Variable stiffness mechanism and dexterous manipulator
By using a variable stiffness mechanism in the robot and adjusting the stiffness coefficient of the transmission shaft in series, the problem that the robot is difficult to compatible with rigidity and flexibility when grasping objects of different forms is solved, and flexible stiffness changes and high-precision gripping effects are achieved.
Patent Information
- Application Number
- CN202421887549.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-05
- Publication Date
- 2025-05-27
- Estimated Expiration
- 2034-08-05
AI Technical Summary
When existing robots grasp objects of different shapes, their stiffness and flexibility are difficult to compatible, resulting in insufficient or excessive clamping force, and are prone to damage in complex environments.
The variable stiffness mechanism is adopted, including input parts, planetary wheel components, elastic parts, adjustment outer rings and adjustment components, and the stiffness coefficient of the transmission shaft is adjusted in series to achieve flexible stiffness changes.
When contacting unknown complex objects, the robot can maintain high flexibility and applicability, while maintaining the accuracy during grip to avoid insufficient grip strength caused by elastic deformation.
Smart Images
Figure CN222904063U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a manipulator, in particular to a variable stiffness mechanism of a manipulator. Background Art
[0002] The five-finger dexterous hand is an important component of the end effector of a robot. Generally installed at the end of the robot's wrist, it is a device that directly executes tasks. As the last link and the executing component for the robot to interact with the environment, the five-finger dexterous hand plays a very important role in improving the flexibility and usability of the robot. The quality of its performance largely determines the working performance of the entire robot.
[0003] Currently, relatively representative dexterous hands include Shadow in the UK, Festo in Germany, Tesla in the US, DLR / HIT in China, and ILDA in South Korea.
[0004] Conventional manipulators generally use motors to drive transmission mechanisms to drive the fingers to bend. However, the compliance of the manipulator is insufficient. When the objects to be grasped have various shapes, especially when grasping hard objects and soft objects respectively, it will be unsuitable. For example, when grasping a hard object (dumbbell), the clamping force is insufficient and it will fall off, or when grasping a thin and light object (straw, cake, cotton), the clamping force is too large and the object will be damaged. In addition, due to the particularity of mechanical transmission, when facing collisions and impacts in a complex external environment, it is very easy to damage the joint motors and reducers.
[0005] There are generally two types of mechanisms for the variable stiffness mechanism of the end dexterous hand of a robot, namely the antagonistic type and the series type. The series type uses an active non-linear elastic mechanism to connect the actuator and the load side. The driving force is generated by the driver, and the sub-driver adjusts the stiffness of the non-linear elastic mechanism by adjusting the lever arm or mechanism. The disadvantage of this method is that the actuator does not participate in the torque output of the mechanism, increasing more weight and size and having low energy utilization. In the antagonistic variable stiffness mechanism, the load is connected to two actuators through two non-linear elastic mechanisms. The two drivers apply preloads to the elastic elements in advance to change the equilibrium state of the two non-linear elastic mechanisms, thereby generating the ability to actively change the joint stiffness. The disadvantage of this method is that two actuators are used to drive one degree of freedom, increasing the complexity of the system (for example, patent CN112518796B - Antagonistic drive type multi-configuration cable-driven hand claw mechanism).
[0006] The stiffness of existing dexterous hands is generally determined by the performance of their mechanisms and motors. If it is necessary to adapt to different environmental changes, the compliance of the mechanism needs to be increased. Limited by the volume of the robot dexterous hand, previously, the material of the hand was generally changed to use elastic or flexible materials. Although the manipulator using material deformation has excellent performance in compliance, it is undeniable that the acquisition of such compliance performance is based on sacrificing the high-precision grasping performance.
[0007] The information disclosed in this background section is only intended to increase the understanding of the overall background of the present utility model and should not be regarded as an admission or any form of suggestion that this information constitutes the prior art known to those of ordinary skill in the art. Summary of the Utility Model
[0008] The technical problem to be solved by the present utility model is: how to solve the problem that the current requirements for the stiffness and compliance of the manipulator cannot be compatible.
[0009] The present utility model realizes the solution of the above technical problems through the following technical means:
[0010] A variable stiffness mechanism, including an input member, a planetary gear assembly, an elastic member, an adjusting outer ring, and an adjusting assembly. The input member is drivingly connected to the planetary gear assembly. One ends of a plurality of elastic members are evenly connected to the outer ring of the planetary gear assembly. The other ends of the elastic members are connected to the adjusting outer ring. The outside of the adjusting outer ring is connected to the adjusting assembly.
[0011] In the variable stiffness principle of the present utility model, a series connection method is adopted. The input member mainly outputs torque and rotational speed. The adjusting assembly adjusts the stiffness coefficient of the transmission shaft of the input member from the side through the mechanism. To ensure the effect of variable stiffness, when the adjusting outer ring rotates by an angle α, the internal transmission ratio of the planetary gear assembly is i. Therefore, the adjusting assembly needs to rotate in the reverse direction by an angle of i*α accordingly. Thanks to the participation of the variable stiffness mechanism of the present utility model, the dexterous manipulator can maintain high compliance and applicability when contacting unknown complex objects, and at the same time, it does not lack the accuracy during grasping. When grasping a heavy object, it will not cause insufficient gripping force due to the elastic deformation of the hand mechanism, and finally cause the grasped object to fall.
[0012] Preferably, the planetary gear assembly includes a sun gear, planetary gears, a planetary carrier, and an internal gear. A plurality of the planetary gears are circumferentially arrayed along the sun gear. The sun gear meshes with the plurality of planetary gears. The planetary gears mesh with the internal gear. The central axes of the plurality of planetary gears are rotatably connected to the planetary carrier.
[0013] Preferably, the transmission ratio between the planetary carrier and the sun gear is i.
[0014] Preferably, the adjusting assembly includes a worm, a worm wheel disposed on the outer surface of the adjusting outer ring, and an adjusting motor. The worm wheel meshes with the worm, and the adjusting motor is connected to the worm.
[0015] Preferably, the adjusting assembly includes a first adjusting gear, a second adjusting gear disposed on the outer surface of the adjusting outer ring, and an adjusting motor. The first adjusting gear meshes with the second adjusting gear, and the adjusting motor is connected to the first adjusting gear.
[0016] Preferably, the elastic member is one or a combination of a rubber elastic strip and a spring.
[0017] The elastic member provides conditions for flexibility.
[0018] Preferably, the input member is an input motor.
[0019] The present utility model also discloses a dexterous manipulator, which includes a first finger joint, a second finger joint, and the above variable stiffness mechanism. The first finger joint is connected to the second finger joint through the variable stiffness mechanism.
[0020] Preferably, the planetary gear assembly includes a sun gear, planetary gears, a planetary carrier, and an internal gear. A plurality of the planetary gears are circumferentially arrayed along the sun gear. The sun gear meshes with the plurality of planetary gears, and the planetary gears mesh with the internal gear. The central axes of the plurality of planetary gears are rotatably connected to the planetary carrier. One end of the planetary carrier is connected to the total output shaft, and the total output shaft is connected to the second finger joint.
[0021] Preferably, the input member is an input motor, and the input motor is fixed at the end of the first finger joint.
[0022] The advantages of the present utility model are as follows:
[0023] In the variable stiffness principle of the present utility model, a series connection method is adopted. The input member mainly outputs torque and rotational speed, and the adjusting assembly adjusts the stiffness coefficient of the transmission shaft of the input member from the side through the mechanism. To ensure the effect of variable stiffness, when the adjusting outer ring rotates by an angle α, the internal transmission ratio of the planetary gear assembly is i. Therefore, the adjusting assembly needs to reverse by an angle of i*α accordingly. Thanks to the participation of the variable stiffness mechanism of the present utility model, the dexterous manipulator can maintain high compliance and applicability when contacting unknown complex objects, and at the same time, it does not lack the accuracy during grasping. When grasping a heavy object, it will not cause insufficient gripping force due to the elastic deformation of the hand mechanism, and finally cause the grasped object to fall.
[0024] The dexterous manipulator of the present utility model can change the finger bending rigidity according to different objects to be grasped. When it is necessary to grasp a heavy object, the finger bending rigidity increases, and the grasping is more powerful. When a handshake action is required, the control bending stiffness is weakened to better adapt to the smoothness of the handshake.
[0025] The utility model is not limited to be applied to a dexterous manipulator, and can also be extended to other rotating joints. Description of the Drawings
[0026] Figure 1 is the schematic diagram of the variable stiffness mechanism of the embodiment of the utility model;
[0027] Figure 2 is the structural schematic diagram of the variable stiffness structure of the embodiment of the utility model;
[0028] Figure 3 is the connection schematic diagram of the planetary gear assembly, the elastic member and the adjusting outer ring of the embodiment of the utility model;
[0029] Figure 4 is the structural schematic diagram of the elastic member of the embodiment of the utility model;
[0030] Figure 5 is the structural schematic diagram of the elastic member of the embodiment of the utility model;
[0031] Figure 6 is the cross-sectional view of the dexterous manipulator of the embodiment of the utility model;
[0032] Figure 7 is Figure 6 the cross-sectional view at C-C in
[0033] Reference numerals in the drawings:
[0034] 1. Input member; 2. Planetary gear assembly; 21. Sun gear; 22. Planet gear; 23. Planet carrier; 24. Internal gear; 3. Elastic member; 4. Adjusting outer ring; 5. Adjusting assembly; 51. Worm; 52. Worm gear; 53. Adjusting motor; 6. First finger joint; 7. Second finger joint; 8. Total output shaft. Detailed Embodiments
[0035] To make the objectives, technical solutions and advantages of the embodiments of the utility model clearer, the technical solutions in the embodiments of the utility model will be clearly and completely described below in conjunction with the embodiments of the utility model. Apparently, the described embodiments are some but not all of the embodiments of the utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the utility model without making creative efforts shall fall within the scope of protection of the utility model.
[0036] Embodiment 1:
[0037] As Figure 1As shown in the figure, the principle on which this embodiment is based is as follows: The driving end transmits torque outward through the output shaft. There is a variable stiffness mechanism connected between the output shaft and the input shaft. The adjusting motor (sub-driver) in the variable stiffness mechanism adjusts the tension of the elastic member 3 by the rotation angle of the motor. When the rigidity between the driving end and the load needs to be increased, the adjusting motor rotates the angle and preloads a certain force on the elastic member 3 in advance. If the material of the elastic member 3 changes the force but does not change the deformation, the rigidity of the material becomes larger, and then the rigidity between the input shaft and the output shaft becomes larger; on the contrary, the rotation angle of the adjusting motor is reduced, the force preloaded on the elastic material is reduced, the rigidity of the material becomes smaller, and then the rigidity between the input shaft and the output shaft becomes smaller, and the flexibility of the mechanism increases accordingly.
[0038]
[0039] (T remains unchanged, θ decreases, K value increases)
[0040] (θ remains unchanged, T decreases, K value increases)
[0041] K: Stiffness value, T: Torque, θ: Rotation angle
[0042] The theoretical formula is as above. When the torque remains unchanged and the rotation angle is reduced (such as K1), or when the torque is increased and the rotation angle of the motion is absorbed by the structure (such as K2), that is, the stiffness changes.
[0043] In this embodiment, as Figure 1 、 Figure 7 shown, the variable stiffness mechanism includes an input member 1, a planetary gear assembly 2, an elastic member 3, an adjusting outer ring 4, and an adjusting assembly 5. The input member 1 is drivingly connected to the planetary gear assembly 2. One ends of a plurality of elastic members 3 are evenly connected to the outer ring of the planetary gear assembly 2. The other ends of the elastic members 3 are connected to the adjusting outer ring 4. The outside of the adjusting outer ring 4 is connected to the adjusting assembly 5. The input member 1 drives the planetary gear assembly 2 to rotate, and the rotation angles of the planetary gear assembly 2 and the adjusting outer ring 4 change by an angle α. The internal transmission ratio of the planetary gear assembly 2 is i, and the adjusting assembly 5 drives the adjusting outer ring 4 to rotate reversely by an angle of i*α.
[0044] Specifically, the input member 1 is an input motor.
[0045] The planetary gear assembly 2 includes a sun gear 21, planetary gears 22, a planetary carrier 23, and an internal gear 24. A plurality of the planetary gears 22 are arranged in a circumferential array along the sun gear 21. The sun gear 21 meshes with the plurality of planetary gears 22. The planetary gears 22 mesh with the internal gear 24. The central axes of the plurality of planetary gears 22 are rotatably connected to the planetary carrier 23. The output shaft of the input motor is connected to the sun gear 21. The input member 1 drives the sun gear 21 to rotate, thereby driving the plurality of planetary gears 22 to rotate around their own axes and revolve along the internal teeth of the internal gear 24 at the same time. The planetary carrier 23 is connected to the planetary gears 22. When the planetary gears 22 revolve, the planetary carrier 23 rotates accordingly. The revolution of the planetary gears 22 transmits torque through the planetary carrier 23. The planetary carrier 23 serves as the output end of the entire variable stiffness mechanism. The transmission ratio between the planetary carrier 23 and the sun gear 21 is i. Among them, the internal gear 24 does not participate in torque transmission, but it bears the reverse torque of the planetary gears 22 due to their rotation and revolution.
[0046] In this embodiment, there are three planetary gears 22, and the planetary carrier 23 is of an annular structure. However, the number of planetary gears 22 and the specific structure of the planetary carrier 23 are not limited in this embodiment. At the same time, the transmission ratio i between the planetary carrier and the sun gear 21 can also be adjusted.
[0047] An elastic member 3 is provided between the internal gear 24 and the adjusting outer ring 4. The reverse torque of the internal gear 24 is transmitted to the adjusting outer ring 4 through the elastic member 3.
[0048] In this embodiment, with reference to Figure 2 , Figure 7 shown, the adjusting assembly 5 includes a worm 51, a worm gear 52 provided on the outer surface of the adjusting outer ring 4, and an adjusting motor 53. The worm gear 52 meshes with the worm 51. The adjusting motor 53 is connected to the worm 51.
[0049] The adjusting outer ring 4 meshes with the worm 51. When the adjusting motor 53 rotates, the worm 51 rotates, and the rotation angles of the adjusting outer ring 4 and the internal gear 24 change by α, and the elastic member 3 deforms under force. In the above mechanism, to ensure the effect of variable stiffness, when the elastic member 3 deforms under force, the reverse torque increases, but the relative angle between the total output shaft 8 of the variable stiffness mechanism and the output shaft of the input motor cannot change. Therefore, the adjusting motor 53 needs to reverse by an angle of i*α accordingly.
[0050] In this embodiment, the worm gear meshes with the adjusting outer ring 4 through a worm and worm gear mechanism. The end of the worm 51 is connected to the adjusting motor 53. The rotation angle of the adjusting motor 53 drives the adjusting outer ring 4 to rotate. Due to the use of a worm and worm gear transmission, there is a locking mechanism, and the worm gear cannot drive the worm 51 in the reverse direction. Compared with other adjusting mechanisms, the adjusting motor 53 only needs to rotate according to the required adjusting angle and does not need to be energized for a long time to continuously output torque.
[0051] Embodiment 2:
[0052] The adjusting assembly 5 includes a first adjusting gear, a second adjusting gear arranged on the outer surface of the adjusting outer ring 4, and an adjusting motor 53. The first adjusting gear meshes with the second adjusting gear, and the adjusting motor 53 is connected to the first adjusting gear.
[0053] The rotational angle change between the adjusting motor 53 and the adjusting outer ring 4 can be transmitted through other mechanical transmission methods such as gears, chains, linkages, and hydraulics.
[0054] Embodiment Three:
[0055] Elastic members 3 are evenly distributed outside the adjusting outer ring 4 and the inner gear 24 based on the central axis. The elastic members 3 are one or a combination of rubber elastic strips and springs.
[0056] As Figure 2 、 Figure 5 shown, the elastic member 3 is a rubber elastic member. As Figure 3 shown, the elastic member 3 is a spring. As Figure 4 shown, the elastic member 3 adopts a composite fiber elastic material. Different elastic materials and distributions can be selected according to the stiffness K value requirements in specific work.
[0057] In this embodiment, the original rigid characteristics of the elastic material can be changed by varying the material, quantity, and cross-sectional shape of the material.
[0058] Embodiment Four:
[0059] As Figure 6 、 Figure 7 shown, this embodiment discloses a dexterous manipulator, including a first finger joint 6, a second finger joint 7, and the variable stiffness mechanism in the above embodiment. The first finger joint 6 is connected to the second finger joint 7 through the variable stiffness mechanism.
[0060] Specifically, the planetary gear assembly 2 includes a sun gear 21, planetary gears 22, a planetary carrier 23, and an inner gear 24. A plurality of the planetary gears 22 are circumferentially arrayed along the sun gear 21. The sun gear 21 meshes with the plurality of planetary gears 22. The planetary gears 22 mesh with the inner gear 24. The central axes of the plurality of planetary gears 22 are rotatably connected to the planetary carrier 23.
[0061] The input member 1 is connected to the sun gear 21. One end of the total output shaft 8 of the variable stiffness mechanism is connected to the planetary carrier 23, and the other end is connected to the second finger joint 7.
[0062] The input member 1 is connected to the sun gear 21. The input member 1 drives the sun gear 21 to rotate, and then drives multiple planet gears 22 to rotate around their own axes while revolving along the internal teeth of the internal gear 24. The planet carrier 23 is connected to the planet gears 22. When the planet gears 22 revolve, the planet carrier 23 rotates accordingly. The revolution of the planet gears 22 transmits torque through the planet carrier 23. The planet carrier 23 serves as the total output shaft 8 of the entire variable stiffness mechanism. One end of the total output shaft 8 is connected to the second finger joint 7, thereby transmitting the torques after variable stiffness to the second finger joint 7.
[0063] In this embodiment, the first finger joint 6 is the proximal finger joint, and the second finger joint 7 is the middle finger joint. The input member 1 is fixed at the end of the proximal finger joint. After the output of the input member 1 rotates, it is output again through the variable stiffness mechanism, and the torque is transmitted to the middle finger joint through the total output shaft 8.
[0064] Based on the principle of variable stiffness in the first embodiment, the adjustment motor 53 and the elastic member 3 can be arranged between the output shaft and the input shaft, or between the output shaft and the load, or between the driving end and the input shaft. As long as the variable stiffness of the load can be finally achieved.
[0065] It should be noted that: this embodiment can also be extended and used on other joints, not limited to robotic hands.
[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A variable stiffness mechanism, characterized in that: It includes an input part, a planetary gear assembly, an elastic part, an adjusting outer ring, and an adjusting assembly. The input part is driven and connected to the planetary gear assembly. The outer ring of the planetary gear assembly is evenly connected to one end of multiple elastic parts. The other end of the elastic part is connected to the adjusting outer ring. The outside of the adjusting outer ring is connected to the adjusting assembly.
2. The variable stiffness mechanism according to claim 1, characterized in that: The planetary gear assembly includes a sun gear, planetary gears, a planet carrier, and an internal gear. A plurality of the planetary gears are arrayed along the circumference of the sun gear. The sun gear is meshed with the plurality of the planetary gears. The planetary gears are meshed with the internal gear. The central axes of the plurality of the planetary gears are rotatably connected to the planet carrier.
3. The variable stiffness mechanism according to claim 2, characterized in that: The transmission ratio between the planet carrier and the sun gear is i.
4. The variable stiffness mechanism according to claim 1, characterized in that: The adjusting assembly comprises a worm, a worm wheel arranged on the outer surface of an adjusting outer ring, and an adjusting motor. The worm wheel is meshed with the worm, and the adjusting motor is connected to the worm.
5. The variable stiffness mechanism according to claim 1, characterized in that: The adjusting assembly includes a first adjusting gear, a second adjusting gear arranged on the outer surface of the adjusting outer ring, and an adjusting motor. The first adjusting gear is meshed with the second adjusting gear, and the adjusting motor is connected to the first adjusting gear.
6. The variable stiffness mechanism according to claim 1, characterized in that: The elastic member is one or a combination of a rubber elastic strip and a spring.
7. The variable stiffness mechanism according to claim 1, characterized in that: The input member is an input motor.
8. A dexterous manipulator, characterized in that: It comprises a first knuckle, a second knuckle, and a variable stiffness mechanism according to any one of claims 1 to 7, wherein the first knuckle and the second knuckle are connected via the variable stiffness mechanism.
9. The dexterous manipulator according to claim 8, characterized in that: The planetary gear assembly comprises a sun gear, planetary gears, a planet carrier, and an internal gear. A plurality of the planetary gears are arrayed along the circumference of the sun gear. The sun gear is meshed with the plurality of the planetary gears. The planetary gears are meshed with the internal gear. The central axes of the plurality of the planetary gears are rotatably connected with the planet carrier. The planet carrier is connected to one end of the total output shaft, and the total output shaft is connected to the second finger joint.
10. The dexterous manipulator according to claim 8, characterized in that: The input member is an input motor, and the input motor is fixed at the end of the first finger joint.