CN112757277A

CN112757277A - Variable-rigidity flexible joint

Info

Publication number: CN112757277A
Application number: CN202110017936.5A
Authority: CN
Inventors: 张兰; 黄冠宇; 孔令雨; 陈令凯; 谢安桓; 张丹
Original assignee: Zhejiang Lab
Current assignee: Zhejiang Lab
Priority date: 2021-01-07
Filing date: 2021-01-07
Publication date: 2021-05-07

Abstract

The invention discloses a variable-rigidity flexible joint, which comprises: the rigidity adjusting motor, the worm, the driving disc, the shaft and the driven disc; the rigidity adjusting motor is connected with a worm, the worm is connected with a worm wheel of a driving disc through a transmission pair, the driven disc is arranged on the output end face of the driving disc, and the center of the driving disc is rotationally connected with the center of the driven disc through a shaft; the driven disc is uniformly distributed with 3 groups of spring mounting seats along the circumferential direction, each group of spring mounting seats is provided with a linear guide rail, the linear guide rail is provided with a sliding block, two sides of the sliding block are respectively and fixedly connected with one end of a spring, and the other end of the spring is fixedly connected with the spring mounting seats; the output end face of the driving disc is provided with 3 groups of T-shaped grooves distributed along the circumferential direction of the driving disc, the upper end of the sliding block is provided with a roller, and the roller is connected with the T-shaped grooves in a sliding mode. The variable-stiffness flexible joint realizes the variable-stiffness flexible joint by changing the pretightening force of the spring, and has the characteristics of compact structure and quick response.

Description

Variable-rigidity flexible joint

Technical Field

The invention relates to the technical field of robots, in particular to a variable-rigidity flexible joint.

Background

In the early design of robot joints, rigid joints are widely applied due to the advantages of simple structure, quick response and the like, but when the robot is impacted, the rigid joints do not have the functions of buffering and absorbing energy, so that the robot is easy to damage. With the development of bionics, some students inspire the flexibility of animal tendons in the motion process, and begin to apply flexible joints to the structural design of robots, such as adding linear springs to the legs of a legged robot, adding torsion springs to the joints of the robot, and the like. These methods usually use elastic elements with constant stiffness to make the structure flexible, which can relieve the impact and make the robot have better motion characteristics, but still have larger difference compared with the animal joints. Research shows that the rigidity of the legs of the animal can be adjusted according to the change of the movement speed and the step frequency during the movement process of the animal so as to achieve the optimal movement state. Therefore, in the design process of the robot, the rigidity variable mechanism is introduced into the robot structure, so that the motion efficiency of the robot can be improved by storing and releasing energy according to motion requirements, and the robot can adapt to a complex operation environment and resist external motion interference.

The variable-rigidity flexible joint is different according to the rigidity adjusting principle and can be divided into 5 types: the equivalent control realizes rigidity control, the antagonistic control realizes rigidity control, the elastomer structure is changed to control the joint rigidity, the spring pretension is utilized to realize rigidity control, and the output transmission ratio is changed to realize rigidity control.

Disclosure of Invention

The invention aims to provide a variable-rigidity flexible joint aiming at the defects of the existing robot joint technology, the joint is a flexible joint which realizes variable rigidity by changing the pretightening force of a spring, has compact structure and can be applied to a rotary joint of a robot.

The purpose of the invention is realized by the following technical scheme: a variable stiffness flexible joint comprising: the rigidity adjusting motor, the worm, the driving disc, the shaft and the driven disc; the rigidity adjusting motor is connected with a worm, the worm is connected with a worm wheel of a driving disc through a transmission pair, the driven disc is arranged on the output end face of the driving disc, and the center of the driving disc is rotationally connected with the center of the driven disc through a shaft; the driven disc comprises spring mounting seats, springs, sliding blocks and linear guide rails, wherein 3 groups of spring mounting seats are uniformly distributed on the driven disc along the circumferential direction, each group of spring mounting seats is provided with the linear guide rail, the sliding blocks are arranged on the linear guide rails, two sides of each sliding block are respectively fixedly connected with one end of each spring, and the other end of each spring is fixedly connected with the spring mounting seat; the output end face of the driving disc is provided with 3 groups of T-shaped grooves distributed along the circumferential direction of the driving disc, the upper end of the sliding block is provided with a roller, and the roller is connected with the T-shaped grooves in a sliding mode.

Further, the driving disc is of a worm-wheel-like structure.

Further, the contour line of the T-shaped groove is a curve with variable radius.

Further, the curve with variable radius is a sine curve, a cosine curve, a spiral line or a polynomial curve.

Compared with the prior art, the invention has the beneficial effects that: the variable-stiffness flexible joint provided by the invention is a flexible joint which realizes variable stiffness by changing the pretightening force of the spring, has a compact structure and quick response, can effectively relieve impact and vibration, has better impact resistance, adjusts the stiffness of the joint by adjusting the precompression amount of the spring through an independent stiffness adjusting motor, ensures that the position and the stiffness of the joint are relatively independent, has a simpler control method, and can continuously adjust the stiffness. In addition, the curve profile of the T-shaped groove at the output end of the driving disk can be flexibly designed into various forms such as a sine curve, a cosine curve, a spiral line, a polynomial curve and the like, and the rigidity adjusting device can be suitable for rigidity adjusting requirements of different application scenes.

Drawings

FIG. 1 is a schematic view of a variable stiffness flexible joint according to the present invention;

FIG. 2 is a schematic view of a driven plate of the variable stiffness flexible joint of the present invention;

FIG. 3 is a schematic view of the structure of the driving disk output end of the variable stiffness flexible joint according to the present invention;

FIG. 4 is a graph of stiffness curves for a variable stiffness flexible joint according to the present invention;

wherein: 1. worm, 2 driving disk, 3 shaft, 4 driven disk, 5 spring, 6 slide block and 7 linear guide rail.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be further described below with reference to the accompanying drawings. The described embodiments are only some of the embodiments of the present invention, and all other embodiments obtained by those skilled in the art based on the method of the present invention without any inventive work are within the scope of the present invention.

Fig. 1 is a schematic view of a variable stiffness flexible joint according to the present invention, which includes: the rigidity adjusting device comprises a rigidity adjusting motor, a worm 1, a driving disc 2, a shaft 3 and a driven disc 4; the rigidity adjusting motor is connected with the worm 1, the driving disc 2 is of a worm wheel-like disc structure, the cylindrical surface of the driving disc 2 is processed into a worm gear tooth surface matched with the worm 1, the worm 1 is connected with the worm wheel of the driving disc 2 through a transmission pair, the rigidity adjusting motor drives the worm 1 to rotate, and the driving disc 2 is driven to rotate through gear meshing of the worm wheel. The output end face of the driving disk 2 is provided with 3 groups of T-shaped grooves distributed along the circumferential direction of the output end face, as shown in fig. 3, the contour lines of the T-shaped grooves are curves with variable radiuses, and can be sine curves, cosine curves, spiral lines or polynomial curves. Theoretical derivation and simulation analysis show that a curve equation is a key parameter for determining whether the whole structure can achieve rigidity changing, for example, when a curve is a circular arc, the whole structure cannot achieve rigidity changing, and only when a T-shaped groove is a curve with a variable radius, rigidity changing of a joint can be achieved. The driven disc 4 is arranged on the output end of the driving disc 2, and the center of the driving disc 2 and the center of the driven disc 4 are rotationally connected through a shaft 3. Referring to fig. 2, the driven disc 4 of the present invention is a disc-shaped structural member, the driven disc 4 includes spring mounting seats, springs 5, sliders 6 and

linear guide rails

7, and 3 sets of spring mounting seats are uniformly distributed along the circumferential direction of the driven disc 4 for mounting the springs 5. Each group of spring mounting seats is provided with a linear guide rail 7, each linear guide rail 7 is provided with a sliding block 6, two sides of each sliding block are respectively and fixedly connected with one end of each spring 5, and the other end of each spring 5 is fixedly connected with the spring mounting seat; the upper end of the sliding block 6 is provided with a roller, and the roller is connected with the T-shaped groove in a sliding mode. Therefore, the movement of the slide block 6 is a compound movement, on one hand, when the rigidity adjusting motor drives the worm 1 to rotate, the driving disc 2 is driven by the worm 1 to rotate, and the roller can be driven to move along a curve in the T-shaped groove; on the other hand, the linear guide rail 7 arranged along the radial direction moves linearly in the radial direction of the driven disc 4, when the slide block 6 moves along the linear guide rail 7, the expansion and contraction amount of the spring 5 can be changed, so that the pretightening force of the spring 5 is changed, and the rigidity of the joint is changed, therefore, the spring 5 used in the invention can also be replaced by other elastic elements with certain rigidity. The rigidity adjustment of the joint is realized by adjusting the pretightening force of the spring 5, and the device has the advantages of simple and compact structure, small volume, large adjustment range, high precision and the like, and can be integrated into a rotary joint of the robot.

Fig. 4 shows a stiffness graph of the variable stiffness flexible joint according to the present invention, and it can be known from the definition of stiffness that the rotational stiffness of the joint is the derivative of the moment of rotation of the joint with respect to the rotational angle, where k is the system stiffness, and it can be known from fig. 4 that the joint stiffness k increases with the increase of the rotational angle θ.

The working process of the invention is as follows: the worm 1 is driven by a rigidity adjusting motor, the driving disc 2 is driven to rotate through the worm gear and worm transmission pair, the roller of the sliding block 6 is driven to slide in the T-shaped groove in the output end face of the driving disc 2, meanwhile, the sliding block 6 moves linearly along the linear guide rail 7, the stretching amount of the spring 5 installed between the sliding block 6 and the driven disc 4 is changed, and the pre-tightening force of the spring 5 is changed to achieve the purpose of adjusting the rigidity of the system. The rigidity of the joint is adjusted by adjusting the precompression amount of the spring 5 through an independent rigidity adjusting motor, so that the position and rigidity of the joint are adjusted relatively independently, the control method is simple, and the rigidity can be continuously adjusted.

The variable-rigidity flexible joint can be used for foot robots, industrial robots, cooperative robots and the like, and can adapt to different working scenes by adjusting the rigidity of the structure, for example, the variable-rigidity flexible joint can be applied to the foot robots to relieve impact, so that the robots have better motion characteristics; the application of the method to the cooperative robot can ensure that the cooperative robot has better action flexibility and avoids harm to a human body in the human-computer interaction process.

Claims

1. A variable stiffness flexible joint, comprising: the rigidity adjusting device comprises a rigidity adjusting motor, a worm (1), a driving disc (2), a shaft (3) and a driven disc (4); the rigidity adjusting motor is connected with a worm (1), the worm (1) is connected with a worm wheel of a driving disc (2) through a transmission pair, a driven disc (4) is arranged on the output end face of the driving disc (2), and the center of the driving disc (2) is rotationally connected with the center of the driven disc (4) through a shaft (3); the driven disc (4) comprises spring mounting seats, springs (5), sliding blocks (6) and linear guide rails (7), wherein 3 groups of spring mounting seats are uniformly distributed on the driven disc (4) along the circumferential direction, each group of spring mounting seats is provided with the linear guide rail (7), the sliding blocks (6) are arranged on the linear guide rails (7), two sides of each sliding block are fixedly connected with one end of each spring (5), and the other end of each spring (5) is fixedly connected with the spring mounting seat; the output end face of the driving disc (2) is provided with 3 groups of T-shaped grooves distributed along the circumferential direction of the driving disc, and the upper end of the sliding block (6) is provided with a roller which is connected with the T-shaped grooves in a sliding manner.

2. The variable stiffness flexible joint according to claim 1, wherein the drive disc (2) is of a worm-like disc type construction.

3. The variable stiffness flexible joint of claim 1, wherein the contour of the T-shaped slot is a variable radius curve.

4. The variable stiffness flexible joint of claim 3, wherein the variable radius curve is a sine curve, a cosine curve, a spiral curve, or a polynomial curve.