CN109623871B - Active-passive rigidity-variable joint and rigidity adjusting method thereof - Google Patents
Active-passive rigidity-variable joint and rigidity adjusting method thereof Download PDFInfo
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- CN109623871B CN109623871B CN201910154197.7A CN201910154197A CN109623871B CN 109623871 B CN109623871 B CN 109623871B CN 201910154197 A CN201910154197 A CN 201910154197A CN 109623871 B CN109623871 B CN 109623871B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J17/00—Joints
- B25J17/02—Wrist joints
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J19/00—Accessories fitted to manipulators, e.g. for monitoring, for viewing; Safety devices combined with or specially adapted for use in connection with manipulators
- B25J19/06—Safety devices
- B25J19/068—Actuating means with variable stiffness
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Abstract
The invention relates to a driving-driven variable stiffness joint and a stiffness adjusting method thereof, comprising a joint output rod, a joint driving rod, a central shaft, a stepping motor, a motor mounting seat, a helical gear large gear, a torsion spring, a helical gear pinion, a first group of steel balls, a first conical disk, a first disc spring, a first sliding block, a second disc spring, a second conical disk, a second group of steel balls, a left end cover, a first pressure spring, a right-handed nut, a left-handed nut, a sleeve, a second pressure spring, a first shaft sleeve and a second shaft sleeve. The joint rigidity is changed by adjusting the compression amount of the two disc springs, so that the active rigidity changing function of the joint is realized; when the joint rotates relatively, the torsion spring rotates, the sleeve is extruded and deformed, the first group of steel balls and the first conical disc as well as the second group of steel balls and the second conical disc are matched with each other, radial displacement is converted into axial displacement, the first disc spring and the second disc spring are compressed, the joint driving rod and the joint output rod are prevented from rotating relatively, and flexible output of the joint is realized.
Description
Technical Field
The invention relates to the technical field of robot joints, in particular to an active-passive variable stiffness joint and a stiffness adjusting method thereof.
Background
With the rapid development of technology, traditional rigid robot designs have reached a limit. At present, a service medical robot is emerging, in the field of man-machine interaction, safety constraint is an important aspect of interaction between the robot and human, and a traditional rigid robot is slow in motion and insufficient in power, so that practical application is difficult; in the fields of industrial production, flexible assembly and fixed load assembly, the flexibility is sensitive to interaction force, and the application of the high-precision torque sensor has the defects of high cost and high real-time requirement of a control system.
Application number 201710289744.3 discloses a compact type rigidity-variable rotary flexible joint, which comprises a joint driving disc, a joint output disc, a joint passive inner disc, a first cam, a first passive rigidity-variable adjusting seat, a first group of compression springs, an optical axis, a first rigidity-variable adjusting seat, a turbine screw rod structure, a second rigidity-variable adjusting seat, a second group of compression springs, a second passive rigidity-variable adjusting seat, a second cam, a cylindrical gear, a worm, an absolute encoder, a motor and an arc rack, wherein the mechanism has the function of actively-passively adjusting the rigidity of the joint, but is relatively complex in structure, the overall size of the designed joint is 160mm in diameter and 45mm in height, the maximum angle of flexible deformation is 45 degrees, the volume is large, the relative rotation angle is small, and the universality of the mechanism applied to various small and medium-sized robots is limited. The existing rigidity-variable joint is relatively complex in structure, large in size, complex in control and poor in rigidity-variable characteristic, and based on the reasons, the rigidity-variable joint which is simple in structure, small in size and good in active rigidity adjusting characteristic is designed, so that the rigidity-variable joint has important practical significance.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide the active-passive variable stiffness joint and the stiffness adjusting method thereof, and the joint can be used for a joint rotary robot and has the advantages of simple and small structure, rapid adjustment, energy saving and larger stiffness adjusting range.
The invention solves the technical problems by providing an active-passive variable stiffness joint which comprises a joint output rod, a joint driving rod, a central shaft, a stepping motor and a motor mounting seat, wherein two ends of the central shaft are respectively connected with the joint output rod and the joint driving rod, and the stepping motor is fixed on the joint output rod through the motor mounting seat; the joint is characterized by further comprising a helical gear, a torsion spring, a helical pinion, a first group of steel balls, a first conical disc, a first disc spring, a first sliding block, a second disc spring, a second conical disc, a second group of steel balls, a left end cover, a first pressure spring, a right-handed nut, a left-handed nut, a sleeve, a second pressure spring, a first shaft sleeve and a second shaft sleeve;
the first conical disc, the first sliding block, the first disc spring and the first pressure spring are respectively identical to the corresponding second conical disc, the corresponding second sliding block, the corresponding second disc spring and the corresponding second pressure spring in shape and structure;
the output end of the stepping motor is connected with a bevel pinion through a key, the bevel pinion is meshed with a bevel gear wheel, and the bevel gear wheel is matched with the central shaft and fixed with the joint output rod; a torsion spring is wound outside the sleeve, one end of the torsion spring is fixed with the joint output rod, and the other end of the torsion spring is fixed with the joint driving rod;
the middle part of the central shaft is a central shaft shoulder, shaft sections at two ends of the central shaft shoulder are lead screws, the rotation directions of the two lead screws are opposite, and the outer side of the lead screw is a first optical axis; the outer side of the first optical axis is a second optical axis, and a key slot is arranged on the second optical axis on one side; the outer side of the second optical axis is a third optical axis, the outer side of the third optical axis is a threaded shaft, and shaft shoulders are arranged between the first optical axis, the second optical axis, the third optical axis and the threaded shaft;
the left end cover, the second pressure spring, the second conical disc, the second disc spring, the left-handed nut, the right-handed nut, the first disc spring, the first conical disc, the first pressure spring and the helical gear are sequentially nested on the central shaft from the driving end to the output end, the left-handed nut and the right-handed nut are connected to corresponding lead screws of the central shaft through threads, and the second conical disc and the first conical disc are respectively fixed on a first optical axis of the central shaft; the helical gear is arranged on a second optical axis of the central shaft outside the first conical disc through a key slot, and the left end cover is positioned on the second optical axis of the central shaft outside the second conical disc; gaps are reserved between the first disc spring, the first pressure spring, the second disc spring and the second pressure spring and the central shaft; the left end cover is arranged on a second optical axis of the central shaft through interference fit, and is axially positioned through a second sleeve;
the first conical disc is a round table, a plurality of steel ball grooves are uniformly arranged on the side surface of the round table, the large-diameter end of the round table is close to the adjacent right-handed nut, the center of the round table is a through hole and sleeved on a first optical axis of the central shaft, and the small-diameter end of the round table is provided with a pressure spring groove;
the sleeve is sleeved on the first group of steel balls and the second group of steel balls, a plurality of evenly distributed sliding grooves are formed in the circumferences of the left end and the right end, and meanwhile, a through groove is formed in the circumferential side face of the sleeve; the first group of steel balls are positioned in the steel ball groove of the first conical disc, and the axial displacement of the first group of steel balls is limited by the flange extending out of the left end cover; the second group of steel balls are positioned in the steel ball groove of the second conical disc, and the axial displacement of the second group of steel balls is limited by the helical gear;
the first sliding block is sleeved on the right-handed nut to limit the rotation of the right-handed nut, a plurality of protrusions are uniformly arranged on the outer side surface of the first sliding block along the axial direction of the first sliding block, the protrusions are matched with the sliding grooves on the sleeve in shape, and the protrusions can slide left and right in the sliding grooves; the second sliding block is sleeved on the left-handed nut to limit the rotation of the left-handed nut.
The rigidity adjusting method of the active-passive rigidity-variable joint comprises the following steps: the stepping motor drives the central shaft to rotate through gear transmission, left and right nuts on the central shaft move axially towards two ends respectively, so that steel balls on the first conical disc and the second conical disc move in the steel ball grooves and then contact with the sleeve, torsion of the torsion spring is further hindered, the rigidity of the joint is changed by adjusting the compression amount of the two disc springs, and the active rigidity changing function of the joint is realized; when the joint rotates relatively, the torsion spring twists, the inner diameter of the torsion spring radially deforms, the sleeve is extruded and deformed, and then the first group of steel balls and the first conical disc as well as the second group of steel balls and the second conical disc are mutually matched, radial displacement is converted into axial displacement, the first disc spring and the second disc spring are compressed, the relative rotation of the joint driving rod and the joint output rod is hindered, flexible output of the joint is realized, and the passive rigidity changing function of the joint is realized.
Compared with the prior art, the invention has the following beneficial effects:
1. the joint skillfully utilizes the characteristic of diameter change in the torsion process of the torsion spring, and the change is blocked by the combining mechanism, so that the active-passive rigidity changing function of the joint is realized; the torsion spring is simple and compact in structure, is suitable for the torsion type joint robot, and has an energy storage function in the torsion process.
2. The rigidity-variable joint realizes the rotation of the joint through the torsion of the torsion spring, realizes the flexible output of driving moment, and ensures that the joint has higher safety in the man-machine interaction process.
3. In the joint, threads with opposite rotation directions are skillfully processed on two symmetrical shaft sections of the central shaft, the motor can drive the shaft to rotate through the gear set, two nuts with opposite rotation directions simultaneously compress the disc springs, the compression amount of the two disc springs is the same, the structure is simple and compact, and the active-passive rigidity changing function is skillfully realized.
4. The compression deformation of the disc spring is skillfully utilized in the joint to block the change of the pitch diameter of the torsion spring, so that the active-passive rigidity changing function is realized, and compared with a pressure spring, the spring has the advantages of large bearing capacity, small occupied space, compact structure and the like.
5. The invention adopts the forms of the screw nut and the reduction gear to amplify the axial force, has compact structure and reduces the power requirement of the motor.
6. The joint designed in the embodiment of the invention has the advantages of overall dimension of 42mm in diameter, 52mm in height, maximum angle of flexible deformation of 100 degrees, compact structure, small volume, strong applicability, large rigidity adjustment range and the like compared with the existing rigidity-variable joint.
Drawings
FIG. 1 is a schematic view of the overall structure of one embodiment of the active-passive stiffness-changing joint of the present invention;
FIG. 2 is a schematic view of the structure of a joint implementing stiffness adjustment portion of one embodiment of the active-passive stiffness-changing joint of the present invention;
FIG. 3 is a schematic view of the internal structure of a joint implementing stiffness adjustment portion of one embodiment of the active-passive variable stiffness joint of the present invention;
FIG. 4 is a schematic view of a flexible cross-sectional structure of the active-passive stiffness-changing joint along the direction A-A of FIG. 2;
FIG. 5 is a schematic perspective view of a sleeve 21 of one embodiment of an active-passive stiffness joint of the present invention;
fig. 6 is a schematic perspective view of a first slider 21 of an embodiment of the active-passive stiffness-variable joint of the present invention;
FIG. 7 is a schematic perspective view of a first cone 10 of one embodiment of the active-passive stiffness-changing joint of the present invention;
FIG. 8 is a schematic view of the structure of the central shaft 8 of an embodiment of the active-passive stiffness-changing joint of the present invention;
( In the figure 1, a stepping motor; 2. a motor mounting seat; 3. a joint output rod; 4. helical gear; 5. a torsion spring; 6. a joint driving rod; 7. a helical pinion; 8. a central shaft; 9. a first set of steel balls; 10. a first conical disc; 11. a first disc spring; 12. a first slider; 13. a second slider; 14. a second disc spring; 15. a second conical disk; 16. a second set of steel balls; 17. a left end cover; 18. a first compression spring; 19. a right-handed nut; 20. a left-handed nut; 21. a sleeve; 22. a second compression spring; 23 a first sleeve, 24 a second sleeve; 211. a chute 212, a through slot; 102. steel ball groove )
Detailed Description
Specific examples of the present invention are given below. The specific examples are only for further detailed description of the present invention and do not limit the scope of the present application.
The invention relates to a main-passive rigidity-variable joint, which comprises a stepping motor, a motor mounting seat, a joint output rod, a helical gear, a torsion spring, a joint driving rod, a helical gear pinion, a central shaft, a first group of steel balls, a first conical disc, a first disc spring, a first sliding block, a second disc spring, a second conical disc, a second group of steel balls, a left end cover, a first pressure spring, a right-hand nut, a left-hand nut, a sleeve, a second pressure spring, a first shaft sleeve and a second shaft sleeve, wherein the first disc spring is arranged on the first shaft sleeve;
the stepping motor is arranged on the joint output rod through a motor mounting seat, the output end of the stepping motor is connected with the helical pinion through a key, one end of the torsion spring is fixed with the joint output rod, and the other end of the torsion spring is fixed with the joint driving rod; the joint output rod is fixed with the helical gear, and the helical gear is matched with the central shaft;
the middle part of the central shaft is a central shaft shoulder 801, shaft sections at two ends of the central shaft shoulder are lead screws 802, and the outer sides of the two lead screws are a first optical axis 803; the outer side of the first optical axis is a second optical axis 804, and a key groove 805 is arranged on the second optical axis on one side; the outer side of the second optical axis is a third optical axis 806, the outer side of the third optical axis is a threaded shaft 807, and shaft shoulders are arranged between the first optical axis, the second optical axis, the third optical axis and the threaded shaft;
the left end cover 17, the second pressure spring 22, the second conical disk 15, the second disc spring 14, the left-handed nut 20, the right-handed nut 19, the first disc spring 11, the first conical disk 10, the first pressure spring 18 and the helical gear 4 are nested in sequence from the driving end to the output end on the central shaft 8, the left-handed nut 20 and the right-handed nut 19 are connected to a lead screw of the central shaft 8 through threads, and the second conical disk 15 and the first conical disk 10 are respectively fixed on a first optical axis of the central shaft 8; the helical gear is arranged on a second optical axis of the central shaft 8 outside the first conical disc through a key groove 805, and the left end cover 17 is positioned on the second optical axis of the central shaft outside the second conical disc; gaps exist among the first disc spring 11, the first pressure spring 18, the second disc spring 14 and the second pressure spring 22 and the central shaft 8; the left end cover 17 is mounted on a second optical axis 804 of the central shaft 8 through interference fit, and is axially positioned through a second shaft sleeve 24;
the first conical disc 10 and the second conical disc have the same structure and are both round tables, a plurality of steel ball grooves 102 are uniformly arranged on the side surfaces of the round tables, the large-diameter ends of the round tables are close to adjacent right-handed nuts 19 or left-handed nuts, the centers of the round tables are through holes, the round tables are sleeved on a first optical axis of a central shaft, and pressure spring grooves 101 are formed in the small-diameter ends of the round tables;
the sleeve 21 (see fig. 5) is sleeved on the first group of steel balls 9 and the second group of steel balls 16, a plurality of sliding grooves 211 are uniformly distributed on the circumferences of the left end and the right end, the sliding grooves on the left end and the right end are staggered, and meanwhile, a through groove 212 is formed on the circumferential side surface of the sleeve; the first group of steel balls 9 are positioned in the steel ball groove 102 of the first conical disc 10, and the axial displacement of the first group of steel balls is limited by a flange extending out of the left end cover 17; the second group of steel balls 16 are positioned in the steel ball groove 102 of the second conical disc 15, and the axial displacement of the second group of steel balls is limited by the helical gear wheel 4;
the first sliding block 12 is sleeved on the right-handed nut 19 to limit the rotation of the first sliding block, a plurality of protrusions 122 are uniformly arranged on the outer side surface of the sliding block along the axial direction of the sliding block, the shape of the protrusions is matched with that of a sliding groove on the sleeve, and the protrusions can slide left and right in the sliding groove; the second slider 13 is sleeved on the left-handed nut 20 to limit the rotation of the left-handed nut, and the second slider has the same shape and structure as the first slider.
The rigidity adjusting method realized by the active-passive rigidity-variable joint comprises the following steps: the stepping motor drives the central shaft to rotate through gear transmission, left and right nuts on the central shaft move axially towards two ends respectively, so that steel balls on the first conical disc and the second conical disc move in the steel ball grooves and then contact with the sleeve, torsion of the torsion spring is further hindered, the rigidity of the joint is changed by adjusting the compression amount of the two disc springs, and the active rigidity changing function of the joint is realized; when the joint rotates relatively, the torsion spring twists, the inner diameter of the torsion spring radially deforms, the sleeve is extruded and deformed, and then the first group of steel balls and the first conical disc as well as the second group of steel balls and the second conical disc are mutually matched, radial displacement is converted into axial displacement, the first disc spring and the second disc spring are compressed, the relative rotation of the joint driving rod and the joint output rod is hindered, flexible output of the joint is realized, and the passive rigidity changing function of the joint is realized.
Gaps of 0.3-0.6 mm exist between the first disc spring 11, the first pressure spring 18, the second disc spring 14 and the second pressure spring 22 and the central shaft 8.
The circular truncated cone circumferences of the first cone disc and the second cone disc are uniformly provided with 8, 10, 11, 12, 13, 14 or 15 steel ball grooves with different numbers, the first group of steel balls and the second group of steel balls are respectively arranged in the corresponding steel ball grooves, and when the active-passive rigidity change adjustment is carried out, the steel balls in the different steel ball grooves are applied to the inner wall of the sleeve to generate uniform distribution force so as to realize the rigidity change of the joint.
The same number of sliding grooves are distributed at two ends of the sleeve 21, but the sliding grooves with staggered positions are distributed at two ends of the sleeve, each end of the sleeve can be provided with 3, 4, 5, 6 and other sliding grooves with different numbers, the outer sides of the left end nut and the right end nut are distributed with the same number of protruding shapes as the sliding grooves on the adjacent sleeve ends, and when the active-passive rigidity change adjustment is carried out, the left end nut and the right end nut can axially move along different sliding ways through the protruding shapes to realize the rigidity change of the joint.
The use process or the working principle of the joint are as follows: the flexible joint can realize the functions of active variable stiffness and passive variable stiffness:
the stepping motor 1 is arranged on the joint output rod 3 through a motor mounting seat 2, the helical gear pinion 7 is connected with the output end of the motor 1 through a key, one end of the torsion spring 5 is clamped in a groove of the joint output rod 3 through a torsion arm, the joint output rod 3 is fixed with the helical gear wheel 4 through two groups of countersunk head screws, and the helical gear wheel 4 is matched with the central shaft 8 through a key; one end of the central shaft 8 is arranged on the joint driving rod 6 in a clearance fit manner, the central shaft is axially positioned through a hexagonal nut, the other end of the central shaft is connected with the joint output rod through a pin shaft, and the central shaft is axially positioned through the hexagonal nut; the central shaft 8 is provided with a central shaft shoulder in the middle part and is used for axially positioning the left-handed nut 20 and the right-handed nut 19; the shaft sections at the two ends of the central shaft shoulder are screw rods, the screw rods with one end being left-handed and the other end being right-handed drive left-handed nuts 20 and right-handed nuts 19 which are matched with the screw rods to move, so that the first group of steel balls 9 and the second group of steel balls 16 are in contact with the sleeve 21, and the active rigidity changing function of the joint is realized by changing the compression amount of the first disc spring 11 and the second disc spring 14;
when the joint driving rod 6 and the joint output rod 3 do not rotate relatively, the torsion spring 5 is not twisted, the inner diameter of the torsion spring is not changed, the first disc spring 11 and the second disc spring 15 are not compressed, and flexible deformation is not generated; when the joint driving rod 6 and the joint output rod 3 rotate relatively, the torsion spring 5 twists, the inner diameter of the torsion spring is radially deformed, the sleeve 21 is extruded and deformed, and then the first group of steel balls 9 and the first conical disc 10 and the second group of steel balls 16 and the second conical disc 15 are mutually matched with each other, radial displacement is converted into axial displacement, the first disc spring 11 and the second disc spring 14 are compressed, the relative rotation of the joint driving rod 6 and the joint output rod 3 is blocked, the flexible output of the joint is realized, and the passive rigidity changing function of the joint is realized.
Example 1
The embodiment provides a main-passive rigidity-variable joint, which comprises a stepping motor 1, a motor mounting seat 2, a joint output rod 3, a helical gear 4, a torsion spring 5, a joint driving rod 6, a helical gear pinion 7, a central shaft 8, a first group of steel balls 9, a first conical disc 10, a first disc spring 11, a first sliding block 12, a second sliding block 13, a second disc spring 14, a second conical disc 15, a second group of steel balls 16, a left end cover 17, a first pressure spring 18, a right-hand nut 19, a left-hand nut 20, a sleeve 21, a second pressure spring 22, a first shaft sleeve 23, a second shaft sleeve 24, a sliding groove 211 and a steel ball groove 102;
the stepping motor 1 is arranged on the joint output rod 3 through a motor mounting seat 2, and the output end of the stepping motor 1 is connected with an oblique tooth pinion 7 through a key; the torsion spring 5 is wound on the outer surface of the sleeve 21, one end of the torsion spring 5 is clamped in a groove of the joint output rod 3 through a torsion arm, and the other end of the torsion spring is clamped in a groove of the joint driving rod 6 through a torsion arm; the upper part of the joint output rod 3 is fixed with a helical gear wheel 4 through two groups of countersunk head screws, the helical gear wheel 4 is matched with a central shaft 8 through a key, and the helical gear wheel 4 is meshed with a helical gear pinion; one end of the central shaft 8 is arranged on the joint driving rod 6 through a second shaft sleeve 24 and is axially positioned through a hexagonal nut, and the other end of the central shaft is connected with the joint output rod 3 through a first shaft sleeve 23 and is axially positioned through the hexagonal nut;
the middle part of the central shaft 8 (see fig. 8) is a central shaft shoulder 801 for axial positioning of the left-hand nut 20 and the right-hand nut 19; the shaft sections at the two ends of the central shaft shoulder are screw rods 802, and the screw rods with one end being left-handed and the other end being right-handed drive left-handed nuts 20 and right-handed nuts 19 which are matched with the screw rods to move, so that the second group of steel balls 16 and the first group of steel balls 9 are in contact with the sleeve 21, and the active rigidity changing function of the joint is realized by changing the compression amount of the first disc spring 11 and the second disc spring 14; outside the two lead screws is a first optical axis 803 for fixing the first conical disk 10 and the second conical disk 15; the outer side of the first optical axis is a second optical axis 804, and a key groove 805 is arranged on the second optical axis on one side and is used for fixing the helical gear 4; the outer side of the second optical axis is a third optical axis 806, the outer side of the third optical axis is a threaded shaft 807, and shaft shoulders are arranged between the first optical axis, the second optical axis, the third optical axis and the threaded shaft;
the left end cover 17, the second pressure spring 22, the second conical disk 15, the second disc spring 14, the left-handed nut 20, the right-handed nut 19, the first disc spring 11, the first conical disk 10, the first pressure spring 18 and the helical gear 4 are nested in sequence from the driving end to the output end on the central shaft 8, the left-handed nut 20 and the right-handed nut 19 are connected to a lead screw of the central shaft 8 through threads, and the second conical disk 15 and the first conical disk 10 are respectively fixed on a first optical axis of the central shaft 8; the helical gear is arranged on a second optical axis of the central shaft 8 outside the first conical disc through a key groove 805, and the left end cover 17 is positioned on the second optical axis of the central shaft outside the second conical disc; the first disc spring 11 is positioned between the right-handed nut 19 and the first conical disc 10, and a gap of 0.3-0.5 mm is reserved between the first disc spring and the central shaft 8; the first pressure spring 18 is positioned between the first conical disc 10 and the helical gear wheel 4, and a gap of 0.3-0.5 mm is reserved between the first pressure spring and the central shaft 8;
the first conical disc 10 (see fig. 7) and the second conical disc have the same structure and are both round tables, a plurality of steel ball grooves 102 are uniformly arranged on the side surfaces of the round tables, the large diameter ends of the round tables are close to adjacent right-hand nuts 19 or left-hand nuts, the centers of the round tables are through holes and sleeved on a first optical axis of a central shaft, and the small diameter ends of the round tables are provided with pressure spring grooves 101; the first group of steel balls 9 and the second group of steel balls 16 are respectively arranged in the steel ball grooves of the first conical disc and the second conical disc;
one end of the first pressure spring 18 is positioned in a pressure spring groove of the first conical disc 10, and the other end of the first pressure spring is connected with the helical gear wheel 4 and is used for resetting the first conical disc 10;
the second disc spring 14 is positioned between the left-handed nut 20 and the second conical disc 15, and a gap of 0.3-0.5 mm is reserved between the second disc spring and the central shaft 8; the second pressure spring 22 is positioned between the second conical disc 15 and the left end cover 17, and a gap of 0.3-0.5 mm is reserved between the second pressure spring and the central shaft 8; one end of the second pressure spring 22 is positioned in the pressure spring groove of the second conical disc 15, and the other end of the second pressure spring is connected with the left end cover 17 and is used for resetting the second conical disc 15; the left end cover 17 is mounted on a second optical axis 804 of the central shaft 8 through interference fit, and is axially positioned through a second sleeve 24;
the sleeve 21 (see fig. 5) is sleeved on the first group of steel balls 9 and the second group of steel balls 16, the circumferences of the left end and the right end are provided with evenly distributed sliding grooves 211, the sliding grooves at the left end and the right end are staggered, meanwhile, the circumferential side surface of the sleeve is provided with through grooves 212, the sliding grooves are used for limiting the rotation of the first sliding block 12 and the second sliding block 13, and the through grooves are easy to deform in order to bear the inner diameter; the first group of steel balls 9 are positioned in the steel ball groove 102 of the first conical disc 10, and the axial displacement of the first group of steel balls is limited by a flange extending out of the left end cover 17; the second group of steel balls 16 are positioned in the steel ball groove 102 of the second conical disc 15, and the axial displacement of the second group of steel balls is limited by the helical gear wheel 4; the first slider 12 (see fig. 6) is sleeved on the right-handed nut 19 to limit the rotation of the first slider, a nut hole 121 matched with the right-handed nut is formed in the middle of the first slider, a plurality of protrusions 122 are uniformly formed on the outer side surface of the slider along the axial direction of the slider, the shape of each protrusion is matched with a sliding groove on the sleeve, and each protrusion can slide left and right in the sliding groove; the second slider 13 is sleeved on the left-handed nut 20 to limit the rotation of the left-handed nut, and the second slider has the same shape and structure as the first slider.
The overall size of the joint designed by the embodiment is 42mm in diameter and 52mm in height, the maximum angle of flexible deformation is 100 degrees, and the torque of the stepping motor is 0.8 N.m; the torsion spring 5 is a cylindrical torsion spring with the spring wire diameter of 3.5mm, the pitch diameter of 38.5mm and the number of turns of 11, the spring material is a carbon spring steel wire, the first compression spring 18 and the second compression spring 22 are cylindrical compression springs with the spring wire diameter of 1mm, the pitch diameter of 18mm and the number of turns of 4.5; the sleeve 21 is a cylindrical sleeve with the outer diameter of 35mm, the height of 46mm and the thickness of 2 mm; the first group of disc springs 11 and the second group of disc springs 12 are selected from B28 disc springs, and the material is 50CrVA; the first slide block 12 and the second slide block 13 are respectively sleeved with a right-handed nut 19 and a left-handed nut 20 of M14X1, and the number of steel ball grooves 102 on the first conical disk 10 and the second conical disk 15 is 10.
The joint of the invention is suitable for joint rotary robots.
The invention is applicable to the prior art where it is not described.
Claims (6)
1. The active-passive rigidity-variable joint comprises a joint output rod, a joint driving rod, a central shaft, a stepping motor and a motor mounting seat, wherein two ends of the central shaft are respectively connected with the joint output rod and the joint driving rod, and the stepping motor is fixed on the joint output rod through the motor mounting seat; the joint is characterized by further comprising a helical gear, a torsion spring, a helical pinion, a first group of steel balls, a first conical disc, a first disc spring, a first sliding block, a second disc spring, a second conical disc, a second group of steel balls, a left end cover, a first pressure spring, a right-handed nut, a left-handed nut, a sleeve, a second pressure spring, a first shaft sleeve and a second shaft sleeve;
the first conical disc, the first sliding block, the first disc spring and the first pressure spring are respectively identical to the corresponding second conical disc, the corresponding second sliding block, the corresponding second disc spring and the corresponding second pressure spring in shape and structure;
the output end of the stepping motor is connected with a bevel pinion through a key, the bevel pinion is meshed with a bevel gear wheel, and the bevel gear wheel is matched with the central shaft and fixed with the joint output rod; a torsion spring is wound outside the sleeve, one end of the torsion spring is fixed with the joint output rod, and the other end of the torsion spring is fixed with the joint driving rod;
the middle part of the central shaft is a central shaft shoulder, shaft sections at two ends of the central shaft shoulder are lead screws, the rotation directions of the two lead screws are opposite, and the outer side of the lead screw is a first optical axis; the outer side of the first optical axis is a second optical axis, and a key slot is arranged on the second optical axis on one side; the outer side of the second optical axis is a third optical axis, the outer side of the third optical axis is a threaded shaft, and shaft shoulders are arranged between the first optical axis, the second optical axis, the third optical axis and the threaded shaft;
the left end cover, the second pressure spring, the second conical disc, the second disc spring, the left-handed nut, the right-handed nut, the first disc spring, the first conical disc, the first pressure spring and the helical gear are sequentially nested on the central shaft from the driving end to the output end, the left-handed nut and the right-handed nut are connected to corresponding lead screws of the central shaft through threads, and the second conical disc and the first conical disc are respectively fixed on a first optical axis of the central shaft; the helical gear is arranged on a second optical axis of the central shaft outside the first conical disc through a key slot, and the left end cover is positioned on the second optical axis of the central shaft outside the second conical disc; gaps are reserved between the first disc spring, the first pressure spring, the second disc spring and the second pressure spring and the central shaft; the left end cover is arranged on a second optical axis of the central shaft through interference fit, and is axially positioned through a second sleeve;
the first conical disc is a round table, a plurality of steel ball grooves are uniformly arranged on the side surface of the round table, the large-diameter end of the round table is close to the adjacent right-handed nut, the center of the round table is a through hole and sleeved on a first optical axis of the central shaft, and the small-diameter end of the round table is provided with a pressure spring groove;
the sleeve is sleeved on the first group of steel balls and the second group of steel balls, a plurality of evenly distributed sliding grooves are formed in the circumferences of the left end and the right end, and meanwhile, a through groove is formed in the circumferential side face of the sleeve; the first group of steel balls are positioned in the steel ball groove of the first conical disc, and the axial displacement of the first group of steel balls is limited by the flange extending out of the left end cover; the second group of steel balls are positioned in the steel ball groove of the second conical disc, and the axial displacement of the second group of steel balls is limited by the helical gear;
the first sliding block is sleeved on the right-handed nut to limit the rotation of the right-handed nut, a plurality of protrusions are uniformly arranged on the outer side surface of the first sliding block along the axial direction of the first sliding block, the protrusions are matched with the sliding grooves on the sleeve in shape, and the protrusions can slide left and right in the sliding grooves; the second sliding block is sleeved on the left-handed nut to limit the rotation of the left-handed nut.
2. The active-passive variable stiffness joint of claim 1, wherein a gap of 0.3-0.6 mm exists between the first disc spring, the first pressure spring, the second disc spring and the second pressure spring and the central shaft.
3. A method of stiffness adjustment of an active-passive variable stiffness joint according to claim 1 or 2, the method comprising: the stepping motor drives the central shaft to rotate through gear transmission, left and right nuts on the central shaft move axially towards two ends respectively, so that steel balls on the first conical disc and the second conical disc move in the steel ball grooves to be in contact with the sleeve, torsion of the torsion spring is hindered, the rigidity of the joint is changed by adjusting the compression amount of the two disc springs, and the active rigidity changing function of the joint is realized; when the joint rotates relatively, the torsion spring twists, the inner diameter of the torsion spring radially deforms, the sleeve is extruded and deformed, and then the first group of steel balls and the first conical disc as well as the second group of steel balls and the second conical disc are mutually matched, radial displacement is converted into axial displacement, the first disc spring and the second disc spring are compressed, the relative rotation of the joint driving rod and the joint output rod is hindered, flexible output of the joint is realized, and the passive rigidity changing function of the joint is realized.
4. The active-passive variable stiffness joint of claim 1, wherein 8, 10, 11, 12, 13, 14 or 15 steel ball grooves are uniformly distributed on the circumference of the truncated cone of the first cone disc and the circumference of the truncated cone of the second cone disc.
5. The active-passive variable stiffness joint of claim 1, wherein the same number of sliding grooves are distributed at two ends of the sleeve, but the sliding grooves are staggered, and the number of the sliding grooves at each end is 3, 4, 5 or 6.
6. The active-passive stiffness joint of claim 1, wherein the joint is capable of being used in an articulated rotary robot.
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| CN110744584A (en) * | 2019-11-29 | 2020-02-04 | 河北工业大学 | Flexible active-passive variable stiffness joint |
| CN113146605B (en) * | 2021-05-06 | 2022-08-26 | 吉林大学 | Compact artificial muscle module with mechanical flexibility |
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