An anthropomorphic robot and its knee joint with variable stiffness and variable deceleration ratio function

Abstract

The application discloses a humanoid robot and a knee joint with variable stiffness and variable deceleration ratio function of the humanoid robot, which comprises a thigh, a push rod, first connecting rods, a second connecting rod, first guide rods, second guide rods, a variable stiffness mechanism and a shank, the upper end of the thigh is rotationally connected to the upper end of the push rod, the lower part of the thigh is rotationally connected to one end of the two first connecting rods, and the lower end of the thigh is rotationally connected to the upper end of the shank; the lower end of the push rod is rotationally connected to the other end of the two first connecting rods and the first end of the second connecting rod from inside to outside in a coaxial manner, the other end of the second connecting rod is rotationally connected to the shaft on the middle part outside of the first guide rod and the second guide rod; the upper ends of the first guide rod and the second guide rod which are mirror images are rotationally connected to the inner sides of the shaft of the upper end of the shank respectively; the first guide rod and the second guide rod are further respectively provided with sliding grooves, and the variable stiffness mechanism is provided with a fulcrum which slides in the sliding grooves; and the variable stiffness mechanism is further connected with a leaf spring in the shank. The knee joint integrates high burst, buffering and energy storage, and is helpful for long-time high dynamic movement of the humanoid robot.

Description

Technical Field

[0001] The invention belongs to the technical field of humanoid robots, and in particular relates to a humanoid robot knee joint with variable stiffness and variable reduction ratio functions. Background Art

[0002] Humanoid robots, by mimicking human form and movement, can perform various tasks in place of humans without changing the environment. They have become a hot area of ​​robotics research in recent years. The knee joint's cushioning capacity, high explosive force, and energy storage properties are crucial for sustained, highly dynamic movements. Current knee joints struggle to meet these requirements, so designing new knee joints with these capabilities is key to improving humanoid robots' ability to perform high-dynamic tasks such as running and jumping.

[0003] The knee joints of humanoid robots require high speed and torque output capabilities during high-dynamic operation, which requires higher-power drive motors. However, high-power drive motors increase the robot's mass and moment of inertia, which will reduce the robot's rapid response capabilities. Furthermore, due to the robot's size limitations, high-power motors cannot be installed in the robot's joints. Because the areas of the robot requiring rapid movement and the areas requiring high-torque movement are inconsistent, the robot's high-dynamic movement capabilities can be improved by using a variable reduction ratio. However, existing variable reduction ratio joints have one or more drawbacks, including complex structures, low load-bearing torque, poor variable reduction ratio curves, and low reliability. Furthermore, once assembled, when the required high-dynamic task changes, it is difficult to simply modify some of the simpler parts to change the reduction ratio to adapt to the new high-dynamic task.

[0004] During the high-dynamic motion of humanoid robots, joint flexibility not only mitigates impact forces and protects the robot, but also reduces joint power output, increasing the robot's operating time. Variable-stiffness joints, on the other hand, can adapt to different motion conditions and increase energy storage and cushioning effectiveness. Existing variable-stiffness joints suffer from low output torque and complex structures, making them difficult to meet the high-dynamic motion requirements of humanoid robots. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a humanoid robot knee joint with variable stiffness and variable reduction ratio functions.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A knee joint of a humanoid robot with variable stiffness and variable reduction ratio functions comprises a thigh, a push rod, a first connecting rod, a second connecting rod, a first guide rod, a second guide rod, a variable stiffness mechanism and a calf, wherein the first guide rod and the second guide rod are mirror images of each other;

[0008] The upper end of the thigh is rotatably connected to the upper end of the push rod, the lower end of the thigh is rotatably connected to one end of the two first connecting rods, and the lower end of the thigh is rotatably connected to the upper end of the calf;

[0009] The lower end of the push rod is coaxially connected to the other ends of the two first connecting rods and one end of the second connecting rod in sequence from the inside to the outside, and the other end of the second connecting rod is connected to the shaft in the middle of the outer sides of the first guide rod and the second guide rod;

[0010] The upper ends of the first guide rod and the second guide rod are respectively rotatably connected to the inner side of the shaft at the upper end of the calf; the first guide rod and the second guide rod are also respectively provided with a sliding groove, and the variable stiffness mechanism is provided with a fulcrum sliding in the sliding groove; the variable stiffness mechanism is also connected to the leaf spring of the calf.

[0011] In the above technical solution, the thigh includes a thigh structure, a first thigh shaft, a second thigh shaft, a driver A and a joint bearing; the first thigh shaft and the second thigh shaft are respectively fixed in the holes at the upper end and the lower part of the thigh structure, for connecting the upper end of the push rod and one end of the first connecting rod; the driver A is fixed on the thigh structure; joint bearings are respectively fixed in the cylindrical holes at the lower end of the thigh structure for connecting the calf; the thigh also includes a joint encoder, and the joint encoder includes a magnetic ring and a reader, the reader is fixed in the cylindrical hole at the lower end of the thigh structure, and the magnetic ring is fixed on the calf.

[0012] In the above technical solution, the push rod includes a push rod first housing, a driver B, a push rod motor, a push rod second housing, a push rod encoder, a push rod ball screw, a push rod ball screw nut, a push rod third housing and a push rod output connector;

[0013] The first push rod housing is rotatably connected to the first thigh shaft via the first push rod bearing;

[0014] The driver B is mounted on the first housing of the push rod;

[0015] The push rod third housing is fixed to the lower end of the push rod second housing, and the push rod second housing is connected to the push rod first housing via the push rod second bearing;

[0016] The push rod motor includes a stator and a rotor, the stator is located inside the first push rod housing, the rotor is located inside the stator, and the rotor is fixed on the second push rod housing;

[0017] A push rod ball screw nut is fixed inside the push rod third housing, the push rod ball screw nut is sleeved on the push rod ball screw, and a push rod output connector is fixed at the end of the push rod ball screw;

[0018] The push rod encoder comprises a magnetic ring and a reader, wherein the magnetic ring is fixed on the second shell of the push rod, and the reader is fixed on the first shell of the push rod.

[0019] In the above technical solution, the first connecting rod is in a straight line shape and consists of a first connecting rod structural member and a first connecting rod bearing; circular holes are provided at both ends of the first connecting rod structural member, and the first connecting rod bearing is fixed inside the circular holes, which are respectively connected to the second rotating shaft and the second connecting rod of the thigh.

[0020] In the above technical solution, the second connecting rod is H-shaped and consists of a second connecting rod input shaft, a second connecting rod structural member and a second connecting rod bearing; circular holes are provided at both ends of the second connecting rod structural member, and the second connecting rod bearing is fixed inside the circular holes. The second connecting rod bearing near one end of the push rod output connecting member is provided with a second connecting rod input shaft, and the second connecting rod input shaft is sequentially sleeved on the push rod output connecting member, the first connecting rod structural member and the second connecting rod structural member from the inside to the outside.

[0021] In the above technical solution, the first guide rod and the second guide rod are both composed of a guide rod structure, a guide rod bearing and a guide rod input shaft. The guide rod structure is provided with a first circular hole, a second circular hole and a slide groove. The first circular hole is located at the upper end of the guide rod structure, the second circular hole is located in the middle of one side of the guide rod structure, and the slide groove is located in the lower middle part of the guide rod structure; the guide rod bearing is fixed in the first circular hole, and the guide rod input shaft is fixed in the second circular hole. The guide rod bearing is fixed on the calf, and the guide rod input shaft is fixed inside the second connecting rod bearing away from the push rod output connector.

[0022] In the above technical solution, the variable stiffness mechanism includes a first bracket of the stiffness adjustment mechanism, a second bracket of the stiffness adjustment mechanism, a ball screw of the stiffness adjustment mechanism, a guide rail of the stiffness adjustment mechanism, a nut of the ball screw of the stiffness adjustment mechanism, a copper sleeve of the guide rail of the stiffness adjustment mechanism, a slider of the stiffness adjustment mechanism, a second bearing of the stiffness adjustment mechanism, a motor of the stiffness adjustment mechanism, an output shaft of the motor of the stiffness adjustment mechanism, an encoder shaft of the motor of the stiffness adjustment mechanism, and an encoder of the motor of the stiffness adjustment mechanism;

[0023] The first bracket of the rigidity adjustment mechanism and the second bracket of the rigidity adjustment mechanism are fixed to each other to form a support frame of the rigidity variable mechanism;

[0024] The two ends of the ball screw of the rigidity adjustment mechanism are respectively connected to the inside of the first bracket of the rigidity adjustment mechanism through the first bearing of the rigidity adjustment mechanism, and the ball screw nut of the rigidity adjustment mechanism is sleeved on the ball screw of the rigidity adjustment mechanism; one end of the ball screw of the rigidity adjustment mechanism close to the second bracket of the rigidity adjustment mechanism is also connected to the output shaft of the rigidity adjustment mechanism motor;

[0025] A guide rail of the rigidity adjustment mechanism parallel to the ball screw of the rigidity adjustment mechanism is fixed inside the first bracket of the rigidity adjustment mechanism, and a copper sleeve of the guide rail of the rigidity adjustment mechanism is mounted on the guide rail of the rigidity adjustment mechanism;

[0026] The ball screw and guide rail of the rigidity adjustment mechanism are both located inside the rigidity adjustment mechanism slider; a fulcrum is provided on both sides of the rigidity adjustment mechanism slider, and a second bearing of the rigidity adjustment mechanism is sleeved on the fulcrum, and the second bearing of the rigidity adjustment mechanism slides in the slide groove of the guide rod;

[0027] The rigidity adjustment mechanism motor includes a stator and a rotor, the rotor is located inside the stator, the stator is located at the upper end of the second bracket of the rigidity adjustment mechanism, the rigidity adjustment mechanism motor output shaft is fixed inside the rotor, and the rigidity adjustment mechanism motor encoder shaft is fixed at the lower end of the rigidity adjustment mechanism motor output shaft;

[0028] The rigidity adjustment mechanism motor encoder comprises a magnetic ring and a reader, wherein the magnetic ring is fixed on the rigidity adjustment mechanism motor encoder shaft, and the reader is fixed on the rigidity adjustment mechanism motor pressure cover.

[0029] In the above technical solution, the calf includes a calf structure, a first joint shaft, a second joint shaft, a leaf spring and a driver C, and the calf structure is U-shaped; the first joint shaft and the second joint shaft are respectively fixed in the holes at the upper end of the calf structure, the outer sides of the first joint shaft and the second joint shaft are respectively connected to the joint bearings, and the inner sides of the first joint shaft and the second joint shaft are respectively connected to the first guide rod and the second guide rod; the leaf spring is fixed in the hole in the middle of the calf structure, and the leaf spring is connected to the shafts with keyways on both sides of the second bracket of the stiffness adjustment mechanism; the driver C is fixed on the calf structure.

[0030] In the above technical solution, the first guide rod, the second guide rod, the variable stiffness mechanism and the calf constitute the variable stiffness module of the knee joint, and the thigh, the push rod, the first connecting rod, the second connecting rod, the first guide rod and the second guide rod constitute the variable reduction ratio module of the knee joint.

[0031] A humanoid robot comprises the above-mentioned knee joint with the functions of variable stiffness and variable reduction ratio.

[0032] The beneficial effects of the present invention are:

[0033] (1) The present invention provides a humanoid robot knee joint with both variable speed ratio and variable stiffness, wherein the variable speed ratio is related to the joint angle and is a passive variable speed ratio, and the variable stiffness is an active variable stiffness, and its stiffness range is 0 to infinity.

[0034] (2) The joint of the present invention has a symmetrical structure. From the output part of the push rod to the calf, the motion-force is transmitted bilaterally, which is more reliable than unilateral transmission. At the same time, bilateral transmission can also enable the joint to have a larger bearing torque.

[0035] (3) The present invention uses a push rod drive method to separate the joint driving part and the stiffness adjustment part, reducing its axial length and making it easier to install it in the knee joint of a humanoid robot.

[0036] (4) The variable stiffness module of the joint in the present invention is connected in series to the rear of the variable reduction ratio module. The two are separated from each other and can be designed and optimized separately.

[0037] (5) In the present invention, there are many parameters related to the joint reduction ratio, and through optimization, a better reduction ratio curve suitable for different high dynamic movements can be obtained.

[0038] (6) The present invention adopts a modular joint design. When different motion requirements of the robot require different reduction ratios, while keeping the upper and lower legs and driving joints unchanged, connecting rods of different lengths can be quickly replaced to change the joint reduction ratio curve.

[0039] (7) The joint stiffness of the present invention is actively adjustable, and different stiffnesses can be suitable for the buffering and energy storage needs of different high-dynamic movements.

[0040] (8) When the fulcrum position in the variable stiffness mechanism of the present invention remains unchanged (at other positions of zero stiffness and infinite stiffness), the stiffness of the joint increases with the increase of the bearing torque, which is more in line with the movement law of human skeletal muscles.

[0041] (9) The variable stiffness mechanism of the present invention has a rolling bearing on the outside of the fulcrum, which reduces the friction and increases the service life of the joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the structure of the humanoid robot knee joint with variable stiffness and variable reduction ratio functions according to the present invention;

[0043] Figure 2 This is a schematic diagram of the thigh structure of the present invention;

[0044] Figure 3 This is a cross-sectional view of the third rotation axis of the thigh according to the present invention;

[0045] Figure 4 is a cross-sectional view of the push rod of the present invention;

[0046] Figure 5 This is a structural diagram of the first housing of the push rod according to the present invention;

[0047] Figure 6 This is the structural diagram of the first connecting rod of the present invention;

[0048] Figure 7 This is a structural diagram of the second connecting rod of the present invention;

[0049] Figure 8 Structural diagram of the first guide rod and the second guide rod of the present invention;

[0050] Figure 9 This is a structural diagram of the variable stiffness mechanism of the present invention;

[0051] Figure 10 This is a structural diagram of the first bracket and the second bracket of the rigidity adjustment mechanism of the present invention;

[0052] Figure 11 This is a cross-sectional view of the variable stiffness mechanism of the present invention;

[0053] Figure 12 This is a structural diagram of the lower leg according to the present invention;

[0054] Figure 13 This is the principle diagram of variable stiffness of the present invention;

[0055] Figure 14 This is a schematic diagram of the joint speed reduction ratio of the present invention;

[0056] In the figure: 100-thigh, 200-push rod, 300-first connecting rod, 400-second connecting rod, 500-guide rod, 500a-first guide rod, 500b-second guide rod, 600-variable stiffness mechanism, 700-calf, 11-first rotating shaft axis, 12-second rotating shaft axis, 13-third rotating shaft axis, 14-fourth rotating shaft axis, 15-fifth rotating shaft axis, 16-sixth rotating shaft axis, 101-thigh structure, 102-thigh first rotating shaft, 103-thigh second rotating shaft, 104-driver A, 105-spherical bearing, 106-spherical bearing first pressure cover, 107-spherical bearing second pressure cover, 108-joint encoder, 1081-joint encoder magnetic ring, 1082-joint Encoder reader, 201-push rod first housing, 202-push rod first bearing, 203-driver mounting plate, 204-driver B, 205-push rod dust cover, 206-push rod heat sink, 207-push rod motor, 208-push rod second housing, 209-push rod encoder, 210-push rod first pressure ring, 211-push rod second bearing, 212-push rod second pressure ring, 213-push rod ball screw, 214-push rod ball screw nut, 215-push rod third housing, 216-push rod third pressure ring, 217-push rod output connector, 2071-push rod motor stator, 2072-push rod motor rotor, 2091-push rod encoder magnetic ring, 2092-push rod encoder reader, 301-first A connecting rod structure, 302-first connecting rod bearing, 401-second connecting rod input shaft, 402-second connecting rod structure, 403-second connecting rod bearing, 501-first guide rod structure, 502-first guide rod bearing, 503-first guide rod bearing baffle, 504-first guide rod input shaft, 505-second guide rod structure, 506-second guide rod bearing, 507-second guide rod bearing baffle, 508-second guide rod input shaft, 601-first bracket of the steel adjustment mechanism, 602-second bracket of the steel adjustment mechanism, 603-fixed plate of the steel adjustment mechanism, 604-first bearing of the steel adjustment mechanism, 605-ball screw of the steel adjustment mechanism, 606-guide rail of the steel adjustment mechanism, 607-ball screw nut of the steel adjustment mechanism, 608- Mechanism locking nut, 609-adjustment mechanism guide rail copper sleeve, 610-adjustment mechanism slider, 611-adjustment mechanism second bearing, 612-adjustment mechanism second bearing baffle, 613-adjustment mechanism motor, 614-adjustment mechanism motor output shaft, 615-adjustment mechanism motor encoder shaft, 616-adjustment mechanism motor pressure cover, 617-adjustment mechanism motor encoder, 6131-adjustment mechanism motor stator, 6132-adjustment mechanism motor rotor, 6171-adjustment mechanism motor encoder magnetic ring, 6172-adjustment mechanism motor encoder reader, 701-calf structure, 702-first joint shaft, 703-second joint shaft, 704-leaf spring, 705-driver C, 706-calf bearing baffle. DETAILED DESCRIPTION

[0057] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

[0058] like Figure 1 As shown, a humanoid robot knee joint with variable stiffness and variable reduction ratio functions according to the present invention comprises a thigh 100, a push rod 200, two first connecting rods 300, a second connecting rod 400, a first guide rod 500a, a second guide rod 500b, a variable stiffness mechanism 600, and a shank 700, wherein the first guide rod 500a and the second guide rod 500b are mirror images of each other. One end of the push rod 200 is pivotally connected to the upper end of the thigh 100, and one end of the first connecting rod 300 is pivotally connected to the lower portion of the thigh 100. The outer side of the other end of the push rod 200 is connected to the other end of the first connecting rod 300. The hole at one end of the second connecting rod 400 is connected to the hole at the other end of the first connecting rod 300, and the second connecting rod 400 is located outside the first connecting rod 300. The center lines of the other end of the push rod 200, the other end of the first connecting rod 300, and one end of the second connecting rod 400 coincide with each other and are defined as the fourth rotation axis 14. The holes at the other end of the second connecting rod 400 are connected to the shafts at the middle outer portions of the first guide rod 500a and the second guide rod 500b, respectively. The centerlines of the other end of the second connecting rod 400, the shafts at the middle outer portions of the first guide rod 500a, and the shafts at the middle outer portions of the second guide rod 500b coincide, defining a fifth rotating shaft axis 15. The holes at the upper ends of the first guide rod 500a and the second guide rod 500b are respectively fixed to the shafts at the upper end of the shank 700 (this shaft axis is the third rotating shaft axis 13). A chute is provided in each of the first guide rod 500a and the second guide rod 500b, and the variable stiffness mechanism 600 is provided with a fulcrum and is slidable within the chute. The shafts with keyways on both sides of the variable stiffness mechanism 600 are fixed to the shank 700, and the axis of the cylinder is defined as the sixth rotating shaft axis 16.

[0059] like Figure 2 and Figure 3As shown, thigh 100 comprises a thigh structure 101, a first thigh shaft 102, a second thigh shaft 103, a driver A 104, two spherical bearings 105, a first spherical bearing pressure cap 106, a second spherical bearing pressure cap 107, and a joint encoder 108. The centerlines of the first thigh shaft 102 and the second thigh shaft 103 are designated as the first shaft axis 11 and the second shaft axis 12, respectively. The centerlines of the two cylinders at the lower end of thigh structure 101 are designated as the third shaft axis 13. The thigh first rotating shaft 102 and the thigh second rotating shaft 103 are respectively fixed in holes at the upper and lower ends of the thigh structural member 101. One end of the push rod 200 is rotatably connected to the thigh first rotating shaft 102 and can rotate about the first rotating shaft axis 11. One end of the first connecting rod 300 is connected to the thigh second rotating shaft 103 and can rotate about the second rotating shaft axis 12. The calf 700 is connected to the lower end of the thigh structural member 101 and can rotate about the third rotating shaft axis 13. Driver A 104 is fixed to the back plate of the thigh structural member 101. Two spherical bearings 105 are respectively fixed in cylindrical holes at the lower end of the thigh structural member 101 and secured by a first spherical bearing pressure cap 106 and a second spherical bearing pressure cap 107, respectively. The first spherical bearing pressure cap 106 and the second spherical bearing pressure cap 107 are respectively fixed to the sidewalls of the thigh structural member 101. The joint encoder 108 consists of a joint encoder magnetic ring 1081 and a joint encoder reader 1082 . The joint encoder reader 1082 is fixed to the outside of the first joint bearing pressure cover 106 , and the joint encoder magnetic ring 1081 is fixed to the first calf joint shaft 702 .

[0060] like Figure 4As shown, the push rod 200 comprises a push rod first housing 201, a push rod first bearing 202, a driver mounting plate 203, a driver B 204, a push rod dust cover 205, a push rod heat sink 206, a push rod motor 207, a push rod second housing 208, a push rod encoder 209, a push rod first pressure ring 210, a push rod second bearing 211, a push rod second pressure ring 212, a push rod ball screw 213, a push rod ball screw nut 214, a push rod third housing 215, a push rod third pressure ring 216, and a push rod output connector 217. The push rod first bearing 202 is fixed to a circular hole in the push rod first housing 201 and is rotationally connected to the thigh first rotating shaft 102. The driver mounting plate 203 is fixed to the push rod first housing 201, and the driver B 204 is fixed to the driver mounting plate 203. The push rod heat sink 206 is circumferentially fixed to the push rod first housing 201 to facilitate heat dissipation from the push rod motor 207. The push rod third housing 215 is fixed to the lower end of the push rod second housing 208. The push rod second housing 208 is connected to the push rod first housing 201 via the push rod second bearing 211. The push rod third housing 215 and the push rod second housing 208 can rotate around the push rod first housing 201 and are coaxial. The push rod motor 207 consists of a push rod motor stator 2071 and a push rod motor rotor 2072. The push rod motor stator 2071 is located inside the push rod first housing 201, and the push rod motor rotor 2072 is located inside the push rod motor stator 2071 and fixed to the push rod second housing 208. The ball screw nut 214 is fixed inside the push rod third housing 215, and the push rod ball screw 213 is located inside the push rod ball screw nut 214. When the push rod motor stator 2071 drives the push rod motor rotor 2072 to rotate, the push rod ball screw nut 214 can be driven to rotate via the push rod second housing 208 and the push rod third housing 215, thereby driving the push rod ball screw 213 to move along its axis. The push rod encoder 209 consists of a push rod encoder magnetic ring 2091 and a push rod encoder reader 2092. The push rod encoder magnetic ring 2091 is fixed to the push rod second housing 208, and the push rod encoder reader 2092 is fixed to the push rod first housing 201. The angle read by the push rod encoder reader 2092 is the relative rotation angle between the push rod encoder magnetic ring 2091 and the push rod encoder reader 2092, that is, the angle at which the push rod motor rotor 2072 and the push rod ball screw nut 214 rotate about their axes. The first push rod pressure ring 210 is fixed to the side of the first push rod housing 201 and is used to press the push rod motor stator 2071. The second push rod pressure ring 212 is fixed to the side of the third push rod housing 215 and is used to press the second push rod bearing 211. The third push rod pressure ring 216 is fixed to the third push rod housing 215 and is used to press the push rod ball screw nut 214 to prevent it from falling off. The push rod output connector 217 is fixed to the end of the push rod ball screw 213 and serves as the output part of the push rod 200. The upper end of the first push rod housing 201 is a hollow U-shaped structure ( Figure 5), the push rod dust cover 205 is installed inside the U-shaped structure, located at the upper end of the push rod ball screw 213, with a gap between the two, and the push rod dust cover 205 is coaxial with the push rod ball screw 213.

[0061] like Figure 6 As shown, the first connecting rod 300 is in a straight line shape and consists of a first connecting rod structure 301 and a first connecting rod bearing 302. Round holes are provided at both ends of the first connecting rod structure 301, and the first connecting rod bearing 302 is fixed inside the round holes.

[0062] like Figure 7 As shown, the second connecting rod 400 is H-shaped and consists of a second connecting rod input shaft 401, a second connecting rod structural member 402 and a second connecting rod bearing 403. The axes of the holes on both sides of the second connecting rod structural member 402 coincide with the fourth rotating shaft axis 14 and the fifth rotating shaft axis 15 respectively. The second connecting rod bearing 403 is located in the holes on both sides of the second connecting rod structural member 402. The second connecting rod input shaft 401 is located in the hole on one side of the second connecting rod structural member 402 and coincides with the fourth rotating shaft axis 14.

[0063] like Figure 8 As shown, the first guide rod 500a is composed of a first guide rod structure 501, a first guide rod bearing 502, a first guide rod bearing baffle 503 and a first guide rod input shaft 504. The first guide rod structure 501 is provided with a first circular hole (the hole at the upper end), a second circular hole (the hole in the middle) and a slide groove. The first guide rod bearing 502 is fixed in the first circular hole of the first guide rod structure 501, the first guide rod input shaft 504 is fixed in the second circular hole of the first guide rod structure 501, and the first guide rod bearing baffle 503 is fixed outside the first circular hole of the first guide rod structure 501. The axis of the first circular hole of the first guide rod structure 501 coincides with the axis of the third rotating shaft 13, and the axis of the second circular hole of the first guide rod structure 501 coincides with the axis of the fifth rotating shaft 15. The structure of the second guide rod 500b consists of a second guide rod structural member 505, a second guide rod bearing 506, a second guide rod bearing baffle 507 and a second guide rod input shaft 508. The specific structure is the same as that of the first guide rod 500a and will not be repeated here.

[0064] like Figure 9 、 10As shown in Figures 11, the variable stiffness mechanism 600 comprises a first stiffness adjustment mechanism bracket 601, a second stiffness adjustment mechanism bracket 602, a stiffness adjustment mechanism fixing plate 603, two first stiffness adjustment mechanism bearings 604, a stiffness adjustment mechanism ball screw 605, a stiffness adjustment mechanism guide rail 606, a stiffness adjustment mechanism ball screw nut 607, a stiffness adjustment mechanism locking nut 608, a stiffness adjustment mechanism guide rail copper sleeve 609, a stiffness adjustment mechanism slider 610, a stiffness adjustment mechanism second bearing 611, a stiffness adjustment mechanism second bearing stopper 612, a stiffness adjustment mechanism motor 613, a stiffness adjustment mechanism motor output shaft 614, a stiffness adjustment mechanism motor encoder shaft 615, a stiffness adjustment mechanism motor gland 616, and a stiffness adjustment mechanism motor encoder 617. The first stiffness adjustment mechanism bracket 601 and the second stiffness adjustment mechanism bracket 602 are fixed to each other, forming a support frame for the other components of the variable stiffness mechanism 600. Axes with keyways are provided on both sides of the second stiffness adjustment mechanism bracket 602 for connecting to the leaf spring 704. The two first bearings 604 of the rigid adjustment mechanism are located in the internal holes of the first bracket 601 of the rigid adjustment mechanism. A rigid adjustment mechanism fixing plate 603 fixed to the first bracket 601 prevents the first bearings 604 from falling out. The rigid adjustment mechanism guide rail 606 is fixed inside the first bracket 601. The ends of the rigid adjustment mechanism ball screw 605 are fixed inside the two first bearings 604, allowing the rigid adjustment mechanism ball screw 605 to rotate about its axis. The rigid adjustment mechanism ball screw nut 607 and the rigid adjustment mechanism guide rail copper sleeve 609 are both fixed inside the rigid adjustment mechanism slider 610. The rigid adjustment mechanism ball screw nut 607 is mounted on the rigid adjustment mechanism ball screw 605. The rigid adjustment mechanism locking nut 608 is located at one end of the rigid adjustment mechanism slider 610 and is used to secure the rigid adjustment mechanism ball screw nut 607. The rigid adjustment mechanism guide rail copper sleeve 609 is mounted on the rigid adjustment mechanism guide rail 606. The rigidity adjustment mechanism slider 610 moves along the axis of the rigidity adjustment mechanism ball screw 605 (i.e., the axis of the rigidity adjustment mechanism guide rail 606). Pivot points are provided on either side of the rigidity adjustment mechanism slider 610. The rigidity adjustment mechanism second bearing 611 is mounted on and pivots around these pivot points. A rigidity adjustment mechanism second bearing stopper 612 is fixed to the outside of the pivot point to prevent the rigidity adjustment mechanism second bearing 611 from falling off.The rigidity adjustment mechanism motor 613 is composed of a rigidity adjustment mechanism motor stator 6131 and a rigidity adjustment mechanism motor rotor 6132, and the rigidity adjustment mechanism motor rotor 6132 is located inside the rigidity adjustment mechanism motor stator 6131, and the rigidity adjustment mechanism motor stator 6131 is located in a shell composed of the upper end of the rigidity adjustment mechanism second bracket 602 and the rigidity adjustment mechanism motor pressure cover 616. The rigidity adjustment mechanism motor output shaft 614 is fixed on the inner side of the rigidity adjustment mechanism motor rotor 6132, and the rigidity adjustment mechanism motor encoder shaft 615 is fixed on the lower end of the rigidity adjustment mechanism motor output shaft 614; the rigidity adjustment mechanism motor encoder 617 is composed of a rigidity adjustment mechanism motor encoder magnetic ring 6171 and a rigidity adjustment mechanism motor encoder reader 6172, the rigidity adjustment mechanism motor encoder magnetic ring 6171 is fixed on the rigidity adjustment mechanism motor encoder shaft 615, and the rigidity adjustment mechanism motor encoder reader 6172 is fixed on the rigidity adjustment mechanism motor pressure cover 616. One end of the rigidity adjustment mechanism ball screw 605 close to the rigidity adjustment mechanism second bracket 602 is also connected to the rigidity adjustment mechanism motor output shaft 614.

[0065] like Figure 12 As shown, the shank 700 comprises a shank structure 701, a first joint shaft 702, a second joint shaft 703, two leaf springs 704, a driver C705, and a shank bearing block 706. The shank structure 701 is U-shaped. The first joint shaft 702 and the second joint shaft 703 are respectively fixed in holes on the upper side of the shank structure 701. Specifically, the first joint shaft 702 is fixed in the hole on the left side of the shank structure 701, and the second joint shaft 703 is fixed in the hole on the right side of the shank structure 701. The outer sides of the first joint shaft 702 and the second joint shaft 703 are respectively connected to the joint bearing 105, and the inner sides are respectively connected to the first guide rod bearing 502 and the second guide rod bearing 506. The two leaf springs 704 are fixed in the hole in the middle of the shank structure 701. The axis of the upper hole of the shank structure 701 coincides with the axis of the third rotating shaft 13, and the axis of the middle hole coincides with the axis of the sixth rotating shaft 16. The two shank bearing blocks 706 are respectively fixed on the inner sides of the first joint shaft 702 and the second joint shaft 703. The driver C705 is fixed on the shank structure 701.

[0066] The stiffness-changing principle of the humanoid robot knee joint with the function of variable stiffness and variable reduction ratio is as follows: Figure 13The guide rods 500 (first guide rod 500a and second guide rod 500b), the variable stiffness mechanism 600, and the shank 700 form the joint's variable stiffness module. The guide rods 500 (first guide rod 500a and second guide rod 500b) rotate about the third rotation axis 13. The fulcrums of the variable stiffness mechanism 600 (i.e., the fulcrums on both sides of the stiffness adjustment mechanism slider 610) are located within the chute of the first guide rod 500a and second guide rod 500b and can move within the chute. The variable stiffness mechanism 600 is fixed to the leaf spring 704 of the shank 700. The first guide rod 500a and second guide rod 500b are the input components, and the shank 700 is the output component. When the joint does not bear external torque (that is, when the calf 700 has no torque output), the first guide rod 500a, the second guide rod 500b, the variable stiffness mechanism 600, and the calf 700 are collinear, that is, the angle value of θ1 is 0. When there is an external torque, due to the flexibility of the leaf spring 704, the first guide rod 500a, the second guide rod 500b and the calf 700 form an angle θ1. This angle is related to the external torque and is defined as the joint deformation angle. At the same time, under the action of the external torque, the deformation angle of the leaf spring 704 is θ2. The length of the variable stiffness mechanism 600 (the distance from the fulcrum axis to the leaf spring axis) can be adjusted according to the stiffness adjustment mechanism ball screw 605, specifically: control the computer, send control instructions through the driver C705, drive the stiffness adjustment mechanism motor rotor 6132 in the stiffness adjustment mechanism motor 613 to rotate, thereby driving the stiffness adjustment mechanism ball screw 605 to rotate through the stiffness adjustment mechanism motor output shaft 614. Due to the existence of the stiffness adjustment mechanism guide rail 606, the rotation of the stiffness adjustment mechanism ball screw 605 will cause the stiffness adjustment mechanism slider 610 to move linearly along the stiffness adjustment mechanism guide rail 606 (stiffness adjustment mechanism ball screw 605), and the fulcrum on the stiffness adjustment mechanism slider 610 moves linearly along the stiffness adjustment mechanism guide rail 606 (stiffness adjustment mechanism ball screw 605). The length ratio of variable stiffness mechanism 600 and shank 700 is defined as r. The joint's load moment and joint stiffness decrease as r increases. When r is 0, the joint stiffness is infinite, and when r is 1, the joint stiffness is 0. The joint stiffness also increases with increasing joint deformation angle θ1, which is consistent with the changing stiffness characteristics of human skeletal muscle.

[0067] The following is an explanation of the relationship between the joint load moment T and the joint deformation angle θ1 and the calculation formula of their differential relationship (i.e., the relationship between the joint stiffness K and θ1):

[0068] The relationship between θ1 and θ2 is:

[0069] The work done by the joint bearing torque T on the joint deformation angle θ1 is equal to the energy stored in the leaf spring 704, that is: Wherein, k is twice the stiffness of the leaf spring 704;

[0070] According to the above formula, the relationship between the joint load moment T and the joint deformation angle θ1 can be calculated as follows:

[0071]

[0072] By differentiating the above formula with respect to θ1, we can obtain the relationship between the joint stiffness K and the joint deformation angle θ1:

[0073]

[0074] The above formulas show that both joint load torque T and joint stiffness K are related to r and θ1. When θ1 remains constant, T and K decrease as r decreases. When r remains constant, T and K increase as θ1 increases, which is consistent with the changing characteristics of biological skeletal muscle stiffness. When r is 0, the joint stiffness is infinite, and when r is 1, the joint stiffness is 0.

[0075] The invention provides a humanoid robot knee joint with variable stiffness and variable reduction ratio function. The reduction ratio principle is as follows: Figure 14As shown, the thigh 100, push rod 200, two first connecting rods 300, the second connecting rod 400, and the first guide rod 500a and the second guide rod 500b constitute a speed reduction ratio module. When the length of the push rod 200 changes, the push rod 200 will drive the first connecting rod 300 to rotate about the second rotating shaft axis 12. The first connecting rod 300, the second connecting rod 400, the guide rods 500 (the first guide rod 500a and the second guide rod 500b), and the portion between the second rotating shaft axis 12 and the third rotating shaft axis 13 form a four-bar linkage. Therefore, the rotation of the first connecting rod 300 about the second rotating shaft axis 12 will drive the guide rods 500 (the first guide rod 500a and the second guide rod 500b) to move about the third rotating shaft axis 13. The length of push rod 200 changes as follows: The control computer sends control instructions via driver B204, driving push rod motor rotor 6132 in push rod motor 207 to rotate, thereby driving push rod second housing 208 and push rod third housing 216 to rotate, which in turn drives push rod ball screw nut 214 to rotate, thereby driving push rod ball screw 213 to move along its axial direction, thereby changing the length of push rod 200. The ratio of the rotation angle of push rod motor rotor 2172 in push rod motor 207 to the rotation angle of guide rod 500 is not constant, so this knee joint is a variable reduction ratio joint. Before the calculation formula of the reduction ratio and the joint angle, the following definitions are made: the distance between the first rotating shaft axis 11 and the second rotating shaft axis 12 is L0, the distance between the second rotating shaft axis 12 and the third rotating shaft axis 13 is L1, the distance between the third rotating shaft axis 13 and the fourth rotating shaft axis 14 is L2, the distance between the fourth rotating shaft axis 14 and the fifth rotating shaft axis 15 is L3, and the distance between the third rotating shaft axis 13 and the fifth rotating shaft axis 15 is L4. β1 is the angle between the line connecting the second rotating shaft axis 12 and the fourth rotating shaft axis 14 and the line connecting the second rotating shaft axis 12 and the third rotating shaft axis 13, that is, the angle between the first connecting rod 300 and the thigh 100. β2 is the angle between the extended line connecting the second rotating shaft axis 12 and the third rotating shaft axis 13 and the line connecting the third rotating shaft axis 13 and the fifth rotating shaft axis 15, that is, the angle between the guide rod 500 and the thigh 100. h is the pitch of the push rod ball screw 213. The calculation formula of the reduction ratio of the joint is as follows:

[0076] Push rod 200 speed and the rotation angle of the push rod motor 207 The relationship is:

[0077] The rotation speed of the first connecting rod 300 With push rod 200 speed The ratio is:

[0078]

[0079] Rotation angle of the guide rod 500 The rotation speed of the first connecting rod 300 The ratio is:

[0080]

[0081] The reduction ratio of the joint is: R = R1 × R2 × R3.

[0082] By changing the lengths of L0, L1, L2, L3 and L4, the change rule of the joint reduction ratio and the movement angle β2 of the guide rod 500 can be changed, that is, the variable reduction ratio of the joint is achieved.

[0083] The present invention provides a humanoid robot knee joint with a variable stiffness module and a variable reduction ratio function, wherein the module is connected in series to the rear end of the variable reduction ratio module. The knee joint motion angle α is the sum of β2 and θ1. Therefore, during the robot design process, the joint deformation angle θ1 can be calculated based on the joint torque required for the robot movement. Then, the relationship between the motion angle β2 of the variable stiffness mechanism and the required joint torque is calculated based on the joint motion angle α and the joint deformation angle θ1. Based on this relationship, the reduction ratio of the joint can be optimized to obtain a reduction ratio law that is more suitable for the robot's high dynamic motion. Since the optimization variables include the lengths of L0, L1, L2, L3 and L4, the design can optimize a better reduction ratio variation law. In the robot's motion control, the joint angle α can be measured by the joint encoder 108, and the angle value is sent to the control computer through the driver A104, thereby realizing the joint angle reading during the robot's motion process.

[0084] The embodiments described are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention are within the scope of protection of the present invention.

Claims

1. A knee joint of a humanoid robot with variable stiffness and variable reduction ratio functions, characterized in that: The invention comprises a thigh (100), a push rod (200), a first connecting rod (300), a second connecting rod (400), a first guide rod (500a), a second guide rod (500b), a variable stiffness mechanism (600) and a calf (700), wherein the first guide rod (500a) and the second guide rod (500b) are mirror images of each other; The upper end of the thigh (100) is rotatably connected to the upper end of the push rod (200), the lower part of the thigh (100) is rotatably connected to one end of the two first connecting rods (300), and the lower end of the thigh (100) is rotatably connected to the upper end of the calf (700); The lower end of the push rod (200) is coaxially rotatably connected to the other ends of the two first connecting rods (300) and one end of the second connecting rod (400) in sequence from the inside to the outside, and the other end of the second connecting rod (400) is rotatably connected to the shaft in the middle of the outer sides of the first guide rod (500a) and the second guide rod (500b); The upper ends of the first guide rod (500a) and the second guide rod (500b) are respectively rotatably connected to the inner side of the shaft at the upper end of the calf (700); the first guide rod (500a) and the second guide rod (500b) are respectively provided with a sliding groove, and the variable stiffness mechanism (600) is provided with a fulcrum sliding in the sliding groove; the variable stiffness mechanism (600) is also connected to the leaf spring (704) of the calf (700); The variable stiffness mechanism (600) comprises a stiffness adjustment mechanism first bracket (601), a stiffness adjustment mechanism second bracket (602), a stiffness adjustment mechanism ball screw (605), a stiffness adjustment mechanism guide rail (606), a stiffness adjustment mechanism ball screw nut (607), a stiffness adjustment mechanism guide rail copper sleeve (609), a stiffness adjustment mechanism slider (610), a stiffness adjustment mechanism second bearing (611), a stiffness adjustment mechanism motor (613), a stiffness adjustment mechanism motor output shaft (614), a stiffness adjustment mechanism motor encoder shaft (615), and a stiffness adjustment mechanism motor encoder (617); The first bracket (601) of the rigidity adjustment mechanism and the second bracket (602) of the rigidity adjustment mechanism are fixed to each other to form a support frame of the rigidity variable mechanism (600); The two ends of the rigidity adjustment mechanism ball screw (605) are connected to the interior of the rigidity adjustment mechanism first bracket (601) through the rigidity adjustment mechanism first bearing (604), and the rigidity adjustment mechanism ball screw nut (607) is sleeved on the rigidity adjustment mechanism ball screw (605); one end of the rigidity adjustment mechanism ball screw (605) close to the rigidity adjustment mechanism second bracket (602) is also connected to the rigidity adjustment mechanism motor output shaft (614); A rigidity adjustment mechanism guide rail (606) parallel to the rigidity adjustment mechanism ball screw (605) is fixed inside the rigidity adjustment mechanism first bracket (601), and the rigidity adjustment mechanism guide rail copper sleeve (609) is sleeved on the rigidity adjustment mechanism guide rail (606); The rigidity adjustment mechanism ball screw (605) and the rigidity adjustment mechanism guide rail (606) are both located inside the rigidity adjustment mechanism slider (610); fulcrums are provided on both sides of the rigidity adjustment mechanism slider (610), and the rigidity adjustment mechanism second bearing (611) is sleeved on the fulcrum, and the rigidity adjustment mechanism second bearing (611) slides in the guide rod slide groove; The rigidity adjustment mechanism motor (613) comprises a stator and a rotor, the rotor being located inside the stator, the stator being located at the upper end of the rigidity adjustment mechanism second bracket (602), the rigidity adjustment mechanism motor output shaft (614) being fixed inside the rotor, and the rigidity adjustment mechanism motor encoder shaft (615) being fixed at the lower end of the rigidity adjustment mechanism motor output shaft (614); The rigidity adjustment mechanism motor encoder (617) comprises a magnetic ring and a reader, wherein the magnetic ring is fixed on the rigidity adjustment mechanism motor encoder shaft (615), and the reader is fixed on the rigidity adjustment mechanism motor pressure cover (616).

2. The humanoid robot knee joint with variable stiffness and variable reduction ratio functions according to claim 1, characterized in that: The thigh (100) includes a thigh structure (101), a first thigh rotation shaft (102), a second thigh rotation shaft (103), a driver A (104) and a joint bearing (105); the first thigh rotation shaft (102) and the second thigh rotation shaft (103) are respectively fixed in the holes at the upper end and the lower part of the thigh structure (101), and are used to connect the upper end of the push rod (200) and one end of the first connecting rod (300); the driver A (104) is fixed on the thigh structure (101); the joint bearing (105) is respectively fixed in the cylindrical hole at the lower end of the thigh structure (101), and is used to connect the calf (700); the thigh (100) also includes a joint encoder (108), and the joint encoder (108) includes a magnetic ring and a reader, the reader is fixed in the cylindrical hole at the lower end of the thigh structure (101), and the magnetic ring is fixed on the calf (700).

3. The knee joint of the humanoid robot with variable stiffness and variable reduction ratio functions according to claim 2, characterized in that: The push rod (200) comprises a push rod first housing (201), a driver B (204), a push rod motor (207), a push rod second housing (208), a push rod encoder (209), a push rod ball screw (213), a push rod ball screw nut (214), a push rod third housing (216) and a push rod output connector (217); The push rod first housing (201) is rotatably connected to the thigh first rotating shaft (102) via the push rod first bearing (202); The driver B (204) is mounted on the first push rod housing (201); The push rod third housing (216) is fixed to the lower end of the push rod second housing (208), and the push rod second housing (208) is connected to the push rod first housing (201) via the push rod second bearing (211); The push rod motor (207) includes a stator and a rotor, wherein the stator is located inside the push rod first housing (201), the rotor is located inside the stator, and the rotor is fixed on the push rod second housing (208); A push rod ball screw nut (214) is fixed inside the push rod third housing (216), the push rod ball screw nut (214) is sleeved on the push rod ball screw (213), and a push rod output connector (217) is fixed at the end of the push rod ball screw (213); The push rod encoder (209) comprises a magnetic ring and a reader, wherein the magnetic ring is fixed on the push rod second housing (208) and the reader is fixed on the push rod first housing (201).

4. The knee joint of the humanoid robot with variable stiffness and variable reduction ratio functions according to claim 3, characterized in that: The first connecting rod (300) is in a straight line shape and consists of a first connecting rod structure (301) and a first connecting rod bearing (302); circular holes are provided at both ends of the first connecting rod structure (301), and the first connecting rod bearing (302) is fixed inside the circular holes and is respectively connected to the second rotating shaft (103) of the thigh and the second connecting rod (400).

5. The knee joint of the humanoid robot with variable stiffness and variable reduction ratio functions according to claim 4, characterized in that: The second connecting rod (400) is H-shaped and consists of a second connecting rod input shaft (401), a second connecting rod structural member (402) and a second connecting rod bearing (403); circular holes are provided at both ends of the second connecting rod structural member (402), and the second connecting rod bearing (403) is fixed inside the circular holes; the second connecting rod input shaft (401) is provided inside the second connecting rod bearing (403) near one end of the push rod output connecting member (217); the second connecting rod input shaft (401) is sequentially sleeved with the push rod output connecting member (217), the first connecting rod structural member (301) and the second connecting rod structural member (402) from the inside to the outside.

6. The knee joint with variable stiffness and variable reduction ratio function of the humanoid robot according to claim 5, characterized in that: The first guide rod (500a) and the second guide rod (500b) are both composed of a guide rod structure, a guide rod bearing and a guide rod input shaft. The guide rod structure is provided with a first circular hole, a second circular hole and a slide groove. The first circular hole is located at the upper end of the guide rod structure, the second circular hole is located in the middle of one side of the guide rod structure, and the slide groove is located in the lower middle part of the guide rod structure. The guide rod bearing is fixed in the first circular hole, and the guide rod input shaft is fixed in the second circular hole. The guide rod bearing is fixed on the shank (700), and the guide rod input shaft is rotatably connected to the inside of the second connecting rod bearing (403) away from the push rod output connector (217).

7. The knee joint of the humanoid robot with variable stiffness and variable reduction ratio functions according to claim 6, characterized in that: The calf (700) comprises a calf structure (701), a first joint shaft (702), a second joint shaft (703), a leaf spring (704) and a driver C (705). The calf structure (701) is U-shaped; the first joint shaft (702) and the second joint shaft (703) are respectively fixed in holes at the upper end of the calf structure (701); the outer sides of the first joint shaft (702) and the second joint shaft (703) are respectively connected to joint bearings (105); the inner sides of the first joint shaft (702) and the second joint shaft (703) are respectively connected to the first guide rod (500a) and the second guide rod (500b); the leaf spring (704) is fixed in a hole in the middle of the calf structure (701); the leaf spring (704) is connected to shafts with keyways on both sides of the second bracket (602) of the rigidity adjustment mechanism; and the driver C (705) is fixed on the calf structure (701).

8. The knee joint of the humanoid robot with variable stiffness and variable reduction ratio functions according to claim 7, characterized in that: The first guide rod (500a), the second guide rod (500b), the variable stiffness mechanism (600) and the calf (700) constitute a variable stiffness module of the knee joint, and the thigh (100), the push rod (200), the first connecting rod (300), the second connecting rod (400), the first guide rod (500a) and the second guide rod (500b) constitute a variable speed ratio module of the knee joint.

9. A humanoid robot, characterized in that: A knee joint with variable stiffness and variable reduction ratio functions comprising the knee joint according to any one of claims 1 to 8.

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