assembly for unlatching operation.
EP patent no. 1245762 A1 describes the application of the shape memory alloy actuator for opening the door lock/latch. The SMA wires worked as mechanical transmission elements between the doors lock and control device. The control device located at a distance from the lock, a mechanical transmission link which connects the control device to the lock, shape memory actuator being arranged in between as a mechanical transmission link, externally with respect to the lock, in such a way that the lock can be opened by actuation of the shape memory actuator, operated by the control device, in which case the shape memory actuator acts simply as a mechanical device belonging to transmission link.
U.S. Pat. No. 8,398,128 B2, describes a vehicle door latch system configured to temporarily prevent door latch mechanisms from unlatching during a predetermined event is provided. It has fork-bolt pivotally mounted arrangement for moving between a latching position and an unlatching position. The movement of fork-bolt is restricted by block out mechanism. This block out mechanism configured for movement between a blocking position and an unblocking position. The movement of block out mechanism is activated by the SMA wire and biased spring between blocking and unblocking position. Here also the SMA is integral part and housed inside of the latch system to provide the movement for blocking position.
By reference to U.S. Pat. No. 6,481,821 B1 discloses an actuator for an ink jet printer head using a shape memory alloy which includes a lower space part; a silicon substrate where said lower space part is formed; an insulating film formed on said silicon substrate surface and made of a silicon oxide film which acts to push the shape memory alloy film to nozzle side direction and a silicon nitride film which acts to pull the shape memory alloy film in a direction opposite to nozzle side; and a shape memory alloy layer formed upon said insulation film so as to cover said lower space part.
By reference to KR Patent application number KR 100366652 B1 discloses a silicon substrate on which the lower space portion is formed; It consists of silicon nitride film that pulls the thin film of shape memory alloy in the direction opposite to the nozzle direction, or the silicon oxide film and the shape memory alloy thin film pulls in the opposite direction to the nozzle direction. An insulating film formed on a surface of the silicon substrate, the silicon nitride film having a function of pulling the film.
The above information disclosed is only for enhancement of understanding of the background of the invention. Despite the large interest in SMA-based actuators identified in the prior art, none of the practical actuators have been shown to provide control stroke displacement using of SMA material in both forward and backward directions for large number of cycles. It is understood that the SMA material requires external bias force for restarting its quiescent length during the cooling cycle, and most designers in the prior art employed an external bias steel spring for resetting quiescent length. However, these configurations generate a variable force and extreme at maximum stroke displacement that causes degradation of the useful life and force-displacement chrematistics. This limitation has been addressed in several prior arts by appropriate biasing configuration to reset the SMA. Another limitation observed is to accommodate the useful length of SMA wire by wrapping over the pulleys for compacting the device, however, the curvature in the SMA by pulleys causes uneven contraction and expansion that results in a reduction in stroke displacement and generated force as not observed in the case of straight SMA wire. It would be desirable to develop an SMA-based actuator that can provide a substantial magnitude of actuation force while achieving maximum stroke length displacement in a compact design of antagonistic configuration using straight SMA wire elements.
The main objective of the present invention is to provide a novel actuation device comprises of the shape memory alloy (SMA) components as an actuator element.
Another objective of the present invention is to provide the stroke displacement in bidirectional i.e. back and forth (forward & reverse) directions with actuation force.
Another objective of the present invention is to provide the actuation by the SMA material that represented shape memory effect (SME) at specific transformation temperatures.
Another objective of the present invention is to provide bidirectional movement by the plurality of the SMA element(s) in wire form arranged in antagonistic configuration.
Another objective of the present invention is to arrange the segments of the SMA element(s) in the part-modules and to arrange part-modules at both sides of the main stroke transmitting lever.
Another objective of the present invention is to provide a device that comprises part modules and main stroke transmitting lever arranged in linear additive stroke configuration.
Another objective of the present invention is to provide the device that part-modules comprises of rigid strips with plurality of segment of the SMA elements and main stroke transmitting lever.
Another objective of the present invention is to provide mounting orientation of the part-modules along with main stroke transmitting lever are either in width direction or in height direction to miniaturized of actuator dimensions and constant volumetric size.
Another objective of the present invention is to develop the part-modules by the rigid strips and segments of the SMA elements are attached at the ends to the strip by laser or spot electric welding method.
Another objective of the present invention is to develop the actuator device by the plurality of part-modules are attached in such a way to the next neighbouring part modules in serial mechanical cascading configuration for generating additive stroke displacement.
Another objective of the present invention is to provide the resultant full stroke length at the main stroke transmitting lever by the additive summation of the stroke produced by each part-module(s).
Another objective of the present invention is to provide the rigid strips are electrically conductive to provide the path of electrical current flow in it or non-conducting strips that has provision to maintain the path of electrical current flow through it with attached segments of the SMA elements.
Yet another objective of the present invention is to provide bidirectional (back and forth) linear and binary segmented SMA actuator find extensive applications in industrial, domestic, commercial, automobile, aero-space, automation & control, appliance, safety & security, 3D printer head motion & positioning, prosthetic, robotic and electronics industries. Further, the binary positional back and forth applications of the actuator are widely ranging from door lock-unlock, automobile latch-unlatch, windshield wipers motion and directional air flow of wind blower motions, rear view mirror adjustment in automobiles to pin pullers and shutter controllers of space mechanical design actuation.
This summary is provided to introduce a selection of concepts, in a simplified format, that are further described in the detailed description of the disclosure. This summary is neither intended to identify key or essential inventive concepts of the disclosure nor is it intended for determining the scope of the disclosure.
The main aspect of the invention provides a Bidirectional, Linear and Binary Segmented Antagonistic Servomechanism-based Shape Memory Alloy (SMA) actuator comprising a main stroke transmitting lever and a plurality of part-modules disposed in a closely spaced arrangement and adapted to undergo a reciprocal translation in a first direction. The part-modules comprising a plurality of the segments of the SMA elements, further, the part-modules are connected with the adjacent part-modules and main stroke transmitting lever, and each segment of the SMA element extending longitudinally in the first direction.
In another aspect of the invention provides a plurality of part-modules, which are developed by the segments of the SMA elements in wire or strip shape, and rigid metallic/non-metallic strips. These part modules are arranged in an antagonistic configuration at both sides of the main transmitting level that delivers long stroke displacement during forward and backward movement. The embodiment employs the Nitinol shape memory material and its shape memory effect property, which is entirely dependent on external temperature stimuli. The linear actuator is designed for repetitive operation with safe strain recovery of up to 8% that delivers long stroke displacement with significant force generated upon heating of the SMA wire element above well-defined phase transition temperature. It relaxes when cooled below the phase transition temperature. The shape memory effect is also expressed by the different metallic alloys that can use in place of Nitinol with appropriate temperature stimuli.
In another aspect of the invention, the segment of the SMA element is working with a specific predetermined transition temperature of 70-90° C. The phase transformation temperature varies depending on the alloy's chemical composition; and material selection criteria depends on the operating conditions and end applications of linear actuator. It observes that the SMA-based linear actuator requires restoring force for resetting the quiescent length when the transformation temperature falls below the martensitic phase transition temperature.
In another aspect of the invention provide an antagonistic configuration of part modules comprising the segment of the SMA elements. The novel arrangement generates a time-varying recovery force during phase transformation from martensitic to austenitic that utilizes as a bias resetting force on the opposite side part module segment of the SMA elements. Time-varying bias resetting force is effective when the one side segments of the SMA elements are in the martensitic phase and the opposite side segments of the SMA elements are gradually transforming from martensitic to the austenitic phase. The process repeats on the other side part-module when the operating conditions are reversed, and process repeats of resetting in the next cycle and vice-versa.
In another aspect of the invention, the operation of the invented linear actuator is controlled by pulses of electrical energy or train of Pulse Width Modulation (PWM) control signal with a suitable electrical power source. The magnitude of applied electrical power regulates different parameters such as total stroke length displacement, net actuation force generation, response time, operating speed, and working bandwidth of the embodiment.
In another aspect of the invention provide actuator that comprises a plurality of part-modules that are interconnected in series cascading arrangements to provide total stroke length displacement by an additive summation of individual part-module stroke length. The part-module dimensions, in length and width, are confined to maintain the size miniaturization of the linear actuator assembly. The part-module designs are such that they are serially cascaded either on the horizontal side or on the vertical side of the present embodiment. The serial cascading of the part-modules provide design flexibility to the end users in terms of mounting space at the application site. The main stroke transmitting lever is suitably located in the embodiment that provides the total stroke length with net generated actuation force for external actuation.
In another aspect of the invention provide part-modules in two different innovative formations with the main stroke transmitting lever. In the first formation, the part-modules are arranged at both sides of the main transmitting lever with a ‘straight’ configuration of the segments of the SMA elements and in the second formation, part-modules are arranged at one side of the main transmitting lever with a ‘cross’ configuration of the segments of the SMA elements. The main stroke transmitting lever assembly comprises of main stroke transmitting lever, and segments of the SMA elements are welded at the curve ends of the lever. The main stroke transmitting lever is developed by a pair of strips, joined firmly with the sandwiching of an insulating strip. The strips are joined in a particular orientation that forms the ‘S-type long tail’ and ‘flipped F-type long tail’ type structures of the main stroke transmitting lever. In another aspect of the invention, the rigid strips are made of conducting or non-conducting materials. In the case of non-conducting strips used, a suitably electrical continuity is provided between the end points with welding post for the SMA elements. The segments of the SMA elements are developed by crimping of metallic ferrule. The ‘straight’ configuration of part-module is developed by welding of two segments of the SMA elements on the ends of rigid ‘S-type’ conducting/non-conducting strip. The ‘cross’ configuration of part-module is developed by ‘S-type’ & ‘flipped S-type’ rigid strips are joined together with an insulating strip sandwich between them to form an ‘I-section type’ structure. The four segments of the SMA elements are welded in a ‘cross’ configuration at the ends of the ‘I-section type’ structure. Any suitable welding method such as laser or electric spot-welding method can be used to weld at the end points of strips, avoiding any degradation of SMA material properties. The expansion of the linear actuator is further possible in either horizontal or vertical direction by attaching of the next part-modules at the end of the previous part-module.
In another aspect of the invention, all the part-modules are connected in a serial mechanical cascading arrangement to form the SMA link that provide series electrical conducting path for flowing of heating current through the segments of the SMA elements. The electrical current produces a joule heating to each of the segments of the SMA elements in the link that causes phase transformation due to rise in temperature. The phase transformation causes contraction (strain recovery) in each of the segment of the SMA elements which are connected in serial mechanical arrangements. Therefore, the net stroke length is the addition of each strain recovery from each segment of the SMA element. The linear actuator produces net stroke length displacement with the equal driving force for actuation. The identical configuration is formed at the opposite side of the main stroke transmitting lever to build an antagonistic SMA link. Both sides of the SMA links are mechanically connected and electrically isolated with the main stroke transmitting lever. The actuator device will attend the stroke length by passing a controlled electrical current in both sides of the SMA links. The actuation force can be increased by adding/arranging more segments of the SMA elements in parallel with the existing segments of the SMA elements in the part-modules. The stroke length of the actuator device is increased by adding/arranging more part-modules in series cascading with the previously attached part-modules.
In another aspect of the invention, the present invention relates to the actuation and can be used and explored for other applications wherein displacement with high actuation force is the critical requirement. The present embodiment finds extensive applications in industrial, domestic, and commercial sectors like automobile, aerospace, common appliances, energy, chemical processing, 3D printer filament extruder head motion, prosthetics, orthotics, robotics, and electronics (MEMS devices) industries for automation & control, heating & ventilation, safety & security, and bidirectional positioning such as linear, angular positioning and control, micro-displacement, etc. Some of these applications apply similar methods, concepts, or techniques, which are also applicable to other areas. The binary ‘ON/OFF’ positional applications of the actuator are widely ranging from electric door lock-unlock, home door latch-unlatch, vehicle door latch system, vehicle trunk/boot door, fuel tank lid, car central security latch system, and bidirectional motion for windshield wipers motion, directional airflow of wind blower motions, rear view mirror adjustment in automobiles, pin pullers and shutter controllers of space mechanical design actuation or other similar kinds of applications.
To further clarify the advantages and features of the methods, systems, and apparatuses, a more particular description of the methods, systems, and apparatuses will be rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the disclosure and are therefore not to be considered limiting of its scope. The disclosure will be described and explained with additional specificity and detail with the accompanying drawings.
These and other features, aspects, and advantages of the disclosure will become better understood when the following drawing description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Labels of figures: 1. Printer head base plate, 2. Circular guideway with bush assembly, 3. Extruder Throat, 4. Heater Block, 5. Nozzle, 6. Guide Shaft, 7. Stroke transfer connecting link, 8. Mounting base, 9. Mounting plate, 10. S-type rigid strip(s) (10A-10D), 11. S-type long tail stroke transmitting lever(s) (11A, 11B), 12. Segment(s) of the SMA element (12A-12F), 13. Fastening pin(s), 14. Crimp by metallic ferrule(s) (14A-14B), 15. Part-module(s) (15A, 15B), 16. Flipped S-type rigid strips, 17. Insulating strip, 18. ‘Flipped F-type long tail’ main stroke transmitting lever, 19. Mounting and guiding slit.
Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the disclosure. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the disclosure so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
To promote an understanding of the principles of the disclosure, reference will now be made to the various embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as illustrated therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates. It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the disclosure and are not intended to be restrictive thereof.
Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, appearances of the phrase “in an embodiment”, “in another embodiment”, “some embodiments”, “one or more embodiments” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.
Embodiments of the disclosure will be described below in detail with reference to the accompanying drawings.
The present invention provides a bidirectional, linear and binary segmented antagonistic servomechanism-based shape memory alloy (SMA) actuator, wherein the straight configuration comprising: a main stroke transmitting lever (11) and a plurality of part-modules (15A) disposed in a closely spaced arrangement and adapted to undergo a reciprocal translation in a first direction; wherein, the part-modules (15A) comprising a plurality of segments of the SMA elements (12), further, the segments of the SMA elements (12) are connected between the adjacent part-modules (15A) and main stroke transmitting lever (11), and each segment of the SMA element (11) extending longitudinally in the first direction; wherein the main stroke transmitting lever (11) undergoes reciprocal translation in the returned direction from the first direction by closely spaced arrangement in opposite/antagonistic configuration by the plurality of part-modules (15A); wherein, the antagonistic configuration of part-modules (15A) comprises the plurality of segments of the SMA elements (12), each segment extending longitudinally generally in the returned direction and segment of the SMA elements (12) connected between two adjacent part-modules and main stroke transmitting lever (11);
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In another embodiment, the operation of the invented linear actuator is controlled by pulses of electrical energy or train of Pulse Width Modulation (PWM) control signal with a suitable electrical power source. The magnitude of applied electrical power regulates different parameters such as total stroke length displacement, net actuation force generation, response time, operating speed, and working bandwidth of the embodiment. These parameters are also directly related to the dimensions (length and diameter) of employed SMA wire. The overall volumetric dimensions of the assembly depend on the number of part-modules used, and each part-module stroke length contributes to yielding total stroke length in an additive manner and net actuation force by the invention. Therefore, the number of part-modules develop by segmenting the whole length designed SMA wire. The total resultant stroke length represents by ‘SL’ defined by
SL
f=Σi=1nΔli (1)
SL
b=Σi=1nΔli (2)
SL
f
=−SL
b (3)
While specific language has been used to describe the subject matter, any limitations arising on account thereto, are not intended. As would be apparent to a person in the art, various working modifications may be made to the method to implement the inventive concept as taught herein. The drawings and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment.
The experiments were performed to measure the performance of the invented SMA actuator quantitatively. The experimental setup consists of an invented SMA actuator, PC-based controller and data acquisition system, measurement sensors for stroke length (displacement) and net load for external work done, and a regulated power supply with the connected heating module. The joule heating technique is employed for regulating the heating current by the pair of PWM signals generated from a PC-based NI DAQ (National Instrument Data acquisition) system. Generated load was measured by a pair of load cells (LC) of measuring capacity 10 lb from Honeywell Inc., USA. The first end of LC is rigidly mounted at the mounting base 8 and another end is firmly connected to the loose end of the segments of the SMA elements 12. A laser displacement sensor (IL-30 along with IL-100 amplifier from Keyence, Japan) was employed for stroke length (displacement) measurement. The multifunction NI-DAQ card PXIe-6341 was used for data acquisitions.
The first example demonstrates the stroke length (displacement) measurement of the invented bidirectional linear SMA actuator. The PWM controlled heating pulses are applied to both sides of the main stroke transmitting lever part-modules (PM1 & PM2) simultaneously in 37% and 1% of the PWM duty ratio. The conditions of duty ratio are flipped in the next interval to complete one cycle of the forward and backward motion. The total stroke length in the forward and backward direction is measured of 4.8 mm. The measured stroke length and applied control heating pulses for one complete cycle are shown in
The second example demonstrates the repeatability of 4.8 mm stroke length in forward and backward direction motion of both part-modules (PM1 & PM2) with respect to simultaneously applied heating current pulses as shown in
The third example demonstrates the net load measurement from the invented SMA actuator for the external work done. The PWM controlled heating pulses are applied to both the part-modules (PM1 & PM2) simultaneously in 37% and 1% of the PWM duty ratio and the conditions of duty ratio are flipped in the next interval to complete one cycle of forward and backward motion. The total net load in the forward and backward directions is measured of 2.6 kg. The observations of the net load and applied control heating pulses for one complete cycle are shown in
The fourth example demonstrated the repeatability of measured 2.6 kg net load for external work done in forward and backward motion of both part-modules (PM1 & PM2) with respect to simultaneously applied heating current pulses as shown in
In example 5, the combined output measurements of the forward and backward strokes of the developed device are shown. The device can produce 4.75-4.85 mm of total forward and backward stroke length (displacement) with 2.5-2.8 kg net load generated for external pulling and pushing of work done in each cycle of the operation. The results are plotted in
| Number | Date | Country | Kind |
|---|---|---|---|
| 202211060660 | Oct 2022 | IN | national |
| Number | Date | Country | |
|---|---|---|---|
| 20240133367 A1 | Apr 2024 | US |
