Low-inertia small robot leg structure

Abstract

The low-inertia small robot leg structure comprises a first connecting piece, a second connecting piece and a shank, the first connecting piece is provided with a first joint motor, the first joint motor is connected with the second connecting piece, and the axis of the first joint motor is perpendicular to the axis of the second connecting piece; a second joint motor is arranged on the second connecting piece, and a thigh clamping plate is connected to the second joint motor; a third joint motor is arranged between the thigh clamping plates, the shanks are rotationally arranged between the bottoms of the thigh outer clamping plates and the thigh inner clamping plates to form knee joints, and connecting rods are rotationally connected between the positions, lower than the knee joints, of the shanks and the third joint motor. According to the leg compact structure design suitable for the small robot, the number of transmission mechanisms at the knee joints is reduced, the rotational inertia of the legs of the robot is reduced, the energy consumption intensity is reduced under the condition that the battery energy of the small robot is low, and the standby time of the small robot is prolonged.

Description

Technical Field

[0001] This invention relates to the field of legged robot technology, and more particularly to a low-inertia small robot leg structure. Background Technology

[0002] Legged robots, such as quadrupedal and bipedal humanoid robots, have become a research hotspot in the field of robotics due to their excellent terrain adaptability. To achieve highly dynamic running and jumping movements, the design of robot legs must pursue extreme lightweighting and high power density. In structural design, the rational arrangement of joint drive units, namely motors and reducers, is a key factor determining the overall performance of the robot.

[0003] In the design of legged robots, there is a core contradiction: "reducing the end-effector inertia" versus "compactness of the drive unit arrangement." To make the leg swing faster and with less impact, current methods typically move the heavier motors to the hip joint at the base of the torso or thigh, minimizing the weight of the lower leg and foot to reduce the inertia during leg swing. When multiple motors, such as those responsible for thigh swing and those driving the knee joint, are concentrated at the hip joint, power is usually transmitted to the knee joint via linkages or timing belts. This results in two or more motor drive modules needing to be accommodated within the small space of the hip joint. This approach tends to make the overall leg structure thicker and increase the number of transmission mechanisms, thus increasing the overall weight of the robot's leg. Especially in the design of small robots, for low-power joint motors, the motor structure is often slender due to the size limitations of the internal rotor, stator, and reducer. Arranging them in the above manner would result in an excessively large and uncoordinated axial dimension, while simultaneously increasing the rotational inertia of the robot's leg and increasing energy consumption. To address the aforementioned issues, there is an urgent need to develop a compact leg structure design suitable for small robots, reducing the number of transmission mechanisms at the knee joint, lowering the rotational inertia of the robot's legs, reducing energy consumption intensity when the battery power of small robots is low, and increasing the standby time of small robots. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and to provide a compact leg structure design suitable for small robots, which reduces the number of transmission mechanisms at the knee joint, reduces the rotational inertia of the robot's legs, reduces energy consumption intensity when the battery energy of the small robot is low, and improves the standby time of the small robot.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A low-inertia small robot leg structure includes a first connector, a second connector, and a lower leg. A first joint motor is mounted on the first connector, and the first joint motor is connected to the second connector with its axis perpendicular to the axis of the second connector. A second joint motor is mounted on the second connector, and an outer thigh clamp is connected to the second joint motor. A synchronously swinging inner thigh clamp is connected to the outer thigh clamp, and the top of the inner thigh clamp is rotatably connected to a bearing hole on the side of the second connector. A third joint motor is positioned between the outer thigh clamp and the inner thigh clamp. The lower leg is rotatably positioned between the bottom of the outer thigh clamp and the inner thigh clamp to form a knee joint. A connecting rod is rotatably connected between the lower leg and the third joint motor at a position below the knee joint.

[0007] Furthermore, the outer surface of the second connector is provided with reinforcing ribs and a wire outlet hole, and the edge of the second connector is provided with a limiting end face. When the outer thigh splint and the inner thigh splint swing up and down to the extreme position, the limiting end face abuts against the side of the outer thigh splint and the inner thigh splint.

[0008] Furthermore, the outer thigh clamp and the inner thigh clamp are connected and fixed by multiple internal threaded pins and bolts. The two sides of the third joint motor are connected to the outer thigh clamp and the inner thigh clamp by fixing brackets. The gap between the third joint motor and the second joint motor is the spacing that only requires one internal threaded pin.

[0009] Furthermore, the third joint motor and the connecting rod are connected to the threaded hole on the output end face of the third joint motor by bolts passing through the sleeve, flange bearing, and thrust bearing in sequence.

[0010] Furthermore, the lower leg and the connecting rod are axially compressed by a common threaded pin and two bolts on the left and right. A thrust bearing is provided between the lower leg and the connecting rod. The bolt on one side of the lower leg contacts the flange bearing on the lower leg through a washer. A deep groove ball bearing is sleeved between the lower leg and the threaded pin. A sleeve is provided between the deep groove ball bearing and the thrust bearing. The bolt on one side of the connecting rod contacts the connecting rod through a washer.

[0011] Furthermore, the lower leg, the outer thigh splint, and the inner thigh splint are all fitted with internally threaded pins. The two sides of the internally threaded pins are connected to the outer thigh splint and the inner thigh splint by bolts and flange bearings. The lower leg and the flange bearings are axially pressed together by a sleeve.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] This invention simultaneously satisfies the requirements of reducing the end-effector inertia of small robots and ensuring a compact arrangement of the drive units. Because the third joint motor is positioned close to the second joint motor, with only a threaded pin between them, the third joint motor can be positioned as high as possible in the thigh, reducing the lever arm length during its swing and thus lowering the rotational inertia of the thigh. Furthermore, only a single link is needed between the third joint motor and the lower leg to control the lower leg's swing around the knee joint, further reducing the number of transmission mechanisms at the knee joint, minimizing the weight of the robot's legs, and further reducing the rotational inertia of the legs. This leg structure reduces energy consumption and increases standby time in small robots with low battery power. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention;

[0015] Figure 2 This is a diagram showing the connection structure of the thigh clamp and the second connector in this invention.

[0016] Figure 3 This is a connection structure diagram of the first connector and the second connector in this invention;

[0017] Figure 4 This is a schematic diagram of the structure of the second connector in this invention;

[0018] Figure 5 This is a diagram showing the connection structure between the third joint motor and the lower leg in this invention;

[0019] Figure 6 This is a diagram showing the shaft system structure of the third joint motor and connecting rod in this invention;

[0020] Figure 7 This is a diagram showing the shaft system structure of the lower leg and connecting rod in this invention;

[0021] Figure 8 This is a diagram showing the axial structure of the lower leg and thigh splints in this invention.

[0022] Figure label:

[0023] 1-First connector, 2-First joint motor, 3-Second connector, 4-Second joint motor, 5-Outer thigh splint, 6-Inner thigh splint, 7-Third joint motor, 8-Fixing bracket, 9-Internal threaded pin, 10-Lower leg, 11-Connecting rod, 12-Thrust bearing, 13-Flange bearing, 14-Sleeve, 15-Bolt, 16-Washer, 17-Deep groove ball bearing, 31-Limiting end face, 32-Reinforcing rib, 33-Cable outlet hole, 34-Bearing hole. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0025] like Figures 1 to 8 As shown, a low-inertia small robot leg structure includes a first connector 1, a second connector 3, and a lower leg 10. A first joint motor 2 is provided on the first connector 1, and the first joint motor 2 is connected to the second connector 3 with the axis of the first joint motor 2 perpendicular to the axis of the second connector 3. A second joint motor 4 is provided on the second connector 3, and an outer thigh clamp 5 is connected to the second joint motor 4. An inner thigh clamp 6 that swings synchronously is connected to the outer thigh clamp 5. The top of the inner thigh clamp 6 is rotatably connected to a bearing hole 34 on the side of the second connector 3. A third joint motor 7 is provided between the outer thigh clamp 5 and the inner thigh clamp 6. The lower leg 10 is rotatably positioned between the bottom of the outer thigh clamp 5 and the inner thigh clamp 6 to form a knee joint. A connecting rod 11 is rotatably connected between the lower leg 10 and the third joint motor 7 at a position below the knee joint.

[0026] like Figures 2 to 4 As shown, the outer surface of the second connector 3 is provided with reinforcing ribs 32 and a cable outlet hole 33. The edge of the second connector 3 is provided with a limiting end face 31. When the outer thigh clamp 5 and the inner thigh clamp 6 swing up and down to their extreme positions, the limiting end face 31 abuts against the side of the outer thigh clamp 5 and the inner thigh clamp 6. The reinforcing ribs 32 increase the load of the second connector 3, preventing the second connector 3 from deforming or breaking due to an increase in the leg swing frequency. The limiting end face 31 is used to help limit the maximum swing angle of the thigh.

[0027] The outer thigh clamp 5 and the inner thigh clamp 6 are connected and fixed by multiple internally threaded pins 9 and bolts. The two sides of the third joint motor 7 are connected to the outer thigh clamp 5 and the inner thigh clamp 6 by fixing brackets 8. The gap between the third joint motor 7 and the second joint motor 4 is such that only one internally threaded pin 9 is needed. Designing the thigh structure of the robotic leg as a split outer thigh clamp 5 and inner thigh clamp 6 can reduce the weight of the thigh shell structure. At the same time, setting multiple internally threaded pins 9 between the clamps can also ensure the connection strength of the clamps. In order to minimize the rotational inertia of the robotic leg, the third joint motor 7 is set close to the second joint motor 4 and only one internally threaded pin 9 is set between the two. This allows the third joint motor 7 to be positioned as high as possible in the thigh, reducing the lever arm length of the third joint motor 7 when swinging, thereby reducing the rotational inertia of the thigh when swinging.

[0028] This invention simultaneously satisfies the requirements of reducing the end-effector inertia of small robots and ensuring a compact arrangement of drive units. The first connector 1, the first joint motor 2, the second connector 3, and the second joint motor 4 together form the hip joint of the leg. The design of the first joint motor 2's axis being perpendicular to the second connector 3's axis, compared to setting the two motors coaxially, avoids the disharmony of excessively large axial dimensions when using low-power, slender motors in small robots, reduces the rotational inertia of the robot's thigh, and prevents the thigh from becoming too thick, thus avoiding increased weight. The third joint motor 7 is positioned close to the second joint motor 4, allowing it to be located as high as possible in the thigh, reducing the lever arm length of the third joint motor 7 during swinging, thereby reducing the rotational inertia of the thigh during swinging.

[0029] Only one link 11 is used between the third joint motor 7 and the lower leg 10. The third joint motor 7 can drive one end of the link 11 to make a circular reciprocating motion to control the lower leg 10 to swing around the knee joint position. This further reduces the number of transmission mechanisms at the knee joint, realizes the compact arrangement of the drive unit, reduces the weight of the robot leg as a whole by reducing the transmission mechanism, and further reduces the rotational inertia of the robot leg.

[0030] Therefore, this invention reduces energy consumption by decreasing the rotational inertia of the robot's legs, thus extending the standby time of small robots with low battery power. It is particularly suitable for small robots using low-power, slender motors, avoiding the disproportionate size caused by excessively long hip joints, which would lead to a wider torso. It is especially suitable for legged robots with high requirements for miniaturization and lightweight design and limited power supply, such as small quadruped robots for indoor inspection or security, small bipedal robots for teaching and research, and small collaborative and companion robots for navigating narrow spaces. To improve applicability in practical scenarios, these robots often pursue smaller size and lower overall weight. However, limited by battery capacity and heat dissipation, the joint drive units typically use low-power, high-speed motor modules with reducers, resulting in a slender structure with a smaller diameter and longer axial length. If multiple slender motors are arranged in a traditional coaxial stacking manner, it can easily lead to a significant increase in the lateral dimensions of the hips and thighs, increased weight of the shell and connectors, and reduced space utilization. This invention optimizes the non-coaxial compact arrangement and key dimensions of the hip joint drive unit, namely the motor spacing and lever arm direction, to reduce the leg shape envelope and joint swing inertia without increasing the complexity of the transmission chain. This reduces energy consumption and improves battery life under conditions of small battery and low power, and enhances the robot's mobility and movement stability in real-world environments such as narrow passages and indoor furniture environments.

[0031] like Figure 6As shown, the third joint motor 7 and connecting rod 11 are connected by bolts 15 that pass sequentially through sleeve 14, flange bearing 13, and thrust bearing 12 to the threaded hole on the output end face of the third joint motor 7. Axial positioning of the third joint motor 7 and connecting rod 11 is achieved by tightening the bolts 15 into the threaded hole on the output end face of the third joint motor 7. Specifically, the bolts 15 are plug bolts, which contact the inner ring of the flange bearing 13 through sleeve 14. The outer ring of the flange bearing 13 is pressed against the connecting rod 11, and the connecting rod 11 is engaged with the loose ring of the thrust bearing 12. The connecting rod 11 also contacts the output end face of the third joint motor 7 through balls and a tight ring, thus achieving axial positioning of the entire shaft system. Circumferential positioning is mainly achieved through the tight ring engagement of the plug bolts with the flange bearing 13 and the thrust bearing 12.

[0032] like Figure 7 As shown, the lower leg 10 and the connecting rod 11 are axially clamped by a common threaded pin 9 and two bolts 15 on the left and right. A thrust bearing 12 is provided between the lower leg 10 and the connecting rod 11. The bolt 15 on one side of the lower leg 10 contacts the flange bearing 13 on the lower leg 10 through a washer 16. A deep groove ball bearing 17 is sleeved between the lower leg 10 and the threaded pin 9. A sleeve 14 is provided between the deep groove ball bearing 17 and the thrust bearing 12. The bolt 15 on one side of the connecting rod 11 contacts the connecting rod 11 through a washer 16.

[0033] For axial fixation, the preload generated by tightening the internal threaded pin 9 and the two bolts 15 on the left and right achieves axial compression of the lower leg 10 and connecting rod 11. Specifically, looking from left to right, the bolt 15 contacts the inner ring of the flange bearing 13 through the washer 16, and the outer ring of the flange bearing 13 contacts the lower leg 10. The lower leg 10 contacts the outer ring of the deep groove ball bearing 17, the outer ring of the deep groove ball bearing 17 contacts the sleeve 14, the sleeve 14 contacts the loose ring of the thrust bearing 12, the loose ring is tightly fitted with the lower leg 10, and then contacts the connecting rod 11 through the balls and the tight ring, and finally contacts the bolt 15 through the washer 16. The key to the transmission of axial force is to achieve both the positioning of each part and the isolation of relatively rotating parts, so that the entire shaft system only has rolling friction. For circumferential fixation, it is mainly achieved by one flange bearing 13, two deep groove ball bearings 17, and one thrust bearing 12, all of which are fitted with the internal threaded pin 9. The two deep groove ball bearings 17 serve to balance the force on the lower leg 10 and increase its load-bearing capacity. The internal threaded pin 9 is tightly fitted with the connecting rod 11 to transmit the driving force of the lower leg 10 to the connecting rod 11, thereby causing the lower leg 10 to rotate around the knee joint.

[0034] like Figure 8As shown, the lower leg 10, the outer thigh splint 5, and the inner thigh splint 6 are all fitted with an internally threaded pin 9. The two sides of the internally threaded pin 9 are connected to the outer thigh splint 5 and the inner thigh splint 6 via bolts 15 and flange bearings 13. The lower leg 10 and the flange bearings 13 are axially pressed together by sleeves 14. The knee joint system primarily supports the rotation of the lower leg 10. The lower leg 10 is tightly fitted with the internally threaded pin 9 and, through the axial positioning of the two sleeves 14, is supported on the inner thigh splint 6 and the outer thigh splint 5 by the flange bearings 13 on both sides.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-inertia leg structure for a small robot, characterized in that: The device includes a first connector (1), a second connector (3), and a lower leg (10). The first connector (1) is equipped with a first joint motor (2), which is connected to the second connector (3) and the axis of the first joint motor (2) is perpendicular to the axis of the second connector (3). The second connector (3) is equipped with a second joint motor (4), which is connected to an outer thigh splint (5). The outer thigh splint (5) is connected to a synchronously swinging inner thigh splint (6). The top of the inner thigh splint (6) is rotatably connected to the bearing hole (34) on the side of the second connector (3). A third joint motor (7) is provided between the outer thigh splint (5) and the inner thigh splint (6). The lower leg (10) is rotatably positioned between the bottom of the outer thigh splint (5) and the inner thigh splint (6) to form a knee joint. The lower leg (10) is rotatably connected to the third joint motor (7) at a position below the knee joint by a connecting rod (11).

2. The low-inertia small robot leg structure according to claim 1, characterized in that: The outer surface of the second connector (3) is provided with reinforcing ribs (32) and wire outlet holes (33). The edge of the second connector (3) is provided with a limiting end face (31). When the outer thigh clamp (5) and the inner thigh clamp (6) swing up and down to the limit position, the limiting end face (31) abuts against the side of the outer thigh clamp (5) and the inner thigh clamp (6).

3. The low-inertia small robot leg structure according to claim 1, characterized in that: The outer thigh splint (5) and the inner thigh splint (6) are connected and fixed by multiple internal threaded pins (9) and bolts (15). The two sides of the third joint motor (7) are connected to the outer thigh splint (5) and the inner thigh splint (6) by a fixing bracket (8). The gap between the third joint motor (7) and the second joint motor (4) is the spacing that only requires one internal threaded pin (9).

4. The low-inertia small robot leg structure according to claim 1, characterized in that: The third joint motor (7) and the connecting rod (11) are connected to the threaded hole on the output end face of the third joint motor (7) by bolts (15) passing through the sleeve (14), flange bearing (13), and thrust bearing (12) in sequence.

5. The low-inertia small robot leg structure according to claim 1, characterized in that: The lower leg (10) and the connecting rod (11) are axially pressed together by a common threaded pin (9) and two bolts (15) on the left and right. A thrust bearing (12) is provided between the lower leg (10) and the connecting rod (11). The bolt (15) on one side of the lower leg (10) contacts the flange bearing (13) on the lower leg (10) through a washer (16). A deep groove ball bearing (17) is sleeved between the lower leg (10) and the threaded pin (9). A sleeve (14) is provided between the deep groove ball bearing (17) and the thrust bearing (12). The bolt (15) on one side of the connecting rod (11) contacts the connecting rod (11) through a washer (16).

6. The low-inertia small robot leg structure according to claim 5, characterized in that: The lower leg (10) is connected to the outer thigh splint (5) and inner thigh splint (6) by an internal threaded pin (9). The two sides of the internal threaded pin (9) are connected to the outer thigh splint (5) and inner thigh splint (6) by bolts (15) and flange bearings (13). The lower leg (10) and flange bearings (13) are axially pressed together by a sleeve (14).

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