A parallel coupled hydraulically driven robot joint

Abstract

A parallel-coupled hydraulically driven robot joint relates to the field of hydraulically driven robot joint structures. The present invention solves the problems of existing humanoid robots, such as small lateral swing joint rotation angle, complex transmission, small motion driving force, and unstable motion. The hydraulic cylinder of the present invention is an upper and lower double-cylinder structure, and the two pistons are slidably and sealedly inserted in the upper cylinder and the lower cylinder of the hydraulic cylinder respectively. One end of the two transmission rods is rotatably connected to the two pistons through two rotating shafts, and the other ends of the two transmission rods are rotatably connected to the upper and lower ends of two rotating rods arranged side by side through two rotating shafts. The output shaft is a spline shaft, and the middle parts of the two rotating rods are respectively installed in the middle of the output shaft through two spline sleeves. Two coaxially arranged cylinder sleeves are respectively provided on both sides of the front end of the hydraulic cylinder, and the two ends of the output shaft are rotatably connected to the two cylinder sleeves. The present invention is used to realize the lateral swing freedom of the robot leg.

Description

Technical Field

[0001] The present invention relates to the field of hydraulically driven robot joint structures, in particular to the side swing structures of hip joints and shoulder joints of hydraulic humanoid robots, and specifically to a parallel coupled hydraulically driven robot joint. Background Art

[0002] Humanoid robots offer a range of significant advantages over wheeled and tracked robots: they can better adapt to various terrains, consume less energy, operate over a wider area, and mimic the human walking pattern. These robots can move freely without altering the human living environment, and their anthropomorphic appearance makes them more accessible to humans. The side-swing mechanism in a robot's legs allows the thigh to swing horizontally. This design mimics the natural side-to-side swing of the human thigh when walking or running, enhancing the naturalness and efficiency of the robot's walking. The side-swing mechanism is crucial for achieving precise control of the robot's leg movements and enabling the robot to adapt to varying walking conditions and speeds.

[0003] The PET bipedal robot, developed by Boston Dynamics in 2009, consists of only three parts: two legs and a main body. The legs utilize serially articulated legs, each with five active degrees of freedom. In 2015, the Atlas-Unplugged, released after several iterations, boasts 28 degrees of freedom. It utilizes an onboard hydraulic drive system, offering superior dynamic balance and enabling tasks such as navigating debris-strewn surfaces and climbing stairs. In 2017, Agility Robotics developed the more efficient and compact bipedal robot, Cassie, by increasing the degrees of freedom of the ATRIAS robot's legs from three to seven. This robot utilizes a planar four-bar linkage with the knee drive motors mounted at the hips to minimize weight at the rear end of the legs. As can be seen from the above solutions, hydraulic robots currently primarily improve motion quality by increasing degrees of freedom, while the thigh's lateral swing mechanism is typically achieved using linear hydraulic cylinders coupled with a transmission mechanism. The complex transmission structure is mostly arranged on the inner side of the thigh, namely the pelvis. This design increases the lateral width of the pelvis, making the distance between the two legs too large. Not only does it have problems of high complexity and redundancy in the mechanical structure, but it is also difficult to maintain balance, which will bring many difficulties to the robot's motion control.

[0004] In summary, existing humanoid robots have problems such as small side-swing joint rotation angle, complex transmission, small motion driving force, and unstable motion. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of existing humanoid robots such as small side swing joint rotation angle, complex transmission, small motion driving force and unstable motion, and to provide a parallel coupled hydraulic drive robot joint.

[0006] The technical solution of the present invention is:

[0007] A parallel-coupled hydraulically driven robot joint comprises a hydraulic cylinder 12, an output shaft 9, two spline sleeves 10, two rotating rods 2, two transmission rods 3 and two pistons 5. The hydraulic cylinder 12 is an upper and lower double-cylinder structure. The two pistons 5 are respectively slidably sealed and inserted in the upper cylinder and the lower cylinder of the hydraulic cylinder 12. One end of the two transmission rods 3 is rotatably connected to the two pistons 5 through two rotating shafts, and the other ends of the two transmission rods 3 are rotatably connected to the upper and lower ends of the two rotating rods 2 arranged side by side through two rotating shafts. The output shaft 9 is a spline shaft, and the middle parts of the two rotating rods 2 are respectively installed in the middle part of the output shaft 9 through two spline sleeves. Two coaxially arranged cylinder sleeves are respectively provided on both sides of the front end of the hydraulic cylinder 12, and the two ends of the output shaft 9 are respectively rotatably connected to the two cylinder sleeves.

[0008] Furthermore: it also includes a magnetic encoder flange 6 and a magnet 7. A magnet mounting hole is processed in the center of the end face of one side of the output shaft 9. The magnet 7 is inserted into the magnet mounting hole. The magnetic encoder flange 6 is coaxially arranged on the side of the magnet 7. The magnetic encoder flange 6 is connected to the corresponding cylinder sleeve end.

[0009] Furthermore, it also includes two output bearings 8. The side surfaces at both ends of the output shaft 9 are processed into cylindrical surfaces. The two ends of the output shaft 9 are rotatably connected to the two cylinder sleeves through the two output bearings 8 respectively.

[0010] Furthermore, it also includes two fixed bearings 11, and the two fixed bearings 11 are respectively sleeved on the two cylinder sleeves.

[0011] Furthermore, it also includes two piston sealing rings 4, and two first annular sealing grooves are processed on the sides of the two pistons 5 along the circumferential direction. The two piston sealing rings 4 are respectively arranged in the two first annular sealing grooves, and the two pistons 5 are respectively slidably sealed with the upper cylinder barrel and the lower cylinder barrel of the hydraulic cylinder barrel 12 through the two piston sealing rings 4.

[0012] Furthermore, it also includes two cylinder heads and two cylinder head sealing rings 13. The rear ends of the upper cylinder barrel and the lower cylinder barrel of the hydraulic cylinder barrel 12 are provided with an integrally formed annular cylinder seat. Two cylinder head mounting holes are processed on the annular cylinder seat. The two cylinder head mounting holes correspond one to one with the upper cylinder barrel and the lower cylinder barrel respectively. The two cylinder heads are coaxially installed in the two cylinder head mounting holes respectively. Two second annular sealing grooves are processed on the side surfaces of the two cylinder heads respectively along the circumferential direction. The two cylinder head sealing rings 13 are respectively sleeved in the two second annular sealing grooves. The two cylinder heads are sealed with the annular cylinder seat respectively through the two cylinder head sealing rings 13.

[0013] Furthermore, it also includes a bottom valve plate 14 and a hydraulic servo valve 15. The bottom valve plate 14 is installed at the rear end center of the annular cylinder seat, and the hydraulic servo valve 15 is installed at the rear end of the bottom valve plate 14. The bottom valve plate 14 is internally processed with two first oil circuits connecting the hydraulic servo valve 15 and the upper cylinder barrel and the lower cylinder barrel of the hydraulic cylinder barrel 12.

[0014] Furthermore, it also includes two oil pressure sensors 16. Two oil pressure sensors 16 are respectively provided on the upper and lower sides of the hydraulic servo valve 15. The two oil pressure sensors 16 are both installed at the rear end of the bottom valve plate 14. Two second oil circuits connecting the two oil pressure sensors 16 and the upper and lower cylinders of the hydraulic cylinder 12 are provided inside the bottom valve plate 14.

[0015] Furthermore, it also includes a protective shell 1, which is a semicircular shell. The protective shell 1 is buckled at the front end of the hydraulic cylinder 12, and the middle of both sides of the protective shell 1 are processed with avoidance grooves that match the two cylinder shaft sleeves.

[0016] Furthermore, the hydraulic cylinder 12 is made of titanium alloy using 3D printing technology.

[0017] Compared with various existing robot side swing joints, the parallel coupling hydraulic drive robot joint of the present invention has the following beneficial effects:

[0018] 1. The present invention provides a parallel-coupled hydraulically driven robot joint that can achieve a larger rotation angle: by arranging the side swing joint on the outside of the pelvis, a larger leg swing angle can be achieved without interfering with the pelvic structure, and a large swing angle can be easily achieved.

[0019] 2. This invention features a parallel-coupled hydraulically driven robotic joint with optimized piping and transmission structure: hydraulic oil flows directly into the hydraulic cylinder from a drive shaft connected to the cylinder body, eliminating the need for additional oil lines and reducing manufacturing complexity and costs. The housing is manufactured using 3D printing technology, simplifying overall fabrication and facilitating easy installation and disassembly, making the entire transmission structure more compact.

[0020] 3. This invention features a parallel-coupled hydraulically driven robot joint that reduces joint volume: This joint utilizes a dual-cylinder design, resulting in a piston 5 whose actual travel over a full rotational cycle is nearly half that of similar products. The distance between the output shaft 9 and the base of the entire side-swing joint is relatively short. With the pelvis mounted, the robot's legs are more than one-tenth closer together than in previous side-swing joints using linear cylinders. This reduction in joint volume makes the robot more stable while standing and walking, improving its balance.

[0021] 4. The parallel-coupled hydraulically driven robot joint of the present invention improves the load-bearing capacity of the joint: it adopts a double-cylinder parallel arrangement to increase the width in the longitudinal direction, greatly increasing the bending strength and enabling stable bearing of the weight of the arms and legs.

[0022] 5. The parallel-coupled hydraulically driven robot joint of the present invention can achieve high-speed response and high-precision control of the joint: it adopts a hydraulic servo valve 15, an oil pressure sensor 16 and an angle encoder, and servo closed-loop control, which can sense the joint status in real time and control and adjust the oil pressure and flow, achieving precise control, convenient control, and ensuring position accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a structural diagram of a parallel-coupled hydraulically driven robot joint according to the present invention;

[0024] Figure 2 This is a front view of a parallel-coupled hydraulically driven robot joint according to the present invention;

[0025] Figure 3 It is a side view of a parallel coupled hydraulically driven robot joint of the present invention;

[0026] Figure 4 It is a top view of a parallel-coupled hydraulically driven robot joint of the present invention;

[0027] Figure 5 It is an axonometric view of a parallel-coupled hydraulically driven robot joint according to the present invention;

[0028] Figure 6 It is a longitudinal cross-sectional view of a parallel-coupled hydraulically driven robot joint of the present invention;

[0029] Figure 7 It is a transverse cross-sectional view of a parallel-coupled hydraulically driven robot joint of the present invention;

[0030] Figure 8 This is a schematic diagram of a parallel-coupled hydraulically driven robot joint according to the present invention.

[0031] In the figure: 1. Protective shell; 2. Rotating rod; 3. Transmission rod; 4. Piston sealing ring; 5. Piston; 6. Magnetic encoder flange; 7. Magnet; 8. Output bearing; 9. Output shaft; 10. Spline sleeve; 11. Fixed bearing; 12. Hydraulic cylinder; 13. Cylinder head sealing ring; 14. Bottom valve plate; 15. Hydraulic servo valve; 16. Oil pressure sensor. DETAILED DESCRIPTION

[0032] Specific implementation method 1: Combination Figures 1 to 7 Describe this embodiment. This embodiment is a parallel-coupled hydraulically driven robot joint, which includes a hydraulic cylinder 12, an output shaft 9, two spline sleeves 10, two rotating rods 2, two transmission rods 3 and two pistons 5. The hydraulic cylinder 12 is an upper and lower double-cylinder structure. The two pistons 5 are respectively slidably sealed and inserted in the upper cylinder and the lower cylinder of the hydraulic cylinder 12. One end of the two transmission rods 3 is rotatably connected to the two pistons 5 through two rotating shafts, and the other ends of the two transmission rods 3 are rotatably connected to the upper and lower ends of the two rotating rods 2 arranged side by side through two rotating shafts. The output shaft 9 is a spline shaft, and the middle parts of the two rotating rods 2 are respectively installed in the middle of the output shaft 9 through two spline sleeves. Two coaxially arranged cylinder sleeves are respectively provided on both sides of the front end of the hydraulic cylinder 12, and the two ends of the output shaft 9 are respectively rotatably connected to the two cylinder sleeves.

[0033] The rotating rod 2 and the output shaft 9 are connected via a spline, and the spline size is selected according to the standard DIN ISO 14 (1986-12).

[0034] The present invention utilizes a parallel-coupled hydraulically driven roll mechanism to achieve roll freedom for the robot's legs. By placing the roll mechanism outside the pelvis and slewing mechanism, this design optimizes the piping and transmission structure while also reducing the width of the entire pelvis. This improvement is expected to enhance the robot's overall motion performance, reducing its size and weight while ensuring efficient drive capability and facilitating subsequent motion control. Furthermore, the dual-cylinder arrangement increases the longitudinal width, significantly enhancing joint stiffness.

[0035] The present invention provides a dual-cylinder parallel-coupled robot joint structure, which enables the side-swing freedom of the robot's thighs and arms to be achieved without going through a complex transmission structure, thereby achieving functions such as movement flexibility, compact structure, high rigidity and large driving torque, overcoming the shortcomings of traditional humanoid robots such as small side-swing joint rotation angle, complex transmission, small movement driving force, and unstable movement. At the same time, the width of the robot's pelvis can be reduced, making the robot more balanced when standing and walking and easier to control.

[0036] Specific implementation method 2: Combination Figures 1 to 7This embodiment also includes a magnetic encoder flange 6 and a magnet 7. A magnet mounting hole is machined in the center of one end face of the output shaft 9, into which the magnet 7 is inserted. The magnetic encoder flange 6 is coaxially positioned to the side of the magnet 7 and connected to the corresponding end of the cylinder sleeve. This configuration includes an oil pressure sensor 16 installed in the oil circuit and a magnetic encoder mounted on the hydraulic cylinder 12. This multi-sensor integration enables system perception and feedback. Other components and connections are identical to those in the first embodiment.

[0037] Specific implementation method three: Combination Figures 1 to 7 This embodiment also includes two output bearings 8. The sides of the output shaft 9 are machined into cylindrical surfaces. The two ends of the output shaft 9 are rotatably connected to the two cylinder sleeves via the two output bearings 8. Other components and connection relationships are the same as those of the first or second embodiment.

[0038] Among them, the output bearing 8 is chamfered and other processing is performed.

[0039] Specific implementation method four: Combination Figures 1 to 7 This embodiment further includes two fixed bearings 11, which are respectively mounted on two cylinder sleeves. Other components and connection relationships are the same as those of the first, second or third embodiment.

[0040] Among them, the location where the fixed bearing 11 is installed is subjected to processing such as chamfering.

[0041] Specific implementation method five: Combination Figures 1 to 7 This embodiment further includes two piston sealing rings 4. Two first annular sealing grooves are machined circumferentially on the sides of the two pistons 5. The two piston sealing rings 4 are respectively sleeved within the two first annular sealing grooves. The two pistons 5 are slidably and sealingly engaged with the upper and lower cylinders of the hydraulic cylinder 12 via the two piston sealing rings 4. The remaining components and connections are the same as those in the first, second, third, or fourth embodiments.

[0042] Specific implementation method six: combination Figures 1 to 7 This embodiment further includes two cylinder heads and two cylinder head sealing rings 13. The rear ends of the upper and lower cylinder barrels of the hydraulic cylinder 12 are provided with an integrally formed annular cylinder seat. Two cylinder head mounting holes are machined into the annular cylinder seat, corresponding one-to-one with the upper and lower cylinder barrels, respectively. The two cylinder heads are coaxially mounted in the two cylinder head mounting holes. Two second annular sealing grooves are machined into the circumferential direction of the side surfaces of the two cylinder heads. The two cylinder head sealing rings 13 are respectively sleeved in the two second annular sealing grooves. The two cylinder heads are sealed with the annular cylinder seats via the two cylinder head sealing rings 13. Other components and connections are the same as those of the first, second, third, fourth, or fifth embodiments.

[0043] Specific implementation method seven: combination Figures 1 to 7 This embodiment also includes a bottom valve plate 14 and a hydraulic servo valve 15. The bottom valve plate 14 is mounted at the rear center of the annular cylinder base, and the hydraulic servo valve 15 is mounted at the rear end of the bottom valve plate 14. Two first oil passages are machined within the bottom valve plate 14, connecting the hydraulic servo valve 15 to the upper and lower cylinders of the hydraulic cylinder 12. With this arrangement, the hydraulic servo valve 15 is driven by a hydraulic controller to control the flow, speed, and direction of hydraulic oil flowing into the hydraulic cylinder. Other components and connections are identical to those of Embodiments 1, 2, 3, 4, 5, or 6.

[0044] Specific implementation method eight: combination Figures 1 to 7 This embodiment also includes two oil pressure sensors 16, one located on the upper and lower sides of the hydraulic servo valve 15. Both oil pressure sensors 16 are mounted on the rear end of the bottom valve plate 14. Two second oil circuits connect the two oil pressure sensors 16 to the upper and lower cylinders of the hydraulic cylinder 12 within the bottom valve plate 14. This arrangement, with the oil pressure sensors 16 installed in the joint oil circuits, enables control feedback and improves control accuracy. Other components and connections are identical to those in Specific Embodiments 1, 2, 3, 4, 5, 6, or 7.

[0045] Specific implementation method nine: Combination Figures 1 to 7 This embodiment also includes a protective housing 1, a semicircular shell, buckled onto the front end of the hydraulic cylinder 12. The center portion of each side of the housing is machined with a clearance groove that mates with the two cylinder sleeves. This arrangement shields the transmission components within the housing, providing dust protection and safeguarding the internal components. The remaining components and connections are identical to those of Embodiments 1, 2, 3, 4, 5, 6, 7, or 8.

[0046] Specific implementation method ten: Combination Figures 1 to 7 In this embodiment, the hydraulic cylinder 12 is made of titanium alloy using 3D printing technology. Other components and connections are the same as those of the first, second, third, fourth, fifth, sixth, seventh, eighth, or ninth embodiment.

[0047] Finite element analysis was performed on the hydraulic cylinder 12 to effectively improve its rigidity and stability. Through continuous iteration under the constraints of force and design space, the structure of the hydraulic cylinder 12 model was determined, and reinforcing ribs were added to areas of concentrated force. The hydraulic cylinder 12 was 3D printed using high-performance titanium alloy. After printing, the frame was shot peened to enhance surface properties. Finishing was then performed to complete the machining of various surfaces and holes, eliminating the need for process oil lines and minimizing space and weight.

[0048] How it works

[0049] Combine Figures 1 to 8 The working principle of the parallel coupled hydraulically driven robot joint of the present invention is described as follows: the pistons 5 in the upper and lower cylinders arranged side by side are connected to the rotating rod 2 through the transmission rod 3 respectively, the middle part of the rotating rod 2 is connected to the output shaft 9 through a spline, and the two ends of the output shaft 9 are rotatably connected to the two cylinder sleeves of the hydraulic cylinder 12 through the output bearing 8, which can transmit torque outward. During operation, the hydraulic oil enters the upper and lower cylinders of the hydraulic cylinder 12 under the control of the hydraulic servo valve 15, thereby pushing the piston 5 to move. The hydraulic cylinder displacement and pressure and other information are sensed through the oil pressure sensor 16 on the joint. The front end of the piston 5 is connected to the transmission rod 3 through a rotating shaft. The transmission rod 3 pushes the rotating rod 2 to rotate around the output shaft 9 in the center. The rotating rod 2 and the output shaft 9 transmit torque through the spline. When the hydraulic oil in the upper cylinder pushes the piston 5 to move outward and the piston 5 in the lower cylinder moves inward, the thigh swings toward the inside of the body; when the hydraulic oil in the lower cylinder pushes the piston 5 to move outward and the piston 5 in the upper cylinder moves inward, the thigh swings toward the outside of the body.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A parallel-coupled hydraulically driven robot joint, characterized in that: It comprises a hydraulic cylinder (12), an output shaft (9), two spline sleeves (10), two rotating rods (2), two transmission rods (3) and two pistons (5). The hydraulic cylinder (12) is an upper and lower double cylinder structure. The two pistons (5) are respectively slidably sealed and inserted in the upper cylinder and the lower cylinder of the hydraulic cylinder (12). One end of the two transmission rods (3) is respectively connected to the two pistons (5) through two rotating shafts. The other ends of the two transmission rods (3) are respectively connected to the upper and lower ends of the two rotating rods (2) arranged side by side through two rotating shafts. The output shaft (9) is a spline shaft. The middle parts of the two rotating rods (2) are respectively installed in the middle part of the output shaft (9) through two spline sleeves. Two cylinder sleeves arranged coaxially are respectively provided on both sides of the front end of the hydraulic cylinder (12). The two ends of the output shaft (9) are respectively connected to the two cylinder sleeves. It also includes two piston sealing rings (4), the side surfaces of the two pistons (5) are respectively machined with first annular sealing grooves along the circumferential direction, the two piston sealing rings (4) are respectively sleeved in the two first annular sealing grooves, and the two pistons (5) are respectively slidably sealed with the upper cylinder barrel and the lower cylinder barrel of the hydraulic cylinder barrel (12) through the two piston sealing rings (4); It also includes two cylinder heads and two cylinder head sealing rings (13). The rear ends of the upper cylinder and the lower cylinder of the hydraulic cylinder (12) are provided with an integrally formed annular cylinder seat. Two cylinder head mounting holes are processed on the annular cylinder seat. The two cylinder head mounting holes correspond to the upper cylinder and the lower cylinder respectively. The two cylinder heads are coaxially mounted in the two cylinder head mounting holes. The sides of the two cylinder heads are respectively processed with second annular sealing grooves along the circumferential direction. The two cylinder head sealing rings (13) are respectively sleeved in the two second annular sealing grooves. The two cylinder heads are respectively sealed with the annular cylinder seat through the two cylinder head sealing rings (13). It also includes a bottom valve plate (14) and a hydraulic servo valve (15), the bottom valve plate (14) is mounted at the rear end center of the annular cylinder seat, the hydraulic servo valve (15) is mounted at the rear end of the bottom valve plate (14), and two first oil paths connecting the hydraulic servo valve (15) and the upper cylinder barrel and the lower cylinder barrel of the hydraulic cylinder barrel (12) are processed inside the bottom valve plate (14); It also includes two oil pressure sensors (16), the oil pressure sensors (16) are respectively provided on the upper and lower sides of the hydraulic servo valve (15), the two oil pressure sensors (16) are both installed at the rear end of the bottom valve plate (14), and the bottom valve plate (14) is provided with two second oil circuits connecting the two oil pressure sensors (16) and the upper cylinder barrel and the lower cylinder barrel of the hydraulic cylinder barrel (12).

2. The parallel-coupled hydraulically driven robot joint according to claim 1, characterized in that: It also includes a magnetic encoder flange (6) and a magnet (7). A magnet mounting hole is machined at the center of the end face of one side of the output shaft (9). The magnet (7) is inserted into the magnet mounting hole. The magnetic encoder flange (6) is coaxially arranged on the side of the magnet (7). The magnetic encoder flange (6) is connected to the corresponding cylinder shaft sleeve end.

3. The parallel-coupled hydraulically driven robot joint according to claim 2, characterized in that: It also includes two output bearings (8), and the side surfaces of both ends of the output shaft (9) are processed into cylindrical surfaces. The two ends of the output shaft (9) are respectively connected to the two cylinder sleeves through the two output bearings (8).

4. The parallel-coupled hydraulically driven robot joint according to claim 3, characterized in that: It also includes two fixed bearings (11), which are respectively sleeved on the two cylinder shaft sleeves.

5. The parallel-coupled hydraulically driven robot joint according to claim 1, characterized in that: It also includes a protective shell (1), which is a semicircular shell. The protective shell (1) is buckled on the front end of the hydraulic cylinder (12), and the middle of both sides of the protective shell (1) are processed with avoidance grooves matching the two cylinder shaft sleeves.

6. The parallel-coupled hydraulically driven robot joint according to claim 5, characterized in that: The hydraulic cylinder (12) is made of titanium alloy using 3D printing technology.

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