Shape memory alloy-based actuator
The SMA actuator design with two cylinders, multipliers, and recovery elements addresses energy and assembly issues, enabling heavy load lifting and adjustable force/displacement, enhancing SMA actuator performance.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- UNIVERSIDAD CARLOS III DE MADRID
- Filing Date
- 2026-01-08
- Publication Date
- 2026-07-16
AI Technical Summary
Existing shape memory alloy (SMA) actuators face limitations such as high energy consumption, difficulty in maintaining fiber tension, friction, assembly complexity, and limited load-lifting capabilities, particularly with diameters greater than 1 mm, which restrict their application in heavy-duty scenarios.
A SMA-based actuator design comprising two cylinders with SMA fibers, a displacement and/or variable force multiplier, and a recovery element, allowing adjustable force and displacement through a pivot point, with heating mechanisms like Joule effect or electrical resistance, and optional heat dissipation, enabling lifting of up to 4500 N loads with diameters of 1 to 3 mm.
The actuator achieves high load capacity and adjustable force/displacement, overcoming energy inefficiencies and assembly challenges, providing cyclical operation and control over position and force.
Smart Images
Figure ES2026070005_16072026_PF_FP_ABST
Abstract
Description
[0001] DESCRIPTION
[0002] Qualification
[0003] Shape memory alloy-based actuator
[0004] Field of invention
[0005] The present invention pertains to the technical field of actuators and mechanical drives, specifically to actuators made of shape-memory alloy materials, which change their dimensions when subjected to changes and return to their original shape when those conditions return to normal. More specifically, it relates to actuators made using shape-memory alloy fibers that change their dimensions when the temperature changes and return to their original state when the temperature returns to its original value.
[0006] Background of the invention
[0007] Shape memory alloys (SMAs) change their dimensions when subjected to changes and return to their original shape when those conditions return. Specifically, their dimensions change with temperature and they return to their original dimensions when the temperature returns to its original value.
[0008] Currently, there are various actuators based on shape memory alloys, such as nickel-titanium (Ni-Ti) fibers, and others like gold-cadmium (Au-Cd) and copper-zinc (Cu-Zn). Components made with these alloys contract when the temperature rises to a certain value and return to their original shape when the temperature drops. This property is primarily used for lifting loads and operating levers, actuators, and other mechanisms, with a wide range of applications in levers, latches, simple drives, and components used in robotics, aerospace, automotive, automation, and medicine.
[0009] Actuators made from these shape-memory alloys, based on the aforementioned materials, are one of the unconventional actuation solutions that offer the possibility of overcoming the current limitations of classic actuation systems. This is due to their favorable weight-to-size-to-actuation-force ratio, their simple structure, and their quiet operation. Because of their promising properties, these types of actuators have been successfully integrated into various applications in the fields mentioned above.
[0010] To date, most actuators use NiTi fibers with diameters less than 1 mm, resulting in very limited displacements and forces up to 500 N. To achieve these force values, several fibers are used in parallel, which is known as "Bundled Wires" configurations.
[0011] In one actuator model, up to 104 shape-memory alloy fibers were used in parallel, aligned between two through-hole pieces. This actuator also included pulleys to double the displacement and gas springs to aid in the actuator's recovery during the cooling stage. The proposed actuator can move a load of approximately 327 N, providing a displacement of 8% of its length. Limitations of this type of actuator include high energy consumption, the difficulty of maintaining consistent fiber tension, which can lead to breakage and subsequent actuator failure, friction between the fibers and other actuator components such as the pulleys, and the difficulty of assembly due to the large number of fibers.
[0012] Currently, other linear actuators based on shape-memory alloys exist that can lift weights up to 800 N, with a unidirectional displacement of up to 7 mm. The actuator design is based on several parallel SMA fibers (Bundled Wires), which provide a compact, lightweight, quiet design with a good strength-to-size ratio.
[0013] Other manufacturers sell SMA fibers with diameters of 2 mm that can lift heavy loads, but they only offer actuator solutions with forces up to 800 N or up to 1500 N, offering displacements of 2 mm.
[0014] However, the applicant is unaware of the existence of actuators made of shape memory fibers capable of providing forces greater than 1500 N.
[0015] Therefore, a fiber-based actuator with memory is desirable so that it is capable of moving high loads while avoiding the drawbacks of existing systems in the prior art. Description of the invention
[0016] The present invention solves existing problems in the prior art by means of a shape memory alloy-based actuator for lifting loads, comprising a first cylinder and a second cylinder connected to each other. Each of these two cylinders has, in turn, a plurality of shape memory alloy fibers (or SMA fibers) and means for heating these fibers to activate them, causing them to shorten and lift the load. The first cylinder has a base end for attachment to a fixed surface and a connecting end, while the second cylinder has a gripping end for attaching the load to be lifted and a connecting end.The actuator also features a displacement and / or variable force multiplier, which connects both cylinders at their connecting ends. This multiplier modifies and adjusts the actuator's final displacement or the force it exerts, depending on the pivot point. Increasing the actuator's displacement decreases the force it exerts, and vice versa. For example, moving one of the cylinders closer to the multiplier's pivot point will result in less displacement but increase the force it exerts. This allows the actuator's force or displacement to be adjusted according to the specific application or needs, although both parameters change simultaneously. This displacement and / or variable force multiplier can be a pulley or a lever.For example, if the multiplication ratio is 1:1, the actuator's output, in position, will be the displacement of one duplicate fiber multiplied by two, and the approximate force of a fiber assembly. For example, if the characterized fibers have a maximum displacement of 4% of their length, the actuator will exhibit a maximum displacement of 8% of the fiber length.
[0017] In particular, the heating means of shape memory alloy fibers have an electrical connection to said fibers for heating by Joule effect.
[0018] Alternatively, or as a supplementary measure if the necessary heating is not achieved by the Joule effect, the heating means may include an electrical resistance element encasing each fiber and a sheath encasing each fiber and resistance assembly. The fibers are activated by the electrical resistance, which heats up via the Joule effect. Alternatively, other heating means for activation may be used, provided they are compatible with the actuator, to avoid the high energy consumption of the Joule effect.
[0019] According to preferred embodiments of the invention, the shape-memory alloy fibers have a diameter of at least 1 mm and up to 3 mm, enabling them to lift heavy loads of up to 4500 N in a compact and lightweight format. The actuator allows for adjusting the force and displacement according to the specific application, taking into account energy consumption and fiber recovery after activation. The actuator allows for cyclical displacement.
[0020] This load capacity far exceeds that of actuators based on shape memory alloys, which in the prior art can handle loads of up to 800 N with 1 mm fibers, or 1500 N with 2 mm fibers for single-cycle activation at room temperature. Furthermore, in the prior art, if the fiber were high-temperature, its activation would result in high energy consumption, preventing Joule heating.
[0021] Preferably, the actuator of the invention has a recovery element connected to the engagement end of the second cylinder and to a fixed surface, which exerts force in the direction of recovery of the initial position of the shape memory alloy fibers, thereby helping in their recovery when the temperature returns to its initial values.
[0022] Specifically, this recovery element may consist of at least one shape-memory alloy fiber and means for heating it. Preferably, according to this embodiment, the recovery element may have a displacement and / or variable force multiplier connecting the shape-memory alloy fiber to the engagement end of the second cylinder, to modify and adjust the final displacement of the recovery element or the force it exerts. Thus, this recovery element will act in opposition, contributing to the recovery of the actuator to its zero or initial position, i.e., the actuator's reset. This will be particularly useful in cases where, after activation, there is no recovery force because the load lifted by the actuator has been removed.Alternatively, the recovery element could be made using other conventional elements, such as an elastic spring, or a gas piston.
[0023] According to a preferred embodiment, the actuator may incorporate a fan to dissipate heat for the recovery of the initial position of the shape memory alloy fibers.
[0024] According to different specific embodiments of the invention, the actuator may have different sensors for its control. These sensors may be arranged on the displacement and / or variable force multiplier to measure the displacement of said displacement and / or variable force multiplier, specifically its angular displacement, and from this, the actuator's displacement can be calculated.
[0025] Most existing actuators in the prior art are unidirectional, and those using large diameter SMA wires are not controlled, but only switched on and off (on / off function only). In contrast, the actuator of the present invention can control both position and force, and can also recover its position.
[0026] Brief description of the drawings
[0027] Next, to facilitate understanding of the invention, an embodiment of the invention will be described by way of illustration but not limitation, which refers to a series of figures.
[0028] Figure 1 shows a schematic embodiment of an external configuration of an actuator of the present invention attached to the load to be lifted.
[0029] Figure 2 shows an embodiment of an internal configuration of the actuator embodiment of Figure 1 attached to the load to be lifted.
[0030] Figure 3 is a cross-section view of a section of one of the actuator cylinders in Figure 2, showing in detail the shape memory alloy fibers.
[0031] Figure 4 schematically shows an embodiment of the fiber heating means of the actuator shown in the previous figures. These figures refer to a set of elements which are:
[0032] 1. actuator
[0033] 2. load
[0034] 3. First cylinder of the actuator
[0035] 4. second actuator cylinder
[0036] 5. actuator base end
[0037] 6. connection end between cylinders
[0038] 7. actuator engagement end
[0039] 8. variable displacement and / or force multiplier
[0040] 9. Shape memory alloy fibers
[0041] 10. electrical resistance
[0042] 11. case
[0043] 12. recovery element
[0044] 13. fan
[0045] 14. fixed surface
[0046] 15.- sensor
[0047] Detailed description of the invention
[0048] The object of the present invention is an actuator based on a shape memory alloy.
[0049] As can be seen in the figures, the actuator is configured to lift loads and consists primarily of a first cylinder 3 and a second cylinder 4 connected to each other. Each of these two cylinders 3, 4 contains a plurality of shape-memory alloy fibers 9 and means for heating these shape-memory alloy fibers 9. Preferably, up to twelve shape-memory alloy fibers 9 can be accommodated, although other quantities are possible depending on the application. The first cylinder 3 has a base end 5 for attachment to a fixed surface 14 and a connection end 6 for connection to the second cylinder 4, while the second cylinder 4 has a hook end 7 for engaging the load 2 to be lifted and a connection end 6 for connection to the first cylinder 3.Actuator 1 also features a displacement and / or variable force multiplier 8, which connects both cylinders 3 and 4 via their connecting ends 6. This multiplier modifies and adjusts the final displacement of actuator 1 or the force exerted by it, depending on the pivot point. Increasing the displacement of actuator 1 decreases the force it exerts, and vice versa. For example, in the embodiment shown in Figure 2, moving the second cylinder 4 (located on the left in Figure 2) closer to the pivot point of the displacement and / or variable force multiplier 8 results in less displacement generated by actuator 1, but increases the force it exerts. Regarding the first cylinder 3 (located on the right in Figure 2), the closer it is to the pivot point, the greater the final displacement generated, but the lower the force.In this way, the force exerted or displacement of actuator 1 can be adjusted depending on the specific needs, although both parameters vary simultaneously. This displacement and / or variable force multiplier 8 can be a pulley or a lever, as shown in Figure 2.
[0050] According to a particular embodiment, the heating means of the shape memory alloy fibers 9 have an electrical connection (not shown in the figures) to said fibers 9 for heating by Joule effect.
[0051] Alternatively, or complementarily, for cases where the necessary heating is not achieved by the Joule effect of the electrical connection, the heating means may have an electrical resistance 10 that envelops each of the fibers 9, and a sheath 11 that in turn envelops each of the fiber 9 and electrical resistance 10 assemblies for the activation of the fibers 9 by means of the electrical resistance 10. The sheath 11 will preferably be made of Teflon, although other similar materials could be used, and is used to insulate the fibers 9 from each other and at the same time retain the heat in them.
[0052] Other means of heating the fibers 9 may be valid to avoid the high energy consumption of the Joule effect, provided they are compatible with the operation of the actuator 1.
[0053] According to preferred embodiments of the invention, the shape memory alloy fibers 9 have a diameter of at least 1 mm, and up to 3 mm, so that they can lift heavy loads of up to 4500 N in a compact and lightweight format.
[0054] Preferably, the actuator 1 may have a recovery element 12 connected to the engagement end 7 of the second cylinder 4 and to a fixed surface 14, such that said recovery element 12 exerts force in the direction of recovery of the initial position of the shape memory alloy fibers 9, assisting in their recovery when the temperature returns to its initial values.
[0055] Specifically, as shown in Figure 2, this recovery element 12 may consist of at least one shape-memory alloy fiber 9 and means for heating it. Preferably, according to this embodiment, the recovery element 12 may have a displacement and / or variable force multiplier 8 that connects the shape-memory alloy fiber 9 and the engagement end 7 of the second cylinder 4, to modify and adjust the final displacement of the recovery element 12 or the force exerted by it. As shown in Figure 2, this displacement and / or variable force multiplier 8 of the recovery element 12 is a lever, although it could also be another type of multiplying element, such as a pulley.
[0056] Alternatively, the recovery element 12 could be made using other conventional elements, such as an elastic spring, or a gas piston, not shown in the figures.
[0057] According to a preferred embodiment, and as shown schematically in Figure 1, the actuator 1 may incorporate a fan 13 to dissipate heat for the recovery of the initial position of the shape memory alloy fibers 9.
[0058] According to different particular embodiments of the invention, the actuator 1 may have at least one, or several, sensors 15 for its control. These sensors 15 may be arranged in the displacement and / or variable force multiplier 8 for measuring the angular displacement of said displacement and / or variable force multiplier 8, and from this, calculate the displacement of the actuator 1.
Claims
CLAIMS 1. Shape memory alloy-based actuator configured to lift a load (2), comprising a first cylinder (3) and a second cylinder (4) connected to each other, each of the cylinders (3,4) in turn comprising a plurality of shape memory alloy fibers (9), and heating means for shape memory alloy fibers (9), characterized in that the first cylinder (3) comprises a base end (5), configured to be attached to a fixed surface 14, and a connection end (6), the second cylinder (4) comprises a latching end (7), configured to latch the load (2), and a connecting end (6), and The actuator (1) comprises a variable displacement and / or force multiplier (8) that connects both cylinders (3,4) through their connection ends (6), configured to adjust the final displacement of the actuator (1) or the force exerted by said actuator (1).
2. Shape memory alloy-based actuator according to claim 1, wherein the heating means for the shape memory alloy fibers (9) comprise an electrical connection to said fibers (9) for heating by Joule effect.
3. Actuator based on a shape memory alloy, according to any of the preceding claims, wherein the heating means for the shape memory alloy fibers (9) comprise an electrical resistance (10) that envelops each of the fibers (9), and a sheath (11) that in turn encloses each of the fiber (9) and electrical resistance (10) assemblies.
4. Shape memory alloy-based actuator, according to any of the preceding claims, wherein the variable displacement and / or force multiplier (8) is selected from a pulley and a lever.
5. Shape memory alloy-based actuator, according to any of the preceding claims, comprising a recovery element (12) connected to the engagement end (7) of the second cylinder (4) and to a fixed surface (14), configured to exert force in the direction of recovery of the initial position of the shape memory alloy fibers (9).
6. Shape memory alloy-based actuator according to claim 5, wherein the recovery element (12) comprises at least one shape memory alloy fiber (9) and means for heating it.
7. Shape memory alloy-based actuator according to claim 6, wherein the recovery element (12) comprises a variable displacement and / or force multiplier (8) connecting the shape memory alloy fiber (9) and the engagement end (7) of the second cylinder (4), configured to adjust the final displacement of the recovery element (12) or the force exerted by said recovery element (12).
8. Shape memory alloy-based actuator according to claim 5, wherein the return element (12) comprises at least one elastic spring.
9. Shape memory alloy-based actuator according to claim 5, wherein the recovery element (12) comprises at least one gas piston.
10. Shape memory alloy-based actuator, according to any of the preceding claims, comprising a fan (13) configured for heat dissipation for recovery of the initial position of the shape memory alloy fibers (9).
11. Shape memory alloy-based actuator, according to any of the preceding claims, comprising at least one sensor (15) disposed in the displacement and / or variable force multiplier (8) configured for measuring the displacement of said displacement and / or variable force multiplier (8) and the displacement of the actuator (1).
12. Shape memory alloy-based actuator, according to any of the preceding claims, wherein the shape memory alloy fibers (9) have a diameter arranged in the range of 1-3 mm.