Variable stiffness cushioning structure and bionic biped robot

Abstract

The variable stiffness buffer structure and bionic biped robot relate to the field of robot technology. The existing foot type robot has the problems of poor impact resistance and poor terrain adaptability. The present application comprises a buffer elastic element, a tendon and a steering support assembly, the steering support assembly is installed on the leg of the robot and can be deflected, the buffer elastic element is installed on the steering support assembly and can be deflected with the steering support assembly; the tendon connects the buffer elastic element and the foot of the robot and is in tension; when the foot of the robot contacts the ground, the foot of the robot flips around the ankle joint and pulls the tendon, the buffer elastic element deforms through the stretching of the tendon, when the foot of the robot is lifted, the foot of the robot resets under the resilience of the buffer elastic element. With the deflection of the steering support assembly, the buffer elastic element deflects while the included angle between the buffer elastic element and the tendon changes, the resultant force in the direction of the tendon changes, the stiffness of the variable stiffness buffer structure is changed. The present application is mainly used for the design of the robot.

Description

Technical Field

[0001] This invention relates to the field of robotics, and more particularly to a variable stiffness buffer structure and a biomimetic bipedal robot. Background Technology

[0002] Humanoid robots possess high flexibility, adaptability, and maneuverability to complex terrains; they can freely use human tools; and their human-like appearance allows for more natural human-robot interaction, making them highly promising for applications in human society. Their bipedal walking locomotion, similar to humans, offers greater mobility than wheeled or tire-driven systems; therefore, designing the lower limb structure of humanoid robots to more closely resemble human legs is of paramount importance.

[0003] Currently, the connection between the legs and feet of humanoid robots is mostly rigid. When a legged robot moves, especially during vigorous movements such as jumping, the feet experience impact force upon contact with the ground. This impact force is transmitted to the robot's ankle and leg joints, causing significant vibration to these components and affecting their lifespan. Therefore, current legged robots suffer from poor impact resistance. Summary of the Invention

[0004] In view of this, the present invention provides a variable stiffness buffer structure and a bionic bipedal robot. The variable stiffness buffer structure absorbs the impact force on the feet of the bipedal robot during movement, thereby increasing the impact resistance of the bipedal robot. At the same time, the variable stiffness buffer structure can also be used to change the ankle joint stiffness, thereby increasing the adaptability of the bipedal robot to different terrains.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] A variable stiffness buffer structure includes a buffer elastic element and a tendon. The buffer elastic element and the tendon are arranged on the rear side of the leg. The buffer elastic element is installed on the robot's leg, and the tendon connects the buffer elastic element to the robot's foot and is tensioned. When the robot's foot contacts the ground, the robot's foot rotates around the ankle joint and pulls the tendon, and the buffer elastic element deforms due to the stretching of the tendon. When the robot's foot is lifted, the robot's foot returns to its original position under the rebound of the buffer elastic element.

[0007] Furthermore, it also includes a steering support assembly, which is mounted on the robot's legs and can deflect. A buffer elastic element is mounted on the steering support assembly and can deflect with the steering support assembly. As the steering support assembly deflects, the angle between the buffer elastic element and the tendon changes, and the resultant force along the tendon direction changes, thereby realizing the change of the stiffness of the variable stiffness buffer structure.

[0008] Furthermore, the steering support assembly includes a steering motor and a support sleeve for supporting the buffer elastic element. The support sleeve is connected to the motor shaft of the steering motor and can rotate with the motor shaft. The buffer elastic element is built into the support sleeve. When the steering motor is started, the support sleeve rotates with the motor shaft of the steering motor, so that the buffer elastic element deflects.

[0009] Furthermore, it also includes a tensioning wheel and an ankle joint locking assembly for locking the ankle joint; the tensioning wheel is mounted on the robot's leg and is rotatable; the ankle joint locking assembly includes a locking slide, a pressure plate, and a slide lock member, the pressure plate is placed on top of and in contact with the cushioning elastic member, and the locking slide passes through the pressure plate, the cushioning elastic member, and the support sleeve in sequence and is axially movable; one end of the tendon is connected to the lower end of the locking slide, and the other end of the tendon passes around the tensioning wheel and is connected to the foot; the slide lock member is mounted on the robot's leg and has a locking brake part that cooperates with the locking slide; when the locking brake part of the slide lock member brakes the locking slide, the position of the locking slide is locked, the tendon is tensioned and held, and the position of the ankle joint is locked, so that the variable stiffness buffer structure switches from a variable stiffness mode to a pure stiffness mode.

[0010] Furthermore, the sliding pin locking component is provided with a locking pin, which can be driven to extend and retract. The lower end of the locking sliding pin has a locking hole. When the locking pin of the sliding pin locking component extends, the locking pin is inserted into the locking hole of the locking sliding pin, so that the locking sliding pin is locked.

[0011] A biomimetic bipedal robot includes legs and feet, with the legs and feet movably connected and forming an ankle joint at the connection point; it also includes a variable stiffness buffer structure; the variable stiffness buffer structure connects the legs and feet to mitigate the impact force on the feet during movement and increase the bipedal robot's terrain adaptability.

[0012] Furthermore, it also includes a fuselage and a hip joint drive mechanism; the hip joint drive mechanism connects the fuselage and the leg and drives the leg to perform two-degree-of-freedom motion; the hip joint drive mechanism includes a motor connector, a lateral swing motor and a hip joint pitch motor, the housing of the lateral swing motor is mounted on the fuselage, the motor connector is connected to the motor shaft of the lateral swing motor and rotates with the motor shaft, the housing of the hip joint pitch motor is mounted on the motor connector, and the leg is connected to the motor shaft of the hip joint pitch motor and rotates with the motor shaft; when the motor connector rotates with the motor shaft of the lateral swing motor, the motor connector drives the hip joint pitch motor and the leg to perform lateral swing motion; when the leg rotates with the motor shaft of the hip joint pitch motor, the leg performs pitch motion.

[0013] Furthermore, the leg includes a thigh, a lower leg, and a knee joint drive mechanism; the thigh and lower leg are movably connected and form a knee joint at the connection point; the knee joint drive mechanism connects the thigh and lower leg and drives the lower leg to perform pitching motion around the knee joint; the knee joint drive mechanism includes a knee joint pitching motor, a crank, connecting rod one, connecting rod two, and connecting rod three; the knee joint pitching motor is mounted on the thigh; one end of the crank is connected to the motor shaft of the knee joint pitching motor and rotates with the motor shaft; the other end of the crank is hinged to one end of connecting rod one; the other end of connecting rod one is hinged to one end of connecting rod two; the other end of connecting rod two is hinged to the top of the lower leg; one end of connecting rod three is connected to the connection point of connecting rod one and connecting rod two and is rotatable; the other end of connecting rod three is connected to the thigh and is rotatable; when the crank rotates with the motor shaft of the knee joint pitching motor, the torque of the crank is transmitted to the lower leg sequentially through connecting rod one and connecting rod two, so that the lower leg performs pitching motion around the knee joint.

[0014] Furthermore, the heel of the foot is provided with a limiting block 1 to prevent the lower leg from turning backward, and the lower end of the front of the thigh is provided with a limiting block 2 to prevent the thigh from tilting forward; when the legged robot stands, the lower end of the lower leg abuts against the limiting block 1 and can remain stationary, while the limiting block 2 on the thigh abuts against the upper end of the lower leg, and the thigh can remain upright and stationary, thus realizing the robot's undriven standing.

[0015] Furthermore, the foot includes a sole, toes, and a torsion spring. The sole and toes are movably connected by a pin, the torsion spring is sleeved on the pin, and the two torsional feet of the torsion spring respectively abut against the sole and toes.

[0016] The beneficial effects of this invention compared to the prior art are:

[0017] 1. The present invention arranges a variable stiffness buffer structure with rigid-flexible coupling between the legs and feet of a legged robot. The elasticity of the variable stiffness buffer structure absorbs the impact force on the feet, thereby increasing the impact resistance of the legged robot. The variable stiffness of the variable stiffness buffer structure is also used to adapt to complex road conditions, thereby increasing the adaptability and motion stability of the legged robot.

[0018] 2. The knee joint drive mechanism design in this invention not only enables pitching motion of the lower leg but also allows the leg to assume an upright and fully retracted position. In the fully retracted position, it saves on the robot's storage volume. Furthermore, placing the knee joint pitch motor on the thigh side, symmetrically arranged with the hip joint pitch motor, not only ensures the uniformity of leg mass but also enables long-distance drive of the knee joint, increasing the lever arm length and reducing the motor's output torque. It also raises the leg's center of gravity, reduces leg inertia, achieves a lightweight leg design, and significantly reduces the difficulty of leg control.

[0019] 3. In this invention, mechanical limiters are designed at the heel of the foot and the lower end of the thigh, which enables the legged robot to stand without drive and avoids the defect of falling when the power is off. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are provided to further illustrate the invention.

[0021] Figure 1 A cross-sectional view of a variable stiffness buffer structure mounted on the robot's leg.

[0022] Figure 2 A schematic diagram of the variable stiffness buffer structure of the present invention.

[0023] Figure 3 This is a schematic diagram of a variable stiffness buffer structure installed on the legs of a robot.

[0024] Figure 4 A schematic diagram of the structure of the legged robot of the present invention.

[0025] Figure 5 This is a schematic diagram of a legged robot in a fully converged state.

[0026] Figure 6 This is a schematic diagram of the assembly of the fuselage, hip joint drive mechanism, and thigh.

[0027] Figure 7 This is an assembly diagram of the drive mechanism for the thigh, calf, and knee joints.

[0028] Figure 8 This is a schematic diagram illustrating the stiffness change of a variable stiffness buffer structure during deflection.

[0029] Explanation of reference numerals in the attached figures:

[0030] Variable stiffness buffer structure 1, buffer elastic element 11, tensioning wheel 12, tendon 13, tendon tensioning knob 14, steering support assembly 15, mounting bracket 151, steering motor 152, support sleeve 153, ankle joint locking assembly 16, locking slide 161, pressure plate 162, slide lock 163;

[0031] Fuselage 2;

[0032] Thigh 3, Limiting Block 2 31;

[0033] 4 for the lower leg;

[0034] Foot 5, sole 51, toes 52, torsion spring 53; limiting block 1 54;

[0035] Hip joint drive mechanism 6, motor connector 61, side swing motor 62, hip joint pitch motor 63;

[0036] 7. Knee joint drive mechanism, 71. Knee joint pitch motor, 72. Crank, 73. Connecting rod one, 74. Connecting rod two, 75. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0038] Example 1:

[0039] Existing robots typically use ankle joint actuators to drive their feet, enabling pitch and roll movements. However, these typical ankle joint actuators provide purely rigid actuation to the feet. When a legged robot moves, especially during vigorous movements like jumping, the foot experiences impact force upon contact with the ground. This impact force is transmitted to the robot's legs, causing significant vibration to the legs and motors, thus affecting the lifespan of the robot's feet, legs, and motors. Furthermore, bipedal robots require varying ankle joint stiffness for different terrains; a fixed ankle joint stiffness cannot improve the terrain adaptability of bipedal robots.

[0040] Therefore, such as Figures 1 to 8 As shown, this embodiment provides a variable stiffness buffer structure, including a buffer elastic element 11, a tendon 13, and a tendon tension knob 14. The robot's leg and foot are movably connected, forming an ankle joint at the connection point. The buffer elastic element 11 and the tendon 13 are arranged on the rear side of the leg. The buffer elastic element 11 is installed on the robot's leg, and a threading hole is opened on the robot's foot near the heel. The tendon tension knob 14 is installed on the instep of the robot's foot. The buffer elastic element 11 is connected to one end of the tendon 13 and deforms as the tendon 13 is stretched. The other end of the tendon 13 passes through the threading hole on the robot's foot and is connected to the tendon tension knob 14. The tendon 13 is pre-tightened by turning the tendon tension knob 14.

[0041] In this embodiment, the foot and leg of the legged robot are connected not only by the ankle joint but also by a variable stiffness buffer structure. This variable stiffness buffer structure consists of a buffer elastic element 11 and a tendon 13. The tendon 13 is a long, flexible rope-like component, and the buffer elastic element 11 can be a spring, a multi-leaf disc spring, or other elastic elements that can deform along the extension direction of the tendon 13. Therefore, the variable stiffness buffer structure as a whole is an elastic flexible component. When the legged robot performs actions such as walking or jumping, the robot's foot experiences an impact force upon contact with the ground. Under this impact force, the foot rotates around the ankle joint and pulls the tendon 13. The buffer elastic element 11 deforms due to the stretching of the tendon 13, absorbing part of the impact force and anti-interference force, thus buffering the mechanical components such as the foot, ankle joint, and leg. This extends the lifespan of the legged robot and improves its stability during movement. When the legged robot lifts its leg, the buffer elastic element 11 returns to its original position under its own rebound force, and the foot rotates around the ankle joint and returns to its original position via the tendon 13.

[0042] like Figure 1 , Figure 2 and Figure 3 As shown, legged robots need to adapt to different usage environments to increase their versatility. Generally, they operate on soft surfaces like sand or hard surfaces like asphalt. On soft surfaces, when a legged robot walks or jumps, the deformation of the soft ground absorbs the impact force between the robot and the ground. If the variable stiffness buffer structure has low rigidity and high elasticity, the ankle joint is more prone to deformation, resulting in poor stability for the legged robot on soft surfaces. On hard surfaces, the impact force between the legged robot and the ground is large. If the variable stiffness buffer structure has high rigidity and low elasticity, its cushioning effect is poor, and the foot will still experience significant impact and interference.

[0043] Therefore, the variable stiffness buffer structure described in this embodiment further includes a steering support assembly 15 for changing the stiffness of the variable stiffness buffer structure. Specifically, the steering support assembly 15 includes a mounting frame 151, a steering motor 152, and a support sleeve 153 for supporting the buffer elastic element 11. The mounting frame 151 is fixedly mounted on the robot's leg, the housing of the steering motor 152 is mounted on the mounting frame 151, and the support sleeve 153 is mounted on the mounting frame 151 via a pin and can rotate around the pin. At the same time, the support sleeve 153 is connected to the motor shaft of the steering motor 152 and rotates under the drive of the motor shaft. The motor shaft and the pin are arranged coaxially to avoid rotational interference; the buffer elastic element 11 is built into the support sleeve 153.

[0044] In this embodiment, the buffer elastic element 11 is installed on the robot's leg via the steering support assembly 15. When the steering support assembly 15 is in its initial position, the deformation direction of the buffer elastic element 11 is close to 180° with the extension direction of the tendon 13. At this time, the buffer elastic element 11 is easily deformed under the tension of the tendon 13. When the steering support assembly 15 deflects, the buffer elastic element 11 will also deflect together. At this time, the angle between the buffer elastic element 11 and the tendon 13 gradually decreases. With the length of the buffer elastic element 11 remaining unchanged, the elastic force of the buffer elastic element 11 remains unchanged, but the resultant force along the tendon direction increases, and the ankle joint stiffness increases. Therefore, as the angle between the buffer elastic element 11 and the tendon 13 changes, the stiffness of the variable stiffness buffer structure can be changed to adapt to different road conditions and increase the stability of the robot's movement. When the legged robot moves from a hard surface to a soft surface, the steering motor 152 is activated. The support sleeve 153 rotates with the motor shaft of the steering motor 152, and the cushioning elastic element 11 deflects along with the support sleeve 153. As the cushioning elastic element 11 deflects, the angle between it and the tendon 13 gradually decreases, and the tension of the tendon 13 gradually increases, thereby increasing the stability of the connection between the foot and leg when the legged robot is on soft ground. Conversely, when the legged robot moves from a soft surface to a hard surface, the steering motor 152 reverses direction, the support sleeve 153 rotates with the motor shaft of the steering motor 152, and the cushioning elastic element 11 deflects along with the support sleeve 153. As the cushioning elastic element 11 deflects, the angle between it and the tendon 13 gradually increases, and the tension of the tendon 13 gradually decreases. The rigidity of the variable stiffness buffer structure decreases, and the buffering performance increases, allowing it to absorb more impact force. In other words, this embodiment, through the design of the steering support component 15, increases the legged robot's ability to adapt to different terrains.

[0045] like Figure 1 , Figure 2 and Figure 3 As shown, legged robots need to adapt to environments with soft or hard surfaces, as well as flat and rugged terrain. When facing flat surfaces, the walking speed of the legged robot needs to be increased; if the robot's ankle joint has degrees of freedom, it will increase the difficulty of controlling the robot's movement. When facing more complex and rugged terrain, in order to increase the stability of the robot's movement, the walking speed of the legged robot will be reduced; if the robot's ankle joint is locked, it will reduce the legged robot's adaptability.

[0046] Therefore, the variable stiffness buffer structure described in this embodiment also includes a tensioning wheel and an ankle joint locking assembly 16 for locking the ankle joint; the tensioning wheel is installed on the robot's leg and can rotate; the ankle joint locking assembly 16 includes a locking slide 161, a pressure plate 162 and a slide locking member 163, the pressure plate 162 is placed on top of and in contact with the buffer elastic member 11, and the locking slide 161 passes through the pressure plate 162, the buffer elastic member 11 and the support sleeve 153 in sequence and can move axially. One end of the tendon 13 is connected to the lower end of the locking slide, and the other end of the tendon 13 passes around the tensioning wheel and is connected to the tendon tensioning knob 14; the slide locking member 163 is installed on the robot's leg, and the slide locking member 163 is provided with a locking brake part that cooperates with the locking slide 161. Specifically, the slide locking member 163 is provided with a locking pin, and the locking pin can be driven to extend and retract. The slide locking member 163 is preferably an electromagnetic pin lock; the lower end of the locking slide 161 has a locking hole. When the locking pin of the slide locking member 163 extends, the locking pin is inserted into the locking hole of the locking slide 161, so that the position of the locking slide 161 is locked, the tendon 13 is tensioned and held, and the variable stiffness buffer structure switches from variable stiffness mode to pure stiffness mode.

[0047] In this embodiment, when the tendon 13 pulls the locking slide column 161, the locking slide column 161 moves downward along the axis of the support sleeve 153, simultaneously causing the pressure plate 162 to move downward. The pressure plate 162 compresses the buffer elastic element 11, causing the buffer elastic element 11 to compress and absorb energy. When the road surface faced by the legged robot is flat, the slide column locking member 163 is activated, and the locking brake part of the slide column locking member 163 brakes the locking slide column 161. The locking slide column 161 is locked and cannot move, and therefore cannot continue to drive the pressure plate 162 downward to compress the buffer elastic element 11 under the pull of the tendon 13. At this time, the tendon 13 is in a tense state and remains so. The robot's foot remains stationary with the robot's leg under the tension of the tendon 13. That is to say, the ankle joint has been locked and cannot rotate. The variable stiffness buffer structure switches from variable stiffness mode to pure rigidity mode to reduce the control difficulty of the legged robot. When the legged robot faces a complex and rugged road surface, the locking brake part of the sliding column locking member 163 disengages from the locking sliding column 161, the locking sliding column 161 can move axially, and under the pull of the tendon 13, it can continue to drive the pressure plate 162 to move down to squeeze the cushioning elastic member 11, the ankle joint is unlocked, and the variable stiffness cushioning structure switches from pure rigidity to variable stiffness mode to adapt to walking on rugged roads.

[0048] Example 2:

[0049] like Figures 4 to 7As shown, this embodiment provides a biomimetic bipedal robot, including a body 2, thigh 3, lower leg 4, and foot 5 arranged sequentially from top to bottom. It also includes a hip joint drive mechanism 6, a knee joint drive mechanism 7, and a variable stiffness buffer structure 1. The body 2 and thigh 3 are connected via the hip joint drive mechanism 6, which drives the thigh 3 to perform pitch and lateral movements. The thigh 3 and lower leg 4 are movably connected via a pin, forming a knee joint at the connection point. The knee joint drive mechanism 7 connects the thigh 3 and lower leg 4 and drives the lower leg 4 to perform pitch movements around the knee joint. The lower leg 4 and foot 5 are movably connected via a pin, forming an ankle joint at the connection point, allowing the foot 5 to perform pitch movements around the ankle joint. The variable stiffness buffer structure 1 connects the leg and foot 5 to mitigate the impact and interference forces experienced by the foot 5 during movement, and also allows the foot 5 to return to its original position after pitch movements.

[0050] The hip joint drive mechanism 6 includes a motor connector 61, a lateral swing motor 62, and a hip joint pitch motor 63. The housing of the lateral swing motor 62 is mounted on the rear side of the body 2. The motor connector 61 is an L-shaped connector, with one side plate connected to the motor shaft of the lateral swing motor 62 and rotating with it. The housing of the hip joint pitch motor 63 is mounted on the other side plate of the L-shaped connector, and the hip joint pitch motor 63 is located on the outer side of the thigh 3. The motor shaft of the lateral swing motor 62 is arranged perpendicularly to the motor shaft of the hip joint pitch motor 63. The thigh 3 is connected to the motor shaft of the hip joint pitch motor 63 and rotates with it. When the motor connector 61 rotates with the motor shaft of the lateral swing motor 62, the motor connector 61 drives the hip joint pitch motor 63 and the thigh 3 to perform lateral swing motion. When the thigh 3 rotates with the motor shaft of the hip joint pitch motor 63, the thigh 3 performs pitch motion around the motor shaft of the hip joint pitch motor 63. In this embodiment, the design of the hip joint drive mechanism 6 allows the thigh 3 to have two degrees of freedom.

[0051] The knee joint drive mechanism 7 includes a knee joint pitch motor 71, a crank 72, and a multi-link assembly consisting of a first link 73, a second link 74, and a third link 75. The knee joint pitch motor 71 is installed on the inner side of the thigh 3 and is symmetrically arranged with the hip joint pitch motor 63 to ensure the symmetry of the leg structure and the balance of mass. One end of crank 72 is connected to the motor shaft of knee joint pitch motor 71 and rotates with the motor shaft. The other end of crank 72 is connected to the lower leg 4 via a multi-link assembly. Specifically, the other end of crank 72 is hinged to one end of connecting rod 1 73, the other end of connecting rod 1 73 is hinged to one end of connecting rod 2 74, the other end of connecting rod 2 74 is hinged to the top of the lower leg 4, one end of connecting rod 3 75 is connected to the connection point of connecting rod 1 73 and connecting rod 2 74 and can rotate, and the other end of connecting rod 3 75 is connected to the thigh 3 and can rotate. The design of connecting rod 3 75 makes the knee joint drive mechanism 7 have only one degree of freedom, ensuring the certainty of the lower leg's movement angle. When crank 72 rotates with the motor shaft of knee joint pitch motor 71, the torque of crank 72 is transmitted to the lower leg 4 in sequence via connecting rod 1 73 and connecting rod 2 74, so that the lower leg 4 performs pitching motion around the knee joint.

[0052] It should be noted that in this embodiment, even without drive, the crank 72 of the knee joint drive mechanism 7 can still rotate around the motor shaft of the knee joint pitch motor 71 under the action of inertial force, driving the first link 73, the second link 74, and the lower leg 4 to swing. To ensure that the legged robot can maintain an upright position without drive, this embodiment has an opening at the lower end of the thigh 3, and a limiting block 31 is provided at the opening and near the front side of the thigh 3. The upper end of the lower leg 4 is inserted into the opening of the thigh 3. When the thigh 3 and the lower leg 4 are in their extreme positions, the limiting block 31 at the lower end of the thigh 3 abuts against the front end face of the upper end of the lower leg 4, preventing the thigh 3 from tilting forward. That is to say, the maximum included angle between the thigh 3 and the lower leg 4 is close to 180°, and the thigh 3 and the lower leg 4 can achieve upright position without drive under the action of the limiting block 31. In addition, the second connecting rod 74 adopts an arc-shaped connecting rod, and the arc-shaped connecting rod bends towards the back of the thigh. The thigh 3 and the lower leg 4 can be changed from an upright state to a fully retracted leg state through the knee joint drive mechanism 7. The specific drive process is as follows: When the knee joint pitch motor 71 rotates clockwise, the crank 72 rotates clockwise with the motor shaft. The crank 72 transmits the rotational torque to the first connecting rod 73 and the second connecting rod 74 in sequence. The second connecting rod 74 generates an eccentric thrust on the lower leg 4. The lower leg 4 swings counterclockwise around the knee joint so that the thigh 3 and the lower leg 4 gradually converge until the leg forms a fully retracted form. Conversely, when the leg changes from a fully retracted position to an upright position, the knee joint pitch motor 71 rotates counterclockwise, and the crank 72 rotates counterclockwise with the motor shaft. The crank 72 transmits the rotational torque sequentially to connecting rod 1 73 and connecting rod 2 74. Connecting rod 2 74 generates an eccentric pulling force on the lower leg 4, causing the lower leg 4 to swing clockwise around the knee joint, gradually widening the gap between the thigh 3 and the lower leg 4 until the leg reaches an upright position. It should also be noted that in this embodiment, the knee joint pitch motor 71 in the knee joint drive mechanism 7 is positioned at the root of the thigh 3. Besides forming a symmetrical structure with the hip joint pitch motor 63, this also enables long-distance driving of the knee joint, increases the length of the lever arm, and reduces the output torque of the motor. It also raises the leg's center of gravity, reduces the leg's inertia, achieves a lightweight design for the leg, and greatly reduces the difficulty of controlling the leg.

[0053] The foot 5 includes a sole 51, toes 52, and a torsion spring 53. The sole 51 and toes 52 are movably connected by a pin, allowing the toes 52 to pitch around the pin. The torsion spring 53 is fitted onto the pin, with its two torsional feet abutting against the sole 51 and toes 52 respectively, to allow the toes 52 to return to their original position after pitching. When the legged robot walks on uneven surfaces, the toes 52 are compressed and rotated, deforming the torsion spring 53. When the foot 5 is lifted, the toes 52 return to their original position under the rebound force of the torsion spring 53. In this embodiment, the design of the torsion spring 53 in the foot 5 still absorbs the impact force on the foot 5, improving the impact resistance and interference resistance of the legged robot. In addition, a limiting block 54 is provided at the heel of the foot 5 to prevent the lower leg 4 from rotating backward. When a bipedal robot stands, its center of gravity is slightly backward. The bipedal robot relies on its own center of gravity to keep the lower end of the robot's lower leg 4 against the inner surface of the limiting block 54 and remain stationary, thus achieving undriven upright standing of the lower leg 4.

[0054] The following further explains the movement process of the legged robot under different road conditions, in order to further demonstrate the working principle and advantages of the present invention:

[0055] The hip joint pitch motor 63 and the knee joint pitch motor 71 are activated. The thigh 3 rotates with the motor shaft of the hip joint pitch motor 63, and the thigh 3 performs pitching motion around the motor shaft of the hip joint pitch motor 63. At the same time, the crank 72 rotates with the motor shaft of the knee joint pitch motor 71, and drives the first link 73, the second link 74, the third link 75 and the lower leg 4 to swing, and the lower leg 4 performs pitching motion. The lower leg 4 drives the foot 5 to lift and fall. The robot's foot 5 will be subjected to impact force at the moment of contact with the ground. Under this impact force, it will rotate around the ankle joint and pull the tendon 13. The buffer elastic element 11 is deformed by the stretching of the tendon 13, absorbing part of the impact force and anti-interference force, and playing a buffering role for the foot 5, ankle joint, leg and other mechanical parts, extending the service life of the legged robot and improving the stability of the robot during movement.

[0056] When the legged robot moves from a hard surface to a soft surface, the steering motor 152 is activated. The support sleeve 153 rotates with the motor shaft of the steering motor 152, and the buffer elastic element 11 deflects together with the support sleeve 153. As the buffer elastic element 11 deflects, the angle between it and the tendon 13 gradually decreases, and the tension of the tendon 13 gradually increases, so as to increase the stability of the connection between the foot 5 and the leg when the legged robot is on a soft surface.

[0057] When the legged robot moves from soft ground to hard ground, the steering motor 152 reverses, the support sleeve 153 rotates with the motor shaft of the steering motor 152, and the buffer elastic element 11 deflects together with the support sleeve 153. As the buffer elastic element 11 deflects, the angle between it and the tendon 13 gradually increases, the tension of the tendon 13 gradually decreases, the rigidity of the variable stiffness buffer structure 1 decreases, the buffering performance increases, and it can absorb more impact force.

[0058] When the legged robot faces a flat road surface, the sliding column locking component 163 is activated. The locking brake of the sliding column locking component 163 brakes the locking sliding column 161, which is locked and cannot move. Consequently, it cannot continue to drive the pressure plate 162 to move down to squeeze the buffer elastic component 11 under the pull of the tendon 13. At this time, the tendon 13 is in a tense state and remains so. The robot's foot 5 remains stationary with the robot's leg under the tension of the tendon 13. In other words, the ankle joint has been locked and cannot rotate. The variable stiffness buffer structure 1 switches from the variable stiffness mode to the pure rigid mode to reduce the control difficulty of the legged robot.

[0059] When the legged robot faces a complex and rugged road surface, the locking brake part of the sliding column locking member 163 disengages from the locking sliding column 161, the locking sliding column 161 can move axially, and under the pull of the tendon 13, it can continue to drive the pressure plate 162 to move down to squeeze the cushioning elastic member 11, the ankle joint is unlocked, and the variable stiffness buffer structure 1 switches from a pure rigid mode to a variable stiffness mode to adapt to walking on rugged roads.

[0060] This invention utilizes a variable stiffness buffer structure 1 and a torsion spring 53 in the foot 5 to absorb the impact generated between the foot 5 and the ground, thus improving the robot's stability during walking. The variable stiffness buffer structure 1 can switch between variable stiffness and pure stiffness modes, enhancing the humanoid robot's adaptability to the ground. Simultaneously, by moving the knee joint pitch motor 71 in the knee joint drive mechanism 7 upwards to the hip joint, the center of gravity of the entire leg is shifted upwards, reducing the inertia during lower limb swing and contributing to stability during walking. Furthermore, the use of a four-bar linkage as the knee joint drive mechanism 7 allows the humanoid robot to achieve a fully retracted state. Mechanical restraints at the knee and ankle joints enable the humanoid robot to stand without drive, preventing potential falls during power outages.

[0061] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A variable stiffness buffer structure, characterized in that: The system includes a cushioning elastic element and a tendon, which are located on the rear side of the leg. The cushioning elastic element is installed on the robot's leg, and the tendon connects the cushioning elastic element to the robot's foot and is tensioned. When the robot's foot contacts the ground, the robot's foot rotates around the ankle joint and pulls the tendon, causing the cushioning elastic element to deform due to the stretching of the tendon. When the robot's foot is lifted, the robot's foot returns to its original position due to the rebound of the cushioning elastic element. It also includes a steering support assembly, which is mounted on the robot's legs and can deflect, and a cushioning elastic element is mounted on the steering support assembly and can deflect with the steering support assembly; As the steering support assembly deflects, the angle between the buffer elastic element and the tendon changes, and the resultant force along the tendon direction changes, thus changing the stiffness of the variable stiffness buffer structure. The steering support assembly includes a steering motor and a support sleeve for supporting the buffer elastic element. The support sleeve is connected to the motor shaft of the steering motor and can rotate with the motor shaft. The buffer elastic element is built into the support sleeve. When the steering motor is started, the support sleeve rotates with the motor shaft of the steering motor, causing the buffer elastic element to deflect.

2. The variable stiffness buffer structure according to claim 1, characterized in that: It also includes a tensioning wheel and an ankle joint locking assembly for locking the ankle joint; the tensioning wheel is mounted on the robot's leg and is rotatable; the ankle joint locking assembly includes a locking slide, a pressure plate, and a slide lock member, the pressure plate is placed on top of and in contact with the cushioning elastic member, and the locking slide passes through the pressure plate, the cushioning elastic member, and the support sleeve in sequence and is axially movable; one end of the tendon is connected to the lower end of the locking slide, and the other end of the tendon passes around the tensioning wheel and is connected to the foot; the slide lock member is mounted on the robot's leg and has a locking brake part that cooperates with the locking slide; when the locking brake part of the slide lock member brakes the locking slide, the position of the locking slide is locked, the tendon is tensioned and held, and the position of the ankle joint is locked, so that the variable stiffness buffer structure switches from a variable stiffness mode to a pure stiffness mode.

3. The variable stiffness buffer structure according to claim 2, characterized in that: The sliding pin locking component is equipped with a locking pin, which can be driven to extend and retract. The lower end of the locking sliding pin has a locking hole. When the locking pin of the sliding pin locking component extends, the locking pin is inserted into the locking hole of the locking sliding pin, so that the locking sliding pin is locked.

4. A biomimetic bipedal robot, comprising legs and feet, wherein the legs and feet are movably connected and form an ankle joint at the connection point; characterized in that: It also includes a variable stiffness buffer structure as described in any one of claims 1 to 3; the variable stiffness buffer structure connects the leg and foot to alleviate the impact force on the foot of the legged robot during movement and increase the terrain adaptability of the bipedal robot.

5. A bionic bipedal robot according to claim 4, characterized in that: It also includes a fuselage and a hip joint drive mechanism; the hip joint drive mechanism connects the fuselage and the leg and drives the leg to perform two-degree-of-freedom motion; the hip joint drive mechanism includes a motor connector, a lateral swing motor and a hip joint pitch motor, the housing of the lateral swing motor is mounted on the fuselage, the motor connector is connected to the motor shaft of the lateral swing motor and rotates with the motor shaft, the housing of the hip joint pitch motor is mounted on the motor connector, and the leg is connected to the motor shaft of the hip joint pitch motor and rotates with the motor shaft; when the motor connector rotates with the motor shaft of the lateral swing motor, the motor connector drives the hip joint pitch motor and the leg to perform lateral swing motion; when the leg rotates with the motor shaft of the hip joint pitch motor, the leg performs pitch motion.

6. A bionic bipedal robot according to claim 4, characterized in that: The leg includes a thigh, a lower leg, and a knee joint drive mechanism. The thigh and lower leg are movably connected, forming a knee joint at the connection point. The knee joint drive mechanism connects the thigh and lower leg and drives the lower leg to perform pitching motion around the knee joint. The knee joint drive mechanism includes a knee joint pitching motor, a crank, a first connecting rod, a second connecting rod, and a third connecting rod. The knee joint pitching motor is mounted on the thigh. One end of the crank is connected to the motor shaft of the knee joint pitching motor and rotates with the motor shaft. The other end of the crank is hinged to one end of the first connecting rod, the other end of the first connecting rod is hinged to one end of the second connecting rod, the other end of the second connecting rod is hinged to the top of the lower leg, and one end of the third connecting rod is connected to the connection point of the first and second connecting rods and is rotatable. The other end of the third connecting rod is connected to the thigh and is rotatable. When the crank rotates with the motor shaft of the knee joint pitching motor, the torque of the crank is transmitted to the lower leg sequentially through the first and second connecting rods, causing the lower leg to perform pitching motion around the knee joint.

7. A bionic bipedal robot according to claim 6, characterized in that: The heel of the foot is provided with a limiting block 1 to prevent the lower leg from turning backward, and the lower end of the front of the thigh is provided with a limiting block 2 to prevent the thigh from tilting forward. When the legged robot stands, the lower end of the lower leg abuts against the limiting block 1 and can remain stationary, while the limiting block 2 on the thigh abuts against the upper end of the lower leg, and the thigh can remain upright and stationary, thus realizing the robot's driveless standing.

8. A bionic bipedal robot according to claim 4, characterized in that: The foot includes a sole, toes, and a torsion spring. The sole and toes are movably connected by a pin. The torsion spring is fitted onto the pin, and the two torsional feet of the torsion spring abut against the sole and toes, respectively.

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