A reconfigurable nonlinear variable stiffness actuator

Abstract

The application discloses a reconfigurable nonlinear variable stiffness actuator and belongs to the technical field of robots. The reconfigurable nonlinear variable stiffness actuator comprises a shell, one side of the shell is provided with a driving input end for mounting a frameless torque motor, the other side of the shell is provided with an output plate for changing the stiffness response of the system, further comprises a transmission shaft coaxially installed in the driving input end and fixed with a rotor of the frameless torque motor, a sliding assembly arranged in the shell and equidistantly distributed along the circumference of the shell, a spring piece connected to the transmission shaft and sliding in the sliding assembly, wherein the output plate is provided with a curve groove equidistantly opened along the circumferential direction, the sliding assembly slides in the curve groove, and the output plate is driven to rotate by the sliding assembly. The reconfigurable nonlinear variable stiffness actuator has a wide stiffness adjustment range, can adjust the output stiffness in real time according to different external loads, and can effectively improve the human-machine interaction safety during the use of the robot.

Description

Technical Field

[0001] This invention relates to the field of robotics, and more particularly to a reconfigurable nonlinear variable stiffness actuator. Background Technology

[0002] With the rapid development of robotics technology and industry, human-robot interactions are becoming increasingly frequent. Safety issues during human-robot interaction should be a major concern, and the use of flexible joints in robots is an effective solution. As a typical example of flexible joints, variable stiffness actuators have the characteristics of biomimetic joints—they can adjust their stiffness according to the magnitude of external contact loads.

[0003] Currently, existing variable stiffness actuators can be divided into two types: active and passive. Active variable stiffness actuators require an additional drive source for stiffness adjustment, resulting in a larger system size and mass, and also increasing the difficulty of control. Nonlinear stiffness actuators can passively adjust their own stiffness in real time according to the magnitude of the external load, without the need for an additional power source. They can be directly integrated into the robot's joints through a frameless torque motor, providing high torque density and precise motion control, which is beneficial for the miniaturization and weight reduction of robot systems. In addition, the stiffness adjustment range of the actuator can be increased through reconfigurable structural design.

[0004] However, existing nonlinear stiffness actuator systems are often complex in design and have limited stiffness adjustment range, making it difficult to meet the needs of different application scenarios. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of complex design and limited stiffness adjustment range of nonlinear stiffness actuator systems in the prior art. It proposes a reconfigurable nonlinear variable stiffness actuator, which can adapt to external loads, reduce the structural complexity of the actuator, improve adaptability to different application scenarios, and thus realize the driving of robots and safe human-machine interaction.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A reconfigurable nonlinear variable stiffness actuator includes a housing, which is a hollow ring structure. A drive input end is provided on one side of the housing for mounting a frameless torque motor, and an output plate is provided on the other side of the housing for changing the stiffness response of the system. The actuator also includes: a drive shaft, coaxially mounted within the drive input end, for connecting an external bionic joint and tightly fitted to the rotor of the frameless torque motor; and a stiffness adjustment unit connected to the drive shaft and rotating with it to adjust the output stiffness of the device. The output plate has equidistant curved grooves along its circumference, and the housing has equidistant straight grooves along its circumference. The stiffness adjustment unit slides simultaneously within both the curved grooves and the straight grooves, and the output plate is rotated by the stiffness adjustment unit.

[0007] In order to adjust the overall stiffness of the actuator in real time, preferably, the stiffness adjustment unit includes a spring connected to the drive shaft and a sliding assembly that slides in the curved groove and the straight groove. The spring is clamped in the sliding assembly, and the effective working length of the spring is adjusted by the sliding assembly.

[0008] To further modify the reconfigurability and stiffness range of the actuator, rectangular slots for mounting springs are uniformly formed on the outer edge of the drive shaft.

[0009] In order to adjust the effective working length of the spring according to the change of external load, the sliding assembly further includes a sliding frame, on which a sliding pin is fixedly installed. The sliding pin is slidably connected in the curved groove and the straight groove, and a sliding shaft is symmetrically arranged in the sliding frame. An inter-shaft sleeve is sleeved on the sliding shaft, and ball bearings are installed at both ends of the inter-shaft sleeve. The spring is clamped between the symmetrical ball bearings.

[0010] In order to make adaptive adjustments according to the thickness of the spring, the sliding frame is further provided with adjustment grooves on both sides, and the two ends of the sliding shaft pass through the adjustment grooves and are installed with retaining rings between them and the outer wall of the sliding frame. The sliding frame is threaded with symmetrically arranged set screws, and the set screws on both sides are rotatably connected to the adjacent shaft sleeves respectively.

[0011] To prevent dust and foreign objects from entering the interior and affecting the operation of the equipment, preferably, the drive input end includes an end cover fixedly connected to the housing and a mounting flange fixedly installed on the end cover, and the stator of the frameless torque motor is fixed inside the mounting flange.

[0012] To monitor the rotation angle of the frameless torque motor, the drive input terminal further includes a first encoder fixedly mounted on the mounting flange, the first encoder being used to monitor the rotation angle of the frameless torque motor.

[0013] To monitor the rotation angle and speed of the drive shaft, preferably, the reconfigurable nonlinear variable stiffness actuator further includes a second encoder, which is fixedly mounted on the drive shaft and located inside the housing, wherein the second encoder includes a reading head and a magnetic ring.

[0014] To effectively reduce vibration caused by rotation and reduce wear caused by friction, preferably, a connecting bearing is provided inside the output plate to support the drive shaft.

[0015] To reduce mechanical wear between the output board and the housing, preferably, the output board is connected to the housing via a spacer, which is used to maintain a gap between the output board and the housing.

[0016] Compared with the prior art, the present invention provides a reconfigurable nonlinear variable stiffness actuator, which has the following beneficial effects: This reconfigurable nonlinear variable stiffness actuator, when the frameless torque motor is started, the rotor and the drive shaft rotate together. The rotation of the drive shaft drives the reed to rotate at the same time. During the rotation of the reed, the sliding component drives the output plate to rotate together. When the output plate comes into contact with an external obstacle, the sliding component slides in the curved groove of the output plate. The movement of the sliding component increases the effective length of the reed, thereby reducing the output stiffness of the actuator, thus achieving the purpose of safe interaction with the external environment. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of a reconfigurable nonlinear variable stiffness actuator proposed in this invention. Figure 1 ; Figure 2 This is a schematic diagram of the overall structure of a reconfigurable nonlinear variable stiffness actuator proposed in this invention. Figure 2 ; Figure 3 This is a schematic diagram of the overall structure of a reconfigurable nonlinear variable stiffness actuator without an output plate, as proposed in this invention. Figure 4 This is a schematic side view of the reconfigurable nonlinear variable stiffness actuator proposed in this invention. Figure 5 This invention proposes a reconfigurable nonlinear variable stiffness actuator. Figure 4 Sectional view; Figure 6 This is a schematic diagram of the sliding component structure of a reconfigurable nonlinear variable stiffness actuator proposed in this invention.

[0018] In the diagram: 1. Outer shell; 101. Straight groove; 2. Drive input terminal; 201. End cover; 202. Mounting flange; 203. First encoder; 3. Frameless torque motor; 4. Output board; 401. Curved groove; 5. Drive shaft; 501. Rectangular groove; 6. Reed; 7. Sliding assembly; 701. Sliding frame; 702. Sliding pin; 703. Sliding shaft; 704. Inter-shaft sleeve; 705. Ball bearing; 706. Adjusting groove; 707. Retaining ring; 708. Set screw; 8. Second encoder; 801. Reading head; 802. Magnetic ring; 9. Connecting bearing; 10. Spacer. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] Example: Reference Figures 1-6A reconfigurable nonlinear variable stiffness actuator includes a housing 1 with a viewing window, which is a hollow ring structure providing physical support for the entire device and protecting the internal components from external environmental influences. A drive input terminal 2 is located on one side of the housing 1 for mounting a frameless torque motor 3, and an output plate 4 is located on the other side of the housing 1 for changing the system's stiffness response. It also includes a drive shaft 5, coaxially mounted within the drive input terminal 2, for connecting an external bionic joint, which is tightly fitted to the rotor of the frameless torque motor 3. The frameless torque motor 3 serves as the power source, directly driving... The rotation of the drive shaft 5 helps to reduce the overall size and improve efficiency. The stiffness adjustment unit is connected to the drive shaft 5 and rotates with the drive shaft 5 to adjust the output stiffness of the device. The output plate 4 has curved grooves 401 equidistantly arranged along the circumferential direction, and the outer shell 1 has straight grooves 101 equidistantly arranged along the circumferential direction. The stiffness adjustment unit slides in both the curved grooves 401 and the straight grooves 101, and drives the output plate 4 to rotate, so that the stiffness adjustment unit can automatically adjust its position according to the change of external load, thereby changing the stiffness response of the system.

[0022] When the reconfigurable nonlinear variable stiffness actuator is in use, the frameless torque motor 3 starts and drives the transmission shaft 5 to rotate. Since the stiffness adjustment unit is connected to the transmission shaft 5, it will also rotate. During this process, if the external load changes, the stiffness adjustment unit can automatically adjust its position according to the change of the external load, thereby changing the stiffness response of the system. At the same time, the stiffness adjustment unit will also slide along the curved groove 401 on the output plate 4 and the straight groove 101 on the outer shell 1 to ensure that the output plate 4 can be adjusted at the required angle, and finally achieve precise driving of the bionic joint or other connecting parts.

[0023] Reference Figure 1 and Figure 5 Preferably, the stiffness adjustment unit includes a spring 6 connected to the drive shaft 5. Specifically, rectangular grooves 501 for mounting the spring 6 are evenly provided on the outer edge surface of the drive shaft 5, thereby fixing the spring 6. The number of springs 6 installed is proportional to the reconfigurability of the device, so as to change the reconfigurability and stiffness range of the actuator. A sliding assembly 7 slides in the curved groove 401 and the straight groove 101. The spring 6 is clamped in the sliding assembly 7, and the effective working length of the spring 6 is adjusted by the sliding assembly 7, so that the spring 6 can automatically adjust its position under different load conditions, thereby changing the stiffness response of the entire system.

[0024] With the above settings, when the frameless torque motor 3 drives the transmission shaft 5 to rotate, the reed 6 rotates together with the transmission shaft 5. At the same time, if the external load changes, the sliding component 7 will slide along the curved groove 401 and the straight groove 101 according to the load size, automatically adjusting the effective working length of the reed 6. This process changes the degree of bending of the reed 6, thereby adjusting the overall stiffness of the actuator in real time. This design not only realizes the adaptive response to external loads, but also significantly expands the stiffness adjustment range of the actuator, making it more suitable for diverse application scenarios.

[0025] Reference Figure 6 The sliding assembly 7 includes a sliding frame 701, on which a sliding pin 702 is fixedly mounted. The sliding pin 702 is slidably connected in the curved groove 401 and the straight groove 101, allowing the entire sliding assembly 7 to translate along these grooves. It also includes a sliding shaft 703 symmetrically arranged in the sliding frame 701. An inter-shaft sleeve 704 is sleeved on the sliding shaft 703. Ball bearings 705 are installed at both ends of the inter-shaft sleeve 704, providing low-friction support. The spring 6 is clamped between the symmetrical ball bearings 705, realizing sliding friction during the change of the length of the spring 6, thereby adjusting its effective working length according to the change of external load.

[0026] Reference Figure 6 The sliding frame 701 has adjustment grooves 706 on its upper and lower sides. The two ends of the sliding shaft 703 pass through the adjustment grooves 706 and are fitted with retaining rings 707 between them and the outer wall of the sliding frame 701. This ensures that the sliding shaft 703 can move freely within the adjustment grooves 706 while maintaining structural stability. The left and right sides of the sliding frame 701 are threaded with symmetrically arranged set screws 708. The set screws 708 on both sides are rotatably connected to the adjacent shaft sleeves 704. By finely adjusting the position of the shaft sleeves 704 through the set screws 708, the relative position between the two shaft sleeves 704 can be precisely controlled and can be varied according to the thickness of the spring 6.

[0027] When the frameless torque motor 3 drives the drive shaft 5 to rotate, the drive shaft 5 drives the spring 6 to rotate together. Since the spring 6 is clamped between two ball bearings 705, it can automatically adjust the degree of bending according to the change of external load. Specifically: 1. Adaptive stiffness adjustment: When the external load changes, the pressure or tension on the spring 6 will change its bending shape, resulting in a change in its effective working length. Since the spring 6 is clamped between the ball bearings 705, this change in bending shape will be converted into sliding motion of the sliding assembly 7 along the curved groove 401 and the straight groove 101; 2. Precise control: By adjusting the set screw 708, the distance between the two shaft sleeves 704 can be finely adjusted, which can vary according to the thickness of the spring 6. This design not only enhances the flexibility of the system, but also improves its adaptability to different application scenarios. 3. Stability and Reliability: The sliding shaft 703 is fixed to the outer wall of the sliding frame 701 by the retaining ring 707, ensuring the stability and reliability of the sliding assembly 7 throughout the entire operation process. Furthermore, the use of the ball bearing 705 reduces friction and improves the system's response speed and efficiency.

[0028] Through the above design, the sliding component 7 achieves dynamic adjustment of the effective working length of the reed 6, thereby enabling the actuator to automatically adjust its stiffness according to changes in external load. This mechanism not only simplifies system design and reduces complexity, but also significantly expands the stiffness adjustment range, making it more suitable for diverse application scenarios and improving the adaptability of the robot system and the safety of human-machine interaction.

[0029] It should be noted that, in order to prevent interference during operation, the frameless torque motor 3 can only drive the transmission shaft 5 to rotate at a small angle, such as within ±10°, to prevent the sliding component 7 from getting stuck in the linear groove 101.

[0030] Reference Figure 1 and Figure 5 The drive input end 2 includes an end cover 201 fixedly connected to the housing 1. The end cover 201 is firmly connected to the housing 1 by bolts or other fasteners, forming a closed space to accommodate key components such as the drive shaft 5 and the frameless torque motor 3, ensuring the mechanical strength and sealing of the entire device and preventing dust and foreign objects from entering the interior and affecting the operation of the equipment. The end cover 201 also includes a mounting flange 202 fixedly installed on the end cover 201. The stator of the frameless torque motor 3 is fixed inside the mounting flange 202. The design of the mounting flange 202 allows the frameless torque motor 3 to be tightly integrated into the overall structure of the actuator, thereby reducing the overall size of the system and improving mechanical rigidity and stability.

[0031] The drive input 2 not only provides a stable mounting base for the frameless torque motor 3, but also ensures the compactness and efficiency of the entire actuator structure. This integration helps simplify system design, improve mechanical efficiency, and enhance the safety and adaptability of human-machine interaction. Furthermore, the use of the frameless torque motor 3 further improves the actuator's dynamic performance and response speed, making it suitable for more complex robotic applications.

[0032] Reference Figure 1The drive input terminal 2 also includes a first encoder 203 fixedly mounted on the mounting flange 202, located near the frameless torque motor 3. The first encoder 203 is used to monitor the rotation angle of the frameless torque motor 3. The first encoder 203 detects the position change of the rotor of the frameless torque motor 3 by means of optics, magnetism or other technologies, and converts this information into electrical signals to feed back to the control system. This feedback mechanism is crucial for achieving high-precision position control, especially in application scenarios that require fast response and accurate positioning.

[0033] Reference Figure 2 and Figure 5 The reconfigurable nonlinear variable stiffness actuator also includes a second encoder 8, which is fixedly mounted on the drive shaft 5 and located inside the housing 1. The second encoder 8 includes a reading head 801 and a magnetic ring 802 for accurately monitoring the rotation angle and speed of the drive shaft 5.

[0034] Specifically, the magnetic ring 802 is fixedly mounted on the drive shaft 5 and rotates together with the drive shaft 5. The magnetic ring 802 has a specific magnetic pole distribution. When it rotates, the reading head 801 can detect these changes and generate corresponding signals.

[0035] In addition to the first encoder 203 monitoring the rotation angle of the frameless torque motor 3, the second encoder 8 provides an extra layer of monitoring, enhancing the system's reliability and safety. If one encoder fails, the other can still continue to provide necessary feedback, thus improving the overall system robustness. Furthermore, the second encoder 8 does not increase system complexity but effectively improves overall performance. For example, directly mounting the magnetic ring 802 on the drive shaft 5 reduces intermediate steps and improves signal accuracy and stability.

[0036] By integrating a second encoder 8, this reconfigurable nonlinear variable stiffness actuator achieves a higher level of control accuracy and reliability. The second encoder 8 consists of a reading head 801 and a magnetic ring 802, which are mounted on the drive shaft 5 and located inside the housing 1. It provides high-precision rotation angle and speed feedback. This design not only enhances the control capability of the system but also provides redundancy protection, improving the robustness and adaptability of the overall system. This makes the actuator particularly suitable for robot applications with high requirements for accuracy and reliability.

[0037] Reference Figures 1-5 The output plate 4 has a connecting bearing 9 inside, which is used to support the drive shaft 5.

[0038] By providing a low-friction, high-precision support point, the connecting bearing 9 enables the drive shaft 5 to maintain extremely high stability while rotating at high speed, effectively reducing vibration caused by rotation and reducing wear caused by friction.

[0039] By incorporating a connecting bearing 9 within the output plate 4, this reconfigurable nonlinear variable stiffness actuator significantly enhances the rotational stability of the drive shaft 5 and the overall system reliability. The connecting bearing 9 provides necessary support, reduces friction and vibration, and simultaneously strengthens the system's rigidity and dynamic response. Furthermore, this design works in conjunction with other key components such as the sliding assembly 7 and the second encoder 8 to achieve efficient and precise motion control, making it suitable for various complex robot applications. This optimized design not only improves the device's performance but also extends its service life, laying a solid foundation for safe and reliable human-machine interaction.

[0040] Reference Figure 2 The output board 4 is connected to the housing 1 via a spacer 10. The spacer 10 is used to maintain the gap between the output board 4 and the housing 1 to prevent direct contact or unnecessary friction between the two. This design helps to reduce mechanical wear, improve the reliability and lifespan of the system, and also helps to absorb small displacements caused by temperature changes or mechanical vibrations, thereby maintaining the stability and accuracy of the system.

[0041] Working principle: When the frameless torque motor 3 starts, the rotor rotates together with the transmission shaft 5. The rotation of the transmission shaft 5 drives the reed 6 to rotate. During the rotation of the reed 6, the sliding component 7 drives the output plate 4 to rotate together. When the output plate 4 comes into contact with an external obstacle, the sliding component 7 slides in the curved groove 401 of the output plate 4. The movement of the sliding component 7 increases the effective length of the reed 6, thereby reducing the output stiffness of the actuator, thus achieving the purpose of safe interaction with the external environment. During the rotation of the actuator, the first encoder 203 is used to monitor the rotation angle of the frameless torque motor 3, and the second encoder 8 is used to monitor the rotation angle of the drive shaft 5.

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A reconfigurable nonlinear variable stiffness actuator, comprising a housing (1) being a hollow ring structure, characterized in that, One side of the housing (1) is provided with a drive input terminal (2) for mounting a frameless torque motor (3), and the other side of the housing (1) is provided with an output plate (4) for changing the stiffness response of the system. The housing also includes: The drive shaft (5) is coaxially installed inside the drive input end (2) for connecting an external bionic joint and is tightly connected to the rotor of the frameless torque motor (3); A stiffness adjustment unit is connected to the drive shaft (5) and rotates together with the drive shaft (5) to adjust the output stiffness of the device; The output plate (4) is provided with curved grooves (401) at equal intervals along the circumferential direction, and the outer shell (1) is provided with straight grooves (101) at equal intervals along the circumferential direction. The stiffness adjustment unit slides in both the curved groove (401) and the straight groove (101) at the same time, and the output plate (4) is driven to rotate by the stiffness adjustment unit. The stiffness adjustment unit includes a spring (6) connected to the drive shaft (5), and The sliding assembly (7) slides within the curved groove (401) and the straight groove (101), and the spring (6) is clamped within the sliding assembly (7), and the effective working length of the spring (6) is adjusted by the sliding assembly (7). The sliding assembly (7) includes a sliding frame (701), on which a sliding pin (702) is fixedly mounted. The sliding pin (702) is slidably connected within the curved groove (401) and the straight groove (101). A sliding shaft (703) is symmetrically arranged in the sliding frame (701). An inter-shaft sleeve (704) is sleeved on the sliding shaft (703). Ball bearings (705) are installed at both ends of the inter-shaft sleeve (704). The spring (6) is clamped between the symmetrical ball bearings (705). The sliding frame (701) has adjustment grooves (706) on both sides. The two ends of the sliding shaft (703) pass through the adjustment grooves (706) and are fitted with retaining rings (707) between them and the outer wall of the sliding frame (701). The sliding frame (701) is threaded with symmetrically arranged set screws (708). The set screws (708) on both sides are rotatably connected to the adjacent shaft sleeves (704).

2. The reconfigurable nonlinear variable stiffness actuator according to claim 1, characterized in that, The outer edge of the drive shaft (5) is provided with rectangular grooves (501) for mounting springs (6).

3. A reconfigurable nonlinear variable stiffness actuator according to claim 1, characterized in that, The drive input terminal (2) includes an end cap (201) fixedly connected to the housing (1), and The stator of the frameless torque motor (3) is fixed inside the mounting flange (202) and fixedly installed on the end cover (201).

4. A reconfigurable nonlinear variable stiffness actuator according to claim 3, characterized in that, The drive input terminal (2) also includes a first encoder (203) fixedly mounted on the mounting flange (202), the first encoder (203) being used to monitor the rotation angle of the frameless torque motor (3).

5. A reconfigurable nonlinear variable stiffness actuator according to claim 1, characterized in that, The reconfigurable nonlinear variable stiffness actuator also includes a second encoder (8), which is fixedly mounted on the drive shaft (5) and located inside the housing (1). The second encoder (8) includes a reading head (801) and a magnetic ring (802).

6. A reconfigurable nonlinear variable stiffness actuator according to claim 1, characterized in that, The output plate (4) is provided with a connecting bearing (9) inside, which is used to support the transmission shaft (5).

7. A reconfigurable nonlinear variable stiffness actuator according to claim 1, characterized in that, The output board (4) is connected to the outer shell (1) through a spacer (10), which is used to maintain the gap between the output board (4) and the outer shell (1).

Images