Variable stiffness robot joint based on magneto-rheological technology

Abstract

The invention discloses a variable-stiffness robot joint based on a magneto-rheological technology, and belongs to the technical field of variable-stiffness quadruped robots. The variable-stiffness robot joint comprises a flange, a coil baffle, an aluminum disc, a transmission shaft and an elastic unit. The aluminum disc is fixed to the outer side of the thigh of the quadruped robot, the flange is arranged at the other end of the aluminum disc, the flange is fixedly connected with the coil baffle, and the elastic unit is arranged between the aluminum disc and the flange; the transmission shaft is connected with the shank of the quadruped robot through a first common flat key. By the adoption of the structure, the magnetorheological fluid and the variable stiffness unit are subjected to integrated innovative design, and gravitational potential energy generated in the process that the quadruped robot jumps up and falls to the ground can be stored in the elastic unit and released when needed; the effect of buffering and vibration reduction can be achieved while it is guaranteed that the quadruped robot achieves outbreak jumping under the assistance of the variable-rigidity joints.

Description

Technical Field

[0001] The invention relates to the technical field of variable-rigidity quadruped robots, in particular to a variable-rigidity robot joint based on magnetorheological technology. Background Art

[0002] The variable stiffness joint based on magnetorheological technology is a new type of quadruped robot drive joint. The special joint drive mode of the legged robot has higher mobility and flexibility. In recent years, there have been more and more legged robots with multiple movement modes such as walking, trotting, jumping, climbing, etc. The energy and power required by these robots in different movement modes of different movement cycles will vary greatly, which places extremely high requirements on the design of joint drivers.

[0003] Currently, electric drive combined with elastic drive joints has made significant progress, but in most elastic actuators, mechanical locking mechanisms or brakes are relied on to achieve controllable stored energy. Due to the low flexibility and high complexity of the mechanical structure, the energy utilization efficiency of the elastic unit is low, so the requirements for the variable stiffness performance and energy utilization of the drive joint are becoming higher and higher. When the drive joint is required to be able to achieve jump enhancement while also playing a role in cushioning the robot's landing, a new structure is needed to achieve this performance requirement. Summary of the invention

[0004] The purpose of the present invention is to provide a variable stiffness robot joint based on magnetorheological technology, which integrates magnetorheological fluid and variable stiffness unit into an innovative design. When the coil is energized, the gravitational potential energy of the quadruped robot during the jump and landing process can be stored in the elastic unit and released when needed, ensuring that the quadruped robot can achieve explosive jumps with the assistance of the variable stiffness joint while also achieving the effect of buffering and shock absorption.

[0005] To achieve the above object, the present invention provides a variable stiffness robot joint based on magnetorheological technology, comprising a quadruped robot thigh, a quadruped robot shank, and a variable stiffness robot joint arranged between the quadruped robot thigh and the quadruped robot shank, wherein the variable stiffness robot joint comprises a flange, a coil baffle, an aluminum plate, a transmission shaft, and an elastic unit; The aluminum plate is fixed to the outer side of the thigh of the quadruped robot by a first bolt group, the other end of the aluminum plate is provided with the flange, the flange and the coil baffle are fixedly connected by a second bolt group, and the elastic unit is provided between the aluminum plate and the flange; the elastic unit and the flange are fixedly connected by a second set screw group and a fourth common flat key; The transmission shaft is arranged between the thigh of the quadruped robot and the calf of the quadruped robot, and is connected to the calf of the quadruped robot through a first common flat key. The elastic unit and the transmission shaft are connected to the second common flat key through a third fastening bolt group.

[0006] Preferably, the elastic unit includes a sleeve, a magnetorheological bearing, a torsion spring, an excitation coil and a retaining spring. The sleeve is fixedly connected to the right side of the transmission shaft through a second common flat key and a third fixing bolt group, and is located between the aluminum disk and the coil baffle. The magnetorheological bearing is installed on the side of the sleeve close to the aluminum disk, and the magnetorheological bearing is positioned by the sleeve, the third common flat key, the fourth common flat key and the retaining spring; the torsion spring is installed on the flange of the flange, and the front and rear ends of the torsion spring are positioned by the flange flange and the blocks on the aluminum disk respectively; the excitation coil is installed on the side of the sleeve close to the coil baffle.

[0007] Preferably, the coil baffle is provided with four through holes, the flange flange is provided with four threaded holes, the four through holes correspond to the four threaded holes one by one, and the second bolt group passes through the through holes and is screwed and connected with the threaded holes.

[0008] Preferably, the coil baffle is provided with a wire outlet hole for realizing power on and off of the excitation coil.

[0009] Preferably, the flange of the flange flange has three evenly distributed threaded holes for achieving axial positioning of the magnetorheological bearing.

[0010] Preferably, the shaft sleeve is provided with three threaded holes evenly distributed along the circumferential direction for realizing axial connection with the transmission shaft.

[0011] Preferably, the aluminum plate has six through holes evenly distributed in the circumferential direction around the transmission shaft, and the thigh of the quadruped robot has six threaded holes evenly distributed, the six through holes correspond to the six threaded holes one by one, and the first bolt group passes through the through holes and is screwed tightly to the threaded holes.

[0012] Preferably, the magnetorheological bearing includes a magnetorheological fluid and a deep groove ball bearing. The magnetorheological fluid is injected into the deep groove ball bearing. Under the action of an external magnetic field, the magnetorheological fluid forms a magnetic flux distributed along the direction of the magnetic flux lines of the external magnetic field. The magnetic flux is located at the ball, inner raceway and outer raceway of the deep groove ball bearing.

[0013] Preferably, the magnetic flux forms an obstacle to the relative rotation between the inner raceway and the outer raceway, thereby changing the damping of the magnetorheological bearing, and the strength of the magnetic flux is positively correlated with the strength of the magnetic field.

[0014] Preferably, when the excitation coil is energized, a closed magnetic circuit of the magnetorheological bearing, the bushing, the transmission shaft, the coil baffle and the flange is formed.

[0015] Therefore, the present invention adopts the above-mentioned variable stiffness robot joint based on magnetorheological technology, which has the following beneficial effects: 1. The present invention converts the compression angle between the legs of the quadruped robot into energy stored in the torsion spring through the torque transmission route of the quadruped robot legs, transmission shafts, bushings, magnetorheological bearings, flanges, and torsion springs, so that the quadruped robot can achieve explosive jumps with the assistance of variable stiffness joints while also achieving the effect of buffering and vibration reduction. When the height of the high-altitude jump is small, the variable stiffness joint can store energy in the torsion spring to achieve the variable stiffness characteristic; when the jump height is large, in addition to the energy storage of the torsion spring part, it can also protect the knee joint of the quadruped robot under large impact.

[0016] 2. Based on the variable damping characteristics of magnetorheological fluid, the present invention innovatively injects magnetorheological fluid into deep groove ball bearings to produce magnetorheological bearings. When a magnetic field is applied to the outside of the magnetorheological bearing, the ferromagnetic particles inside the bearing will form magnetic chains along the direction of the magnetic flux lines at the contact point between the bearing balls and the inner and outer ring raceways, hindering the relative rotation of the inner and outer rings of the bearing, thereby changing the damping of the bearing. The greater the intensity of the external magnetic field, the greater the intensity of the magnetic chain formed, and the corresponding bearing damping will also be greater.

[0017] 3. In the present invention, blocks are provided on the flange of the flange and the aluminum disk. The torsion spring is installed on the flange of the flange, and the two ends are positioned by the blocks on the flange flange and the aluminum disk respectively. In the process of transmitting torque, it is also the relative rotation of the flange flange and the aluminum disk that enables the torsion spring to store energy.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a variable stiffness robot joint based on magnetorheological technology of the present invention; Figure 2 This is a connection diagram of a variable stiffness robot joint based on magnetorheological technology according to the present invention; Reference numerals: 1. The thigh of the quadruped robot; 2. The gasket; 3. The first common flat key; 4. The first set screw; 5. The transmission shaft; 6. The calf of the quadruped robot; 7. The retaining spring; 8. The second set screw group; 9. The flange; 10. The coil baffle; 11. The third set bolt group; 12. The second common flat key; 13. The bushing; 14. The block; 15. The first bolt group; 16. The third common flat key; 17. The fourth common flat key; 18. The aluminum plate; 19. The second bolt group; 20. The excitation coil; 21. The magnetorheological bearing; 22. The torsion spring. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0021] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0022] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention more clear, the following will be combined with the accompanying drawings in the embodiments of the present invention. Figure 1 to Figure 2 The technical solution of the present invention is described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In the description of the present invention, it should be understood that the terms "center", "surroundings", "lateral", "longitudinal", "length", "thickness", "angle", "up", "down", "left", "right", etc., indicating directions or positions, are limited to simplifying the description of the present invention rather than specific positions or directions. The above terms are not limitations of the present invention.

[0024] The specific connection methods of each part of the present invention adopt conventional means such as mature bolts, rivets, welding, etc. in the prior art. The machinery, parts and equipment all adopt conventional models in the prior art, and the circuit connection adopts the conventional connection method in the prior art, which will not be described in detail here.

[0025] like Figure 1-2As shown, the present invention provides a variable stiffness robot joint based on magnetorheological technology, including a flange, a coil baffle, an aluminum plate, and an elastic unit. The coil baffle 10 and the flange flange 9 are fixedly connected on one side of the elastic unit by the second bolt group 19; the aluminum plate 18 is located on the other side of the elastic unit and is fixed to the outside of the quadruped robot thigh 1 by the first bolt group 15, and a stopper 14 is provided on the aluminum plate 18 and the flange flange 9; the elastic unit and the flange flange 9 are fixedly connected by the second set screw group 8 and the fourth common flat key 17; the elastic unit and the transmission shaft 5 between the quadruped robot thigh 1 and the quadruped robot shank 6 are fixedly connected by the third set bolt group 11 and the second common flat key 12; the elastic unit is positioned between the aluminum plate 18 and the flange flange 9 by the stopper 14. The top of the transmission shaft 5 is provided with a first set screw 4. The connection between the quadruped robot thigh 1 and the four groups of robot shanks 6 and the transmission shaft 5 is provided with a gasket 2.

[0026] The elastic unit includes a sleeve 13, a magnetorheological bearing 21, a torsion spring 22, an excitation coil 20 and a retaining spring 7. An aluminum disk 18 is connected to the thigh 1 of the quadruped robot through a first bolt group 15, a stopper 14 is arranged on the aluminum disk 18, and one end of the torsion spring 22 is limited by the stopper 14; a transmission shaft 5 is connected to the calf 6 of the quadruped robot through a first common flat key 3, the sleeve 13 is located between the aluminum disk 18 and the coil baffle 10, and is fixedly connected to the transmission shaft 5 through a second common flat key 12 and a third fastening bolt group 11; keyways are provided on the inner and outer sides of the magnetorheological bearing 21, the outer side of the sleeve 13 is fixedly connected to the inner ring of the magnetorheological bearing 21 through a third common flat key 16, the outer ring of the magnetorheological bearing 21 is fixedly connected to the flange flange 9 through a fourth common flat key 17, and the other end of the torsion spring 22 is limited by the stopper 14 on the flange flange 9.

[0027] The coil baffle 10 is provided with four through holes, and the flange 9 is provided with four threaded holes. The four through holes correspond to the four threaded holes one by one, and the second bolt group 19 passes through the through holes and is screwed and connected with the threaded holes.

[0028] The coil baffle 10 is provided with a wire outlet hole for realizing power on and off of the excitation coil 20 .

[0029] There are three evenly distributed threaded holes on the flange of the flange 9 for realizing the axial positioning of the magnetorheological bearing 21 .

[0030] The shaft sleeve 13 is evenly distributed along the circumferential direction with three threaded holes for axial connection with the transmission shaft 5 on the upper and lower legs.

[0031] The aluminum plate 18 has six through holes evenly distributed along the circumferential direction around the transmission shaft 5, and the quadruped robot thigh 1 has six threaded holes evenly distributed, the six through holes correspond to the six threaded holes one by one, and the first bolt group 15 passes through the through holes and is screwed and connected to the threaded holes.

[0032] When the excitation coil 20 is not energized, the magnetorheological fluid inside the magnetorheological bearing 21 in the elastic unit is in a liquid state that acts as a lubricant. The quadruped robot is a robot dog. When it lands after jumping, the angle between the thigh 1 of the quadruped robot and the shank 6 of the quadruped robot will be compressed. The angle compression between the thigh 1 of the quadruped robot and the shank 6 of the quadruped robot will transmit the torque to the inner and outer rings of the magnetorheological bearing 21 through the transmission structure: the transmission shaft 5, the sleeve 13, the magnetorheological bearing 21, the flange 9, and the torsion spring 22. At this time, since the magnetorheological fluid inside the magnetorheological bearing 21 is in a liquid state, the inner and outer rings of the magnetorheological bearing 21 will rotate relatively, so the above-mentioned joint will not affect the jumping of the quadruped robot.

[0033] However, when the excitation coil 20 is energized, since the excitation coil 20 is assembled on the shaft sleeve 13, one side of the excitation coil 20 is a coil baffle 10 made of 45 steel, which is connected to the flange 9 through the second bolt group 19, and the other end is the magnetorheological bearing 21. At this time, a closed magnetic circuit along the flange 9, the coil baffle 10, the shaft sleeve 13, the transmission shaft 5, the magnetorheological bearing 21, and the flange 9 will be formed near the excitation coil 20. At this time, the ferromagnetic particles inside the magnetorheological bearing 21 will form a magnetic flux chain along the direction of the magnetic flux line at the contact point between the balls inside the magnetorheological bearing 21 and the inner and outer ring raceways, which will hinder the relative rotation of the inner and outer rings of the magnetorheological bearing 21, thereby changing the damping of the bearing. The greater the strength of the external magnetic field, the greater the strength of the magnetic flux formed, and the greater the damping of the corresponding bearing. When the quadruped robot jumps and lands, the angle change between the quadruped robot thigh 1 and the quadruped robot shank 6 also transmits the torque to the inner and outer rings of the magnetorheological bearing 21 through the above-mentioned transmission structure. At this time, due to the magnetorheological fluid inside the magnetorheological bearing 21, a high-strength magnetic flux is formed along the direction of the magnetic flux line under the action of the magnetic field, and the inner and outer rings of the magnetorheological bearing 21 will not rotate relative to each other. The magnetorheological bearing 21 can be approximately regarded as a rigid body. The two ends of the corresponding torsion spring 22 will be compressed under the action of the block 14, and a part of the gravitational potential energy will be stored in the torsion spring 22. When the quadruped robot jumps again, the energy stored in the torsion spring 22 will act on the quadruped robot thigh 1 and the quadruped robot shank 6 in the opposite direction of the torque transmission route, so that the jumping height of the quadruped robot will be correspondingly increased. When the quadruped robot repeats the above debugging process repeatedly, the jumping height of the robot will become higher and higher.

[0034] In summary, the present invention adopts the above-mentioned variable stiffness robot joint based on magnetorheological technology, and integrates magnetorheological fluid and variable stiffness unit for innovative design. When the coil is energized, the gravitational potential energy of the quadruped robot during the jump and landing process can be stored in the elastic unit and released when needed, ensuring that the quadruped robot can achieve explosive jumps with the assistance of the variable stiffness joint while also achieving the effect of buffering and shock absorption.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A variable stiffness robot joint based on magnetorheological technology, comprising a quadruped robot thigh, a quadruped robot shank, and a variable stiffness robot joint arranged between the quadruped robot thigh and the quadruped robot shank, characterized in that: The variable stiffness robot joint comprises a flange, a coil baffle, an aluminum plate, a transmission shaft and an elastic unit; The aluminum plate is fixed to the outer side of the thigh of the quadruped robot by a first bolt group, the other end of the aluminum plate is provided with the flange, the flange and the coil baffle are fixedly connected by a second bolt group, and the elastic unit is provided between the aluminum plate and the flange; the elastic unit and the flange are fixedly connected by a second set screw group and a fourth common flat key; The transmission shaft is arranged between the thigh of the quadruped robot and the calf of the quadruped robot, and is connected to the calf of the quadruped robot through a first common flat key. The elastic unit and the transmission shaft are connected to the second common flat key through a third fastening bolt group.

2. The variable stiffness robot joint based on magnetorheological technology according to claim 1 is characterized in that: The elastic unit includes a sleeve, a magnetorheological bearing, a torsion spring, an excitation coil and a retaining spring. The sleeve is fixedly connected to the right side of the transmission shaft through a second common flat key and a third fixing bolt group, and is located between the aluminum disk and the coil baffle. The magnetorheological bearing is installed on the side of the sleeve close to the aluminum disk, and the magnetorheological bearing is positioned by the sleeve, the third common flat key, the fourth common flat key and the retaining spring; the torsion spring is installed on the flange of the flange, and the front and rear ends of the torsion spring are positioned by the flange flange and the blocks on the aluminum disk respectively; the excitation coil is installed on the side of the sleeve close to the coil baffle.

3. The variable stiffness robot joint based on magnetorheological technology according to claim 1 is characterized in that: The coil baffle is provided with four through holes, the flange is provided with four threaded holes, the four through holes correspond to the four threaded holes one by one, and the second bolt group passes through the through holes and is screwed and connected with the threaded holes.

4. The variable stiffness robot joint based on magnetorheological technology according to claim 1 is characterized in that: The coil baffle is provided with a wire outlet hole for realizing power on and off of the excitation coil.

5. The variable stiffness robot joint based on magnetorheological technology according to claim 1 is characterized in that: The flange of the flange is provided with three evenly distributed threaded holes for realizing the axial positioning of the magnetorheological bearing.

6. The variable stiffness robot joint based on magnetorheological technology according to claim 2, characterized in that: The shaft sleeve is evenly distributed along the circumferential direction with three threaded holes for realizing axial connection with the transmission shaft.

7. The variable stiffness robot joint based on magnetorheological technology according to claim 1 is characterized in that: The aluminum plate has six through holes evenly distributed in the circumferential direction around the transmission shaft, and the thigh of the quadruped robot has six threaded holes evenly distributed. The six through holes correspond to the six threaded holes one by one, and the first bolt group passes through the through holes and is screwed and connected to the threaded holes.

8. The variable stiffness robot joint based on magnetorheological technology according to claim 1 is characterized in that: The magnetorheological bearing includes a magnetorheological fluid and a deep groove ball bearing. The magnetorheological fluid is injected into the deep groove ball bearing. Under the action of an external magnetic field, the magnetorheological fluid forms a magnetic flux distributed along the direction of the magnetic flux lines of the external magnetic field. The magnetic flux is located at the balls, inner raceways and outer raceways of the deep groove ball bearing.

9. The variable stiffness robot joint based on magnetorheological technology according to claim 8, characterized in that: The magnetic flux hinders the relative rotation between the inner raceway and the outer raceway, thereby changing the damping of the magnetorheological bearing. The strength of the magnetic flux is positively correlated with the strength of the magnetic field.

10. The variable stiffness robot joint based on magnetorheological technology according to claim 2, characterized in that: After the excitation coil is energized, a closed magnetic circuit of the magnetorheological bearing, the shaft sleeve, the transmission shaft, the coil baffle and the flange is formed.

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