A distributed KHV type involute small tooth difference joint module

Abstract

The present invention discloses a distributed K-H-V type involute small tooth difference joint module, which is applied to the joints of a serpentine robot arm. The joint module is composed of three sets of rotary drive units, a frame, an internal gear, and an external gear. During the transmission process, the eccentric shaft rotates to drive the internal gear to output a rotational speed, while the external gear moves horizontally. The three sets of rotary drive units are respectively installed in through holes that are equally spaced between the internal gear and the external gear. The rotary drive units use a small motor in conjunction with bearings, external gears, and internal gears, which improves the space utilization of the joint module. In addition, by reducing the number of transmission links, the power loss of the joint module is reduced, so that the joint module has the characteristics of high rigidity and large transmission ratio of the involute small tooth difference planetary gear transmission, while also having the characteristics of small size and high output efficiency.

Description

Technical Field

[0001] The present invention relates to an improvement of a joint module used on a snake-like robotic arm, and more particularly, to a distributed KHV-type involute small-tooth-difference joint module. Background Art

[0002] In the 1920s, Petr Miturich first proposed the concept of a snake-like robotic arm. He believed that mechanical devices could simulate the movement of snakes to achieve more efficient motion gaits, such as spring motion, sinusoidal motion, and lateral rotation. Although the snake-like robotic arm was designed relatively early, it was limited by the weak motion model theory used for motion planning at the time. Until the 1980s, the coordinated control of the snake-like arm's morphology remained a difficult problem. With the gradual improvement of the theory, the snake-like robotic arm entered a period of rapid development after the 1990s. Due to its high degree of freedom, flexible movement, and large aspect ratio, it is suitable for various narrow, complex, deep cavities, and sealed environments. It has gradually been applied to assembly, manufacturing, surveying and maintenance in the aerospace and nuclear power plant fields; active endoscopes, various types of minimally invasive surgery, and controllable needle technology in the medical field.

[0003] Joint modules are highly integrated, modular joints with a unified design. They enable relative motion between various robot components, enabling rapid realization of robot functionality and practical applications. Joint modules are commonly used for cable-driven snake-like robotic arms and joint actuation in humanoid and quadruped robots.

[0004] At present, joint modules can be roughly divided into two categories. One is cylindrical and mostly uses a hollow torque motor plus a harmonic reducer. Its overall length and size are large, and the harmonic reducer is expensive, has poor rigidity, is not impact-resistant, and has low transmission efficiency. It is not suitable for the leg joints of quadruped and humanoid robots; the other is disc-shaped and mostly uses a hollow torque motor plus a planetary reducer. Its appearance is more suitable for leg joints, but the planetary reducer is inside the motor, its transmission is relatively small, and the planetary gear transmission has backlash and low precision.

[0005] When the output of a serpentine manipulator drive unit is rotational motion, harmonic or planetary reducers are often used to increase torque. Further research has revealed that involute gearing with small tooth difference is also suitable for serpentine manipulator drives, particularly the 2K-H and KHV types, due to its high transmission ratio, compact structure, reliable operation, and high overload and shock resistance. Therefore, research on involute gearing with small tooth difference has practical significance for serpentine manipulator drives.

[0006] A small tooth difference refers to a KHV-type planetary gear transmission consisting of a pair of involute internal gears with a small tooth difference, typically 1 to 4. This transmission consists of a sun gear (internal gear K), a planet carrier (eccentric shaft H), and a specialized output mechanism V. It is named KHV for its basic components and N for its meshing method, with N denoting internal meshing. Another type of planetary transmission with a small tooth difference is the 2K-H type, a double internal meshing, double internal gear pair NN type. Its basic components are two sun gears K and a planet carrier (eccentric shaft H). Summary of the Invention

[0007] In order to realize the requirements of the serpentine robot arm for the large torque, high precision and small volume of the joint module, as well as the requirement for the flattening of the joint module, the present invention adopts an involute small tooth difference planetary gear transmission as a reducer, which has a large transmission ratio. On the basis of the traditional KHV type, a configuration innovation is carried out to design a distributed KHV type transmission, and three small motors are used to replace a large motor, and the three small motors are distributed in the middle of the outer gear, so that the joint module structure space utilization rate is higher, and the multi-stage transmission link is reduced, the first-level sliding friction is converted into rolling friction, and the transmission efficiency is improved. The present invention designs a distributed KHV type involute small tooth difference joint module with a small volume, disc shape, high rigidity, high precision and large transmission ratio through an innovative transmission method and an integrated design of the motor and transmission system.

[0008] The present invention designs a distributed KHV-type involute small-tooth-difference joint module applied to a serpentine robot arm, comprising a first rotary drive unit (1), a second rotary drive unit (2), a third rotary drive unit (3), an internal gear (4), a frame (5), a uniform-section thin-walled bearing (6), a first gear cover (41), a second gear cover (61), a first external gear (7), and a second external gear (8);

[0009] Wherein, the first rotation drive unit (1), the second rotation drive unit (2) and the third rotation drive unit (3) have the same structure;

[0010] Wherein, the first gear cover (41) and the second gear cover (61) have the same structure;

[0011] The first external gear (7) and the second external gear (8) have the same structure; the GA panel (71) of the first external gear (7) is provided with a stepped through hole for placing a bearing, and the GB panel (72) of the first external gear (7) is a smooth surface;

[0012] The D-axis center hole (41F) of the first gear cover (41), the G-axis center hole (7E) of the first external gear (7), the H-axis center hole (8E) of the second external gear (8), and the F-axis center hole (61F) of the second gear cover (61) are aligned and kept coaxial;

[0013] wherein the frame (5) and the internal gear (4) remain coaxial;

[0014] The first rotary drive unit (1) comprises a DC brushless motor A (1A), an eccentric shaft cover plate A (1B), an AA deep groove ball bearing (1C), an AB deep groove ball bearing (1D), an A reverse retaining spring (1E), an eccentric shaft A (1F), and an A shaft ring (1G); the motor output shaft (1A1) of the motor (1A) sequentially passes through the AB center through hole (1F1) of the A eccentric shaft (1F), the AA center through hole (1F1) of the A eccentric shaft cover plate (1B), and the AA center through hole (1F2) of the A eccentric shaft cover plate (1B). hole (1B1); the A eccentric shaft (1F) and the A eccentric shaft cover (1B) are fixed to the front end cover of the motor (1A) by screws; the AA deep groove ball bearing (1C) is installed on the AA shaft section (1F7) of the A eccentric shaft (1F), the AB deep groove ball bearing (1D) is installed on the AB shaft section (1F8), the A shaft ring (1G) is installed on the AC shaft section (1F9), and the A reverse retaining ring (1E) is installed on the retaining groove (1F10);

[0015] The inner ring surface of the internal gear (4) is provided with D inner teeth (4A), D inner convex ring (4C) and D bearing section (4B) in sequence; the D inner convex ring (4C) is used to block and limit the movement of the uniform cross-section thin-walled bearing (6) in the vertical direction; the outer ring of the uniform cross-section thin-walled bearing (6) is connected to the D bearing section (4B) of the internal gear (4), and the inner ring of the uniform cross-section thin-walled bearing (6) is connected to the E bearing section (5F) of the frame (5); the D inner teeth (4A) of the internal gear (4) are used to mesh with the G outer teeth (7D) on the first external gear (7) and the H outer teeth (8D) on the second external gear (8);

[0016] The joint module uses two external gears (7, 8) with the same structure and is placed symmetrically relative to the central axis of the internal gear (4). When moving, the eccentricities are equal in size and opposite in direction, and cancel each other out.

[0017] Compared with the existing KHV type (pin type) joint module technology, the advantages of the distributed KHV type involute small tooth difference joint module of the present invention are:

[0018] (1) Structural volume: The distributed KHV reduces the multi-stage transmission links including sliding friction. The compact structure is smaller in volume. The motor is inside the gear, which effectively utilizes the space. The number of parts in the structure is smaller, the structure is simpler, and the processing and assembly are more convenient.

[0019] (2) Transmission ratio. Calculated using the transmission ratio formula, the transmission ratio is related to the number of teeth on the outer gear and the difference in the number of teeth between the inner and outer gears. The difference in the number of teeth has a greater impact; the smaller the difference in the number of teeth, the larger the transmission ratio. The calculation results show that the distributed KHV has a large transmission ratio. Due to the large transmission ratio, the motor can maintain a high speed, the transmission efficiency is higher, and the output power is greater. Using a single-stage transmission, a transmission ratio of 100 or even higher can be achieved; using a three-stage transmission, a transmission ratio of over 10,000 can be achieved.

[0020] (3) The distributed KHV mechanism has no high pairs and no sliding friction except for gear meshing, resulting in lower power loss than the KHV type (pin-type). It has high redundancy, and the joint module has 1 degree of freedom. Only one power source is required to control the movement of the mechanism.

[0021] (4) The power source can be split and evenly arranged in the equally divided holes of the external gear, which can make full use of the space and make the overall size of the joint module smaller. The use of this distributed KHV structure flattening makes the drive not only suitable for the drive of snake-like robotic arms, but also for the joints of humanoid and quadruped robots, and the application scenarios are richer.

[0022] (5) Involute gear transmission has lower processing cost than cycloid pinwheel, and can be processed in batches using traditional gear processing methods.

[0023] (6) High reliability. The three motors are quasi-parallel output. However, as long as one motor is operating normally, the entire system can output at the original speed, and the output torque will decrease. The power limit is higher. The torque of the power sources evenly distributed in the equally divided holes of the external gear can be accumulated together, but the synchronization requirements of each power source are high. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural diagram of the distributed KHV type involute small tooth difference joint module of the present invention.

[0025] Figure 1A This is another perspective structural diagram of the distributed KHV type involute small tooth difference joint module of the present invention.

[0026] Figure 1B It is a cross-sectional structural diagram of the distributed KHV type involute small tooth difference joint module of the present invention.

[0027] Figure 1C This is a cross-sectional structural diagram from another perspective of the distributed KHV type involute small tooth difference joint module of the present invention.

[0028] Figure 1D This is an exploded view of the distributed KHV type involute small tooth difference joint module of the present invention.

[0029] Figure 2 It is a cross-sectional structural diagram of the first rotary drive unit in the distributed KHV type involute small tooth difference joint module of the present invention.

[0030] Figure 2A It is an exploded view of the first rotary drive unit of the present invention.

[0031] Figure 2B It is a structural diagram of the eccentric sleeve in the first rotary drive unit of the present invention.

[0032] Figure 2C It is a stress cloud diagram of the eccentric shaft in the first rotation drive unit of the present invention.

[0033] Figure 2D It is a cross-sectional view of the assembly of the first rotary drive unit and the external gear of the present invention.

[0034] Figure 3 It is an exploded view of the second rotation drive unit of the present invention.

[0035] Figure 4 It is an exploded view of the third rotation drive unit of the present invention.

[0036] Figure 5 It is a structural diagram of the internal gear of the present invention.

[0037] Figure 5A It is a cross-sectional view of the assembly of the internal gear, the external gear and the first rotation drive unit of the present invention.

[0038] Figure 6 It is a structural diagram of the frame of the present invention.

[0039] Figure 6A It is another perspective structural diagram of the frame of the present invention.

[0040] Figure 7 It is a structural diagram of the first gear cover of the present invention.

[0041] Figure 7A This is a structural diagram of the first gear cover from another perspective of the present invention.

[0042] Figure 8 It is a structural diagram of the first external gear of the present invention.

[0043] Figure 8A This is a structural diagram of the first external gear from another perspective of the present invention.

[0044] Figure 9 is the maximum bending stress of the gear under different torques with different numbers of external gears.

[0045] Figure 10 This is the angular velocity curve of the internal gear when using dual external gears in the distributed KHV type involute small tooth difference joint module of the present invention.

[0046] Figure 11 These are the stress cloud diagram and deformation cloud diagram of the gears under different loads of the distributed KHV type involute small tooth difference joint module of the present invention.

[0047]

[0048] DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below with reference to the accompanying drawings. The parameters listed are merely exemplary embodiments of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

[0050] See also Figure 1 、 Figure 1A 、 Figure 1B 、 Figure 1C 、 Figure 1D As shown, the present invention designs a distributed KHV type involute small tooth difference joint module for use on a serpentine robotic arm, which includes a first rotation drive unit 1, a second rotation drive unit 2, a third rotation drive unit 3, an internal gear 4, a frame 5, a uniform cross-section thin-walled bearing 6, a first gear cover 41, a second gear cover 61, a first external gear 7, and a second external gear 8.

[0051] The first rotation drive unit 1 , the second rotation drive unit 2 and the third rotation drive unit 3 have the same structure.

[0052] The first gear cover 41 and the second gear cover 61 have the same structure. The first external gear 7 and the second external gear 8 have the same structure. The D-axis center hole 41F of the first gear cover 41, the G-axis center hole 7E of the first external gear 7, the H-axis center hole 8E of the second external gear 8 and the F-axis center hole 61F of the second gear cover 61 are aligned and kept coaxial. Figure 1C shown.

[0053] The frame 5 and the internal gear 4 are kept coaxial, so that the internal gear 4 can only perform circular motion around the central axis of the center hole (41F). The assembly positions of the three rotary drive units (1, 2, 3) are constrained by the frame 5. The two eccentric shaft segments on the eccentric shaft sleeve of each rotary drive unit are coaxial with the three equally divided circular holes of the external gears (7, 8), constraining the movement of the external gears (7, 8).

[0054] To reduce the overall volume of the joint module in the serpentine robotic arm, the lower end of the internal gear 4 and the frame 5 are matched by a uniform cross-section thin-walled bearing 6 to achieve translation. The preferred dimensions of the uniform cross-section thin-walled bearing 6 are an inner ring of 66.2mm, an outer ring of 88.9mm, and a thickness of 6.35mm. The uniform cross-section thin-walled bearing 6 is a bearing with a special cross-sectional width and thickness; the same cross-sectional dimensions can match many different bearing inner diameters; the width and thickness of a standard bearing increase proportionally with the increase in the bearing inner diameter, while the uniform cross-sectional thin-walled bearing 6 increases the inner diameter while maintaining the cross-sectional dimensions unchanged. Therefore, when the bearing diameter is large, the use of a uniform cross-sectional thin-walled bearing 6 can significantly reduce the overall volume of the structure. The internal gear 4, which serves as the output of the joint module, has a threaded hole on its upper end face for connecting the output actuator, and a threaded hole on the lower end face for fixing the internal gear bearing cover 42. The design of the internal gear bearing cover 42 helps prevent the uniform cross-sectional thin-walled bearing 6 from falling off.

[0055] The present invention designs a distributed KHV-type involute small-tooth-difference joint module. In its optimized structural design, it employs multiple eccentric shaft inputs (i.e., the eccentric shafts in the rotary drive unit), with the external gear 4 performing translational motion and the internal gears (7, 8) rotating as output. The distributed KHV-type transmission adopts a planetary gear transmission. During the motor-driven transmission process of the joint module, the eccentric shafts rotate, driving the internal gears (7, 8) as the speed output, while the external gear 4 translates.

[0056] To meet the serpentine robot arm's requirements for distributed KHV-type involute small-tooth-difference joint modules, all components, except the motor, can be made of steel, aluminum alloy, or resin. 3D printing is also possible if miniaturization is achieved.

[0057] First rotary drive unit 1

[0058] See also Figure 2 、 Figure 2A The cross-sectional structure and exploded view of the first rotary drive unit 1 are shown. The first rotary drive unit 1 includes a DC brushless motor A 1A, an eccentric shaft cover A 1B, an AA deep groove ball bearing 1C, an AB deep groove ball bearing 1D, an A reverse retaining spring 1E, an A eccentric shaft 1F and an A shaft ring 1G.

[0059] like Figure 2A As shown, eccentric shaft cover A 1B has an AA center through-hole 1B1 at its center. Surrounding AA center through-hole 1B1 are AA countersunk holes 1B2, AB countersunk holes 1B3, and AC countersunk holes 1B4. AA center through-hole 1B1 is used for the motor output shaft 1A1 of brushless DC motor A 1A to pass through.

[0060] like Figure 2 、 Figure 2AAs shown, the center of the front panel 1F5 of the eccentric shaft A 1F is provided with an AB center through hole 1F1, and the AB center through hole 1F1 is surrounded by AA through holes 1F2, AB through holes 1F3, and AC through holes 1F4. The AB center through hole 1F1 is used for the motor output shaft 1A1 of the DC brushless motor A 1A to pass through. That is, the motor output shaft 1A1 of the DC brushless motor A 1A passes through the AB center through hole 1F1 of the front panel 1F5 and the AA center through hole 1B1 of the eccentric shaft cover 1B in sequence. The DC brushless motor A 1A is placed in the cavity 1F6 of the eccentric shaft A 1F (as shown in FIG. Figure 2B As shown), and by cooperating with the screws and the threaded holes, the A brushless DC motor 1A is fixed on the A eccentric shaft cover 1B.

[0061] like Figure 2 、 Figure 2A As shown, the exterior of eccentric shaft A 1F is sequentially provided with an AA shaft segment 1F7, an AB shaft segment 1F8, an AC shaft segment 1F9, and a retaining groove 1F10. An AA deep groove ball bearing 1C is mounted on AA shaft segment 1F7. An AB deep groove ball bearing 1D is mounted on AB shaft segment 1F8. An A shaft ring 1G is mounted on AC shaft segment 1F9. An A reverse retaining spring 1E is mounted on retaining groove 1F10.

[0062] like Figure 2 As shown, the motor output shaft 1A1 of the motor 1A sequentially passes through the AB center through-hole 1F1 of the A eccentric shaft 1F and the AA center through-hole 1B1 of the A eccentric shaft cover 1B. The A eccentric shaft 1F and the A eccentric shaft cover 1B are fixed to the front end cover of the motor 1A by screws. The AA deep groove ball bearing 1C is installed on the AA shaft section 1F7 of the A eccentric shaft 1F, the AB deep groove ball bearing 1D is installed on the AB shaft section 1F8, the A shaft ring 1G is installed on the AC shaft section 1F9, and the A reverse retaining spring 1E is installed on the retaining groove 1F10. The rear end cover of the motor 1A is fixed to the frame 5.

[0063] Second rotary drive unit 2

[0064] See also Figure 3 The exploded structure diagram of the second rotation drive unit 2 is shown, and the second rotation drive unit 2 includes a B brushless DC motor 2A, a B eccentric shaft cover 2B, a BA deep groove ball bearing 2C, a BB deep groove ball bearing 2D, a B reverse retaining spring 2E, a B eccentric shaft 2F and a B shaft ring 2G.

[0065] A BA center through hole 2B1 is formed at the center of the B eccentric shaft cover 2B. Surrounding the BA center through hole 2B1 are BA countersunk holes 2B2, BB countersunk holes 2B3, and BC countersunk holes 2B4. The BA center through hole 2B1 is used for the motor output shaft 2A1 of the B brushless DC motor 2A to pass through.

[0066] The front panel 2F5 of the B eccentric shaft 2F has a central through-hole 2F1 (BB), surrounded by three holes: 2F2, 2F3, and 2F4. The output shaft 2A1 of the B brushless DC motor 2A passes through the central through-hole 2F1. Specifically, the output shaft 2A1 of the B brushless DC motor 2A passes through the central through-hole 2F1 of the front panel 2F5 and the central through-hole 21B1 of the B eccentric shaft cover 2B. The B brushless DC motor 2A is positioned within the cavity of the B eccentric shaft 2F and secured to the B eccentric shaft cover 2B via screws engaging threaded holes.

[0067] The exterior of eccentric shaft B 2F is equipped with, in sequence, BA shaft segment 2F7, BB shaft segment 2F8, BC shaft segment 2F9, and retaining groove 2F10. BA deep groove ball bearing 2C is mounted on BA shaft segment 2F7. BB deep groove ball bearing 2D is mounted on BB shaft segment 2F8. B shaft ring 2G is mounted on BC shaft segment 2F9. Reverse retaining spring 2E is mounted on retaining groove 2F10.

[0068] The third rotary drive unit 3

[0069] See also Figure 4 The exploded structure diagram of the third rotation drive unit 3 is shown, and the third rotation drive unit 3 includes a C brushless DC motor 3A, a C eccentric shaft cover 3B, a CA deep groove ball bearing 3C, a CB deep groove ball bearing 3D, a C reverse retaining spring 3E, a C eccentric shaft 3F and a C shaft ring 3G.

[0070] A CA center hole 3B1 is formed at the center of the C eccentric shaft cover 3B. Surrounding CA center hole 3B1 are CA countersunk holes 3B2, CB countersunk holes 3B3, and CC countersunk holes 3B4. CA center hole 3B1 is used for the motor output shaft 3A1 of the C brushless DC motor 3A to pass through.

[0071] A central through-hole 3F1 (CB) is defined at the center of the front panel 3F5 of the C-eccentric shaft 3F. Surrounding this through-hole are three CA through-holes 3F2, 3F3, and 3F4. The motor output shaft 3A1 of the C-brushless DC motor 3A passes through the central through-hole 3F1 (CB). Specifically, the motor output shaft 3A1 of the C-brushless DC motor 3A passes sequentially through the central through-hole 3F1 (CB) of the front panel 3F5 and the central through-hole 31B1 (CA) of the C-eccentric shaft cover 3B. The C-brushless DC motor 3A is positioned within the cavity of the C-eccentric shaft 3F and secured to the C-eccentric shaft cover 3B via screws engaging threaded holes.

[0072] The exterior of C eccentric shaft 3F is sequentially equipped with a CA shaft segment 3F7, a CB shaft segment 3F8, a CC shaft segment 3F9, and a retaining groove 3F10. A CA deep groove ball bearing 3C is mounted on CA shaft segment 3F7. A CB deep groove ball bearing 3D is mounted on CB shaft segment 3F8. A C shaft ring 3G is mounted on CC shaft segment 3F9. A C reverse retaining spring 3E is mounted on retaining groove 3F10.

[0073] The three rotary drive units in the distributed KHV-type involute small-tooth-difference joint module designed in this invention utilize brushless DC motors (1A, 2A, and 3A), preferably a 2008 model aircraft model small motor. The motor rotor shaft end is inlaid with a radially magnetized ring. Calculation of eccentric shaft torque indicates a maximum output torque of 0.085 N·m. The motor parameters are shown in Table 1.

[0074] Table 1 Model aircraft motor parameters

[0075] Stator outer diameter 20mm No-load current 0.33A / 10V stator thickness 8mm Phase resistance 379.3mΩ Number of stator slots 12 Maximum current 8.9A Number of rotor poles 14 Maximum power 112.14W Speed ​​constant 1000rpm / V Rated voltage 12.6V weight 27.08g Motor size 23.8×18.9mm

[0076] The maximum load driven by the three motors in the distributed KHV-type involute small-tooth-difference joint module designed in this invention is 6.30 N·m. The maximum load when all three motors are driven simultaneously is 18.9 N·m. The maximum speed of each motor is 137.0 rpm.

[0077] In the rotary drive unit with an eccentric shaft system designed by the present invention, the eccentric shafts (1F, 2F, 3F) are the active rotating shafts. In order to make the structure more compact and ensure the torsional strength of the eccentric shafts, the eccentric shafts are designed as hollow shaft sleeves. The motor is placed in the cavity of the eccentric shafts. One end of the eccentric shaft is closed (i.e., the front panel) and has three through holes for connecting with the motor rotor. Figure 2A 、 Figure 3 、 Figure 4 shown.

[0078] The present invention uses Abaqus software to perform verification simulation on the eccentric shaft. When the load of the rotary drive unit is 200N, a single motor is used for driving, the input torque of the eccentric shaft is 2.7N·m, the torque is applied to the cylindrical inner surface of the eccentric shaft, and the two deep groove ball bearings are fixed to the bearing section of the cylindrical outer surface of the eccentric shaft, the stress cloud diagram is as follows: Figure 2C As shown in the figure, the maximum stress of the eccentric shaft is less than the yield stress, which meets the use requirements.

[0079] The 6706 model deep groove ball bearing is used between the eccentric shaft and the external gear equal hole to reduce the rotational friction. The two bearings on the eccentric shaft are axially positioned by the end cover plus bolts and the shaft ring plus shaft retaining spring. The bolts are also used to fix the motor rotor to the eccentric shaft. The assembly drawing and exploded view of the eccentric shaft system are shown as follows: Figure 2 、 Figure 2Ashown.

[0080] In the rotary drive unit with an eccentric shaft system designed in the present invention, a motor drives the eccentric shaft to rotate, and the deep groove ball bearing installed on the eccentric shaft realizes the rotation of the outer gear (7, 8) relative to the inner gear (4), and the frame 5 also rotates relative to the inner gear (4).

[0081] Internal gear 4

[0082] like Figure 1D 、 Figure 5 、 Figure 5A As shown, the inner ring surface of the internal gear 4 is sequentially provided with D internal teeth 4A, D inner convex ring 4C, and D bearing segment 4B. The D inner convex ring 4C is used to block and limit the vertical movement of the uniform cross-section thin-walled bearing 6. In other words, the upper end face of the outer ring of the uniform cross-section thin-walled bearing 6 is pressed by the lower end face of the D inner convex ring 4C, while the lower end face of the outer ring of the uniform cross-section thin-walled bearing 6 is pressed by the upper end face of the internal gear bearing cover 42. The outer ring of the uniform cross-section thin-walled bearing 6 is connected to the D bearing segment 4B of the internal gear 4, and the inner ring of the uniform cross-section thin-walled bearing 6 is connected to the E bearing segment 5F of the frame 5, as shown in FIG. Figure 5A shown.

[0083] The D internal teeth 4A of the internal gear 4 are used to mesh with the G external teeth 7D on the first external gear 7 and the H external teeth 8D on the second external gear 8 (as shown in FIG. Figure 1B 、 Figure 1C 、 Figure 5A The D bearing section 4B of the internal gear 4 is sleeved with a uniform cross-section thin-walled bearing 6 (as shown). Figure 1B 、 Figure 1C 、 Figure 5A As shown), the outer ring of the uniform cross-section thin-walled bearing 6 is connected to the bearing segment 4B of the internal gear 4, and the inner ring of the uniform cross-section thin-walled bearing 6 is connected to the E bearing segment 5F of the frame 5, which is conducive to the movement of the distributed KHV type middle mechanism relative to the internal gear 4.

[0084] Rack 5

[0085] See also Figure 1A 、 Figure 1B 、 Figure 1C 、 Figure 1D 、 Figure 5A 、 Figure 6 、 Figure 6AAs shown, the bottom panel 5D of the frame 5 is provided with an EA through hole 5D1, an EB through hole 5D2, an EC through hole 5D3 and an E wiring hole 5E for wiring (at least for the three-phase wires of the motor to pass through). One end of the bottom panel 5D of the frame 5 is provided with an EA inner boss 5A, an EB inner boss 5B, and an EC inner boss 5C; the other end of the bottom panel 5D is provided with an EA base 5A1 at a position corresponding to the EA inner boss 5A, an EB base 5B1 at a position corresponding to the EB inner boss 5B, and an EC base 5C1 at a position corresponding to the EC inner boss 5C. An E bearing segment 5F and an E outer ring 5G are provided on the outer cylindrical surface of the frame 5. The inner ring of a uniform cross-section thin-walled bearing 6 is connected to the E bearing segment 5F. The upper end face of the inner ring of the uniform cross-section thin-walled bearing 6 is pressed by the bearing inner ring baffle 62, and the lower end face of the inner ring of the uniform cross-section thin-walled bearing 6 is pressed by the upper end face of the E outer ring 5G of the frame 5, as shown in FIG. Figure 5A shown.

[0086] exist Figure 1D In the embodiment, the three inner bosses (5A, 5B, 5C) on the frame 5 are aligned with the three inner bosses (62A, 62B, 62C) on the bearing inner ring baffle 62 and fixed by screws, so that the bearing inner ring baffle 62 is fixed to the frame 5, as shown in FIG. Figure 5A shown.

[0087] The motor stator of the brushless DC motor 1A in the first rotation drive unit 1 is mounted at the EA through hole 5D1 .

[0088] The motor stator of the B brushless DC motor 2A in the second rotation drive unit 2 is mounted at the EB through hole 5D2 .

[0089] The motor stator of the C brushless DC motor 3A in the third rotation drive unit 3 is mounted at the EC through hole 5D3 .

[0090] In the present invention, the E-bearing segment 5F on the outer cylindrical surface of the frame 5 is used to axially fix the inner ring of the uniform cross-section thin-walled bearing 6. The E-bearing segment 5F on the outer cylindrical surface of the frame 5 and the E-outer ring 5G form a stepped shaft, which also takes into account the design requirements of the miniaturized structure of the frame 5.

[0091] In the present invention, a structural design of three bases (EA base 5A1, EB base 5B1, EC base 5C1) is designed at the bottom of the frame 5. On the one hand, this can reduce the vibration of the rotation drive unit (1, 2, 3) during operation, and on the other hand, it is also convenient for fixing the distributed KHV type involute small tooth difference joint module of the present invention to the platform in the application scenario.

[0092] First gear cover 41

[0093] In the present invention, the first gear cover 41 and the second gear cover 61 have the same structure, but are assembled relative to each other. Figure 1B 、 Figure 1C 、 Figure 2D 、 Figure 5A shown.

[0094] like Figure 7 、 Figure 7A As shown, a D center hole 41F is provided at the center of the first gear cover 41, and then a DA through hole 41A, a DB through hole 41B, and a DC through hole 41C are provided in three equal parts.

[0095] The DA through hole 41A is used to place the first rotation drive unit 1. The DB through hole 41B is used to place the second rotation drive unit 2. The DC through hole 41C is used to place the third rotation drive unit 3.

[0096] The DB panel 41E of the first gear cover 41 is provided with a DA convex ring 41A1, a DB convex ring 41B1, and a DC convex ring 41C1. DA convex ring 41A1 is located at DA through-hole 41A, DB convex ring 41B1 is located at DB through-hole 41B, and DC convex ring 41C1 is located at DC through-hole 41C. The convex rings at the through-holes are used to press against the outer ring of the bearing.

[0097] The DA panel 41D of the first gear cover 41 is provided with a D-counter countersunk through hole 41D1 for a screw to pass through.

[0098] The DA outer convex ring 41A1 is used to press the upper end surface of the outer ring of the AA deep groove ball bearing 1C in the first rotation drive unit 1 .

[0099] The DB outer convex ring 41B1 is used to press the upper end surface of the outer ring of the BA deep groove ball bearing 2C in the second rotation drive unit 2 .

[0100] The DC outer convex ring 41C1 is used to press the upper end surface of the outer ring of the CA deep groove ball bearing 3C in the third rotation drive unit 3 .

[0101] Second gear cover 61

[0102] The second gear cover 61 has an F center hole 61F at its center, and is divided into three equal parts into FA through holes 61A, FB through holes 61B, and FC through holes 61C.

[0103] The FA through hole 61A is used to place the first rotation drive unit 1. The FB through hole 61B is used to place the second rotation drive unit 2. The FC through hole 61C is used to place the third rotation drive unit 3.

[0104] The FB panel 61E of the second gear cover 61 is provided with the FA, FB, and FC convex rings. The FA convex ring is located at the FA through-hole 61A, the FB convex ring is located at the FB through-hole 61B, and the FC convex ring is located at the FC through-hole 61C. The convex rings at the through-holes are used to support the outer ring of the bearing.

[0105] The FA outer convex ring is used to press against the upper end surface of the outer ring of the AB deep groove ball bearing 1D in the first rotation drive unit 1 .

[0106] The FB outer convex ring is used to press against the upper end surface of the outer ring of the BB deep groove ball bearing 2D in the second rotation drive unit 2 .

[0107] The FC outer convex ring is used to press against the upper end surface of the outer ring of the CB deep groove ball bearing 3D in the third rotation drive unit 3 .

[0108] The cooperation between the first gear cover 41 and the first external gear 7 can restrict the movement of the outer ring of the AA deep groove ball bearing 1C in the up-down direction.

[0109] The cooperation between the second gear cover 61 and the second external gear 8 can restrict the movement of the outer ring of the AB deep groove ball bearing 1D in the up-down direction.

[0110] Bearing inner ring baffle 62

[0111] like Figure 1D 、 Figure 5A As shown, the bearing inner ring baffle 62 is provided with an FA inner boss 62A, an FB inner boss 62B, and an FC inner boss 62C.

[0112] The EA inner boss 5A on the frame 5 is aligned with the FA inner boss 62A on the bearing inner ring baffle 62 and then fixed with screws.

[0113] The EB inner boss 5B on the frame 5 is aligned with the FB inner boss 62B on the bearing inner ring baffle 62 and then fixed with screws.

[0114] The EC inner boss 5C on the frame 5 is aligned with the FC inner boss 62C on the bearing inner ring baffle 62 and then fixed with screws.

[0115] First external gear 7

[0116] In the present invention, the first external gear 7 and the second external gear 8 have the same structure, but are assembled relative to each other. Figure 1B 、 Figure 1C 、 Figure 2D 、 Figure 5A shown.

[0117] like Figure 8 、 Figure 8AAs shown, a G center hole 7E is provided at the center of the first external gear 7, and then a GA stepped through hole 7A, a GB stepped through hole 7B, and a GC stepped through hole 7C are provided in three equal parts.

[0118] A GA inner baffle 7A1 is provided in the GA stepped through hole 7A. The GA inner baffle 7A1 is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 1C in the first rotary drive unit 1.

[0119] A GB inner baffle 7B1 is provided in the GB stepped through hole 7B. The GB inner baffle 7B1 is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 2C in the second rotation drive unit 2.

[0120] A GC inner baffle 7C1 is provided in the GC stepped through hole 7C. The GC inner baffle 7C1 is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 3C in the third rotation drive unit 3.

[0121] G external teeth 7D are provided on the outer circumferential surface of the first external gear 7 , and the G external teeth 7D mesh with the D internal teeth 4A of the internal gear 4 .

[0122] The GA face plate 71 of the first external gear 7 has a GA stepped through hole 7A, a GB stepped through hole 7B, and a GC stepped through hole 7C.

[0123] The GB face plate 72 of the first external gear 7 is a smooth surface.

[0124] Second external gear 8

[0125] The second external gear 8 is provided with an H center hole 8E at its center, and then divided into three equal parts: an HA stepped through hole 8A, an HB stepped through hole 8B, and an HC stepped through hole 8C.

[0126] An HA inner baffle is provided in the HA stepped through hole 8A and is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 1C in the first rotary drive unit 1 .

[0127] An HB inner baffle is provided in the HB stepped through hole 8B and is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 2C in the second rotary drive unit 2 .

[0128] An HC inner baffle is provided in the HC stepped through hole 8C and is used to press against the lower end surface of the outer ring of the AA deep groove ball bearing 3C in the third rotation drive unit 3 .

[0129] H external teeth 8D are provided on the outer circumferential surface of the second external gear 8 , and the H external teeth 8D mesh with the D internal teeth 4A of the internal gear 4 .

[0130] The HA panel of the second external gear 8 has an HA stepped through hole 8A, a HB stepped through hole 8B, and an HC stepped through hole 8C.

[0131] The HB face plate 82 of the second external gear 8 is a smooth surface.

[0132] In the present invention, the equally divided holes of the external gears (7, 8) are stepped holes for axial positioning on one side of the bearing, and the axial positioning on the other side of the bearing is achieved through a retaining ring. The three retaining rings are a whole and are fixed to the external gear through threaded connection.

[0133] In the present invention, the first gear cover 41, the first external gear 7, the second external gear 8 and the second gear cover 61 are all provided with through holes in three equal parts, and baffles are also provided in the through holes to form a stepped hole structure as shown in FIG. Figure 1D As shown. This type of stepped equally divided through hole cooperates with the bearing and is used for axial positioning on one side of the bearing. The axial positioning on the other side of the bearing is achieved through a retaining ring. The three retaining rings are a whole and are fixed to the external gears (7, 8) by threaded connection. On the other hand, after the DA through hole 41A of the first gear cover 41, the GA stepped through hole 7A of the first external gear 7, the HA stepped through hole 8A of the second external gear 8, and the FA through hole 61A of the second gear cover 61 are aligned, they are used to place the first rotation drive unit 1; after the DB through hole 41B of the first gear cover 41, the GB stepped through hole 7B of the first external gear 7, the HB stepped through hole 8B of the second external gear 8, and the FB through hole 61B of the second gear cover 61 are aligned, they are used to place the second rotation drive unit 2; after the DC through hole 41C of the first gear cover 41, the GC stepped through hole 7C of the first external gear 7, the HC stepped through hole 8C of the second external gear 8, and the FC through hole 61C of the second gear cover 61 are aligned, they are used to place the third rotation drive unit 3

[0134] Example 1

[0135] To gain a more intuitive understanding of the motion process of the involute small-tooth-difference drive used in a serpentine manipulator, and to further examine the feasibility and rationality of the distributed KHV rotary drive unit designed in this study, including its motion principle, mechanical structure, and control system, the distributed KHV rotary drive unit designed in this study had overall dimensions of 115 mm in diameter, 26 mm in thickness, a gear transmission contact ratio of 1.05, and a tooth profile overlap coefficient of 0.053. Performance testing was conducted.

[0136] The three motors in the prototype are DJ Yu 2008 brushless motors. The specific parameters of the motors are shown in Table 1. All non-standard parts in the prototype, such as gears, frames, eccentric shafts, and retaining rings, are made of 3D resin materials with a processing accuracy of ±200μm.

[0137] When the output of a serpentine manipulator's drive unit is rotational, harmonic or planetary speed reducers are often used to increase torque. Further research has revealed that involute gear transmissions with small tooth differences are particularly suitable for serpentine manipulator drive units due to their high transmission ratio, compact structure, reliable operation, and high resistance to overload and shock. The transmission performance of this rotary drive unit was tested. The primary objective was to verify its operational stability and demonstrate the feasibility of the mechanism and control system. The experiments measured the output speed of the internal gear of the rotary drive unit at different input speeds. Based on the experimental results, the actual transmission ratio of the rotary drive unit prototype was calculated. Two sets of experiments were conducted: one in which only one motor was powered and controlled to move at a constant speed at different speeds; the other in which all three motors were powered simultaneously at the same speed and controlled to move at a constant speed at different speeds.

[0138] The angular velocity of the internal gear was measured using a Shengli VC6235P handheld tachometer. The experimental data are shown in Table 2. As can be seen, when the motor input speed ranges from 400 rpm to 2000 rpm, the transmission ratio of the linear drive unit in both experimental groups is relatively stable, with the error within 3% of the theoretical value of 92. This demonstrates the feasibility of the linear drive unit's transmission principle and control system.

[0139] Table 2 Experimental results of the rotary drive unit prototype

[0140]

[0141] In the present invention, the maximum bending stress of the gear when the double external gears (7, 8) are used under different loading torques is obtained by finite element simulation, and compared with the conventional single external gear, see Table 3 and Figure 9 . Taking into account that in the KHV type small tooth difference transmission, the external gear performs high-speed eccentric motion, and there is an eccentric weight in the joint module, periodic interference force will be generated during operation, thereby generating vibration, aggravating bearing wear, reducing bearing service life, and even causing accidents in severe cases. Therefore, balancing measures must be taken to eliminate or reduce vibration. Because the ratio of the tooth thickness of the external gear used in the present invention to the gear diameter is small, the eccentric mass can be regarded as distributed in a rotating plane, so only static balance can be performed. Two identical external gears can be installed symmetrically relative to the center axis of the internal gear. During movement, the eccentricity is equal in size and opposite in direction, canceling each other out.

[0142] Table 3 Maximum bending stress of gears under different torques with different numbers of external gears

[0143]

[0144] exist Figure 9Taking the safety factor as 1.25, the allowable bending stress is 400 MPa, and the maximum output torque of the distributed KHV type rotary drive unit using the double external gear design of the present invention is 200 N·m.

[0145] In order to verify whether the transmission principle of the three groups of rotary drive units (1, 2, 3) designed by the present invention is feasible, its working state is determined, and the force conditions of the eccentric shafts (1C, 2C, 3C) are obtained (providing parameter constraints for the structural design of the eccentric shafts), and dynamic simulation analysis is performed on them. Since the three groups of rotary drive units (1, 2, 3) and the external gears (7, 8), and the external gears (7, 8) and the internal gear 4 adopt a bearing movable connection method, and the frame 5 and the internal gear 4 are coaxial, so that the internal gear 4 can only make circular motion around its axis, the positions of the three groups of rotary drive units (1, 2, 3) are constrained by the frame 5. At the same time, the two eccentric shaft segments of the eccentric shafts (1C, 2C, 3C) are coaxial with the three equally divided circular holes of the external gears (7, 8), constraining the movement of the external gears (7, 8). A rotary motor with a constant speed of 100 rpm is applied to the eccentric shaft. After running for 5 seconds, the output angular velocity fluctuation of the distributed KHV type involute small tooth difference joint module of the present invention is stable and can even be considered to be completely eliminated. The angular velocity obtained by simulation is 6.52 rad / s. When the eccentric shaft speed is 100 rpm, the angular velocity of the internal gear 4 is 6.52 rad / s. When the rotation motor is applied to two or three eccentric shafts at the same time, the angular velocity output curve is the same as Figure 10 Stay consistent.

[0146] In order to determine the number of gear pairs that are in contact when the outer gears (7, 8) are meshing with the inner gear 4 in the distributed KHV gear transmission, and to verify the calculation results of the transmitted torque with the eccentric shafts (1C, 2C, 3C), a finite element simulation analysis of the distributed KHV gear meshing is performed to obtain the stress cloud map and deformation cloud map of the gear under different loads, as shown in the figure. Figure 11 As shown in the figure. (a) and (b) are the stress and deformation nephograms of the gear when the load is 50N·m; (c) and (d) are the stress and deformation nephograms of the gear when the load is 150N·m; (e) and (f) are the stress and deformation nephograms of the gear when the load is 250N·m. According to the relationship between the maximum bending stress of the gear and the loading torque, the change in the number of gear pairs in simultaneous contact is nonlinear. The slope of the curve decreases with increasing loading torque and is equal when the loading torque is approximately 220N·m. At this time, the maximum bending stress of the gear is 575MPa.

[0147] The distributed KHV-type rotary drive unit structure designed by the present invention has motors distributed on the gears, which is compact, small, and flat. Compared with the MIT-configured drive unit of the same specification, the thickness is reduced by 30%. Compared with the KHV-type transmission, sliding friction is eliminated and efficiency is improved. The redundancy is high. With three motors driving, only one motor needs to be normal for the system to operate normally under low torque conditions.

Claims

1. A distributed K-H-V involute small tooth difference joint module, characterized by: The joint module is applied to the snake-like robotic arm; The joint module comprises a first rotation drive unit (1), a second rotation drive unit (2), a third rotation drive unit (3), an internal gear (4), a frame (5), a uniform cross-section thin-wall bearing (6), a first gear cover (41), a second gear cover (61), a first external gear (7), and a second external gear (8); Wherein, the first rotation drive unit (1), the second rotation drive unit (2) and the third rotation drive unit (3) have the same structure; Wherein, the first gear cover (41) and the second gear cover (61) have the same structure; The first external gear (7) and the second external gear (8) have the same structure; the GA panel (71) of the first external gear (7) is provided with a stepped through hole for placing a bearing, and the GB panel (72) of the first external gear (7) is a smooth surface; The D-axis center hole (41F) of the first gear cover (41), the G-axis center hole (7E) of the first external gear (7), the H-axis center hole (8E) of the second external gear (8), and the F-axis center hole (61F) of the second gear cover (61) are aligned and kept coaxial; wherein the frame (5) and the internal gear (4) remain coaxial; The first rotary drive unit (1) comprises a brushless DC motor (1A), an eccentric shaft cover (1B), an AA deep groove ball bearing (1C), an AB deep groove ball bearing (1D), an A reverse retaining spring (1E), an eccentric shaft (1F) and an A shaft ring (1G); the motor output shaft (1A1) of the motor (1A) sequentially passes through the AB center through hole (1F1) of the eccentric shaft (1F) and the AA center through hole (1B1) of the eccentric shaft cover (1B); the eccentric shaft (1F) and the eccentric shaft cover (1B) are fixed to the front end cover of the motor (1A) by screws; the AA deep groove ball bearing (1C) is installed on the AA shaft section (1F7) of the eccentric shaft (1F), the AB deep groove ball bearing (1D) is installed on the AB shaft section (1F8), the A shaft ring (1G) is installed on the AC shaft section (1F9), and the retaining groove (1F 10) A reverse retaining spring (1E) is installed on it; The inner ring surface of the internal gear (4) is provided with D inner teeth (4A), D inner convex ring (4C) and D bearing section (4B) in sequence; the D inner convex ring (4C) is used to block and limit the movement of the uniform cross-section thin-walled bearing (6) in the vertical direction; the outer ring of the uniform cross-section thin-walled bearing (6) is connected to the D bearing section (4B) of the internal gear (4), and the inner ring of the uniform cross-section thin-walled bearing (6) is connected to the E bearing section (5F) of the frame (5); the D inner teeth (4A) of the internal gear (4) are used to mesh with the G outer teeth (7D) on the first external gear (7) and the H outer teeth (8D) on the second external gear (8); The joint module uses two external gears (7, 8) with the same structure and is placed symmetrically relative to the central axis of the internal gear (4). When moving, the eccentricities are equal in size and opposite in direction, and cancel each other out.

2. The distributed K-H-V type involute small tooth difference joint module according to claim 1 is characterized in that: During the transmission process of the joint module driven by the motor, the eccentric shaft rotates to drive the internal gear to output the speed, and the external gear moves horizontally.

3. The distributed K-H-V type involute small tooth difference joint module according to claim 1, characterized in that: The joint module has a flat structure.

4. The distributed K-H-V type involute small tooth difference joint module according to claim 1, characterized in that: The joint module adopts a distributed K-H-V type rotary drive unit with a double external gear design and a maximum output torque of 200N·m. 。 5. The distributed K-H-V type involute small tooth difference joint module according to claim 1, characterized in that: The joint module is made of steel, aluminum alloy or resin.

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