Shape memory spring bidirectional control planetary differential elastic drive

Abstract

This invention provides a shape memory spring-controlled bidirectional planetary differential actuator, comprising a housing, an input shaft, an output shaft, an actuator, a shape memory bidirectional controllable planetary differential mechanism, and an elastic energy storage element. The housing, used to fix the actuator and the elastic energy storage element, is composed of a main body, a rear end cover, and a front end cover. The shape memory bidirectional controllable planetary differential mechanism consists of a planetary carrier, a planetary gear set, a bidirectional controllable gear ring ratchet, two pawls, a cam lever, and a shape memory spring. One end of the elastic energy storage element is connected to the bidirectional controllable gear ring ratchet, and the other end is fixed through the main body of the housing. The oscillation direction of the cam lever is controlled by the thermal contraction of the shape memory spring, and the rotation direction of the bidirectional controllable gear ring ratchet is controlled by the meshing state of the bidirectional controllable gear ring ratchet and the pawls. This invention utilizes the thermal effect of the shape memory spring as the driving method to control the bidirectional controllable gear ring ratchet, improving the instantaneous driving force of the actuator and reducing power consumption.

Description

Technical Field

[0001] This invention relates to the field of robotics, specifically to a planetary differential elastic actuator with bidirectional control of shape memory springs. Background Technology

[0002] As organisms have evolved, legged creatures have become increasingly agile during movement, and their entire propulsion system has reached new heights, exhibiting complex motion characteristics. Consequently, legged bionic robots have also seen some development, with primary gaits including running, jumping, and crawling, all of which possess discrete gait characteristics. To improve the dexterity and maneuverability of legged robots, the drive joints need to have extremely high instantaneous output power, i.e., explosive force. This is also the primary motion state commonly used in the biological world for obstacle avoidance and predator evasion.

[0003] The most crucial component of a robot's joints is the actuator, which determines the robot's motion performance and energy efficiency. Many current articulated robots possess significant advantages in movements such as running and jumping, achieving instantaneous energy bursts while maintaining overall system stability and safety. Joint actuators are the core components, playing a vital role in improving the robot's motion performance and control. Various types of actuators exist today, each with its own advantages and disadvantages in different fields. However, their large size and high energy consumption are challenging issues, making robots somewhat cumbersome. Purely motor-driven robots have poor energy efficiency and stability, making it difficult to achieve optimal robot performance. For example, fields such as exoskeletons or prosthetics require more flexible features that conform to human needs.

[0004] Traditional motor actuators cannot meet the requirements of biomimetic joints for high power, low energy consumption, and collision safety, making it difficult for biomimetic drive systems to surpass biological drive systems. Elastic actuators, which integrate elastic elements with traditional actuators, act as energy buffers. They not only exhibit the buffering effect of actuators but also store and release energy, significantly improving the impact resistance and safety of the drive system. This is the main reason why elastic actuators have attracted so much attention and are widely used in robot joints for gait movements such as running and jumping. Biomimetic elastic actuators enable energy exchange between the actuator and the load, reducing power loss and making the actuator more energy-efficient.

[0005] Patent CN110315520B discloses an energy-controllable redundant elastic actuator based on a variable-cell mechanism, comprising an output shaft, a drive motor, a planetary differential, and a housing. The housing is constructed by sequentially connecting and fixing a front cover for supporting the output shaft, a housing body, and a rear cover for fixing the drive motor. The planetary differential consists of a planetary gear set and a rotatable gear ring, with a ratchet engaged with a pawl hinged to the housing body. This mechanism solves the problems of existing joint actuators, such as lack of buffering capacity, poor shock resistance, and high power consumption under the requirements of high-load cyclic motion.

[0006] Patent CN113334356B discloses a passive variable stiffness series elastic actuator. A motor assembly generates torque, which is then used by a transmission assembly to rotate a lead screw nut fixed circumferentially to the output component. During operation, the rotation of the lead screw is constrained by a lower leg, thus the rotation of the nut causes the output component to move. The stiffness of this actuator can change with the external load, and compared to a constant stiffness series elastic actuator, it can guarantee force measurement resolution at low stiffness and control bandwidth at high stiffness.

[0007] Patent CN113211428B discloses a variable stiffness series elastic drive device and its control method, including: a drive mechanism, a reciprocating mechanism, an elastic output mechanism, a power supply, and a controller. This drive device features a compact and reliable structure, improved system safety, variable stiffness control and joint buffering capability, flexible adjustment methods, and a wide range of applications.

[0008] As can be seen from the above elastic actuators, biomimetic elastic actuators are widely used in the field of robotics. Compared with traditional actuators, the elastic elements inside the elastic actuators have the characteristics of small size, impact resistance, and low output impedance. Therefore, how to develop biomimetic elastic actuators towards low energy consumption, high burst power, lightweight, and miniaturization is one of the urgent problems to be solved. Currently, biomimetic elastic actuators are widely used in rehabilitation robots, jumping robots, and human prostheses. Biomimetic elastic drive joints for robots with military applications are also a direction that researchers are constantly striving for, showing strong foresight. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing actuator technology and provide a planetary differential elastic actuator with bidirectional control of shape memory spring. This invention integrates the shape memory bidirectional controllable planetary differential mechanism with the elastic energy storage element, thereby improving the energy efficiency of the elastic actuator. It features small size, simple structure, low cost, wide application, low power consumption, small weight, and impact resistance. At the same time, it enables articulated robots to generate instantaneous burst energy under high loads and also has a ground-contact buffering effect.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A shape memory spring-controlled bidirectional planetary differential actuator includes a housing, an input shaft, an output shaft, an actuator, a shape memory bidirectional controllable planetary differential mechanism, and an elastic energy storage element. The housing is used to fix the stator and rotor of the actuator and the elastic energy storage element, and is composed of a housing body, a rear end cover supporting the input shaft, and a front end cover fixing the entire actuator, which are interconnected. The input shaft is connected to a flange, and a bearing is provided between the flange and the rear end cover. The shape memory bidirectional controllable planetary differential mechanism is provided in the inner cavity of the housing body. The input shaft is connected to the sun gear of the planetary gear set, which transmits the torque of the actuator from the sun gear to the planet gears and the bidirectional controllable gear ratchet. The output shaft is connected to the planet gear shaft, and the torque is transmitted from the planet gear shaft to the output shaft.

[0012] The shape memory bidirectional controllable planetary differential mechanism includes a planet carrier (12), a planetary gear set (13), a bidirectional controllable gear ring ratchet (16), a variable diameter spring (19), two pawls (20), a cam lever (21), a shape memory spring (22), and four tension springs (25). The bidirectional controllable gear ring ratchet has ratchet teeth on its outside. The two pawls are fixed by circular grooves on the housing and mesh with the ratchet teeth to realize the locking and unlocking states of the bidirectional controllable gear ring ratchet. At the same time, the outer end face of the bidirectional controllable gear ring ratchet is connected to the four tension springs by wire winding through holes. The other end of the four tension springs is fixed to the main body of the housing. The rotation of the bidirectional controllable gear ring ratchet can cause the four tension springs to deform, thereby generating elastic potential energy. Due to the symmetrical installation of the shape memory bidirectional controllable planetary differential mechanism and the four tension springs, the bidirectional controllable gear ring ratchet can be rotated in both directions to store energy.

[0013] In this invention, when the driver input shaft rotates counterclockwise (viewed from the front end), and one end of the external relay receives a high level (assuming the right side is high at this time) while the other end receives a low level, the shape memory spring at the high-level end is energized and undergoes thermal contraction. At this time, the energized shape memory spring at the high-level end causes the cam lever to move towards the high-level end, and the pawl at the low-level end engages with the bidirectional controllable gear ratchet. When encountering a low load, the output shaft also rotates counterclockwise. In this case, the bidirectional controllable gear ratchet will not undergo a large-angle rotational change, ensuring the shape memory... The bidirectional controllable planetary differential mechanism operates normally. When the drive encounters a high load, the input shaft continues to rotate counterclockwise. At this point, the output shaft stops rotating due to the excessive load, and the resulting impact is absorbed by the four tension springs. The bidirectional controllable gear ring ratchet rotates clockwise according to the principle of a planetary differential, causing the four tension springs connected to the end face of the bidirectional controllable gear ring ratchet to be stretched clockwise, resulting in elastic deformation. The resulting elastic potential energy is locked by the two pawls. Therefore, when the drive system encounters a high load, this invention can absorb the impact, improving the stability and vibration damping of the drive. Under high load, the elastic potential energy is locked until the four tension springs reach their maximum deformation. When the driver rotates counterclockwise again, a high-level signal is applied to the relay connected to the left shape memory spring, and a low-level signal is applied to the relay connected to the right shape memory spring. This causes the cam lever to move to the left, opening the left pawl and releasing the stored elastic potential energy. The combined torque of the motor drive torque and the torque on the bidirectional controllable geared ratchet results in a sudden increase in output power, increasing the motor's maximum instantaneous power, improving energy utilization, and reducing the driver's energy consumption. When the driver input shaft rotates clockwise (viewed from the front end), a high-level signal is applied to the relay connected to the right shape memory spring. Since the bidirectional controllable geared ratchet is locked counterclockwise, the bidirectional controllable planetary differential mechanism can be considered a regular reducer, and the entire elastic driver can be considered a geared motor where the driver and reducer are integrated.

[0014] When the driver input shaft rotates clockwise (viewed from the front end), a high-level signal is applied to the relay connected to the shape memory spring on the left, causing the cam lever to move to the left. The pawl on the right then engages with the bidirectional controllable gear ratchet. Under low load, the output shaft also rotates clockwise. At this time, the bidirectional controllable gear ratchet does not undergo large-angle rotational changes, ensuring the normal operation of the shape memory bidirectional controllable planetary differential mechanism. When the driver encounters high load, the input shaft still rotates clockwise. At this time, the output shaft stops rotating due to excessive load. The resulting impact is absorbed by the four tension springs. The bidirectional controllable gear ratchet rotates counterclockwise according to the principle of planetary differentials. This causes the four tension springs connected to the end face of the bidirectional controllable gear ratchet to be stretched counterclockwise, generating elastic deformation. The resulting elastic potential energy is locked by the pawl. When the driver rotates counterclockwise again, a high-level signal is applied to the relay connected to the shape memory spring on the right, and a low-level signal is applied to the other end, causing the cam lever to move to the right. The pawl on the right then opens, releasing the stored elastic potential energy. When the input shaft of the driver rotates counterclockwise (viewed from the front end), a high level is applied to the relay connected to the shape memory spring on the left, and a low level is applied to the other end. Since the bidirectional controllable gear ratchet is locked in the clockwise direction, the bidirectional controllable planetary differential mechanism can be regarded as an ordinary reducer, and the entire elastic driver can be regarded as a geared motor in which the driver and reducer are integrated.

[0015] Preferably, the elastic energy storage element is embedded inside the elastic actuator, integrated with the actuator, and the tension spring can be replaced at any time to change the spring stiffness. The spring is easy to install and remove.

[0016] Preferably, the cam structure on the cam lever allows the two pawls to cleverly control the rotation direction of the bidirectional controllable gear ratchet, thereby controlling the direction of energy storage and release, realizing a bidirectional controllable planetary differential mechanism, and using the material properties of shape memory springs to control the swing motion of the cam lever, and controlling the on / off state of the shape memory springs through the high and low levels of multi-channel relays.

[0017] Preferably, the bidirectional controllable planetary differential mechanism adopts a single-stage reduction, including a sun gear, planet gears, planet gear shafts, a planet carrier, and a bidirectional controllable gear ring ratchet; the driver input shaft is connected to the sun gear, the sun gear meshes with the three planet gears for transmission, and the planet gear shaft is connected to the output shaft; the driver torque is transmitted from the sun gear to the planet gears, and then from the planet gears to the output shaft and the bidirectional controllable gear ring ratchet, and finally to the load end.

[0018] Preferably, the bidirectional controllable gear ratchet has bearings embedded inside, the front and rear covers are also embedded with bearings, the planetary carrier has thin-walled bearings embedded inside and outside, and the input shaft end has a small bearing embedded to ensure smooth transmission.

[0019] Preferably, the stator of the driver is fixed to the main body of the housing by cylindrical retaining adhesive, and the rotor of the driver is connected to the sun gear of the planetary gear set through a flange cover. The inner cavity of the main body of the housing supporting the stator is provided with a shape memory bidirectional controllable planetary differential mechanism, thus realizing the integration of the driver and the shape memory bidirectional controllable planetary differential mechanism.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) In the field of articulated robots, this invention can effectively absorb impact energy, ensure the stability of the system, and store energy. When needed, the stored energy can be provided again to improve the maximum instantaneous power of the drive system. During the robot's movement, it not only has a certain buffering effect, but also has the characteristics of high energy efficiency, low power consumption, low cost, miniaturization, and lightweight.

[0022] (2) The spring installation and disassembly method mentioned in this invention is convenient, and springs with appropriate stiffness can be replaced according to different environments.

[0023] (3) This invention integrates the bidirectional controllable planetary differential mechanism with the shape memory spring, and uses a first-stage planetary gear to reduce the axial dimension. It also utilizes the thermal shrinkage of the shape memory alloy material to achieve bidirectional meshing alternating control of the bidirectional controllable planetary differential mechanism.

[0024] (4) The present invention connects the stator and rotor of the driver to the main body of the housing. The housing is made of aluminum alloy and uses four small tension springs and a bidirectional controllable planetary differential mechanism, which can effectively reduce the weight of the entire driver.

[0025] (5) The present invention has a bearing inside the bidirectional controllable gear ratchet, a bearing between the rear end cover and the flange cover, a bearing between the front end cover and the output shaft, a small bearing between the input shaft and the output shaft, and a thin-walled bearing between the planetary carrier, the motor rotor and the main body of the housing, which effectively reduces the friction inside the driver and minimizes the energy loss caused by friction. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the axial assembly of the present invention.

[0027] Figure 2 This is an isometric view of the present invention.

[0028] Figure 3 This is a schematic diagram of the planetary gear set mechanism of the present invention.

[0029] Figure 4 This is a schematic diagram of the ratchet and pawl mechanism of the present invention.

[0030] Figure 5 This is a schematic diagram of the frameless motor structure of the present invention.

[0031] Figure 6 This is a schematic diagram of the cam lever structure of the present invention.

[0032] Figure 7 This is a schematic diagram of the ratchet structure of the present invention.

[0033] The components include: 1. Encoder frame; 2. Rear end cover; 3. Bearing 1; 4. Magnet; 5. Flange cover; 6. Rotor end cover; 7. Motor rotor; 701. Rotor magnet; 702. Magnet; 8. Motor stator; 801. Stator winding; 802. Stator body; 9. Bearing 2; 10. Input shaft; 11. Bearing 3; 12. Planetary carrier; 1301. Planetary gear; 1302. Planetary gear shaft; 1303. Sun gear; 14. Housing body; 15. Bearing 4; 16. Bidirectional controllable gear ratchet; 17. Bearing 5; 18. Output shaft; 19. Variable diameter spring; 20. Pawl; 21. Cam lever; 22. Shape memory spring; 23. Bearing 6; 24. Front end cover; 25. Tension spring. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0035] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0036] Example 1:

[0037] refer to Figures 1-7A shape memory spring-controlled bidirectional planetary differential actuator includes an input shaft 10, a motor rotor 7, a motor stator 8, a shape memory bidirectional controllable planetary differential mechanism, an elastic energy storage element tension spring 25, and a housing. The housing consists of an encoder frame 1 for fixing the encoder, a rear end cover 2 supporting the output shaft 6 and the motor rotor 7, a housing body 14 supporting two pawls 20 and a variable diameter spring 19, and a front end cover 24 supporting the output shaft. A bearing 3 is provided between the rear end cover 2 and the flange cover 5 for fixing the input shaft 10. The inner cavity of the main body 14 is equipped with a shape memory bidirectional controllable planetary differential mechanism. The motor input shaft 10 transmits the input to the planetary gear set 13 through the connection with the sun gear 1303. The motor output shaft 18 is connected to the bidirectional controllable planetary differential mechanism through the planetary gear shaft 1302 to transmit the torque in the planetary gear set 13 to the load end. A small bearing 15 is provided between the motor input shaft 10 and the output shaft 18, a bearing 11 is provided between the planet carrier 12 and the motor rotor 7, and a bearing 23 is provided between the output shaft 18 and the front cover 24.

[0038] The bidirectional controllable planetary differential mechanism consists of a primary planetary gear set 13 and a bidirectional controllable ring gear ratchet 16. The primary planetary gear set 13 includes planetary gears 1301, a sun gear 1303, and a planetary gear shaft 1302. The bidirectional controllable ring gear ratchet 16 is provided with ratchet teeth, which mesh with pawls 20 fixed to the main body 14 of the housing. The cam lever 21 can control the opening and closing of the pawls 20 to achieve locking and contact locking of the rotational movement of the bidirectional controllable ring gear ratchet 16. There are four through holes near the right end face of the bidirectional controllable ring gear ratchet 16, which are connected to four tension springs 25. The other end of the four tension springs 25 is fixed to the main body of the housing. The rotation of the bidirectional controllable ring gear ratchet 16 realizes the extension and contraction deformation of the tension springs 25, thereby generating elastic potential energy.

[0039] In this embodiment, when the winding 801 of the stator 8 of the drive motor is energized, a magnetic force is generated to drive the rotation of the motor rotor 7, that is, the motor input shaft 10 starts to operate, and the torque of the input shaft 10 is transmitted to the bidirectional controllable planetary differential mechanism. When the relay connected to the right end of the shape memory spring 22 is at a high level and the other end is at a low level, under low load, if the motor input shaft 10 rotates counterclockwise (viewed from the front end 24), the driver output shaft 18 also rotates counterclockwise. At this time, the bidirectional controllable gear ring ratchet 16 and the pawl 20 mechanism remain stationary, ensuring that the planetary gear set 13 transmits torque normally. When the output shaft 18 encounters high load or impact, according to the principle of planetary differential, the bidirectional controllable gear ratchet 16 will rotate clockwise. At this time, the elastic energy storage element tension spring 25 also begins to extend clockwise, causing deformation and generating elastic force. During the extension of the four tension springs 25, the impact at the load end will be absorbed by the four tension springs 25. Therefore, the elastic energy storage element plays a role in shock resistance and buffering, which can effectively reduce the damage caused by ground impact during robot movement and improve the stability of the drive system. When the four tension springs 25 extend to a certain angle, the bidirectional controllable gear ratchet 16 stops moving, and the pawl 20 stores the elastic potential energy. When the motor input shaft 10 rotates counterclockwise again, the relay connected to the left shape memory spring is at a high level while the other end is at a low level, disengaging the left pawl 20 from the ratchet teeth of the bidirectional controllable gear ratchet 16. At this time, the elastic energy storage element tension spring 25 instantaneously releases its elastic potential energy, causing the bidirectional controllable gear ratchet 16 to rotate counterclockwise, providing driving torque together with the driver, increasing the driver's maximum instantaneous power, improving the driver's energy utilization rate, and reducing the driver's energy consumption. Similarly, when the relay connected to the left spring of the shape memory spring 22 is at a high level, under low load, if the motor input shaft 10 rotates clockwise (viewed from the front end face 24), the output shaft 18 also rotates clockwise. When the output shaft 18 encounters a high load or impact, according to the principle of the planetary differential, the bidirectional controllable gear ratchet 16 will rotate counterclockwise. At this time, the elastic energy storage element spring 25 also begins to extend in the counterclockwise direction, causing deformation and generating elastic force. When the input shaft 10 rotates clockwise normally again, the relay connected to the right shape memory spring is at a high level and the relay connected to the left shape memory spring is at a low level, releasing the engagement between the pawl 20 and the ratchet teeth on the bidirectional controllable gear ratchet 16. At this time, the elastic energy storage element spring 25 instantaneously releases elastic potential energy, causing the bidirectional controllable gear ratchet 16 to rotate clockwise, providing driving torque together with the driver.

[0040] This invention can change the direction of energy storage through a shape memory bidirectional controllable planetary differential mechanism, improving the flexibility of the actuator. It is widely used in legged joint robots and exoskeletons. During robot movement, it can absorb the impact of ground contact, playing a certain buffering role. At the same time, due to the presence of elastic energy storage elements, the actuator can store energy. When the actuator works again, it can be controlled to release energy at a specific time, working together with the actuator to provide torque and increase the maximum output power of the traditional actuator. It can not only be applied to legged robots to increase jumping height, but also to human exoskeletons to achieve assisted movements and improve energy utilization.

[0041] Example 2:

[0042] refer to Figures 1-7 A shape memory spring-controlled bidirectional planetary differential actuator includes an input shaft 10, a motor rotor 7, a motor stator 8, a shape memory bidirectional controllable planetary differential mechanism, an elastic energy storage element tension spring 25, and a housing. The housing consists of an encoder frame 1 for fixing the encoder, a rear end cover 2 supporting the output shaft 6 and the motor rotor 7, a housing body 14 supporting two pawls 20 and a variable diameter spring 19, and a front end cover 24 supporting the output shaft. A bearing 3 is provided between the rear end cover 2 and the flange cover 5 for fixing the input shaft 10. The inner cavity of the main body 14 is equipped with a shape memory bidirectional controllable planetary differential mechanism. The motor input shaft 10 transmits the input to the planetary gear set 13 through the connection with the sun gear 1303. The motor output shaft 18 is connected to the bidirectional controllable planetary differential mechanism through the planetary gear shaft 1302 to transmit the torque in the planetary gear set 13 to the load end. A small bearing 15 is provided between the motor input shaft 10 and the output shaft 18, a bearing 11 is provided between the planet carrier 12 and the motor rotor 7, and a bearing 23 is provided between the output shaft 18 and the front cover 24.

[0043] The bidirectional controllable planetary differential mechanism consists of a primary planetary gear set 13 and a bidirectional controllable ring gear ratchet 16. The primary planetary gear set 13 includes planetary gears 1301, a sun gear 1303, and a planetary gear shaft 1302. The bidirectional controllable ring gear ratchet 16 is provided with ratchet teeth, which mesh with pawls 20 fixed to the main body 14 of the housing. The cam lever 21 can control the opening and closing of the pawls 20 to achieve locking and contact locking of the rotational movement of the bidirectional controllable ring gear ratchet 16. There are four through holes near the right end face of the bidirectional controllable ring gear ratchet 16, which are connected to four tension springs 25. The other end of the four tension springs 25 is fixed to the main body of the housing. The rotation of the bidirectional controllable ring gear ratchet 16 realizes the extension and contraction deformation of the tension springs 25, thereby generating elastic potential energy.

[0044] In this embodiment, under low-load operation, when the two shape memory springs 22 are connected to different high and low levels in the multi-channel relays, the bidirectional controllable gear ratchet 16 and pawl 20 will not operate regardless of whether the driver rotates the input shaft 10 counterclockwise or clockwise. In this case, the invention can be used as a traditional planetary gear drive without affecting the normal function of the drive motor. Simultaneously, due to the presence of the bidirectional controllable planetary differential mechanism, a larger reduction ratio is achieved, increasing the output torque. That is, under specific conditions, the invention plays a specific role.

[0045] Example 3:

[0046] refer to Figures 1-7 A shape memory spring-controlled bidirectional planetary differential actuator includes an input shaft 10, a motor rotor 7, a motor stator 8, a shape memory bidirectional controllable planetary differential mechanism, an elastic energy storage element tension spring 25, and a housing. The housing consists of an encoder frame 1 for fixing the encoder, a rear end cover 2 supporting the output shaft 6 and the motor rotor 7, a housing body 14 supporting two pawls 20 and a variable diameter spring 19, and a front end cover 24 supporting the output shaft. A bearing 3 is provided between the rear end cover 2 and the flange cover 5 for fixing the input shaft 10. The inner cavity of the main body 14 is equipped with a shape memory bidirectional controllable planetary differential mechanism. The motor input shaft 10 transmits the input to the planetary gear set 13 through the connection with the sun gear 1303. The motor output shaft 18 is connected to the bidirectional controllable planetary differential mechanism through the planetary gear shaft 1302 to transmit the torque in the planetary gear set 13 to the load end. A small bearing 15 is provided between the motor input shaft 10 and the output shaft 18, a bearing 11 is provided between the planet carrier 12 and the motor rotor 7, and a bearing 23 is provided between the output shaft 18 and the front cover 24.

[0047] When both shape memory springs 22 connected to the multi-channel relays receive a low level, the cam lever 21 is in the intermediate state. At this time, the bidirectional controllable geared ratchet 16 is in a floating state. The elastic actuator has two energy output ports. If the output ports are blocked, when the motor rotor 7 rotates counterclockwise, the energy of the actuator flows to the elastic energy storage element 25 through the bidirectional controllable planetary differential mechanism, extending in the clockwise direction of the bidirectional controllable geared ratchet 16 until it reaches its limit extension. When the motor rotor 7 rotates clockwise, the bidirectional controllable geared ratchet 16 will rotate counterclockwise. At the same time, the energy stored in the elastic energy storage element 25 will be transferred to the bidirectional controllable geared ratchet 16. With the superposition of energy at both ends, the bidirectional controllable geared ratchet 16 will be in a state of counterclockwise accelerated rotation until the elastic energy storage element 25 returns to its original length and then becomes controlled by the actuator alone. Similarly, when the actuator starts to drive clockwise, it stores energy counterclockwise and releases elastic potential energy clockwise until it tends to a stable state.

[0048] Furthermore, this invention employs a nickel-titanium shape memory spring, utilizing the shape memory effect and plasticity of the novel material to make the control of the bidirectional controllable planetary differential mechanism more convenient.

[0049] Furthermore, the present invention employs a bidirectional controllable planetary differential mechanism, utilizing a bidirectional controllable gear ring ratchet 16 to make the energy storage direction of the driver controllable, thereby improving the driver's flexibility and increasing the driver's output states.

[0050] Furthermore, the bidirectional controllable gear ratchet 16 has a bearing 17 inside, the motor rotor 7 has a bearing 11 between it and the planetary carrier 12, and the input shaft 10 and the output shaft 18 have bearings 15 inside. This enables the driver to maintain stability while resisting shock and storing energy, and reduces energy loss caused by internal friction, resulting in low noise.

[0051] Furthermore, the present invention uses a frameless motor, which allows for the replacement of the basic components of the driver at any time according to environmental needs, thereby changing the input performance of the driver, and is convenient to disassemble and install.

[0052] Furthermore, the elastic energy storage element tension spring 25 is easy to replace, meaning that the spring specifications can be changed at any time to change the stiffness to adapt to different application scenarios, while also being inexpensive.

[0053] Furthermore, the overall weight of this invention is concentrated in the bidirectional controllable planetary differential mechanism and the frameless motor, achieving the lightweight characteristics of the entire shape memory spring bidirectional control planetary differential elastic drive.

[0054] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A planetary differential elastic actuator with bidirectional control of shape memory springs, characterized in that, It includes a housing, driver, input shaft, output shaft, shape memory bidirectional controllable planetary differential mechanism, and elastic energy storage element; The housing includes an encoder mounting bracket (1), a rear end cover (2) supporting the input shaft (10), a housing body (14) supporting two pawls (20) and fixing the driver stator, and a front end cover (24) for fixing the entire driver; the driver includes a motor rotor (7) and a motor stator (8), a bearing 1 (3) is provided between the rear end cover and the flange cover, the driver is connected to the input shaft (10) through the flange cover (5), and an encoder magnet (4) is installed inside the flange cover (5); The shape memory bidirectional controllable planetary differential mechanism includes a planetary carrier (12), a planetary gear set (13), a bidirectional controllable gear ring ratchet (16), a variable diameter spring (19), two pawls (20), a cam lever (21), a shape memory spring (22), and four tension springs (25). A bearing 3 (11) is provided between the planetary carrier (12) and the motor rotor end cover (6). The engagement of the spur teeth on the outside of the bidirectional controllable gear ring ratchet (16) with the two pawls (20) achieves bidirectional controllability. The rotation direction of the geared ratchet (16) is controlled by two pawls (20) which are fixed to the housing through circular grooves and variable diameter springs (19). The cam lever (21) is connected to the housing body (14) by screws. A shape memory spring (22) is provided between the cam lever (21) and the housing body (14) and is connected by a cable tie. The bidirectional controllable geared ratchet (16) is connected to the elastic energy storage element (25) through holes. The elastic energy storage element is composed of four tension springs (25).

2. The planetary differential elastic actuator with bidirectional control of shape memory springs according to claim 1, characterized in that: In the shape memory bidirectional controllable planetary differential mechanism, the variable diameter spring (19) has a top diameter of 2.5 mm, a bottom diameter of 5 mm, and a height of 5 mm; the bidirectional controllable gear ratchet (16) has straight teeth with a module of 0.5, 100 teeth, and a pressure angle of 20° inside, and ratchet teeth with a module of 0.25, 215 teeth, and a pressure angle of 20° outside; each of the two pawls (20) has four ratchet teeth with a module of 0.25, 4 teeth, and a pressure angle of 20° on each pawl; the cam lever (21) has a total length of 15.8 mm; the shape memory spring (22) has an outer diameter of 4 mm, a wire diameter of 0.5 mm, and a length of 30 mm; and the four tension springs (25) have an outer diameter of 5 mm and a wire diameter of 1 mm. The length including the hook is 20mm. The planetary gear set (13) adopts a sun gear with a module of 0.5, a number of teeth of 20, and a pressure angle of 20° and three planetary gears with a module of 0.5, a number of teeth of 40, and a pressure angle of 20°. The reduction ratio is 6. The rotation direction of the bidirectional controllable gear ring ratchet (16) can be controlled by two pawls (20). The reciprocating motion of the two pawls (20) is realized by the variable diameter spring (19). The cam lever (21) is controlled by the thermal contraction of the shape memory spring (22). The change of energy storage direction and the energy release direction are realized by the left and right swing of the cam lever (21). The four tension springs (25) mainly realize the energy storage and release characteristics.

3. The planetary differential elastic actuator with bidirectional control of shape memory springs according to claim 1, characterized in that: The shape memory spring (22) is made of nickel-titanium alloy and has shape memory effect and superelasticity. The energization and de-energization of the shape memory spring (22) are controlled by a multi-channel relay. When one end of the external relay receives a high level and the other end receives a low level, the shape memory spring (22) at the high level end is energized and thermally contracted, while the shape memory spring (22) at the low level end is de-energized and stretched, so that the pawl at the low level end is in an engaged state, while the high level end is in an unengaged state. At this time, it is used as a ratchet and pawl mechanism. Conversely, when one end of the relay receives a low level and the other end receives a high level, the cam lever is moved to the other side, changing the control direction of the ratchet and pawl, realizing the bidirectional controllable gear ring ratchet function. When both relays receive a low level, the shape memory spring (22) returns to its original length, and the bidirectional controllable gear ring ratchet (16) is in a floating state. At this time, the driver has two energy output ports.

4. The planetary differential elastic actuator with bidirectional control of shape memory springs according to claim 1, characterized in that: The inner ring of the motor stator (8) of the driver is fixed to the housing body (14) by a cylindrical specific retaining adhesive; the motor rotor (7) of the driver is composed of a magnet (702) and a magnet (701) and a motor rotor end cover (6), and is connected to the rear end cover (2) through a flange cover (5) and a bearing 1 (3); a shape memory bidirectional controllable planetary differential mechanism is installed in the inner cavity of the housing body (14) supporting the motor stator (8), realizing bidirectional control of the bidirectional controllable gear ratchet (16) and two controllable energy storage directions.

5. The planetary differential elastic actuator with bidirectional control of shape memory springs according to claim 1, characterized in that: The bidirectional controllable gear ratchet is provided with a bearing 5 (17) inside, and the bearing 2 (9) is embedded inside the main body (14) of the housing; a bearing 3 (11) is provided between the planetary carrier (12) and the motor rotor (7), and a bearing 4 (15) is provided between the output shaft (18) and the input shaft (10), with the bearing 4 (15) placed at the end of the output shaft (18); a bearing 6 (23) is provided between the front end cover (24) and the output shaft (18) to reduce internal friction.

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